Antigoni Alexandrou Ecole Polytechnique
Jinwoo Cheon Yonsei University
Hedi Mattoussi Florida State University
Vince Rotello University of Massachusetts
XX1: Design of Luminescent QDs and QD-assemblies for Targeted Use in Biology
Monday PM, November 30, 2009
Room 309 (Hynes)
9:30 AM - **XX1.1
Nanocomposite Engineering of Nanocrystalline Materials.
Jackie Ying 1 Show Abstract
1 , Institute of Bioengineering and Nanotechnology, Singapore Singapore
Nanocrystalline materials are of interest for a variety of applications. This talk describes the design and functionalization of nanocomposite materials for biological and chemical applications. Specifically, we have synthesized metallic, metal oxide and semiconducting nanocrystals for bioimaging, biolabeling, bioseparation, biosensing and catalytic applications. These nanocrystals are ≤ 10 nm in size, and are surface modified to provide for high dispersion, biocompatibility, and water solubility. They are used as building blocks to create multifunctional nanocomposite particles with unique properties.
10:00 AM - XX1.2
InAs(ZnCdS) Quantum Dots Optimized for Biological Imaging in the Near-infrared.
Peter Allen 1 , Wenhao Liu 1 , Moungi Bawendi 1 Show Abstract
1 Chemistry, MIT, Cambridge, Massachusetts, United States
We present a series of InAs(CdZnS) semiconductor nanocrystals, aka quantum dots, that are optimized for bright and stable emission in the near-infrared region (700-900nm). The synthesis and characterization of the core/shell InAs(CdZnS) quantum dots is presented. The quantum dots are then functionalized, via ligand exchange, with a variety of biocompatible ligands to enable water solubilization. Preliminary in vivo and in vitro biological imaging experiments are discussed.
10:15 AM - XX1.3
Bioactivated PEGylated Quantum Dots and Magnetic Nanoparticles: Functionalization and Interaction with Biological Systems.
Valerie Marchi-Artzner 1 Show Abstract
1 chemistry , university rennes 1, Rennes France
The inorganic core-shell semiconductor nanocrystals (QD), for example CdSe/ZnS, possess a range of tunable optical fluorescence properties whereas the surface ligand can be optimized to tailor interactions with the surroundings and control the final size of the nanocrystals. Whatever the application involving nanocrystals is, the chemical grafting of their surface has to be very well controlled. Therefore we developed two strategies to chemically functionalize the surface of the nanocrystals. The first one is based on the use of the self-assembling properties of synthetic gallate amphiphiles (Boulmedais, F. Langmuir, 2006, 22 (23), 9797) or polymer (Luccardini et al, Langmuir, 2006, 22(5), 2304). Its simple dilution into water induced the formation of well dispersed QD micelles. The second one consists in remplacing the initial ligands with short peptides having a higher affinity for the QD surface (Dif A. et al, J.A.C.S.2008, 130, (26), 8289). The use of the QD as biolabel for individual protein tracking requires the developments of simple methods to target an individual protein in a controlled manner in living cells or cellular extract. In particular the controlled stoechiometry of a stable protein-QD complex together with the preservation of the biological functionality after labelling remains unsolved. In this view, we describe here a specific targeting of proteins bearing a histamine-rich sequence with either QD micelles (Roullier, V. et al, Nanolett. 2009, 9(3), 1228-1234) or small PEGylated peptidic quantum dots (Dif, A. et al, submitted). The quantum dots possess a metal ion-chelating (multi-dentate) ligand at the surface that can bind selectively the histag proteins in vitro and in living cells (HeLa cells transfected with a histag membranar protein). The cytotoxicity of these QD micelles and Pegylated peptidic QD was studied on living cells.We describe here the properties of bioactivated nanoparticles combined magnetic and fluorescent properties within one single nanometer-sized nanoparticle used as an active label of a biological receptor. Bioactivated fluorescent magnetic micelles with a hydrodynamic diameter of around 30 nm containing both hydrophobic CdSe/ZnS quantum dots (QD) and γ-Fe2O3 nanocrystals are obtained and can be manipulated to induce a non-diffusive spatiotemporal distribution in the presence of a magnetic gradient field (Roullier, V. et al, Chem. Mat., 2008, 20, (21), 6657). Their magnetic and fluorescent properties were evaluated as dual probes for MRI and fluorescence imaging as well as their cytotoxicity in living cells.
10:30 AM - **XX1.4
The Preparation of Colloidally Stable, Water-Soluble,Biocompatible, Semiconductor Nanocrystals with a Small Hydrodynamic Diameter.
Paul Mulvaney 1 Show Abstract
1 School of Chemistry & Bio21 Institute, University of Melbourne, Parkville, Victoria, Australia
We report a simple, economical method for generating water soluble, biocompatible nanocrystals that are colloidally robust and have a small hydrodynamic diameter. The nanocrystal phase transfer technique utilizes a low molecular weight amphiphilic polymer that is formed via maleic anhydride coupling of poly(styrene-co-maleic anhydride) with either ethanolamine or Jeffamine M-1000 polyetheramine. The polymer encapsulated water soluble nanocrystals exhibit the same optical spectra as those formed initially in organic solvents, preserve photoluminescence intensities, are colloidally stable over a wide pH range (pH 3--13), have a small hydrodynamic diameter and exhibit low levels of non-specific binding to cells . Emma E. Lees, Tich-Lam Nguyen, Andrew H. A. Clayton, and Paul Mulvaney, "The Preparation of Colloidally Stable, Water-Soluble,Biocompatible, Semiconductor Nanocrystals with a Small Hydrodynamic Diameter", ACS Nano, 3, 1121-28 (2009).
11:30 AM - **XX1.5
Designing Nanocrystal Quantum Dots for Biological Imaging.
Moungi Bawendi 1 Show Abstract
1 Department of Chemistry, MIT, Cambridge, Massachusetts, United States
This talk will focus on the application of nanocrystal quantum dots in biological and biomedical imaging. We will discuss control of the hydrodynamic size, valency, and non-specific binding. We will also discuss the development of quantum dots and their ligand families that aim for minimized hydrodynamic diameter and that emit in the visible and the near IR. We will also discuss the development of “smart” quantum dot systems that are more than passive reporters of their location, but that also act as biochemical sensors of their microenvironment. For this we will focus on quantum dot pH sensing of the tumor microenvironment.
12:00 PM - XX1.6
Synthesis of Visible and Near Infrared-emitting CuInS2/ZnS QDs and Their Application for in vivo Imaging.
Thomas Pons 1 , Emilie Pic 2 , Nicolas Lequeux 3 , Elsa Cassette 1 , Lina Bezdetnaya 2 , Frederic Marchal 2 , Francois Guillemin 2 , Benoit Dubertret 1 Show Abstract
1 LPEM - UPR0005, CNRS, Paris France, 2 Centre de Recherche en Automatique de Nancy, Centre Alexis Vautrin, CNRS, Nancy France, 3 PPMD - UMR7615, CNRS-ESPCI, Nancy France
Semiconductor nanocrystals, or quantum dots (QDs), have attracted much attention over the last years due to their exceptional electronic and optical properties. They present high extinction coefficients, photoluminescence (PL) quantum yields (QY) and photostability, and their narrow emission spectra can be tuned by size and composition. They have therefore become promising alternatives to organic chromophores in many applications as light absorbers or emitters, from photovoltaics and light emitting diodes to fluorescent probes for biological imaging. In particular, QDs have the potential to significantly impact the performance of near infrared fluorescence imaging for biomedical research, diagnostics and optically assisted surgery. For example, QDs could be applied to detection of the sentinel lymph node, the status of which is a key prognostic factor for treatment of many types of cancer. Unfortunately, QD emitting in the near infrared have been so far composed of toxic compounds (Cd, Pb, Hg, Te, As…). The potential long term release of these toxic elements in the body has thus been a major obstacle to the QD clinical use, but would also represent an important hurdle for large scale optoelectronic applications.CuInS2 is an I-III-VI2 semiconductor with a direct band gap of 1.45 eV, corresponding to an 855 nm emission wavelength, and does not contain any toxic heavy metals. This material could therefore offer the opportunity to fulfil the potential of semiconductor QDs without the toxicity limitations encountered by II-VI QDs, and provide PL emission ranging from the visible to the near infrared. Here we present the synthesis of bright and photo-stable core/shell CuInS2/ZnS QDs with emission ranging from the visible to near infrared range using air-stable compounds and discuss their optical properties. We show that these QDs could be easily transferred in water using two standard solubilization techniques, ligand exchange and micelle encapsulation. We demonstrate their use for in vivo imaging and detection of regional lymph nodes in mice, and present a preliminary comparison of toxicity with Cd-based QDs. Careful toxicity studies will be required before any clinical applications, but we expect that these QDs will find many applications for in vivo biomedical imaging where toxic heavy metals cannot be tolerated.
12:15 PM - XX1.7
Quantitative Quantum Qot (QD) Methods for Tracking Stem Cells Noninvasively in vivo.
Rowena Mittal 1 2 , Marcel Bruchez 3 2 1 Show Abstract
1 Biomedical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States, 2 Molecular Biosensor & Imaging Center, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States, 3 Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania, United States
One of the most promising advances in the field of regenerative medicine has been the isolation of pluripotent stem cells, embryonic and adult, capable of differentiating into multiple tissue types. Yet a critical question remains: what is the fate of transplanted stem cells in vivo over the time of an experimental study? Presently, there are no effective noninvasive toolsets available to monitor stem cells in vivo. Due to their tunable physiochemical and fluorescent characteristics, brightness, and stability, quantum dots (QDs) have great potential for noninvasive cell tracking in regenerative medicine. However, observations of QD labeled cells have been mainly qualitative in nature, limiting our ability to determine ideal loading conditions for long-term imaging in vivo. Currently, there is no standard method for determining the number of particles taken per cell to make comparisons between experiments and literature. Without this value, optimizing a QD toolset for tracing stem cell fate will be challenging.Therefore, we developed methods utilizing commercially available materials and accessible tools to quantify QD characteristics and internalization by cells. First, we present a method using flow cytometry and calibration standards to assess the number of QDs internalized per cell. This method accounts for batch dependent differences in relative brightness of QDs. Second, we describe a biotin-4-fluorescein fluorescence plate reader assay to quantify the number of biotin binding sites per QD available per batch of streptavidin (SAv) QDs. Applying these straightforward techniques in vitro demonstrated unique uptake behavior by mouse fetal skin-derived dendritic cells (FSDCs), mouse myoblast stem cells (C2C12s), and mouse fibroblast cells (NIH3T3s) exposed to 0, 1, 4, and 8 nM loading concentrations of 705 nm polyarginine (polyarg) conjugated SAv QDs. The retention of polyarg QDs loaded at 8 nM was quantified over 5 days in all cell types. Moreover, the internalization of polyarg QDs by cells was dependent on the number of biotin binding sites available per SAv QD and conjugation reaction conditions. Lastly, initial limits of detecting QD tagged cells in our in vivo imaging system were benchmarked to establish in vivo QD loading criteria. These novel methods and quantitative results have allowed us to make comparisons of QD uptake and retention by cells with respect to cell type, QD conjugate type, QD bioactivity, and experimental conditions. This information will be invaluable for improving commercial and novel QD toolsets for cell tracking and for determining the effect of QD uptake on stem cell function and cytotoxicity – an area still under investigation. In the long term, the application of quantified methods developed here will help move cell-based therapies from the bench to the clinic.
12:30 PM - XX1.8
Tailored Quantum Dot Surface Modification for Biomedical Applications.
Joonhyuck Park 1 , Jutaek Nam 2 , Jin Ho 2 , Sungho Jung 2 , Nayoun Won 2 , Sungwook Jung 1 , Sungjee Kim 1 2 Show Abstract
1 School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, Pohang Korea (the Republic of), 2 Department of Chemistry, Pohang University of Science and Technology, Pohang Korea (the Republic of)
Bio-compatible quantum dots (QDs) can be used for a platform technology to track various biomolecules or target specific cells by their unique and advantageous optical properties. We synthesize a family of modified Dihydrolipoic acids to meet the diverse demands of QD surfaces for biological applications. The QD surfaces can be decorated by, but not limited to, carboxylic acids, various amines, sulfates, and zwitterion groups. We can provide QDs with excellent colloidal stabilities over a broad pH range in complex biological media. We can also make QD surfaces anti-fouling as minimizing the non-specific bindings. The surface engineered QDs can be used for cell trafficking, tissue imaging, and single molecule imaging of a protein on an extracellular matrix. We have investigated the endocytosis mechanisms of QDs depending on their surface properties. HeLa cells were cultured with QDs with the surfaces of carboxylic acids, tertiary amines and zwitterions. Systematic endocytosis inhibition studies were performed along with flow cytometry and confocal laser scanning microscopy. The nature of QD surface critically determines the mechanism and rate of cellular uptakes. It was revealed that carboxylic acid coated QDs internalize into HeLa cells mostly by ATP-dependent endocytosis whereas tertiary amine coated ones prefer lipid-raft-dependent macropinocytosis. We will also discuss the internalization of QDs into cytosols of prokaryotic cells by electroporation.
12:45 PM - XX1.9
Bio-imaging of Hyaluronic Acid Derivatives Using Quantum Dots.
Sei Kwang Hahn 1 , Ki Su Kim 1 , Sang Joon Park 1 , Jiseok Kim 1 Show Abstract
1 Advanced Materials Sciences and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Kyungbuk, Korea (the Republic of)
Hyaluronic acid (HA), is a biodegradable, biocompatible, non-immunogenic and non-inflammatory linear polysaccharide, which has been used for various medical applications such as arthritis treatment, ocular surgery, tissue augmentation, and so on. In this work, the effect of chemical modification of HA on its distribution throughout the body was investigated using quantum dots (QDot) for target specific and long acting drug delivery applications. According to the real time bio-imaging of HA derivatives, HA-QDot conjugates with 35 mol% HA modification maintaining enough binding sites for HA receptors were mainly accumulated in the liver, while those with 68 mol% HA modification losing much of HA characteristics were evenly distributed to the tissues in the body. The results are well matched with the fact that HA receptors are abundantly present in the liver with a high specificity to HA molecules. Based on these findings, slightly modified HA derivatives were used for target-specific intracellular delivery of siRNA and highly modified HA derivatives were used for long acting conjugation of peptide and protein therapeutics. This presentation will give you a brief overview on novel HA derivatives for various drug delivery applications.
XX2: Nanocrystal Functionalization to Promote Hydrophilicity and Biocompatibility
Monday PM, November 30, 2009
Room 309 (Hynes)
2:30 PM - **XX2.1
Nanocrystals for Biomedical Diagnosis.
Charles Cao 1 Show Abstract
1 Chemistry, University of Florida, Gainesville, Florida, United States
Because of their unique size-dependent optical, electronic, magnetic, and chemical properties, inorganic nanocrystals are becoming a new class of powerful tools in biological and medical applications for sensing, labeling, optical imaging, magnetic resonance imaging (MRI), cell separation, and treatment of disease. These applications, however, require nanocrystals that are soluble and stable in aqueous solutions, and thus creating a need to further engineer nanocrystal coatings, because those high-quality nanocrystals are often synthesized in organic phase and stabilized with hydrophobic ligands. To date, two major approaches have been developed to modify the coatings of hydrophobic nanocrystals using organic ligands. The first approach is based on coordinate bonding. Functional groups (such as thiol, dithiol, phosphine and dopamine) are used to directly link hydrophilic groups onto the surface of hydrophobic nanocrystals by replacing their original hydrophobic ligands. The second approach uses hydrophobic van der Waals interactions, through which the hydrophobic tails of amphiphilic ligands interact with (but do not replace) the hydrophobic ligands on nanocrystals, and it leads to the formation of nanocrystal-micelles. Many types of water-soluble nanocrystals made by these two approaches suffer low stability and/or high non-specific binding with non-target biomolecules. Water-soluble nanocrystals coated with PEGylated amphiphilic polymers are proven to have very high stability and low nonspecific-absorption levels, but PEGylated polymer shells often produce large hydrodynamic diameters (HDs) on the order of 30-40 nm, which could limit the use of these nanocrystals in applications such as in vivo cell imaging. Herein, we report an alternative nanocrystal-surface-engineering approach that uses a new class of ligands (here called dual-interaction ligands) to produce water-soluble nanocrystals of gold, Fe3O4, CdSe/ZnS quantum dots (QDs) and Mn-Doped QDs. These dual-interaction ligands can bind onto the surface of hydrophobic nanocrystals through both coordinate bonding and hydrophobic van der Waals interactions. The resulting water-soluble nanocrystals have relatively small HDs (e.g., less than 20 nm), and exhibit extraordinary stability in a wide range of pH (e.g., 1-14), salt concentrations, and thermal treatment (at 100 oC). We have demonstrated the use of these nanocrystals for monitoring virus expression in cells as well as for detecting protein of interest in blood samples.
3:00 PM - XX2.2
Dual-Water-Phase Reverse Micelle Method to Prepare Silica Beads with Separately Impregnated Highly Photoluminescent and Magnetic Nanocrystals.
Norio Murase 1 , Ping Yang 1 , Masanori Ando 1 Show Abstract
1 Photonics Research Institute, National Institute of Advanced Industrial Science & Technology, Ikeda, Osaka563-8577, Japan
Sol-gel-derived silica beads encapsulating highly luminescent semiconductor nanocrystals (NCs) can additionally host other materials, such as magnetic NCs, in a specially prepared hollow sphere within the beads, resulting in dual functionality. Several sol-gel approaches have been used to synthesize magnetic-luminescent silica beads. However, the direct attachment of magnetic nanocrystals (MNCs) and luminescent nanocrystals (LNCs) reduces photoluminescence (PL) efficiency. We have prepared luminescent silica beads by using a reverse micelle method, in which water droplets formed in a continuous oil phase. Water-soluble CdTe NCs disperse in the water droplets. Alkoxide molecules, such as tetraethoxysilane (TEOS), initially disperse in the oil phase gradually enter the water phase as they becomes more and more hydrophilic accompanied by hydrolysis. After the hydrolyzed TEOS condenses in the water droplets, silica beads with impregrated LNCs are synthesized. A newly developed modified version of this reverse micelle method presents silica beads with impregnated LNCs with high PL efficiency and MNCs. In this version, two water phases are used. The first is the same as described above: aqueous solution of LNCs and hydrolyzed TEOS. The second phase is dispersion of MNCs under high pH (~10) conditions. Following the formation of droplets by the first water phase and subsequent hydrolysis of TEOS in the droplet, the second water phase goes in to the water droplets. This creates a hollow space inside of each droplet because the interface in a droplet quickly forms a wall of silica by condensation of alkoxide due to the high pH of the second water phase. This creates silica beads (100–200 nm in diameter) with dispersed LNCs in the continuous silica phase and MNCs in the hollow part of each bead. Since the two types of NCs are separated, their specific properties are not degraded by the preparation. The result is highly photoluminescent and magnetic beads. The initial PL efficiency (68%) of the LNCs was maintained with saturated magnetization of 3 emu/g; the decrease from the initial value (45 emu/g) is explained by the reduced weight ratio in the silica beads. The brightness of these beads makes them well suited for biological tagging and collection. The characteristics of the prepared beads were clarified by TEM, ADF, and chemical analysis together with XRD.
3:15 PM - XX2.3
Mediating Cellular Uptake and Endosomal Escape of Quantum Dots using Modular Designer Peptides.
Kelly Boeneman 1 , James Delehanty 1 , Bing Mei 2 , Juan Blanco-Canosa 3 , Phillip Dawson 3 , Hedi Mattoussi 2 , Igor Medintz 1 Show Abstract
1 Center for Biomolecular Science and Engineering, Naval Research Laboratory, Washington, District of Columbia, United States, 2 Division of Optical Sciences, Naval Research Laboratory, Washington DC, District of Columbia, United States, 3 Departments of Cell Biology and Chemistry, Scripps Research Institute, La Jolla, California, United States
To realize the full potential of luminescent semiconductor quantum dots (QDs) as intracellular labeling reagents and sensors, robust methods for their targeted intracellular delivery must be developed. We have previously shown that QDs self-assembled with a histidine-appended polyarginine ‘Tat’ cell-penetrating peptide (CPP) could be specifically delivered in a non-toxic manner to HEK293T/17 and COS-1 cells via endocytic uptake . We have further assessed the long-term intracellular stability and fate of these QD-peptide conjugates and found that they remained sequestered within the acidic endolysosomes for at least three days after initial uptake; the CPP remained stably associated with the QD throughout this time. This appears to corroborate other findings that, regardless of the size or nature of the ligand used to facilitate endocytic uptake, almost all QD-conjugates subsequently remain in this vesicular system and do not access the cytosol . To address this limitation, we explored a variety of techniques to either actively deliver QDs directly to the cytosol or facilitate their endosomal escape into the cytosol. Active methods such as electroporation and nucleofection delivered only modest amounts of QDs to the cytosol that appeared to be aggregated. Delivery using polymeric transfection reagents resulted in primarily endosomal sequestration of QDs, although in one case a commercial reagent did facilitate a modest cytosolic dispersal of the nanocrystals, but only after several days of culture and with a significant amount of polymer-induced cytotoxicity. In comparison, a modular, amphiphilic peptide expressing a variety of overlapping functionalities and designed for cell penetration and vesicular membrane interactions was found to mediate rapid QD uptake followed by a slower endosomal release of the QD-conjugates which peaked at 48 hours after initial delivery. Importantly, this QD-peptide bioconjugate elicited minimal cytotoxicity in the cell lines tested. We have also utilized various modifications of this peptide sequence expressing specifically deleted residues to identify the critical functional attributes which provide it with both cellular uptake and endosomal escape capabilities. We will present these results and discuss how a better understanding of these processes can allow cellular delivery of QD-conjugates capable of targeted in vivo sensing applications. 1.Delehanty, J.B., et al., Self-assembled quantum dot-peptide bioconjugates for selective intracellular delivery. Bioconj. Chem., 2006, 17:920-927.2.Delehanty, J.B., et al., Delivering quantum dots into cells: strategies, progress and remaining issues. Anal. Bioanal. Chem., 2009, 39:1091-1105.
3:30 PM - XX2.4
Synthesis and Cytotoxicity Evaluation of Highly Luminescent, Water-Soluble InP and ZnS-Coated InP Quantum Dots.
Yuxuan Wang 1 , Chai Hoon Quek 2 , Kam Leong 3 , Jiye Fang 4 1 Show Abstract
1 Materials Sci. & Eng., State University of New York at Binghamton, Binghamton, New York, United States, 2 Mechanical Eng. & Materials Sci., Duke University, Durham, North Carolina, United States, 3 Biomedical Eng., Duke University, Durham, North Carolina, United States, 4 Chemistry, State University of New York at Binghamton, Binghamton, New York, United States
Semiconductor quantum dots (QDs) are gaining much attention as a new class of luminescence probes for biological detection and labeling. For in vivo imaging, the QD should ideally emit at the near IR range to minimize background interference. However, the frequently used CdSe-based QDs often exhibit properties too close to the optimal biological window of transmission. Hypothesizing that InP-based QDs would overcome this disadvantage, we synthesized InP and ZnS-coated InP QDs using a high-temperature organic solvent approach, and subsequently transfer them into aqueous phase through a ligand-exchange process using various functional surfactants including Trichloro-s-triazine modified mPEG. Structural characterizations and luminescence examination of these water-soluble QDs revealed an average size of ~3-4 nm and a high quantum yield. The cytotoxicity of the as-synthesized QDs against phaeochromocytoma PC12 cells and primary hepatocytes as evaluated by the MTS cell viability assay was low relative to other inorganic QDs. This study suggests a bright potential for this new type of InP/ZnS-coated InP QDs in bioimaging.
3:45 PM - XX2.5
Toward Development of High-quality Water-soluble PbS Quantum Dots.
Haiguang Zhao 1 , Mohamed Chaker 1 , Dongling Ma 1 Show Abstract
1 , INRS, Varennes, Quebec, Canada
Near infrared (NIR) quantum dots (QDs) have attracted much attention due to their unique size-tunable optical properties. They are currently exploited for various applications, such as optoelectronics and biological markers. Among them, the use of NIR QDs for in vivo deep-tissue imaging is particularly attractive in view of the improved tissue penetration of lights and decreased tissue autofluorescence. However, it is still a challenge to synthesize bright, highly stable and biocompatible NIR emitting QDs. Recently, we have synthesized high-quality PbS QDs via a simple, solventless, greener approach which can be dispersed very well in the organic phase. In order to make them suitable for biomedical applications, various amphiphilic molecules have been used as phase transferring agents. Through detailed investigation, it is found that the quantum yield and lifetime of transferred PbS QDs are very sensitive to the initial surface ligand structure and the structure of amphiphilic molecules. Under certain circumstances, significant structure deterioration after the phase transfer results in the complete loss of the photoluminescence of PbS QDs. By forming a compact, protective surface layer, the structural integrity has been maintained and the quantum efficiency as high as that of the initial PbS QDs in the organic phase has been achieved in the aqueous phase.
4:30 PM - **XX2.6
Hydrophilic Polymer Ligands for Semiconductor Quantum Dots.
Francisco Raymo 1 Show Abstract
1 Chemistry, University of Miami, Coral Gables, Florida, United States
The outstanding photophysical properties of semiconductor quantum dots suggest that these inorganic nanoparticles can become valuable alternatives to conventional organic dyes in a diversity of bioimaging applications. These nanostructured assemblies, however, are not soluble in aqueous environments in their native form and must be passivated with hydrophilic coatings to ensure biocompatibility. In particular, their native hydrophobic surfactants can be replaced with hydrophilic thiols or coated with amphiphylic polymers to impose aqueous solubility. Nonetheless, the first strategy produces nanoparticles with poor quantum yields and limited stabilities, while the second approach increases significantly their physical dimensions. In order to overcome these limitations, we designed a series of ligands incorporating multiple thiol groups and poly(ethylene glycol) chains along a common polymer backbone. These macromolecular constructs adsorb on the surface of preformed CdSe/ZnS core-shell quantum dots to produce hydrophilic nanoparticles with compact dimensions, excellent quantum yields and long-term stabilities. Furthermore, these luminescent probes can cross cell membranes and are not cytotoxic. Thus, our novel polymer ligands can eventually lead to the development of valuable biocompatible quantum dots for the convenient investigation of cellular processes and visualization of subcellular structures.
5:00 PM - XX2.7
Aniline-Catalyzed Hydrazone Ligation: An Alternative Chemistry for the Multivalent Display of Biomolecules on Quantum Dot Surfaces.
Duane Prasuhn 1 , Juan Blanco-Canosa 3 , Kimihiro Susumu 2 , Gary Vora 1 , James Delehanty 1 , Hedi Mattoussi 2 , Philip Dawson 3 , Igor Medintz 1 Show Abstract
1 Center of Bio/Molecular Science & Engineering - Code 6910, US Naval Research Laboratory, Washington, District of Columbia, United States, 3 Department of Cell Biology and Chemistry, Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, United States, 2 Division of Optical Sciences - Code 5611, US Naval Research Laboratory, Washington, District of Columbia, United States
With their unique photoluminescent properties, semiconductor quantum dots (QDs) are promising nanoparticle-based scaffolds for biosensing and biomedical applications. One of the principle hurdles for the wider incorporation of QDs in biology continues to be the lack of facile linkage chemistries that allow the multivalent display of biomolecules such as proteins, peptides, and DNA on the QD surface in a controlled manner. Current methodologies are based on a limited set of functional groups and allow only minor control over the number and spatial orientation of the attached biomolecules. Aniline-catalyzed hydrazone coupling which has recently been demonstrated for modifying peptides and proteins may be a viable alternative for attaching biomolecules onto QD surfaces. This arises from the inherent regio-selectivity of the chemical ligation chemistry itself. Further, high reaction rates that approach >90% completion in less than one day using equimolar reactant concentrations can be carried out in mild, aqueous conditions of slightly acidic to neutral pH. We have tested two versions of this chemical approach. In the first, a polyhistidine ‘starter’ peptide is ligated to the targeted peptide or DNA of interest and facilitates subsequent self-assembly to the QD surface. The modularity of this approach was demonstrated by utilizing the final QD conjugates in sensing, cellular delivery, and DNA hybridization assays. It was also used to investigate resonance energy transfer in QD-assemblies with complex architectures. Examples of each will be discussed along with their utility. The second approach to this chemistry ligates targeted peptides or DNA directly to modified capping ligands already present on the QD surface. This methodology may be a viable approach for the controlled engineering of not only hybrid QD-biological systems, but is applicable to other types of nanoparticle materials.
5:15 PM - XX2.8
Study of Diamond photoluminescent Nanoparticles Uptake Mechanism in Cultured Cells.
Orestis Faklaris 1 , Vandana Joshi 2 , Abdallah Slablab 1 , Yan-Kai Tzeng 3 , Geraldine Dantelle 1 , Hugues Girard 4 , Celine Gesset 4 , Jean-Paul Boudou 2 , Mohamed Sennour 5 , Alain Thorel 5 , Jean-Charles Arnault 4 , Patrick Curmi 2 , Francois Treussart 1 Show Abstract
1 Laboratoire de Photonique Quantique et Moléculaire, Ecole Normale Supérieure de Cachan, CNRS UMR 8537, Cachan France, 2 Laboratoire Structure et Activité des Biomolécules Normales et Pathologiques, Université d’Evry-Val-d’Essonne, INSERM U829, Evry France, 3 Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei Taiwan, 4 Diamond Sensor Laboratory, CEA LIST, Gif-sur-Yvette France, 5 Laboratoire Pierre-Marie Fourt, CNRS UMR 7633, Centre des Matériaux de l’Ecole des Mines de Paris, Evry France
Single molecule observation is of great importance to study biomolecules interactions. Organic dyes are widely used as biomarkers but lack of photostability. One of the most used alternative system are the semiconductor Quantum Dots (QDs). Although very efficient for multicolour staining, they suffer of blinking and may be cytotoxic. In contrast, diamond nanoparticles containing nitrogen-vacancy (NV) color centers are a promising alternative. NV-centers neither photobleach nor blink and nanodiamonds are biocompatible. Here we investigate the uptake mechanisms of 35 nm photoluminescent nanodiamonds (PNDs) at the single particle level in culture cells. Moreover, we study and compare the photophysical properties of single PNDs and QDs.Nanodiamonds are made photoluminescent by particle beam irradiation creating vacancies and subsequent annealing. HeLa cells were grown in standard conditions and mounted on microscope slides or prepared for TEM observations. For endosomal and lysosomal labeling fluorescein was used. Colocalization was examined by either a home-made confocal microscope with single-photon detectors or with a SPC2 Leica microscope. Endocytosis was blocked by incubating cells at 4°C or by drug treatment. For single particle observations, the nanoparticles were spin-coated on glass coverslips.By endosomal and lysosomal staining and by hindering endocytosis uptake with drugs we find that PNDs are internalized by receptor-mediated endocytosis. With colocalization analysis we find a perfect colocalization of PNDs-aggregates in endosomal or lysosomal vesicles while for single PNDs the colocalization is partial. We verify these results by HR-TEM measurements. Moreover, we show that a single NV-center is 3-4 times less bright than a single QD, but that optimization of PNDs preparation leads to 20 nm PNDs containing up to 6-7 NV-centers, that are brighter than a single QD at the end.To summarize, we determined the internalization mechanism of PNDs. Thanks to their higher brightness and photostability compared to other biomarkers, PNDs are promising intracellular markers, which could also serve as drug delivery devices.
5:30 PM - XX2.9
Conjugating Luminescent CdTe Quantum Dots with Biomolecules.
Christina Gerhards 1 , Christian Schulz-Drost 1 , Vito Sgobba 1 , Dirk Guldi 1 Show Abstract
1 Department of Chemistry and Pharmacy , Friedrich-Alexander University Erlangen-Nuernberg, Erlangen Germany
The interest in semiconductor quantum dots (QD) has been continuously increasing during the last two decades. As the physical and chemical properties of semiconductor QDs differ greatly from those of their corresponding bulk materials numerous applications have emerged (i.e. photodiodes/solar cells, phototransistors, integrated optical circuit elements, lasers). [1, 2] Furthermore QDs have unique optical properties such as high emission quantum yields, broad absorption and narrow, symmetric photoluminescence, high molar extinction coefficients, remarkable resistance to chemical- and photodegradation as well as to photobleaching.  Considering, for example, the emission features, a key asset is that they span the full visible region of the solar spectrum as a result of tunable band gaps together with a very broad excitation wavelength range. Important is in this context that traditional markers based, for example, on organic molecules fall short of providing long-term stability and simultaneous detection of multiple signals. Biological labeling by conjugation of inorganic nanostructures with biomolecules represents a significant milestone. These inorganic nanostructure / biomolecule conjugates combine the properties of both materials, namely exhibiting the spectroscopic characteristics of the QDs, while preserving the function of the biomolecules.  I will present interactions between water soluble, luminescent CdTe QDs and different redoxactive proteins (i.e., cytochrome c).  Characterization spans from simple UV-Vis absorption assays to transient absorption, steady-state and time-resolved photoluminescence spectroscopy as well as HR-TEM.References: D. V. Talapin, S. Haubold, A. L. Rogach, A.Kornowski, M.Haase, H. J. Weller, Phys. Chem. B 2001, 105, 2260.  M.Gao, S. Kirstein, H. Mohwald, A. L. Rogach, A.Kornowski, A. Eychmueller, H. Weller, J. Phys. Chem. B 1998, 102, 8360.  B. Dubertret, P. Skourides, D. J. Norris, V. Noireaux, A. H. Brivanlou, A. Libchaber, Science 2002, 298, 1759. W. C. W. Chan, D. J. Maxwell, X. Gao, R. E. Bailey, M. Han, S. Nie, Curr. Opin. Biotechnol. 2002, 13, 40. I. L Medinitz,. H. T. Uyeda, E. R. Goldmann, H. Mattoussi, Nature Mat. 2005, 4, 435.  C. Gerhards, C. Schulz-Drost, V. Sgobba, D. M. Guldi, Phys. Chem. B 2008, 112, 14482.
5:45 PM - XX2.10
Chiral Quantum Dots.
Yurii Gun ko 1 Show Abstract
1 Chemistry, Trinity College Dublin, Dublin Ireland
Quantum dots (QDs) are fluorescent semiconductor (e.g. II-VI) nanocrystals, which have a strong characteristic spectral emission. This emission is tunable to a desired energy by selecting variable particle size, size distribution and composition of the nanocrystals. QDs have recently attracted enormous interest due to their unique photophysical properties and range of potential applications in photonics and biochemistry.The main aim of our work is develop new materials based chiral quantum dots (QDs) and establish fundamental principles influencing the structure and properties of chiral QDs. Here we present the synthesis and characterisation of various chiral II-VI (CdS, CdSe and CdTe) semiconductor nanoparticles. The most interesting are penicillamine stabilised CdS and CdSe nanoparticles, which have shown both very strong and very broad luminescence spectra. Circular dichroism (CD) spectroscopy studies have revealed that the D- and L- penicillamine stabilised CdS and CdSe QDs demonstrate circular dichroism and possess almost identical mirror images of CD signals [1, 2]. Studies of photoluminescence and CD spectra have shown that there is a clear relationship between defect emission and CD activity. We believe that these new QDs could find important applications as fluorescent assays and sensors (or probes) in asymmetric synthesis, catalysis, enantioseparation, biochemical analysis and medical diagnostics. Also chiral QDs with an appropriate functionality could potentially serve as materials for the fabrication of circularly polarised light emitting devices. These devices are necessary components of chiroptical detectors used in polarimetry and CD spectrometers. Finally, circular polarized light emitters might have a potential application in colour displays.References1. M. M. Moloney, Y. K. Gun’ko, J. M. Kelly, Chem.Comm. 2007, 3900 – 3902.2. S. D. Elliott, M. P. Moloney and Y. K. Gun’ko, Nano lett , 2008, 8(8), 2452-2457.
XX3: Poster Session
Tuesday AM, December 01, 2009
Exhibit Hall D (Hynes)
9:00 PM - XX3.1
Non-blinking and Non-bleaching Upconverting Nanoparticles as Optical Imaging Nanoprobe and T1 MRI Contrast Agent.
Yong Il Park 1 , Taeghwan Hyeon 1 Show Abstract
1 School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of)
Nanoparticles have been extensively studied for their unique size-dependent electronic, optical, and magnetic properties and their potential applications as probes in biomedical imaging. Recently, various multimodal imaging probes have been fabricated by combining different functional nanoparticles for more accurate imaging and diagnosis. For example, the combination of fluorescent semiconductor quantum dots and superparamagnetic magnetite nanoparticles yielded bimodal imaging probes that can provide the high sensitivity and resolution of fluorescence imaging as well as non-invasive and real-time monitoring abilities of magnetic resonance imaging (MRI). We demonstrated that NaGdF4:Er3+,Yb3+/NaGdF4 upconverting nanoparticles (UCNPs) can serve as multimodal imaging probe not only for background-free optical imaging but also for MRI. UCNPs absorb near-infrared (NIR) photons and emit visible or near UV photons. Non-blinking and non-bleaching property of UCNPs is unraveled by combined wide-field epi-luminescence imaging and atomic force microscopy analysis. The sturdy and persistent luminescence of UCNPs will minimize possible artifacts related to photoblinking and photobleaching of fluorescent probes in long-term imaging experiments. Bright-field and luminescence images of cancer cells incubated with UCNPs show complete absence of autofluorescence with NIR excitation at 980 nm and detection at 400-700 nm. Owing to Gd3+ ions on the surface, imaging contrast is clearly enhanced by UCNPs in T1-weighted MRI. Our UCNPs, endowed with multimodality, are expected to contribute to unerring diagnosis in biomedical applications.
9:00 PM - XX3.10
Luminescent Silicon Nanoparticles as Possible Agents for Bio-Imaging.
Nathalie Herlin Boime 1 , Ilaria Rivolta 4 , Rosaria D'Amato 2 , Vincent Maurice 1 , Valentina Bello 3 , Mauro Falconieri 2 , Giovanni Mattei 3 , Giulio Sancini 4 , Yarue Nie 5 , Olivier Sublemontier 1 , Enrico Trave 3 , Dayang Wang 5 , Giuseppe Miserocchi 4 , Elisabetta Borsella 2 Show Abstract
1 IRAMIS/SPAM, CEA, Gif/Yvette Cedex France, 4 environmental medicine and biotechnology, Univ Milano-Bicocca, Milano Italy, 2 FIM, ENEA, Rome Italy, 3 Physics, Univ Padova, Padova Italy, 5 colloids and interface, MPI of colloids and interfaces, Potsdam Germany
Visible light emission from silicon nanoscaled structures has motivated an intense research for 15 years. Nevertheless, significant quantities of such particles could not be supplied in order to develop silicon nanocrystals-based applications which are now emerging. For labelling applications, organic dye based fluorophores are most often used. However, these dyes have several drawbacks such as rapid photo-oxidation, limited lifetime, need of different wavelengths to activate each dye... More recently, semiconductor nanocrystals (quantum dots-QDs) have been introduced for bio-labelling. As a result of the quantum confinement, such NPs (nanoparticles) exhibit intense, size-tuneable emission in the visible and near-infrared optical range. One main advantage of using luminescent NPs for imaging rests on their photostability, increased sensitivity through longer life time, and excitability by a single wavelength, which makes semiconductor NPs glow in a rainbow of colours depending on their size. However, as most widely used QDs (II-VI semiconductor QDs) are highly cytotoxic, limitations occur for in vivo application in living organisms and Si QD can offer a valuable alternative studied in the frame of the Bonsai euro project. Using the laser pyrolysis method, we are now able to obtain silicon nanocrystals with sizes between 4 and 9 nm and with a production rate between 0.2 g/h and 1 g/h respectively. The powders exhibit an intense photoluminescence (PL) after some days of passivation under ambient atmosphere or soft oxidation treatments in liquids and PL remains stable for months. The PL emission of Si NPs falls in the range 600-1000 nm and typical radiative lifetimes are in the range 0.05-0.3 ms. Using two-photon excitation we were able to excite Si NPs in the IR (at about 900 nm) where the human skin transmittivity is high. In order to use these NP for bio-labelling, the elaboration of stable and biocompatible colloids of Si NPs is necessary. The stability of NP Si suspensions in aqueous media was greatly improved by coating a silica shell at the surface of the NP and grafting with functional silanes terminated with amine or epoxy groups, for example efficiency of APTS grafting was measured in the range 6-10 functions per Si NP. NP were conjugated with poly(ethyleneglycol) and negligible cytotoxicity of PEGylated Si NPs was observed by vitality tests on epithelial cell lines known to be fairly sensible to noxious agents, i.e. A30 cells (located at the air/blood barrier). At first sight it was also found that cell proliferation is differently affected by S-PEGylated and E-PEGylated Si NPs (strongly in the first case, mildly in the second). First images of cells labelled with Si NP could also be obtained. Detailed results concerning these different points (passivation, surface functionnalization, toxicity and imaging) will be shown and discussed.
9:00 PM - XX3.11
Nontoxic Silicon Nanocrystals and Nanodiamonds as Substitution of Harmful Quantum Dots.
Anna Fucikova 1 2 , Jan Valenta 1 , Ivan Pelant 2 , Vitezslav Brezina 3 Show Abstract
1 Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University in Prague, Prague Czechia, 2 , Institute of Physics AS CR, v. v .i., Prague Czechia, 3 , Institute of Systems Biology and Ecology AS CR, v. v .i.,, Nove Hrady Czechia
Commercially available semiconductor quantum dots (CQD) (e.g. cadmium containing quantum dots like CdS, CdSe, CdTe etc.) are toxic according to recent publications. They cannot be used in long-term biological studies in vitro and there is no safe method how to remove them after application in vivo. We are developing new non-toxic nanocrystalline silicon (Si-NCs) fluorescence labels which are biodegradable in living body and fluorescent nanodiamonds which are long-term stable (mainly for in vitro use). Light-emitting silicon nanocrystals (Si-NCs) have a crystalline core with size between 1-5 nm and their surface is naturally covered by SiO2 or functionalized by various compounds with respect to desirable use. Photoluminescence (PL) emission bands of Si-NCs range from ultraviolet to near infrared spectral region, depending on the Si-NC size and surface passivation. We present mesurements of luminescence spectra of single nanocrystals at room temperature in various environments including animal cells. There is a slight shift of the PL emission in the spectra when Si-NCs are interacting with internal environment of cells. Nanodiamond (ND) particles with diameter of 10 nm emit in the visible part of the spectrum with PL peak between 600-800 nm. Their cytotoxicity was studied in culture of L929 mouse fibroblast and HeLa cells. The bio-interaction of nanoparticles is studied by optical transmission microscopy, time-lapse microphotography of cell culture evolution, fluorescence microscopy, fluorescence micro-spectroscopy, confocal microscopy and scanning electron microscopy. The size and shape of nanocrystals were determined using atomic force microscopy and dynamic light scattering.
9:00 PM - XX3.12
Quantum Dots Delivery into Living Cells and High Resolution 3D Microscopy.
Alexandra Fragola 1 , Eleonora Muro 1 , Roli Richa 1 , Pierre Vermeulen 1 , Pedro Felipe Gardeazabal 1 , Pierre Blandin 1 , Eduardo Sepulveda 1 , Ivan Maksimovic 1 , Vincent Loriette 1 , Benoit Dubertret 1 Show Abstract
1 , LPEM, Paris France
Quantum dots (QD) present several advantages for high resolution 3D fluorescence imaging of biological samples:-they allow simultaneous multicolor imaging-thanks to a great absorption cross section, a high quantum yield, a recently reduced blinking and a good resistance to photobleaching, QDs become promising probes for single molecule imaging during a long time observation-they can be functionalized for specific targeting.Nevertheless, quantum dots delivery into living cells remains a critical step for many biological applications. We will show how pinocitosys allow to introduce into the cytoplasm QD at high concentration that are still bright and diffuse freely, even several days after.We will also present the development of a new method for quantum dot delivery based on pseudo-virus production as QD cargos. Those pseudo-viruses are 120nm particles with an envelope allowing fusion with target cells ; therefore, main applications could be specific staining, for cancer cells for example, or QD delivery in weak cells (neurons or stem cells).To observe cells stained with QD, we developed a structured illumination microscope that can perform both fast optical sectioning or super resolution imaging. The principle consists in collecting high spatial frequencies of the sample through the optical transfer function of the microscope using moiré effect. Based on Gustafsson's set-up (J. Microsc. 2000), our microscope uses two interfering beams to introduce a spatial modulated intensity pattern in the focal plane, which is displaced laterally with no mechanical elements, using a second spatial light modulator. An enhancement of the lateral resolution by a factor of two can then be achieved and allows super-resolution fluorescence imaging of multicolor QD-labeled cells for co-localization applications.This versatile set-up also permits fast acquisition of classical wide field and structured illuminated fluorescence images in order to obtain an optical section of the sample with only two images. This recent technique, called HiLo microscopy (J. Mertz, JBO 2009), allows 3D observation of QD-labeled biomolecules with good lateral and axial resolutions and increased temporal resolution.
9:00 PM - XX3.14
Synthesis of Multifunctional Monodisperse MnO Nanocrystals as Potential Hybrid Materials for Biomedical Applications.
Thomas Schladt 1 , Kerstin Schneider 1 , Tanja Graf 1 , Wolfgang Tremel 1 Show Abstract
1 Institute for Inorganic and Analytical Chemistry, Johannes Gutenberg University Mainz, Mainz, RLP, Germany
Magnetic nanoparticles of 3d transition metal oxides have gained enormous interest as new materials for biomedical applications such as magnetic separation, sensing, and as contrast agents for magnetic resonance imaging (MRI). Although scalable preparative routes to high-quality magnetic nanoparticles are well-established, synthetic routes for surface modification are far less developed, which limits the utility of nanoparticles in biological applications. Two common problems are confronted when applying these particles in vivo: their destabilization due to the absorption of plasma proteins and non-specific uptake by reticular-endothelial system (RES), like macrophage cells. Poly(ethylene glycol) (PEG) and PEGylated materials are well-known for their biocompatibility, thus PEGylation of colloidal nanoparticle surfaces has been shown to reduce cytotoxicity and nonspecific protein binding.In this contribution we present single crystalline, highly monodisperse MnO nanoparticles of various sizes which were synthesized by decomposition of a manganese oleate complex in high boiling non-polar solvents. Transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) confirmed phase purity and homogeneity of the particles. Magnetic measurements showed that the magnetic properties strongly depend upon the size of the nanoparticles. Both magnetic moment and blocking temperature increase when the particle size is decreased.The as-prepared MnO nanocrystals were modified by ligand exchange of the oleate groups by novel multifunctional PEGylated polymers. These polymers allow further functionalization of the nanoparticles, e.g. cell-specific biomolecules. The coated MnO nanocrystals are extremely stable in various aqueous media (e.g. PBS-buffer, human blood serum), exhibit no cytotoxicity, and high T1 relaxivity coefficients. Therefore, our multifunctional MnO nanoparticles demonstrate a strong potential for a variety of bioapplications such optical/magnetic resonance imaging and specific cell targeting.References Katz, E.; Willner, I. Angew. Chem., Int. Ed. 2004, 43, 6042.  Xu, C.; Xu, K.; Gu, H.; Zhong, X.; Guo, Z.; Zheng, R.; Zhang, X.; Xu, B. J. Am. Chem. Soc. 2004, 126, 3392. Zhao, M.; Josephson, L.; Tang, Y.; Weissleder, R. Angew. Chem., Int. Ed. 2003, 42, 1375. Park, J.; Joo, J.; Kwon,S.G.; Jang, Y.; Hyeon, T.; Angew. Chem. Int. Ed. 2007, 46, 4630. (a) Q. A. Pankhurst, J. Connolly, S. K. Jones, J. Dobson, J. Phys. D Appl. Phys. 2003, 36, R167. (b) C. C. Berry, A. S. G. Curtis, J. Phys. D, Appl. Phys. 2003, 36, R198. (c) S. M. Moghimi, A. C. Hunter, J. C. Murray, Pharm. Rev. 2001, 53, 283. (a) Harris M. J., Zalipsky, S., Eds. Poly(ethylene glycol): Chemistry and Biological Applications; American Chemical Society: Washington, DC, 1997. (b) Kohler, N.; Fryxell, G.; Zhang, M. J. Am. Chem. Soc. 2004, 126, 7206. Schladt, T. D.; Graf, T.; Tremel, W.; Chem. Mater. 2009, in press.
9:00 PM - XX3.15
Nanocomposites of Highly Luminescent CdTe Quantum Dots with Nanoporous Gold.
Minho Kim 1 , Sunghoon Kim 2 , Jaebeom Lee 2 , Dongyun Lee 1 Show Abstract
1 Nanomaterials Engineering, Pusan National University, Busan Korea (the Republic of), 2 Nanomedical Engineering, Pusan National University, Busan Korea (the Republic of)
Semiconductor nanocrystals (NCs), also known as quantum dots (QDs) are very attractive materials because of their many desirable properties, such as a wide absorption band, strong emission, possibility for controlling band gap, and their durability when exposed to light irradiation. Nanoscaled gold is also well known for enhancing the surface sensitivity of spectroscopic measurements. In this study, attempts to combine these two materials to synthesize nanocomposites have been performed. We used gold as nanoporous form on glass substrate that is fabricated from gold-silver alloy thin film by dealloying process using chemical or electrochemical technique. We prepared various sizes of the CdTe QDs and different pore sizes of the nanoporous gold films. And then, the CdTe QDs are embedded into the nanoporous gold films by electrophoretic or dip coating method. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM) are used to explore microstructures of the nanocomposites, and Raman spectroscopy and photoluminescence (PL) are employed to analyze optical properties of the nanocomposites. Implications for the applications of the nanocomposite are discussed.
9:00 PM - XX3.16
High-Resolution Long-Range Scanning Magnetic Imaging of Nanoparticles.
Li Yao 1 , Shoujun Xu 1 Show Abstract
1 Department of Chemistry, University of Houston, Houston, Texas, United States
Magnetic nanoparticles are widely used as biochemical markers, drug delivery carriers, and imaging contrast agents. Precise determination of the position and amount of the particles at a given time is vital for these purposes. In many applications, such as assay analysis on microchips and in vivo imaging, one characteristic is that the magnetic particles being used are far away from the detectors, on the order of several millimeters to a few centimeters. This makes it challenging to obtain a high sensitivity and sufficient spatial information because of the r^-3 dependence of magnetic field strength. Here we show a scanning magnetic imaging technique that possesses both a large detection range and high spatial resolution. This technique couples a novel scanning imaging scheme with a sensitive atomic magnetometer, which operates at a low temperature of 37 oC. We achieved a spatial resolution of 20 micrometers with a detection distance of nearly one centimeter, while only using ~30 nl of magnetic particles. The absolute magnetization and hence the amount of the particles is simultaneously determined. Such a combination enables imaging of magnetic nanoparticles in various situations where a large separation between the magnetic sample and the detector is inevitable. Our technique thus fills the gap between microscopic magnetic imaging and long-distance magnetic sensing. It will be applicable for scenarios that are not easily achievable before. Of particular interest are microfluidic applications of magnetic nanoparticles. We will be able to distinguish in which channel the magnetic particles flow and at what time and flow rate. The magnetization of the particles will reveal the amount of labeled chemical of interest, which serves as an indicator of the degree of the biomedical interaction has proceeded. We expect the resolution and detection limit be further improved based on projection from the intrinsic sensitivity of our atomic magnetometer.
9:00 PM - XX3.2
Quantum Dot Conjugation to Aptamers for Biological Probes using Cu(I)-catalyzed Azide-alkyne Cycloaddition.
Sungwook Jung 1 , Hyungu Kang 2 , Joonhyuck Park 1 , Jutaek Nam 3 , Nayoun Won 3 , Ho Jin 3 , Sungho Jung 3 , Sungjee Kim 1 3 Show Abstract
1 School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, Pohang Korea (the Republic of), 2 Aptamer Unit, Postech Biotech Center, Pohang University of Science and Technology, Pohang Korea (the Republic of), 3 Department of Chemistry, Pohang University of Science and Technology, Pohang Korea (the Republic of)
Semiconductor quantum dots (QDs) are promising fluorescent probes for cellular imaging. On the other hand, aptamers can be easily synthesized by systematic evolution of ligands by exponential enrichment, and can show bindings to a broad range of targets with extremely high affinity and specificity. CdSe/CdS/ZnS (core/shell/shell) QDs were used as they can retain high fluorescence quantum yields in biological media. We have conjugated QDs to single stranded RNA aptamers that have been screened for human epidermal growth factor receptors 2 (HER2) which are known to be overexpressed in 15-20 percent of breast cancer cells. Cu(I)-catalyzed azide-alkyne cycloaddition, ‘click’ reaction, was employed for the conjugation. This approach provided us with robust QD-aptamer conjugate probes. The conjugate size was characterized by the dynamic light scattering and electrophoresis studies. The QD conjugates were used for cellular imaging with HER2-overexpressing human breast cancer cell line SKBr3. As controls, Hela and MCF7 cell lines were used as they have negligible or moderate expression level of HER2. Interactions of the QD conjugates with various types of cells were investigated using confocal laser scanning microscopy and fluorescence-activated cell sorting analysis. We will discuss applications of the QD conjugates for long-term single molecule imaging such as cell membrane protein trafficking.
9:00 PM - XX3.3
In vivo Real-time Multiplexed Infrared Quantum Dot Imaging Toward Tumor Growth and Development Studies.
Nayoun Won 1 , Joonhyuck Park 2 , Sanghwa Jeong 1 , Jiwon Bang 1 , Sungjee Kim 1 2 Show Abstract
1 Chemistry, Pohang University of Science and Technology, Pohang Korea (the Republic of), 2 School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology, Pohang Korea (the Republic of)
Infrared (IR) quantum dots (QDs) can promise a new modality for in vivo bio-imaging and future medical imaging applications. QDs have proven the potential for imaging contrast agents by the bright luminescence, resistance against photobleaching, and the multiplexing capability. IR wavelengths can provide maximal tissue penetrations by the minimal interferences from water and biomolecules and the reduced auto-fluorescence. IR QDs are used for in vivo imaging of tumor growth and development in a mouse model. We xenograft cancer cells that are labeled by IR QD internalization, and observe the growth and development of tumor by home-built IR imaging setup. Penetration depth of the QD imaging is simulated by optical phantom experiments using biological tissues such as bovine liver and porcine skin. We investigate into the imaging parameters that affect contrasts and signal to noise ratios. We report changes in penetration depths by the incidence angle, polarization, and excitation and emission wavelengths. We will also discuss camera specificities between Si and InGaAs CCDs for the in vivo imaging applications.
9:00 PM - XX3.4
Monofunctional Quantum Dot Probes for Cell Imaging and Nano-Architecture.
Samuel Clarke 1 , F. Pinaud 1 , A. Sittner 1 , G. Gouzer 1 , O. Beutel 2 , J. Piehler 2 , M. Dahan 1 Show Abstract
1 Physics and Biology, ENS Paris, Paris France, 2 Biology, Universitat Osnabruck, Osnabruck Germany
Recently, it has been shown that the optical properties of quantum dot (QD) nanoparticles enable novel experiments at the single-molecule level in live cells, thereby opening new prospects for the understanding of cellular processes. One difficulty with these experiments is that complex biological environments impose stringent design requirements on fluorescent probes, necessitating the development of smaller and more biocompatible QDs. In this work, we present our efforts towards minimizing the size and controlling the surface functionality of QDs. We show that an engineered peptide surface coating and a purification method based on gel electrophoresis are sufficient to produce compact monofunctional QDs covalently conjugated to streptavidin, biotin or antibodies. To further characterize these QD probes, we apply techniques such as HPLC, ultracentrifugation and live cell assays. Aside from applications in biological imaging, we demonstrate the utility of monofunctional QDs to form controlled assemblies of nanoparticles, such as dimers and higher-order structures, which are confirmed by electron and single-molecule spectroscopy.
9:00 PM - XX3.5
In vivo NIR Up-conversion Luminescent Bioimaging Using Lanthanide Doped Nanocrystals and their Surface Modification.
Sanghwa Jeong 1 , Nayoun Won 1 , Sungjee Kim 1 2 Show Abstract
1 Chemistry, POSTECH, Pohang Korea (the Republic of), 2 School of Interdisciplinary Bioscience and Bioengineering, POSTECH, Pohang Korea (the Republic of)
Lanthanide doped nanocrystals (LDNCs) have attracted much attention for a decade owing to their advantageous features for bio-imaging such as strong chemical stability, low toxicity, narrow emission profile, and robustness against photobleaching. Especially, LDNCs that can be excited by near-infrared (NIR) are optimal for in vivo imaging probes. They can promise deep tissue penetrations, minimal auto-fluorescence, and reduced light scattering. Monodisperse NaYF4:Yb3+,Tm3+ up-conversion luminescent LDNCs have been successfully synthesized in fatty acid condition. The LDNCs are spherical with a mean diameter of 30 nm, and are dispersed in aqueous media through ligand exchanging by amines with long alkyl chains. The surface modified LDNCs show outstanding colloidal stability under a wide pH range from 2 to 8. The LDNCs show bright blue up-conversion luminescence in aqueous media under the illumination at 980 nm. They are further used for in vivo imaging studies on small animal models as exploiting the deep penetration depth, high signal-to-noise, and low toxicity.
9:00 PM - XX3.6
Quantum Dot Micelle Conjugates.
Olivier Carion 1 , Emilie Genin 2 , Benoit Mahler 1 , Eric Larquet 3 , Eric Doris 2 , Benoit Dubertret 1 Show Abstract
1 LPEM, ESPCI, Paris France, 2 iBiTecS, CEA, Gif sur Yvette France, 3 IMPMC, UMR 7590, Paris France
Colloidal nanocrystal quantum dots (QDs) consist of an inorganic nanoparticle core surrounded by a layer of organic ligands. Since their discovery, intensive studies have been carried out suggesting great potential for applications in electronic material science and more recently in biology. Indeed, the development of sensitive and specific probes that circumvent the intrinsic limitations of fluorogenic organic dyes is of considerable interest in many fields of research from molecular and cellular biology to medical imaging and diagnosis. Semiconductor nanocrystals have thus received considerable attention thanks to their unique optical properties which include high quantum yield, large molar extinction coefficient, tunable fluorescence emission, and photostability. Hydrophilic QDs have already been conjugated to biomolecules such as peptides, antibodies, nucleic acids, or small ligands for applications as targeted fluorescent labels. Applications of QDs in biology are increasingly widespread, giving a new impetus to this nano-material. Control over the photophysical and chemical properties of QDs require an extensive understanding of these properties, of their advantages and limitations. This knowledge allows the optimization of the coating and material composition to obtain the most reliable and reproducible results during biological experiments. The preparation of controlled and stable hydrophilic QDs is still a major challenge. This first step determines bioconjugate formation, controls the size, the robustness and quantum efficiency of the future biological probe. Here we will present the preparation and characterization of functionalized phospholipid QD micelles. These self-assembled probes consist in hydrophobic QDs incorporated into amphiphilic phospholipid micelles. The hydrophobic chains interdigitate with the QD hydrophobic ligands and the hydrophilic part of the lipid ensures water solubility. We will show details about quantum dot micelles characterization and procedures for obtaining stable conjugated QDs in aqueous buffers. We will present techniques for QD purification, encapsulation, and their effect on the QD optical properties. We will detail the preparation of Quantum dots bioconjugated with various biomolecules, such as proteins, DNA, antibodies. For the first time to our knowledge, we will present a full characterization of QD micelles in aqueous medium using cryogenic electron microscopy. We will also present QDs conjugated with CrAsH, a bisarsenical affinity probe. These organic dyes have s