Magnetism and Morphological Effects of Iron Oxide Nanoparticles in Enhancing Antibiofouling Activity of Polyphenol-Coated Surfaces

Biofouling is the process of adhesion and proliferation of biological or organic entities that may result in the formation of biofilm consisting of microbes and extracellular polymeric substances (EPS). Biofilm formation on solid surfaces significantly impacts various industries, such as desalination plants, medical devices, water pipelines, heat exchangers, and ship hulls. Microbial fouling involves the physicochemical interactions between microorganisms and solid surfaces. An electromagnetic field (EMF) may change the diffusion rates of microbial cells and the electrical double layer around the cells and contacting surfaces. In the current study, polycardanol (PC) exhibiting antibiofouling activity was modified with ferromagnetic iron oxide (IO) to investigate the EMF effects on bacterial adhesion. Two different types of IO were used to magnetize PC coatings: 1) iron oxide ionic solution (IOIS) and 2) iron oxide nanoparticles (IONPs). When there was a flow of electrolyte that contained bacterial cells across the coating slides, flow-induced EMF generated according to Faraday’s principle of induction. It was observed that the IOIS-modified surfaces, with an induced current of 44, 53, 66 nA, showed decreases in the adhesion of bacteria cells more than the unmodified (polycardanol) and IONP-modified ones. In addition to the EMF effects, the nano-scale uniform roughness of the modified surfaces appeared to play an important role in the reduction of cell adhesion. Atomic Force Microscopy (AFM) revealed that incorporating magnetic agents into PC coatings increased surface roughness. The extent of this increase depended on the concentration and size of the magnetic particles, thereby altering the antibiofouling activity. The IOIS-modified surfaces showed the needle-like spiky peaks rising around 11.8-27.5 nm while the IONP-modified ones had a smaller number of peaks, but the size of them is much larger (89.2-272.3 nm) than those in the IOIS surfaces exhibiting taller, but a lower number of peaks, with irregular spacing between the peaks. The IOIS surface displayed more regularly spaced nano-scale peaks compared to the submicron irregularly spaced spikes seen in the IONP surfaces. Both the surface roughness and the flow-induced EMF were observed to play important roles in antibiofouling activity.