Antimicrobial Surface Coatings on Reverse Osmosis Membranes for Biofouling Inhibition

The adhesion of bacteria to surfaces leads to irreversible formation of biofilm, which is a major challenge in both medical and technological applications. Particularly, reverse osmosis (RO) membranes for seawater desalination suffer from biofilm formation, which results in a reduction of membrane performance. Since biofilms are less susceptible to antibiotics and disinfection agents, a potential solution to prolong the lifetime of the RO membrane. By modify its surface in a way that reduces bacterial attachment through optimization of the surface physicochemical properties and include an antimicrobial component, which would slow biofilm growth of attached bacteria. Antimicrobial peptides (AMPs) are well known for their broad antimicrobial activity and their ability to overcome biofilm formation on surfaces. Thus we aimed to change the surface properties such as the charge using graft polymerization, and increase the antimicrobial activity of the surface using AMPs.

In this study, the AMP magainin-2 was immobilized to RO membranes grafted with polymeric coatings with different charge properties. Initially, the membrane surfaces were grafted with different monomers which were then functionalized with azide. Second, the peptides were attached to the grafted surfaces by using the copper-catalyzed azide-alkyne cycloaddition reaction (click reaction). XPS analysis confirmed both polymer grafting and peptide presence on the surface. The resulting RO showed reduced contact angles, which is advantageous for reducing bacterial adherence. Membranes grafted with magainin-2 showed bacterial killing activity towards Pseudomonas aeruginosa as measured in flow cell conditions. It is pertinent to note that membranes that were coated directly with magainin-2 showed also effective inhibition of P. aeruginosa biofilm, up to 80% reduction in biovolume compared to an unmodified membrane. Understanding how AMP surface activity is affected by grafted polymer compositions on membranes and hence will aid in the design and development of reverse osmosis membranes that are highly antimicrobial and biofilm resistant.