Binding Polymer Particles With Encapsulated Antibacterial Compounds to Thin-Film Composite Membranes for Enhanced Biofouling Resistance

Biofouling continues to be a major challenge for membrane processes.  Several methods have been proposed to curtail biofouling, including membrane surface modification with hydrophilic and antimicrobial polymers and nanomaterials.  Although many of these modifications rely on compounds that leach from the membrane surface, they do not always leach in a controllable way.  Here, we borrow technology used for drug delivery – controlled release – and apply it to the membrane biofouling problem.  We have encapsulated two antimicrobial compounds, kanamycin and cinnamaldehyde, in biodegradable poly(lactic-co-glycolic acid), PLGA, particles. These particles can be covalently bound to the polyamide membrane surface, targeting biofouling where it is most problematic. 

In this proof-of-concept study, 200 nm diameter PLGA particles were fabricated using spontaneous emulsion diffusion.  The outer surface of the PLGA particles was doped with poly(ethylene-alt-maleic acid), which contains carboxyl groups that can be covalently bound to the carboxyl groups present on the polyamide surface.  Successful binding was confirmed with a scanning electron microscopy, and modified membrane surface properties were assessed with contact angle goniometry.  The effect of surface modification on membrane transport properties was tested using a bench top reverse osmosis system.

Although particles could potentially be loaded with a variety of chemicals, we investigated loading with kanamycin and cinnamaldehyde.  Thus, we demonstrated the encapsulation of both hydrophilic and hydrophobic active compounds.  Kanamycin is a hydrophilic aminoglycoside antibiotic.  It was encapsulated using a water-oil-water emulsion.  Cinnamaldehyde is a hydrophobic extract of cinnamon that exhibits both antimicrobial and anti-quorum sensing activity.  Particles containing cinnamaldehyde were fabricated using spontaneous emulsion diffusion.  The loaded compounds were released from the particles over a matter of days, and particles inhibited bacterial growth in solution.  Biofilm formation on modified membranes was assessed using Escherichia colias a model organism, and significant reductions in biofilm formation were observed.

Using this platform, a variety of different antimicrobial compounds could potentially be used to prevent biofouling.  Additionally, this flexible platform offers the possibility of stimuli-response particles that release active compounds under specific conditions.  Therefore, particles can be customized to meet the challenges of particular feed waters.