Antibacterial response of polylactide surfaces modified with hydrophilic polymer brushes

Ultrathin polymeric films may completely change in their surface properties from bacteria loving to bacteria repelling which are essential for creating non-fouling surfaces. The covalent modifications of biodegradable polylactide (PLA) surface with alkyl bromide initiator followed by immobilization of three different types of polymers having potential antibacterial effects, i.e., poly(2-hydroxyethyl methacrylate) (PHEMA), Poly(2-[(methacryloyloxy)ethyl]trimethylammonium chloride) (PMETA) and poly(poly(ethylene glycol) methacrylate) (PPEGMA) were successfully conducted using surface-initiated atom transfer radical polymerization (ATRP) technique. High initiator density (1.72 initiator/nm2) on PLA surface determined by XPS led to the formation of smooth polymer brush as shown by AFM images which were further characterized by FTIR and contact angle measurement. Though linear brush growth was observed irrespective of monomers employed, ‘grafting yield’ was found to be highest for PHEMA brush (22.2 µg cm−2 at 6 h) under similar conditions indicating its high activity in the presence of efficient catalytic system. Finally, the antibacterial response of these brushes was evaluated against both gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria and PMETA modified PLA surface was found to exhibit the highest inhibition of bacterial adhesion (> 97% for S. aureus). The novelty lies in the generation of polymer brushes with excellent antibacterial property onto biodegradable polylactide surface. The potential uses of these modified surfaces would include biomedical devices, food packaging, etc.