Effect of pendant group functionality on the biological activity of quaternized Poly(4-vinylpyridine) copolymers

Cationic polymers are remarkable materials effectively used in a wide range of biomedical applications such as drug delivery, tissue engineering and gene delivery. It is well established that the functional groups within polymer structures exert a profound influence on their biological activities. Elucidating the specific effects of these functional groups on the biological properties of polymers is paramount, as it will facilitate the development and application of novel polymeric materials across a diverse range of biomedical fields. Here, the antibacterial activity, cytotoxicity and gene transfection efficiency of the cationic copolymer of quaternized 4-vinylpyridine (Q4VP) and oligo(ethylene glycol) methyl ether methacrylate (OEGMA₅₀₀) which has distinct functionalities (hydrophobic, hydrophilic, zwitterionic) as pendant groups were investigated in vitro. The functional groups of alkyl, alkenyl, quaternary ammonium, hydroxyl, carboxylic acid, phenyl and ester were included into the structure of the copolymer as the pendant groups by quaternization. The degrees of quaternization ranged from 35-43 %, and zeta potentials of the copolymers were measured between +19.2 and +28.2 mV. In antibacterial activity test evaluated by broth microdilution method, MIC values were found to be between 4–16 μg/mL against Escherichia coli (E. coli) and 2–32 μg/mL against Staphylococcus aureus (S. aureus). In vitro cytotoxicity test on the L929 cell line, using the MTT method, revealed inhibition concentration values (IC₅₀) ranging from 192.3 to 972.6 μg/mL for the quaternized copolymers. Moreover, the transfection efficiency of polyelectrolyte complexes formed by the quaternized copolymer with plasmid DNA encoding green fluorescent protein (GFP) were systematically examined in HEK293T cells. The study revealed that, contingent upon the functionality of the pendant groups, a peak transfection efficiency exceeding 90 % was attained. The results clearly demonstrate the direct impact of the pendant group functionality on the biological activity of the cationic copolymer.