Solvent-Responsive Macroporous Polymer Gel Possessing Inherent Antimicrobial Activity Based on Quaternized 2-(Methyl(pyridine-4-yl)amino)ethyl Methacrylate

Macroporous polymeric gels functionalized with quaternized 2-(methyl(pyridine-4-yl) amino)ethyl methacrylate, possessing hydrocarbon chain lengths ranging from butyl to dodecyl, have been fabricated (labeled as DGC4, DGC6, DC8, and DGC12). The prepared gels were characterized using13C solid-state NMR, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy (FESEM), and optical and swelling studies. Interestingly, it was observed that these polymer gels show responsive behavior in ethanol and water, which was further studied qualitatively as well as quantitatively. Further, the solvent-responsive behavior of these gels was found to be influenced by the alkyl chain length. Polymeric gels containing octyl chains displayed the highest responsiveness to ethanol and water. Furthermore, the antimicrobial activity of the gels was determined for Gram-negative bacteria (Escherichia coli) as well as Gram-positive bacteria (Staphylococcus aureus). It was observed that the antimicrobial activity displayed by the polymer gels was dependent on the alkyl chain length of the quaternized functionality. Results revealed that upon increasing the alkyl chain length from butyl to dodecyl, the antimicrobial performance of the polymeric gels improved. The gels labeled as DGC4, DGC6, DGC8, and DGC12 exhibited reduction of 98.97%, 99.62%, 99.96%, and 100% against Staphylococcus aureus and 99.53%, 99.82%, 100%, and 100% against Escherichia coli, respectively. The biocompatibility of the polymer gels designated as DGC8 and DGC12 was assessed by using cell viability experiments with an MTT assay.