Galactopolymer architectures/functionalized graphene oxide nanocomposites for antimicrobial applications

Methacryl-2,3,4,6-tetra- O -acetyl-D-galactopyranoside (MG) based linear (PMG-L), 3-armed (PMG-3A) and 4-armed (PMG-4A) galactopolymer architectures were produced by ATRP copper complexed process and the obtained polymer architectures were characterized by FT-IR and 1 H- & 13 C-NMR spectroscopic techniques. The weight percentages of pendant protected galactose moieties of the galactomacromolecular chains were in the range of 74.3-77.9 % and the molecular weights of the galactopolymers were in the orbit of 10595-13211 as calculated from 1 H-NMR spectra. Further, graphene oxide (GO) was functionalized with 2-thiopheneethylamine (GO-T) and RGD peptide (GO-P) and their nanocomposites were prepared with the synthesized PMG-L, PMG-3A, and PMG-4A galactopolymers by solvent assisted–mixing method. The 4-armed nanocomposites exhibited 5-12 °C higher thermal stability compared to the neat galactopolymers. DSC studies of the neat galactopolymers and nanocomposites revealed that the PMG-3A nanocomposites with 1 wt% GO and modified GO showed higher glass transition temperature values (98-129 °C) compared to their neat galactopolymer (92 °C). FE-SEM analysis of nanocomposites revealed the dependence of polymer architecture and GO surface functionalities on the surface morphologies. The 4-armed polymer composites having 1 wt% of GO-P and GO-T showed the formation of relatively uniform spherical 150-200 nm nanoparticles. Antibacterial activities of the PMG-L, PMG-3A, and PMG-4A nanocomposites were evaluated against E. coli and compared with their neat galactopolymer architectures. The PMG-3A and PMG-4A galactopolymer nanocomposites exhibited considerably prominent zone of inhibition in contrast to the linear polymer, PMG-L nanocomposites and their neat galactopolymers. Graphical abstract