Preparation of gold nanoparticles by a novel biodegradable graft copolymer sodium alginate-g-poly (N,N-dimethylacrylamide-co-acrylic acid) with anti micro bacterial application

[Display omitted] •Synthesis and characterization of a biodegradable graft copolymer based on sodium alginate and a mixture of DMA and AA.•Biodegradation studies and determination of COOH groups into the synthesized graft copolymer.•Preparation of gold nanoparticles (GgNPs) by using the graft copolymer without addition of any reducing agent.•The prepared GgNPs are rice shaped under optimum condition.•The synthesized (rice shaped) GgNPs show an excellent antibacterial activity onto gram positive and gram negative bacteria. Sodium alginate-g-poly-(N,N-dimethylacrylamide-co-acrylic acid) was prepared in presence of potassium peroxydisulfate (K2S2O8) as the initiator by solution polymerization technique. The so prepare graft copolymer was characterized by different characterization techniques like determination of molecular weight by SEC, FTIR, 1H NMR and 13C NMR spectroscopy, XRD-studies. Biodegradation of the graft copolymer was analyzed by enzymatic cleavage. The graft copolymer was used to synthesize gold nanoparticles from chloroauric acid tetra hydrate (HAuCl4, 4H2O) without addition of any reducing agent. The gold nanoparticles were characterized by UV–VIS spectroscopy, Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive X-ray Analysis (EDAX). The effects of various synthetic parameters such as polymer and chloroauric acid (HAuCl4, 4H2O) concentration, pH, reaction time and temperature were studied for finding optimum condition. It was shown that the synthesized nanoparticles were rice shaped. One type of synthesized gold nanoparticles, under optimized condition was used for antimicrobial activity against both gram-negative and gram-positive bacteria by agar well diffusion method. The gold nanoparticles prepared under optimum condition exhibits excellent anti bacterial sensitivity to one gram negative bacteria Vibrio parahaemolyticus (ATCC-17802) and one gram positive bacteria Bacillus subtilis (ATCC-11774).