Anti-Bacterial Properties of Boron Cross-linked Chitosan/Poly (Vinyl Alcohol) Hydrogels Containing Zinc Oxide Nanoparticles

Chitosan is a hydrophilic and versatile polysaccharide possessing functional groups such as carbonyl and amine groups which are areas for antimicrobial activity. PVA has high degree of swelling in aqueous solutions and mostly blended with chitosan because of its good tensile strength and elastic nature. Six chitosan- PVA hydrogel samples were prepared by varying the amounts of chitosan and PVA, blending them with equal amounts of boric acid ( cross-linker), soaking them in sodium hydroxide overnight, washed several times with distilled water, freeze- thawed at -200 for 6hrs and + 370 for 2hrs respectively for 5 cycles, then dried in an oven and later analyzed. During the hydrogel preparations, the first three samples were blended without zinc oxide nanoparticles and the last three with equal amounts of zinc oxide nanoparticles. Swelling percentages of samples 1- 3 were evaluated in 2 ways: (1) soaking a known amount of each dried sample in distilled water while varying time. (2) soaking another known amount of dried samples in different pH buffer solutions for 24hrs. Its kinetics showed that: as the pH increases, their swelling % increases and starts dropping as the pH gets more basic and that the higher the amount of PVA in a sample, the higher its swelling % in water with increased time. The bacterial analysis of the samples were carried out in order to determine the effect of an increased amount of chitosan and of zinc oxide nanoparticles on bacterial growth. The LB agar medium was used for the culturing of the E.coli bacteria which is a gram negative bacteria possessing a thinner peptidoglycan membrane. The sample with the highest amount of Chitosan showed more inhibition than the others and the addition of nanoparticles to this sample showed an even more greater inhibition towards the bacteria. Finally the Scanning electron microscopy (SEM) and FTIR of the prepared hydrogels were done inorder to determine the surface structures of the hydrogels and the various functional groups present in each hydrogel respectively. Keywords : Chitosan-PVA hydrogel, Zinc oxide nanoparticles, Boric acid cross linker, Antibacterial properties, Swelling properties.