Synthesis of cationic hyperbranched polyamidoamine dendrimer and comparison of its antimicrobal activity with chitosan

Abstract

The cationic hyperbranched dendritic polyamidoamine (PAMAM) containing terminal methyl ester end groups was synthesized and employed for modifying bulk chitosan. This modifying agent was synthesized using the repetitive reactions between Michael addition and amidation to obtain the methyl ester group terminated hyperbranched PAMAM and then followed by the methylaton of methyl ester terminated hyperbranched dendritic PAMAM (PAMAM-ester) with dimethyl sulphate. Hyperbranched dendrtic PAMAM and cationic hyperbranched dendritic PAMAM were characterized by FTIR and H NMR analysis to confirm these structures. The modification of chitosan with catonic hyperbranched PAMAM-ester was carried-out through the reaction of the polyamidoamine methyl ester end group and the chitosan amine group at room temperature for 5 days. The amide linkage was formed and evidenced by FTIR analysis. Chitosan modfied with excess amount of catonic hyperbranched PAMAM-ester was water soluble at neutral pH. TGA and XRD analyses provided evidence that the catonic hyperbranched PAMAM-chitosan containing a bulky side group exhibited enhanced chain mobility, resultng n increasing water solubility. Pure chitosan and cationic hyperbranched dendritic PAMAM-chitosan films showed excellent antimicrobial activity. However, coating of bulk chitosan and in-situ depolymerization of coated chitosan show that chitosan-fabrics showed negative antimicrobial result. On other hand, cotton fabrics treated with cationic hyperbranched dendritic PAMAM have good ability to inhibit the microbial growth. Combined treatment of cotton fabric with chitosan and cationic hyperbranched dendritic PAMAM indicated that cationic hyperbranched dendritic PAMAM moiety played a synergistic effect on antimicrobial activity due to its cationic characterstic.