Synthesis and characterization of quaternized carboxymethyl chitosan/poly(amidoamine) dendrimer core–shell nanoparticles

With the aim to develop a novel water-soluble modified chitosan nanoparticle with tuned size and improved antibacterial activity, quaternized carboxymethyl chitosan/poly(amidoamine) dendrimers (CM-HTCC/PAMAM) were synthesized. Firstly low-generation amino-terminated poly(amidoamine) (PAMAM) dendrimers were prepared via repetitive reactions between Michael addition and amidation, which were then employed for modifying quaternized carboxymethyl chitosan (CM-HTCC). Prior to the reaction of CM-HTCC with PAMAM, carboxylic groups in CM-HTCC were activated with EDC/NHS in order to enhance the reaction efficiency. FT-IR, 1H NMR, elemental analysis and XRD were performed to characterize CM-HTCC/PAMAM dendrimers. Turbidity measurements showed that CM-HTCC/PAMAM dendrimers had good water-solubility. TEM images indicated that CM-HTCC/PAMAM dendrimers existed as smooth and spherical nanoparticles in aqueous solution. The results of antibacterial activity explored that CM-HTCC/PAMAM dendrimer nanoparticles displayed higher antibacterial activity against Gram-negative bacteria Escherichia coli (E. coli), whereas they showed much less efficiency against Gram-positive bacteria Staphylococcus aureus (S. aureus) compared to quaternized chitosan (HTCC).