Novel aminohydrazide cross-linked chitosan filled with multi-walled carbon nanotubes as antimicrobial agents

Four chemically modified chitosan derivatives (1) under bar-(4) under bar were designed and synthesized via a series of four reactions; first by reaction with benzaldehyde to protect its amino groups (Derivative (1) under bar), second by reaction with epichlorohydrine (Derivative (2) under bar), third by reaction with aminobenzhydrazide (Derivative (3) under bar), and forth by removing of benzaldehyde to restore the free amino groups on the chitosan (Derivative (4) under bar). Two multi-walled carbon nanotube (MWCNT) biocomposites based on Derivative (4) under bar were also prepared. The structure of the prepared derivatives and MWCNT composites was elucidated using elemental analyses, MR, XRD, SEM and TEM. The modified chitosan derivatives and MWCNT composites showed better antimicrobial activities than that of chitosan against Enterococcus faecalis, Staphylococcus epidermidis, Escherichia coli, Aspergillus niger, Cryptococcus neoformans and Candida tropicalis as judged by their higher inhibition zone diameters using the agar well diffusion technique. These derivatives and MWCNT composites are more potent against Gram-positive bacteria than against Gram-negative bacteria. The MWCNT composites displayed comparable or even better antimicrobial activities than the reference bactericides or fungicides. Thus, structural modification of chitosan through combination with functionalized moieties and MWCNTs in one system was taken as a way to achieve promising templates for antimicrobial agents and to be appropriate candidates for medical applications. (C) 2018 Elsevier B.V. All rights reserved.