Modification of chitosan and chitosan nanoparticle by long chain pyridinium compounds: Synthesis, characterization, antibacterial, and antioxidant activities

[Display omitted] •The long chain pyridinium salts were grafted on the chitosan and chitosan nanoparticle.•The QAC-chitosan derivatives were evaluated for antibacterial and antioxidant activities.•They showed significant effect against Gram-positive bacteria and a mild activity against DPPH radicals. Chitosan is an antibacterial biopolymer and conjugation of it with other antimicrobial agents can be a valuable method to improve the potential application of the resultant materials in the various industries such as cosmetics, food and packaging materials. In this work, a series of quaternary pyridinium compounds were synthesized; then to achieve developed biological properties, they were attached to the chitosan and chitosan nanoparticles. The formation of chitosan derivatives was evinced by FT-IR, 1H and 13C NMR, UV–vis and EDX spectroscopy. The morphology of samples was detected by FE-SEM, TEM and AFM images. The QAC-chitosan hybrids were investigated for antibacterial activity against two Gram-positive and two Gram-negative bacteria, and they showed a significant effect on the Gram-positive bacteria. DPPH-radical scavenging assay shows mild improvement in antioxidant activity of new chitosan derivatives.