Green synthesis of chitosan-cinnamaldehyde cross-linked nanoparticles: Characterization and antibacterial activity

Traditional method of chitosan (naturally available abundant biopolymer) nanoparticles synthesis is the ionic cross-linking between chitosan and say, sodium tri-polyphosphate (TPP). These nanoparticles are structurally less stable and are basically obtained viaconversion of chitosan, a pure bio-based material, into a hybrid structure of biopolymer and a synthetic chemical. The present work reports a novel attempt to synthesize antimicrobial chitosan nanoparticles by chemical cross-linking with cinnamaldehyde, another eco-friendly bactericidal agent. The synthesized nanoparticles (size range, 80-150 nm) were analysed for their surface morphology. X-ray diffraction pattern denoted the amorphous characteristics of the formed nanoparticles. The FTIR analysis revealed formulation of chitosan nanoparticles to be based on Schiff reaction between amino group of chitosan and aldehyde group of cinnamaldehyde. NMR analysis also confirmed the formulation of cinnamaldehyde cross-linked chitosan nanoparticles. TGA and DSC were performed to analyse thermal characteristics and stability of prepared nanoparticles. Subsequently, the study successfully indicated that the synthesized nanoparticles exhibit synergistic antibacterial activity (98%) against Staphylococcus aureus (Gram-positive) and (96%) Escherichia coli (Gram-negative) bacteria. The MIC and MBC values were found to be 5 mg/mL and 10 mg/mL, respectively, for both types of bacteria.