Hybrid materials based on chitosan functionalized with green synthesized copper nanoparticles: Physico-chemical and antimicrobial analysis

Recently, the development of materials with antimicrobial properties has become a challenge under scrutiny. The incorporation of copper nanoparticles (NpCu) into a chitosan matrix appears to represent a viable strategy to contain the particles and prevent their oxidation. Regarding the physical properties, the nanocomposite films (CHCu) showed a decrease in the elongation at break (5 %) and an increase in the tensile strength of 10 % concerning chitosan films (control). They also showed solubility values lower than 5 % while the swelling diminished by 50 %, on average. The dynamical mechanical analysis (DMA) of nanocomposites revealed two thermal events located at 113 degrees and 178 degrees C, which matched the glass transitions of the CH-enriched phase and nanoparticles-enriched phase, respectively. In addition, the thermogravimetric analysis (TGA) detected a greater stability of the nanocomposites. Chitosan films and the NpCu-loaded nanocomposites demonstrated excellent antibacterial capacity against Gram-negative and Gram-positive bacteria, proved through diffusion disc, zeta potential, and ATR-FTIR techniques. Additionally, the penetration of individual NpCu particles into bacterial cells and the leakage of cell content were verified by TEM. The mechanism of the antibacterial activity of the nanocomposites involved the interaction of chitosan with the bacterial outer membrane or cell wall and the diffusion of the NpCu through the cells. These materials could be applied in diverse fields of biology, medicine, or food packaging.

Automated summary

Recently, the development of antimicrobial materials has been a focus of attention. Incorporating copper nanoparticles (NpCu) into a chitosan matrix is a viable strategy to prevent their oxidation. The nanocomposite films (CHCu) showed improved tensile strength, decreased elongation at break, lower solubility, and reduced swelling compared to chitosan films (control). These nanocomposites also exhibited excellent antibacterial capacity against both Gram-negative and Gram-positive bacteria, and the antibacterial mechanism involved the interaction of chitosan with bacterial membranes and the diffusion of NpCu into the cells. These materials have potential applications in various fields including biology, medicine, and food packaging.