A novel hybrid β-chitin/calcium phosphate functionalized with copper nanoparticles for antibacterial applications

Abstract

In the present work, a newly synthesized hybrid β-chitin/dicalcium phosphate anhydrous (DCPA) loaded with copper nanoparticles Cu(NPs) was investigated as an antibacterial agent using various strains. The hybrid β-chitin/DCPA was obtained via a mechano-chemical route and the Cu(NPs) supported over β-chitin/DCPA matrix was successfully synthesized from Cu(II) ions using the ultrasound-assisted method followed by in situ chemical reduction with sodium borohydride. All the prepared materials were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–vis diffuse reflectance spectroscopy (DRS), simultaneous thermogravimetry/differential thermal analysis (TG/DTA), and scanning electron microscopy (SEM-EDS). The localized surface plasmon resonance (LSPR) of Cu(NPs) after the reduction process was identified by the optical absorption spectroscopy, in the visible light region around 600 nm. The antibacterial activity of Cu-based materials was investigated against series of Gram-positive bacteria (S. aureus, L. monocytogenes) and Gram-negative (E. coli, P. aeruginosa) strains, using the microtitration assay by determining the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). Among the materials tested, Cu(NPs)/β-chitin/DCPA exhibited a high antibacterial effect exceeding CuII-β-chitin/DCPA and many others reported antibacterial agents, with a MIC value of 125 μg.mL−1 (6 μg.mL−1 of copper). The excellent antibacterial result was related to high dispersion properties of the hybrid support (β-chitin/DCPA) which avoid the aggregation of Cu(NPs) via various surface bonds with β-chitin biopolymer. Copper-based materials synthesized here exhibit promising antibacterial activities which can be explored in more details in others bacterial strains.