Bioactive agar-based functional composite film incorporated with copper sulfide nanoparticles

Copper sulfide nanoparticles (CuS NP) were prepared using copper acetate and thiourea as a source of Cu2+ and S2−, respectively, cornstarch as a stabilizing agent and ammonia as a hydrolyzing agent under a mild condition of sulfidation (70 °C for 1 h). The present work describes the synthesis and preparation of bioactive agar/CuS NP nanocomposite film. CuS NP was characterized using UV-vis spectroscopy, X-ray diffraction pattern, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). CuS NP was roughly spherical and irregular with a size in the range of 2–10 nm with an average of 4.6 ± 1.3 nm. Agar-based films with different concentrations (0.25, 0.50, 1.0 and 2.0 wt%) of CuS NP were prepared and characterized using SEM and Fourier transforms infrared spectroscopy (FTIR), and the film properties such as UV-barrier, mechanical, water vapor barrier, swelling ratio, water solubility, hydrophobicity, thermal stability, antibacterial properties and cytotoxicity were investigated. The CuS NP was well dispersed in the polymer matrix to form compatible nanocomposite films. The swelling ratio and moisture content of the composite films decreased while the water solubility increased slightly after the addition of CuS NP. The composite films showed significantly increased UV-barrier without much sacrifice of transparency, and they also showed increased mechanical strength and water vapor barrier properties. Also, in vitro analysis showed excellent biocompatibility of CuS NP and nanocomposite films on skin fibroblast L929 cell lines with cell viability above 90%. Also, they exhibited distinctive antibacterial activity against food-borne pathogenic bacteria, E. coli and some activity against L. monocytogenes.