Green synthesis of copper nanoparticles by using pineapple peel waste: in vitro characterizations and antibacterial potential

Abstract

A considerable amount of fruit waste is being produced every day worldwide. The green synthesis of metal nanoparticles from fruit peel waste can be an innovative, cost-effective, and eco-friendly alternative to traditional methods. Copper nanoparticles (CuNPs) were synthesized by a green method using the pineapple peels extract (PLX) and copper sulfate pentahydrate. The formation of CuNPs was visually identified and detected by UV-Visible spectroscopy. The CuNPs were characterized by Fourier-transform infrared (FTIR) spectroscopy, particle size analyzer, scanning electron microscopy (SEM), and X-ray diffraction (XRD). The antioxidant and reducing power of CuNPs were conducted by %DPPH scavenging and electron transfer-based ferric reducing antioxidant power (FRAP) assay, respectively. The antibacterial properties of CuNPs were determined in gram-positive, and gram-negative bacteria. The results showed that the CuNPs were spherical in shape with mean particle size 290.5 nm. The zeta potential of the nanoparticles was found to be - 12.3 mV indicating the instability in the colloidal state. The FTIR study confirmed the peaks of phytochemicals present in the PLX and the nanoparticles supporting the use of pineapple peels as stabilizing, reducing and capping agents. Both the DPPH and reducing power assay depicted that the synthesized CuNPs had significant antioxidant activity. However, the synthesized CuNPs had strong inhibitory capacity against both gram-positive and gram-negative test organisms. Thus, the CuNPS could be used for its viable antibacterial potential to preserve fruits, flowers, and vegetables from bacterial contamination.

Keywords: Antibacterial potential; Antioxidant activity; Copper nanoparticles; Copper sulphate; Green synthesis; Pineapple peels.