Endophytic bacterial strain, Brevibacillus brevis-mediated green synthesis of copper oxide nanoparticles, characterization, antifungal, in vitro cytotoxicity, and larvicidal activity

Abstract

The biomass filtrate containing various metabolites of endophytic bacterial strain, Brevibacillus brevis PI-5 was used as a biocatalyst for reducing and stabilizing copper oxide nanoparticles (CuO-NPs). UV-Vis spectroscopy, Fourier transform infrared, transmission electron microscopy, scanning electron microscopy with energy-dispersive X-ray (SEM-EDX), X-ray diffraction, and X-ray photoelectron spectroscopy were used for CuO-NPs characterization. A spherical, well-dispersed, and crystallographic structure with sizes of 2-28 nm was formed. The SEM-EDX confirmed the presence of Cu and O with weight percentages of 27.62% and 48.88%, respectively. The biological activities including antifungal, anticancer, and larvicidal of synthesized CuO-NPs were assessed using the fungal radial growth inhibition, MTT assay method, and mortality percentages, respectively. The obtained data showed that the CuO-NPs exhibit high activity in a dose-dependent manner. The growth of three phytopathogenic fungi, Fusarium oxysporum, Alternaria alternata, and Aspergillus niger was decreased by percentages of 64.5% ± 4.1%, 62.9% ± 0.3%, and 70.2% ± 2.3%, respectively at 300 μg·mL-1. Also, various clinical Candida spp. were successfully inhibited with varied zones of inhibition and minimum inhibitory concentration values in ranges of 6.25-50 μg·mL-1. The in vitro cytotoxicity exhibits target-orientation to breast cancer cells (T47D) at low concentration compared to normal cells (HFB4) with IC50 values of 122.3 ± 5.4 and 229.9 ± 5.7 μg·mL-1, respectively. The mortality percentages of I, II, III, and IV instar larvae of Culex antennatus were 60% ± 1.4%, 43.1% ± 1.1%, 36.2% ± 1%, and 32.1% ± 0.9%, at 10 mg·L-1 and increased to 86.9% ± 2.1%, 68.1% ± 1.7%, 64.4% ± 1.9%, and 53.1% ± 1.4% at 50 mg·L-1, respectively.