Antibacterial and Antifungal Efficacy of Phyto-synthesized Cobalt Nanoparticles Synthesized Using Aloe vera (Aloe barbadensis Miller) Extract.

Abstract

Antimicrobial resistance is exponentially increasing because microbes evolve new ways to evade treatment. Therefore, threatening our ability to treat common bacterial and fungal diseases. This research work covers the synthesis of cobalt nanoparticles using extract of Aloe vera, characterization, and antimicrobial activity. Phytochemical screening of aqueous extract of Aloe vera was carried out in accordance with established methods. Co NPs were synthesized using the bottom-up method of synthesis and characterized using FTIR, UV-Vis spectrophotometry, SEM, and XRD. Prominent absorption peaks appeared at 3405 cm⁻¹, which was ascribed to OH vibration; 2923 cm⁻¹, assigned to Sp3 C-H; sp³ 1634 cm⁻¹, assigned to C=O; and the characteristic metal-oxygen peak appeared at 650 cm⁻¹. UV-visible analysis showed wavelengths of maximum absorption (λmax) at about 380 nm and 400 nm. The SEM analysis of Co NPs showed irregular morphology. While the closest crystalline structure was body-centered cubic (BCC) with a size of 10.43 nm.

The synthesized Co NPs were employed for antibacterial and antifungal studies against two gram-negative bacteria, Escherichia coli and Salmonella typhi. Two gram-positive bacteria, Staphylococcus aureus and Helicobacter pylori, and two fungi, Aspergillus niger and Candida. The result showed the highest inhibition at 28 mm, 26 mm, 20 mm, and 15 mm for E. coli, S. typhi, H. pylori, and Staph. aureus, respectively. Also, 21 and 20 mm for two fungi, Aspergillus Niger and Candida. Augmentin and ketoconazole were used as bacterial and fungal control drugs. The cytotoxicity (brine shrimp lethality assay) of the plant extract did not pose significant acute toxicity to the brine shrimp, while Co NPs demonstrated a clear concentration-dependent pattern.