Antioxidant, Antibacterial and Antibiofilm Potential of Green Synthesized Silver-Zinc Oxide Nanocomposites from Curcuma longa Extract against Multi-Drug-Resistant Enteroaggregative E. coli

Enteroaggregative Escherichia coli (EAEC) has been widely recognized as one of the leading causes of infantile diarrhoea and nutrient malabsorption in developing as well as developed countries. In recent years, drug resistance, particularly multi-drug resistance (MDR), among the EAEC strains has been widely documented and could result in a therapeutic stumble. Antimicrobial alternatives are widely employed to curb this emerging public health crisis. In the present study, a facile one-pot synthesis of silver/zinc oxide nanocomposites (Ag/ZnO NCs) using a methanolic extract of stem and leaves of Curcuma longa was performed. The synthesis of Ag/ZnO NCs was confirmed using UV-vis spectroscopy and Fourier transform infrared spectroscopy, while the thermal stability was ascertained by thermogravimetric analysis with differential thermogravimetric analyses, and crystallinity was determined using powder X-ray diffraction. The shape and size of the green synthesized Ag/ZnO NCs, determined using field-emission–scanning-electron microscopy and transmission electron microscopy, revealed an irregular polycrystalline morphology with a size of 31.34 ± 1.27 nm. Later, the antibacterial potential of the green synthesized Ag/ZnO NCs evaluated against MDREAEC strains revealed a minimum inhibitory concentration of 31.25 μg/mL and a minimum bactericidal concentration ranging from 62.50 to 125 μg/mL. Moreover, the green synthesized Ag/ZnO NCs inhibited the biofilm-forming ability of the tested strains of MDR-EAEC. Furthermore, concentrationdependent antioxidant activity was exhibited by the green synthesized Ag/ZnO NCs, as evidenced by the ABTS assay and reducing power assay. Overall, this study demonstrated the antibacterial potential of Ag/ZnO NCs synthesized using C. longa extracts with antifouling as well as antioxidant properties, which could be used as an alternative therapeutic candidate.