Green-synthesized ZnO–MnO nanocomposite as a potent antimicrobial and antibiofilm agent: protein leakage mechanism and synergistic interaction with cefotaxime

Introduction Multidrug-resistant (MDR) Acinetobacter baumannii infection is a major global public health concern due to its rapid emergence and increasing resistance to conventional antimicrobial agents. Therefore, the development of novel and environmentally friendly antimicrobial alternatives is urgently needed. Methods In this study, zinc oxide–manganese oxide bimetallic nanocomposite (ZnO–MnO BNC) was successfully synthesized using potato peel extract through a green synthesis approach. The synthesized nanocomposite was characterized using UV–Vis spectroscopy, FTIR, TEM, and XRD analyses. Its biological activities, including cytotoxic, antibacterial, antibiofilm, bactericidal, and synergistic effects with cefotaxime, were evaluated. Results UV–Vis spectroscopy showed characteristic absorption peaks at 300 and 380 nm, confirming nanocomposite formation. FTIR analysis identified the functional groups responsible for bioreduction and stabilization, along with Zn–O and Mn–O bonds. TEM analysis revealed nanosized particles ranging from 10 to 60 nm with an average size of approximately 35 nm, while XRD confirmed the crystalline structure of ZnO and MnO phases. Biological evaluation demonstrated moderate toxicity toward WI-38 normal cells (IC50 = 168.34 μg/mL) and strong anticancer activity against Hep-G2 and MCF-7 cell lines, with IC50 values of 30.56 and 56.1 μg/mL, respectively. The ZnO–MnO BNC exhibited potent antibacterial activity against MDR Acinetobacter baumannii clinical isolates, producing inhibition zones up to 20.33 ± 0.58 mm and minimum inhibitory concentrations ranging from 32 to 512 μg/mL. Additionally, the nanocomposite showed significant antibiofilm activity (up to 62.99%), rapid bactericidal kinetics, time-kill efficacy, and pronounced protein leakage (up to 73.46%). Synergistic interaction with cefotaxime further enhanced antibacterial activity. Discussion The findings highlight the potential of biogenic ZnO–MnO BNC as an eco-friendly nanoplatform with promising antimicrobial and anticancer applications. The strong antibacterial, antibiofilm, and synergistic activities suggest its possible use as an alternative strategy to combat MDR bacterial infections.