PEG entrapped ZnO synthesized using Calendula officinalis flower extract- physicochemical characterization, in vitro and in vivo biocompatibility assessment, and antibiofilm activity

Bacteria are shown to develop resistance to a majority of commercially available antibiotics, and biofilm formation hinders the reachability of these antibiotics to the target organisms. In this study, we have green-synthesized zinc oxide (ZnO) nanoparticles using Calendula officinalis flower extract and encapsulated the nanoparticles inside a biocompatible polymer, polyethylene glycol (PEG) (PEG-ZnO-CO). The phytochemical analysis and Gas chromatography–mass spectrometry (GC-MS) analysis was done to know the components of the flower extract. The PEG-ZnO-CO nanoparticles were characterized using different techniques like UV–vis spectrophotometry, dynamic light scattering (DLS), zeta potential, Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) analysis. The biocompatibility of the nanoparticles was also monitored using MTT assay, hemolysis assay, and zebrafish embryo study for both in vitro and in vivo analysis, respectively. Finally, the biofilm-inhibiting activity was assessed for S. aureus and Pseudomonas sp. The results showed the hydrodynamic diameter of the nanoparticle to be 130 nm; TEM showed the ZnO nanoparticle size to be 6.7 nm. SEM images showed spherical morphology; zeta potential was −10.47 mV, showing moderate stability. The band gap was 2.29 eV, showing perfect semiconducting properties. The biofilm mass was 0.58 ± 0.03 mg after 100 μg/mL of PEG-ZnO-CO treatment compared to 0.65 ± 0.05 mg in the untreated control for S. aureus . For Pseudomonas sp. , the biofilm mass after 100 μg/mL of PEG-ZnO-CO treatment was 0.58 ± 0.045 mg compared to 0.68 ± 0.05 mg for the untreated control. The PEG-ZnO-CO nanoparticles were biocompatible up to a dose of 50 μg/mL and showed a moderate biofilm inhibition capacity. Further study is needed in the future to explore the antimicrobial activities with other microbial strains.