Comparative analysis: particle size and bactericidal efficacy of zinc oxide nanoparticles with aloe vera gel versus aloe vera gel-honey

In the realm of nanoscience, the inherent antibacterial potential of nanoparticles (NPs) stands as an alluring prospect for the development of pharmaceutical interventions. Yet, conventional chemical and physical NPs fabrication methods pose environmental and safety concerns. The aim of this study is to greenly-synthesize zinc oxide nanoparticles (ZnO NPs) using aloe vera gel (AVG) and aloe vera gel-honey (AVG-honey) under different reactant-to-chemical reductant (or precursor-to-reducing agent) ratio conditions, facilitated by sonication. Structural and optical characteristics of synthesized ZnO NPs were explicated through Fourier Transformation Infrared Spectroscopy (FTIR) and Ultraviolet-visible Spectroscopy (UV-vis). Concurrently, x-ray diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM) delineated the crystalline disposition and morphological behaviors. The antibacterial susceptibility of ZnO NPs against Methicillin-resistant Staphylococcus aureus (MRSA) and Klebsiella Pneumoniae (K. pneumoniae) was investigated using the disc diffusion method. The structures of biosynthesized ZnO NPs were confirmed through distinctive peaks in FTIR and UV-vis spectra. XRD unveils hexagonal wurtzite crystallinity, while FESEM captured distinct morphologies, which are spherical and rice-shaped, in ZnO NPs/AVG, while ZnO NPs/AVG-honey revealed micro-size spherical structures surrounded by numerous tiny lumps. Notably, ZnO NPs/AVG at a 1:6 ratio exhibits a 26.5 nm size, showcasing superior antibacterial efficacy against MRSA (ZOI = 12 mm) and K. pneumoniae (ZOI = 13 mm) compared to other reactant-to-chemical reductant ratios and ZnO NPs/AVG-honey. In conclusion, the study revealed that ZnO NPs synthesized solely using AVG exhibited finer particle sizes and slightly enhanced antibacterial efficacy compared to ZnO NPs formulated with a combination of AVG and honey. This outcome shows that utilization of two reducing agents will contribute to large size of nanoparticles, thus reduce the efficiency of the antibacterial susceptibility. Moreover, the concentration ratios of reactants-to-chemical reductants emerged as crucial determinants in the nanoparticle synthesis process.