The present study aimed to develop the synthesis of zinc oxide nanoparticles (ZnO-NPs) using the green method, with Aloe barbadensis leaf extract as a stabilizing and capping agent. In vitro antitumor cytotoxic activity, as well as the surface-functionalization of ZnO-NPs and their drug loading capacity against doxorubicin (DOX) and gemcitabine (GEM) drugs, were also studied. Morphological and structural properties of the produced ZnO-NPs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersion X-ray diffraction (EDX), UV-Vis spectrophotometry, Fourier-transform infrared analysis (FTIR), and X-ray diffraction (XRD). The prepared ZnO-NPs had a hexagonal shape and average particle size of 20–40 nm, with an absorption peak at 325 nm. The weight and atomic percentages of zinc (50.58% and 28.13%) and oxygen (26.71% and 60.71%) were also determined by EDAX (energy dispersive x-ray analysis) compositional analysis. The appearance of the FTIR peak at 3420 m^–1 confirmed the synthesis of ZnO-NPs. The drug loading efficiency (LE) and loading capacity (LC) of unstabilized and PEGylated ZnO-NPs were determined by doxorubicin (DOX) and gemcitabine (GEM) drugs. DOX had superior LE 65% (650 mg/g) and higher LC 32% (320 mg/g) than GEM LE 30.5% (30 mg/g) and LC 16.25% (162 mg/g) on ZnO-NPs. Similar observation was observed in the case of PEG-ZnO-NPs, where DOX had enhanced LE 68% (680 mg/g) and LC 35% (350) mg/g in contrast to GEM, which had LE and LC values of 35% (350 mg/g) and 19% (190 mg/g), respectively. Therefore, DOX was chosen to encapsulate nanoparticles, along with the untreated nanoparticles, to check their in vitro antiproliferative potential against the triple-negative breast cancer (TNBC) cell line (MDA-MB-231) through the MTT (3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide) assay. This drug delivery strategy implies that the PEGylated biogenically synthesized ZnO-NPs occupy an important position in chemotherapeutic drug loading efficiency and can improve the therapeutic techniques of triple breast cancer.

The selected six specific bacterial and fungal strains, which caused oral teeth decay were analyzed by antimicrobial iron oxide (Fe₂O₃), copper oxide (Cu₄O₃), and zinc oxide (ZnO) nanoparticles synthesized by aloe barbadensis leaves extract, using agar well diffusion method with 0.9% saline solution. TMOs comparatively had not been focused on oral cavity infectious pathogens to analyze antimicrobial activity. In the present study, TMOs were characterized by UV, SEM, FTIR, and XRD. Oral infectious strains (Escherichia coli, Bacillus subtilis, Bacillus licheniformis, Klebsiella pneumonia) and fungal strains (Aspergillus niger, Candida albicans) were used as test microorganisms. The effect of different concentrations of TMO-NPs (2.5 µg/mL, 5 µg/mL, 10 µg/mL) was studied by zone of inhibition (ZOI), minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). The zinc oxide nanoparticle with least particle-sized (37.8 nm) exhibited highest antimicrobial activity. In future, these zinc-oxide nanoparticles may be used in medicine for oral infectious diseases treatment.