Browsing by Author "Botha, Subelia"

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    Antioxidant and antimicrobial activities of green-synthesized silver nanoparticles using a cocktaila aqueous extract of capparis sepiaria root and tabernaemontana elegans bark
    (Wiley, 2025) Mashilo, Cate M.; Sibuyi Nicole RS; Botha, Subelia; Meyer, Mervin; Madiehe, Abram M
    The increasing incidence of antimicrobial resistance (AMR) poses a serious threat to public health, which necessitates the development of alternative countermeasures to combat it. Green nanotechnology, in particular the use of silver nanoparticles (AgNPs), shows promise in combating AMR. Although the synthesis of AgNPs using medicinal plant extracts has been explored, combining extracts from two medicinal plants to synthesize AgNPs with enhanced properties has received less attention. Therefore, this study addresses this gap by presenting the green synthesis of AgNPs using a cocktail of Capparis sepiaria–Tabernaemontana elegans (CsTe) aqueous extract as reducing, stabilizing, and capping agents. The focus is on assessing the antioxidant and antimicrobial activities of the synthesized CsTe-AgNPs. Various parameters, such as pH, temperature, extract and silver concentrations, reaction ratio, and synthesis time, were optimized to enhance the efficiency of CsTe-AgNPs synthesis. The CsTe- AgNPs were monodispersed and spherical, with an average core size of 14 ± 2.953 and 7 ± 3.849 nm, and hydrodynamic size of 23 ± 12.260 and 138 ± 2.086 nm for pH = 6 and pH = 11, respectively. The FTIR analysis revealed a shift in peaks of biomolecules present in the CsTe extracts that could be responsible for the reduction of Ag salt to form CsTe-AgNPs. Notably, CsTe-AgNPs_pH11 had potent antimicrobial activity, with a minimum inhibitory concentration (MIC) of 12.5 ± 0 μg/mL against K. pneumoniae and P. aeruginosa, and a slightly higher MIC for C. albicans of 25 ± 5.449 μg/mL. This study demonstrated the effectiveness of using a mixture of two extracts to synthesize AgNPs with enhanced antioxidant and antimicrobial activities, and therefore, could serve as a promising reagent to combat AMR.
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    Functional metal oxides synthesized using natural extracts from waste maize materials
    (Elsevier, 2021) Nwanya, Assumpta Chinwe; Botha, Subelia; Ezema, Fabian I.
    We show in this article the possibilities of employing an environmentally friendly, uncomplicated, economical and sustainable green synthesis technique effected by natural extracts from waste maize (zea mays lea) materials to synthesize some functional transition single metal oxide nanoparticles (NPs). Copper oxides (Cu2O and CuO), zinc oxide (ZnO), nickel oxide (NiO), chromium oxide (Cr2O3), iron oxide (Fe2O3) and cadmium oxide (CdO) were successfully synthesized using this facile method. Structural characterizations by X-ray diffraction (XRD) for the various oxides show the phases and space groups corresponding to their individual structures. Images from the high resolution transmission electron microscope (HRTEM) revealed various shapes and sizes of the obtained nanoparticles. Results from the attenuated total reflection-Fourier transform infrared (ATR-FTIR) revealed different kinds of functional groups present in the synthesized metal oxide nanoparticles. We showed that the phytochemicals in the natural extracts obtained from the waste materials from Zea mays lea plant is pivotal to the bio-reduction, stabilization and chelation of the metal oxide nanoparticles.
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    The potential of chalcone-capped gold nanoparticles for the management of diabetes mellitus
    (Surfaces and Interfaces, 2021-08) Pearce, Brendon; Benjeddou, Mongi; Botha, Subelia; Omolaja, Akinfenwa, A; Omuruyia, Sylvester, I; Badmus, Jelili, A; Ismail, Enas; Marnewick, Jeanine; Ekpob, Okobi, E; Hussein, Ahmed, A
    Searching for new natural bioactive capping agents represent an urgent priority in the green synthesis of metal nanoparticles. Additionaly, the biosaftey of metal nanparticles is a major concern especially in medical applications. Recently, the use of pharmacollogicaly active natural products as capping agents has been deployed to avoid toxic effects during the nanoparticles preparation and to enhance their drugability compared with convential drugs. Helichrysum foetidum is a South African medicinal plant used in folk medicine for the treatment of different human pathologies, and it is known to contain a variety of bioactive compounds. Herein, the total extract and two pure chalcones, helichrysetin and helichrysin, isolated from the same plant were successfully used to synthesize quasi-monodispersed gold nanoparticles in the size range of 2–12 nm. The bio-evaluation of samples indicated that the AuNP/capping agent conjugates are biostable, and have different biological profiles from the total extract/pure compounds. The enzymatic inhibition assays showed significant inhibition by the total extract, helichrysetin and their gold nanoparticles. Interestingly, a similar activity was observed for glucose uptake in HEK293 treated cells. On the other hand, all the tested samples relatively demonstrated no cytotoxicity when tested against the HaCaT keratinocytes. In conclusion, the study demonstrated potential enhancement of glucose uptake in mammalian kidney cells, and inhibition of carbohydrate-hydrolysing enzymes by green synthesized gold nanoparticles of H. foetidum. It also provides a therapeutic appraisal of AuNPs/chalcones conjugate towards the development of antidiabetes drugs derived from H. foetidum and its gold nanoparticles.
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    Synthesis and characterization of silver nanoparticles for photovoltaic application
    (2013) Adam, Razia Zulfikar; Botha, Subelia; Muller, Theo
    With an increase in the amount of harmful carbon emissions in the atmosphere as well as a decrease in the availability of fossil fuels, there is a relatively high demand for alternate energy devices. Solar cells have become an alternative option in aid of leading the way for clean energy; however these devices are relatively expensive and have an efficiency that is relatively low in comparison to that of fossil fuelled energy. As a result the cost of the solar cell needs to be reduced by reducing the amount of silicon used in order to compete with fossil fuelled devices; however this decrease would lead to a decrease in efficiency. In recent years silver nanoparticles have been extensively researched as a result of its extraordinary optical, electrical, catalytic, magnetic and antibacterial properties. As a result of these properties, the nanoparticles may be applied to many research areas such as photovoltaics, catalysis and medical fields. The optical properties of silver nanoparticles may thus be exploited in order to increase absorption and in turn the efficiency of the solar cell devices. This study focuses on the optimization of the polyol synthesis to possibly obtain uniformly dispersed silver nanoparticles. The silver nanoparticles would then be incorporated onto amorphous silicon thin films, deposited by hot wire chemical vapour deposition, by spraying a suspension of the silver nanoparticles onto the thin films. The silver nanoparticles were viii characterized by Ultra Violet Visible Spectroscopy (UV-VIS), High Resolution Transmission Electron Microscopy, X-ray Diffraction, and Thermogravimetric Analysis. The thin films with the incorporated silver nanoparticles were characterized by UV-VIS, and High Resolution Scanning Electron Microscopy. It was shown that silver nanoparticles with various morphologies were produced by the polyol synthesis and may be used to enhance light trapping of thin film photovoltaic devices.