Research Articles (Biotechnology)

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https://hdl.handle.net/10566/16116

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Browsing by Author "Meyer, Mervin"

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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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    Heterocyclic (pyrazine)carboxamide Ru(II) complexes: structural, experimental and theoretical studies of interactions with biomolecules and cytotoxicity†
    (Royal Society of Chemistry, 2024) Tsaulwayo, Nokwanda; Sibuyi, Nicole Remaliah Samantha; Meyer, Mervin
    Treatments of N-(1H-benzo[d]imidazol-2-yl)pyrazine-2-carboxamide (HL1) and N-(benzo[d]thiazol-2-yl)pyrazine-2-carboxamide carboxamide ligands (HL2) with [Ru(p-cymene)Cl2]2 and [Ru(PPh3)3Cl2] precursors afforded the respective Ru(ii) complexes [Ru(L1)(p-cymene)Cl] (Ru1), [Ru(L2)(p-cymene)Cl] (Ru2), [Ru(L1)(PPh3)2Cl] (Ru3), and [Ru(L2)(PPh3)2Cl] (Ru4). These complexes were characterized by NMR, FT-IR spectroscopies, mass spectrometry, elemental analyses, and crystal X-ray crystallography for Ru2. The molecular structure of complex Ru2 contains one mono-anionic bidentate bound ligand and display pseudo-octahedral piano stool geometry around the Ru(ii) atom. The interactions with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) were investigated by spectroscopic techniques. The experimental binding studies suggest that complexes Ru1-Ru4 interact with DNA, primarily through minor groove binding, as supported by molecular docking results. Additionally, these complexes exhibit strong quenching of the fluorescence of tryptophan residues in BSA, displaying static quenching. The in vitro cytotoxicity studies of compounds Ru1-Ru4 were assessed in cancer cell lines (A549, PC-3, HT-29, Caco-2, and HeLa), as well as a non-cancer line (KMST-6). Compounds Ru1 and Ru2 exhibited superior cytotoxicity compared to Ru3 and Ru4.
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    Phytofabrication of silver nanoparticles using ehretia rigida leaf aqueous extract, their characterization, antioxidant and antimicrobial activities
    (Elsevier Ltd, 2025) Oselusi, Samson; Sibuyi, Nicole; Meyer, Mervin
    The green synthesis of nanoparticles (NPs) offers a sustainable, rapid, and cost-effective alternative to traditional chemical and physical methods, with diverse applications across various fields. This study reports the synthesis of silver nanoparticles (AgNPs) using Ehretia rigida (Er) leaf aqueous extract and evaluates their biological activities. The formation of the NPs was confirmed by the change in colour from clear to dark brown. The synthesis parameters, such as pH, temperature, Er extract and silver nitrate (AgNO3) concentrations, reaction ratio, and incubation time, were optimized for high yields, controlled size, and stability of the NPs. The optimized Er-AgNPs were characterized using ultraviolet–visible (UV–vis) spectroscopy, dynamic light scattering (DLS), Fourier transform infrared (FTIR) spectroscopy, and high-resolution transmission electron microscopy (HR–TEM). The Er-AgNPs sample presented a characteristic absorbance peak at 408 nm, a hydrodynamic size of 74.02 ± 0.19 nm, a polydispersity index (PDI) of 0.39 ± 0.05, and a zeta potential of −25.4 ± 6.26 mV. FTIR analysis revealed the nature of the biomolecules responsible for the reduction and stabilization of the NPs. HR–TEM revealed that the Er-AgNPs were spherical, with core sizes ranging from 6 to 18 nm. The Er leaf aqueous extract and Er-AgNPs possessed antioxidant activities, with the Er leaf extract having higher activity than Er-AgNPs. The Er leaf extract did not exhibit any antimicrobial activity, whereas the Er-AgNPs demonstrated broad-spectrum antimicrobial activities against all the tested pathogens. This study provides a sustainable, easy and cost-effective method to produce AgNPs for biomedical applications.