Gwada Cynthia A, Ndivhuwo Prince S, Matshetshe Kabo, Aradi Emily, Mdluli Phumlane, Moloto Nosipho, Otieno Francis, Airo Mildred
School of Physical and Biological Sciences, Maseno University Private Bag, Maseno Kenya
Molecular Sciences Institute, School of Chemistry, University of the Witwatersrand Private Bag 3, Wits, 2050 South Africa.
RSC Adv. 2025 May 1;15(18):14170-14181. doi: 10.1039/d4ra08900f. eCollection 2025 Apr 28.
The increasing prevalence of antimicrobial resistance (AMR) bacteria poses a major global health threat, compounded by the limited development of new antibiotics. To address this challenge, alternative strategies, including nanoparticle-based therapies, are being explored. This study investigates the antimicrobial properties of green-synthesized silver nanoparticles (AgNPs) derived from leaf extracts of (OG), (AG), and (AA). These plant extracts act as reducing, capping, and stabilizing agents during the synthesis process. By controlling the reaction parameters, the synthesized AgNPs displayed surface plasmon resonance (SPR) peaks at 434, 427, and 435 nm for OG, AG, and AA, respectively, indicating successful nanoparticle formation. The particles were predominantly spherical, with average sizes of 28.5 ± 6.3 nm (AgNPs-OG), 15.07 ± 3.8 nm (AgNPs-AA), and 20.2 ± 2.5 nm (AgNPs-AG), although some particles exhibited triangular and cylindrical shapes. X-ray diffraction (XRD) confirmed the formation of crystalline, face-centered cubic (FCC) metallic silver, while Fourier Transformation Infrared (FTIR) identified functional groups such as alcohols, amines, amides, carboxyl, and esters capping the surface of AgNPs. Energy dispersive spectroscopy (EDS) further confirmed the purity of the AgNPs. The antimicrobial activity of the synthesized AgNPs was tested against Gram-negative and Gram-positive bacteria. Notably, AgNPs demonstrated high antimicrobial efficacy, particularly with smaller-sized, spherical particles showing superior performance. The minimum inhibitory concentration was as low as 1.016 μg mL, highlighting the strong antimicrobial potential of AgNPs, whereas the minimum bactericidal concentration was recorded for , indicating greater susceptibility of Gram-negative bacteria to AgNPs and a concentration-dependent bactericidal effect. A comparison analysis showed that the antimicrobial effectiveness of the aqueous extract was significantly enhanced when AgNPs were incorporated, whereas higher antimicrobial performance was observed for green-synthesized AgNPs compared with wet chemically synthesized AgNPs reported in the literature. This is attributed to enhanced biocompatibility and a synergistic effect between the nanoparticles and plant-derived bioactive compounds. The mechanism of action of AgNPs involves silver ion (Ag) release and reactive oxygen species (ROS) generation surface oxidation and photoactivation. These findings underscore the potential of green-synthesized AgNPs as an alternative strategy in mitigating AMR.
抗菌耐药（AMR）细菌的日益流行对全球健康构成了重大威胁，而新抗生素开发的有限性更是雪上加霜。为应对这一挑战，人们正在探索包括基于纳米颗粒的疗法在内的替代策略。本研究调查了从 （OG）、 （AG）和 （AA）的叶提取物中绿色合成的银纳米颗粒（AgNPs）的抗菌特性。这些植物提取物在合成过程中充当还原剂、封端剂和稳定剂。通过控制反应参数，合成的AgNPs在OG、AG和AA中分别在434、427和435 nm处显示出表面等离子体共振（SPR）峰，表明成功形成了纳米颗粒。这些颗粒主要为球形，平均尺寸分别为28.5±6.3 nm（AgNPs-OG）、15.07±3.8 nm（AgNPs-AA）和20.2±2.5 nm（AgNPs-AG），不过有些颗粒呈现出三角形和圆柱形。X射线衍射（XRD）证实形成了结晶的面心立方（FCC）金属银，而傅里叶变换红外光谱（FTIR）鉴定出了覆盖在AgNPs表面的醇、胺、酰胺、羧基和酯等官能团。能量色散光谱（EDS）进一步证实了AgNPs的纯度。对合成的AgNPs的抗菌活性针对革兰氏阴性菌 和革兰氏阳性菌 进行了测试。值得注意的是，AgNPs表现出很高的抗菌效力，特别是尺寸较小的球形颗粒表现出卓越的性能。最低抑菌浓度低至1.016 μg/mL，突出了AgNPs强大的抗菌潜力，而 记录到了最低杀菌浓度，表明革兰氏阴性菌对AgNPs更敏感以及存在浓度依赖性杀菌作用。一项比较分析表明，当加入AgNPs时，水提取物的抗菌效果显著增强，而与文献中报道的湿化学合成的AgNPs相比，绿色合成的AgNPs表现出更高的抗菌性能。这归因于纳米颗粒与植物衍生的生物活性化合物之间增强的生物相容性和协同效应。AgNPs的作用机制涉及银离子（Ag）释放和活性氧（ROS）生成 表面氧化和光激活。这些发现强调了绿色合成的AgNPs作为减轻AMR的替代策略的潜力。
