KH. T. 2‑Mediated Synthesis of Gold and Silver Nanoparticles: Optimization, Characterization, and Inhibitory Efficiency Against Malignant and Bacterial Cells

Abstract

Metallic nanoparticles (NPs) are effective in various biological processes. In particular, gold (Au) and silver (Ag) NPs have unique properties that make them ideal candidates for therapeutic applications. This study aimed to explore the potential of a new isolate, KH.T.2, for the extracellular synthesis of Au- and AgNPs and to evaluate their anticancer and antibacterial activities. The cyanobacteria were isolated and morphologically and genetically identified; their chemical constituents were detected using LC-QTOF-MS. KH.T.2 mediated the syntheses of Au and Ag NPs using two methods (cell-free media and cell biomass extracts). The syntheses were optimized by controlling various parameters, such as the concentration, temperature, illumination, and pH, to obtain small and stable LC_Bio@AgNPs, LC_Sup@AgNPs, LC_Sup@AuNPs, and LC_Bio@AuNPs. The NPs were physicochemically characterized, and their antibacterial and anticancer activities were studied. Au and Ag NPs were successfully synthesized by KH.T.2, suggesting that their peptides, amino acids, polysaccharides, and fatty acids were the main reagent-mediated synthesis. LC_Bio@AgNPs, LC_Sup@AgNPs, LC_Sup@AuNPs, and LC_Bio@AuNPs are small and negatively charged, enabling them to be used as antibacterial and anticancer agents. KH.T.2 represented a novel source for synthesizing Au and Ag NPs, and these NPs have been demonstrated to be effective therapeutic agents.

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Phylogenetic tree of the 16s rRNA sequence of K. iranica KH.T.2 was built using the cluster method and MEGA4 software version 10.2.6.

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Segmented filamentous shape of K. iranica KH.T.2 under light (A,B), inverted light (C,D), and scanning electron microscopes (E,F). Scale bar of 20 μm (A–E) and 2 μm (F).

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Wavelengths (nm) of LC_Bio@AgNPs, LC_Sup@AgNPs, LC_Bio@AuNPs, and LC_Sup@AuNPs synthesized by K. iranica KH.T.2 under various reaction parameters, including concentration, temperature, illumination, reaction time, and pH.

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Wavelengths (nm) of LC_Bio@AgNPs, LC_Sup@AgNPs, LC_Bio@AuNPs, and LC_Sup@AuNPs following the synthesis under optimal reaction conditions.

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FTIR spectra of functional groups on the surface of LC_Bio@AgNPs, LC_Sup@AgNPs, LC_Bio@AuNPs, and LC_Sup@AuNPs synthesized by K. iranica KH.T.2.

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TEM micrographs and frequency distribution analysis of particle size of LC_Bio@AgNPs (A,B), LC_Sup@AgNPs (C,D), LC_Bio@AuNPs (E,F), and LC_Sup@AuNPs (G,H). Scale bars of 50 nm (A,B,D) and 20 nm (C). The attached HR-TEM micrograph in D has a scale bar of 5 nm.

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SEM micrographs illustrating the shapes of LC_Bio@AgNPs (A), LC_Sup@AgNPs (B), LC_Bio@AuNPs (C), and LC_Sup@AuNPs (D) synthesized by K. iranica KH.T.2. Scale bar of 100 nm (A,C,D) and 200 nm (B).

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Elemental compositions of LC_Bio@AgNPs (A), LC_Sup@AgNPs (B), LC_Bio@AuNPs (C), and LC_Sup@AuNPs (D) detected by EDx analysis.

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Elemental distribution of LC_Bio@AgNPs (A), LC_Sup@AgNPs (B), LC_Bio@AuNPs (C), and LC_Sup@AuNPs (D) synthesized by K. iranica KH.T.2.

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HDs (nm) and potential charges (mV) of LC_Bio@AgNPs (A,B), LC_Sup@AgNPs (C,D), LC_Bio@AuNPs (E,F), and LC_Sup@AuNPs (G,H) synthesized by K. iranica KH.T.2, respectively.

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Cell viabilities of HeLa (A), HepG2 (B), A549 (C), and OEC (D) cell lines before and after treatment with LC_Bio@AgNPs, LC_Sup@AgNPs, LC_Bio@AuNPs, and LC_Sup@AuNPs synthesized by K. iranica KH.T.2. Data are presented as the mean ± SEM; P-values were calculated versus control cells: ****P < 0.0001, ***P < 0.0001, **P < 0.005, and *P < 0.01.

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Antibacterial activities of LC_Bio@AgNPs, LC_Sup@AgNPs, LC_Bio@AuNPs, and LC_Sup@AuNPs synthesized by K. iranica KH.T.2 against S. pneumoniae (A), E. coli (B), and S. aureus (C). Hand-written letters on plates A, B, C, D, and E refer to LC_Bio@AgNPs, LC_Sup@AgNPs, LC_Bio@AuNPs, LC_Sup@AuNPs, and ciprofloxacin, respectively.