Green synthesis of silver nanoparticles (AgNPs) has been extensively studied by using a variety of plant extracts for applications in biomedical sciences and engineering. However, there are no reports on the synthesis of AgNPs by utilizing the berry extract of Sea Buckthorn, which is a traditional Chinese medicine and exhibits a wide spectrum of antioxidant, anti-inflammatory and anticancer activities. In this paper, we report an easy and eco-friendly technique for the preparation of AgNPs using the Sea Buckthorn berry extract under ultrasonic radiation at ambient temperature and the evaluation of both biosynthesis parameters and biological activities. The UV-visible spectrum and dynamic light scattering (DLS) analysis showed that the size of AgNPs was sensitive to the biosynthesis parameters, such as the pH of the extract, material proportion and reaction time, offering a size-controlled synthetic method for AgNPs. The X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and DLS studies showed that the AgNPs (pH 10.0; material proportion 1 : 1; 4 h) had a face-centered cubic (fcc) structure and spherical shape with an average particle size of 27.3 ± 0.2 nm covered by anions, and existed in a monodispersed form with a polydispersity index (PDI) of 0.213. The biosynthesized AgNPs showed potent anticancer activity against human colorectal cancer (HCT116 and SW620), hepatoma cancer (HepG2), breast cancer (MCF-7) and cervical cancer (HeLa) cell lines as well as strong antioxidant activity. The IC₅₀ values for these five cell lines were 8.77, 4.61, 14.59, 16.05 and 27.98 μg mL⁻¹, respectively. However, the biosynthesized AgNPs revealed poor inhibition activities for the growth of E. coli and S. aureus. These results confirmed that the Sea Buckthorn could be a low-cost, nontoxic and eco-friendly natural resource for the synthesis of AgNPs, which might be useful for the development of new alternative antioxidant and anticancer agents in biomedicine.

Green synthesis of silver nanoparticles (AgNPs) by using the extracts of Chinese herbal medicines (CHMs) has attracted tremendous attention due to the potential synergistic effect between metal nanoparticles and capping agents. However, since CHMs are precious and expensive, finding other cheap and eco-friendly resources for biosynthesizing AgNPs with superior medicinal activites is necessary. Herbal medicine residues (HMRs) are the by-products of traditional Chinese herbal medicine after decoction and were identified to contain approximately 30–50% of medicinally active ingredients, which may be advantageous for green synthesis of medicinal AgNPs. Inspired by this, we present herein the preparation of AgNPs by reusing Bazheng Mixture residues and evaluate both biosynthesis parameters and bioactivities, where Bazheng Mixture is a famous Chinese patent medicine for relieving inflammation and pain, and allaying fever. The UV-visible spectrum and DLS analysis showed that the as-prepared AgNPs were sensitive to pH, material proportion and incubation time, but the yield was impervious to material proportion. TEM, HRTEM, SAED and DLS characterization found that AgNPs (pH 10.0; material proportion 1 : 1; 6 h) had a face-centered cubic (fcc) structure and spherical shape with an average size of 22.2 ± 0.5 nm covered by anions, and existed in monodispersed form with long term stability. The AgNPs displayed potent toxic effects against both cancer cell lines and pathogens, and superior antioxidant activity. The IC₅₀ for HCT116, HepG2 and HeLa cell lines were 13.07, 19.67, and 26.18 μg mL⁻¹, respectively. The MICs of AgNPs for E. coli and S. aureus were both 50.0 μg mL⁻¹. The uptake analysis of AgNPs for both pathogens and cancer cell lines was performed to preliminarily illustrate the mechanism of toxic effects. These results confirm that HMRs could be a low-cost, nontoxic and eco-friendly resource for green synthesis of medicinal AgNPs, and also provide an alternative method for general recycling strategies of HMRs.

Fabrication of silver nanoparticles (AgNPs) using Chinese herbal medicine is popular as the bioactive components included in them would generate potential synergistic effect with the metal nanoparticles. The leaf of Mentha pulegium, whose extract contains a range of phytochemicals and exhibits a wide spectrum of bioactivities, is used as Chinese herbal medicine after drying naturally. Thus, the green synthesis of AgNPs using Mentha pulegium has aroused interests from analysts. However, the biosynthesis of AgNPs under alkaline conditions and the biological activities remain elusive, where alkaline conditions may influence the physicochemical properties and the biological activities of biosynthesized AgNPs. In this study, we were stimulated to fabricate bioactive AgNPs using Mentha pulegium extract under alkaline conditions, accompanied by a systematic evaluation on the effect of biosynthesis parameters on the formation, average size, and polydispersity of AgNPs. Our results showed that alkaline conditions could accelerate the formation of AgNPs with a small average size but at a disadvantage to the polydispersity. Additionally, the as-prepared AgNPs had a hexagonal structure and spherical shape with an average size of 15.7 ± 0.1 nm, existing in the monodispersed form and revealing a high degree of stability. The AgNPs exhibited potent antioxidant and significant inhibitory activity for both bacterial and cancer cell lines. The MIC values of AgNPs for Staphylococcus aureus and Escherichia coli were both 50.0 μg·mL^–1, and the IC₅₀ values for HCT116, HepG2, and HeLa cells were 9.0, 14.5, and 31.5 μg·mL^–1, respectively. The AgNPs biosynthesized using M. pulegium under alkaline conditions, which had a smaller size and more surface loads, are entirely different with those synthesized under acidic conditions, and the anticancer activity increased significantly. The internalization of AgNPs inside these five cells displayed a variant trend with variable AgNPs concentrations, suggesting the different mechanism of cell death. For two pathogens, HCT116 and HepG2 cancer cell lines, both cell wall and intracellular damage may be responsible for the cell death. However, for Hela cell line the cell death may be rooted in oxidative stress or intracellular penetration. These results confirmed that the AgNPs biosynthesized from M. pulegium extract under alkaline conditions would act as better anticancer agents in biomedicine.

Since silver nanoparticles (AgNPs) synthesized by using plant extracts revealed varied biological activities, the green synthesis of AgNPs has attracted considerable attention. Although the green synthesis of AgNPs have been accomplished by using the extracts of Cornus Officinalis, which is a traditional Chinese medicine and exhibits a wide spectrum of phytochemicals. The effects of biosynthesis parameters on reducing reaction, stability and more broad biological activities of so-prepared AgNPs did not been evaluated. In this paper, we firstly assessed the effects of UV radiation, pH, material proportion and radiation times on the green synthesis of AgNPs under 365 nm UV radiation by UV-visible spectrum and dynamic light scattering (DLS) analysis. The results showed that UV radiation could accelerate the formation of AgNPs and influence the average size below pH 7.0, and the size of so-prepared AgNPs were sensitive to the pH and material proportion, but no obvious changes to UV radiation times, offering a size-controlled synthetic method for AgNPs. The further X-ray diffraction (XRD), transmission electron microscopy (TEM) and DLS studies showed AgNPs synthesized at pH 7.0, extract: AgNO₃ = 1 : 1 and after 4 h UV radiation were a face-centered cubic (fcc) structure and both spherical and polygonal in shape with average particle size of 64.5 ± 0.3 nm existed in a monodispersed form. Subsquently, the stability of AgNPs was analyzed by zeta potential (−24.8 mV) and the average size measurement after 30 days storage (63.3 ± 0.4 nm), revealing a high degree of stability. Lastly, the investigation of biological activities showed that the biosynthesized AgNPs had potent antioxidant activity, antimicrobial activity against both S. aureus and E. coli as well as anticancer activity against HCT116 and HepG2 cell lines but negligible cytotoxicity against SW620. And the internalization of biosynthesized AgNPs inside the bacterial cell was evaluated by flow cytometric analysis, where the SSC values have significant increase after treating with nanoparticles. These results confirmed that the biosynthesis parameters on the green synthesis of AgNPs by using Cornus Officinalis extract also played pivotal roles and so-prepared AgNPs would be useful for the development of new alternative antioxidant, antimicrobial and anticancer agents in biomedicine.