Rowan Berries: A Potential Source for Green Synthesis of Extremely Monodisperse Gold and Silver Nanoparticles and Their Antimicrobial Property

Rowanberries (Sorbus aucuparia) are omnipresent in Europe. The medicinal importance of rowanberries is widely known and corresponds to the active ingredients present in the fruits, mainly polyphenols, carotenoids, and organic acids. In the current study, we explored rowanberries for the reduction of gold and silver salts into nanoparticles. Rowanberries-mediated gold nanoparticles (RB-AuNPs) formed within 5 s at room temperature, and silver nanoparticles (RB-AgNPs) formed in 20 min at 90 °C. The produced nanoparticles were thoroughly characterized by UV-Vis spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), dynamic light scattering (DLS), single-particle inductively coupled plasma–mass spectrometry (sp-ICP-MS), thermogravimetric analysis (TGA), Fourier transform-infrared spectroscopy (FT-IR) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF). The characterization confirmed that the nanoparticles are highly monodisperse, spherical, stable over long periods, and exhibit a high negative zeta potential values. The produced RB-AuNPs and RB-AgNPs were 90–100 nm and 20–30 nm in size with a thick biological corona layer surrounding them, providing extreme stability but lowering the antimicrobial activity. The antimicrobials study of RB-AgNPs revealed that the nanoparticles have antimicrobial potential with an MBC value of 100 µg/mL against P. aeruginosa and 200 µg/mL against E. coli.

Biomimetically Generated Nanoparticles in Boosting the Performance of Microbial Fuel Cells

Studies are presented in the context of the past attempts at finding nanocatalysts that can boost the performance of microbial fuel cells (MFCs) ? in terms of waste treatment and energy generation. Given the great potential of biomimetically synthesized nanoparticles (BMNPs) in providing less expensive and more environmentally friendly alternatives to NPs synthesized by physical and chemical methods, as well as a near-total lack of previous work in this area, the current research was undertaken. Effect of gold and silver nanoparticles (NPs), synthesized biomimetically using five freely available weeds, was assessed as catalysts in the MFCs. In all cases, the nanoparticles were seen to enhance the coulombic efficiency (reflective of the reduction in the waste’s organic carbon load), maximum attainable power density, and overall energy yield of the MFCs by >200% relative to the uncatalyzed MFCs. Gold nanoparticles were more effective than silver nanoparticles by ? 20%. The results reveal that biomimetically synthesized NPs can be highly effective in reducing the operational costs as well as ecological footprints of MFCs and further work should be focused on NPs of non-precious metals.

Gold and silver nanoparticles as high-value colourants and multi-functional entities for natural fibres and minerals

<p>Significant opportunities exist in both the scientific and industrial sectors for the development of novel multi-functional materials that combine the inherent properties of all precursor components in a synergistic manner, thereby providing new products and opportunities. Processes that add value to natural materials in a facile and refined manner are particularly sought after. Thus this research combines useable substrates, notably natural protein fibres and minerals with gold or silver nanoparticles, producing high value, multi-functional materials that display the strength, softness and shine (of the protein fibres), or high surface area and dispersibility (of the minerals) with the high value and wealth associated with the noble metal nanoparticles, their broad spectrum of intense colours, anti-microbial, insecticide and anti-static properties. This adds significant worth to the substrates, transforming them from commodities to valuable materials. Silk, merino wool and crossbred wool were the natural fibres employed kaolinite and halloysite clays the minerals. They were combined with gold and silver nanoparticles of various sizes and shapes (and hence colours) producing the following composite materials: • Gold nanoparticle-merino wool composites • Gold nanoparticle-crossbred wool composites • Gold nanoparticle-silk composites • Silver nanoparticle-kaolinite composites • Silver nanoparticle-halloysite composites The most successful method for producing silver nanoparticle-clay composites involved the external preparation of silver nanoparticles and their subsequent attachment to the clay substrates by means of a layer-by-layer deposition approach, which capitalised on electrostatic interactions between oppositely charged polyelectrolytes capping the nanoparticles and bound to the clay surfaces. Three general approaches were employed in the production of the gold nanoparticle-natural fibre composite materials. The nanoparticles were either synthesised ex-situ and subsequently attached to the fibres, or the natural fibres were utilised as redox active biotemplates in which the wool or silk absorbed and subsequently reduced Au³⁺ to nanoparticulate Au⁰ on and within the fibres. Thirdly, a seed mediated growth approach was employed in which additional Au³⁺ was reduced to nanoparticulate Au⁰ on the surface of gold nanoparticles already bound to the fibres. This was facilitated by an external reductant.</p>

Gold and silver nanoparticles as high-value colourants and multi-functional entities for natural fibres and minerals

<p>Significant opportunities exist in both the scientific and industrial sectors for the development of novel multi-functional materials that combine the inherent properties of all precursor components in a synergistic manner, thereby providing new products and opportunities. Processes that add value to natural materials in a facile and refined manner are particularly sought after. Thus this research combines useable substrates, notably natural protein fibres and minerals with gold or silver nanoparticles, producing high value, multi-functional materials that display the strength, softness and shine (of the protein fibres), or high surface area and dispersibility (of the minerals) with the high value and wealth associated with the noble metal nanoparticles, their broad spectrum of intense colours, anti-microbial, insecticide and anti-static properties. This adds significant worth to the substrates, transforming them from commodities to valuable materials. Silk, merino wool and crossbred wool were the natural fibres employed kaolinite and halloysite clays the minerals. They were combined with gold and silver nanoparticles of various sizes and shapes (and hence colours) producing the following composite materials: • Gold nanoparticle-merino wool composites • Gold nanoparticle-crossbred wool composites • Gold nanoparticle-silk composites • Silver nanoparticle-kaolinite composites • Silver nanoparticle-halloysite composites The most successful method for producing silver nanoparticle-clay composites involved the external preparation of silver nanoparticles and their subsequent attachment to the clay substrates by means of a layer-by-layer deposition approach, which capitalised on electrostatic interactions between oppositely charged polyelectrolytes capping the nanoparticles and bound to the clay surfaces. Three general approaches were employed in the production of the gold nanoparticle-natural fibre composite materials. The nanoparticles were either synthesised ex-situ and subsequently attached to the fibres, or the natural fibres were utilised as redox active biotemplates in which the wool or silk absorbed and subsequently reduced Au³⁺ to nanoparticulate Au⁰ on and within the fibres. Thirdly, a seed mediated growth approach was employed in which additional Au³⁺ was reduced to nanoparticulate Au⁰ on the surface of gold nanoparticles already bound to the fibres. This was facilitated by an external reductant.</p>

Cytotoxic Effects of Phytomediated Silver and Gold Nanoparticles Synthesised from Rooibos (Aspalathus linearis), and Aspalathin

The green chemistry approach has continuously been applied for the synthesis of functional nanomaterials to reduce waste, environmental hazards, and the use of toxic chemicals among other reasons. Bioactive natural compounds have been found great potential in this regard and are used to improve the stability, activity, and biodistribution of metal nanoparticles (MNPs). Aspalathin (ASP) from Aspalathus linearis (rooibos) has a well-defined pharmacological profile and functional groups capable of both reducing and capping agents in the synthesis of metallic nanoparticles (NP). This study provides the first report of the phytomediated synthesis of gold and silver nanoparticles (AuNPs/AgNPs) via ASP and the green rooibos (GR) extract. The study demonstrated a green chemistry approach to the biosynthesis of nanoparticles of GR-AuNPs, ASP-AuNPs, GR-AgNPs, and ASP-AgNPs. The results showed that GR and ASP could act both as reducing and stabilising agents in the formation of crystalline, with different shapes and dispersity of NPs in the ranges of 1.6–6.7 nm for AgNPs and 7.5–12.5 nm for the AuNPs. However, the ASP NPs were less stable in selected biogenic media compared to GR NPs and were later stabilised with polyethene glycol. The cytotoxicity studies showed that GR-AgNPs were the most cytotoxic against SH-SY5Y and HepG2 with IC50 108.8 and 183.4 μg/mL, respectively. The cellular uptake analysis showed a high uptake of AuNPs and indicated that AgNPs of rooibos at a lower dose (1.3–1.5 μg/mL) is favourable for its anticancer potential. This study is a contribution to plant-mediated metallic nanoparticles using a pure single compound that can be further developed for targeted drug delivery for cancer cells treatments in the coming years.

Current Knowledge of Silver and Gold Nanoparticles in Laboratory Research—Application, Toxicity, Cellular Uptake

Silver and gold nanoparticles can be found in a range of household products related to almost every area of life, including patches, bandages, paints, sportswear, personal care products, food storage equipment, cosmetics, disinfectants, etc. Their confirmed ability to enter the organism through respiratory and digestive systems, skin, and crossing the blood–brain barrier raises questions of their potential effect on cell function. Therefore, this manuscript aimed to summarize recent reports concerning the influence of variables such as size, shape, concentration, type of coating, or incubation time, on effects of gold and silver nanoparticles on cultured cell lines. Due to the increasingly common use of AgNP and AuNP in multiple branches of the industry, further studies on the effects of nanoparticles on different types of cells and the general natural environment are needed to enable their long-term use. However, some environmentally friendly solutions to chemically synthesized nanoparticles are also investigated, such as plant-based synthesis methods.