Green biochemistry approach for synthesis of silver and gold nanoparticles using Ficus racemosa latex and their pH-dependent binding study with different amino acids using UV/Vis absorption spectroscopy

Efficient synthesis of amino acids capped gold nanoparticles from easily reducible aryldiazonium tetrachloroaurate(III) salts for cellular uptake study

Biomimetic synthesis of gold nanoparticles (GNPs) is critical in biomedical applications. Gold bioconjugates were fabricated by capping the water-dispersible gold-carbon nanoparticles with tyrosine, tryptophan and cysteine amino acids. Incubation of the water-soluble and easily reducible aryldiazonium gold(III) salt [HOOC-4-C₆H₄N≡N]AuCl₄ with amino acids at room temperature formed a purple color over a few minutes with tryptophan and tyrosine and over two hours with cysteine. Rarely that cysteine is capable of reducing gold(III) precursors; however, a cysteine capped gold bioconjugate was synthesized and characterized in this study. Capping GNPs with amino acids was confirmed by high resolution transmission electron microscopy (TEM) and agarose gel electrophoresis. Depending on the amino acid, synthesized particles size was 27.2 ± 5.4 nm, 14.6 ± 7.7 nm and 8.6 ± 2.6 nm for tyrosine, tryptophan and cysteine, respectively. The amino acids capped GNPs showed negligible cytotoxicity to human dermal normal fibroblast cell lines. The highly water dispersible bioconjugates were studied for in vitro cellular uptake by HeLa cancer cells using confocal laser scan microscopy (CLSM) after being labelled with FITC (GNPs-COOH-FITC) and the nuclei were counter stained with DAPI fluorescent dyes. The biomimetic route for the synthesis of the amino acids reduced gold-carbon nanoparticles will benefit the applications in biomedical devices and biosensors.

Recent Developments in the Facile Bio-Synthesis of Gold Nanoparticles (AuNPs) and Their Biomedical Applications

Gold nanoparticles (AuNPs) are extensively studied nanoparticles (NPs) and are known to have profound applications in medicine. There are various methods to synthesize AuNPs which are generally categorized into two main types: chemical and physical synthesis. Continuous efforts have been devoted to search for other more environmental-friendly and economical large-scale methods, such as environmentally friendly biological methods known as green synthesis. Green synthesis is especially important to minimize the harmful chemical and toxic by-products during the conventional synthesis of AuNPs. Green materials such as plants, fungi, microorganisms, enzymes and biopolymers are currently used to synthesize various NPs. Biosynthesized AuNPs are generally safer for use in biomedical applications since they come from natural materials themselves. Multiple surface functionalities of AuNPs allow them to be more robust and flexible when combined with different biological assemblies or modifications for enhanced applications. This review focuses on recent developments of green synthesized AuNPs and discusses their numerous biomedical applications. Sources of green materials with successful examples and other key parameters that determine the functionalities of AuNPs are also discussed in this review.

Gold nanoparticles and angiogenesis: molecular mechanisms and biomedical applications

Angiogenesis is the formation of new blood vessels from pre-existing vessels. It is a highly regulated process as determined by the interplay between pro-angiogenic and anti-angiogenic factors. Under certain conditions the balance between angiogenesis stimulators and inhibitors is altered, which results in a shift from physiological to pathological angiogenesis. Therefore, the goal of therapeutic targeting of angiogenic process is to normalize vasculature in target tissues by enhancing angiogenesis in disease conditions of reduced vascularity and blood flow, such as tissue ischemia, or alternatively to inhibit excessive and abnormal angiogenesis in disorders like cancer. Gold nanoparticles (AuNPs) are special particles that are generated by nanotechnology and composed of an inorganic core containing gold which is encircled by an organic monolayer. The ability of AuNPs to alter vasculature has captured recent attention in medical literature as potential therapeutic agents for the management of pathologic angiogenesis. This review provides an overview of the effects of AuNPs on angiogenesis and the molecular mechanisms and biomedical applications associated with their effects. In addition, the main synthesis methods, physical properties, uptake mechanisms, and toxicity of AuNPs are briefly summarized.

A polymyxin B-silver nanoparticle colloidal system and the application of lipopolysaccharide analysis

Polymyxin B (PMB) is a small cyclic polycationic lipopeptide, which can be used as an antibiotic drug against Gram-negative bacteria. In this work, the interaction between citrate capped silver nanoparticles (AgNPs) and PMB is studied. Experimental results show that the association constant is extremely high and the binding event leads to a significant variation in the localized surface plasmon resonance (LSPR) of AgNPs. Moreover, the PMB-AgNP colloidal system can be further exploited as a sensitive analytical platform. Taking lipopolysaccharide (LPS) as an example, we demonstrate a facile colorimetric LPS detection method. LPS is a major constituent of the Gram-negative bacterial cell wall which is used as an optimal biomarker for some diseases like urinary tract infections and sepsis. In this study, target LPS is able to tightly bind to PMB, which effectively inhibits the PMB induced aggregation of AgNPs. By monitoring the UV-vis absorption spectra, the LPS concentration can be quantitatively determined with high sensitivity. The sensing strategy is quite simple, which allows effortless diagnosis of many diseases at different stages.

Photocatalytic reduction of organic pollutant under visible light by green route synthesized gold nanoparticles

We report a rapid method of green chemistry approach for synthesis of gold nanoparticles (AuNPs) using Lagerstroemia speciosa leaf extract (LSE). L. speciosa plant extract is known for its effective treatment of diabetes and kidney related problems. The green synthesis of AuNPs was complete within 30min at 25°C. The same could also be achieved within 2min at a higher reaction temperature (80°C). Both UV-visible spectroscopy and transmission electron microscopy results suggest that the morphology and size distribution of AuNPs are dependent on the pH of gold solution, gold concentration, volume of LSE, and reaction time and temperature. Comparison between Fourier transform infrared spectroscopy (FT-IR) spectra of LSE and the synthesized AuNPs indicate an active role of polyphenolic functional groups (from gallotannins, lagerstroemin, and corosolic acid) in the green synthesis and capping of AuNPs. The green route synthesized AuNPs show strong photocatalytic activity in the reduction of dyes viz., methylene blue, methyl orange, bromophenol blue and bromocresol green, and 4-nitrophenol under visible light in the presence of NaBH₄. The non-toxic and cost effective LSE mediated AuNPs synthesis proposed in this study is extremely rapid compared to the other reported methods that require hours to days for complete synthesis of AuNPs using various plant extracts. Strong and stable photocatalytic behavior makes AuNPs attractive in environmental applications, particularly in the reduction of organic pollutants in wastewater.

Recent advances in plant-mediated engineered gold nanoparticles and their application in biological system

For biosynthesis of gold nanoparticles different parts of a plant are used as they contain metabolites such as alkaloids, flavonoids, phenols, terpenoids, alcohols, sugars and proteins which act as reducing agents to produce nanoparticles. They also act as capping agent and stabilizer for them. They are used in medicine, agriculture and many other technologies. The attention is therefore focussed on all plant species which have either aroma or colour in their leaves, flowers or roots for the synthesis of nanoparticles because they all contain such chemicals which reduce the metal ions to metal nanoparticles. The size and morphology of gold nanoparticles is dependent on the biogenic-synthetic route, incubation time, temperature, concentration and pH of the solution. In this review, we have discussed the latest developments for the fabrication of gold nanoparticles from herbal extract, their characterization by UV-vis., Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, atomic force microscopy, energy-dispersive X-ray spectroscopy, dynamic light scattering and Zeta Potential techniques. Their application in drug delivery, cancer treatment, catalysis and as antimicrobial agent has also been discussed.

Facile synthesis of D–π–A structured dyes and their applications towards the cost effective fabrication of solar cells as well as sensing of hazardous Hg(ii)

Synthesis of two D–π–A dyes with a multidisciplinary application approach explained on the basis of electron sharing effects.

Rapid Biosynthesis of Gold Nanoparticles by the Extracellular Secretion ofBacillus niabensis45: Characterization and Antibiofilm Activity

The present study demonstrated that the extracellular biosynthesis of gold nanoparticles (GNPs) usingB. niabensis45 may be mediated by a cyclic peptide (P2). The molecular weight of P2 was determined to be about 1122 Da by MALDI-TOF-MS and ESI-MS. A novel protocol for rapid biosynthesis of GNPs using P2 was developed. The results showed that GNP synthesis could be completed in a wide range of temperatures (40–100°C) and pH (6.0–10.0) within few minutes when 9 mL of P2 (2 mg/mL) and 1 mL of HAuCl4solution (2 mM) were mixed together. The synthesized GNPs were further characterized. Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) analysis confirmed the presence of elemental gold and crystalline structure of the GNPs, respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed the formation of spherical metallic GNPs. The size distribution of GNPs calculated using ImageJ software was found to be 10–20 nm. And these GNPs showed excellent antibiofilm activity againstPseudomonas aeruginosaPAO1 andStaphylococcus aureusATCC25923. The results revealed microbial cyclic peptides could be used as synthesis of GNPs which had potent antibiofilm potential.