Photo-Driven Synthesis of Anisotropic Gold Nanoparticles Using Silk Fibroin—Cell Viability Activities in Lymphocyte and Jurkat Cancer Cells

Microwave-Assisted Biosynthesis of Quercetin-Stabilized Gold Nanoparticles with Enhanced Antibacterial and Catalytic Properties

In the past few years, substantial progress has been made in the field of microwave-assisted biosynthesis of gold nanoparticles (AuNPs) using quercetin (QT) as a natural reducing and stabilizing agent. This study explores the rapid and eco-friendly synthesis of AuNPs facilitated by microwave irradiation, offering a time-efficient alternative to conventional methods. The AuNPs were thoroughly characterized to confirm their morphology, size, crystalline structure, and surface plasmon resonance (SPR). The synthesized AuNPs were confirmed by visual color change from yellow to violet and characteristic SPR peak at 519 nm. Furthermore, XRD studies clearly confirmed the crystalline nature of the face-centered cubic structure of AuNPs. Moreover, TEM images reveal that the AuNPs were found to be more or less spherical and have a slightly variable morphology with an average diameter of 14 nm. The antibacterial properties of QT and AuNPs were evaluated against two different bacterial strains via Staphylococcus aureus and Escherichia coli, demonstrating significant activity, particularly due to the stabilizing effect of QT. Additionally, the catalytic efficiency of the AuNPs was evaluated by their ability to reduce 4-nitrophenol to 4-aminophenol, a model reaction for the catalytic activity. The results were promising, with the rate constant of QT-AuNPs determined to be 0.1016 s-1. This work highlights the dual functionality of QT-mediated AuNPs in enhancing both antimicrobial and catalytic properties, contributing to their potential applications in the biomedical and environmental fields. This study highlights the dual role of QT-mediated AuNPs in enhancing antimicrobial and catalytic properties, paving the way for innovative applications in both the biomedical and environmental fields. The uniqueness lies in leveraging the natural properties of QT to simultaneously improve biological activity and catalytic efficiency, offering a sustainable and multifunctional QT-AuNP solution.

Direct detection of melamine in milk via surface-enhanced Raman scattering using gold-silver anisotropic nanostructures

As the degree of anisotropy in nanoparticle morphology increases, the resulting electromagnetic enhancement can be significantly intensified. Herein, we have attempted to develop anisotropic gold-silver (a-AuAg) nanoparticles deposited on a titanium sheet (a-AuAg@Ti) as a highly efficient Surface-enhanced Raman Spectroscopy (SERS) sensor for rapid detection of health-hazardous milk adulterants like melamine. Hierarchical a-AuAg nanoparticles have been synthesized via a facile seed and growth-mediated method, followed by immobilization on a titanium sheet using a drop-casting technique. The structural, morphological, chemical, and optical properties of a-AuAg@Ti sensors have been systematically investigated and correlated with their respective SERS performance. Morphological analysis revealed the occurrence of triangular, hexagonal, and pentagonal-shaped nanoparticles with an average particle size of ∼ 23 to 26 nm. Preliminary SERS analysis using Rhodamine 6G (R6G) probe molecule revealed significantly higher SERS activity for a-AuAg nanoparticles compared to their spherical counterparts. This could be attributed to the lightning rod effect associated with the synthesized anisotropic nanostructures. An enhancement factor of 1.7 x 108 has been estimated for a-AuAg@Ti sensor with excellent signal reproducibility. Further, the efficacy of melamine detection has been investigated by spiking it into water and milk samples. The estimated lower detection limit (LDL) near picomolar and nanomolar concentrations have been obtained for melamine-spiked samples in water and milk, respectively. High-performance liquid chromatography analysis for melamine revealed an LDL of only 0.1 µM, indicating the higher sensitivity of a-AuAg@Ti SERS sensor. Moreover, we have also analyzed commercial milk products to verify the melamine contents, but none of them showed melamine-specific fingerprint bands. Our findings highlight the superior sensitivity of a-AuAg@Ti substrates for real-time melamine detection, making them excellent optical sensing tools for food safety analysis.

Facile engineering of aptamer-coupled silk fibroin encapsulated myogenic gold nanocomposites: investigation of antiproliferative activity and apoptosis induction

Nanocomposites selectively induce cancer cell death, holding potential for precise liver cancer treatment breakthroughs. This study assessed the cytotoxicity of gold nanocomposites (Au NCs) enclosed within silk fibroin (SF), aptamer (Ap), and the myogenic Talaromyces purpureogenus (TP) against a human liver cancer cell (HepG2). The ultimate product, Ap-SF-TP@Au NCs, results from a three-step process. This process involves the myogenic synthesis of TP@Au NCs derived from TP mycelial extract, encapsulation of SF on TP@Au NCs (SF-TP@Au NCs), and the conjugation of Ap within SF-TP@Au NCs. The synthesized NCs are analyzed by various characteristic techniques. Ap-SF-TP@Au NCs induced potential cell death in HepG2 cells but exhibited no cytotoxicity in non-cancerous cells (NIH3T3). The morphological changes in cells were examined through various biochemical staining methods. Thus, Ap-SF-TP@Au NCs emerge as a promising nanocomposite for treating diverse cancer cells.