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The aim of this research is to define optimal conditions to improve the stability of gold and silver nanoparticles' anti-zearalenone antibody conjugates for their utilisation in lateral flow immunochromatographic assay (LFIA). The Turkevich–Frens method was used to synthesise gold nanoparticles (AuNPs), which were between 10 and 110 nm in diameter. Silver nanoparticles (AgNPs) with a size distribution of 2.5 to 100 nm were synthesised using sodium borohydride as a reducing agent. The onset of AuNP and AgNP aggregation occurred at 150 mM and 80 mM NaCl concentrations, respectively. Stable Au and Ag nanoparticle–antibody conjugates were achieved at 1.2 mM of K2CO3 concentration, which corresponds to the pH value of ≈7. Lastly, the highest degree of conjugation between Au and Ag nanoparticles and anti-zearalenone antibodies was at 4 and 6 µg/mL of antibody concentrations. The optimisation of the conjugation conditions can contribute to better stability of nanoparticles and their antibody conjugate and can improve the reproducibility of results of bioreporter molecules in biosensing lateral flow devices. [ABSTRACT FROM AUTHOR]

Salmonella is a bacterial pathogen which is one of the leading causes of severe illnesses in humans. The current study involved the design and development of two methods, respectively using iron oxide nanoparticle (IONP) and iron core gold nanoparticle (ICGNP), conjugated with the Salmonella antibody and the fluorophore, 4-Methylumbelliferyl Caprylate (4-MUCAP), used as an indicator, for its selective and sensitive detection in contaminated food products. Twenty double-blind beverage samples, spiked with Salmonella enteritidis, Staphylococcus aureus, and Escherichia coli, were prepared in sterile Eppendorf® tubes at room temperature. The gold layer and spikes of ICGNPs increased the surface areas. The ratio of the surface area is 0.76 (IONPs/ICGNPs). The comparative sensitivity and specificity of the IONP-based and the ICGNP-based methods to detect Salmonella were determined. The ICGNP method shows the limit of detection is 32 Salmonella per mL. The ICGNPs had an 83.3% sensitivity and a 92.9% specificity value for the presence and detection of Salmonella. The IONP method resulted in a limit of detection of 150 Salmonella per mL, and a 66.7% sensitivity and 83.3% specificity for the presence and detection of Salmonella. The higher surface area of ICGNPs increases the efficiency of detection. The monitoring of Salmonella can thus be achieved by a rapid magnetic fluorescent assay using a smartphone for image capture and analyze, providing quantitative results. The findings from the present study would help to detect Salmonella rapidly in water. It can improve the microbial quality of water and food safety due to the presence of Salmonella in the water environment. [ABSTRACT FROM AUTHOR]

A critical understanding of the formation and growth process of gold nanoparticles (GNPs) is crucial, in order to synthesize monodisperse gold nanocrystals of controllable size and shape in a predictable way. GNPs of different shapes and sizes can be produced by altering different physicochemical reaction conditions, such as pH, temperature, and the ratio of reactants. The significant variations in the morphological features of GNPs can be monitored in situ in a time-dependent manner by using UV–visible spectroscopy. In this study, we have synthesized seedless GNPs by reduction of HAuCl 4 by using various molar ratios of HEPES and Na 2 HPO 4. The shape and the geometry of the gold nanostructures were optimized by varying the pH (5, 7, and 9) of the HEPES, molar concentrations of disodium phosphate to HAuCl 4, and reaction temperatures (20 °C, 40 °C, and 60 °C). The changes in the color of the reaction mixtures over time were recorded in situ in terms of the absorbance of the UV–visible light to tune and investigate the growth process of gold nanostructures. Transmission electron microscopic (TEM) images indicated that the gold nanostructures are anisotropic, stable, and exist in the size range of < 1–100 nm. The present study also confirms that the change in the color of nanostructure reaction mixtures is a function of the surface plasmon resonance bands under the influence of physicochemical reaction conditions and corroborates with the size and shape of nano-gold. Physicochemical parameters such as temperature, pH, and the molar concentration of the reactants act synergistically to influence the growth, molecular mechanics, and reaction thermodynamics that aid to affect the particle size, shape, and surface corona of the GNPs. By tracking the growth process, we can confirm that the nucleation, growth process, size, and shape of the gold nanostructures depend on the HEPES free radicals and phosphate ions which cluster to form polymeric chains on the gold nanocore. The present study's findings explain the growth process of the GNPs of various colors that can be observed by the naked eye and have promising applications, for example in the development of the biosensing rapid lateral flow immunoassays (LFIA) for the detection of mycotoxins in food samples. [Display omitted] [ABSTRACT FROM AUTHOR]

Glioblastoma multiforme (GBM) is the most aggressive and commonly diagnosed brain cancer and is highly resistant to routine chemotherapeutic drugs. The present study involves the synthesis of Lignin-g-p (NIPAM-co-DMAEMA) gold nanogel, loaded with curcumin and piperine, to treat GBM. The ongoing study has the application potential to (1) overcome the limitations of drugs biodistribution, (2) enhance the toxicity of anticancer drugs against GBM, and (3) identify the drugs uptake pathway. Atom transfer radical polymerization was used to synthesize the Lignin-g-PNIPAM network, crosslinked with the gold nanoparticles (GNPs) to self-assemble into nanogels. The size distribution and morphological analysis confirmed that the drug-loaded gold nanogels are spherical and exist in the size of 180 nm. The single and combinatorial toxicity effects of curcumin- and piperine-loaded Lignin-g-p (NIPAM-co-DMAEMA) gold nanogels were studied against U-251 MG GBM cells. A cytotoxicity analysis displayed anticancer properties. IC50 of curcumin- and piperine-loaded gold nanogels were recorded at 30 μM and 35 μM, respectively. Immunostaining and Western blot analysis confirmed the protein expression of caspase-3 and cleaved caspase-3 in cells treated with drug-loaded nanogels. Kinetic drug release revealed 86% release of hybrid curcumin–piperine from gold nanogel after 250 min at pH 4. Atomic absorption spectroscopic analysis confirmed that the drug-loaded nanogels have better internalization or association with the cancer cells than the GNPs or nano-gels alone. Morphological studies further confirmed that the curcumin and piperine nanogels penetrate the cells via endocytic pathways and induce caspase-3-related apoptosis. The experimental evidence shows the enhanced properties of combinatorial curcumin–piperine gold nanogels (IC50: 21 μM) to overcome the limitations of conventional chemotherapeutic treatments of glioma cells. [ABSTRACT FROM AUTHOR]