Enhancement of secondary metabolites in Bacopa monnieri (L.) Pennell plants treated with copper-based nanoparticles in vivo

The study aims to document the effect of starch-stabilised copper-based nanoparticles (CuNPs) on the biosynthesis of pharmaceutically valuable secondary metabolites, especially saponins, of the reputed nootropic herb Bacopa monnieri (L.) Pennell. CuNPs were synthesised chemically by the reduction of cupric sulphate pentahydrate with ascorbic acid using starch as the capping agent. They were characterised by UV-visible spectrophotometry, Fourier-transform infra-red spectroscopy, X-ray diffraction, high-resolution transmission electron microscopy and zeta potential. The nanoparticles consisted of cuprous oxide and metallic copper, were approximately spherical, polydispersed with diameter <20 nm. Hydroponically grown B. monnieri plants were treated in vivo with the CuNPs between the concentrations of 0-100 mg l-1. Spectrophotometric estimation of the total contents of saponins, alkaloids, phenolics, flavonoids and DPPH radical scavenging capacity from the methanolic extracts of the whole plants showed a hormetic increase in the content of secondary metabolites in a concentration-dependent manner from 5 mg l-1 until it declined at toxic metabolic concentration. This was accompanied by an increase in ROS markers hydrogen peroxide and malondialdehyde as well as a hormetic effect on activities of phenylalanine ammonia lyase and antioxidant enzymes catalase, ascorbate peroxidase and superoxide dismutase. CuNPs at sub-toxic concentrations were found to enhance secondary metabolism and antioxidant capacity in Bacopa monnieri through ROS-mediated defence response.

Efficacy of mycosynthesised AgNPs from Earliella scabrosa as an in vitro antibacterial and wound healing agent

The silver nanoparticles (AgNPs) with their unique chemical and physical properties are proving as a new therapeutical agent. In the present study, the AgNPs synthesised from an aqueous extract of a macrofungus, Earliella scabrosa, were characterised by field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX), high-resolution transmission electron microscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and further evaluate for its in vitro antibacterial and wound healing efficacy. The mycosynthesised AgNPs exhibited the surface plasmon resonance peak at 410 nm with good stability over a period of a month. The FESEM and EDX analyses revealed the spherical-shaped AgNPs of an average size of 20 nm and the presence of elemental Ag, respectively. The XRD pattern showed the crystalline nature of AgNPs. The FTIR spectra confirmed the conversion of Ag+ ions to AgNPs due to reduction by biomolecules of macrofungus extract. The mycosynthesised AgNPs showed effective antibacterial activity against two Gram-positive bacteria, namely Bacillus subtilis and Staphylococcus aureus, and two Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa. The pathogens were highly sensitive to AgNPs, whereas less sensitive to AgNO3. The mycosynthesised AgNPs showed significant wound healing potential with 68.58% of wound closure.

Unraveling High-Yield Phase-Transition Dynamics in Transition Metal Dichalcogenides on Metallic Substrates

2D transition metal dichalcogenides (2D-TMDs) and their unique polymorphic features such as the semiconducting 1H and quasi-metallic 1T' phases exhibit intriguing optical and electronic properties, which can be used in novel electronic and photonic device applications. With the favorable quasi-metallic nature of 1T'-phase 2D-TMDs, the 1H-to-1T' phase engineering processes are an immensely vital discipline exploited for novel device applications. Here, a high-yield 1H-to-1T' phase transition of monolayer-MoS2 on Cu and monolayer-WSe2 on Au via an annealing-based process is reported. A comprehensive experimental and first-principles study is performed to unravel the underlying mechanism and derive the general trends for the high-yield phase transition process of 2D-TMDs on metallic substrates. While each 2D-TMD possesses different intrinsic 1H-1T' energy barriers, the option of metallic substrates with higher chemical reactivity plays a significantly pivotal role in enhancing the 1H-1T' phase transition yield. The yield increase is achieved via the enhancement of the interfacial hybridizations by the means of increased interfacial binding energy, larger charge transfer, shorter interfacial spacing, and weaker bond strength. Fundamentally, this study opens up the field of 2D-TMD/metal-like systems to further scientific investigation and research, thereby creating new possibilities for 2D-TMDs-based device applications.

Facile one‐pot hydrothermal synthesis of stable and biocompatible fluorescent carbon dots from lemon grass herb

Luminescent carbon‐based nanomaterials hold great promise due to their stable photo‐physical behaviour, biocompatibility and lower toxicity. This work involves economic and facile one‐pot green synthesis of water‐soluble nanostructures from lemon grass (LGNS) [Cymbopogon citratus (DC) Stapf ] as carbon source. High‐resolution transmission electron microscopy confirmed the formation of LGNS with lattice spacing of 0.23 nm matching low‐dimensional graphitic structures. The strong absorption exhibited at 278 nm could be attributed to л‐states of sp2 /sp3 hybridisation in carbon nanostructures. Fluorescence spectroscopy of LGNS exhibited strong excitation‐dependent emission properties over a broad range of wavelengths from 300 to 600 nm. Quantitatively, these LGNS were estimated to have quantum yield of 23.3%. Biomass derived LGNS could be potentially exploited for wide variety of applications like bioimaging, up‐conversion, drug delivery and optoelectronic devices. To this extent, synthesised LGNS were used to image yeast cells via multicolour/multi‐excitation fluorescence imaging.

Optical detection of CA 15.3 breast cancer antigen using CdS quantum dot

The present study focus on optical sensing of breast cancer antigen 15.3 (CA 15.3) using cadmium sulphide quantum dot (CdS-QD) in saline and serum samples spiked with antigen. The surface of CdS-QD was modified by cysteamine capping followed by tagging of CA 15.3 antibody. The samples were characterised using UV-visible absorption spectroscopy (UV-VIS Spectroscopy), Fourier transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HRTEM) attached with energy-dispersive X-ray spectroscopy, phase contrast inverted epi-fluorescence microscopy and photoluminescence (PL) spectrophotometry (EDS). The CdS-QD showed a mean diameter of 3.02 ± 0.6 nm. The complex formed after antigen-antibody interaction resulted in distinguishable optical and fluorescence intensity with respect to varying concentration of antigen. The PL study revealed that CA 15.3 antibody labelled CdS QD can detect CA 15.3 tumour marker even at very low concentration of 0.002 KU/L with a constant response time of 15 min. This study clearly indicates that detection of CA 15.3 at low concentration is possible using surface modified CdS QD in serum samples and can find immense applications in biosensor development for detection of breast cancer marker similar to various automated detection kits available in market.

Size dependent effects of antifungal phytogenic silver nanoparticles on germination, growth and biochemical parameters of rice (Oryza sativa L), maize (Zea mays L) and peanut (Arachis hypogaea L)

Advancement in materials synthesis largely depends up on their diverse applications and commercialisation. Antifungal effects of phytogenic silver nanoparticles (AgNPs) were evident, but the reports on the effects of the same on agricultural crops are scant. Herein, we report for the first time, size dependent effects of phytogenic AgNPs (synthesised using Stevia rebaudiana leaf extract) on the germination, growth and biochemical parameters of three important agricultural crops viz., rice (Oryza sativa L), maize (Zea mays L) and peanut (Arachis hypogaea L). AgNPs with varied sizes were prepared by changing the concentration and quantity of the Stevia rebaudiana leaf extract. As prepared AgNPs were characterized using the techniques, such as high-resolution transmission electron microscopy, particle size and zeta potential analyser. The measured (dynamic light scattering technique) average sizes of particles are ranging from 68.5 to 116 nm. Fourier transform infrared studies confirmed the participation of alcohols, aldehydes and amides in the reduction and stabilisation of the AgNPs. Application of these AgNPs to three agricultural crop seeds (rice, maize and peanut) resulted in size dependent effects on their germination, growth and biochemical parameters such as, chlorophyll content, carotenoid and protein content. Further, antifungal activity of AgNPs also evaluated against fungi, Aspergillus niger.

Postprandial anti-hyperglycemic activity of marine Streptomyces coelicoflavus SRBVIT13 mediated gold nanoparticles in streptozotocin induced diabetic male albino Wister rats

The present study focuses on the biosynthesis of gold nanoparticles (AuNPs) using Streptomyces coelicoflavus (S. coelicoflavus) SRBVIT13 isolated from marine salt pan soils collected from Ongole, Andhra Pradesh, India. The biosynthesised AuNPs are characterised by UV-visible spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, high-resolution transmission electron microscopy and energy-dispersive X-ray analysis. Transmission electron microscopy study suggests that the biosynthesised AuNPs are spherical in shape within a size range of 12-20 nm (mean diameter as 14 nm). The anti-type II diabetes activity of AuNPs is carried out by testing it in vitro α-glucosidase and α-amylase enzyme inhibition activity and in vivo postprandial anti-hyperglycemic activity in sucrose and glucose-loaded streptozotocin induced diabetic albino Wister rats. AuNPs has shown a significant inhibitory activity of 84.70 and 87.82% with IC50 values of 67.65 and 65.59 μg/mL to α-glucosidase and α-amylase enzymes, while the diabetic rats have shown significant reduction in the post postprandial blood glucose level by 57.80 and 88.09%, respectively compared with control group after AuNPs treatment at the concentration of 300 and 600 mg/kg body weight. Hence, this biosynthesised AuNPs might be useful in combating type II diabetes mellitus for the betterment of human life.