Seed Priming with MeJa Prevents Salt-Induced Growth Inhibition and Oxidative Damage in Sorghum bicolor by Inducing the Expression of Jasmonic Acid Biosynthesis Genes.

Salinity is one of the major detrimental abiotic stresses at the forefront of deterring crop productivity globally. Although the exogenous application of phytohormones has formerly proven efficacious to plants, their effect on the moderately stress-tolerant crop "Sorghum bicolor" remains elusive. To investigate this, S. bicolor seeds primed with methyl jasmonate (0; 10 and 15 µM MeJa) were exposed to salt (200 mM NaCl) stress, and their morpho-physiological, biochemical, and molecular attributes were measured. Salt stress significantly decreased shoot length and fresh weight by 50%, whereas dry weight and chlorophyll content were decreased by more than 40%. Furthermore, salt-stress-induced oxidative damage was evident by the formation of brown formazan spots (indicative of H2O2 production) on sorghum leaves and a more than 30% increase in MDA content. However, priming with MeJa improved growth, increased chlorophyll content, and prevented oxidative damage under salt stress. While 15 µM MeJa maintained proline content to the same level as the salt-stressed samples, total soluble sugars were maintained under 10 µM MeJa, indicating a high degree of osmotic adjustment. Shriveling and thinning of the epidermis and xylem tissues due to salt stress was prevented by MeJa, followed by a more than 70% decrease in the Na+/K+ ratio. MeJa also reversed the FTIR spectral shifts observed for salt-stressed plants. Furthermore, salt stress induced the expression of the jasmonic acid biosynthesis genes; linoleate 92-lipoxygenase 3, allene oxide synthase 1, allene oxide cyclase, and 12-oxophytodienoate reductase 1. In MeJa-primed plants, their expression was reduced, except for the 12-oxophytodienoate reductase 1 transcript, which further increased by 67%. These findings suggest that MeJa conferred salt-stress tolerance to S. bicolor through osmoregulation and synthesis of JA-related metabolites.

Functionalities of electrochemical fluoroquinolone sensors and biosensors.

Fluoroquinolones (FQs) are a class of broad-spectrum antimicrobial agents that are used to treat variety of infectious diseases. This class of antibiotics was being used for patients exhibiting early symptoms of a human respiratory disease known as the COVID-19 virus. As a result, this outbreak causes an increase in drug-resistant strains and environmental pollution, both of which pose serious threats to biota and human health. Thus, to ensure public health and prevent antimicrobial resistance, it is crucial to develop effective detection methods for FQs determination in water bodies even at trace levels. Due to their characteristics like specificity, selectivity, sensitivity, and low detection limits, electrochemical biosensors are promising future platforms for quick and on-site monitoring of FQs residues in a variety of samples when compared to conventional detection techniques. Despite their excellent properties, biosensor stability continues to be a problem even today. However, the integration of nanomaterials (NMs) could improve biocompatibility, stability, sensitivity, and speed of response in biosensors. This review concentrated on recent developments and contemporary methods in FQs biosensors. Furthermore, a variety of modification materials on the electrode surface are discussed. We also pay more attention to the practical applications of electrochemical biosensors for FQs detection. In addition, the existing challenges, outlook, and promising future perspectives in this field have been proposed. We hope that this review can serve as a bedrock for future researchers and provide new ideas for the development of electrochemical biosensors for antibiotics detection in the future.

Quantum Dot-Sensitised Estrogen Receptor-α-Based Biosensor for 17ß-Estradiol.

17ß-estradiol (E2) is an important natural female hormone that is also classified as an estrogenic endocrine-disrupting compound (e-EDC). It is, however, known to cause more damaging health effects compared to other e-EDCs. Environmental water systems are commonly contaminated with E2 that originates from domestic effluents. The determination of the level of E2 is thus very crucial in both wastewater treatment and in the aspect of environmental pollution management. In this work, an inherent and strong affinity of the estrogen receptor-α (ER-α) for E2 was used as a basis for the development of a biosensor that was highly selective towards E2 determination. A gold disk electrode (AuE) was functionalised with a 3-mercaptopropionic acid-capped tin selenide (SnSe-3MPA) quantum dot to produce a SnSe-3MPA/AuE electroactive sensor platform. The ER-α-based biosensor (ER-α/SnSe-3MPA/AuE) for E2 was produced by the amide chemistry of carboxyl functional groups of SnSe-3MPA quantum dots and the primary amines of ER-α. The ER-α/SnSe-3MPA/AuE receptor-based biosensor exhibited a formal potential (E0') value of 217 ± 12 mV, assigned as the redox potential for monitoring the E2 response using square-wave voltammetry (SWV). The response parameters of the receptor-based biosensor for E2 include a dynamic linear range (DLR) value of 1.0-8.0 nM (R2 = 0.99), a limit of detection (LOD) value of 1.69 nM (S/N = 3), and a sensitivity of 0.04 µA/nM. The biosensor exhibited high selectivity for E2 and good recoveries for E2 determination in milk samples.

Biodegradable water hyacinth cellulose-graft-poly(ammonium acrylate-co-acrylic acid) polymer hydrogel for potential agricultural application.

Swollen cellulose fibres isolated from water hyacinth were utilized in the synthesis of water hyacinth cellulose-graft-poly(ammonium acrylate-co-acrylic acid) polymer hydrogel (PHG). Acrylic acid (AA) partially neutralized with NH3 was heterogeneously grafted onto swollen cellulose by radical polymerization reaction using N,N-methylene-bis-acrylamide (MBA) as the cross-linker and ammonium persulphate (APS) as the initiator. The reaction conditions were optimized through assessment of grafting parameters such as grafting cross-linking percentage (GCP), percentage grafting cross-linking efficiency (%GCE) and water absorption tests. Characterization of the copolymer by Fourier Transform Infra-red (FTIR) spectroscopy revealed successful grafting of the monomer onto cellulose. Transmission electron microscopy (TEM) image of acetone-extracted PHG displayed micro-porous structure. The optimized product swelled in distilled water up to 165 times its own dry weight. The swelling was influenced by the pH and presence, nature and concentration of ions. The hydrogel had the capacity to retain moisture in soil, and degradation testing revealed a higher mass loss in cellulose grafted copolymer compared to the copolymer without cellulose. Degradation by soil microbial isolates showed significantly higher (P ≤ 0.05) accumulation of NH4 + in the cellulose grafted copolymer up to 0.05% (w/v) from 40 to 100 h, relative to similar amounts of copolymer without cellulose. The use of water hyacinth, a notorious weed in Kenyan waters, to produce cellulose-based polymer hydrogels has not been explored and yet, it could form an effective and beneficial way of utilizing this plant. A mechanism of graft polymerization reaction has also been proposed. The synthesized product can be applied in agriculture and other fields where biodegradability and effective utilization of water is essential.

Tyrosinase based amperometric biosensor for determination of tyramine in fermented food and beverages with gold nanoparticle doped poly(8-anilino-1-naphthalene sulphonic acid) modified electrode.

The aim of the present work was to develop an amperometric biosensor for tyramine (Tyr) measurement in food and beverages. The biosensor architecture is based on tyrosinase (Tyrase) immobilization on glassy carbon electrode modified by a nanocomposite consisting of gold nanoparticles (AuNP) synthesized by a green method and poly(8-anilino-1-naphthalene sulphonic acid) modified glassy carbon electrode. Under optimized experimental conditions for fixed potential amperometric detection, the biosensor exhibited a linear response to tyramine in the range 10-120 µM and the limit of detection was estimated to be 0.71 µM. The novel platform showed good selectivity, long-term stability, and reproducibility. The strong interaction between tyrosinase and the nanocomposite was revealed by the high value of the Michaelis-Menten constant (79.3 µM). The fabricated biosensor was successfully applied to the determination of Tyr in dairy products and fermented drinks with good recoveries, which makes it a promising biosensor for quantification of tyramine.

Impedimetric sensor for tyramine based on gold nanoparticle doped-poly(8-anilino-1-naphthalene sulphonic acid) modified gold electrodes.

A novel impedimetric sensor for the determination of tyramine (Tyr), a biogenic amine, on the surface of gold nanoparticle-poly-(8-anilino-1-napthalene sulphonic acid), AuNP-PANSA modified gold electrode (AuE) is presented for the first time. The AuNP were successfully synthesized by a green synthesis method. Their characterization and optimization were conducted using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetry. Under optimal conditions, the impedimetric sensor revealed a relatively broad linear range from 0.8 to 80 µM similar to more complex architectures found in the literature and the limit of detection of 0.04 µM was the lowest achieved until now. In order to test the reliability of the proposed method, real sample application studies were conducted using dairy products and fermented drinks. It was found that the sensor presented a good selectivity and recovery. Furthermore, the impedimetric sensor shows good reproducibility, stability, selectivity and very small interferences which augur well for its application in food safety control processes.