Krishna Pal Singh

Current trends in nanomaterial embedded field effect transistor-based biosensor

Recently, as metal-, polymer-, and carbon-based biocompatible nanomaterials have been increasingly incorporated into biosensing applications, with various nanostructures having been used to increase the efficacy and sensitivity of most of the detecting devices, including field effect transistor (FET)-based devices. These nanomaterial-based methods also became the ideal for the amalgamation of biomolecules, especially for the fabrication of ultrasensitive, low-cost, and robust FET-based biosensors; these are categorically very successful at binding the target specified entities in the confined gated micro-region for high functionality. Furthermore, the contemplation of nanomaterial-based FET biosensors to various applications encompasses the desire for detection of many targets with high selectivity, and specificity. We assess how such devices have empowered the achievement of elevated biosensor performance in terms of high sensitivity, selectivity and low detection limits. We review the recent literature here to illustrate the diversity of FET-based biosensors, based on various kinds of nanomaterials in different applications and sum up that graphene or its assisted composite based FET devices are comparatively more efficient and sensitive with highest signal to noise ratio. Lastly, the future prospects and limitations of the field are also discussed.

Foliar Application of Plant Growth-Promoting Rhizobacteria Increases Antifungal Compounds in Pea (Pisum sativum) Against Erysiphe pisi

Systemic effect of two plant growth-promoting rhizobaeterial (PGPR) strains, viz., Pseudomonas fluorescens (Pf4) and P. aeruginosa (Pag), was evaluated on pea (Pisum sativum) against the powdery mildew pathogen Erysiphe pisi Foliar spray of the two PGPR strains was done on specific nodal leaves of pea and conidial germination of E. pisi was observed on other nodal leaves, distal to the treated ones. Conidial germination was reduced on distant leaves and at the same time, specific as well as total phenolic compounds increased in the leaves distal to those applied with PGPR strains, thereby indicating a positive correlation. The strains induced accumulation of phenolic compounds in pea leaves and the amount increased when such leaves were get inoculated with E. pisi conidia. Between the two strains, Pag was found to be more effective than Pf4 as its effect was more persistent in pea leaves. Foliar application of PGPR strains for the control of powdery mildew of pea is demonstrated in vitro while correlating it with the increased accumulation of plant phenolics.

Water quality evaluation of Himalayan Rivers of Kumaun region, Uttarakhand, India

Water quality of Himalayan rivers has been steadily deteriorating over several decades due to anthropogenic activities, dumping of treated or untreated effluents, poor structured sewerage and drainage system, etc. In the present study, the water quality of five important rivers namely, Gola, Kosi, Ramganga, Saryu and Lohawati rivers were investigated which flow through the different districts of Kumaun region of Uttarakhand Himalaya. The water of all these rivers serves as the major source for drinking and irrigation purposes in these districts of the Kumaun region of Uttarakhand. River water samples collected in pre-monsoon and post-monsoon seasons of the years 2011 and 2012 were analyzed for various water quality characteristics. Statistical analyses indicate positive correlation among most of the chemical parameters. Piper diagram illustrates that all the water samples fall in Ca–Mg–HCO3 hydrochemical facies, Moreover, the suitability of water for drinking purposes determined by water quality index indicated that river water in both the seasons is unsuitable. Irrigation water quality of all the river water was found suitable during both the seasons according to the result of sodium adsorption ratio, sodium percentage and residual sodium carbonate. The present study revealed that major factors contributing to deterioration of water quality of all the rivers might be eutrophication, tourism, anthropogenic and geogenic processes. Therefore, to restore the vitality and water quality of all these rivers, proper water resource planning programme should be developed.

Applying graphene oxide nano-film over a polycarbonate nanoporous membrane to monitor E. coli by infrared spectroscopy.

Nano-biosensors are excellent monitoring tools for rapid, specific, sensitive, inexpensive, in-field, on-line, and/or real-time detection of pathogens in foods, soil, air, and water samples. A variety of nano-materials (metallic, polymeric, and/or carbon-based) were employed to enhance the efficacy, efficiency, and sensitivity of these nano-biosensors, including graphene-based materials, especially graphene oxide (GO)-based materials. GO bears many oxygen-bearing groups, enabling ligand conjugation at the high density critical for sensitive detection. We have fabricated GO-modified nano-porous polycarbonate track-etched (PCTE) membranes that were conjugated to an Escherichia coli-specific antibody (Ab) and used to detect E. coli. The random distribution of nanopores on the PCTE membrane surface and the bright coating of the GO onto the membrane were confirmed by scanning electron microscope. Anti-E. coli β-gal Abs were conjugated to the GO surface via 1-ethyl-3,3-dimethylaminopropyl carbodiimide hydrochloride-N-hydroxysuccinimide chemistry; antibody coating was confirmed by the presence of a characteristic IR peak near 1600cm(-1). A non-corresponding Ab (anti-Pseudomonas) was used as a negative control under identical conditions. When E. coli interacted anti-E.coli β-gal with Ab-coated GO-nano-biosensor units, we observed a clear shift in the IR peak from 3373.14 to 3315cm(-1); in contrast, we did not observe any shift in IR peaks when the GO unit was coated with the non-corresponding Ab (anti-Pseudomonas). Therefore, the detection of E. coli using the described GO-nano-sensor unit is highly specific, is highly selective and can be applied for real-time monitoring of E. coli with a detection limit between 100μg/mL and 10μg/mL, similar to existing detection systems.

Selective Recognition and Detoxification of Deltamethrin Using Molecularly Imprinted Polymer (MIP) Matrices

Stability of natural antibodies, peptides and enzymes as molecular recognition elements in chemical and biological sensors has been facing threat due to their lack of stability, complicated ethical issues, time taking processes and signal transduction mechanisms limits. Molecularly imprinted polymers (MIPs) with recent advancements have created synthetic materials that can mimic the function of chemical and biological receptors but with less stability constraints, quick synthesis and with no ethical issues. These polymers can provide high sensitivity and selectivity while maintaining excellent thermal and mechanical stability. In the present study molecularly imprinted polymer matrix has been fabricated for the specific recognition of pesticide Deltamethrin, which is being used widely to control insects in crop management system. The composite membranes have been prepared by using methacrylic acid (MAA) as functional monomer, selected by electrostatic interactions based computational simulation and ethylene glycol dimethacrylate (EGDMA) as cross linker. The garbing of deltamethrin MIP on membrane matrix was confirmed by the UV-VIS spectrophotometer, FTIR and Scanning Electron Microscopy (SEM). The detoxification and separation of Deltamethrin was done using a solid phase extraction (SPE) and a specially designed membrane syringe holder, which could separate and detect the herbicide up to a very sensible limit, 20 µg/ml.

Determination of E. coli by a Graphene Oxide-Modified Quartz Crystal Microbalance

ABSTRACT A biosensor for the determination of Escherichia coli using graphene oxide on the crystal (gold) surface was fabricated by the drop cast method. The E. coli sensing characteristics of the biosensor, such as a change in frequency, were examined by exposing the graphene oxide-coated crystal to various functionalization steps at room temperature. Graphene oxide was functionalized by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride–N-hydroxysuccinimide to covalently conjugate β-galactosidase antibodies to recognize microorganisms that produce this material. Frequency changes in the quartz crystal microbalance are dependent on the absorbed/desorbed masses of the analytes on the functional surface of the crystal. In addition, various characterization techniques were optimized for the morphological elemental analysis of the nanocoating that included field emission scanning electron microscopy, scanning electron microscopy, and electron diffraction spectroscopy. This surface was used in a quartz crystal microbalance nanoplatform for the rapid, sensitive, and label-free detection of E. coli. Under optimal conditions, the frequency of quartz crystal microbalance biosensor was directly proportional to the concentration of antigen with a dynamic range from 0.5 mg mL−1 to 5 ng mL−1 and a minimum detection limit of 5 ng mL−1, and a sensitivity of 0.037 Hz g ml−1 cm−1. These results show that the graphene oxide-coated crystal had excellent performance for E. coli. This research reports a simple, inexpensive, and effective highly stable biosensor using graphene oxide as the sensing medium.

Graphene Oxide-Polycarbonate Track-Etched Nanosieve Platform for Sensitive Detection of Human Immunodeficiency Virus Envelope Glycoprotein

Solid-state nanopores within graphene-based materials are on the brink of fundamentally changing the sensing of desired bioanalytes through ion trafficking across nanoporous membranes. Here, we report on a two-electrode electrochemical biosensor comprised of a graphene oxide-polycarbonate track-etched nanosieve platform for the rapid and sensitive detection of the Human Immunodeficiency Virus Type 1 (HIV-1) envelope glycoprotein ectodomain (gp140MS). We have covalently linked an engineered high-affinity one-domain soluble CD4 fused to a human domain targeting HIV-1 coreceptor binding site and ferrocene (Fc) (2Dm2m) to the nanosieve platform. An exponential decrease in the ionic current resulted from a partial blockade of the nanosieve due to the specific interactions of gp140MS with the 2Dm2m protein, which was immobilized on the nanosieve platform by biolinkage as a function of applied voltages of 0.1-2.0 V. There was no change in current when a nonspecific antigen bovine serum albumin was tested under identical conditions. This platform had high sensitivity, and when the receptor-binding phenomenon was tested to identify the minimum concentration of target analyte, the lowest detection limit was as short as 8.3 fM and with sensitivity and response times of 0.87 mA mM-1 cm-1 and 12 s, respectively. In addition to this remarkable sensitivity, our nanobiorecognition platform has the advantage of superior stability due to the few layered graphene oxide laminates. It also exhibits exceptional biomolecule binding and higher reusability, sustainability, and ease of fabrication in a soft mechanism. Real samples of HIV positive and negative patients were successfully tested to confirm the virus by the developed platform. To the best of our knowledge, this is the first time prosperous pervious remembrance surface has been employed in a nanobiosensing application. In light of the recent great trend of using graphene-based nanopore surfaces created by sophisticated ion-beam methods in sensing and sequencing, this hybrid-surface nanolayer fabricated by the simple vacuum filtration of a few layered graphene oxide laminates may serve as a good alternative in terms of ease of fabrication without expensive instrumental prerequisites.

Functional and structural insights into candidate genes associated with nitrogen and phosphorus nutrition in wheat ( Triticum aestivum L.)

An extensive bioinformatics based study has been performed to gain insight into the structural and functional aspects of candidate genes involved in Nitrogen and Phosphorus nutrition in wheat. Based on our study, 37 N and P nutrition candidate genes were identified (24 NUE and 13 inorganic phosphate transporters) in wheat genome. 23 gene specific novel microsatellites were discovered using genomic sequences of identified N and P nutrition genes. We also identified the microRNAs that target ten candidate genes including TaAS1-3A, TaAS1-3D, TaASN2-1A, TaASN2-1B, TaANR1-6A, TaANR1-6B, TaNRT2.4-6A, TaNRT2.6-6A, TaNRT2.6-6B and TaPHT1.5-5B. Expression profiling of identified genes showed altered expression under N and P starvation. The proposed 3D structure of wheat N and P nutrition proteins shared high level homology with known experimental structures providing information to understand their functions at the biochemical level. Molecular dynamics simulations of refined modeled structures of wheat N and P nutrition proteins show conformational stability. The identified N and P nutrition candidate genes and their targeting miRNAs may provide resources for the genetic improvement and promote N and P use efficiency. Our study provides first-hand structural prospective of N and P nutrition candidate genes towards development of wheat varieties resilient to N and P stress.

­­­ A web resource for nutrient use efficiency-related genes, quantitative trait loci and microRNAs in important cereals and model plants

Cereals are key contributors to global food security. Genes involved in the uptake (transport), assimilation and utilization of macro- and micronutrients are responsible for the presence of these nutrients in grain and straw. Although many genomic databases for cereals are available, there is currently no cohesive web resource of manually curated nutrient use efficiency (NtUE)-related genes and quantitative trait loci (QTLs). In this study, we present a web-resource containing information on NtUE-related genes/QTLs and the corresponding available microRNAs for some of these genes in four major cereal crops (wheat ( Triticum aestivum), rice ( Oryza sativa), maize ( Zea mays), barley ( Hordeum vulgare)), two alien species related to wheat ( Triticum urartu and Aegilops tauschii), and two model species ( Brachypodium distachyon and Arabidopsis thaliana). Gene annotations integrated in the current web resource were manually curated from the existing databases and the available literature. The primary goal of developing this web resource is to provide descriptions of the NtUE-related genes and their functional annotation. MicroRNAs targeting some of the NtUE related genes and the QTLs for NtUE-related traits are also included. The genomic information embedded in the web resource should help users to search for the desired information.

Metabolite profiling can assist variability analysis in Trichoderma species

Variability in 41 isolates of Trichoderma belonging to 21 species was observed in the phenolic acid profile of their culture filtrates. The phenolic acid profiles were observed to be very stable in the culture filtrate of Trichoderma species. The similarity in phenolic acid profile was recorded and based on it the species were grouped into three distinct groups, viz. highly similar, moderately similar and least similar. Of the 21 species, seven species showed highly similar trend, whereas two and four species showed moderate and least similarity in their phenolic acid profiles, respectively. Looking into the stability of phenolic acid profile in the culture filtrate of the Trichoderma species the present tool may help in diversity analysis in Trichoderma species originating from different geographical areas.