Peptide Nucleic Acid Immobilized Biocompatible Silane Nanocomposite Platform for Mycobacterium tuberculosis Detection

Surface-Initiated Reversible Addition-Fragmentation Chain Transfer Polymerization (SI-RAFT) to Produce Molecularly Imprinted Polymers on Graphene Oxide for Electrochemical Sensing of Methylparathion

A nonenzymatic redox-responsive sensor was put forward for the detection of methylparathion (MP) by designing globular nanostructures of molecularly imprinted polymers on graphene oxide (GO@MIPs) via surface-initiated reversible addition-fragmentation chain transfer polymerization (SI-RAFT). Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), and small-angle X-ray scattering (SAXS) studies have confirmed the successful formation of receptor layers of MIPs on RAFT agent-functionalized GO sheets. The electrochemical signal with an amplified current response was attained because of the enhanced diffusion rate of ions at the interface provided by widening the pore size of the MIP film. The analytical response of GO@MIPs, validated by recording square-wave anodic stripping voltammetry (SWASV) at varying MP concentrations, followed the linear response between 0.2 and 200 ng/mL. Under optimized conditions, the sensor exhibited a limit of detection of 4.25 ng/mL with high selectivity over other interfering ions or molecules. The anti-interfering ability and good recovery (%) in food samples directed the use of the proposed sensor toward real-time monitoring and also toward future mimicking of surfaces.

An insight to the recent advancements in detection of Mycobacterium tuberculosis using biosensors: A systematic review

Since ancient times, Tuberculosis (TB) has been a severe invasive illness that has been prevalent for thousands of years and is also known as "consumption" or phthisis. TB is the most common chronic lung bacterial illness in the world, killing over 2 million people each year, caused by Mycobacterium tuberculosis (MTB). As per the reports of WHO, in spite of technology advancements, the average rate of decline in global TB infections from 2000-2018 was only 1.6% per year, and the worldwide reduction in TB deaths was only 11%. In addition, COVID-19 pandemic has reversed years of global progress in tackling TB with fewer diagnosed cases. The majority of undiagnosed patients of TB are found in low- and middle-income countries where the GeneXpert MTB/RIF assay and sputum smear microscopy have been approved by the WHO as reference procedures for quickly detecting TB. Biosensors, like other cutting-edge technologies, have piqued researchers' interest since they offer a quick and accurate way to identify MTB. Modern integrated technologies allow for the rapid, low-cost, and highly precise detection of analytes in extremely little amounts of sample by biosensors. Here in this review, we outlined the severity of tuberculosis (TB) and the most recent developments in the biosensors sector, as well as their various kinds and benefits for TB detection. The review also emphasizes how widespread TB is and how it needs accurate diagnosis and effective treatment.

Road Map of Semiconductor Metal-Oxide-Based Sensors: A Review

Identifying disease biomarkers and detecting hazardous, explosive, flammable, and polluting gases and chemicals with extremely sensitive and selective sensor devices remains a challenging and time-consuming research challenge. Due to their exceptional characteristics, semiconducting metal oxides (SMOxs) have received a lot of attention in terms of the development of various types of sensors in recent years. The key performance indicators of SMOx-based sensors are their sensitivity, selectivity, recovery time, and steady response over time. SMOx-based sensors are discussed in this review based on their different properties. Surface properties of the functional material, such as its (nano)structure, morphology, and crystallinity, greatly influence sensor performance. A few examples of the complicated and poorly understood processes involved in SMOx sensing systems are adsorption and chemisorption, charge transfers, and oxygen migration. The future prospects of SMOx-based gas sensors, chemical sensors, and biological sensors are also discussed.

Biosensors for the detection of Mycobacterium tuberculosis: a comprehensive overview

Tuberculosis (TB) infection is one of the leading causes of death in the world. According to WHO reports 2019, the average rate of decrease in global TB incidences was only 1.6% per year from 2000 to 2018, besides that the global decline in TB deaths was just 11%. Therefore, the dire need for early detection of the pathogen for the successful diagnosis of TB seems justified. Mycobacterium tuberculosis secretory proteins have gained more attention as TB biomarkers, for the early diagnosis and treatment of TB. Here in this review, we elaborate on the recent advancements made in the field of piezoelectric, magnetic, optical, and electrochemical biosensors, in addition to listing their merits and setbacks. Additionally, this review also discusses the construction of biosensors through modern integrated technologies, such as combinations of analytical chemistry, molecular biology, and nanotechnology. Integrated technologies enhance the detection for perceiving highly selective, specific, and sensitive signals to detect M. tuberculosis. Furthermore, this review highlights the recent challenges and scope of improvement in numerous biosensors developed for rapid, specific, selective, and sensitive detection of tuberculosis to reduce the TB burden and successful treatment.

The overview and perspectives of biosensors and Mycobacterium tuberculosis: A systematic review

Tuberculosis (TB) is referred to as a "consumption" or phthisis, which has been a fatal human disease for thousands of years. Mycobacterium tuberculosis (M. tb) might have been responsible for the death of more humans than any other bacterial pathogens. Therefore, the rapid diagnosis of this bacterial infection plays a pivotal role in the timely and appropriate treatment of the patients, as well as the prevention of disease spread. More than 98% of TB cases are reported in developing countries, and due to the lack of well-equipped and specialized diagnostic laboratories, development of effective diagnostic methods based on biosensors is essential for this bacterium. In this review, original articles published in English were retrieved from multiple databases, such as PubMed, Scopus, Google Scholar, Science Direct, and Cochrane Library during January 2010-October 2019. In addition, the reference lists of the articles were also searched. Among 109 electronically searched citations, 42 articles met the inclusion criteria. The highest potential and wide usage of biosensors for the diagnosis of M. tb and its drug resistance belonged to DNA electrochemical biosensors (isoniazid and rifampin strains). Use of biosensors is expanding for the detection of resistant strains of anti-TB antibiotics with high sensitivity and accuracy, while the speed of these sensory methods is considered essential as well. Furthermore, the lowest limit of detection (0.9 fg/ml) from an electrochemical DNA biosensor was based on graphene-modified iron-oxide chitosan hybrid deposited on fluorine tin oxide for the MPT64 antigen target. According to the results, the most common methods used for M. tb detection include acid-fast staining, cultivation, and polymerase chain reaction (PCR). Although molecular techniques (e.g., PCR and real-time PCR) are rapid and sensitive, they require sophisticated laboratory and apparatuses, as well as skilled personnel and expertise in the commentary of the results. Biosensors are fast, valid, and cost-efficient diagnostic method, and the improvement of their quality is of paramount importance in resource-constrained settings.

DNA markers and nano-biosensing approaches for tuberculosis diagnosis

According to WHO 2018 report, 10 million people developed tuberculosis and 1.3 million died from it making it 1 of 10 deadliest diseases worldwide. Tuberculosis is caused by infection with the bacillus Mycobacterium tuberculosis (Mtb). WHO recommends using a specific diagnostic kit Xpert MTB/RIF developed by Cepheid (California, United States). An alarming number of new cases (ca. 558,000) of rifampicin-resistant tuberculosis was diagnosticated in 2017. In recent years, new diagnosis tools targeting the Mtb DNA biomarkers have emerged using a plethora of nanomaterials capable of delivering new technological approaches for the rapid diagnostics of TB and rifampicin-resistant TB (RR-TB). In this chapter, we summarized the state-of-the-art of the current available DNA biomarkers and the potential applications for the development of new diagnosis nanotechnology-based devices. The latter use carbonaceous nanomaterials (graphene and carbon nanotubes), noble metals (silver and gold), semi-conducting (metal oxides, magnetic beads, and quantum dots) in order to reveal and/or to amplify the signal after the recognition of target DNA biomarker. The readout techniques such as colorimetry, fluorescence, surface plasmon resonance, and electrochemical methods were also reviewed. Future is bright for point-of-care diagnostics with a sample-in answer-out approach that hampers user-error through miniaturization of biochip technology to the nanoscale range, which will enable their use by nonspecialized personnel.

Electrochemical determination of M. tuberculosis antigen based on Poly(3,4-ethylenedioxythiophene) and functionalized carbon nanotubes hybrid platform

An electrochemical DNA aptasensor for the detection of Mycobacterium tuberculosis (M. tb) antigen MPT64, was developed using Poly(3,4-ethylenedioxythiophene) (PEDOT) doped with carbon nanotubes (CNTs). The biotinylated aptamer was immobilized onto streptavidin attached to -COOH functionalized CNTs via streptavidin-biotin interaction. Various characterization studies as FT-IR, FE-SEM, EIS and DPV were done to validate each fabrication step of the aptasensor. Optimization studies related to aptamer concentration and response time were performed. The electrochemical signal generated from the aptamer-target molecule interaction was monitored electrochemically by differential pulse voltammetry in the presence of [Fe(CN)₆]^3-/4- as a redox probe. The aptasensor exhibited limit of detection of 0.5±0.2fgmL^-1 within 15min with stability of 27 days at 4°C and reusability of 7 times after repeated regeneration with 50mM NaOH. The potential application of the aptasensor was established by spike-in studies to obtain recovery in between (88-95)%.

Chitosan-iron oxide nanocomposite based electrochemical aptasensor for determination of malathion

An electrochemical aptasensor based on chitosan-iron oxide nanocomposite (CHIT-IO) film deposited on fluorine tin Oxide (FTO) was developed for the detection of malathion. Iron oxide nanoparticles were prepared by co-precipitation method and characterized by Transmission electron microscopy and UV-Visible spectroscopy. The biotinylated DNA aptamer sequence specific to the malathion was immobilized onto the iron oxide doped-chitosan/FTO electrode by using streptavidin as linking molecule. Various characterization studies like Field Emission-Scanning Electron Microscopy (FE-SEM), Fourier Transform Infrared Spectroscopy (FT-IR), and Electrochemical studies were performed to attest the successful fabrication of bioelectrodes. Experimental parameters like aptamer concentration, response time, stability of electrode and reusability studies were optimized. Aptamer immobilized chitosan-iron oxide nanocomposite (APT/SA/CHIT-IO/FTO) bioelectrodes exhibited LOD of about 0.001 ng/mL within 15 min and spike-in studies revealed about 80-92% recovery of malathion from the lettuce leaves and soil sample.

Gold nanoparticle decorated graphene sheet-polypyrrole based nanocomposite: its synthesis, characterization and genosensing application

We report herein the synthesis of gold nanoparticle (GNP) decorated-graphene sheets (GO-GNPs) using the template of graphene oxide (GO) by a one-pot solution-based method. A polypyrrole-GO decorated GNP nanocomposite (GO-GNP/PPY) has been electropolymerized using a potentiodynamic method on an indium tin oxide (ITO) coated glass substrate. The as-synthesized nanocomposites are characterized by transmission electron microscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared and Raman spectroscopy. It has been found that GNPs of ca. 13 nm are uniformly dispersed on the surface of GO, and have a high electrochemically active surface area. The surface morphology studies show that PPY structure changes from nanoflowers to nanostars and then to nanosheets with an increase in the scan rate (20-200 mV s(-1)). The prepared GO-GNP/PPY/ITO electrode was further used as a genosensor, where the electrochemical response was measured using methylene blue (MB) as a redox indicator. The genosensor shows a response time of 60 s with high sensitivity (1 × 10(-15) M) and linearity (1 × 10(-15)-1 × 10(-6) M) with the correlation coefficient of 0.9975.

Development of a PCR-free electrochemical point of care test for clinical detection of methicillin resistant Staphylococcus aureus (MRSA)

An MRSA assay requiring neither labeling nor amplification of target DNA has been developed. Sequence specific binding of fragments of bacterial genomic DNA is detected at femtomolar concentrations using electrochemical impedance spectroscopy (EIS). This has been achieved using systematic optimisation of probe chemistry (PNA self-assembled monolayer film on gold electrode), electrode film structure (the size and nature of the chemical spacer) and DNA fragmentation, as these are found to play an important role in assay performance. These sensitivity improvements allow the elimination of the PCR step and DNA labeling and facilitate the development of a simple and rapid point of care test for MRSA. Assay performance is then evaluated and specific direct detection of the MRSA diagnostic mecA gene from genomic DNA, extracted directly from bacteria without further treatment is demonstrated for bacteria spiked into saline (10(6) cells per mL) on gold macrodisc electrodes and into human wound fluid (10(4) cells per mL) on screen printed gold electrodes. The latter detection level is particularly relevant to clinical requirements and point of care testing where the general threshold for considering a wound to be infected is 10(5) cells per mL. By eliminating the PCR step typically employed in nucleic acid assays, using screen printed electrodes and achieving sequence specific discrimination under ambient conditions, the test is extremely simple to design and engineer. In combination with a time to result of a few minutes this means the assay is well placed for use in point of care testing.

Polyaniline Langmuir-Blodgett film based aptasensor for ochratoxin A detection

Ochratoxin A (OTA) produced by Aspergillus Ochraceus and Penicillium verrucosum is a very dangerous toxin due to its toxic effects in human beings and its presence in a wide range of food products and cereals. A Langmuir-Blodgett (polyaniline (PANI)-stearic acid (SA)) film based highly sensitive and robust impedimetric aptasensor has been developed for ochratoxin A (OTA) detection. DNA Aptamer (Apt-DNA) specific to OTA has been covalently immobilized onto mixed Langmuir-Blodgett (LB) monolayer comprising of PANI-SA deposited onto indium tin-oxide (ITO) coated glass plates. This Apt-DNA/PANI-SA/ITO aptaelectrode has been characterized using scanning electron microscopy, Fourier transform-infrared spectroscopy, contact angle measurements, cyclic voltammetry and electrochemical impedance spectroscopy, respectively. The Apt-DNA/PANI-SA/ITO aptasensor shows detection of OTA by electrochemical impedance spectroscopy in the linear range of 0.0001 μg/ml (0.1 ng/ml) to 0.01 μg/ml (10 ng/ml) and 1 μg/ml-25 μg/ml with detection limit of 0.1 ng/ml in 15 min. The Apt-DNA/PANI-SA/ITO aptasensor can be reused ∼13 times. The binding or affinity constant (K(a)) of aptamer with OTA, calculated using Langmuir adsorption isotherm, is found be 1.21×10(7) M(-1).