Non-enzymatic glucose detection with screen-printed chemiresistive sensor using green synthesised silver nanoparticle and multi-walled carbon nanotubes-zinc oxide nanofibers.

Non-enzymatic screen-printed chemiresistive interdigitated electrodes (SPCIE) were designed and fabricated using a low-cost screen-printing method for detection of the glucose. The interdigitated electrodes (IDE) pattern was printed using conductive graphene ink on the glossy surface of the photo paper. The proposed glossy photo paper-based SPCIE are functionalized with multi-walled carbon nanotubes-zinc oxide (MWCNTs-ZnO) nanofibers to create the chemiresistive matrix. Further, to bind these nanofibers with the graphene electrode surface, we have used the green synthesized silver nanoparticles (AgNPs) with banana flower stem fluid (BFSF) as a binder solution. AgNPs with BFSF form the conductive porous natural binder layer (CPNBL). It does not allow to increase the resistivity of the deposited material on graphene electrodes and also keeps the nanofibers intact with paper-based SPCIE. The synthesized material of MWCNT-ZnO nanofibers and green synthesized AgNPs with BFSF as a binder were characterized by Ultraviolet-visible spectroscopy (UV-vis), scanning electron microscope (SEM), x-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The amperometric measurements were performed on the proposed SPCIE sensor to detect the glucose sample directly. The innovative paper-based SPCIE glucose sensor exhibits a linear corelation between current measurements and glucose concentration in the range between 45.22µm and 20 mm, with a regression coefficient (R2) of 0.9902 and a lower limit of detection (LoD) of 45.22µm (n= 5). The sensitivity of the developed SPCIE sensor was 2178.57µAmM-1cm-2, and the sensor's response time determined was approximately equal to 18 s. The proposed sensor was also tested for real blood serum sample, and relative standard deviation (RSD) was found equal to 2.95%.

Device-Physics Realization of ZnO-MWCNT Nanostructure-Based Field-Effect Biosensor for Ultrasensitive Simultaneous Genomic Detection of Foodborne Pathogens.

The complex and versatile interactions among the wide variety of the nanostructures and the target analytes have primarily limited the detailed investigation of the transduction mechanism of nanomaterial-assisted electrical signal-based biosensors despite their high sensitivity, low-cost, portability, and ease of deployment. Hence, no common ground is formed detailing the principle of operation, demanding a strong need for systematic examination instead of hit and trial. Therefore, a maiden mechanistic investigation has been carried out in this paper for a field-effect-based biosensor device relying on the energy band diagram and the surface potential profile. To demonstrate the experimental evidence and appreciate the importance of food safety, three hazardous foodborne pathogens (Proteus mirabilis, Escherichia coli, and Clostridium botulinum) have been detected herein. The biosensor device, built on a hydrothermally synthesized zinc oxide and MWCNT (ZnO-MWCNT) composite nanostructure, simultaneously incorporates three fairly specific ss-DNA probes. Furthermore, the unmet challenge of biosensor device variability is addressed through the optimum selection of operating voltage of the device via a unique "voltage-selection-algorithm". We believe that the rigorous experimentation and the insightful device-physics realization demonstrated in this work will pave the way for a future decisive biosensor platform.

Electrochemical nano-biosensor based on electrospun indium zinc oxide nanofibers for the determination of complement component 3 protein.

Age-related macular degeneration (AMD) is a progressive chronic neurodegenerative retinal disease leading to vision loss, irreversible blindness, and visual impairment in older adults worldwide. Complement component 3 (C3) protein has been identified as the most predominant biomarker towards early diagnosis of AMD; therefore, there is an utmost requirement for non-invasive detection of C3 protein in the tear fluids of AMD patients. Considering this, we report an insightful electrochemical sensor capable of detecting clinically relevant concentrations ranging from 10 fg/mL to 1 µg/mL using electrospun indium-doped zinc oxide (InZnO) nanofibers as the transducing layer. The InZnO nanofibers have facilitated high anti-C3 antibody loading of 3.42 × 10-9 mol/cm2 and enhanced the overall charge transport mechanism at the sensor interface. The biofunctionalization process of the biosensor was investigated thoroughly using X-ray photoelectron spectroscopy (XPS) as well as different electrochemical techniques. The target C3 proteins were captured on the fabricated biosensor surface and determined through changes in charge transfer resistance (RCT) while executing electrochemical impedance spectroscopy (EIS) and peak current (Ip) in the case of cyclic voltammetry (CV) and differential pulse voltammetry (DPV), respectively. The InZnO nanofiber-based nano-biosensor demonstrated a very low limit of detections (LODs) of 5.214 fg/mL and 0.241 fg/mL with an excellent sensitivity of 4.6709 (ΔR/R) (g/mL)-1 cm-2 and 54.4939 (ΔIp/Ip)% (g/mL)-1 cm-2 for EIS and DPV techniques, respectively. By virtue of high antibody loading, ultrasensitive and ultra-selective capability, the indium-doped ZnO nanofibers show huge potential to be used as a high-performance diagnostic platform for AMD diagnosis.

2D vanadium disulfide nanosheets assisted ultrasensitive, rapid, and label-free electrochemical quantification of cancer biomarker (MMP-2).

Cancer is one of the most tormenting global health burdens reporting high mortality and morbidity worldwide. Matrix metalloproteinase 2 (MMP-2) protein has elevated expression for most types of cancers, including prostate and breast cancer. Therefore, accurate and specific detection of MMP-2 biomarker is crucial for screening, treatment, and prognosis of related cancer. In this work, we have proposed a label-free electrochemical biosensor for the detection of MMP-2 protein. This biosensor was fabricated using hydrothermally synthesized vanadium disulfide (VS2) nanosheets with monoclonal anti-MMP2 antibodies biofunctionalized using a suitable linker. The VS2nanomaterials were synthesized hydrothermally at different reaction temperatures (140 °C, 160 °C, 180 °C and 200 °C) generating different morphologies from a 3D bulk cubic structure at 140 °C to 2D nanosheets at 200 °C. Owing to the advantages of 2D VS2nanosheets with high surface-to-volume ratio, excellent electrochemical response and high antibody loading possibility, it was selected for fabricating an MMP-2 specific biosensor. The antibody-antigen binding event is analyzed by recording electrochemical impedance spectroscopy signals for different target MMP-2 protein concentrations. The sensitivity and lower limit of detection were 7.272 (ΔR/R)(ng ml)-1cm-2and 0.138 fg ml-1, respectively in 10 mM phosphate buffer saline for this proposed sensor. Further, interference studies were also performed which demonstrates the sensor to be highly selective against non-specific target proteins. This 2D VS2nanosheet-based electrochemical biosensor is a sensitive, cost-effective, accurate, and selective solution for cancer diagnosis.

Tear-based MMP-9 detection: A rapid antigen test for ocular inflammatory disorders using vanadium disulfide nanowires assisted chemi-resistive biosensor.

A sensitive, non-invasive, and biomarker detection in tear fluids for inflammation in potentially blinding eye diseases could be of great significance as a rapid diagnostic tool for quick clinical decisions. In this work, we propose a tear-based MMP-9 antigen testing platform using hydrothermally synthesized vanadium disulfide nanowires. Also, various factors contributing to baseline drifts of the chemiresistive sensor including nanowire coverage on the interdigitated microelectrode of the sensor, sensor response duration, and effect of MMP-9 protein in different matrix solutions were identified. The drifts on the sensor baseline due to nanowire coverage on the sensor were corrected using substrate thermal treatment providing a more uniform distribution of nanowires on the electrode which brought the baseline drift to 18% (coefficient of variations, CV = 18%). This biosensor exhibited sub-femto level limits of detection (LODs) of 0.1344 fg/mL (0.4933 fmoL/l) and 0.2746 fg/mL (1.008 fmoL/l) in 10 mM phosphate buffer saline (PBS) and artificial tear solution, respectively. For a practical tear MMP-9 detection, the proposed biosensor response was validated with multiplex ELISA using tear samples from five healthy controls which showed excellent precision. This label-free and non-invasive platform can serve as an efficient diagnostic tool for the early detection and monitoring of various ocular inflammatory diseases.

Near perfect classification of cardiac biomarker Troponin-I in human serum assisted by SnS2-CNT composite, explainable ML, and operating-voltage-selection-algorithm.

The high worldwide mortality and disproportionate impact of cardiovascular diseases have emerged as the most significant global health burden, unfortunately, unmet by the traditional detection methods. Therefore, developing a rapid, sensitive, selective, and rugged biosensor for the precise classification/quantification of cardiac biomarkers is a stepping stone for the future generation of cardiac healthcare. We demonstrate a facile, time-efficient, and scalable biosensor for classifying the FDI approved gold standard cardiac biomarker Troponin-I (cTnI) in untreated human serum matrix, built-on 2-D SnS2 and 1-D MWCNT composite transducer and decision-tree based explainable machine learning (ML) algorithm. The proposed methodology is further enhanced using an inimitable Operating-Voltage-Selection-Algorithm (OVSA), which boosts ML accuracy to ∼100%. The near-perfect classification is realized by strategically incorporating this two-step algorithm-first the OVSA, then the heuristic and ML approaches on the selected dataset. Dynamic concentrations of the biomarker (100 fg/mL to 100 ng/mL) are estimated with high sensitivity, ∼71 (ΔR/R) (ng/mL)-1cm-2 and low limit of detection (0.02 fg/mL), aiding to the prediction and prognosis of acute myocardial infarction. The hyperparameter tuning and feature engineering improve the decision process of the ML algorithm, fostering robustness against data variability. Feature importance indices, namely the Gini index, Permutation Importance, and SHAP values, portray 'Voltage' as the most important feature, further justifying our insight into the OVSA. The biosensor's specificity, selectivity, reproducibility and stability are effectively demonstrated with the sampling to result reporting time of just 20 min, establishing it as a potential candidate for clinical testing.

Label-free, ultrasensitive and rapid detection of FDA-approved TBI specific UCHL1 biomarker in plasma using MWCNT-PPY nanocomposite as bio-electrical transducer: A step closer to point-of-care diagnosis of TBI.

Traumatic Brain Injury (TBI), a major cause of mortality and neurological disability affecting people of all ages worldwide, remains a diagnostic and therapeutic challenge to date. Rapid, ultra-sensitive, selective, and wide-range detection of TBI biomarkers in easily accessible body fluids is an unmet clinical need. Considering this, in this work, we report the design and development of a facile, label-free, highly stable and sensitive, chemi-impedance-based sensing platform for rapid and wide range detection of Ubiquitin-carboxy terminal hydrolase L1 (UCHL1: FDA-approved TBI specific plasma biomarker), using carboxylic functionalized MWCNTs embedded polypyrrole (PPY) nanocomposites (PPY/f-MWCNT). The said nanocomposites were synthesized using chemical oxidative polymerization method. Herein, the functionalized MWCNTs are used as conducting fillers so as to increase the polymer's dielectric constant according to the micro-capacitor model, thereby augmenting both DC electrical conductivity and AC dielectric property of the nanocomposite. The proposed immunosensing platform comprises of PPY/f-MWCNT modified interdigitated microelectrode (IDµEs) array, on which anti-UCHL1-antibodies are immobilized using suitable covalent chemistry. The AC electrical characterization of the nanocomposite modified IDµEs, with and without the antibodies, was performed through generic capacitance vs. frequency (C-F, 1 KHz - 1 MHz) and capacitance vs. applied bias (C-V, 0.1 V-1 V) measurements, using an Agilent B1500A parametric analyzer. The binding event of UCHL1 peptides to anti-UCHL1-antibodies was transduced in terms of normalised changes in parallel capacitance, via the C-F analysis. Further, we have tested the detection efficiency of the said immunoassay against UCHL1 spiked human plasma samples in the concentration range 10 fg/mL - 1 µg/mL. The proposed sensing platform detected UCHL1 in spiked-plasma samples linearly in the range of 10 fg/mL - 1 ng/mL with a sensitivity and LoD of 4.22 ((ΔC/C0)/ng.mL-1)/cm2 and 0.363 fg/mL, respectively. Further, it showed excellent stability (30 weeks), repeatability, reproducibility, selectivity and interference-resistance. The proposed approach is label-free, and if desired, can be used in conjunction with DC measurements, for biosensing applications.

ZnO nanoparticles embedded silk fibroin-a piezoelectric composite for nanogenerator applications.

This paper demonstrates a flexible nanogenerator (NG) using Silk-Zinc Oxide (ZnO) composite by exploiting the inherent piezoelectric properties of silk and ZnO. A direct precipitation method was employed to synthesize Zinc Oxide nanoparticles (NPs). Silk-ZnO composite film was then prepared by spin-coating the homogenous silk-ZnO solution. The composition and morphology of silk-ZnO composite were analyzed using various standard characterization procedures. The biocompatibility study of the composite film was also performed through cell viability testing. The utility of as prepared composites was demonstrated through the fabrication of piezoelectric nanogenerator. This hybrid nanogenerator was capable to generate a maximum open circuit voltage of 25 V (peak to peak value) in the bending state for a specific ZnO concentration. The output response of the nanogenerator exhibited a good correlation with the bending angle of the device. A peak outputpower density of 6.67 mW cm-3was achieved from the nanogenerator. The fabricated prototype is efficient to light-up commercial red LEDs and to harvest energy from human body movement. The piezoelectric coefficient (d33) of silk-ZnO composite film was also experimentally figured out.

Simultaneous Detection of CO and NH3 Gases at Room Temperature with an Array of ZnS Chemiresistive Sensors and the Superposition Principle.

Simultaneous detection of multiple toxic gases in the air using room temperature gas sensors is significant in low-power environmental monitoring applications. However, the low-temperature resistive gas sensors are sensitive to more than one gas, and thus, an array of gas sensors and high energy-consuming machine learning algorithms are required to predict the concentrations of the individual gases in mixed target gas. Here, we report a computationally less intensive method to predict the composition of the target gases using linear gas sensors. A sensor array consisting of two ZnS resistive gas sensors biased at different voltages in conjunction with the superposition principle is used to predict the concentration of individual gases in the binary mixture of NH3 and CO present in the air. Further, the effect of humidity on response is mitigated by formulating the sensitivity of the sensors as a function of relative humidity. The proposed algorithm predicted the concentration of the individual gases in mixed gas with a maximum absolute error of ∼15% irrespective of humidity levels, which is practically allowed in most gas sensing applications. As the superposition principle is a low-power consuming technique, the proposed approach can be used in applications where trace levels of gases in mixed targets need to be detected with energy-efficient methods.

Reduction of the Measurement Time of a Chemiresistive Gas Sensor Using Transient Analysis and the Cantor Pairing Function.

It is vital to measure the concentration of gas quickly in many gas sensing applications. Predicting the steady-state response from the earlier transient response is the economical and viable solution in this regard. However, existing transient analysis approaches either need huge data and computationally intensive algorithms or are inefficient. Here, we described a method to reduce the measurement time of the concentration of CH4 with a chemiresistive gas sensor at room temperature (27 °C). The presented method considers the sensor's response at two fixed time intervals after gas exposure and maps their pairing number to the gas concentration. The proposed method measures the gas concentration in just 30 s from the gas exposure time. As the proposed method can quickly measure gas concentrations, it can be employed in widespread applications where quick quantification of gas is necessary.

Artificial Intelligence-Based Portable Bioelectronics Platform for SARS-CoV-2 Diagnosis with Multi-nucleotide Probe Assay for Clinical Decisions.

In the context of the recent pandemic, the necessity of inexpensive and easily accessible rapid-test kits is well understood and need not be stressed further. In light of this, we report a multi-nucleotide probe-based diagnosis of SARS-CoV-2 using a bioelectronics platform, comprising low-cost chemiresistive biochips, a portable electronic readout, and an Android application for data acquisition with machine-learning-based decision making. The platform performs the desired diagnosis from standard nasopharyngeal and/or oral swabs (both on extracted and non-extracted RNA samples) without amplifying the viral load. Being a reverse transcription polymerase chain reaction-free hybridization assay, the proposed approach offers inexpensive, fast (time-to-result: ≤ 30 min), and early diagnosis, as opposed to most of the existing SARS-CoV-2 diagnosis protocols recommended by the WHO. For the extracted RNA samples, the assay accounts for 87 and 95.2% test accuracies, using a heuristic approach and a machine-learning-based classification method, respectively. In case of the non-extracted RNA samples, 95.6% decision accuracy is achieved using the heuristic approach, with the machine-learning-based best-fit model producing 100% accuracy. Furthermore, the availability of the handheld readout and the Android application-based simple user interface facilitates easy accessibility and portable applications. Besides, by eliminating viral RNA extraction from samples as a pre-requisite for specific detection, the proposed approach presents itself as an ideal candidate for point-of-care SARS-CoV-2 diagnosis.

Towards point-of-care diagnosis of Alzheimer's disease: Multi-analyte based portable chemiresistive platform for simultaneous detection of ß-amyloid (1-40) and (1-42) in plasma.

Label-free simultaneous detection of Alzheimer's disease (AD) specific biomarkers Aß40 and Aß42 peptides on a single platform using polypyrrole nanoparticle-based chemiresistive biosensors is reported here. The proposed interdigitated-microelectrode based inexpensive multisensor-platform can concurrently detect Aß40 and Aß42 in spiked-plasma in the range of 10-14 - 10-6 g/mL (with LoDs being 5.71 and 9.09 fg/mL, respectively), enabling the estimation of diagnostically significant Aß42/Aß40 ratio. A detailed study has been undertaken here to record the individual sensor responses against spiked-plasma samples with varying amounts and proportions of the two target peptides, towards enabling disease-progression monitoring using the Aß-ratio. As compared to the existing cost-ineffective brain-imaging techniques such as PET and MRI, and the high-risk CSF based invasive AD biomarkers detecting procedures, the proposed approach offers a viable alternative for affordable point-of-care AD diagnostics, with possible usage in performance evaluation of therapeutic drugs. Towards point-of-care applications, the portable readout used in this work was conjugated with an android-based mobile app for data-acquisition and analysis.

Cerium oxide nanofiber based electroanalytical sensor for TNF-α detection: Improved interfacial stability with Nafion.

The present work is aimed at improving the adhesion of nanomaterials at the interface of solid state working electrodes. Towards this, herein, an efficient method has been proposed that requires the electrode interface to be decorated with an optimally thin layer of Nafion. This selectively permeable layer ensures the stability of the sensor interface, without hampering the transport of biomolecules and electrons. As a case study, here, electrospun Cerium oxide nanofiber (CeNF) modified Glassy carbon electrodes (GCE) have been used as the sensing interface, and stability and performance of the GCE/CeNF/Nafion interface is evaluated using analytical electrochemistry. The CeNF is synthesized via electrospinning and is characterized using X-ray diffraction spectroscopy, Thermal gravimetry, Fourier transform infrared spectroscopy, and Field emission scanning electron microscopy. Further, detection of sepsis specific biomarker TNF-α from spiked buffer samples is demonstrated, as a case study, towards evaluating the effect of Nafion on the interfacial sensitivity. The achieved LOD of GCE/CeNF and GCE/CeNF/Nafion for TNF-α detection were 2.8 fg/mL and 1.2 fg/mL, respectively. A comparative analysis between the Electrochemical impedance spectroscopic (EIS) results of the GCE/CeNF and the GCE/CeNF/Nafion interfaces confirms the improvement in stability, without affecting the sensitivity and the limiting detection.

A facile, sensitive and rapid sensing platform based on CoZnO for detection of fipronil; an environmental toxin.

A sensitive detection of extremely toxic phenylpyrazole insecticide, 'Fipronil' is presented. Currently, the advancement of approaches for the detection of insecticides at low concentrations with less time is important for environmental safety assurance. Considering this fact, an effort has been made to develop an electrospun CoZnO nanofiber (NF) based label-free electrochemical system for the detection of fipronil. The CoZnO NF were characterized using different techniques including field emission scanning electron microscopy (FE-SEM), Energy Dispersive X-Ray Analysis (EDX), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Raman Spectroscopy. Based on the experimental results, the proposed platform displayed a linear response for fipronil in the attogram/mL range despite the multiple interfering agents. The sensitivity of the device was found to be 3.99 Kῼ (g/ml)-1 cm-2. Limit of detection (LOD) and limit of quantification (LOQ) were calculated and found to be 112 ag mL-1 and 340 ag mL-1 respectively. Further, this proposed sensor will be implemented in the fields for the rapid and proficient detection of the real samples.

The Concept of Making On-Chip Thermal Cycler for RT-PCR Using Conjugate Heat Transfer in Diverging Microchannel.

Covid-19 is pandemic to which the world is fighting. Various precautionary measures are being imposed all over the world which is affecting the routine life of an individual and also the economy worldwide. Although, a definite vaccine is still not known to medical science but they are able to distinguish Covid-19 from the other types of flu. Presently this is being done by detecting the SARS-CoV-2 virus using RT-PCR technique as recommended by the World Health Organization (WHO) (WHO, Geneva, 2020). Reverse Transcription Polymerase Chain Reaction (RT-PCR) is a nucleic acid amplification test that converts the RNA into DNA and subsequently amplifies the specific DNA targets. This method was already being employed to detect the severe acute respiratory syndrome-associated coronavirus (SARS-CoV) (Emery et al. in Emerg Infect Dis 10(2):311, 2004). The entire process of DNA amplification takes place in three steps: denaturation, annealing, and extension for which the sample is required to be maintained at constant temperatures of 95, 55 and 72 °C, respectively. This article introduces the technology to achieve a constant temperature which can be tweaked to develop on-chip RT-PCR.

Label-Free Electrochemical Detection of DNA Hybridization: A Method for COVID-19 Diagnosis.

This paper presents label-free electrochemical transduction as a suitable scheme for COVID-19-specific viral RNA/c-DNA detection, with an aim to facilitate point of care diagnosis. In lieu of this, we discuss the proposed electrochemical biosensing scheme, based on electrodeposited gold nanoparticles as the transducing elements. Specific to this approach, here, the protocols associated with the immobilization of the single-stranded probe nucleotide on to the biosensor, have also been laid out. This paper also discusses the methods of electrochemical analysis, to be used for data acquisition and subsequent calibration, in relation to target analyte detection. Towards facilitating portable diagnosis, development of miniaturized sensors and their integration with readout units have also been discussed.

A miniaturized electrochemical platform with an integrated PDMS reservoir for label-free DNA hybridization detection using nanostructured Au electrodes.

We report the fabrication and characterization of a miniaturized electrochemical platform for the label-free detection of DNA hybridization. The proposed platform is fabricated using microfabrication and electrodeposition techniques. Comprising a Ti working electrode with electrodeposited Au nanostructures, and Pt/Au pseudo-reference and counter electrodes, the device accounts for a limit of detection of 0.97 fM and a sensitivity of 20.78 (µA µM-1) cm-2 with respect to Dengue virus specific consensus primer detection in the range of 10 fM-1 µM. Here, the incorporation of nanostructured Au in the active sensing area not only enhances the current response by increasing the overall surface area, but it also facilitates facile probe DNA immobilization by gold-thiol self-assembly. We have used differential pulse voltammetry analysis in this study to monitor the changes in reaction kinetics with respect to target hybridization. Furthermore, the evaluation of reproducibility of the biosensor and its selectivity against interference has yielded acceptable outcomes. Additionally, in order to evaluate the system's selectivity, we have successfully distinguished PCR amplified wild type and mutant target DNAs corresponding to the BRCA1 specific gene. Here, the mutant and the wild type target DNAs differ by a two base deletion, and the fact that the system is able to differentiate even such minute dissimilarities under hybridization conditions is indicative of its superior performance.

Electrospun tin (IV) oxide nanofiber based electrochemical sensor for ultra-sensitive and selective detection of atrazine in water at trace levels.

Atrazine, a class 3a carcinogen, is a pesticide of chloro triazine family and is known to severely affect the human endocrine system upon consumption. The toxic effects of atrazine cause damage not only to the humans but also to animals and plants. In lieu of the detrimental effects of atrazine on environment, it is essential to develop a sensor platform capable of its detection in water. Here, we propose ultrasensitive electrochemical detection of atrazine using electrospun SnO2 nanofibers. In this study, the nanofibers have been characterized using Field Emission Spectroscopy, X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), UV-Vis-NIR spectroscopy and Fourier transform infrared spectroscopy (FTIR). Using a label-free transduction, we have detected atrazine in fairly low concentrations, with the limit of detection being 0.9 zM and the sensitivity being 4.11 (µA/µM)/cm2, in a wide dynamic detection range varying from 1 zM to 1 µM. Furthermore, we have reported atrazine detection in trace levels in spiked real time water samples, which is an essential step in ensuring that the sensing platform can be deployed for practical applications. In addition to this, the sensor exhibits excellent selectivity, reasonable stability (when stored at 4 °C), and good interference-resistance.

Chemiresistive DNA hybridization sensor with electrospun nanofibers: A method to minimize inter-device variability.

Chemiresistive platforms are best suited for developing DNA hybridization detection systems, owing to their ease of fabrication, simple detection methodology and amenability towards electronics. In this work, we report development of a generic, robust, electrospun nanofiber based interdigitated chemiresistive platform for DNA hybridization detection. The platform comprises of interdigitated metal electrodes decorated with electrospun nanofibers on the top. Two approaches viz., drop casting of graphene doped Mn2O3 nanofibers (GMnO) and direct electrospinning of polyaniline/polyethylene oxide (PANi/PEO) composite nanofibers, have been utilized to decorate these electrodes. In both approaches, inter-device variability, a key challenge for converting this proof-of-concept into a tangible prototype/product, has been addressed using a shadow masking technique. Consequently, the relative standard deviation for multiple PANi/PEO nanofiber based chemiresistors has been brought down from 17.82% (without shadow masking) to 4.41% (with shadow masking). The nanofibers are further modified with single-stranded probe DNAs, to capture a desired hybridization event. To establish the generic nature of the platform, detection of multiple target DNAs has been successfully demonstrated. These targets include dengue virus specific consensus primer (DENVCP) and four DNAs corresponding to Staphylococcus aureus specific genes, namely nuc, mecA, vanA and protein A. The chemiresistive detection of DENVCP has been performed in the concentration range of 10 fM - 1 µM, whereas the detection of the other targets has been carried out in the range of 1 pM - 1 µM. Using a 3σ method, we have estimated the limit of detection for the chemiresistive detection of DENVCP to be 1.9 fM.