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Results of the studies are reported relating to application of the silanized nanostructured zirconia, electrophoretically deposited onto indium tin oxide (ITO) coated glass for covalent immobilization of the monoclonal antibodies (anti-CYFRA-21-1). This biosensing platform has been utilized for a simple, efficient, noninvasive, and label-free detection of oral cancer via cyclic voltammetry technique. The results of electrochemical response studies conducted on bovine serum albumin (BSA)/anti-CYFRA-21-1/3-aminopropyl triethoxy silane (APTES)/ZrO2/ITO immunoelectrode reveal that this immunoelectrode can be used to measure CYFRA-21-1 (oral cancer biomarker) concentration in saliva samples, with a high sensitivity of 2.2 mA mL ng-1, a linear detection range of 2-16 ng mL-1, and stability of six weeks. The results of these studies have been validated via enzyme-linked immunosorbent assay.

We demonstrate the fabrication of a facile and efficient biosensing platform for electrochemical detection of human cardiac biomarker Troponin I (cTnI) using Tungsten trioxide-reduced graphene oxide (WO 3 -RGO) nanocomposite as a matrix. The in-situ hydrothermal method was employed for the synthesis of the WO 3 -RGO nanocomposite. Raman spectroscopy, X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FE-SEM) were employed to investigate structural and morphological behavior. The WO 3 -RGO nanocomposite was further functionalized with 3-aminopropyl tri-ethoxy saline (APTES) for the activation of amino groups (‒NH 2 ) that can covalently bind to the antibodies of cTnI. This immunosensor was further studied using contact angle measurement, Fourier transform infrared spectroscopy (FT-IR) and electrochemical techniques. The synergistic behavior between RGO and WO 3 nanorods has allowed the immunosensor to exhibit enhanced heterogeneous electron transfer rate constant (K o  = 2.4 × 10 −4 cms -1 ) resulting in improved biosensor efficiency. The immuno-sensor exhibit good sensitivity as 58.24 μA/cm 2 per decade in an extended linear detection range 0.01–250 ng/mL with the stability up to 30 days. Besides this, the fabricated immuno-sensor exhibits good reproducibility and excellent selectivity towards the detection of the cTnI biomarker. Furthermore, the validation of immunosensor with cardiac patient samples demonstrates the clinical application of this nano-biosensing platform for the detection of other biomarkers too. [ABSTRACT FROM AUTHOR]

The present work introduces partially reduced graphene oxide (pRGO)-silica (SiO 2 ) particles hybrid system (pRGOSHs) for sensitive and cost effective free cholesterol detection. Fabricated out of thin layers of pRGOSHs, these proposed ChOx/pRGOSHs/ITO based biosensors have a detection range of 2.6–15.5 mM with an appreciable detection limit of 1.3 mM and sensitivity of 11.1 μA/mM/cm 2 . Low Michaelis–Menten constant (K m ) (4.9 × 10 − 4 mM) and high diffusivity constant (D) (3.2 × 10 − 10 cm 2 /s) values clearly indicate enhanced immobilization of enzyme over the substrate. Additionally, electrochemical impedance studies indicate that the synergistic combination of SiO 2 and pRGO also results in much lower impedance values (40% and 18% decrease in comparison to SiO 2 and pRGO respectively) for an overall enhanced sensing performance. These results are further corroborated by the density functional theory based theoretical simulations indicating enhanced electron density (theoretically) in case of the proposed hybrid system. Finally, the present work also highlights the importance of Si–OH bonds formation in the proposed pRGOSHs composite system for attaining such enhanced biosensing ability. [ABSTRACT FROM AUTHOR]

Abstract: We have fabricated the chemically functionalized multi-walled carbon nanotubes (MWCNT) electrophoretically deposited onto indium tin oxide for urea detection. Urease and glutamate dehydrogenase are attached to MWCNT/ITO electrode surface covalently using ethyl-dimethylaminopropyl-carbodiimide and N-hydroxysuccinimide coupling chemistry. Excellent electrochemical properties of MWCNT and covalent functionalization of dual enzyme improve biosensor stability and sensitivity. The electrochemical response studies of the proposed biosensor exhibits wide detection range (0.83–24.9mM), low detection limit (1.3mM) and higher sensitivity of 4.67μAmM−1 cm−2. The low magnitude (0.274mM) of the apparent Michaelis–Menten constant (K m) value indicates high enzymatic affinity of Urs–GLDH enzymes on MWCNT/ITO electrode surface. [Copyright &y& Elsevier]

This report describes the fabrication of a novel microfluidics nanobiochip based on a composite comprising of nickel oxide nanoparticles (nNiO) and multiwalled carbon nanotubes (MWCNTs), as well as the chip's use in a biomedical application. This nanocomposite was integrated with polydimethylsiloxane (PDMS) microchannels, which were constructed using the photolithographic technique. A structural and morphological characterization of the fabricated microfluidics chip, which was functionalized with a bienzyme containing cholesterol oxidase (ChOx) and cholesterol esterase (ChEt), was accomplished using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy. The XPS studies revealed that 9.3% of the carboxyl (COOH) groups present in the nNiO-MWCNT composite are used to formamide bonds with the NH2 groups of the bienzyme. The response studies on this nanobiochip reveal good reproducibility and selectivity, and a high sensitivity of 2.2 mA/mM/cm2. This integrated microfluidics biochip provides a promising low-cost platform for the rapid detection of biomolecules using minute samples. [ABSTRACT FROM AUTHOR]

Abstract: We report results of studies relating to the development of an electrochemical immunosensor based on carboxylated multiwalled carbon nanotubes (c-MWCNTs) electrophoretically deposited onto indium tin oxide (ITO) glass. This c-MWCNTs/ITO electrode surface has been functionalized with monoclonal aflatoxin B1 antibodies (anti-AFB1) for the detection of aflatoxin-B1 using electrochemical technique. Electron microscopy, X-ray diffraction and Raman studies suggest successful synthesis of c-MWCNTs and the Fourier transform infra-red spectroscopic (FT-IR) studies reveal its carboxylic functionalized nature. The proposed immunosensor shows high sensitivity (95.2μAng−1 mLcm−2), improved detection limit (0.08ngmL−1) in the linear detection range of 0.25–1.375ngmL−1. The low value of association constant (0.0915ngmL−1) indicates high affinity of immunoelectrode towards aflatoxin (AFB1). [Copyright &y& Elsevier]

We report results of studies relating to the fabrication of a microfluidics cholesterol sensor based on nanocrystalline anatase-titanium dioxide (ant-TiO2) film deposited onto indium tin oxide (ITO) glass. The results of response studies (optimized under the flow rate of 30 μl/min) conducted on cholesterol oxidase (ChOx) immobilized onto crystalline ant-TiO2 nanoparticles (∼27 nm)/ITO microfluidics electrode reveal linearity as 1.3 to 10.3 mM and improved sensitivity of 94.65 μA/mM/cm2. The observed low value of Km (0.14 mM) indicates high affinity of ChOx to cholesterol. No significant changes in current response of this microfluidics sensor are measured in the presence of different interferents. [ABSTRACT FROM AUTHOR]

We present a straightforward method for fabricating functional micro-, submicro-, and nano-channels embedded in a porous carbon film and the application of this microfluidic platform for electrochemical sensing. A skin layer of poly(methyl methacrylate) (PMMA) fibers was first electrospun on a thoroughly cleaned Si wafer substrate, followed by spin coating of a polyacrylonitrile (PAN) film on top of the skin. High-temperature carbonization of the composite film decomposed the PMMA fibers and produced embedded microchannels in the PAN-derived amorphous monolithic carbon electrode. The channels were decorated with Pt nanoparticles by in situ thermal decomposition of a precursor metal salt to enhance functionality of the carbon electrode. Carbon electrodes decorated with Pt nanoparticles (carbon-Pt), with and without embedded microchannels, were used to detect the food toxin aflatoxin B1 (AFB1) by surface biofunctionalization with the antibodies of AFB1 (anti-AFB1) via an electrochemical impedance technique. The aligned nanochannels in the porous carbon film act as a reaction chamber for antigen–antibody interactions and provide channels for fast electron transport toward the electrode from the electrolyte, resulting in improved electrochemical performance of the biosensor. The fabricated immunosensor is highly sensitive to 1 pg/mL of AFB1 with a concentration range of 10 −12 –10 −7 g/mL. [ABSTRACT FROM AUTHOR]

We report results of the studies relating to the fabrication of a paper based sensor comprising of poly (3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and reduced graphene oxide (RGO) composite. The effect of various solvents like methanol, ethylene glycol and H 2 SO 4 on the electrical conductivity of PEDOT:PSS coated Whatman paper has been investigated. The conductivity of this solution processed conducting paper significantly increases from ~1.16×10 −4 S cm −1 up to ~3.57×10 −2 S cm −1 (~300 times) on treatment with ethylene glycol. The observed significant increase in electrical conductivity is due to conformational rearrangement in the polymer and is due to strong non-covalent cooperative interaction between PEDOT and the cellulose molecules. Further, incorporation of RGO into the conducting paper results in improved electrochemical performance and signal stability. This paper electrode is a promising alternative over the expensive conventional electrodes (ITO, gold and glassy carbon), that are known to have limited application in smart point-of-care (POC) devices. This low cost, flexible and environment friendly conducting paper based biosensor utilized for cancer biomarker (carcinoembryonic antigen, CEA) detection reveals high sensitivity of 25.8 µA ng −1 mL cm −2 in the physiological range, 1–10 ng mL −1 . [ABSTRACT FROM AUTHOR]

Abstract: Electrochemically deposited biocompatible zirconia (ZrO2) film on gold coated glass electrodes has been utilized for the fabrication of urea biosensor. The prepared ZrO2 films and bioelectrodes have been characterized using Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and electrochemical techniques, respectively. The urea biosensor, fabricated by immobilizing mixed enzyme [urease (Urs) and glutamate dehydrogenase (GLDH)] on this nanobiomaterial, shows linearity up to 40mgdL−1 of analyte (urea) and sensitivity of 0.071μA/(mMcm−2) with stability up to 4months when stored at 4°C. The low value of Michaelis–Menten constant (K m ) estimated using Hans plot as 0.5mM indicates enhancement in the affinity and/or activity of enzyme attached to this nanostructured biocompatible matrix. [Copyright &y& Elsevier]

Motivation behind the present work is to fabricate a cost effective and scalable biosensing platform for an easy and reliable detection of cancer biomarker Carcinoembryonic antigen (CEA). Here, we report the sensitive and selective detection of CEA using graphene based bio-sensing platform. Large sized (~ 2.5 × 1.0 cm 2 ), uniform, continuous, single and few layers graphene films have been grown on copper (Cu) substrate employing chemical vapor deposition (CVD) technique using hexane as a liquid precursor. Functional group has been created over Graphene/Cu substrate through π-π stacking of 1- pyrenebutanoic acid succinimidyl ester (PBSE). Further, to make the sensor specific to CEA, antibody of CEA (anti-CEA) has been covalently immobilized onto PBSE/Graphene/Cu electrode. Selective and sensitive detection of CEA is achieved by anti-CEA/PBSE/Graphene/Cu electrode through electrochemical impedance spectroscopy (EIS) measurements. Under optimal condition, the fabricated sensor shows linear response in the physiological range 1.0–25.0 ng mL −1 (normal value ~ 5.0 ng mL −1 ), revealing sensitivity 563.4 Ω ng −1 mL cm −2 with a correlation coefficient of 0.996 and limit of detection (LOD) 0.23 ng mL −1 . In this way, one step electrode fabrication with high specific surface area provides a light weight, low cost, reliable and scalable novel biosensing platform for sensitive and selective detection of CEA. We believe that this bioelectrode equipped with specific recognition elements could be utilized for detection of other biomolecules too. [ABSTRACT FROM AUTHOR]

We report results of the studies relating to the development of a non-invasive, label free immunosensor based on nanostructured hafnium oxide (hafinia) deposited onto indium tin oxide (ITO) coated glass for oral cancer biomarker (CYFRA-21-1) detection in human saliva. The nanostructured hafnia (nHfO 2 ) has been synthesized via one step low temperature hydrothermal process and modified with 3-aminopropyltriethoxy silane (APTES) for covalent immobilization of monoclonal antibodies (anti-CYFRA-21-1). Bovine serum albumin (BSA) was used to block non-specific sites at the anti-CYFRA-21-1/APTES/nHfO 2 /ITO electrode surface. The structural, morphological and spectroscopic characterization of the synthesized nanomaterials and fabricated electrodes has been carried out using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) studies, respectively. The results of response studies conducted on BSA/anti-CYFRA-21-1/APTES/nHfO 2 /ITO immunoelectrode reveal that this biosensor has high sensitivity (9.28 μA mL ng −1 cm −2 ), wide linear detection range (2–18 ng mL −1 ) and fast response time (15 min). This immunosensor has been validated with enzyme linked immunosorbent assay (ELISA) in saliva samples of oral cancer patients. [ABSTRACT FROM AUTHOR]