Browsing by Author "B.D. Malhotra"

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A self assembled monolayer based microfluidic sensor for urea detection
(2011) Saurabh Srivastava; Pratima R. Solanki; Ajeet Kaushik; Md. Azahar Ali; Anchal Srivastava; B.D. Malhotra
Urease (Urs) and glutamate dehydrogenase (GLDH) have been covalently co-immobilized onto a self-assembled monolayer (SAM) comprising of 10-carboxy-1-decanthiol (CDT) via EDC-NHS chemistry deposited onto one of the two patterned gold (Au) electrodes for estimation of urea using poly(dimethylsiloxane) based microfluidic channels (2 cm × 200 μm × 200 μm). The CDT/Au and Urs-GLDH/CDT/Au electrodes have been characterized using Fourier transform infrared (FTIR) spectroscopy, contact angle (CA), atomic force microscopy (AFM) and electrochemical cyclic voltammetry (CV) techniques. The electrochemical response measurement of a Urs-GLDH/CDT/Au bioelectrode obtained as a function of urea concentration using CV yield linearity as 10 to 100 mg dl-1, detection limit as 9 mg dl -1 and high sensitivity as 7.5 μA mM-1 cm-2. © 2011 The Royal Society of Chemistry.
Electrophoretically deposited reduced graphene oxide platform for food toxin detection
(2013) Saurabh Srivastava; Vinod Kumar; Md. Azahar Ali; Pratima R. Solanki; Anchal Srivastava; Gajjala Sumana; Preeti Suman Saxena; Amish G. Joshi; B.D. Malhotra
Reduced graphene oxide (RGO) due to its excellent electrochemical properties and large surface area, has recently aroused much interest for electrochemical biosensing application. Here, the chemically active RGO has been synthesized and deposited onto an indium tin oxide (ITO) coated glass substrate by the electrophoretic deposition technique. This novel platform has been utilized for covalent attachment of the monoclonal antibodies of aflatoxin B1 (anti-AFB1) for food toxin (AFB1) detection. The electron microscopy, X-ray diffraction, and UV-visible studies reveal successful synthesis of reduced graphene oxide while the XPS and FTIR studies suggest its carboxylic functionalized nature. The electrochemical sensing results of the anti-AFB1/RGO/ITO based immunoelectrode obtained as a function of aflatoxin concentration show high sensitivity (68 μA ng -1 mL cm-2) and improved detection limit (0.12 ng mL -1). The association constant (ka) for antigen-antibody interaction obtained as 5 × 10-4 ng mL-1 indicates high affinity of antibodies toward the antigen (AFB1). © The Royal Society of Chemistry 2013.
Fabrication of sensitive bioelectrode based on atomically thin CVD grown graphene for cancer biomarker detection
(Elsevier Ltd, 2018) Vijay K. Singh; Saurabh Kumar; Sumit Kumar Pandey; Saurabh Srivastava; Monu Mishra; Govind Gupta; B.D. Malhotra; R.S. Tiwari; Anchal Srivastava
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 cm2), 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. © 2018 Elsevier B.V.
Graphene Oxide-Based Biosensor for Food Toxin Detection
(Humana Press Inc., 2014) Saurabh Srivastava; Md Azahar Ali; Sima Umrao; Upendra Kumar Parashar; Anchal Srivastava; Gajjala Sumana; B.D. Malhotra; Shyam Sudhir Pandey; Shuji Hayase
We report results of the studies relating to the fabrication of a highly sensitive label free biosensor based on graphene oxide (GO) platform for the detection of aflatoxin B1 (AFB1) which is most toxic and predominant food toxin, using electrochemical impedance spectroscopy. The structural and optical characterization of GO/Au and anti-AFB1/GO/Au has been done by electron microscopy, Raman, X-ray diffraction (XRD), UV–vis and electrochemical impedance spectroscopy (EIS). The impedimetric sensing response of immunoelectrode as a function of AFB1 concentration reveals wider linear detection range (0.5–5 ng/ml), high sensitivity (639 Ω ng−1 ml), improved detection limit (0.23 ng ml−1) and good stability (5 weeks) for the label-free detection. Association constant (ka) for antigen–antibody interaction obtained as 0.46 ng ml−1 indicates high affinity. © 2014, Springer Science+Business Media New York.
Mesoporous silica particle embedded functional graphene oxide as an efficient platform for urea biosensing
(Royal Society of Chemistry, 2014) Shiju Abraham; Valerian Ciobota; Saurabh Srivastava; Sunil K. Srivastava; Rajesh K. Singh; Jan Dellith; B.D. Malhotra; Michael Schmitt; Jürgen Popp; Anchal Srivastava
The mesoporous silica particle embedded graphene oxide (GO) hybrid system is a promising platform for electrochemical biosensing owing to its large 2-dimensional structure, fast electron transfer kinetics, improved hydrophilic nature and surplus functional groups. Here, GO sheets were synthesized by Hummer's improved method and sub-micron sized homogeneous mesoporous silica (SiO2) particles were prepared by Stober's method. The SiO 2 particles were embedded on the GO surfaces and were optimized with different concentrations for better applicability and hydrophilicity. Micro-structural and spectroscopic characterization of as-synthesized materials was carried out to confirm the successful synthesis as well as the functionalities required for biosensing. Scanning electron microscopy investigations suggest that the average size of the SiO2 particles decorated on the GO surface is ∼500 nm. Raman investigation provides information regarding the increase in defects and disorder on the GO surface with the increase in the SiO2 content. The optimized GO-SiO 2 (GOS) composite electrode was prepared by the electrophoretic deposition technique and was used for the attachment of urease and glutamate dehydrogenase enzymes for urea detection employing the cyclic voltammetry method. The reproducibility, specificity and stability of the fabricated biosensor were found to be excellent for the urea sensing. Such an easy and cost effective material based GOS urea sensor showed a high sensitivity (2.6 μA mM-1 cm-2) and a good detection limit (14 mg dL -1). This journal is © the Partner Organisations 2014.
Reduced graphene oxide-titania based platform for label-free biosensor
(Royal Society of Chemistry, 2014) Pratima R. Solanki; Saurabh Srivastava; Md. Azahar Ali; Rajesh Kr. Srivastava; Anchal Srivastava; B.D. Malhotra
A label-free biosensor has been fabricated using a reduced graphene oxide (RGO) and anatase titania (ant-TiO2) nanocomposite, electrophoretically deposited onto an indium tin oxide coated glass substrate. The RGO-ant-TiO2 nanocomposite has been functionalized with protein (horseradish peroxidase) conjugated antibodies for the specific recognition and detection of Vibrio cholerae. The presence of Ab-Vc on the RGO-ant-TiO2 nanocomposite has been confirmed using electron microscopy, Fourier transform infrared spectroscopy and electrochemical techniques. Electrochemical studies relating to the fabricated Ab-Vc/RGO-ant-TiO2/ITO immunoelectrode have been conducted to investigate the binding kinetics. This immunosensor exhibits improved biosensing properties in the detection of Vibrio cholerae, with a sensitivity of 18.17 × 106 F mol-1 L-1 m-2 in the detection range of 0.12-5.4 nmol L-1, and a low detection limit of 0.12 nmol L-1. The association (ka), dissociation (kd) and equilibrium rate constants have been estimated to be 0.07 nM, 0.002 nM and 0.41 nM, respectively. This Ab-Vc/RGO-ant-TiO2/ITO immunoelectrode could be a suitable platform for the development of compact diagnostic devices. © The Royal Society of Chemistry 2014.