Browsing by Author "Gajjala Sumana"

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Carboxylated multiwalled carbon nanotubes based biosensor for aflatoxin detection
(2013) Chandan Singh; Saurabh Srivastava; Md. Azahar Ali; Tejendra K. Gupta; Gajjala Sumana; Anchal Srivastava; R.B. Mathur; Bansi D. Malhotra
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 (95.2 μA ng-1 mL cm-2), improved detection limit (0.08 ng mL-1) in the linear detection range of 0.25-1.375 ng mL-1. The low value of association constant (0.0915 ng mL -1) indicates high affinity of immunoelectrode towards aflatoxin (AFB1). © 2013 Elsevier B.V.
Cationic poly(lactic-co-glycolic acid) iron oxide microspheres for nucleic acid detection
(2013) Chandra Mouli Pandey; Aditya Sharma; Gajjala Sumana; Ida Tiwari; Bansi Dhar Malhotra
Herein, we envisage the possibility of preparing stable cationic poly(lactic-co-glycolic acid) (PLGA) microspheres encapsulating the iron oxide nanoparticles (IONPs; 8-12 nm). The IONPs are incorporated into PLGA in organic phase followed by microsphere formation and chitosan coating in aqueous medium via nano-emulsion technique. The average size of the microspheres, as determined by dynamic light scattering are about 310 nm, while the zeta potential for the composite remains near 35 mV at pH 4.0. These microspheres are electrophoretically deposited onto indium tin oxide (ITO)-coated glass substrate used as cathode and parallel platinum plate as the counter electrode. This platform is utilized to fabricate a DNA biosensor, by immobilizing a probe sequence specific to Escherichia coli. The bioelectrode shows a surface-controlled electrode reaction with the electron transfer coefficient (α) of 0.64 and charge transfer rate constant (ks) of 61.73 s-1. Under the optimal conditions, this biosensor shows a detection limit of 8.7 × 10-14 M and is found to retain about 81% of the initial activity after 9 cycles of use. © 2013 The Royal Society of Chemistry.
Copper oxide assisted cysteine hierarchical structures for immunosensor application
(American Institute of Physics Inc., 2014) Chandra Mouli Pandey; Gajjala Sumana; Ida Tiwari
The present work describes the promising electrochemical immunosensing strategy based on copper (II) assisted hierarchical cysteine structures (CuCys) varying from star to flower like morphology. The CuCys having average size of 10 μm have been synthesised using L-Cysteine as initial precursor in presence of copper oxide under environmentally friendly conditions in aqueous medium. To delineate the synthesis mechanism, detailed structural investigations have been carried out using characterization techniques such as X-ray diffraction, transmission electron microscopy, and Fourier transform infrared spectroscopy. The electrochemical behaviour of self-assembled CuCys on gold electrode shows surface controlled electrode reaction with an apparent electron transfer rate constant of 3.38 × 10-4cm s-1. This innovative platform has been utilized to fabricate an immunosensor by covalently immobilizing monoclonal antibodies specific for Escherichia coli O157:H7 (E. coli). Under the optimal conditions, the fabricated immunosensor is found to be sensitive and specific for the detection of E. coli with a detection limit of 10 cfu/ml. © 2014 AIP Publishing LLC.
Electrochemical detection of a pathogenic Escherichia coli specific DNA sequence based on a graphene oxide-chitosan composite decorated with nickel ferrite nanoparticles
(Royal Society of Chemistry, 2015) Ida Tiwari; Monali Singh; Chandra Mouli Pandey; Gajjala Sumana
In this report, an electrochemical genosensor has been fabricated for Escherichia coli O157:H7 (E. coli) detection using a graphene oxide-nickel ferrite-chitosan (GO/NiF/ch) nanocomposite film as the sensing platform. The prepared GO/NiF/ch nanocomposite was characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy and thermo-gravimetric analysis. Nucleic acid hybridization technique was employed for the detection of a specific sequence of E. coli. The hybridization between the complementary DNA and probe DNA was investigated by differential pulse voltammetry (DPV) using methylene blue as redox indicator. The fabricated biosensor exhibits a linear response to complementary DNA in the concentration range of 10-6 to 10-16 M with a detection limit of 1 × 10-16 M. © The Royal Society of Chemistry.
Electrochemical genosensor based on carboxylated graphene for detection of water-borne pathogen
(Elsevier B.V., 2018) Nandita Jaiswal; Chandra Mouli Pandey; Amrita Soni; Ida Tiwari; Martin Rosillo-Lopez; Christoph G. Salzmann; Bansi Dhar Malhotra; Gajjala Sumana
This work reports the application of newly synthesized carboxylated graphene nanoflakes (Cx-Gnfs). The Cx-Gnfs were synthesized by wet chemical method in sulfuric acid/nitric acid mixture and was further electrophoretically deposited on indium tin oxide (ITO) coated glass substrates using Mg2+ ions which provides an overall charge to the materials for deposition onto the anode. The materials were characterized using SEM, TEM, contact angle, UV–vis spectroscopy, FT-IR, XRD and electrochemically characterized by cyclic voltammetry, chronocoulometry and electrochemical impedance spectroscopy. The sensitive quantitative determination of nucleic acid Escherichia coli O157: H7 (E. coli) has been achieved using Cx-Gnfs and r-GO as the sensing layer using electrochemical impedance spectroscopy. The electrochemical results reveal that the Cx-Gnfs based genosensor exhibits a linear response to complementary DNA (10−6 M to 10−17 M) with a detection limit of 1 × 10−17 M while the rGO based genosensor shows a detection limit of 1 × 10−15 M. Under optimal conditions, this Cx-Gnfs based genosensor was found to retain about 85% of its initial activity after being used for 6 times. © 2018 Elsevier B.V.
Electrochemical genosensor based on graphene oxide modified iron oxide-chitosan hybrid nanocomposite for pathogen detection
(Elsevier B.V., 2015) Ida Tiwari; Monali Singh; Chandra Mouli Pandey; Gajjala Sumana
In this report, a nucleic acid sensor has been fabricated via covalent immobilization of Escherichia coli O157:H7 (E. coli) specific probe oligonucleotide sequence, onto graphene oxide modified iron oxide-chitosan hybrid nanocomposite (GIOCh) film. The size of the GIOCh, as determined by dynamic light scattering and TEM, varies from 350 to 300 nm, while the zeta potential for the composite remains near 60 mV at pH 4.0. The prepared GIOCh are electrophoretically deposited onto indium tin oxide (ITO) coated glass substrate, used as cathode, while parallel platinum plate is used as counter electrode. The pDNA immobilized onto GIOCh/ITO electrode has been characterized using scanning electron microscopy; contact angle and Fourier transform infrared spectroscopy. Further, the electrochemical response studies carried out using electrochemical impedance spectroscopy reveals that this nucleic acid sensor exhibits a linear response to complementary DNA in the concentration range of 10-6-10-14 M with a detection limit of 1 × 10-14 M. Under optimal conditions, this biosensor is found to retain about 90% of the initial activity after 6 cycles of use. © 2014 Elsevier B.V. All rights reserved.
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.
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.
Hierarchical cystine flower based electrochemical genosensor for detection of Escherichia coli O157:H7
(Royal Society of Chemistry, 2014) Chandra Mouli Pandey; Ida Tiwari; Gajjala Sumana
This work reports on a facile and reproducible approach to synthesize novel organic flowers of cystine (CysFls) with high uniformity. These 3D flower-like structures have a purely hierarchical arrangement, wherein each petal is composed of several cystine molecules with an average size of 50 μM, as determined by transmission electron microscopy. The CysFls were self-assembled onto a gold electrode and were utilized as matrices for the covalent immobilization of an Escherichia coli O157:H7 (E. coli) specific probe oligonucleotide that was identified from the 16s rRNA coding region of the E. coli genome. This fabricated CysFl platform sought to provide improved fundamental characteristics to electrode interface in terms of electro-active surface area and diffusion coefficient. Electrochemical impedance spectroscopy revealed that this genosensor exhibits a linear response to complementary DNA in the concentration range of 10-6 to 10-15 M with a detection limit of 1 × 10-15 M. Under optimal conditions, this genosensor was found to retain about 88% of its initial activity after being used for 6 times. This journal is © the Partner Organisations 2014.
Highly sensitive electrochemical immunosensor based on graphene-wrapped copper oxide-cysteine hierarchical structure for detection of pathogenic bacteria
(Elsevier B.V., 2017) Chandra Mouli Pandey; Ida Tiwari; Vidya Nand Singh; K.N. Sood; Gajjala Sumana; Bansi Dhar Malhotra
We report results of the studies relating to fabrication of the graphene wrapped copper (II) assisted cysteine hierarchical structure (rGO-CysCu, 10 μm) synthesised using facile, aqueous and environmental-friendly conditions. The results of electrochemical impedance spectroscopic investigations indicate that self-assembly of rGO-CysCu molecules onto gold electrode provides a high surface area and high electron transfer rate constant (1.82 × 10−6 cm/s). Further, an ultrasensitive label-free electrochemical immunosensor for quantitative determination of Escherichia coli O157: H7 (E. coli) has been developed using rGO-CysCu as the sensing layer. Under optimal conditions, the calibration plot pertaining to sensing characteristics of the fabricated immunoelectrode for E. coli O157: H7 was approximately linear in the wide detection range of 10 CFU mL−1 to 108 CFU mL−1 with a detection limit of 3.8 CFU mL−1. Moreover, the proposed method was successfully used to differentiate the E. coli O157: H7 cells from the non-pathogenic E. coli (DH5α) and other bacterial cells in the synthetic samples. © 2016 Elsevier B.V.
Nanostructured palladium-reduced graphene oxide platform for high sensitive, label free detection of a cancer biomarker
(2014) Vinod Kumar; Saurabh Srivastava; Sima Umrao; Ram Kumar; Gopal Nath; Gajjala Sumana; Preeti S. Saxena; Anchal Srivastava
We report the results of studies related to the fabrication of a palladium nanoparticle decorated-reduced graphene oxide (Pd@rGO) based electrochemical immunosensor for the label free ultrasensitive detection of the prostate-specific antigen (PSA), a prostate cancer biomarker. The synergistic electrochemical activities of Pd and rGO result in an enhanced electron transfer used for the development of an ultrasensitive immunosensor. A facile approach was developed for the in situ synthesis of Pd@rGO using ascorbic acid as the reducing agent which enables the simultaneous reduction of both Pd+2 and GO into Pd nanoparticles and rGO, respectively. XRD, FTIR, SEM and TEM investigations were carried out to characterize the Pd@rGO material. A thin film of nanostructured Pd@rGO was electrophoretically deposited on an ITO coated glass electrode that was subsequently functionalized with anti-PSA antibodies. The electrochemical sensing results of the proposed immunosensor showed a high sensitivity {28.96 μA ml ng-1 cm-2}. The immunosensor is able to detect PSA at concentrations as low as 10 pg ml-1. The simple fabrication method, high sensitivity, good reproducibility and long term stability with acceptable accuracy in human serum samples are the main advantages of this immunosensor. © 2014 The Royal Society of Chemistry.
Nanostructuring of hierarchical 3D cystine flowers for high-performance electrochemical immunosensor
(Elsevier Ltd, 2014) Chandra Mouli Pandey; Gajjala Sumana; Ida Tiwari
Here, we report a simple and reproducible method for large scale fabrication of novel flower and palm-leaf like 3D cystine microstructures (CMs) with high uniformity having a size of 50μm and 10μm respectively, through a facile aqueous solution route as a function of pH and concentration. In a proof-of-concept study, the 3D CMs have been further explored to fabricate a label-free high-performance electrochemical immunosensor by immobilizing monoclonal antibodies. Electrochemical methods were employed to study the stepwise modification of the system and the electronic transduction for the detection. The fabricated immunosensor design demonstrates high performance with enhanced sensitivity (4.70 cfu ml-1) and linear sensing range from 10 to 3 x 109 cfu ml-1 a long shelf-life (35 days) and high selectivity over other bacterial pathogens. The enhanced performance originates from a novel nanostructuring in which the CMs provide higher surface coverage for the immobilization of antibodies providing excellent electronic/ionic conductivity which result in the enhanced sensitivity. © 2014 Elsevier B.V.
Protein conjugated carboxylated gold@reduced graphene oxide for aflatoxin B1 detection
(Royal Society of Chemistry, 2015) Saurabh Srivastava; Shiju Abraham; Chandan Singh; Md. Azahar Ali; Anchal Srivastava; Gajjala Sumana; Bansi D. Malhotra
A sensitive, reproducible, stable and label-free immunosensor has been prepared via simultaneous reduction of graphene oxide and gold(III) salt using an eco-friendly and non-toxic reducing agent sodium citrate resulting in uniformly distributed gold nanoparticles on reduced graphene oxide (rGO) sheets. The in situ grown gold@carboxylated reduced graphene oxide (Au@rGO) surface has been used for bioconjugation with monoclonal antibodies of aflatoxin B1 using EDC-NHS chemistry. The in situ growth of AuNPs (gold nanoparticles) onto the rGO sheet results in improved electrocatalytic activity and loading of the antibodies due to the enhanced surface area. The monodispersion of the Au nanoparticles on the rGO sheets yields heterogeneous electron transfer (2.85 × 10-4 cm s-1) resulting in improved biosensor efficacy compared to that based on the rGO electrode. This immunosensor is sensitive to detect as low as 0.1 ng mL-1 concentration of aflatoxin compared to the reported ELISA (enzyme-linked immunosorbent assay) standard method. The Au@rGO based immunosensor exhibits high sensitivity (182.4 μA (ng mL-1)-1 cm-2) in a wide linear detection range of 0.1-12 ng mL-1. Results of the studies related to this immunosensor reveal that the Au@rGO nanocomposite is a suitable platform for the development of a compact biosensing device for food toxin monitoring. © The Royal Society of Chemistry 2015.