Kavita Arora

Polyaniline Based Nucleic Acid Sensor

Twenty-bases long NH2-modified DNA and PNA probes specific to a pathogen (Mycobacterium tuberculosis) were covalently immobilized onto a polyaniline (PANI)/Au electrode to detect nucleic acid hybridization with complementary, one-base mismatch and noncomplementary targets within 30 s using Methylene Blue. The PNA-PANI/Au electrode exhibits improved specificity (1000 times) and detection limit (0.125 x 10(-18) M) as compared to that of the DNA-PANI/Au electrode (2.5 x 10(-18) M). These PNA-PANI/Au electrodes can be utilized for detection of hybridization with the complementary sequence in 5 min sonicated M. tuberculosis genomic DNA within 1 min of hybridization time. These DNA-PANI/Au and PNA-PANI/Au electrodes can be used 6-7 and 13-15 times, respectively.

STD sensor based on nucleic acid functionalized nanostructured polyaniline.

STD (sexually transmitted disease, Gonorrhoea) sensor based on nucleic acid probe (from Opa, a multi-copy gene of Neisseria gonorrhoeae) functionalized nanostructured-polyaniline coated onto indium-tin-oxide-coated glass plate has been fabricated using avidin-biotin as cross-linking agent. This DNA functionalized electrode can specifically detect upto 0.5 x 10(-15)M of complementary target within 60s of hybridization time at 25 degrees C by differential pulse voltammetry (DPV) using methylene blue as electro-active DNA hybridization indicator. This highly sensitive and specific nucleic acid functionalized nanostructured-polyaniline electrode can distinguish presence of N. gonorrhoeae from Neisseria meningitidis and Escherichia coli culture and spiked samples from the urethral swabs of the patients.

Graphene Oxide based Label Free Ultrasensitive Immunosensor for Lung Cancer Biomarker, hTERT

We report the fabrication of ultrasensitive Graphene Oxide (GO) based electrochemical immunosensor to detect human telomerase reverse transcriptase (hTERT), a lung cancer biomarker. The immuno-electrode-has been fabricated by covalent immobilization of rabbit anti-hTERT antibodies (Ab) onto GO films on ITO coated glass. The Fourier Transform Infrared (FTIR) spectroscopic studies confirms the presence of diverse organic functional groups (-COOH, -CHO, -OH) of GO, and the binding (anti-hTERT) onto GO/ITO electrode. Interestingly, Scanning Electron Micrographs (SEM) also reveals clear visual surface modification of the GO film by anti-hTERT antibodies and hTERT antigen (Ag). The electrochemical Differential Pulse Voltammetry (DPV) results show that the GO based immunosensor exhibits specificity and low detection upto 10 ag mL-1 (10×10-18 g mL-1) in wide detection range (10 ag mL-1-50 ng mL-1) for hTERT. The immunosensor showed ability to detect hTERT in spiked sputum samples upto 100 fg mL-1 in dynamic detection range of 100 fg mL-1-10 ng mL-1. The enhanced performance of Ab/GO/ITO is attributed to fast electron transfer and efficient loading of Ab on large surface area provided by GO network. The low level detection of hTERT warrants the realization of point-of-care device for early detection of lung/oral cancer through oral fluids

A secretory multifunctional serine protease, DegP of Plasmodium falciparum, plays an important role in thermo-oxidative stress, parasite growth and development

Plasmodium falciparum heat shock proteins and proteases are known for their indispensable roles in parasite virulence and survival in the host cell. They neutralize various host‐derived stress responses that are deleterious for parasite growth and invasion. We report identification and functional characterization of the first DegP from an apicomplexan (P. falciparum). To determine the molecular identity and functions of the parasite‐encoded DegP, we complemented the Escherichia coli degP null mutant with a putative PfdegP gene, and the results showed that PfDegP complements the growth defect of the temperature sensitive DegP‐deficient mutant and imparts resistance to non‐permissive temperatures and oxidative stress. Molecular interaction studies showed that PfDegP exists as a complex with parasite‐encoded heat shock protein 70, iron superoxide dismutase and enolase. DegP expression is significantly induced in parasite culture upon heat shock/oxidative stress. Our data suggest that the PfDegP protein may play a role in the growth and development of P. falciparum through its ability to confer protection against thermal/oxidative stress. Antibody against DegP showed anti‐plasmodial activity against blood‐stage parasites in vitro, suggesting that PfDegP and its associated complex may be a potential focus for new anti‐malarial therapies.

Anti-atrazine Functionalized Gold-nano Structures for Environmental Monitoring

Atrazine, a pesticide is a xenobiotic compound known to be a putative endocrine disruptor that may cause serious health risks even at very low levels. As per World Health Organization (WHO) the permissible limit of atrazine is restricted to 2 μg L-1 in drinking water and 0.02 -15 ppm (mg L-1) in food and it has been classified as Class 3a carcinogen as per IARC 2001. We report application of anti-atrazine based immune sensor for detection of atrazine using directly deposited gold nanostructures onto ITO glass slides for environmental monitoring. Non-toxic, simple and directly deposited gold nano structures (GNS-ITO) were characterized using cyclic voltammetry and UV visible absorption that showed characteristic absorption peak at ~559 nm confirming presence of 20-30 nm sized nano-structured hexagonal humps. Anti-atrazine has been covalently immobilized onto GNS-ITO and characterized using FT-IR spectroscopy, CV and SEM. Interestingly, SEM images reveals that the GNS grown on the surface are spherical and symmetrically distributed throughout the surface. Fabricated immune electrodes were used to sense atrazine through Square Wave Voltammetry and it was found to have dyanamic linear range from 50 aM - 1 nM (10.78 fg mL-1 - 215 pg mL-1) in 60 s antigen exposure time. Fabricated immune electrode was also shown to retain substantial stability till 12 weeks upon storage at 4°C in desiccated condition and showed no binding with non-specific antigens like malathion, parathion, 2-amino anthracene, albendazole etc. This system offers the potential for rapid, cost-effective immunosensing for the analysis of samples of environmental, medical and pharmaceutical significance.

Anti-IL8/AuNPs-rGO/ITO as an Immunosensing Platform for Noninvasive Electrochemical Detection of Oral Cancer

An efficient electrochemical transducer matrix for biosensing devices requires specific characteristics, such as fast electron transfer, stability, high surface area, biocompatibility, and presence of specific functional groups, to facilitate biomolecule attachment. We demonstrate the fabrication of an electrochemical immunosensor based on a highly stable gold nanoparticles-reduced graphene oxide (AuNPs-rGO) composite material as a transducer matrix for label-free and noninvasive detection of salivary oral cancer biomarker interleukin-8 (IL8). The synergy between rGO and AuNPs allowed the immunosensor to exhibit fast response and high sensitivity due to the improved electron transfer behavior of the composite. The immunosensor shows very fast detection (9 min) of IL8 and high sensitivity with an experimental linear dynamic range of 500 fg mL-1 to 4 ng mL-1 and a detection limit of 72.73 ± 0.18 pg mL-1. The fabricated immunosensor exhibits excellent specificity toward the detection of IL8 in human saliva samples. Furthermore, the reusability and stability up to 3 months of the immunosensor demonstrates the commercial potential of this nanoplatform for the detection of other biomarkers of clinical relevance.

Advances in Nano Based Biosensors for Food and Agriculture

Nanotechnology is revolutionizing development in almost all technological sectors, with applications in building materials, electronics, cosmetics, pharmaceuticals, food processing, food quality control and medicine. In particular, nano-based sensors use nanomaterials either as sensing material directly or as associated materials to detect specific molecular interactions occurring at the nano scale. Nano biosensors are used for clinical diagnostics, environmental monitoring, food and quality control. Nano biosensors can achieve on site, in situ and online measurements.