Ravindra P. Singh

Application of peptide nucleic acid towards development of nanobiosensor arrays.

Peptide nucleic acid (PNA) is the modified DNA or DNA analogue with a neutral peptide backbone instead of a negatively charged sugar phosphate. PNA exhibits chemical stability, resistant to enzymatic degradation inside living cell, recognizing specific sequences of nucleic acid, formation of stable hybrid complexes like PNA/DNA/PNA triplex, strand invasion, extraordinary thermal stability and ionic strength, and unique hybridization relative to nucleic acids. These unique physicobiochemical properties of PNA enable a new mode of detection, which is a faster and more reliable analytical process and finds applications in the molecular diagnostics and pharmaceutical fields. Besides, a variety of unique characteristic features, PNAs replace DNA as a probe for biomolecular tool in the molecular genetic diagnostics, cytogenetics, and various pharmaceutical potentials as well as for the development of sensors/arrays/chips and many more investigation purposes. This review paper discusses the various current aspects related with PNAs, making a new hot device in the commercial applications like nanobiosensor arrays.

Analysis of direct immobilized recombinant protein G on a gold surface

For the immobilization of IgG, various techniques such as chemical linker, thiolated protein G methods, and fragmentation of antibodies have been reported [Y.M. Bae, B.K. Oh, W. Lee, W.H. Lee, J.W. Choi, Biosensors Bioelectron. 21 (2005) 103; W. Lee, B.K. Oh, W.H. Lee, J.W. Choi, Colloids Surf. B-Biointerfaces, 40 (2005) 143; A.A. Karyakin, G.V. Presnova, M.Y. Rubtsova, A.M. Egorov, Anal. Chem. 72 (2000) 3805]. Here, we modified the immunoglobulin Fc-binding B-domain of protein G to contain two cysteine residues at its C-terminus by a genetic engineering technique. The resulting recombinant protein, RPGcys, retained IgG-binding activity in the same manner as native protein G. RPGcys was immobilized on a gold surface by strong affinity between thiol of cysteine and gold. The orientations of both IgG layers immobilized on the base recombinant protein Gs were analyzed by fluorescence microscope, atomic force microscope (AFM), and surface plasmon resonance (SPR). Our data revealed that IgG-binding activity of RPGcys on gold surface significantly increased in comparison to wild type of protein G (RPGwild), which was physically adsorbed due to absence of cysteine residue. Immobilization of highly oriented antibodies based on cysteine-modified protein G could be useful for the fabrication of immunosensor systems.

Silver nanosieve using 1,2-benzenedicarboxylic acid: a sensor for detection of hydrogen peroxide

A novel approach for the preparation of a well-ordered nanosieve structure of silver nanoparticles using a Ag-1,2-benzenedicarboxylate (Ag-1,2-BDC) complex and sodium stearate under a hydrothermal process was performed. The X-ray diffraction (XRD) pattern suggests the formation and crystallinity of silver nanoparticles. The average particle size of silver nanoparticles was 35 nm and shows a hexagonal shape with a nanosieve structure as confirmed by transmission electron microscopy (TEM). The selective area electron diffraction (SAED) pattern of the nanosieve suggests a mono-crystalline nature of the silver nanoparticles. The SEM image reveals that the particles are of spherical and granular nature. The UV-Vis absorption spectrum shows a characteristic absorption peak of silver nanoparticles at 410 nm. The findings suggest that hydrothermal induced assembly should be a convenient and effective route for the preparation of new silver nanostructures. In addition, the Ag nanosieve modified electrode (AgNS/GC) exhibited an excellent electrocatalytic activity toward the reduction of hydrogen peroxide (H2O2). This silver nanosieve may also be a promising candidate for electronics and photonics application.

Direct immobilization of cupredoxin azurin modified by site-directed mutagenesis on gold surface.

For making efficient bioelectronic device, we have developed novel immobilization method of cupredoxin azurin modified on gold (Au) surface. A recombinant protein with cysteine residue by using site-directed mutagenesis was designed and then directly immobilized on Au surface without any chemical linker. The immobilization of the functionalized protein is confirmed by surface plasmon resonance (SPR) and its surface morphology is analyzed by scanning tunneling microscopy (STM). The immobilization efficiency has been increased about 75.6%, as compared to that of wild-type azurin. The electrochemical property of the fabricated thin film was investigated by the cyclic voltammetry (CV). As a result, cysteine-modified azurin can be used for making high-quality protein film, and applied to the fabrication of nano-scale bioelectronics.

Smart Nanomaterials for Biosensors, Biochips and Molecular Bioelectronics

The domain of biology has greatly been benefited by advances in other sciences leading to new levels of sensitivity, precision and resolution in biomolecular detection. The key driving force is the ...