Anees A. Ansari

Zinc oxide nanoparticles-chitosan composite film for cholesterol biosensor.

Zinc oxide nanoparticles (NanoZnO) uniformly dispersed in chitosan (CHIT) have been used to fabricate a hybrid nanocomposite film onto indium-tin-oxide (ITO) glass plate. Cholesterol oxidase (ChOx) has been immobilized onto this NanoZnO-CHIT composite film using physiosorption technique. Both NanoZnO-CHIT/ITO electrode and ChOx/NanoZnO-CHIT/ITO bioelectrode have been characterized using Fourier transform-infrared (FTIR), X-ray diffraction (XRD), cyclic voltammetry (CV), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) techniques, respectively. The ChOx/NanoZnO-CHIT/ITO bioelectrode exhibits linearity from 5 to 300 mg dl(-1) of cholesterol with detection limit as 5 mg dl(-1), sensitivity as 1.41x10(-4) A mg dl(-1) and the value of Michaelis-Menten constant (K(m)) as 8.63 mg dl(-1). This cholesterol biosensor can be used to estimate cholesterol in serum samples.

Sol-gel derived nanostructured cerium oxide film for glucose sensor

Sol-gel derived nanostructured cerium oxide (CeO2) film deposited on gold (Au) electrode has been utilized for physisorption of glucose oxidase (GOx). X-ray diffraction, atomic force microscopy, UV-visible spectroscopy, and electrochemical techniques have been used to characterize sol-gel derived CeO2∕Au electrode and GOx∕CeO2∕Au bioelectrode. The response characteristics of the glucose bioelectrode (GOx∕CeO2∕Au) indicate linearity, detection limit and shelf-life as 50–400mg∕dL, 12.0μM, and 12weeks, respectively. The value of apparent Michaelis–Menten constant (Km) of GOx∕CeO2∕Au bioelectrode has been found to be 13.55μM.

Hydrogen peroxide sensor based on horseradish peroxidase immobilized nanostructured cerium oxide film

Nanostructured cerium oxide (NanoCeO(2)) film deposited onto indium-tin-oxide (ITO) glass substrate by solution casting has been used for immobilization of horseradish peroxidase (HRP) via physiosorption technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-vis and electrochemical techniques have been utilized for characterization of NanoCeO(2)/ITO electrode and HRP/NanoCeO(2)/ITO bioelectrode. The HRP/NanoCeO(2)/ITO electrode exhibits value of the apparent Michaelis-Menten constant (K(m)) as 2.21 microM, linear regression coefficient as 0.998 and linearity for hydrogen peroxide as 1.0-170 microM obtained using electrochemical response measurements. Besides this, HRP/NanoCeO(2)/ITO bioelectrode can be used about 20 times and is stable for 5 weeks at 4 degrees C. The results of photo-response studies carried out on HRP/NanoCeO(2)/ITO bioelectrode indicate reasonable agreement with those obtained using amperometric technique.

A nanostructured cerium oxide film-based immunosensor for mycotoxin detection

Rabbit-immunoglobulin antibodies (r-IgGs) and bovine serum albumin (BSA) have been immobilized onto sol-gel-derived nanostructured cerium oxide (nanoCeO(2)) film fabricated onto an indium-tin-oxide (ITO) coated glass plate to detect ochratoxin-A (OTA). Broad reflection planes obtained in x-ray diffraction (XRD) patterns reveal the formation of CeO(2) nanostructures. Electrochemical studies reveal that nanoCeO(2) particles provide an increased electroactive surface area for loading of r-IgGs with desired orientation, resulting in enhanced electron communication between r-IgGs and electrode. BSA/r-IgGs/nano CeO(2)/ITO immunoelectrode exhibits improved characteristics such as linear range (0.5-6 ng dl(-1)), low detection limit (0.25 ng dl(-1)), fast response time (30 s) and high sensitivity (1.27 microA ng(-1) dl(-1) cm(-2)). The high value of the association constant (K(a), 0.9 x 10(11) l mol(-1)) indicates the high affinity of the BSA/r-IgGs/nanoCeO(2)/ITO immunoelectrode to OTA.

Nanostructured zinc oxide platform for cholesterol sensor

Nanostructured zinc oxide (nano-ZnO) film has been fabricated onto indium tin oxide (ITO) containing preferred (002) plane and 10 nm crystallite size using sol-gel technique for immobilization of cholesterol oxidase (ChOx). Electrochemical response of ChOx/nano-ZnO/ITO bioelectrode determined as a function of cholesterol concentration using cyclic voltammetry technique reveals improved detection range (5–400 mg/dl), low detection limit (0.5 mg/dl), fast response time (10 s), sensitivity (0.059 μA/mg dl−1 cm−2), and low value (0.98 mg/dl) of Michaelis–Menten constant (Km). It is shown that nano-ZnO film provides better environment and enhanced electron transfer between ChOx and electrode.

Nanostructured zinc oxide platform for mycotoxin detection

Nanostructured zinc oxide (Nano-ZnO) film has been deposited onto indium-tin-oxide (ITO) glass plate for co-immobilization of rabbit-immunoglubin antibodies (r-IgGs) and bovine serum albumin (BSA) for ochratoxin-A (OTA) detection. The results of X-ray diffraction (XRD) studies reveal the formation of Nano-ZnO with average particle size as ~5.0nm. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) techniques have been used to characterize Nano-ZnO/ITO electrode and BSA/r-IgGs/Nano-ZnO/ITO immunoelectrode. Electrochemical impedimetric response of BSA/r-IgGs/Nano-ZnO/ITO immunoelectrode obtained as a function of OTA concentration exhibits linearity as 0.006-0.01nM/dm(3), detection limit of 0.006nM/dm(3), response time as 25s and sensitivity of 189Omega/nM/dm(3)cm(-2) with a regression coefficient of 0.997.

Zinc oxide-chitosan nanobiocomposite for urea sensor

Zinc oxide (ZnO)-chitosan (CH) nanobiocomposite film onto indium-tin-oxide (ITO) coated glass has been used to immobilize urease (Urs) and glutamate dehydrogenase (GLDH) for urea detection. The presence of ZnO nanoparticles in CH results in its increased surface area and enhanced electron transfer kinetics. The Urs-GLDH/CH-ZnO/ITO bioelectrode characterized using electrochemical, Fourier transform infrared, and scanning electron microscopy studies exhibit linearity of 5–100mg∕dl, detection limit of 3mg∕dl, response time of 10s, reproducibility as 20 times, and shelf life of 3months. The low Michaelis–Menten constant (Km) value (4.92mg∕dl) indicates enhanced affinity of enzyme with nanobiocomposite.

Luminescent mesoporous LaVO4:Eu3+ core-shell nanoparticles: synthesis, characterization, biocompatibility and their cytotoxicity

A general and facile method was used for preparation of water-soluble silica coated LaVO4:Eu3+ core-shell nanoparticles. In the present study, we have discussed and compared the cytotoxicity characteristics of the synthesized LaVO4:Eu3+ and silica coated LaVO4:Eu3+ core-shell nanoparticles. X-ray diffraction (XRD), field-emission transmission electron microscopy (FE-TEM), energy dispersive X-ray analysis (EDX), Fourier-transform infrared spectroscopy (FTIR), UV/Vis absorption spectroscopy and photoluminescence spectroscopic techniques were employed to characterize the structure and morphology of the prepared products. To obtain high aqueous solubility, luminescent LaVO4:Eu3+ nanoparticles were encapsulated with silica groups, giving the nanoparticles a negatively charged surface at physiological pH. The results of XRD confirm the formation of a well-crystallized LaVO4:Eu3+ phase with a tetragonal zircon structure. Optical absorption spectra show that the optical properties of silica-coated LaVO4:Eu3+ core-shell nanoparticles are related to their sizes and shapes. Further, in order to assess cytotoxicity, we investigated whether the LaVO4:Eu3+ nanoparticles could alter biological samples once they enter human H522 and peripheral blood mono nuclear cells (PBMCs). An MTT assay was performed to measure the mitochondrial activity that reflects the number of viable cells. Silica coated LaVO4:Eu3+ core-shell nanoparticles exhibited no significant effect on the viability of both types of cells up to 24 h after exposure. Strikingly, no dose effects were detected, even at highest concentrations.

Hydrothermal Growth of Vertically Aligned ZnO Nanorods Using a Biocomposite Seed Layer of ZnO Nanoparticles

Well aligned ZnO nanorods have been prepared by a low temperature aqueous chemical growth method, using a biocomposite seed layer of ZnO nanoparticles prepared in starch and cellulose bio polymers. The effect of different concentrations of biocomposite seed layer on the alignment of ZnO nanorods has been investigated. ZnO nanorods grown on a gold-coated glass substrate have been characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. These techniques have shown that the ZnO nanorods are well aligned and perpendicular to the substrate, and grown with a high density and uniformity on the substrate. Moreover, ZnO nanorods can be grown with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a dominant (002) peak in an XRD spectrum and possessed a high crystal quality. A photoluminescence (PL) spectroscopy study of the ZnO nanorods has revealed a conventional near band edge ultraviolet emission, along with emission in the visible part of the electromagnetic spectrum due to defect emission. This study provides an alternative method for the fabrication of well aligned ZnO nanorods. This method can be helpful in improving the performance of devices where alignment plays a significant role.

Nanomaterials as Analytical Tools for Genosensors

Nanomaterials are being increasingly used for the development of electrochemical DNA biosensors, due to the unique electrocatalytic properties found in nanoscale materials. They offer excellent prospects for interfacing biological recognition events with electronic signal transduction and for designing a new generation of bioelectronic devices exhibiting novel functions. In particular, nanomaterials such as noble metal nanoparticles (Au, Pt), carbon nanotubes (CNTs), magnetic nanoparticles, quantum dots and metal oxide nanoparticles have been actively investigated for their applications in DNA biosensors, which have become a new interdisciplinary frontier between biological detection and material science. In this article, we address some of the main advances in this field over the past few years, discussing the issues and challenges with the aim of stimulating a broader interest in developing nanomaterial-based biosensors and improving their applications in disease diagnosis and food safety examination.