Carbon nanotubes — chitosan nanobiocomposite for immunosensor

Carboxylic group functionalized single walled (SW) and multi walled (MW) carbon nanotubes (CNT) have been incorporated into biopolymer matrix of chitosan (CH) to fabricate nanobiocomposite film onto indium– tin–oxide (ITO) coated glass plate for co-immobilization of rabbit-immunoglobulin (r-IgGs) and bovine serum albumin (BSA) to detect ochratoxin-A (OTA). The results of electrochemical studies reveal that presence of both CNT results in increased electro-active surface area of CH leading to enhanced electron transport in these nanobiocomposites. Moreover, in CH–SWCNT and CH–MWCNT nanobiocomposites the availability of NH2/OH group in CH and surface charged CNT also increases loading of the r-IgGs resulting in enhanced electron transport responsible for improved sensing characteristics. Compared to BSA/r-IgGs/CH– MWCNT/ITO immunoelectrode, electrochemical response studies of BSA/r-IgGs/CH–SWCNT/ITO immunoelectrode carried out as a function of OTA concentration exhibits improved linearity as 0.25–6 ng/dL, detection limit as 0.25 ng/dL, response time as 25 s, and sensitivity as 21 μA ng dL−1cm−2 with the regression coefficient as 0.998

A self assembled monolayer based microfluidic sensor for urea detection

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

Highly sensitive biofunctionalized nickel oxide nanowires for nanobiosensing applications

We report results of the studies relating to the fabrication of nickel oxide nanowires (NwNiOs) with an enhanced aspect ratio of similar to 100 for biosensing applications. Anti Vibrio cholerae monoclonal antibodies were used to functionalize the nickel oxide nanowire (20-80 nm) surfaces fabricated on indium tin oxide coated glass plate for Vibrio cholerae detection. The results of the impedance response studies conducted using this immunoelectrode as a function of the Vibrio cholerae concentration revealed a detection range of 37-350 ng ml(-1) and a low detection limit of 0.553 ng ml(-1) using the 3 sigma(b)/m criteria. The high sensitivity (11.12 Omega (ng ml(-1))(-1) cm(-2)) of this fabricated sensor is attributed to the excellent electronic properties of NiO nanowires which facilitate the efficient transfer of electrons between the electrode and the antibody molecules through electron channeling effects. Besides this, the nanostructured NiO nanowire based immunosensor exhibits interesting supercapacitive behaviour towards the detection of CT. This immunosensor showed values of association constant (K-a) of 4.5 x 10(7) ng ml(-1) and dissociation constant (K-d) of 2.22 x 10(-6) ng ml(-1)

Sol-gel derived nanostructured cerium oxide film for glucose sensor

Sol-gel derived nanostructured cerium oxide (CeO(2)) 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 CeO(2)/Au electrode and GOx/CeO(2)/Au bioelectrode. The response characteristics of the glucose bioelectrode (GOx/CeO(2)/Au) indicate linearity, detection limit and shelf-life as 50-400 mg/dL, 12.0 mu M, and 12 weeks, respectively. The value of apparent Michaelis-Menten constant (K(m)) of GOx/CeO(2)/Au bioelectrode has been found to be 13.55 mu M

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