Suman Lata

Construction of an amperometric bilirubin biosensor based on covalent immobilization of bilirubin oxidase onto zirconia coated silica nanoparticles/chitosan hybrid film.

A method is described for the construction of a highly sensitive electrochemical biosensor for the detection of bilirubin. The sensor is based on covalent immobilization of bilirubin oxidase (BOx) onto zirconia coated silica nanoparticles (SiO2@ZrONPs)/chitosan (CHIT) composite electrodeposited onto Au electrode. The enzyme electrode was characterized by scanning electron microscopy (SEM), Fourier transform infra-red spectroscopy (FTIR), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The biosensor showed optimum response within 2s at pH 8.5 (0.1M Tris-HCl) and 35°C, when operated at 20 mV s(-1). The biosensor exhibited excellent sensitivity (detection limit as 0.1 nM), fast response time and wider linear range (from 0.02 to 250 μM). Analytical recovery of added bilirubin was 95.56-97.0%. Within batch and between batch coefficients of variation were 3.2% and 3.35% respectively. The enzyme electrode was used 150 times over a period of 120 days, when stored at 4°C. The biosensor measured bilirubin levels in sera of apparently healthy and persons suffering from jaundice, which correlated well with a standard colorimetric method (r=0.99).

An acrylamide biosensor based on immobilization of hemoglobin onto multiwalled carbon nanotube/copper nanoparticles/polyaniline hybrid film

A method is described for the construction of a highly sensitive electrochemical biosensor for the detection of acrylamide, based on covalent immobilization of hemoglobin (Hb) onto carboxylated multiwalled carbon nanotube/copper nanoparticle/polyaniline (c-MWCNT/CuNP/PANI) composite electrodeposited onto pencil graphite (PG) electrode. The enzyme electrode was characterized by cyclic voltammetry (CV), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and electrochemical impedance spectroscopy (EIS). The biosensor showed an optimal response at pH 5.5 (0.1 M sodium acetate buffer) and 35 °C when operated at 20 mV s(-1). The biosensor exhibited low detection limit (0.2 nM) with high sensitivity (72.5 μA/nM/cm(2)), fast response time (<2 s), and wide linear range (5 nM to 75 mM). Analytical recovery of added acrylamide was 95.40 to 97.56%. Within- and between-batch coefficients of variation were 2.35 and 4.50%, respectively. The enzyme electrode was used 120 times over a period of 100 days, when stored at 4 °C.

Construction of an amperometric d-amino acid biosensor based on d-amino acid oxidase/carboxylated mutliwalled carbon nanotube/copper nanoparticles/polyalinine modified gold electrode

An improved D-amino acid biosensor was constructed based on covalent immobilization of D-amino acid oxidase onto carboxylated mutliwalled carbon nanotube/copper nanoparticles/polyalinine hybrid film electrodeposited on gold electrode. The biosensor exhibited an optimal response within 2s at pH 8.0 and 30°C when polarized at 0.09 V. There was a linear relationship between biosensor response (μA) and D-alanine concentration ranging from 0.001 to 0.7 mM. The sensitivity of the biosensor was 54.85 μA cm(-2) mM(-1) with a lower limit of detection of 0.2 μM (signal/noise=3). The enzyme electrode was used 150 times over a period of 4 months. The biosensor measured the d-amino acid level in fruit juices.

Biosensors for determination of D and L- amino acids: A review

Amino acids (AAs) of nutritional importance exist as L-isomers, while D-isomeric form of AAs is common constituent of bacterial cell wall. The presence of D-amino acids in foods is promoted by harsh technological processes (e.g., high temperature, extreme pH, adulteration or microbial contamination). The detection of free AAs in different brain disorders is also very important. Among the various methods available for detection of AAs, most are complicated and require time-consuming sample pre-treatment, expensive instrumental set-up and trained persons to operate, specifically for chromatographic methods. The biosensing methods overcome these drawbacks, as these are simple, fast, specific and highly sensitive and can also be applied for detection of AAs in vivo. This review presents the principles, merits and demerits of various analytical methods for AA determination with special emphasis on D-amino acids (DAA) and L-amino acids (LAA) biosensors. The electrochemical AA biosensors work optimally within 2-900 s, pH range, 5.3-9.5; temperature range, 25-45 °C; AA concentration range, 0.0008-8000 mM, limit of detection(LOD) between 0.02 and 1250 µM and working potential from -0.05 to 0.45 V. These biosensors measured AA level in fruit juices, beverages, urine, sera and were reused 200 times over a period of 7-120 days. The use of various nanostructures and electrochemical microfluidic paper based analytical device (EμPAD) are suggested for further development of AA biosensors.