Bhawna Batra

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.

Determination of lactic acid with special emphasis on biosensing methods: A review.

Lactic acid (2-Hydroxypropanoic acid) is generated from pyruvic acid under anaerobic condition in skeletal muscles, brain, red blood cells, and kidney. Lactate in normal human subjects get cleared very quickly at a rate of 320mmol/L/hr, mostly by liver metabolism and re-conversion of lactate back to pyruvate. Measurement of lactate level in serum is required for the differential diagnosis and medical management of hyperlactatemia, cardiac arrest and resuscitation, sepsis, reduced renal excretion, hypoxia induced cancer, decreased extra hepatic metabolism, intestinal infarction and lactic acidosis. Determination of lactate is also important in dairy products and beverages to access their quality. Among the various methods available for detection of lactate, most are complicated, nonspecific, less sensitive and require time-consuming sample pretreatment, expensive instrumental set-up and trained persons to operate, specifically for chromatographic methods. Biosensing methods overcome these drawbacks, as these are simple, fast, specific and highly sensitive. Lactate biosensors reported so far, work optimally within 3-180s, between pH, 5.5-8.5 and temperature 22°C to 37°C and lactate concentration ranging from 10 to 2000µM. These biosensors have been employed to measure lactate level in embryonic cell culture, beverages, urine, and serum samples and reused upto 200-times within a period of 7-216 days. This review presents the principles, merits and demerits of various analytical methods for lactate determination with special emphasis on lactate biosensors. The future perspective for improvement of analytic performance of lactate biosensors are discussed.

Construction of glutamate biosensor based on covalent immobilization of glutmate oxidase on polypyrrole nanoparticles/polyaniline modified gold electrode

A method is described for construction of a highly sensitive electrochemical biosensor for detection of glutamate. The biosensor is based on covalent immobilization of glutamate oxidase (GluOx) onto polypyrrole nanoparticles and polyaniline composite film (PPyNPs/PANI) electrodeposited onto Au electrode. The enzyme electrode was characterized by cyclic voltammetry (CV), scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infra-red spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS). The biosensor showed optimum response within 3s at pH 7.5 (0.1 M sodium phosphate) and 35 °C, when operated at 50 mV s⁻¹. It exhibited excellent sensitivity (detection limit as 0.1 nM), fast response time and wider linear range (from 0.02 to 400 μM). Analytical recovery of added glutamate (5 mM and 10 mM) was 95.56 and 97%, while within batch and between batch coefficients of variation were 3.2% and 3.35% respectively. The enzyme electrode was used 100 times over a period of 60 days, when stored at 4 °C. The biosensor measured glutamate level in food stuff, which correlated well with a standard colorimetric method (r=0.99).

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.

An amperometric lactate biosensor based on lactate dehydrogenase immobilized onto graphene oxide nanoparticles‐modified pencil graphite electrode

A novel amperometric lactate biosensor was developed based on immobilization of lactate dehydrogenase onto graphene oxide nanoparticles‐decorated pencil graphite electrode. The enzyme electrode was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), and cyclic voltammetry at different stages of its construction. The biosensor showed optimum response within 5 s at pH 7.3 (0.1 M sodium phosphate buffer) and 35°C, when operated at 0.7 V. The biosensor exhibited excellent sensitivity (detection limit as low as 0.1 μM), fast response time (5 s), and wider linear range (5–50 mM). Analytical recovery of added lactic acid in serum was between 95.81–97.87% and within‐batch and between‐batch coefficients of variation were 5.04 and 5.40%, respectively. There was a good correlation between serum lactate values obtained by standard colorimetric method and the present biosensor (r = 0.99). The biosensor measured lactate levels in sera of apparently healthy subjects and persons suffering from lactate acidosis and other biological materials (milk, curd, yogurt, beer, white wine, and red wine). The enzyme electrode lost 25% of its initial activity after 60 days of its regular uses, when stored dry at 4°C.