Impedimetric genosensor for detection of hepatitis C virus (HCV1) DNA using viral probe on methylene blue doped silica nanoparticles.

An impedimetric genosensor was fabricated for detection of hepatitis C virus (HCV) genotype 1 in serum, based on hybridization of the probe with complementary target cDNA from sample. To achieve it, probe DNA complementary to HCVgene was immobilized on the surface of methylene blue (MB) doped silica nanoparticles MB@SiNPs) modified fluorine doped tin oxide (FTO) electrode. The synthesized MB@SiNPs was characterized using scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) pattern. This modified electrode (ssDNA/MB@SiNPs/FTO) served both as a signal amplification platform (due to silica nanoparticles (SiNPs) as well as an electrochemical indicator (due to methylene blue (MB)) for the detection of the HCV DNA in patient serum sample. The genosensor was optimized and evaluated. The sensor showed a dynamic linear range 100-106 copies/mL, with a detection limit of 90 copies/mL. The sensor was applied for detection of HCV in sera of hepatitis patient and could be renewed. The half life of the sensor was 4 weeks. The MB@SiNPs/FTO electrode could be used for preparation of other gensensors also.

Construction of an improved amperometric acrylamide biosensor based on hemoglobin immobilized onto carboxylated multi-walled carbon nanotubes/iron oxide nanoparticles/chitosan composite film.

A method is described for construction of an improved amperometric acrylamide biosensor based on covalent immobilization of hemoglobin (Hb) onto nanocomposite of carboxylated multi-walled carbon nanotubes (cMWCNT) and iron oxide nanoparticles (Fe3O4NPs) electrodeposited onto Au electrode through chitosan (CHIT) film. The Hb/cMWCNT-Fe3O4NP/CHIT/Au electrode was characterized by scanning electron microscopy, Fourier transform infra-red spectroscopy, electrochemical impedance spectroscopy, and differential pulse voltammetry at different stages of its construction. The biosensor was based on interaction between acrylamide and Hb, which led to decrease in the electroactivity of Hb, i.e., current generated during its reversible conversion [Fe(II)/Fe(III)]. The biosensor showed optimum response within 8 s at pH 5.0 and 30 °C. The linear working range for acrylamide was 3-90 nM, with a detection limit of 0.02 nM and sensitivity of 36.9 µA/nM/cm(2). The biosensor was evaluated and employed for determination of acrylamide in potato crisps.

An amperometric biosensor based on laccase immobilized onto Fe3O4NPs/cMWCNT/PANI/Au electrode for determination of phenolic content in tea leaves extract.

A method is described for the construction of an amperometric biosensor for detection of phenolic compounds based on covalent immobilization of laccase onto iron oxide nanoparticles (Fe3O4NPs) decorated carboxylated multiwalled carbon nanotubes (cMWCNTs)/polyaniline (PANI) composite electrodeposited onto a gold (Au) electrode. The modified electrode was characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The biosensor showed optimum response within 3s at pH 6.0 (0.1 M sodium acetate buffer) and 35°C, when operated at 0.3 V vs. Ag/AgCl. Linear range, detection limit were 0.1-10 µM (lower concentration range) and 10-500 µM (higher concentration range), and 0.03 µM respectively. The sensor measured total phenolic content in tea leaves extract. The enzyme electrode lost 25% of its initial activity after its 150 uses over a period of 4 months, when stored at 4°C.

Polyphenol biosensor based on laccase immobilized onto silver nanoparticles/multiwalled carbon nanotube/polyaniline gold electrode.

Laccase purified from Ganoderma sp. was immobilized covalently onto electrochemically deposited silver nanoparticles (AgNPs)/carboxylated multiwalled carbon nanotubes (cMWCNT)/polyaniline (PANI) layer on the surface of gold (Au) electrode. A polyphenol biosensor was fabricated using this enzyme electrode (laccase/AgNPs/cMWCNT/PANI/Au electrode) as the working electrode, Ag/AgCl as the reference electrode, and platinum (Pt) wire as the auxiliary electrode connected through a potentiostat. The biosensor showed optimal response at pH 5.5 (0.1 M acetate buffer) and 35°C when operated at a scan rate of 50 mV s(-1). Linear range, response time, and detection limit were 0.1-500 µM, 6 s, and 0.1 µM, respectively. The sensor was employed for the determination of total phenolic content in tea, alcoholic beverages, and pharmaceutical formulations. The enzyme electrode was used 200 times over a period of 4 months when stored at 4°C. The biosensor has an advantage over earlier enzyme sensors in that it has no leakage of enzyme during reuse and is unaffected by the external environment due to the protective PANI microenvironment.

Comparative study of performances of lipase immobilized asymmetric polysulfone and polyether sulfone membranes in olive oil hydrolysis.

In the present study, lipase was immobilized via glutaraldehyde crosslinking on the polysulfone and polyether sulfone asymmetric membranes. The results indicated that the overall immobilization of lipase is related to the hydrophobicity of the membrane material and thus higher immobilization is achieved for polysulfone membrane. The evidence of immobilization is done by XRD, SEM, contact angle and porometric studies. Hydrolytic activity of lipase in immobilized form is determined by hydrolyzing olive oil and compared with hydrolytic activity of free lipase. The effect of different reaction parameters viz., temperature, pH, substrate concentration, and incubation time on the lipase activity is investigated. The observed maximum reaction rate (V(max)) and Michaelis-Menten constant (K(m)) of polysulfone and polyether sulfone is determined.

Immobilization of sorghum leaf oxalate oxidase onto alkylamine and arylamine glass.

An oxalate oxidase (EC 1.2.3.4) purified from grain sorghum leaves was immobilized onto alkylamine and arylamine glass beads through glutaraldehyde coupling and diazotization with a conjugation yield of 10.8 mg/g support and 9.2 mg/g support, respectively. The enzyme retained 67.5% and 34.1% of its initial specific activity after immobilization onto alkylamine and arylamine glass, respectively. The enzyme exhibited an increase in optimum pH, temperature for maximum activity, energy of activation (Ea) and time for linearity but decrease in thermal stability at 60 degrees C after immobilization on both types of beads. The K(m) value for oxalate was increased by 9- to 10-fold but Vmax remained unaltered after immobilization. Both alkyl and arylamine glass bound enzyme was unaffected by physiological concentrations of Cl- and NO3-. The analytic importance of this work is demonstrated.