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R Vaidya

Publications and source records attributed to R Vaidya.

11 recordsLinked to original sources
PubMed1995

Effect of interference on the performance of glucose enzyme electrodes using Nafion coatings.

The negatively charged perfluorinated ionomer Nafion was used as a coating on hydrogen peroxide detecting platinum electrode as well as on a polycarbonate diffusion membrane in the construction of a glucose amperometric enzyme electrode. The current response of these electrodes to hydrogen peroxide, ascorbic acid, acetaminophen, uric acid and glucose was studied and the coating procedure was optimized. It was confirmed that the Nafion coating prevents interference by anionic substances such as ascorbic acid and uric acid, and decreases acetaminophen interference. In this regard it was shown that coating the glucose diffusion membrane (polycarbonate) was more effective than coating the platinum wire itself, because of the prevention of the homogeneous redox reaction of the interference species with hydrogen peroxide, as well as the additional diffusional resistance to the glucose flux. The glucose levels in serum samples were estimated and the stability of the enzyme electrodes during continuous operation in serum was studied. An enzyme electrode with constant sensitivity of ca. 1 microA/mM and a linear range of up to 15 mM, unaffected by contact with serum, is reported.

Biosensing Techniques↗
PubMed1994

Use of charged membranes to control interference by body chemicals in a glucose biosensor.

The prerequisite for the continuous in vivo monitoring of glucose concentration is the development of an implantable glucose sensor with long-term stability. A new enzyme electrode concept featuring fluid-state glucose oxidase modified carbon powder along with a cross-linked glucose oxidase enzyme layer has been developed. The glucose sensor incorporating this enzyme electrode has been tested in vitro at 37 degrees C. It has a lifetime of three months after which it can be recharged with fresh enzyme. The next step in the characterization of this sensor is its in vitro behaviour in the presence of interfering substances commonly encountered in human blood. Here we report such a study of the sensor. The glucose diffusion membranes used were polycarbonate membranes. We used standard polycarbonate membranes (membranes treated with polyvinylpyrrolidone or PVP), PVP-free polycarbonate membranes, and standard polycarbonate membranes coated with positively and negatively charged hydrogel layers. The sensors showed a response to glucose concentrations < 300 mg dL-1, both in pure phosphate buffer and in the presence of interferences. The influence of ascorbic acid, bilirubin, creatinine, L-cystine, glycine, uric acid and urea on the amperometric signal of the sensor was investigated. The polycarbonate membrane coated with the negatively charged hydrogel layer provided good protection for the enzyme electrode, especially in the presence of ascorbic acid and uric acid.

Biosensing Techniques↗
PubMed1979

Serum gonadotropins and testosterone in infertile patients with varicocele.

Serum concentrations of gonadotropins and testosterone in 25 infertile men with varicocele were compared with those in control men and men with idiopathic oligo-azoospermia. No significant difference was found in values of serum follicle-stimulating hormone (FSH) (14.9 +/- 13.6 mIU/ml), luteinizing hormone (LH) (24.9 +/- 19.1 mIU/ml), and testosterone (5.0 +/- 2.1 ng/ml) when the group with varicocele was compared with either the control group (FSH, 7.0 +/- 3.2 mIU/ml; LH, 23.6 +/- 16.0 mIU/ml; testosterone, 5.3 +/- 1.8 ng/ml) or the group with idiopathic oligo-azoospermia (FSH, 23.0 +/- 22.69 mIU/ml; LH, 36.7 +/- 24.1 mIU/ml; testosterone, 5.31 +/- 2.3 ng/ml). However, compared with the control group, there was a significant elevation of serum FSH levels in patients with varicocele whose testicular biopsy score counts were between 1 and 4. The importance of preoperative determination of the serum FSH level is discussed.

Biopsy↗