We report the fabrication of potentiometric electrolyteinsulator capacitor (EISCAP) biosensors based on silicon and porous silicon (PS) substrates with oxide and stacked oxidenitride dielectrics. These biosensors have been calibrated for the detection and estimation of bioanalytes like tributyrin and urea, based on enzymatic reactions and have a linear detection range from 0.1 mM to 20 mM of the bioanalyte concentration. These improved sensitivity EISCAP sensors were used for the estimation of the total acid content in rancid butter, estimation of enzyme (Lipase) activity and to estimate total triglyceride levels in blood serum. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enakshi Bhattacharya

Department of Electrical Engineering

Anju Chadha

Department Of Biotechnology

Arun Mathew

ACID CONTENT

BIOANALYTES

BLOOD SERUM

DETECTION AND ESTIMATION

ENZYMATIC REACTION

LINEAR DETECTION

Novel applications

TRIBUTYRIN

TRIGLYCERIDE LEVELS

Biosensors

enzyme activity

ENZYME SENSORS

Estimation

signal transduction

urea

Porous silicon

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Physica Status Solidi (A) Applications and Materials Science

Electrolyte insulator semiconductor capacitors (EISCAPs) show a shift in the measured capacitance-voltage (C-V) characteristics with changes in the pH of the electrolyte and has the potential to be used as biosensors. The choice of an electrode to the EISCAP is important for reliable measurements. Here, we discuss a silicon-based EISCAP sensor bonded to a glass wafer with an embedded electrode. Three noble metal electrodes (Pt, Au, Ag) are studied for the ease of integration and performance and it is found that the chloridized Ag electrodes exhibit the highest pH sensitivity and the lowest electrode potential drift with time. A readout system that measures the pH of the electrolyte under test is developed and implemented in a programmable system on chip. Calibration of the EISCAP to account for sensor process variations is also incorporated. The pH measurement data on the miniaturized EISCAPs is presented. © 2001-2012 IEEE.

IEEE Sensors Journal

A miniaturized pH sensor with an embedded counter electrode and a readout circuit

A modified electrolyte-insulator-semiconductor-capacitor (EISCAP) developed in-house was used for the determination of triglycerides and urea in blood, in addition to urea in milk. The sensitivity of the sensor was 55 ± 0.5 mV per unit change of pH. The EISCAP was optimized to operate at 25 °C in 0.25 mM phosphate buffer (pH 6), 1 M KCl and 1 mg lipase for triglycerides and in 1 mM Tris-HCl buffer (pH 7.4), 0.5 M KCl and 0.5 U urease for urea. Comparisons of the results obtained from the developed biosensor and clinical records gave correlation coefficients of 0.979 and 0.974 for blood triglycerides and blood urea respectively. Similarly, estimation of milk urea determined using the sensor in comparison with the spectrophotometric method gave a correlation coefficient of 0.992. The sensor gave reproducible and reliable results up to six months. © 2011 Elsevier B.V. All rights reserved.

Sensors and Actuators, B: Chemical

Potentiometric estimation of blood analytes - Triglycerides and urea: Comparison with clinical data and estimation of urea in milk using an electrolyte-insulator-semiconductor-capacitor (EISCAP)

We report the fabrication of an electrolyte-insulator-semiconductor (EIS) device with an improved sensitivity brought about by texturization of the functionalized dielectric at the dielectric/electrolyte interface by electrostatic attachment of nanoparticle and mesoparticle. Improvement in sensitivities up to 42% over the nontextured (control) devices was obtained with SiO2 particles on SiO2 dielectric. The sensitivity was a function of the size of the particles with higher sensitivities being obtained with smaller particle sizes. The possible contributions of the chemical modification of the dielectric surface by the aminosilanes resulting in the modification of the surface charge, and of the physical modifications by particle texturization leading likely to enhancement of the surface densities of the active binding sites, were highlighted. A novel design for the EIS reservoir for possible improved circuit integration and manufacturability, involving a two-step reservoir in photoresist was demonstrated. This device was capable of characterizing sample volumes as small as 20 μL. A 2 × 1 and a 2 × 2 array was also demonstrated, which could be utilized for multianalyte detection. © 2014 IEEE.

Sensitivity enhancement of electrolyte-insulator-semiconductor sensors using mesotextured and nanotextured dielectric surfaces

We report fabrication of a potentiometric biosensor on silicon for the estimation of tributyrin and urea based on enzymatic reactions. The sensor is an electrolyte-insulator-semiconductor capacitor (EISCAP) that shows a shift in the measured C-V with changes in the pH of the electrolyte. This pH shift can be induced by the enzyme-mediated hydrolysis of tributyrin and urea which results in acidic and basic solutions, respectively and an EISCAP can be effectively used for the detection of these bioanalytes. A silicon nitride based EISCAP was used for the first time to detect triglycerides and urea. The sensor was able to detect millimolar concentrations of the bioanalytes (tributyrin/urea). The most important features of the tributyrin and urea sensor are high sensitivity, long life-time, easily built at a low cost, micro-construction and short response time. Optimization of the conditions for the enzymatic reaction and calibration of the sensor are included. © 2004 Elsevier B.V. All rights reserved.

Solid state potentiometric sensor for the estimation of tributyrin and urea

A novel, enzymatic, porous silicon (PS) based potentiometric method for estimating triglycerides is reported. Lipase, an enzyme, which hydrolyses triglycerides was immobilised on PS which was prepared from p-type (1 0 0) crystalline silicon and was thermally oxidized. On hydrolysis the triglycerides result in the formation of fatty acids which causes a change in the pH of the solution. Enzyme solution-oxidized PS-crystalline silicon structure was used to detect changes in pH during the hydrolysis of tributyrin as a shift in the capacitance-voltage (C-V) characteristics. Optimisation of the conditions for the enzymatic reaction and calibration of the sensor are included. © 2002 Elsevier Science B.V. All rights reserved.

Current Applied Physics

Estimation of triglycerides by a porous silicon based potentiometric biosensor

Ciência e Tecnologia de Alimentos

CARACTERÍSTICAS DE IDENTIDADE, QUALIDADE E ESTABILIDADE DA MANTEIGA DE GARRAFA: PARTE I -- CARACTERÍSTICAS DE IDENTIDADE E QUALIDADE

Sensors and Actuators B: Chemical

Capacitive microsensors for biochemical sensing based on porous silicon technology

Journal of Micromechanics and Microengineering

Protective coatings in harsh environments

Novel applications of silicon and porous silicon based EISCAP biosensors

Journal	Physica Status Solidi (A) Applications and Materials Science
ISSN	18626300
Open Access	No