This paper reports on the design and fabrication of electrolyte insulator semiconductor capacitor (EISCAP) devices to detect triglycerides in the form of microreactors fabricated by bulk micromachining of silicon. We have developed a complete triglyceride biochip wherein the enzyme for hydrolysis and the counter electrode for signal transduction are integrated with a miniaturised EISCAP sensor. A compact readout system that measures the triglyceride concentration in blood serum under test has been developed and is implemented in a Programmable System on Chip (PSoC®). The miniaturised EISCAP devices are tested using blood serum samples to estimate the triglyceride concentration within the clinical range of 50 to 150 mg dL-1 and the time taken by the readout system to calibrate the sensor and to measure the triglyceride is less than 5 minutes. © The Royal Society of Chemistry 2014.

Anju Chadha

Department Of Biotechnology

Enakshi Bhattacharya

Department of Electrical Engineering

Mohanasundaram Sulur Veeramani

Prakash Shyam

Noel Prashant Ratchagar

BLOOD SERUM

BULK- MICROMACHINING

COMPACT READOUTS

Counter electrodes

ELECTROLYTE INSULATOR SEMICONDUCTORS

MICRO REACTOR

PROGRAMMABLE SYSTEM ON CHIPS

SILICON BIOSENSORS

Biochips

ENZYME ELECTRODES

Readout systems

Sensors

signal transduction

Silicon

blood

Fulltext

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

Analytical Methods

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

Electrolyte Insulator Semiconductor Capacitor (El S CAP) is a transducer that can detect triglycérides (TGs) in blood serum through an enzymatic response that changes the pH of the electrolyte (blood serum). This change in pH is transformed by the EISCAP to a shift in the capacitance-voltage (C-V) characteristics of the device which in turn can be mapped to the amount of TG in blood serum. We have developed a miniaturized biochip with immobilized enzyme integrated with a thin film counter electrode for the estimation of TG in blood serum within the clinical range. The miniaturized devices are tested using blood serum sample to estimate the TG concentration and compared with clinical data. © 2013 IEEE.

Proceedings of IEEE Sensors

Compact silicon biosensor for the clinical range estimation of blood serum triglycéride

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)

In this paper we discuss the fabrication and characterization of miniaturized triglyceride biosensors on crystalline silicon and porous silicon (PS) substrates. The sensors are miniaturized Electrolyte Insulator Semiconductor Capacitors (mini-EISCAPs), which primarily sense the pH variation of the electrolyte used. The lipase enzyme, which catalyses the hydrolysis of triglycerides, was immobilized on the sensor surface. Triglyceride solutions introduced into the enzyme immobilized sensor produced butyric acid which causes the change in pH of the electrolyte. Miniaturized EISCAP sensors were fabricated using bulk micromachining technique and have silicon nitride as the pH sensitive dielectric layer. The sensors are cubical pits of dimensions 1,500 μm × 1,500 μm × 100 μm which can hold an electrolyte volume of 0.1 μl. The pH changes in the solution can be sensed through the EISCAP sensors by monitoring the flatband voltage shift in the Capacitance-Voltage (C-V) characteristics taken during the course of the reaction. The reaction rate is found to be quite high in the miniature cells when compared to the sensors of bigger dimensions. © 2008 Springer Science+Business Media, LLC.

Journal of Materials Science: Materials in Medicine

Miniaturization of EISCAP sensor for triglyceride detection

Lipase from Pseudomonas cepacia was covalently immobilized on crystalline silicon, porous silicon and silicon nitride surfaces. The various stages of immobilization were characterized using FTIR (Fourier transform infrared) spectroscopy. The surface topography of the enzyme immobilized surfaces was investigated using scanning electron microscopy (SEM). The quantity of the immobilized active enzyme was estimated by the para-nitrophenyl palmitate (pNPP) assay. The immobilized lipase was used for triglyceride hydrolysis and the acid produced was detected by a pH sensitive silicon nitride surface as a shift in the C-V (capacitance-voltage) characteristics of an electrolyte-insulator-semiconductor capacitor (EISCAP) thus validating the immobilization method for use as a biosensor. © 2008 Elsevier B.V. All rights reserved.

Applied Surface Science

Covalent immobilization of Pseudomonas cepacia lipase on semiconducting materials

Miniaturised silicon biosensors for the detection of triglyceride in blood serum

Journal	Analytical Methods
ISSN	17599660
Open Access	No