Rangadhar Pradhan

Impedimetric characterization of human blood using three-electrode based ECIS devices

Abstract In this study, three-electrode based electric cell-substrate impedance sensing (ECIS) devices were used to study the electrical properties of blood and its constituents using electrochemical impedance spectroscopy. The three-electrode based ECIS devices were fabricated by using micromachining technology with varying sizes for working, reference and counter electrodes. The blood and its constituents such as serum, plasma, and red blood cells (RBCs) were prepared by conventional methods and stored for impedance measurement using fabricated microdevices. Equivalent circuits for blood, serum, plasma and RBCs were proposed using the software package ZSimpWin to validate the experimental data. The proposed equivalent circuit models of blood and its components have excellent agreement up to a frequency of 1 MHz. It is evident from the experimental results that blood and its components have specific impedance signatures that decrease with the increase of frequency. Blood shows higher impedance than the other samples in the lower frequency range (<50 kHz). It was also found that above 50 kHz, the impedance value of RBCs is nearly the same as whole blood. The impedance of serum and plasma steadily decreases with the increase of frequency up to 100 kHz and flattens out after that. The minimum impedance value achieved for serum and plasma is much less than the value obtained for whole blood.

Frequency dependent impedimetric cytotoxic evaluation of anticancer drug on breast cancer cell

The present work reports the impedance characteristics of MCF-7 cell lines treated with anticancer drug ZD6474 to evaluate the cytotoxic effect on cellular electrical behaviour using miniature impedance sensors. Four types of impedance sensing devices with different electrode geometries are fabricated by microfabrication technology. The frequency response characteristics of drug treated cells are studied to evaluate cytotoxic effect of ZD6474 and also to assess the frequency dependent sensitivity variation with electrode area. A significant variation in magnitude of measured impedance data is obtained for drug treated samples above 10 µM dose indicating prominent effect of ZD6474 which results in suppression of cell proliferation and induction of apoptosis process. The results obtained by impedimetric method are correlated well with conventional in vitro assays such as flow cytometry, cell viability assays and microscopic imaging. Finally an empirical relation between cell impedance, electrode area and drug dose is established from impedance data which exhibits a negative correlation between drug doses and impedance of cancer cells.

Some salient points in type 2 diabetes prevalence in rural Bengal.

Abstract Diabetes mellitus is a complex metabolic disorder characterized by failure to properly utilize glucose and other metabolites in the body causing spillover of these substances in the urine, mainly due to relative or absolute deficiencies of insulin secretions by the β- cells of the pancreas. Our observations indicates that prevalence of diabetes in rural Bengal is in between 3.5% - 5.7%. Religion wise prevalence in rural Bengal shows Muslims have lowest prevalence (4.8%) and it is highest in Hindus (5.4%) while Christians (5.1%) in between. Analysis of Food intake patterns show the prevalence of diabetes is more in meat eaters (7.2%). It is most in pork eaters (7.6%), intermediate in chicken eaters (6.4%) and lowest in those who take goat/sheep (6.1%). In vegetarians it is 5.8% and in fish eaters it is 5.2%. Other factors, such as migration from one place to another, food intake habit, exercises have a great role in type 2 diabetes management.

Electric cell–substrate impedance sensing technique to monitor cellular behaviours of cancer cells

The present work reports the cellular electrical behaviour of the MDA-MB-231 breast cancer cell line treated with the anticancer drug ZD6474, using impedance sensing devices. Microelectrode-based devices with four different electrode geometries are fabricated by microfabrication technology. Real-time impedance monitoring data show high impedance variation during the initial 5 hours, revealing rapid spreading of cells over electrode surfaces. It is further established that impedance variation is mostly controlled by cells covering the electrode surface area, and thus, an enhanced effect is seen with electrode devices with a smaller geometry. Real-time impedimetric cytotoxicity data reveal that cell death and detachment starts at 21 h after inoculation of cells in the devices. The frequency response characteristics of drug-treated cells are studied to evaluate the cytotoxic effect of ZD6474. Compared to the control, a significant variation in the magnitude of the measured impedance data is observed for drug-treated samples above a 5 μM dose, indicating cell growth suppression and cell death. Finally, an empirical relationship between cell impedance and drug dose is established from impedance data, which shows that they are negatively correlated.

Assessing Cytotoxic Effect of ZD6474 on MDA-MB-468 Cells Using Cell-Based Sensor

This paper presents the application of an impedance-based measurement of cytotoxicity of ZD6474 on MDA-MB-468 breast cancer cells in culture. In the present experiment, four types of cell-based sensors with different electrode geometries are fabricated by using microfabrication technology. MDA-MB-468 cells are grown on the electrode surfaces to study cell adhesion, spreading, and apoptosis. The real time impedance monitoring data show that the cells took to complete the spreading process on electrode surfaces. The cytotoxic effect of ZD6474 is dose dependant and with the increases of drug doses, the impedance value decreases, which correlates that ZD6474 blocks cell proliferation and induces apoptosis in breast cancer cells. A quantitative relationship, developed between the impedance and drug doses, establishes a negative correlation between the drug doses and impedance. General consistency has been found between the impedance response and the biochemical assay. Thus, impedance sensing method provides a simple and cost effective method to study chemical cytotoxicity in vitro.

Quantitative evaluation of blood glucose concentration using impedance sensing devices

Abstract This paper reports on the impedimetric investigation of glucose concentrations present in the human blood by using impedance sensing devices with different working electrode areas. It is evident from the experiment that, the impedance value increases with the increase of glucose concentration in blood and the trend follows in all the devices with various electrode areas. The measured complex admittance plot shows two semicircles which are due to double layer and coating capacitances respectively. Lower values of relative standard deviation in impedance data infer the reproducibility of these devices. A quantitative relationship, developed between the impedance and glucose concentration establishes a positive correlation between the blood glucose values and impedance.

Simulation of three electrode device for bioimpedance study using COMSOL Multiphysics

This paper presents the standardization of three electrode device for bioimpedance study. The COMSOL Multiphysics is used as the simulation tool for the characterization of the microdevice. In the last decades, the bioimpedance methodology has been extensively used to study the different aspects of biomedical practices. The Micro Electro Mechanical system (MEMS) helps to fabricate miniature devices for the bioimpedance study. In this work a MEMS based three electrode device is simulated using COMSOL Multiphysics to find out the impedance of Phosphate Buffered Solution (PBS) which is the physiological medium for most biological studies and used to stabilize the microelectrodes under testing. The impedance obtained from COMSOL environment is processed with an equivalent circuits simulator named as ZsimpWin by taking into account the equivalent circuit of the PBS.

Extended Stern Model

In this paper, a theoretical approach of extended Stern model is formulated to represent the electric double layer (EDL) for biochemical as well as biological samples. The existing Stern model is used for several decades to describe the phenomena of electric double layer of electrode/electrolyte interface. In the conventional stern model the double layer which is formed between the electrode and electrolyte interface is described by double layer capacitance. Using the existing Stern model, the equivalent circuit model is not valid for electrical double layer capacitance of electrode/electrolyte interface in I² dispersion range. The protein molecules form chemical coupling and chemical adsorption along with classical ionic bonding with gold electrodes. Thus, the compactness of EDL decreases and the double layer capacitance is replaced by a constant phase element (CPE). In the present paper, a three-electrode based ECIS device was used to measure the impedance of various enzymatic solutions for practical realization of theoretical approach. The results obtained from experimental work, were simulated by equivalent circuit simulator, ZsimpWin to validate the extended Stern model by comparing I‡ 2 value. Finally the electrical parameters were extracted and compared for Stern model and extended Stern model. The results obtained by practical experiment and equivalent circuit simulation showed the effectiveness of extended Stern model over Stern model.

Characterization of electrode/electrolyte interface for bioimpedance study

The electrochemical impedance spectroscopy (EIS) methodology has been extensively used to study the different aspects of electrochemical and biomedical practices. This paper presents the numerical simulation of impedance for electrode/electrolyte interface. The COMSOLR Multiphysics is used to study the interface impedance. The technology for Micro Electro Mechanical system (MEMS) helps to fabricate miniature devices for the electrochemical study. In this work a MEMS based three electrode device along with Phosphate Buffered Solution (PBS) is simulated using COMSOL Multiphysics to find out the impedance of interface. PBS is used as physiological medium for most biological studies and also used to stabilize the microelectrodes under testing. The impedance obtained from COMSOL Multiphysics is processed with an equivalent circuit simulator named as ZsimpWin to find the viability of impedance of electrode/electrolyte interface.

Importance of heart-healthy diet.

Abstract Prevalence of cardiac diseases is on the rise and is at alarming rate in the Indian subcontinent. Diet, lifestyle factors and stress are the cardinal factors in the aetio-pathogenesis of coronary diseases. Other important risk factors are history of smoking, high BP, increased cholesterol level, diabetes and atherosclerosis, abdominal obesity, high triglycerides, insulin resistance, increased homocysteine level in blood and increase in fibrinogen with defects in fibrinolysis. Inter-population differences exist in both the diet and in the socio-cultural factors within and outside the Indian subcontinent. The dietary pattern, eating and method of cooking vary in different parts of India. Currently, there is much controversy over the best balance in carbohydrates, fats, and protein. Although dietary approaches differ in important aspects, they have some recommendations in common: everyone puts much stress in the value of fiber-rich whole grains, legumes, and fresh fruits and vegetables, and when fats are recommended, they are mainly monounsaturated and polyunsaturated. Weight control and exercise are essential components of any diet program. Reduction of all kinds of stress through stress reduction programmes is beneficial. A combined approach will play a rich dividend in control of cardiac diseases.