Electrical System for Bioelectric Impedance using AD5933 Impedance Converter

Benchtop lab equipment, such as the HP4194A Precision Impedance Analyzer, offer accuracy and functionality but are often expensive and bulky. Although integrated circuits offer less functionality than benchtop equivalents, they can be a cheaper alternative for smaller applications. In this study, the AD5933 Impedance Converter was investigated as a low-cost option for impedance analysis of the bicep brachii. The AD5933 evaluation board was properly calibrated to measure human muscle by using an equivalent parallel circuit consisting of a 5 nF capacitor and a 1 kOhm resistor. Next, the impedance of the bicep was measured using the AD5933 as the experimental device and the HP4194A as the control device. A 2 volt peak-to- peak signal was generated for a 10 kHz to 100 kHz frequency range and the resulting impedance of the bicep was measured. The AD5933 recorded impedance curves qualitatively and quantitatively similar to those recorded by the HP4194A. Thus, the AD5933 was considered to be a low- cost alternative for impedance analysis in small-scale medical applications

Dielectric Characterization of Coastal Cartilage Chondrocytes

BACKGROUND: Chondrocytes respond to biomechanical and bioelectrochemical stimuli by secreting appropriate extracellular matrix proteins that enable the tissue to withstand the large forces it experiences. Although biomechanical aspects of cartilage are well described, little is known of the bioelectrochemical responses. The focus of this study is to identify bioelectrical characteristics of human costal cartilage cells using dielectric spectroscopy. METHODS: Dielectric spectroscopy allows non-invasive probing of biological cells. An in house computer program is developed to extract dielectric properties of human costal cartilage cells from raw cell suspension impedance data measured by a microfluidic device. The dielectric properties of chondrocytes are compared with other cell types in order to comparatively assess the electrical nature of chondrocytes. RESULTS: The results suggest that electrical cell membrane characteristics of chondrocyte cells are close to cardiomyoblast cells, cells known to possess an array of active ion channels. The blocking effect of the non-specific ion channel blocker gadolinium is tested on chondrocytes with a significant reduction in both membrane capacitance and conductance. CONCLUSIONS: We have utilized a microfluidic chamber to mimic biomechanical events through changes in bioelectrochemistry and described the dielectric properties of chondrocytes to be closer to cells derived from electrically excitably tissues. GENERAL SIGNIFICANCE: The study describes dielectric characterization of human costal chondrocyte cells using physical tools, where results and methodology can be used to identify potential anomalies in bioelectrochemical responses that may lead to cartilage disorders

Probing Nanoparticle Interactions in Cell Culture Media

Nanoparticle research is often performed in vitro with little emphasis on the potential role of cell culture medium. In this study, gold nanoparticle interactions with cell culture medium and two cancer cell lines (human T-cell leukemia Jurkat and human pancreatic carcinoma PANC1) were investigated. Gold nanoparticles of 10, 25, 50, and 100 nm in diameter at fixed mass concentration were tested. Size distributions and zeta potentials of gold nanoparticles suspended in deionized (DI) water and Dulbecco\u27s Modified Eagle\u27s Media (DMEM) supplemented with fetal calf serum (FCS) were measured using dynamic light scattering (DLS) technique. In DI water, particle size distributions exhibited peaks around their nominal diameters. However, the gold nanoparticles suspended in DMEM supplemented with FCS formed complexes around 100 nm, regardless of their nominal sizes. The DLS and UV-vis spectroscopy results indicate gold nanoparticle agglomeration in DMEM that is not supplemented by FCS. The zeta potential results indicate that protein rich FCS increases the dispersion quality of gold nanoparticle suspensions through steric effects. Cellular uptake of 25 and 50 nm gold nanoparticles by Jurkat and PANC1 cell lines were investigated using inductively coupled plasma-mass spectroscopy. The intracellular gold level of PANC1 cells was higher than that of Jurkat cells, where 50 nm particles enter cells at faster rates than the 25 nm particles

Microfluidic Impedance Spectroscopy as a Tool for Quantitative Biology and Biotechnology

A microfluidic device that is able to perform dielectric spectroscopy is developed. The device consists of a measurement chamber that is 250 μm thick and 750 μm radius. Around 1000 cells fit inside the chamber assuming average quantities for cell radius and volume fraction. This number is about 1000 folds lower than the capacity of conventional fixtures. A T-cell leukemia cell line Jurkat is tested using the microfluidic device. Measurements of deionized water and salt solutions are utilized to determine parasitic effects and geometric capacitance of the device. Physical models, including Maxwell-Wagner mixture and double shell models, are used to derive quantities for sub-cellular units. Clausius-Mossotti factor of Jurkat cells is extracted from the impedance spectrum. Effects of cellular heterogeneity are discussed and parameterized. Jurkat cells are also tested with a time domain reflectometry system for verification of the microfluidic device. Results indicate good agreement of values obtained with both techniques. The device can be used as a unique cell diagnostic tool to yield information on sub-cellular units. (C) 2012 American Institute of Physics

Electrical System for Bioelectric Impedance using AD5933 Impedance Converter

Benchtop lab equipment, such as the HP4194A Precision Impedance Analyzer, offer accuracy and functionality but are often expensive and bulky. Although integrated circuits offer less functionality than benchtop equivalents, they can be a cheaper alternative for smaller applications. In this study, the AD5933 Impedance Converter was investigated as a low-cost option for impedance analysis of the bicep brachii. The AD5933 evaluation board was properly calibrated to measure human muscle by using an equivalent parallel circuit consisting of a 5 nF capacitor and a 1 kOhm resistor. Next, the impedance of the bicep was measured using the AD5933 as the experimental device and the HP4194A as the control device. A 2 volt peak-to- peak signal was generated for a 10 kHz to 100 kHz frequency range and the resulting impedance of the bicep was measured. The AD5933 recorded impedance curves qualitatively and quantitatively similar to those recorded by the HP4194A. Thus, the AD5933 was considered to be a low- cost alternative for impedance analysis in small-scale medical applications

Effects of beta-carotene on the fertility of rabbits

The aim of this study was to investigate the effects of beta-carotene added in the diets of New Zealand rabbits on the ovulation, fertilization ratio, LH and progesterone levels. Forty female and 4 male adult New Zealand rabbits were used. Female rabbits were divided into 2 groups consisting of 20 each. Group I consisted of experimental rabbits while Group II was kept as the control. Animals in the experimental and control groups were kept in separate cages but in the same husbandry conditions. For the animals in the experimental group, 2.8 mg/kg of synthetic beta-carotene was added into the diet for a month. The female adults in the control group were fed a normal diet. At the end of month, male rabbits were deliberately placed in cages with females for mating. Blood samples were taken from all female rabbits every 6 hours for 2 days after mating and the level of LH was measured in all samples. Blood was also taken at 4 day intervals for 30 days and the progesterone levels were measured. All females (in Groups I and II) were laparotomized 2 weeks after mating and the ovarial corpora lutea and fetuses were counted. The LH levels in Groups I and II were statistically analysed and no difference was found between 0, 12, 18, 24, 30, 36, 42 and 48 hours, but the difference between Groups I and II at 6 hours was statistically significant (p<0.05). The difference in progesterone values on days 0, 4, 8 and 20 between the groups was not statistically significant, but the difference at 12, 16 and 30 days was significant (p<0.05). This difference on days 24 and 28 was also significant (p<0.01). The numbers of corpora lutea taken from the two groups were similar. The number of fetuses in Groups I and II was different and the difference was statistically significant (p<0.05). The number of fetuses born alive was also different and was statistically significant (p<0.05). In conclusion, the results of this study indicated that the addition of beta-carotene in the rabbits' feed stimulated fertilization and increased reproductive performance. Therefore, beta-carotene can be used as a supplement in rabbit feed in order to increase reproduction

Dielectrophoretic Separation of Mouse Melanoma Clones

Dielectrophoresis (DEP) is employed to differentiate clones of mouse melanoma B16F10 cells. Five clones were tested on microelectrodes. At a specific excitation frequency, clone 1 showed a different DEP response than the other four. Growth rate, melanin content, recovery from cryopreservation, and in vitro invasive studies were performed. Clone 1 is shown to have significantly different melanin content and recovery rate from cryopreservation. This paper reports the ability of DEP to differentiate between two malignant cells of the same origin. Different DEP responses of the two clones could be linked to their melanin content

Differential Dielectric Responses of Chondrocyte and Jurkat Cells in Electromanipulation Buffers

Electromanipulation of cells as a label-free cell manipulation and characterization tool has gained particular interest recently. However, the applicability of electromanipulation, particularly dielectrophoresis (DEP), to biological cells is limited to cells suspended in buffers containing lower amounts of salts relative to the physiological buffers. One might question the use of low conductivity buffers (LCBs) for DEP separation, as cells are stressed in buffers lacking physiological levels of salt. In LCB, cells leak ions and undergo volume regulation. Therefore, cells exhibit time-dependent DEP response in LCB. In this work, cellular changes in LCB are assessed by dielectric spectroscopy, cell viability assay, and gene expression of chondrocytes and Jurkats. Results indicate leakage of ions from cells, increases in cytoplasmic conductivity, membrane capacitance, and conductance. Separability factor, which defines optimum conditions for DEP cell separation, for the two cell types is calculated using the cellular dielectric data. Optimum DEP separation conditions change as cellular dielectric properties evolve in LCB. Genetic analyses indicate no changes in expression of ionic channel proteins for chondrocytes suspended in LCB. Retaining cellular viability might be important during dielectrophoretic separation, especially when cells are to be biologically tested at a downstream microfluidic component

Dielectrophoretic separation of mouse melanoma clones

Dielectrophoresis (DEP) is employed to differentiate clones of mouse melanoma B16F10 cells. Five clones were tested on microelectrodes. At a specific excitation frequency, clone 1 showed a different DEP response than the other four. Growth rate, melanin content, recovery from cryopreservation, and in vitro invasive studies were performed. Clone 1 is shown to have significantly different melanin content and recovery rate from cryopreservation. This paper reports the ability of DEP to differentiate between two malignant cells of the same origin. Different DEP responses of the two clones could be linked to their melanin content