1,721,828 research outputs found
Single Cell Impedance Spectroscopy
No full textEThOS - Electronic Theses Online ServiceGBUnited Kingdo
Single cell microfluidic impedance cytometry – a review
No full textLab on chip technologies are being developed for multiplexed single cell assays. Impedance offers a simple non-invasive method for counting, identifying and monitoring cellular function. A number of different microfluidic devices for single cell impedance have been developed. These have potential applications ranging from simple cell counting and label-free identification of different cell types or detecting changes in cell morphology after invasion by parasites. Devices have also been developed that trap single cells and continuously record impedance data. This technology has applications in basic research, diagnostics or non-invasively probing cell function at the single-cell level. This review will describe the underlying principles of impedance analysis of particles. It then describes the state of the art in the field of microfluidic impedance flow cytometry. Finally future directions and challenges are discussed
Microfluidic impedance cytometry-measuring single cells at high speed
No full textHigh throughput single cell microfluidic analysis platforms offer the ability to characterize large numbers of individual cells (or more generally particles) at high speed. Miniature flow cytometers offer new methods for the rapid analysis of single cells. Impedance analysis of single cells provides information on cell size (volume), membrane and cytoplasmic characteristics. The technology has developed rapidly and offers the prospects of new approaches for counting and differentiating cells with applications from basic research to point of care diagnostics
AC electrokinetic particle manipulation in microsystems
No full textLab-on-Chip systems integrate multiple functionalities on a single platform. Automated or remote manipulation and analysis of particles and fluids is a key element in microfluidic devices. Microelectrodes can be integrated into these devices to generate large electric fields and field gradients using low voltages. Electrokinetics is an attractive method for integrating particle manipulation and separation within such systems. The electrokinetic forces are easy to control by designing optimum electrode structures and choice of field and frequency. In this chapter, the theory of AC electrokinetics is reviewed and example applications for manipulation of particles are provided. The use of dielectrophoresis (DEP) for manipulating micro particles is then described, together with a discussion on scaling issues
Single cell impedance spectroscopy
No full textCellular analysis requires a combination of biophysical and biochemical approaches for counting, manipulation and characterization of biological cells. In recent years, considerable attentions have been paid to single cell analysis based on Lab-On-a-Chip (LOC) technology, which offers the characterization of a large amount of cells one by one [1-3]. Electrical impedance spectroscopy (EIS) provides a high speed, non-invasive and label-free technique for single cell analysis. We have fabricated microfluidic chips with integrated microelectrodes inside the microchannel to perform a differential impedance measurement, as shown in figure 1. Two pairs of parallel facing electrodes define a detection and reference volume. AC excitation voltages at mixed frequencies are applied to the microelectrodes, generating electric field in the channel. As a cell passes by, it modifies the current lines through each of the two detection volumes in turn. A positive and negative peak variation in the measured differential current signal can be observed. Due to differences in the dielectric properties and sizes of various cells, specific information can be obtained from a single cell membrane, cytoplasm or nucleus at distinct frequencies
Impedance Measurements of Cells
No full textImpedance measurements are performed by applying an AC excitation voltage to an unknown system whilst measuring the current. The ratio of the excitation voltage to the current gives the complex impedance of the system. Impedance measurements of cells provide data on the intrinsic dielectric properties of the cells
Current Analysis Model for the Single Particle Impedance Spectrum Sensitivity Analysis of Microfluidic Cytometers
No full textAdaptive noise cancellation for single cell impedance spectroscopy using Maximum Length Sequences
No full textWe have recently developed a novel impedance spectroscopy for high throughput analysis on single biological particles in microfluidic cytometers using Maximum Length Sequences (MLS) 1-3. This technique uses MLS as the excitation signal to the micro-impedance system (figure 1) and allows multi-frequency impedance data to be obtained in one measurement, due to the white noise-like properties of MLS. The data flow diagram of MLS measurement system is shown in figure 2. The digital MLS signal, generated in MATLABTM (Mathworks, Inc., USA) is converted into the analog MLS by D/A converter and applied to the cytometer. After low pass filtering (LPF), the response of the system is sampled into digital form. A Fast M-sequence Transform (FMT) converts the sampled response into the Impulse Response (IR), which is equivalent to the transfer-function of the system. Finally Fast Fourier Transform (FFT) is applied to the IR, characterizing the transfer-function in the frequency domain, from which the impedance of the cell is extracted. The impedance spectra of polystyrene beads and human red blood cells have been measured using this new technology. We have derived 512 frequency data evenly distributed between 976.56 Hz and 500 kHz within approximately 1 ms and the data have been verified by the conventional AC single frequency measurement and the circuit simulations in PSpice (Cadence Inc. USA)2, 3. However, the original measured data using MLS technology exhibits inferior signal-to-noise ratio (SNR), compared to the AC single frequency measurement, in which the energy of the excitation signal is purely concentrated on one specific frequency and the lock-in amplifier for demodulation has a strong ability to reject the noise at other frequencies. In order to improve the SNR of the MLS measurement system without adding any hardware, we use adaptive filters to perform the noise cancellation4, which is based on the least mean square (LMS) principle. A fixed delay is inserted in the original data as a reference input to the adaptive filter for cancelling the noise interference from the background, as shown in figure 3. The SNR of the system can be improved approximately 20 dB at each measured frequency by attenuating the noise level
- …
