Microfluidic impedance cytometer for platelet analysis

Numerical and experimental characterization of solid-state micropore-based cytometer for detection and enumeration of biological cells

Portable diagnostic devices have emerged as important tools in various biomedical applications since they can provide an effective solution for low-cost and rapid clinical diagnosis. In this paper, we present a micropore-based resistive cytometer for the detection and enumeration of biological cells. The proposed device was fabricated on a silicon wafer by a standard microelectromechanical system processing technology, which enables a mass production of the proposed chip. The working principle of this cytometer is based upon a bias potential modulated pulse, originating from the biological particle's physical blockage of the micropore. Polystyrene particles of different sizes (7, 10, and 16 μm) were used to test and calibrate the proposed device. A finite element simulation was developed to predict the bias potential modulated pulse (peak amplitude vs. pulse bandwidth), which can provide critical insight into the design of this microfluidic flow cytometer. Furthermore, HeLa cells (a type of tumor cell lines) spiked in a suspension of blood cells, including red blood cells and white blood cells, were used to assess the performance for detecting and counting tumor cells. The proposed microfluidic flow cytometer is able to provide a promising platform to address the current unmet need for point-of-care clinical diagnosis.

Two-dimensional acoustic particle focusing enables sheathless chip Coulter counter with planar electrode configuration

The field of cytometry has grown in scope and importance ever since the early 20th century with leaps in technology introducing the Coulter counter and the flow cytometer. Cytometry methods have brought about a revolution for the medical and biotechnology industry by providing fast and accurate analysis of cell and particle suspensions. Recent developments in the field aim at improving current cytometers and to provide miniaturized low-cost cytometry systems for point-of-care clinical diagnostics or research. In an attempt to address the need for particle positioning which is important for both impedance and optically based cytometers we present a microfluidic system which precisely positions cells and particles, using acoustic forces and subsequently performs measurements using an integrated and simple planar electrode Coulter-type impedance cytometer without the need for sheath flows. Data is presented to show how the acoustic method improves the accuracy of the impedance cytometer when prefocusing is employed to particles and cells (diluted whole blood). Confocal imaging and simulations support the findings and provide the basis for further improvements. The acoustophoretic prefocusing technique opens a path towards small, low cost cytometers while also providing an easy way to improve current systems.

Microfluidic Impedance Cytometry for Blood Cell Analysis

Microfluidic Impedance Cytometry (MIC) is a label-free technique for counting and analyzing single cells at high throughput. Over the last decade the technology has matured into a robust and versatile tool with applications in many areas. Multi-frequency impedance measurements provide information on cell dielectric properties, including cell volume, membrane capacitance, and internal (cytoplasmic) electrical properties. This chapter describes the basic principles underlying MIC together with the technology that enables such measurements. Examples of application in healthcare and diagnostics are provided, including the use of MIC for performing a fast and simple full blood count with a very small volume of sample. The limits of sensitivity of the system are discussed along with novel approaches to enable measurement of small particles such as bacteria. MIC has been used to probe the properties of parasite infected cells, to distinguish tumor cells from normal cells, and even in the differentiation state of stem cells. Addressing future technology challenges, particularly in integrated sample processing, should enable MIC to be used as part of a simple diagnostic toolkit providing sample in, answer out solutions.

Study of Paclitaxel-Treated HeLa Cells by Differential Electrical Impedance Flow Cytometry

This work describes the electrical investigation of paclitaxel-treated HeLa cells using a custom-made microfluidic biosensor for whole cell analysis in continuous flow. We apply the method of differential electrical impedance spectroscopy to treated HeLa cells in order to elucidate the changes in electrical properties compared with non-treated cells. We found that our microfluidic system was able to distinguish between treated and non-treated cells. Furthermore, we utilize a model for electrical impedance spectroscopy in order to perform a theoretical study to clarify our results. This study focuses on investigating the changes in the electrical properties of the cell membrane caused by the effect of paclitaxel. We observe good agreement between the model and the obtained results. This establishes the proof-of-concept for the application in cell drug therapy.