Research Progress on Microfluidic Chip of Cell Separation Based on Dielectrophoresis / 分析化学

Cell separation technology is an important means for cell sorting and cell-population purification. It is the current international research hot spot in biochemical analysis which has very important applications in many fields such as biology, medicine, agriculture and environment. This review introduces the development status of cell separation using microfluidic chip based on dielectrophoresis. It expounds the working principle of dielectrophoresis and the key factors such as cell size, electrode shape and signals that impacts the dielectrophoresis of cell separation on different types of microfluidic chip. Finally, it forecasts the future development trend of cell separation using microfluidic chip based on dielectrophoresis.

Dielectric response of erythrocyte in patients with Kaschin-Beck disease / 中华地方病学杂志

Objective To measure the erythrocyte dielectric response variation of patients with KaschinBeck disease,to explore the pathogenesis of Kaschin-Beck disease and seek more effective means for evaluating the effectiveness of early diagnosis and control measures against Kaschin-Beck disease.Methods According to the principle of dielectrophoresis and cell dielectric response phenomena,dielectrophoretic pool was manufactured and dielectrophoretic detection and separation system was established.Patients with Kaschin-Beck disease (438) were selected in Kaschin-Beck disease areas of Aba County,Sichuan.At the same time,healthy persons (480) in KaschinBeck disease areas and non-Kaschin-Beck disease areas in Aba County were selected.Anticoagulant blood samples from patients with Kaschin-Beck disease and healthy persons were collected,erythrocytes were separated,cell suspension (10s cells/ml) was prepared and 200 μl cell suspension was added to the dielectrophoretic pool to measure erythrocyte dielectric response rate.Results Erythrocyte dielectric response rates were significantly different between patients living in Kaschin-Beck disease areas with Kaschin-Beck disease [(75.87 ± 5.89)％] and healthy persons living in Kaschin-Beck disease areas and non-Kaschin-Beck disease areas [(92.43 ± 4.45)％,(92.81 ±5.01)％,F =1.843,P ＜ 0.01).Erythrocyte dielectric response rate was significantly reduced in patients with Kaschin-Beck disease compared with that of healthy persons (all P ＜ 0.01);erythrocyte dielectric response rate of adult patients with Kaschin-Beck disease was lower [(69.57 ± 6.87)％] than that of pediatric patients with Kaschin-Beck disease [(82.17 ± 4.91)％,P ＜ 0.01].Erythrocyte dielectric response rates were significantly different in patients with different degrees of Kaschin-Beck disease (F =1.647,P ＜ 0.01).Erythrocyte dielectric response rate of patients with Kaschin-Beck disease was negatively correlated with prevalence of the disease (r =-0.87,P ＜ 0.01).Conclusions Erythrocytes of patients with Kaschin-Beck disease have some degree of pathological damage.The more severe the disease,the more serious the damage of red blood cell.The change of erythrocyte dielectric response properties may be used as an index to judge the prevalence of Kaschin-Beck disease and for early diagnosis.

Preparation and Experimental Study on Dielectrophoresis- Based Microfluidic Chip for Cell Patterning / 分析化学

Adielectrophoresis-basedmicrofluidicchipappliedtocellspatterningisdesignedandfabricated, and it demonstrates non-contact and batch manipulation of cells. The microfluidic chip employs a PDMS microchannel and two ITO electrodes, which are designed as astep shape. The distribution of electric field caused by the microelectrodes is simulated by finite element simulation software, COMSOL. The position of the maximum intensity of electric field is also determined. The ITO microelectrodes and the PDMS microchannel are fabricated using MEMS fabrication process. After oxygen plasma surface treatment, the PDMS microchannel and glass substrate with the ITO microelectrodes are aligned and bonded to form experimental microfluidic chip. Through DEP experiment with the varying frequencies, DEP response of yeast cells is examined, and the electric field frequency of the both positive and negative DEP responses are confirmed. The results showed that yeast cells in solution conductivity of 60 μS/cm had negative DEP movement at the frequency of 1 kHz to 10 kHz, positive DEP movement at the 500 kHz to 10 MHz, and no DEP movement at the 50 kHz. Under the condition of the sinusoidal potential of 8Vp-p and the electric field frequency of 5 MHz, the yeast cells were aligned into chains along the step edge of microelectrodes.

Bacterial handling under the influence of non-uniform electric fields: dielectrophoretic and electrohydrodynamic effects

This paper describes the modeling and experimental verification of a castellated microelectrode array intended tohandle biocells, based on common dielectrophoresis. The proposed microsystem was developed employing platinumelectrodes deposited by lift-off, silicon micromachining, and photoresin patterning techniques. Having fabricated the microdevice it was tested employing Escherichia coli as bioparticle model. Positive dielectrophoresis could be verified with the selected cells for frequencies above 100 kHz, and electrohydrodynamic effects were observed as the dominant phenomena when working at lower frequencies. As a result, negative dielectrophoresis could not be observed because its occurrence overlaps with electrohydrodynamic effects; i.e. the viscous drag force acting on the particles is greater than the dielectrophoretic force at frequencies where negative dielectrophoresis should occur. The experiments illustrate the convenience of this kind of microdevices to micro handling biological objects, opening the possibility for using these microarrays with other bioparticles. Additionally, liquid motion as a result of electrohydrodynamic effects must be taken into account when designing bioparticle micromanipulators, and could be used as mechanism to clean the electrode surfaces, that is one of the most important problems related to this kind of devices.

Este artigo descreve a modelagem e teste experimental de uma rede de microeletrodos em cremalheira cujo objetivo é o manuseio de células biológicas, com base em dieletroforese comum. O microsistema proposto foi desenvolvido empregando eletrodos de platina depositados por técnicas de 'lift-off', micro-usinagem em silício e litografia com foto-resina. Uma vez fabricado o microdispositivo, este foi testado utilizando a Escherichia coli como modelo de biopartículas. Dieletroforese positiva pode ser observada com as células selecionadas para freqüências acima de 100kHz, e efeitos eletro-hidrodinâmicos foram observados como o fenômeno dominante para menores freqüências. Como resultado, a dieletroforese negativa não pode ser observada pois sua ocorrência se sobrepõe a efeitos eletro-hidrodinâmicos; i.e. a força de arraste viscoso atuando sobre as partículas é superior à força dieletroforética para freqüências em que a dieletroforese negativa deveria ocorrer. Os experimentos ilustram a conveniência deste tipo de micro-dispositivo para o micromanuseio de objetos biológicos, abrindo a possibilidade de uso destas micro-redes com outras partículas biológicas. Além disto, o movimento líquido como resultado dos efeitos eletro-hidrodinâmicos deve ser levado em conta ao se desenhar micromanipuladores de partículas biológicas, e pode ser utilizado como mecanismo para limpar as superfícies dos eletrodos, que é um dos problemas mais importantes relacionados a este tipo de dispositivo.