Microfluidic Cell Electroporation

Movahed S, Li D (2011) Microfluidics cell electroporation. Microfluid Nanofluid 10(4) 703-734... 

Applying an electric field near a cell will result in a disturbance in the membrane structure and creating nanopores in the cell membrane. This leads to a significant increase in electrical conductivity and permeability of the cell membrane that is usually named the electroporation or electropermeabilization. Performing the cell electroporation in microfluidic devices is usually called microfluidic cell electroporation. ... 

Microfluidic Cell Electroporation, Table 1 Values of the parameters of cell manbrane permeabilization theory... 

Compared with the traditional electroporative devices, a very low-intensity electric pulse is usually required to perform microfluidic cell electroporation. This is due to the extremely small space of the electrodes in microfluidic electroporative devices. It significantly reduces the size of the required pulse generator, the amoxmt of generated heat, and safety cautions... 

Microfluidic Cell Electroporation, Fig. 6 Electro-fiision process of two different kinds of cells. The upper and lower cells are animal HEK-293 and plant cucumber mesophyll protoplasts, respectively. In this figure, A, B,... 

In this article, the underlying concepts and theory of electroporation and also some of the most significant experimental studies on the microfluidic ceU electroporation will be reviewed. It wDl begin by providing the fundamentals and mathematical description of the cell electroporation. Here, the theory of membrane permeabilization and its simplified asymptotic solution will be reviewed. After that, the most... 

Rubinsky s group presented the first microfluidic device to electroporate a cell (Davalos et al., 2000 Huang and Rubinsky, 1999). Their devices consisted of three silicon chips bonded together to form two chambers, separated by a 1 pm thick silicon nitride membrane with a 2—10 pm diameter hole. Because silicon nitride is nonconductive, any electrical current flowing from the top chamber to the bottom chamber must pass through this microhole. A cell suspension was introduced into the top chamber, followed by the immobilization of one cell in the hole by lowering the pressure in the bottom chamber. 

A series of innovative strategies have been developed to electroporate cells on a microfluidic platform. In these methods, high-density microelectrodes or structures with subcellular dimensions are required. Lu et al. presented... 

Although the theoretical studies on this subject lag the experimental ones, some theoretical studies have been accomplished recently to discover the nature of the membrane permeabilization and cell transfection. It helps the experimentalist to optimize the design and performance of their proposed microfluidic design for electroporation. 

One of the main applications of microfluidic electroporation devices is cell lysis. In these devices, the mechanical (shear force) or electrical forces are applied to rapture the cell membrane and release its intercellular contents. 

Many studies have been conducted on this topic. As an example. Fig. 3 depicts the schematic diagram of the microfluidic electroporative device proposed by Wang et al. [12]. In their setup, cells start to move from sample reservoir (right-hand side) to the receiving reservoir (left-hand side). The electrodes are placed at the ends of the microchannels. In the electroporation area, geometric change and reduction of the cross-sectional area of the microchannels intensifies the applied electric field to the required electric field of electroporation. 

The most important function of electroporation is transfection, i.e., inserting the biological nanosamples into the living cell. Cell viability and transfection rate are the two most important indicators to evaluate the functionality of these microfluidic electroporatiOTi devices. The applied electric pulse must be ctuitroUed carefully. While the nanosample insertitHi should be as successful as possible, the viability of the cell may not be affected by applied external electric pulse. Compared with the cell lysis, the cell transfection usually performs by q)plying lower external electric field. 

Fox MB, Esveld DC, Valero A, Luttge R, Mastwijk HC, Bartels PV, Berg AVD, Boom RM (2006) Electroporation of cells in microfluidic devices a review. Anal Bioanal Chem 385(3) 474-485... 

Wang H-Y, Lu C (2006) Electroporation of mammalian cells in a microfluidic channel with geometric variation. Anal Chem 78 5158-5164... 

Lu H, Schmidt MA, Jensen KF (2005) A microfluidic electroporation device for cell lysis. Lab Chip... 

When a large electric field is applied across a cell, the transmembrane potential is dismpted and pores are formed on the surface of the membrane. This phenomenon is called electroporation and is often used for gene transfection. As conventionally implemented, the process is reversible, and when the electric field is terminated, the pores close. The phenomenon can also be used to cause permanent disruption of the membrane, effectively lysing the cell. There have been several reports on the use of electrical lysis techniques in microfluidic devices [9-11]. Of particular interest, fast lysis of individual cells ( 33 ms) by electrical pulses for chemical cytometry was demonstrated in a microfluidic platform [12]. These extremely rapid lysis methods which minimize unwanted effects of slow lysis (that may bias the results) make these techniques favorable for protein analysis when compared to chemical lysis techniques. One drawback of electrical lysis is that much of the cell membrane, subcellular structures and the nucleus may remain intact and thus can clog the channe or adhere to the surface, affecting the separation and limiting the capacity for re-use. 

Bao, N., Zhan, Y., Lu, C., 2008. Microfluidic electroporative flow cytometry for studying single-cell biomechanics. Anal. Chem. 80 (20), 7714-7719. Available at http //www.ncbi. nlm.nih.gov/pubmed/18798650. 

---