Flow Electroporation Device

The flow electroporation involves sophisticated process control including I/O control for pinch valves, RS-232 control for pump, temperature & electrical data monitoring, and data base management. My responsibility is to fabricate a computer-controled platform. The task involves with interface cards selection & test, signal conditioner selection, and software-programing for integrating those control components.

The device and control interface are shown as below.

RF pulses trains are the source generating pores over red blood cells (RBC) in a flow cell. Forming pores on RBCs can be achieved by any kind of electrical pulse with sufficient voltage magnitude. However, to find an effective pulse form with minimized cell damage is a challenge.

My tasks were data acquisition instrumentation and data analysis.

The RF pulse picture shown is the plot of acquired data via a high performance DAQ board (1.25Mhz sampling rate.

The obtained voltage and current infomation is analyzed to determine the pores forming condition and Joule effect upon the target fluid. After year's research, the optimal combination was found to obtain the best performance.

The configuration of the flow chamber and flow rate play another impotant role upon the electroporation performance and cell viability. According to the observation from Goldsmith[1], RBCs were performing free tumbling motion in the low-shear force region. Here are the computational analysis about flow pattern.

The rectangular marks indicated the region of free tumbling zone. The red-color part represents high-shear zone in the flow chamber. According to the computational results, low flow rate contributes larger free-tumbling area. The importance of RBC's free tumbling motion is the followings.

Pores formed by electroporation will not be concentrated at certain area, which causing serious damage upon RBC. Moreover, due RBC's tumbling motion, pores will be uniformly distributed over RBC. It contributes successful electroporation performance with significantly low damage upon RBC.

Life is never easy because too much factors get involved, so does this technology. If the operating temperature of the flow cell can not be maintained at certain level, RBC will be subjected damage upon its enzyme. Thus, adequate temperature control is required and a thermal cooler is attached to flow cell.

There came a question, how to determine the adequate size of thermal cooler without spending enormous cost on prototyping and testing? The answer is - using computational analysis. Thermal performance analysis had been conducted by finite element method (FEM). Flow cells at different sizes and different kinds of thermal electric coolers (TEC) were studied. Through the assistance of thermal analysis, the best combination was determined. It is noteworthy that the prediction by thermal analysis is slightly different with real one, which was built according to the analysis.

The previous works had contributed repeatable and remarkable electroporation performance. Is there any way to enhance the performance? Yes, there are two directions, increasing voltage magnitude or number of applied pulse trains. However, carrying out those experiments to find an optimal operating parameters are expensive and time consuming. Therefore, a computational analysis about electric field distribution on the RBCs with different orientation are conducted.

The red spots on the RBC represent the highest cross-membrane electric potential. If the highest cross-membrane electric potential execeed a threshhold value, then the pore will be formed. The results indicate cell orientation has small effect upon the highest cross-membrane electric potential value.

Based on the studies, there is no need to apply higher voltage magnitude. It is enough to apply the magnitude 20% greater than threshold voltage. The strategy to enhance the performance is applying voltage with the magnitude 20% greater than the threshold and increased number of pulse trains. This approach had led the success of an outstanding electroporation performance, and of course, excellent cell viability.

This technology was transfer to Maxcyte, and after year's improvement, the product is shown as teh following. This technology is applied for CAR-T in Glead.

[1]. H.L Goldsmith, Red cell motions and wall interactions in tube flow, Federation Proceeding, Vol.30, No.5,1971