CRYOPROTECTIVE AGENT (CPA) REMOVAL WITH DILUTION-FILTRATION METHOD AND CPA CONCENTRATION MONITORING WITH ELECTRICAL CONDUCTIVITY MEASUREMENTS

In cell/tissue cryopreservation, cryoprotective agents (CPAs) should be added before freezing and removed after thawing. Nowadays people mainly apply centrifugation for CPA removal, which may cause many problems. Meanwhile, a simple and cheap method for real-time monitoring of the residual CPA concentration during processing remains an unfilled need. In this work, a "dilution-filtration" system with hollow fiber dialyzer was implemented and approved to remove dimethyl sulfoxide (Me2SO) effectively. Compared to other methods (centrifugation and microfluidic approach), this one holds advantages of low time and labor consumption, low osmotic injury to the cells, high effectiveness, ease to control the final suspension volume and low risk of contamination. The "dilution-filtration" system can also be easily modified for CPA addition and cell suspension volume control (concentration or dilution of cell suspension). Meanwhile, a method of electrical conductivity (EC) measurement was applied to monitor the residual CPA concentration. The results showed EC measurements of waste solution can convey the CPA concentrations in cell suspension. This validates the feasibility of a safer and easier way to on-line and real-time monitoring of CPA concentration in cell suspension by measuring the EC of waste solution.