Comparison of Cooling Systems during Islet Purification

Abstract

Islet isolation is a complex procedure that includes digestion and purification of pancreatic tissue. As we move towards clinical regulatory control and standardization, understanding of the detailed stages of the procedure have become increasingly important. Purification on a COBE 2991 density gradient allows human islets to be separated from a large volume of acinar tissue. Cooling the gradient and tissue is thought to be important to reduce metabolic activity but cooling systems for the gradient are expensive, with limited availability. In this study, the efficiency of cooling methods for the COBE 2991 cell separator has been investigated. The two cooling systems were: a) COBE 2991 modified internally to allow coolant (polyethylene glycol) from a chiller to circulate either side of the spindle and around the bowl (original system), and b) an air-cooled system using an air conditioner to blow cold air into the bowl from above (air cooler system). Cooling required 20 min for the original system and temperature was stabilized within 4–7°C. The air system cooled rapidly but was not stable. There was an increase in the temperature of the medium with using both systems during centrifugation because of heat generated by the COBE machine; however, the temperature of the medium after centrifugation with the air system was significantly higher than that with the original system (13.3 ± 0.2°C vs. 8.7 ± 0.7°C, p < 0.05). The original cooler system was found to be more efficient at reducing heat generated by the COBE machine than the air system. Further investigation of the importance of the recorded temperatures is required.