Inactivation of bacterial endotoxin in water using a pressurized microfluidic ultra-high temperature (UHT) pasteurizer

Ultra-pure water is critical for certain medical applications such as preparation of dialysis fluid and formulation of intravenous medications. However, production of ultra-pure water is challenging due to the difficulty of inactivating or removing endotoxins in water. The main objective of this study was to evaluate the ability of a pressurized microfluidic ultra-high temperature (UHT) pasteurizer to inactivate endotoxins (>2 log EU/ml) in water to meet the sterility assurance limit. A solution of Pseudomonas endotoxin (300 EU/ml) was prepared in endotoxin-free water and treated at various temperatures (150 °C–230 °C), pressures (1.65–3.10 MPa) and flow rates (100–400 ml/min). Endotoxin concentrations were determined using the Kinetic Turbidimetric LAL Assay. Endotoxin was effectively heat stable when treated at temperatures between 150 °C and 184 °C. Endotoxin inactivation at 200 °C was significant and was influenced by flow rate; however, even the slowest flow rate (100 ml/min) could not confidently achieve >2 log reduction of endotoxin. Increasing the temperature/pressure (230 °C/3.10 MPa) resulted in >3.8 log EU/ml reduction of endotoxin at all flow rates (100–400 ml/min). This is the first demonstration that microfluidic UHT pasteurization could be an effective process for inactivating endotoxin in water used in medical devices and for other continuous flow applications.