Development and Testing of the Microwave Sterilizable Access Port Prototype

The ability to aseptically remove samples and products, and the capability for addition of materials to sterile or otherwise microbially susceptible systems have always been compromised by the lack of a reliable means of sterilizing the mating fixtures. Cultures of mammalian cells are particularly vulnerable to microbial contamination due to the complexity of nutrient media and the lengthy periods required for cell growth. The Microwave Sterilizable Access Port has been developed to overcome this limitation. The system consists of three primary components: a microwave power source, a combined sterilization chamber/in-line valve port assembly, and a specimen transfer interface. Microwave energy is transmitted via coaxial cable to a small pressurized chamber that serves as a sterile transition between the surrounding environment and the system during transfer of materials. Mating surfaces are sterilized using a small quantity of liquid water (≈500μL) that is transformed to superheated steam by contact with a silicon carbide block located within the sterilization chamber which efficiently absorbs microwave energy at 2.45GHz. The small quantities of water introduced into the sterilization chamber rapidly flash to steam and superheat as additional microwave energy is absorbed. Due to the exponential relationship between temperature and time required to achieve wet thermal sterilization, a complete microbial kill of thermophillic spore forming bacilli is achieved at temperatures between 150-200°C at exposure times as low as 30 seconds. Numerous repetitive bi-directional aseptic transfers of sterile media have been demonstrated in the presence of initial contamination levels in excess of 10⁶CFU. The resulting technology is fully compatible with deployment in microgravity and hypogravity environments.