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BIOSENSORS · 411 8.12.3. OPEN MICROFLOW Open microflow is a fluid injection system for tissue where a flowing liquid interface is formed between the sensor surface and the tissue sample matrix. This provides a continuously regenerating fluid filter and barrier that reduces cell or protein access to the sensor surface, thus reducing surface fouling (Rigby, Crump, & Vadgama, 1995). This type of liquid interface in tissue ensures reduced surface contamination and stabilizes biosensor interfacial contact. When used in vitro, there was retention of the electrode output to within 3% of the original glucose response and a tenfold reduction in baseline drift in the presence of blood over periods of 2 hours to 3 hours. When used in vivo, better tissue con- tact through tissue hydration eliminated any tissue versus blood differences; changes in glucose could also be registered more quickly. Whether improved performance through a liquid interface can have benefits during long-term implantation remains to be verified. 8.13. CONCLUSIONS Although initiated as a basis for simplified measurement of complex parameters, biosensors have turned out to be a remarkable kaleidoscope of interfacial properties and challenges for practical utiliza- tion. The practical issues as yet defy ready transfer to widespread applied measurement. However, the armory of transducers, biomolecules, and formatting techniques, including MEMS, is continuing to expand, and it is likely that this will result in viable new systems. The concepts now being embod- ied extend well beyond the archetypal enzyme-based devices and demonstrate how target molecules