Studies on effect of sample circulation on sensing performance of protein C immunosensor

Protein C (PC) is an important anti-coagulant and anti-thrombotic in blood plasma. PC deficiency may lead to severe thrombotic complications such as stroke and heart attack. The frequency of PC deficiency in general population is estimated to be 0.2%. Early diagnosis of PC deficiency is critical for preventing fatal thrombo-embolic episodes. A realtime, cost effective, and highly sensitive fiber-optic PC immunosensor is currently under development in our research group. After injection of the PC sample to sensor chamber, PC diffuses to the fiber surface from bulk solution, followed by immunoreaction with antibodies on the surface. The signal intensity from PC in plasma was much lower than in pure buffer due to high viscosity of blood plasma. To increase the signal intensity, convective mass transfer was applied during incubation. A sample circulation unit was also designed to circulate sample within enclosed system to provide continuously convective mass transfer of sample with minimum sample volume. Micropumps and microvalves are being investigated to make a microfluidic system for minimization of sample volume and a more precise measurement. The ultimate goal is to automate the sample circulation unit to be incorporated in an automatic sensing cartridge for PC measurement.