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FAST WHOLE BLOOD TESTING FOR DETECTING BIOMARKERS BY SIZE-EXCLUSION SPR SENSING

This paper presents a simple and fast protein detection from a whole blood sample using an SPR (surface plasmon resonance) sensor chip integrated with in situ blood cell separation function. We demonstrated the separation of plasma from a whole blood just by dispensing the single drop on the sensor chip and the detection of IgG molecules in it. This sensor chip allows the detection of IgG molecules of a concentration lower than the physiological value and the fast detection time (< 12 min). KEY WORD SPR, Blood separation, Blood testing, INTRODUCTION A whole blood testing is commonly used for early detection of diseases by detecting biomarker proteins in blood serum (ex. AFP and PSA). Conventional methods involve a time consuming procedure of blood cell separation using external equipments such as a centrifuge and filtration device, preventing the miniaturization of the system. Although various kinds of cell separation techniques have been developed in LOC field, including a microfluidic and electrostatic cell separations[1], most of them still require external devices such as a pump, tube, valve, and power supply. To overcome these drawbacks, we propose a novel technique for protein detection from a whole blood sample using a “Size-exclusion SPR sensor chip” (filter SPR chip) that we have previously developed for detecting particle aggregation [2]. A filter SPR chip has a microslit array on a flat gold surface, with the gap of 3 m smaller than a cell size (Figure 1). Because the SPR sensing area is limited to about 300 nm above the gold surface, the walls of 5 m height exclude blood cells from the sensing area, thus only a serum can touch the sensor surface, where ligands are immobilized to capture analytes, allowing the specific detection of proteins in the serum as the SPR angle shift. This method needs no external equipment for cell filtration, because it is driven by their sedimentation and diffusion. In addition, the short distance between the filtration and the sensing area enables us to detect proteins immediately after applying samples. Non-labeling of SPR sensing also allows the one-step procedure; just applying sample to a ligand-immobilized chip.