Development of a Multichannel Quartz Crystal Microbalance with High Sensitivity for Simultaneous Detections of Multi-substances and Its Application as Biosensors

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In this research project, development of a highly sensitive multichannel quarts crystal microbalance (MQCM) was carried out. Small QCM electrodes, the diameter of which was less than 2mm, were fabricated on a single quartz plate (22mmx22mm). That each QCM was able to operate as an independent sensor device without interference from other QCM electrodes on the same MQCM was successfully confirmed in both air and liquid phases. Ih addition, high sensitivity of QCM technique was maintained by increasing resonant frequency by decreasing the thickness of a quartz crystal plate. The major subject of this research project was to develop a highly sensitive biosensor based on MQCM technology for quantitative, simultaneous detections of several substances. To reach this goal, different specficity should be given to each of QCM electrodes on a MQCM. Monoclonal antibodies, anti-HSA and anti-BSA, were introduced to the surface of channel 1 and channel 2, respectively, on a 4-channel MQCM. When the antibody-modified MQCM was contacted with a solution containing both HSA and BSA, the resonant frequency of each channel decreased, the magnitude of which was linearly dependent on a concentration of the corresponding antigen. However, at a high antigen concentration, nonspecific adsorption of antigens was observed. Magnetic microbeads, the surface of which was previously modified with, for example, various antibodies, were considered as a technique to give specificity to QCM electrode surface. Using these magnetic microbeads which were readily collected on a QCM electrode surface with a small magnet and removed from the surface after measurements, repetitive use of MQCM was expected, decreasing the cost of the measurements. We expect highly sensitive sensors based on MQCM technology developed in this research project will be useful for detections of many diseases including cancers and tumors at their very early stages.