170-MHz electrodeless quartz crystal microbalance biosensor : Capability and limitation of higher frequency measurement

We develop a highly sensitive quartz crystal microbalance (QCM) biosensor with a fundamental resonance frequency of 170 MHz. A naked AT-cut quartz plate of 9.7 μm thick is set in a sensor cell. Its shear vibration is excited by the line wire, and the vibration signals are detected by the other line wire, achieving the noncontacting measurement of the resonance frequency. The mass sensitivity of the 170 MHz QCM biosensor is 15 pg/(cm² Hz), which is better than that of a conventional 5 MHz QCM by 3 orders of magnitude. Its high sensitivity is confirmed by detecting human immunoglobulin G (hIgG) via Staphylococcus protein A immobilized nonspecifically on both surfaces of the quartz plate. The detection limit is 0.5 pM. Limitation of the high-frequency QCM measurement is then theoretically discussed with a continuum mechanics model for a plate with point masses connected by elastic springs. The result indicates that a QCM measurement will break down at frequencies one-order-of-magnitude higher than the local resonance frequency at specific binding cites.Hirotsugu Ogi, Hironao Nagai, Yuji Fukunishi, Masahiko Hirao, and Masayoshi Nishiyama. 170-MHz electrodeless quartz crystal microbalance biosensor: Capability and limitation of higher frequency measurement. Analytical Chemistry, 2009, 81(19), 8068-8073. ©2009 American Chemical Society. https://doi.org/10.1021/ac901267b

Replacement-free electrodeless quartz crystal microbalance biosensor using nonspecific-adsorption of streptavidin on quartz

This paper proposes a replacement-free and surface-modification-free quartz crystal microbalance (QCM) biosensor. With the use of significant nonspecific adsorption of streptavidin on naked quartz surfaces, target analyte is detected through biotin-tagged receptors on streptavidin. The wireless-electrodeless QCM technique is developed with a 30 μm thick AT-cut quartz plate, whose fundamental resonance frequency is 55 MHz, and the naked quartz surfaces are used for the nonspecific adsorption of streptavidin. Once it is installed in the sensor cell, it can be used semipermanently; it never needs to be replaced. The equilibrium dissociation constant of streptavidin on quartz is determined to be 1.3 × 10⁻⁷M. The flow rate affected the number of the adsorbed streptavidin on quartz as well as the binding velocity.Hirotsugu Ogi, Ken Okamoto, Hironao Nagai, Yuji Fukunishi, and Masahiko Hirao. Replacement-free electrodeless quartz crystal microbalance biosensor using nonspecific-adsorption of streptavidin on quartz. Analytical Chemistry, 2009, 81(10), 4015-4020. ©2009 American Chemical Society. https://doi.org/10.1021/ac9004524

Multichannel wireless-electrodeless quartz-crystal microbalance immunosensor

We develop the wireless-electrodeless multichannel quartz-crystal microbalance (QCM) biosensor using quartz plates of slightly different thicknesses. Their shear vibrations are simultaneously excited and detected by a pair of antenna wires to perform the noncontacting measurement. Their fundamental resonance frequencies are between 43 and 55 MHz, and vibrations at up to 10 channels are measured in liquids. Owing to high affinity of naked quartz surfaces for proteins, we immobilized various receptor proteins on different quartz plates nonspecifically and detected various antigen-antibody reactions separately. The exponential coefficient of the frequency change, rather than the amount of the frequency decrease, is found to be useful for distinguishing between specific and nonspecific binding reactions.Hirotsugu Ogi, Hironao Nagai, Yuji Fukunishi, Taiji Yanagda, Masahiko Hirao, and Masayoshi Nishiyama. Multichannel wireless-electrodeless quartz-crystal microbalance immunosensor. Analytical Chemistry, 2010, 82(9), 3957-3962. ©2010 American Chemical Society. https://doi.org/10.1021/ac100527r

Development of 170MHz electrodeless quartz-crystal microbalance immunosensor with nonspecifically immobilized receptor proteins

Staphylococcus aureus protein A (SPA) shows high nonspecific binding affinity on a naked quartz surface, and it can be used as the receptor protein for detecting immunoglobulin G (IgG), the most important immunoglobulin. The immunosensor ability, however, significantly depends on the immobilization procedure. In this work, the effect of the nonspecific immobilization procedure on the sensor sensitivity is studied using a homebuilt electrodeless quartz-crystal microbalance (QCM) biosensor. The pure-shear vibration of a 9.7-mm-thick AT-cut quartz plate is excited and detected in liquids by the line antenna located outside the flow channel. SPA molecules are immobilized on the quartz surfaces, and human IgG is injected to monitor the binding reaction between SPA and IgG. This study reveals that a long (nearly 24 h) immersion procedure is required for immobilizing SPA to achieve the tight biding with the quartz surfaces.Hirotsugu Ogi, Hironao Nagai, Yuji Fukunishi, Taiji Yanagida, Masahiko Hirao and Masayoshi Nishiyama. Development of 170MHz electrodeless quartz-crystal microbalance immunosensor with nonspecifically immobilized receptor proteins. Japanese Journal of Applied Physics, 2010, 49(7S), 07HD07. https://doi.org/10.1143/JJAP.49.07HD07

Aggregation behavior of amyloid β₁₋₄₂ peptide studied using 55 MHz wireless-electrodeless quartz crystal microbalance

A homebuilt wireless-electrodeless high frequency quartz crystal microbalance is adopted for long-time monitoring of the aggregation behavior of amyloid β₁₋₄₂ peptide in a flow-cell system. The monomer amyloid peptides are immobilized on both surfaces of the crystal, and an amyloid-β solution is injected. The monotonic frequency decrease indicates aggregation on the crystal, which yields aggregation rate. Aggregation is observed even at a peptide concentration as low as 550 nM.Hirotsugu Ogi, Kenichi Hatanaka, Yuji Fukunishi, Hironao Nagai, Masahiko Hirao and Masayoshi Nishiyama. Aggregation behavior of amyloid β₁₋₄₂ peptide studied using 55 MHz wireless-electrodeless quartz crystal microbalance. Japanese Journal of Applied Physics, 2009, 48(7S), 07GF01. https://doi.org/10.1143/JJAP.48.07GF01