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A highly sensitive wireless-electrodeless quartz-crystal microbalance biosensor with a fundamental resonance frequency of 170 MHz was developed. A blank AT-cut quartz plate of 9.7 Â¿m thick was excited by the line antenna in liquid, and its vibration signals were detected by the other line antenna, achieving the noncontacting measurement of the resonance frequency. The mass sensitivity of the 170 MHz QCM biosensor is better than that of a conventional 5 MHz QCM by three orders of magnitude. This biosensor was applied to detect human immunoglobulin G using Staphylococcus aurous protein A immobilized nonspecifically on both surfaces of the quartz plate. The detection limit is 0.5 pM.