A Strategy for Chemical Sensing Based on Frequency Tunable Acoustic Devices

• Published in: Analytical chemistry (Washington) Vol. 73; no. 7; pp. 1577 - 1586
• Main Authors: Sindi, Hayat S, Stevenson, Adrian C, Lowe, Christopher R
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.04.2001
• Subjects: Acoustics; Biological and medical sciences; Biosensing Techniques - methods; Biosensors; Biotechnology; Calibration; Chemistry; Electromagnetic Phenomena; Fundamental and applied biological sciences. Psychology; Humans; Immunoglobulin G - analysis; Methods. Procedures. Technologies; Phosphorylase b - analysis; Proteins - analysis; Sensors; Silicon Dioxide; Various methods and equipments; Performance evaluation; Acoustic wave resonator; Biosensor; Resonance frequency; Biological macromolecule; Acoustic sensor; Chemical sensor; Electromagnetic device; Frequency weighting; Immunosensor
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac000820u

A new acoustic sensor geometry, the magnetic acoustic resonant sensor (MARS), is described. The device comprises a circular 0.5-mm-thick resonant plate fabricated from a wide variety of nonpiezoelectric materials and coated on the underside with a 2.5-μm-thick aluminum film. Harmonic radial shear waves over at least a 2 orders of magnitude frequency range can be induced in the resonant plate by enhanced magnetic direct generation using a noncontacting rf coil and NdFeB magnet. Mass loading with adherent aluminum films produced frequency changes of 106 Hz/nm (40.8 Hz/ng·mm-2), while contact with viscous fluids resulted in maximum changes of 15 446 Hz/cP. At an operating frequency of 50 MHz, the device detected viscosity changes as low as 0.0006 cP. The adsorption of proteins such as human IgG and the binding of a complementary antigen, goat anti-human IgG, on the upper nonmetallized surface of the device has been monitored with a detection limit of ∼75 ng/mL. The binding of substrates and allosteric effectors to glycogen phosphorylase b has provided evidence that the device is very sensitive to viscoelastic changes in adsorbed proteins. The MARS device generates radial shear acoustic waves over a broad bandwidth that are unaffected by the conductivity of the solution. These results suggest that simple metal, glass, crystalline, or polycrystalline plates can be used as a new type of tunable acoustic immunosensor.