Resumen de Diseño y evaluación de un biosensor basado en resonadores de cristal de cuarzo (QCR) para caracterizar muestras biológicas relacionadas con enfermedades artríticas
Quartz crystal resonator is widely used as biosensor device due to its high sensitivity to physicochemical phenomena occurring on its electrode surface, the reproducibility of its measures and its easy use. Sauerbrey[1] was the first to show that the quartz crystal resonator can be used as a microbalance useful for characterizing small layers of mass deposited on the crystal electrode. Sauerbrey observed that if a thin layer of rigid material is deposited on the quartz crystal, the crystal and the deposited material will vibrate at the same frequency generating a change in the initial resonance frequency of the crystal. Specifically, the resonance frequency decreases when increases the deposited mass.
The quartz crystal can also operate in fluid medium. In this case, in addition to the frequency shift of the crystal, there is a significant loss in the quality factor of the resonator. For Newtonian fluids (constant viscosity), Kanazawa and Gordon [2] note that the frequency shift and the change in the quality factor of the crystal, depends on the density and viscosity of the liquid deposited. This phenomenon allows to use quartz crystal resonators as small viscometers. The density of the fluid to be analyzed must be known.
For deposition of viscoelastic fluids, the measure of resonance frequency shift is not sufficient to obtain the fluid viscosity value. Therefore, it is necessary to measure a second variable (the half band half width - Γ) to obtain the correct value of viscosity of the deposited fluid [3]. For pseudoplastic fluids (apparent viscosity dependent of the shear rate applied), it is necessary a mathematical model to explain the behavior of the fluid viscosity at different shear rates. In particular, for the analysis of samples with pseudoplastic behavior, Rouse model has been chosen because it explains in sufficient detail the pseudoplastic behavior and is simple to apply to the experimental measurements.
In this work, the design of a biosensor based on a quartz crystal resonator (QCR) for viscometric characterization of biological samples emulating the behavior of the synovial fluid is proposed.
Synovial fluid is a mixture of plasma and hyaluronic acid dialysate with pseudoplastic behavior. Its main function is to act as a lubricant in joints keeping to a minimum the friction between the bones, especially during movement [4–7].
The decrease of the hyaluronic acid in the synovial fluid has been associated with arthritic disease since the lubricating properties of synovial fluid depend on its viscosity and the same time, this viscosity depends on the concentration of hyaluronic acid in the sample. [4–8] It is widely documented the relationship between changes in viscosity of the synovial fluid and joint conditions [4–13]. Based on this relationship between hyaluronic acid and some arthritic diseases, the synovial fluid analysis can contribute fundamental information to diagnosis and treatments for joint diseases.
Based on the above, the biomedical application proposed is intended to provide the QCR’s as an additional tool for the diagnosis of arthritic diseases such as osteoarthritis and rheumatoid arthritis analyzing synovial fluid viscosity. Because this is a preliminary work, hyaluronic acid dilutions are used in order to emulate the behavior of synovial fluid.
