Uncoated quartz resonator as a universal biosensor

We studied dynamic processes in drying drops of model protein-salt solutions, using an uncoated quartz resonator as a biosensor. To measure these processes we developed a method based on recording the dynamics of the Acoustic-Mechanical Impedance (AMI) of a drop as it dried on the surface of a quartz resonator oscillating at a resonant frequency of 60 kHz. The aim of this work was to highlight the role of some components of serum in self-organization processes. Human serum albumin (HSA), fibronectin (Fn), immunoglobulin G (IgG), immunoglobulin M (IgM), bovine serum albumin (BSA), sodium chloride (NaCl), Potassium Chloride (KCl), and nonionic surfactant O(CH(2)CH(2))(n)CH(2)CH(2)OH were used as components of the tested solutions. It was shown that dynamics of the AMI in drying drops were closely related to liquid composition. This approach allowed us to distinguish with good accuracy solutions in which one or more components (proteins or salts) were replaced by other components with the same mass concentration. We assumed that these differences were due to different surface properties and native functions of proteins, and different positions of salts in the Hofmeister line. Our preliminary work demonstrated that the dynamics of phase transitions in drying drops of serum could be used as an informative parameter for medical diagnostics. In this study, we highlight some positions in this cause-effect chain.