The sensor’s electrical connections were made by Navitoclax mechanism low-conductivity silver-reinforced epoxy. The experimental characterizations of the sensor’s response to varying Bcl-2 concentrations were performed in a custom-designed oscillatory circuit. The oscillatory circuit was composed of two RF amplifiers connected in series, a frequency counter, an oscilloscope (to monitor the signal), and the sensor, which was used as the feedback element determining the oscillation frequency. The characterization was performed by using multiple sensors with up to 10 tests conducted on a sensor by cleaning the delay path with 1.5 M NaCl solution in de-ionized (DI) water. The tests were done by placing 80 ��L droplets of Bcl-2 solutions (in Dulbecco’s phosphate-buffered saline��DPBS) with various concentrations on the delay path.
Quantification of the Bcl-2 concentration was achieved by monitoring the frequency shift for each solution. The frequency shift was caused by the change in surface density of the delay path (mass loading). As surface density increased by protein adhesion, SAW velocity decreased, resulting in a reduction in the oscillation frequency that was measured by the frequency counter. The frequency shift for each tested concentration was measured, and the sensor was successful in detecting Bcl-2 concentrations as low as the target concentration, 0.5 ng/mL. It was observed that the frequency shift had a linear trend corresponding to increasing Bcl-2 concentration. Additionally, minimal frequency shift was observed for the control DPBS solution with no Bcl-2 present.Figure 1.
Illustration of the sensor.In the following section, important design parameters, fabrication of the sensor, and surface functionalization are discussed in detail. In Section 3, the electrical characterization of the sensor and results are presented. The final section covers the discussions and conclusion along with the future work.2.?Sensor Design and Fabrication2.1. Sensor DesignThe sensor uses shear horizontal surface acoustic waves, which are frequently used for liquid-loaded biosensing applications. In SH-SAWs, the particle displacement is in the plane of the surface (unlike normal-to-surface displacement of Rayleigh waves). SH-SAWs are not affected or damped by liquid loading, as compared to Rayleigh waves, in which the particle displacement is directly Drug_discovery coupled with the liquid on top and highly damped by mass loading of the liquid itself.
Thus, Rayleigh waves are virtually insensitive to mass loading changes in liquid sensing applications. On the other hand, almost all SH wave propagation
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