Viability and resolution of sensing hemolysis with a capacitive sensor

Abstract

Background: Monitoring lysis in cell's suspensions can be a good indicator of cell's integrity and health. The current techniques to measure the number of lysed cells in some process are generally time consuming. Objective: In this paper, we investigate the viability of a simple method for sensing hemolysis in real time through the electrical impedance of a parallel-plate capacitor that holds a biological cell suspension. Materials and methods: The method is based on measuring variations of the effective dielectric function of an erythrocyte suspension during a lysis process induced by osmotic stress. Our sensor is strongly affected by the so-called electrode polarization phenomenon which prevents sensing variations of the real part of the effective dielectric function. However, measurements of the imaginary part, and thus of the electrical resistivity of the suspension, is straight forward. Results: We show that from resistivity measurements, it is possible to sense variations of the lysed erythrocytes' volume fraction with a resolution better than 0.1%. Conclusions: The proposed sensor can offer a high resolution in monitoring hemolysis and is a viable option for developing new rapid diagnostic medical tests.

Simplifying Capacitive Sensor Readout Using a New Direct Interface Circuit

“…Hence, for values of C X greater than a few hundred pF, the influence of C off in ( 14) is negligible and ( 11) can be used instead. In any case, with these data and using (14), the Normalized Acquisition Time is approximately 0.12 ms/nF (70.96 ms / 561 nF), more than three orders of magnitude smaller than in [23].…”

“…Despite the simplicity of the proposal, the error in the estimation of C X is lower than that of other more complex readout circuits. These results are obtained for a much larger range of capacities, allowing the new DIC to be used in applications where it was impossible to use this type of circuit until now, as in [9], [10], [12]- [14].…”

“…Regardless of the value of C X , this situation comes about whenever enough large values of R A and R B are chosen. In terms of uncertainty, for (14) we can find a measurement of quality in the estimate of C X , u(C X )/C X :…”

“…Sensor capacitance in such applications varies from tens of picofarads to just a few nanofarads. Furthermore, interesting new applications have recently been proposed for this type of sensor, such as DNA detection [10], position and displacement [11], dew point measurement [12], water in crude oil [13], and sensing hemolysis [14], where capacitance varies in a wide range, from hundreds of picofarads to hundreds of nanofarads.…”