Influence of molecular size and zeta potential in electrokinetic biosensing

• Published in: Biosensors & bioelectronics Vol. 152; p. 112005
• Main Authors: Sahu, Siddharth Sourabh, Stiller, Christiane, Cavallaro, Sara, Karlström, Amelie Eriksson, Linnros, Jan, Dev, Apurba
• Format: Journal Article
• Language: English
• Published: England Elsevier B.V 15.03.2020
• Subjects: Algorithms; Biosensing Techniques - methods; Biosensor; Electricity; Electrochemical Techniques - methods; Electrokinetics; Improved sensitivity; Influence of molecular size and charge; Particle Size; Proteins - analysis; Static Electricity; Streaming current; Surface Properties; Zeta potential; Influence of molecular size and charge; Improved sensitivity; Streaming current; Zeta potential; Biosensor; Electrokinetics
• ISSN: 0956-5663; 1873-4235; 1873-4235
• DOI: 10.1016/j.bios.2020.112005

Electrokinetic principles such as streaming current and streaming potential are extensively used for surface characterization. Recently, they have also been used in biosensors, resulting in enhanced sensitivity and simpler device architecture. Theoretical models regarding streaming current/potential studies of particle-covered surfaces have identified features such as the particle size, shape and surface charge to influence the electrokinetic signals and consequently, the sensitivity and effective operational regime of the biosensor. By using a set of well-characterized proteins with varying size and net surface charge, this article experimentally verifies the theoretical predictions about their influence on the sensor signal. Increasing protein size was shown to enhance the signal when their net surface charge was either opposite to that of the sensor surface, or close to zero, in agreement with the theoretical predictions. However, the effect gradually saturated as the protein size exceeded the coulomb screening length of the electrolyte. In contrast, the proteins containing the same type of charge as the surface showed little or no difference, except that the signal inverted. The magnitude of the surface charge was also shown to influence the signal. The sensitivity of the technique for protein detection varied over two orders of magnitude, depending upon the size and surface charge. Furthermore, the capacity of the electrokinetic method for direct electrical detection of various proteins, including those carrying little or no net electric charges, is demonstrated. •The size and charge of particles affects their signal in electrokinetic biosensing.•This was shown for proteins of varying size and zeta potential by streaming current measurements.•The sensitivity varied over two orders of magnitude for the proteins studied.•The results were explained by a pre-existing theoretical model.•The possibility to enhance the signal by varying the measurement conditions was shown.