Tunable resistive pulse sensing as a tool to monitor analyte induced particle aggregation

Analytical technologies based upon superparamagnetic beads, SPBs, offer a rapid, simple and inexpensive way of separating and purifying the target analyte prior to detection. The SPBs can perform the capture, purification and the signal transduction stages, producing a simple, fast, and sensitive label-free format. Particle aggregation in the presence of the analyte is a common example of such a detection strategy. Herein we demonstrate the key parameters which lead to aggregation. We utilize a tunable resistive pulse sensing, TRPS, technology to follow the aggregation using three different methods of analysis. TPRS allows a comparison in the data treatment using average population values, particle concentration, and a more detailed analysis monitoring the change in aggregate size and frequency. To validate the approach, we use the well-known biotin-avidin binding assay to demonstrate the advantages and limitations of each type of analysis. Also presented are the key parameters that contribute to assay sensitivity such as bead concentration, size, binding capacities and data analysis.