Small molecule detection in normal ionic strength buffers

Abstract

A system for detecting target molecules includes a sample well defining a sensing region and two electrode regions, a sensor positioned in the sensing region and sensitized to the target molecules, an electrode positioned in each electrode region and configured to expose the sensor to a frequency-modulated electric field, and a detector configured to detect both an amplitude of oscillation of the sensor at a frequency of the modulated electric field and a direction of a displacement of the sensor. The sensing region defines a channel between the electrodes, and a ratio of a current density at a center of the sensing region to a current density at one of the electrodes is at least 2. The system allows detection of target molecules in a normal ionic strength buffer (e.g., having an ionic strength in a range of about 10 mM to about 1 M).