The present invention generally relates to nanoscale wires, including to nanoscale wires used as sensors. In some cases, the nanoscale wires may be used to directly determine analytes, even within relatively complicated environments such as blood, unlike many prior art techniques. In some aspects, the nanoscale wire form at least a portion of the gate of a field-effect transistor, and in certain aspects, different periodically- varying voltages or other electrical signals may be applied to the field-effect transistor. For example, in one set of embodiments, sinusoidally- varying voltages of different frequencies may be applied to the nanoscale wire and the source electrode of the field-effect transistor. The electrical conductance or other properties of the nanoscale wire in response to the periodically- varying voltages may then be determined and used to determine binding of the species.