Apparatuses, systems, and methods are disclosed for target detection based on collateral cleavage of a reporter by an enzyme. A biologically gated transistor may include a channel and a reporter moiety immobilized to the channel. The state of the reporter moiety may affect one or more output signals from the biologically gated transistor when excitation conditions are applied to the biologically gated transistor and a sample fluid is applied in contact with the channel. A sample fluid may include an enzyme configured to activate in response to a target nucleic acid to cleave the reporter moiety. Excitation circuitry may apply the excitation conditions, and measurement circuitry may measure output signals from the biologically gated transistor. An analysis module may determine a parameter relating to presence of the target nucleic acid, based on the one or more measurements.