Systems and methods for measuring electrophysiological and electrochemical signals in a portion of a body of a subject are provided. The structure includes an array of electrochemical sensors made of miniaturized multi-layer graphene, an array of electrophysiological electrodes, an integrated front-end readout circuit, and narrow silicon shafts with metal spines. The sensor arrays offer significantly higher sensitivity than conventional methods and enable simultaneous, multi-site measurement of chemical and electrophysiological. The front-end circuit contains features that allow significant improvement in detection of the resulting electrochemical current produced by the electrochemical sensing electrodes. The silicone probes allow measurements deep in the body. In one example, neuroprobes are provided that include an electrophysiological sensor and an amperometric or voltammetric electrochemical sensor for detecting electrochemical signals from neuromodulators such as dopamine in a portion of a brain of a subject.
