An integrated flexible implantable L-glutamate sensor

In this work, we have developed a fully integrated implantable probe on polyimide-film substrate for sensing neurotransmitters and recording extracellular action potentials simultaneously. The flexibility of the probe helps to prevent scar forming in tissues aiming for long-term in vivo monitoring. An Ag/AgCl reference electrode was integrated in the same probe with the Au/Cr or Pt/Cr working electrodes, which presented an integrated, compact and robust system. Several electrode configurations have been designed for implantation at various locations in the central nervous system. The prototype device for proof of principle is an enzyme-based electrochemical L-glutamate sensor using L-glutamate oxidase. A comparison between Au and Pt thin films was conducted by cyclic voltammtry. The enzyme was deposited with a multiple-step process on the working electrodes followed by meta-Phenylenediamine coating for better selectivity. The self-referencing technique was also used to enhance both the limit of detection and selectivity. The assembled sensors were calibrated and tested at various concentrations of L-glutamate at the presence of interfering molecules showing good sensitivity and selectivity.