Simultaneous neurochemical stimulation and recording using an assembly of biosensor silicon microprobes and SU-8 microinjectors

In this contribution we present multi-channel microinjector arrays fabricated by a reliable three-layer SU-8 process for the local delivery of specific substances into brain tissue. They are designed to be assembled with previously developed, implantable biosensor microprobes for the detection of the neurotransmitter l-glutamate [1]. This combination allows simultaneous chemical stimulation or inhibition of neuronal activity and the monitoring of neurochemical substances in real time. Dimensions down to 150 μm × 150 μm for the cross-section of a 6 mm long single microinjector could be realised, substantially minimising brain damage during implantation. Real-time measurements in the prefrontal cortex and the cerebellum of the rats brain demonstrate (a) the successful in vivo calibration of the biosensor responding to injections of small volumes of the neurotransmitter glutamate in its local vicinity and (b) recorded glutamate release due to stimulation with concentrated potassium solution.