Collagenase-aided insertion of intracortical microelectrode arrays: evaluation of insertion force and chronic recording performance.

Typically intracortical electrodes are required to puncture the intact pia mater during insertion which in the process can lead to brain dimpling and trauma. Furthermore, there is interest in the development of more flexible substrates to reduce relative micromotion after implantation, but such device have difficulty penetrating the pia without buckling. In this paper a strategy for reducing the mechanical integrity of the pia's collagen network by treatment with collagenase is evaluated experimentally. Measurements of the insertion force were carried out with a load cell during computer controlled slow (10 microm/sec) electrode insertion into the cortex of rats. It is shown that controlled application of collagenase reduces the peak insertion force experienced by the microwire arrays around 30% on average. In addition, chronic neural recordings (up to 1 month) suggest that there is no appreciable difference in the signal quality as recorded from the collagenase treated and the control sites. The results suggest the technique is useful for reducing insertion forces without compromising neural recording capabilities.