  The detection of quantal exocytic events from neurons and neuroendocrine
cells is a challenging task in neuroscience. One of the most promising
platforms for the development of a new generation of biosensors is diamond, due
to its biocompatibility, transparency and chemical inertness. Moreover, the
electrical properties of diamond can be turned from a perfect insulator into a
conductive material (resistivity Ohm cm) by exploiting the metastable nature of
this allotropic form of carbon. A 16 channels MEA (Multi Electrode Array)
suitable for cell culture growing has been fabricated by means of ion
implantation. A focused 1.2 MeV He+ beam was scanned on a IIa single-crystal
diamond sample (4.5x4.5x0.5 mm3) to cause highly damaged sub-superficial
structures that were defined with micrometric spatial resolution. After
implantation, the sample was annealed. This process provides the conversion of
the sub-superficial highly damaged regions to a graphitic phase embedded in a
highly insulating diamond matrix. Thanks to a three-dimensional masking
technique, the endpoints of the sub-superficial channels emerge in contact with
the sample surface, therefore being available as sensing electrodes. Cyclic
voltammetry and amperometry measurements of solutions with increasing
concentrations of adrenaline were performed to characterize the biosensor
sensitivity. The reported results demonstrate that this new type of biosensor
is suitable for in vitro detection of catecholamine release.
