Gold is the most widely used electrode material for bioelectronic applications due to its high electrical conductivity,
good chemical stability and proven biocompatibility. However, gold adheres only weakly to widely used substrate
materials such as glass and silicon oxide, typically requiring the use of a thin layer of chromium between the
substrate and the metal to achieve adequate adhesion. Unfortunately, this approach can reduce biocompatibility
relative to pure gold films due to the risk of the underlying layer of chromium becoming exposed. Here we report on
an alternative adhesion layer for gold and other metals formed from a thin layer of the negative-tone photoresist SU8,
which we find to be significantly less cytotoxic than chromium, being broadly comparable to bare glass in terms of
its biocompatibility. Various treatment protocols for SU-8 were investigated, with a view to attaining high
transparency and good mechanical and biochemical stability. Thermal annealing to induce partial cross-linking of the
SU-8 film prior to gold deposition, with further annealing after deposition to complete cross-linking, was found to
yield the best electrode properties. The optimized glass/SU8-Au electrodes were highly transparent, resilient to
delamination, stable in biological culture medium, and exhibited similar biocompatibility to glass.