The biodegradability and biocompatibility of ZnO wires in biofluid has been studied by investigating the interaction of the wires with deionized water, ammonia, NaOH solution, and horse blood serum. The results show that ZnO can be dissolved into mineral ions by these liquids within a few hours (see figure) and that ZnO is a bio-safe, nontoxic material for in vivo biosensing and biodetection.