I think there are quite lots of different roles. For example, biomimetic MOx nanomaterials can be used in fabrication of non-enzymatic biosensors, with low-cost and highly environmental stability advantages.
This might be a really tricky question, it strongly depends on the type of oxide you are using, for instance, some oxides will help you isolate, some others will enhance immobilization, serve as mediators in reactions, transduce different signals...