Bioelectrochemistry for in vivo analysis: Interface engineering toward implantable electrochemical biosensors

With a long history in research, bioelectrochemistry has emerged as a hot spot in the development of implantable biosensors with desired selectivity, sensitivity and spatiotemporal resolution for accurate analysis of electroinactive species in vivo. To catalyze electrode reactions (oxidation or reduction) of target analytes, enzymes are employed as the efficient bioelectrocatalysts immobilized on the electrodes. In bioelectrochemistry, the biggest challenge is the interfacial electron transfer between the redox active centers of enzymes and electrode surfaces. Besides, enzymatic electrodes are prone to inhibition and inactivation by environmental factors (co-substrates, inhibitors, pH, etc.). Rational design of the electrode surface/interface is necessitated to fulfill the requirements of in vivo applications. This mini review covers the recent and representative progress on interface engineering to enable bioelectrochemistry for in vivo analysis with an emphasis on heterogeneous electron transfer, oxygen dependence and microenvironment tolerance of bioelectrodes and self-powered electrochemical biosensors as well.