Layer-by-layer electrochemical biosensors configuring xanthine oxidase and carbon nanotubes/graphene complexes for hypoxanthine and uric acid in human serum solutions.

A selective biosensing platform for the determination of hypoxanthine (Hx) and uric acid (UA) concentrations in both buffer and human serum sample solutions was developed. The biosensor features the layer-by-layer (LbL) self-assembly of negatively charged xanthine oxidase (XOD) and positively charged poly(diallyldimethyl ammonium chloride) (PDDA) wrapped oxidized multi-walled carbon nanotubes and graphene (CNTs-G) complexes (PDDA-CNTs-G) on screen printed carbon electrode (SPCE) surfaces. Catalytic responses of the XOD modified biosensor with the chosen optimum number of layers for LbL assembly on SPCE towards Hx in buffer solutions were first investigated using both cyclic and square wave voltammetries.