Figure 1.

(A) Schematic illustrations of two different xanthine (XAN) biosensing schemes employing xerogel scaffolds for immobilized xanthine oxidase enzyme (XOx), polyurethane-based semi-permeable membranes for selectivity, and strategically incorporated NMs: (a) gold NP-doped xerogels and (b) surface modification of the working electrode interface with CNTs. In either scenario, the inclusion of NMs typically results in signal enhancement that subsequently leads to more sensitive biosensing, faster response times, and extended linear ranges, as shown by the illustrative example data of (B) amperometric I-t and (C) corresponding calibration curves showing the effect with and without Au-NP incorporation (A(a)—left) for xanthine biosensing. Note: Similar signal enhancements from the CNT scheme (A(b)—right) were also demonstrated for XAN (Supporting Information, Figure S1).