A simulated sunlight-activated plastic mimic enzyme for dual-mode detection of D-penicillamine and serum iron

No reports disclosed that whether the plastic centrifuge tube with intrinsic photoenzyme activity can be used for the specific sensing of pharmaceuticals and biomarkers in biofluids so far. We herein report the plastic eppendorf (EP) tube as both reaction vessel and sunlight-activated plastic mimic enzyme for colorimetric/smartphone dual-mode detection of D-penicillamine (D-PA) and iron (Ⅲ) ions in goat and rabbit serums accordingly. The photooxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) combined with simulated sunlight-activated EP tube was selectively inhibited by adding D-PA, and the absorbance at 652 nm of oxidized TMB decreased. Good linearity between the absorbance variation (or R/(R + G + B)) and D-PA level ranging from 10 to 300 µM was obtained, and the limits of detection (LOD) were determined as 8.50 μM (colorimetric) and 6.92   μM (smartphone). Furthermore, the polyvinyl alcohol hydrogel encapsulated TMB in EP tube as a smartphone biosensor had been triumphantly used to monitor D-PA level in goat serum. Interestingly, the adsorption band of photo-oxidized EP tube-TMB system inhibited by D-PA gradually increased as the enhancement of iron (Ⅲ) ions concentration. Based on the “on–off-on” effect, a sensitive and selective method was further used for selectively sensing iron (Ⅲ) in rabbit serum. Notably, the dual-mode sensing platforms exhibited outstanding detection performance, with LOD values as low as 0.50 µM and 0.65 µM respectively. In short, this work not only excavated a photoactivated-plastic mimics, but also developed a robust, low-cost, simple and sensitive biosensor for simultaneous detection of D-PA and Fe (Ⅲ) ions in biofluids. The current photoactivated sensor does not requires the introduction of exogenous catalyst except for simulated sunlight, plastic tube and chromogenic substrate.