Abstract
Second-generation glucose biosensors are presently the mainstream commercial solution for blood glucose measurement of diabetic patients. Screen-printed carbon electrodes (SPCEs) are the most-used substrate for glucose testing strips. This study adopted hydrophilic and positively charged α-poly-l-lysine (αPLL) as the entrapment matrix for the immobilization of negatively charged glucose oxidase (GOx) and ferricyanide (FIC) on SPCEs to construct a disposable second-generation glucose biosensor. The αPLL modification is shown to facilitate the redox kinetics of FIC and ferrocyanide on the SPCEs. The SPCEs coated with 0.5 mM GOx, 99.5 mM FIC, and 5 mM αPLL had better sensitivity for glucose detection due to the appreciable effect of protonated αPLL on the promotion of electron transfer between GOx and FIC. Moreover, the SPCEs coated with 0.5 mM GOx, 99.5 mM FIC, and 5 mM αPLL were packaged as blood glucose testing strips for the measurement of glucose-containing human serum samples. The glucose testing strips had good linearity from 2.8 mM to 27.5 mM and a detection limit of 2.3 mM. Moreover, the 5 mM αPLL-based glucose testing strips had good long-term stability to maintain GOx activity in aging tests at 50 °C.
Highlights
Diabetes mellitus is the most common endocrine disease and is a disorder of carbohydrate metabolism producing high glucose levels in the blood, leading to different dysfunctions such as nerve degeneration, kidney failure, and blindness [1,2,3]
The results suggest that αPLL has good biocompatibility for the protection of glucose oxidase (GOx)
The cleaned Screen-printed carbon electrodes (SPCEs) were electrochemically oxidized at 2 V for 300 s in 100 mM NaOH to increase the edge-plane-to-basal-plane ratio of the graphite, facilitating the electron transfer rate [34,35]
Summary
Diabetes mellitus is the most common endocrine disease and is a disorder of carbohydrate metabolism producing high glucose levels in the blood, leading to different dysfunctions such as nerve degeneration, kidney failure, and blindness [1,2,3]. Diabetic patients must take precise daily measurements of their blood glucose concentrations. Several methods, including metamaterial-based electromagnetic spectroscopy [4], fluorescence [5], near-infrared spectroscopy [6], and electrochemistry [7], have been developed for glucose detection. Most commercial glucose biosensors adapt electrochemical methods via the catalysis of glucose oxidase (GOx) or glucose dehydrogenase to detect glucose concentration [8]. A variety of self-monitoring glucose biosensors have been commercialized for point-of-care testing (POCT) [9,10,11]. Second-generation glucose biosensors using mediators dominate the POCT product market due to their low cost and good sensing properties with resistance to the impact of dissolved oxygen [12]
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