Effect of Poly-l-Lysine Polycation on the Glucose Oxidase/Ferricyanide Composite-Based Second-Generation Blood Glucose Sensors

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.

Enzyme-Mimicking Materials from Designed Self-Assembly of Lysine-Rich Peptides and G-Quadruplex DNA/Hemin DNAzyme: Charge Effect of the Key Residues on the Catalytic Functions

“…In this work, we designed ε-polylysine (ε-PLL) or α-polylysine (α-PLL) peptides to assemble with G-quadruplex DNA and hemin to fabricate peroxidase-like active sites (Figure ). Despite both having amine as the side chain group, ε-PLL differs from α-PLL in the p K a of NH 2 , 7.6 and 10.3–10.5. − Under studied reaction conditions, these two peptides have distinct charged states and may bond to Fe–H 2 O 2 in different manners, one more like a Lewis base and the other more like a Lewis acid. The results showed that the DNA and the polylysine peptides accelerated the hemin-catalyzed reactions synergistically, and the complex containing ε-PLL was more active than that containing α-PLL, suggesting the superiority of a base group over an acid group that was located at the distal side of hemin.…”

Non-Invasive Blood Glucose Monitoring Technology: A Review

“…Common electronic media include ferrocene-based polymers and derivatives (FBPDs), ferricyanide (FIC), hydroquinone (HQ) and conductive organic salts (such as tetrathiafulvalene (TTF), tetracyanoquinodimethane (TCNQ), etc.) [20,24,25]. Among them, FBPDs have the advantages of excellent redox performance, easy of modification, stability, large specific surface area and good electrical conductivity.…”

“…Due to the mutual attraction between positive and negative charges, they used positively charged α-poly-L-lysine (αPLL) as the entrapment matrix for the better immobilization of negatively charged GOx and FIC. The screen-printed strip GBs had good linearity from 2.8 mM to 27.5 mM and a detection limit of 2.3 mM [24]. However, ferrocene or ferricyanide derivatives are generally at risk of permeation and biotoxicity and are not recommended for use in vivo devices [18].…”

The Impact of Recent Developments in Electrochemical POC Sensor for Blood Sugar Care

“…The second-generation GOx sensor uses an electron transfer mediator instead of oxygen as the electron acceptor, which can overcoming the oxygen limitation of the first-generation GOx sensor ( Lin et al, 2019 ; Yadav et al, 2019 ). The electron mediators are small, soluble redox-active molecules such as ferrocene derivatives, ferricyanides, conductive organic salts and quinones.…”