Glucose biosensor based on the highly efficient immobilization of glucose oxidase on layer-by-layer films of silsesquioxane polyelectrolyte

In this paper, LbL films were prepared between 3-n-propylpyridinium silsesquioxane polymer (SiPy+Cl−) and copper (II) tetrasulfophthalocyanine (CuTsPc), denoted as (SiPy+Cl−/CuTsPc)n. The multilayer film modified electrode (SiPy+Cl−/CuTsPc)2 showed excellent electrocatalytic activity for H2O2 reduction with a wide linear range of response, high sensitivity and low detection limit. This film was modified with glucose oxidase (GOx) and a film of Nafion (Nf) which was used to prevent the GOx from leaking off. FTIR, fluorescence spectrometry and CD measurements showed that the GOx enzyme retains its native secondary structure when immobilized on the LbL film. The resulting (SiPy+Cl−/CuTsPc)2(SiPy+Cl−/GOx/Nf) biosensor displayed a current response which varies linearly with the concentration of glucose in the range from 1 to 10 mmol L−1 with a detection limit of 0.16 mmol L−1, a sensitivity of 1.397 × 10−7 μA (mmol L−1)−1 and a fast response time. The apparent Michaelis–Menten constant (kmapp) was 10 mmol L−1. In addition, the biosensor also exhibited good reproducibility, excellent stability and long life-time with no decrease in the activity of enzyme over a one week period and remained active in the films for periods longer than three weeks.