Determination of Monoenzyme- and Bienzyme-Stimulated Precipitation by a Cuvette-Based Surface Plasmon Resonance Instrument

Abstract

This paper describes the use of a cuvette-based surface plasmon resonance (SPR) instrument to measure biocatalyzed precipitation reactions. Enzyme-modified SPR sensor disk forms the base of a cuvette, in which the substrate solution is added with stirring. The determination of the substrate concentration relies on the measurement of SPR angle shift (ΔθSPR) induced by the deposition of the insoluble products without involving in any electrochemical reactions. As examples, horseradish peroxidase (HRP)-modified monoenzyme SPR sensor and HRP–glucose oxidase bienzyme-layered sensor are created to determine hydrogen peroxide and glucose via the catalyzed oxidation of 4-chloro-1-naphthol (4-CN). The deposition of the oxidized 4-CN-insoluble products leads to SPR angle shifts, which are linear to H2O2 and glucose in the concentration ranges of 0.067–7.24 × 10−5 and 0.7–8.3 × 10−4 mM, respectively. The SPR sensitivities are greater than those of nonelectrochemical quartz crystal microbalance (QCM) (the parallel results in this study) and compare favorable with those of electrochemical QCM and electrochemical SPR methods. This study opens the field for enhanced SPR measurements by using biocatalyzed precipitation as a signal amplification method.