A Refractometric Uric Acid Biosensor Based on Immobilized Uricase and PVA+PEG Composite Hydrogels

A mechanically stable, high-sensitivity, high-selectivity, optical uric acid sensitive membrane (UASM) was prepared by immobilizing uricase in a mixture of SiO2 mesocellular foams (SiMCFs) and nanoparticles (SiNPs), then embedding it in a composite gel of polyvinyl alcohol (PVA) and polyethylene glycol (PEG). The UASM was spin-coated onto a gold-glass sheet to create a surface plasmon resonance (SPR) biosensor without electromagnetic and light-intensity disturbances. A series of prism-based SPR sensing experiments showed that, for a UASM consisting of SiMCFs and SiNPs at a mass ratio of 6:4, PVA and PEG at a mass ratio of 4:1, the resonance angle of the sensor decreased by about 2.610° and the average sensitivity was 2.175°/mM within a UA concentration range of 0 - 1.2 mM. Young's moduli of four dry UASM strips (670 - 1050 MPa) were obtained, demonstrating that UASMs have good biomechanical stability. Langmuir adsorption isotherm could explain the adsorption law of the UASMs for UA molecules in the concentration range of 0.2 - 1.2 mM.