Immobilization of barley oxalate oxidase onto gold–nanoparticle-porous CaCO3 microsphere hybrid for amperometric determination of oxalate in biological materials

ObjectivesThe use of Au nanoparticles (AuNPs)–CaCO3 porous microsphere hybrid as a matrix for enzyme immobilization to increase the performance of an amperometric biosensor.Design and methodsA method is described for construction of an amperometric oxalate biosensor by immobilizing a barley root oxalate oxidase (OxOx) onto AuNPs–CaCO3 porous microsphere hybrid encapsulated in silica sol and deposited on Au electrode.ResultsThe biosensor showed optimum response within 4 s at pH 5.0 and 30 °C, when polarized at + 0.4 V vs. Ag/agCl. The biosensor possesses high sensitivity and measures oxalate concentrations as low as 1.0 μmol/L. The working linear range was from 1.0 to 1000 μmol/L of oxalate. The biosensor measured urinary and plasma oxalate of normal persons and stone formers.ConclusionThe use of AuNPs–CaCO3 porous microsphere hybrid as a support for immobilization of OxOx has resulted into an improved amperometric oxalate biosensor.

► Constructed amperometric oxalate biosensor based on OxOx/AuNPs-CaCO3 microsphere.
► Biosensor showed optimum response within 4s at 0.4 V, pH 5.0 and 30 °C.
► Response was linear between 1.0-1000 μmol/L oxalic acid concentrations.
► Biosensor measured urinary & plasma oxalate of normal persons and stone formers.