Plant tissue-based chemiluminescence flow biosensor for oxalate

A novel plant tissue-based chemiluminescence (CL) biosensor for oxalate combined with flow injection analysis is proposed in this paper. The analytical reagents involved in the CL reaction, including luminol and cobalt(II), were both immobilized on an ion exchange resin column, while the biological material spinach tissue was packed in a mini-glass column. By the oxalate oxidase-catalyzed reaction in the plant tissue column, hydrogen peroxide was produced, which could react with luminol and cobalt(II) being released from the ion exchange column by hydrolysis to generate a CL signal. The CL emission intensity was linear with oxalate concentration in the range 0.6–100 µM and the detection limit was 0.2 µM. The biosensor was stable for 300 determinations and a complete analysis, including sampling and washing, could be performed in 2 min with a relative standard deviation of less than 5%.In recent years, traditional enzyme biosensors have been challenged by biosensors which use new biocatalytic materials, including animal and plant tissues1–3 and microorganisms.4–6 The catalytic function of these types of biosensors is due to the enzymes linked with metabolic pathways which exist either in the cytoplasmic membranes or directly inside the cells of these materials. Compared to biosensors with immobilized isolated and pure enzymes, such biosensors with immobilized tissues or whole cells show potential advantages of low cost, high stability, and a high level of enzyme activity. So far, most of them are bioselective membrane electrodes, in which the biocatalytic layer is usually retained physically at the detecting electrode surface with a support membrane and the analyte is sensed by diffusing through the test solution to the inner detector surface. However, these sensors often suffer from problems of long response time, low sensitivity and complex sensor assembly.Flow injection chemiluminescence (CL) analysis is becoming increasingly important in various fields for its high sensitivity, rapidity, simplicity and feasibility. Nowadays, CL flow sensing systems with immobilized reagents have received much attention and many applications have appeared in the literature.7–11 In these systems, analytes are detected by the CL reactions with the immobilized reagents directly or with the dissolved reagents which are released from the immobilized substrates by appropriate eluents. In this paper, a new type of biosensor, based on a plant tissue reactor, with flow injection CL detection for the determination of oxalate is proposed. It is prepared by using a spinach tissue column as the source of oxalate oxidase to catalyze the oxidation reaction of oxalate producing hydrogen peroxide, which is then detected by the CL reaction with luminol and cobalt(II) bleeding from an ion exchange column with immobilized reagents by hydrolysis.12