Bioluminescence-based fibre-optic sensor with entrapped co-reactant: an approach for designing a self-contained biosensor

The possibility of designing a self-contained fibre-optic biosensor, i.e., that can be used without renewing reagents in the probe, was investigated. A probe specific for NADH involves immobilized bioluminescent enzymes which require the presence of two co-reactants a flavin substrate (FMN) and an aldehyde] to catalyse light emission. The FMN was non-covalently immobilized in a synthetic film and was internally released in the vicinity of the bound enzymes, at the sensing tip of the bioprobe. Release of FMN was achieved from the two different matrices tested: a collagen film and a poly(vinyl alcohol) (PVA) network. Continuous-flow assays of NADH could be performed over a linear dynamic range from 10 pmol to 1 nmol. A PVA matrix appears to be a promising support for designing a self-contained biosensor, as 30–35 reliable measurements (R.S.D.=5%) could be achieved without a decrease in the sensor signal, compared with only 10–15 assays with a collagen film.