An Optic-Fiber Sensor for Metronidazole Based on the Fluorescence Quenching of a Copolymer Bound Flavone Derivative

meter-thick optode membrane is a common problem in optic-fiber sensor design. Many methods have been published for slowing down the leaching process. Covalent binding of dye molecules on suitable matrices is one of the most efficient immobilization methods.1–7 Recently, we have described a new optic-fiber sensor for tetracycline antibiotics based on covalently immobilized anthracene.8 A distinct advantage of the sensor is that the lifetime is prolonged. Here, we further extend the previous work to a new methacrylate-acrylate-based copolymer binding a flavone derivative for constructing a metronidazole sensor. Flavones are secondary metabolites found in distinct families and genera in the plant kingdom. They show several biological properties, such as inhibition of protein tyrosine kinase, cytoxicity against cancer cells, antiviral, antibacterial and antioxidant activities. Recently, Wang et al. reported on the photochemical and photophysical properties of 4¢-N,N-dimethylaminoflavone derivatives with characteristic fluorescence emission.9,10 Among them, 3-hydroxyl-4¢-N,Ndimethylaminoflavone methacrylate (HMFM) was used as a new fluorescence probe to study the conformation of the water-soluble polymer. 11 Metronidazole, 1-(2-hydroxyethyl)-2-methyl-5-nitromidazole, has been widely used for the treatment of protozoa and anaerobic bacterial infections. The methods reported for measuring the concentration of metronidazole include spectrophotometry12, polarography13, voltammetry14 and chromatography.15 Two optic sensors for metronidazole based on pyrenebutyric acid physically trapped in PVC membranes were described by Chen and his co-workers.16,17 In this study, we developed a new optic-fiber sensor for metronidazole based on the fluorescence quenching of a covalently immobilized flavone derivative. The sensor shows good response properties, including reversibility, reproducibility, selectivity and a short response time. Also important is a prolonged lifetime, because of the covalent immobilization of dye.