Optical-based detections, amplification

Chapters 2-6 describe the use of several different types of polymer-based sensors, i.e. chemiluminescent, fluorescent and optical, to detect explosive materials. In the optical case a large array of coated beads is employed to reduce the signal-to-noise ratio, and provide greater amplification of weak signals from trace levels of vapours. 

Enzyme DNA hybridization assays with electrochemical detection can offer enhanced sensitivity and reduced instrumentation costs in comparison with their optical counterparts. Efforts to prevent non-specific binding of the codissolved enzyme and to avoid fouling problems by selecting conditions suitable to amplify the electrode response have been reported by Heller and co-workers [107]. A disposable electrochemical sensor based on an ion-exchange film-coated screen-printed electrode was described by Limoges and co-workers for an enzyme nucleic acid hybridization assay using alkaline phosphatase [108] or horseradish peroxidase [109]. In another methodology to improve sensitivity, a carbon paste electrode with an immobilized nucleotide on the electrode surface and methylene blue as hybridization indicator was coupled, by Mascini and co-workers [110], with PGR amplification of DNA extracted from human blood for the electrochemical detection of virus. 

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