title: Bulk fluorescence light blockers to improve homogeneous detection in capillary-waveguide fluoroimmunosensors.
abstract: A simple approach that employs black drawing ink (BDI) as bulk fluorescence light blocker and improves considerably the homogeneous signal detection in capillary-waveguide fluoroimmunosensors is presented. The concept was proved using a capillary sensor configuration. Fluorescent molecules in the capillary were excited by a laser beam vertically to its axis and the emitted photons that were trapped and waveguided through the capillary wall were then collected. Two competitive fluoroimmunoassays, for rabbit gamma-globulins in buffer and thyroxine in human serum, respectively, were set-up to evaluate this approach. It was found that the presence of ink improved the specific to bulk fluorescence signal ratio by approximately 60-times without affecting the analyte-antibody binding reaction thus, facilitating homogeneous detection. The analytical characteristics of the two assays developed with the sensor operating in homogeneous detection mode were similar to those determined following the heterogeneous detection mode (i.e. after removal/washing of the immunoreaction mixture).
authors.affiliation: Institute of Radioisotopes & Radiodiagnostic Products, Immunoassay/Immunosensors Laboratory, NCSR Demokritos, Aghia Paraskevi, GR-15310, Greece.
authors.forename: Christos
authors.initials: C
authors.lastname: Mastichiadis
authors.forename: Panagiota S
authors.initials: PS
authors.lastname: Petrou
authors.forename: Ion
authors.initials: I
authors.lastname: Christofidis
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Misiakos
authors.forename: Sotirios E
authors.initials: SE
authors.lastname: Kakabakos
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D002197:Capillary Action; D004867:Equipment Design; D019544:Equipment Failure Analysis; D015200:Fluoroimmunoassay / Q000295:instrumentation*; D007281:Ink; D055096:Optical Devices; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity