4-Aminophenol was selected as a model hapten for thermal-lens detection in a heterogeneous indirect immunoassay for small organic compounds. The assay is based on the competition of the free hapten and 4-aminophenol labeled with tetramethyl rhodamine isothiocyanate (TRITC) for rabbit anti-4-aminophenol antibodies (4-AP-GA-BSA) immobilized on a transparent poly(ethylene terephthalate) plate. The amount of the colored analyte was directly measured by thermal lensing at the plate surface. The developed method is specific for 4-aminophenol. The limit of detection is 2 × 10<sup>−7</sup> M, which corresponds to the absolute amount of 3 × 10<sup>−11</sup> mol of 4-aminophenol. The sensitivities of the developed thermal-lens and fluorescence-based measurements of the immunoassay under the same conditions are in good agreement with the expected and discussed theoretical sensitivities of photothermal and fluorescence measurements.
Vol. 5, Iss. 12 Virtual Journal for Biomedical Optics
Dmitry A. Nedosekin, Anton V. Brusnichkin, Andrei Y. Luk'yanov, Sergei A. Eremin, and Mikhail A. Proskurnin, "Heterogeneous Thermal-Lens Immunoassay for Small Organic Compounds: Determination of 4-Aminophenol," Appl. Spectrosc. 64, 942-948 (2010)