Dioxetane-doped silica nanoparticles as ultrasensitive reagentless thermochemiluminescent labels for bioanalytics.

Thermochemiluminescence (TCL; the light emission originating by the thermally triggered decomposition of a molecule) was proposed in the late 1980s as a detection technique for immunoassays. However, after little pioneering work, this technique was abandoned because of the high temperatures required and the poor detectability in comparison to other labels. Here we describe for the first time a thermochemiluminescent acridine-based 1,2-dioxetane with a remarkably low (i.e., below 100 °C) emission-triggering temperature, which made it possible to obtain light emission even in an aqueous environment, as well as amino-functionalized silica nanoparticles loaded with this compound and the fluorescent energy acceptor dipyridamole. Thanks to the signal amplification due to the large number of 1,2-dioxetane molecules in each nanoparticle (about 10(4)) and the increased emission efficiency due to energy transfer to the fluorescent acceptor, the doped nanoparticles could be revealed with a detectability close to that of chemiluminescent enzyme labels (the limit of detection of doped nanoparticles by TCL imaging was 1 × 10(-16) mol mm(-2), thus approaching the value of 5 × 10(-17) mol mm(-2) obtained for the enzyme label horseradish peroxidase with chemiluminescence detection). They could thus be used as highly detectable labels in the development of sensitive TCL-based immunoassays and nucleic acid hybridization assays, in which the detection step does not require any additional chemical reagent. We believe that these doped silica nanoparticles could pave the way for the revival of TCL detection in bioanalytics, taking advantage of the reagentless detection and the high signal/noise ratio in comparison with conventional luminescence detection techniques.