Preparation and fluorescence properties of fluorophore-labeled avidin-biotin system immobilized on Fe3O4 nanoparticles through functional indolequinone linker.

ABSTRACT

We prepared and characterized a new class of fluorophore-labeled magnetic nanoparticles (MNPs) possessing a hypoxia-responsive unit to construct a hypoxia-selective emission system. The indolequinone derivative as a hypoxia-response unit bearing biotin was synthesized and immobilized on Fe(3)O(4) MNP. Subsequent complexation of this functionalized MNP with fluorescein-labeled avidin formed fluorophore-labeled nanoparticles (AF-QB@MNP). The fluorescence intensity of AF-QB@MNP was suppressed because of the adjacent quenching function of the indolequinone moiety and MNP. Upon hypoxic treatment by NADPHcytochrome P450 reductase, AF-QB@MNP was activated to liberate a fluorescence unit, leading to the significant enhancement of fluorescence emission, while a smaller enhancement in fluorescence emission occurred upon aerobic treatment. The AF-QB@MNP has a indispensable properties as a fluorescent probe for imaging of disease relevant hypoxic microenvironments.