Lanthanide-based luminescence represents an attractive alternative to conventional organic chromophores used for optical imaging applications. The unique electronic configuration of trivalent lanthanides results in narrow emission bands independent of the coordinative environment of the metal between 490-700 nm. Due to the Laporte-forbidden nature of <i>f-f</i> transitions, the excitation and energy transfer from aromatic chromophores (‘antennae’) at 250-350 nm is required to access the metal ion-based excited states. The need for this short-wave excitation renders luminescent lanthanides not suitable for in vivo applications due to the limited permeability of light through biological media below 500 nm. To overcome this impediment, we employ Cherenkov radiation energy transfer (CRET) to excite luminescent lanthanide complexes in situ. Cherenkov radiation (CR) is emission of short wavelength light generated by positron emitting radioisotopes commonly utilized in nuclear medicine. CR exhibits high relative intensity at short wavelengths required to efficiently excite lanthanide antennae. We have demonstrated the feasibility of this approach using inter- and intramolecular CRET systems and show that optical CRET imaging of a small library of terbium complexes allows us to screen relative quantum yield in a high throughput fashion. Herein, we will discuss efforts to utilize high-quantum yield Tb(III) complexes as biocompatible, analyte-responsive turn-on probes by triplet state energy modulation of the antenna and the development of biocompatible Eu(III) complexes to enable multiplex imaging.

Cherenkov radiation mediated excitation of lanthanide luminescence: Towards in vivo compatible, lanthanide-based optical probes

ACS Spring Meeting 2021

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