Luminescent lanthanides exhibit many properties of ideal optical imaging probes such as low limits of detection, minimal photobleaching and emit in the first or second biological window (550-800 nm and 1000-1350 nm). Organic chromophores absorbing in the 200-300 nm range, known as antennae, are necessary for efficient excitation of these lanthanide complexes due to the Laporte forbidden nature of f-f transitions. As these excitation wavelengths are not compatible with biological applications due to the strong absorbance of proteins and hemoglobin at wavelengths below 550 nm, we proposed that lanthanide-based complexes could be excited in situ using Cherenkov radiation. Cherenkov radiation has a maximum below 400 nm and is generated by charged particles emitted during the decay of radioisotopes in dielectric media. We have pioneered the in situ excitation of lanthanide complexes with Cherenkov radiation energy transfer (CRET), which eliminates the need for external high energy, short wavelength excitation of these complexes. Following our initial proof of concept, we demonstrated peptide-functionalized Tb(III) and Eu(III) complexes with CRET excitation could be used for simultaneous, multiplexed imaging and in vivo optical imaging. However, these complexes possessed limited quantum yields, and due to difficult functionalization chemistry, the variety of targeting vectors that could be appended was restricted. Here, we demonstrate our efforts towards second generation complexes with higher quantum yields and a versatile bioconjugation strategy that broadens the range of targets that can be explored.

Development of discrete europium chelates for targeted in vivo bioimaging

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.