Luminescent iridium(III)-peptide bioconjugates for bioanalytical and biomedical applications

Iridium(III) complexes are alternative bioimaging probes due to their tunable photophysical properties, but are limited by poor cell penetrability and high cytotoxicity. Recently, iridium(III)-peptide bioconjugates have received significant attention as bifunctional molecules in bioanalytical and biomedical fields. Conjugation to peptides endows iridium(III) complexes with specificity, potentially overcoming the side effects and drug resistance of metallodrugs, whilst enhancing cellular uptake due to the improved cell penetrability, low cytotoxicity and targetability of peptides. In this review, we briefly introduce the interactions between iridium(III) complexes and amino acids/peptides, including coordination to amino acids and detection and/or inhibition of peptides. We describe imaging applications of iridium(III)-peptide bioconjugates, involving direct coordination of functional peptides or ligand modification, for targeted imaging. Next, we present therapeutic and theranostic applications of iridium(iii)-peptide bioconjugates through targeting of DNA and proteins. Finally, we outline the challenges and future opportunities in the development of iridium(III)-peptide bioconjugates for precision medicine.