A novel colorimetric sensing strategy for biomolecule assay has been developed, which integrates the signal amplification of the hybridization chain reaction (HCR) with the assembly of gold nanoparticles (AuNPs) through triplex formation. In the presence of targets, the HCR process can be triggered, the HCR products are specifically recognized by triplex-forming oligonucleotide (TFO) functionalized AuNPs, accompanying the aggregation of AuNPs and a dramatic absorbance change at 522 nm. In addition, the DNA hairpin probes can form rigid triplex structures with TFO-functionalized AuNPs in the absence of targets, resulting in a negligible background signal. By taking advantage of this new biosensor platform, a broad range of targets, involving nucleic acids, small molecules and proteins, have been successfully determined with high sensitivity and selectivity, which may hold great potential for practical application.

Iridium(III) complexes are emerging as a promising tool in the area of detection and therapy due to their prominent photophysical properties, including higher photostability, tunable phosphorescence emission, long-lasting phosphorescence, and high quantum yields. In recent years, much effort has been devoted to develop novel near-infrared (NIR) iridium(III) complexes to improve signal-to-noise ratio and enhance tissue penetration. In this review, we summarize different classes of organometallic NIR iridium(III) complexes for detection and therapy, including cyclometalated ligand-enabled NIR iridium(III) complexes and NIR-dye-conjugated iridium(III) complexes. Moreover, the prospects and challenges for organometallic NIR iridium(III) complexes for targeted detection and therapy are discussed.