Au\nNanoparticles-Trisbipyridine Ruthenium(II) Nanoaggregates\nas Signal-Amplifying SERS Tags for Immunoassay of cTnI

Acute myocardial\ninfarction (AMI) is one of the leading causes\nof human mortality worldwide. In the early stages of AMI, the patient’s\nelectrocardiogram (ECG) may not change, so the fast, sensitive, and\naccurate detection of the specific biomarker of cardiac troponin I\n(cTnI) is of great importance in the early diagnosis of AMI. In this\nwork, for the first time, electrostatic nanoaggregates of negatively\ncharged Au nanoparticles and positively charged trisbipyridine ruthenium(II)\nions (i.e., (−)AuNPs|[Ru(bpy)<sub>3</sub>]<sup>2+</sup> ENAs)\nas novel and signal-amplifying surface-enhanced Raman scattering (SERS)\ntags were synthesized in an easy and rapid (<3 min) way and applied\nin the highly sensitive, rapid detection of cTnI in human serum by\nbeing combined with an immunochromatographic test strip (ICTS). The\nsynthesized (−)AuNPs|[Ru(bpy)<sub>3</sub>]<sup>2+</sup> ENAs\nexhibited strong SERS activity due to the multiple Raman-active units\n(three bpy ligands) carried by each [Ru(bpy)<sub>3</sub>]<sup>2+</sup> complex ion and abundant hotspots in each SERS tag. The developed\n(−)AuNPs|[Ru(bpy)<sub>3</sub>]<sup>2+</sup> ENAs-based SERS-ICTS\nhas been validated to be applicable in detection of cTnI in human\nserum with excellent sensing performances, such as fast testing (5\nmin) and a low detection limit (60 pg/mL). It is envisioned that the\ndeveloped (−)AuNPs|[Ru(bpy)<sub>3</sub>]<sup>2+</sup> ENAs-based\nSERS-ICTS sensor may have promising applications in point of care\ntesting of various biomarkers in clinic. Additionally, this work may\ninspire the finding and the application of new types of Raman reporter\nmolecules based on high valent metal-multi ligand coordination compounds\nlike [Ru(bpy)<sub>3</sub>]<sup>2+</sup>.