Iridium(III) Luminescent Probe for Detection of the Malarial Protein Biomarker Histidine Rich Protein-II.
This work outlines the synthesis of a non-emissive, cyclometalated Ir(III) complex, Ir(ppy)2(H2O)2(+) (Ir1), which elicits a rapid, long-lived phosphorescent signal when coordinated to a histidine-containing protein immobilized on the surface of a magnetic particle. Synthesis of Ir1, in high yields,is complete O/N and involves splitting of the parent cyclometalated Ir(III) chloro-bridged dimer into two equivalents of the solvated complex. To confirm specificity, several amino acids were probed for coordination activity when added to the synthesized probe, and only histidine elicited a signal response. Using BNT-II, a branched peptide mimic of the malarial biomarker Histidine Rich Protein II (pfHRP-II), the iridium probe was validated as a tool for HRP-II detection. Quenching effects were noted in the BNT-II/Ir1 titration when compared to L-Histidine/Ir1, but these were attributed to steric hindrance and triplet state quenching. Biolayer interferometry was used to determine real-time kinetics of interaction of Ir1 with BNT-II. Once the system was optimized, the limit of detection of rcHRP-II using the probe was found to be 12.8 nM in solution. When this protein was immobilized on the surface of a 50 µm magnetic agarose particle, the limit of detection was 14.5 nM. The robust signal response of this inorganic probe, as well as its flexibility of use in solution or immobilized on a surface, can lend itself toward a variety of applications, from diagnostic use to imaging.
Department of Chemistry, Vanderbilt University; k.davis@vanderbilt.edu.
Keersten M
KM
Davis
Department of Chemistry, Vanderbilt University.
Anna L
AL
Bitting
Department of Chemistry, Vanderbilt University.
Christine F
CF
Markwalter
Department of Chemistry, Vanderbilt University.
Westley S
WS
Bauer
Department of Chemistry, Vanderbilt University.
David W
DW
Wright
D000953:Antigens, Protozoan / Q000032:analysis* / Q000378:metabolism; D015415:Biomarkers / Q000737:chemistry; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D007495:Iridium / Q000737:chemistry*; D008280:Magnetics; D016778:Malaria, Falciparum / Q000175:diagnosis / Q000469:parasitology*; D010963:Plasmodium falciparum / Q000737:chemistry* / Q000378:metabolism; D015800:Protozoan Proteins / Q000032:analysis* / Q000378:metabolism
D000953:Antigens, Protozoan; D015415:Biomarkers; C514457:HRP-2 antigen, Plasmodium falciparum; D015800:Protozoan Proteins; D007495:Iridium