Abstract
The luminescence characteristics of six osmium carbonyl complexes with phenanthroline (phen) or bipyridine (bpy) and pyridine (py), 4-phenylpyridine (4-phpy), or triphenylphosphine (PPh3) complexes in the presence of polyanion heparin were studied in both ethanol and aqueous solutions. The influence of heparin on the luminescence of the complexes is heavily dependent on the type of ligands in the complexes and the solvent used. In the ethanol solutions, the heparin solution enhanced the luminescence of the five osmium complexes, with the strongest enhancement to the 4-phenylpyridine complexes; linear curves were obtained in the luminescence enhancement ratio (F/F 0) versus the heparin concentration range of 1–40 μg/mL. In aqueous solutions, heparin quenching of the complexes was more significant; a linear quenching curve was obtained with [Os(phen)2CO(PPh3)](PF6)2 in the lower concentration range of 1–12 μg/mL. The interaction of these complexes with heparin in the solutions is discussed. The complexes are shown to be successful in the fast and sensitive detection of heparin in commercial injectable samples.
Highlights
Heparina, a highly sulfated glycosaminoglycan, has the highest negative charge density of any known natural biological molecule [1]
The excitation and emission spectra of each complex in their ethanol solution (except for [Os(bpy)2CO(py)](PF6)2 which could not dissolve in ethanol) and their aqueous solution were first recorded at room temperature under ambient air
The aqueous solution of osmium complexes with a PPh3 or pyridine group exhibits a decrease in luminescence intensity at low added heparin concentrations; the luminescence increases at heparin concentration above 15 to 19 μg/mL
Summary
A highly sulfated glycosaminoglycan, has the highest negative charge density of any known natural biological molecule [1]. The sulfate groups are deprotonated and attract positively charged counterions (usually sodium) to form a heparin salt It is in this form that heparin is usually administered as an anticoagulant [5, 6]. This research focuses on studying the effect of the heparin polyanion on the photoluminescence of these polypyridyl osmium(II) complexes, for the purpose of finding potential luminescence markers for the detection of the optically nonactive polyanion heparin. For each of these chromophoric ligands, three analogous sets were compared using pyridine (py), triphenylphosphine (PPh3), or 4-phenylpyridine (4-phpy) as the sixth ligand These ligands showed a significant impact on the luminescence characteristics of the osmium complex in the absence as well as in the presence of polyanions. The results of the studies could lead to a new, potential effective detection method for heparin monitoring
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