Turn-on room temperature phosphorescence assay of heparin with tunable sensitivity and detection window based on target-induced self-assembly of polyethyleneimine capped Mn-doped ZnS quantum dots.

Room-temperature phosphorescence (RTP) turn-on assay of heparin with tunable sensitivity and detection window was demonstrated on the basis of the target induced self-assembly of polyethyleneimine capped Mn-doped ZnS (PEI-Mn-ZnS) QDs. The proposed method can cover the whole therapeutic dosing concentration range in postoperation and long-term therapy (0.2-1.2 U/mL, 1.7-10 μM) and cardiovascular surgery (2-8 U/mL, 17-67 μM) in 10 mM Tris-HCl (pH 7.4) buffer and can be applied for heparin determination in 100-fold diluted human serum samples. The tunable sensitivity and detection window was ascribed to the tunable particle size and ligand loading amount of PEI-Mn-ZnS QD arising from the chain length (or molecule weight) and feed amount of PEI. The chain length of PEI exhibited significant effect on the particle size and ligand loading amount and ultimately had important influence on both the sensitivity and detection window. The feeding amount of PEI, however, greatly affected the ligand loading amount alone and, in turn, affected only the detection window.