Determination of Neutrophil Gelatinase-Associated Lipocalin Based on Immune Fluorescence Quenching of NaYF₄:Yb, Er Upconversion Nanophosphors

Two antibodies of neutrophil gelatinase-associated lipocalin (NGAL) were labeled by NaYF₄:Yb,Er upconversion nanophosphors (UCP) and CdTe quantum dots (QDs), respectively. The labelled-antibodies reacted with NGAL forming double anti-sandwich body by immune reaction and NGAL was determined without any washing and separation operation. It was found that fluorescence of UCP at 540 nm could significantly quenched. Linear relationship between values of fluorescence intensity ratio of UCP and mass concentration of NGAL was obtained in the range of 40-750 μg · L^-1, with detection limit (3s/k) of 23.3 μg·L^-1. On the base of blank sample, test for recovery was made by standard addition method. Values of recovery found were in the range of 94.6%-108%, with RSD's (n=6) in the range of 5.5%-9.1%.