Characterizing Fluorescence Lifetime of Nad(p)h in Human Leukemic Myeloid Cells and Mononuclear Cells

Abstract

The aim of this ex vivo study was to explore the potential of using the°uorescence lifetime of intracellular reduced nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) as a label-free indicator to characterize the di®erences between human leukemic myeloid cells and normal mononuclear cells (MNC). The steady-state and time-resolved auto°uorescence of two human leukemic myeloid cell lines (K562, HL60) and MNC were measured by a spectro°uorimeter. According to excitation-emission matrix (EEM) analysis, the optimal emission of NAD(P)H in these cells suspensions occurred at 445 nm. Furthermore, the°uorescence lifetimes of NAD(P)H in leukemic myeloid cells and MNC were determined by¯tting the time-resolved auto°uorescence data. The mean°uorescence lifetimes of NAD(P)H in K562, HL60, and MNC cells were 5:57AE 1:19, 4:45 AE 0:71, and 7:31 AE 0:60 ns, respectively. There was a signi¯cant di®erence in the mean lifetime of NAD(P)H between leukemic myeloid cells and MNC (p < 0:05). The di®erence was essentially caused by the change in relative concentration of free and protein-bound NAD(P)H. This study suggests that the mean°uorescence lifetime of NAD(P)H might be a potential labelfree indicator for di®erentiating leukemic myeloid cells from MNC.