Green, yellow and red emitting CdTe QDs decreased the affinities of apigenin and luteolin for human serum albumin in vitro

Apigenin and luteolin were studied for the affinities for human serum albumin (HSA) in the presence and absence of three CdTe QDs with different sizes. The fluorescence intensities of HSA decreased remarkably with increasing concentration of QDs. Apigenin and luteolin resulted in obvious blue-shifts of the λem of HSA from 340 nm to 330 nm and 320 nm. However, the extents of blue-shifts induced by apigenin or luteolin in the presence of QDs were much smaller than that in the absence of QDs. The quenching process of apigenin for HSA was easily affected by the QDs size than that of luteolin. QDs decreased the quenching constant from 37.23% to 52.38% for apigenin. However, QDs decreased the quenching constant from 56.18% to 60.38% for luteolin. QDs decreased the affinity of apigenin or luteolin for HSA. G-QDs, Y-QDs, and R-QDs decreased the affinity of apigenin for HSA about 14.71%, 12.65% and 6.91%. The binding affinity of apigenin for HSA increased with increasing QDs size. However, the binding affinity of luteolin for HSA decreased with increasing QDs size. G-QDs, Y-QDs, and R-QDs decreased the affinities of luteolin for HSA about 19.48%, 22.47% and 28.18%.