Ultrasensitive detection of trace protein by Western blot based on POLY-quantum dot probes

In this study, we describe an ultrasensitive quantum dots (QDs)-based Western blot. With the high affinity of avidin-functionalized POLY-QDs and simplification of the detection process, this enabled the quantitative analysis of protein by Western blotting. To prepare the POLY-QDs, CdTe quantum dots were first coated with biotinylated denatured bovine serum albumin and then, via the effect of the biotin-avidin system, the biotinylated denatured bovine serum albumin-coated QDs, which had strong fluorescence, were linked together. With this series of modifications, the fluorescence intensity of CdTe QDs was significantly increased. Using the POLY-QDs as labels, the signal of Western blotting was more sensitive in tracing the protein than traditional dyeing. In the present study, trace protein A was applied to POLY-QDs-based Western blotting as a model. The linearity of this method was from 30 pg to 1.5 ng, and the sensitivity was up to low pictogram values. The final fluorescence signal on the polyvinylidenedifluoride (PVDF) membrane was retained for at least 40 min. The results of this study indicate that the POLY-QDs-based Western blot is an excellent quantitative analytical method for trace protein analysis.