Ultrasensitive free bilirubin detection in whole blood via counting quantum dots aggregates at single nanoparticle level

Here we report a versatile strategy for detecting bilirubin by harnessing the cationic polymer polyethylenimine induced aggregation of human serum albumin-modified quantum dots. These aggregates are easily discriminated from the individual QD by single molecule spectral imaging microscopy and correlated to the bilirubin concentration. The proposed method can selectively detect bilirubin with a detection limit as low as 0.6 nM. Remarkably, this method has been successfully applied to the trace detection of free bilirubin in human whole blood and serum samples with satisfactory results.