One-step in situ solid-substrate-based whole blood immunoassay based on FRET between upconversion and gold nanoparticles

Despite their general clinicalapplications, current fluorescence-based immunoassays are confronted withserious challenges, e.g. the advance serum/ plasma separation and the tediouswashing process in current heterogeneous approaches, and aggregation ofparticles, low sensitivity and the narrow linear range in homogeneousapproaches. In this paper, these urgent problems were solved in a novelone-step in situ immunoassay of whole blood samples by combining the traditional fluorescenceresonance energy transfer (FRET) technology (between upconversion nanoparticles(UCNPs) and gold nanoparticles (GNPs)) and the solid-substrate basedimmunoassay technology. The low detection limits of goat IgG (gIgG) as 0.042 μg/mLin buffers, 0.51 μg/mL in 20-fold diluted whole bloodsamples and a wide linear range from 0.75 μg/mL to 60 μg/mLin blood samples were achieved. To the best of our knowledge, it is the firstone-step in situ solid-substrate-based immunoassay of whole blood samples with large lineardetection range. This development provides a promising platform for a rapid andsensitive immunoassay of various bio-molecules directly in whole blood withouttedious separation, washing steps and aggregation problems.