Abstract A novel method for the detection of PDGF-BB has been developed using double-strand DNA-copper nanoparticles (dsDNA-CuNPs) as fluorescent markers. This assay relies on the premise that the aptamer-based probe undergoes a conformational change upon binding with target protein, and subsequently triggers polymerization reaction to generate dsDNA. Then, the resultant dsDNA can be used as a template for the formation of CuNPs with high fluorescence. Under the optimized conditions, the proposed assay allowed sensitive and selective detection of PDGF-BB with a detection limit of 4 nmol/L. This possibly makes it an attractive platform for the detection of a variety of biomolecules whose aptamers undergo similar conformational change.