A target-responsive autonomous aptamer machine biosensor for enzyme-free and sensitive detection of protein biomarkers.

Highly sensitive and selective detection of protein disease markers is crucial for fundamental research and disease diagnosis. In this work, based on a new target-triggered autonomous aptamer machinery amplification approach, we developed a simple and sensitive sensing platform for the detection of a cancer biomarker, platelet-derived growth factor BB (PDGF-BB), in human sera. The target PDGF-BB binds the fluorescently quenched hairpin aptamer probes and causes structural and conformational changes in the aptamers to recover their fluorescence. The presence of partial duplex DNA fuel strands further leads to the recycling of the target proteins and the functioning of the aptamer machine autonomously to amplify the fluorescence emission significantly, thereby resulting in sensitive detection of PDGF-BB down to the low picomolar level. Besides, due to the high specificity of the aptamer, such a protein detection method shows high selectivity and can be employed to detect PDGF-BB in human sera. Featuring the advantages of being enzyme-free and nanomaterial-free for signal amplification, as well as homogeneous detection, the developed approach thus holds great potential for the construction of various aptasensors for the convenient and sensitive detection of different molecules.