Terminal protection-mediated autocatalytic cascade amplification coupled with graphene oxide fluorescence switch for...

Folate receptor (FR) is over-expressed in most human tumors and has been regarded as biomarker and therapeutic target. Specific and sensitive detection of FR is essential for tumor treatment and drug development. Here, a specific, sensitive and rapid FR detection strategy was proposed based on terminal protection-mediated autocatalytic cascade amplification coupled with graphene oxide fluorescence switch. Firstly, the specific binding of FR to the folate terminally-labeled on a primary trigger DNA (PT-DNA) could protect the PT-DNA from exonuclease I degradation, converting FR detection to PT-DNA detection. Subsequently, the PT-DNA hybridized with the overhang of 3'-FAM labeled hairpin probe to initiate exonuclease III-assisted hydrolysis, accompanied with the PT-DNA recycling and autonomous generation of secondary trigger DNA and fluorophore. The secondary trigger DNA could as a PT-DNA analogue for the successive hybridization and hydrolysis process, liberating numerous fluorophores within 40min. Finally, The fluorophores kept away from the surface of graphene oxide, achieving significantly amplified fluorescence signal. The specific interaction between FR and folate guaranteed the FR could be distinguished from other proteins with high selectivity. The high fluorescence quenching efficiency of graphene oxide guaranteed a low background. Due to the highly autocatalytic cascade amplification efficiency and low background, sensitive detection of FR had been achieved with the detection limit of 0.44pM. The recoveries from 92% to 107% were achieved by detecting FR in spiked human serum. These results indicate this strategy holds a great potential for reliable quantification of FR in clinical diagnosis and disease treatment.