Universal fluorometric aptasensor platform based on water-soluble conjugated polymers/graphene oxide

We designed a universal and sensitive fluorometric aptasensor that uses a fluorescence resonance energy transfer (FRET) mechanism. In the aptasensor, water-soluble conjugated poly(9,9-bis(6'-N,N,N-trimethylammonium)hexyl)fluorine phenylene (PFP) is used as the energy donor and a carboxyfluorescein (FAM)-labeled aptamer is used as the energy acceptor. Graphene oxide (GO) used as a quencher can specifically adsorb the aptamer, leading to quenching of the FAM fluorescence. In the presence of targets, the aptamer can change its conformation to prevent adsorption by GO. Strong FRET was thus obtained owing to the electrostatic interactions between PFP and the aptamer. In contrast, in the absence of targets, the FRET was weak because of GO specifically adsorbing the aptamer and quenching the fluorescence. Bisphenol A (a pollutant molecule) and dopamine (a biomolecule) were used as models to successfully validate the feasibility, universality, and high selectivity and sensitivity of this aptasensor. This method can detect BPA at environmentally relevant concentrations (less than 1 ng/mL) with a limit of detection of 0.005 ng/mL. A low limit of detection (1.0 nmol/L) was also obtained for dopamine. In addition, this aptasensor is applicable in real samples and in diluted human plasma and human serum. Good recovery rates from 95% to 105% and from 95% to 107% were obtained for bisphenol A and dopamine, respectively. Furthermore, adenosine detection was successfully achieved by the same mechanism, proving the universality. It is expected that the aptasensor could be applied in detecting other contaminants, biomolecules, and heavy metal ions by a change in only the aptamer sequence. Graphical abstract A universal and sensitive fluorometric aptasensor was developed for the detection of small molecules that uses a fluorescence resonance energy transfer (FRET) mechanism. GO graphene oxide. PFP poly(9,9-bis(6'-N,N,N-trimethylammonium)hexyl)fluorine phenylene.