Graphene oxide enhanced specificity at aptamer and its application to multiplexed enzymatic activity sensing

We explore the effect of sufficient GO on the property of a dye labeled adenosine 5′-triphosphate (ATP) aptamer (P) which shows similar affinity and specificity for ATP and its analogues including adenosine 5′-diphosphate (ADP), adenosine 5′-monophosphate (AMP), and adenosine (AD). It is found that ATP and its analogues give rise to fluorescence recovery of GO-quenched P to a different extent (in the order of ATP > AD > ADP > AMP), and the difference becomes larger when increasing the concentration of GO in a certain range, implying an improvement of specificity of the ATP aptamer. Based on this finding, a fluorescence turn-on assay for alkaline phosphatase (ALP) and creatine kinase (CK) is proposed, by using AMP and ADP as the substrate, respectively. Specifically, the GO-quenched P system containing substrate shows low fluorescence intensity. In the presence of target enzyme, the substrate is converted into either AD or ATP which have higher affinity with P, resulting in stronger fluorescence of the mixture of P and GO. The entire assay is sensitive and selective. More importantly, the ability of GO with suitable concentration to improve the specificity of aptamers not only offers an exciting new way to detect protease, but also is valuable for developing the application of GO and aptamers in the biosensing field and is expected to be used in aptamer screening systems, to improve the specificity of screened aptamers.