Highly amplified detection of visceral adipose tissue-derived serpin (vaspin) using a cognate aptamer duo.

A cognate aptamer duo for visceral adipose tissue-derived serpin (vaspin) which distinctively bind to two different sites on vaspin with high affinity and specificity were successfully developed by using graphene oxide-based systematic evolution of ligands by exponential enrichment (GO-SELEX), which offers immobilization-free screening of aptamers. The specific and simultaneous bindings of this aptamer duo (V1 and V49 aptamers) to the different sites of vaspin were confirmed by circular dichroism (CD) analysis and both sandwich-type surface plasmon resonance (SPR) and quantum dot labelled fluorescence imaging analysis (V1 aptamer serves as primary capturing aptamer and V49 aptamer as secondary signalling aptamer or vice versa). With this vaspin cognate aptamer duo on SPR platform, the detection of the target vaspin were improved to the limit of detection down to 3.5 ng/ml in buffer and 4.7 ng/ml in human serum samples. This cognate aptamer duo based biosensor could be utilized in the early diagnosis of type-2 diabetes.