One-step competitive assay for detection of thrombin via disassembly of diblock oligonucleotide functionalised nanogold aggregates

In this study, we developed a simple, sensitive and cost effective sensing strategy for thrombin. Two polyadenine diblock oligonucleotides, one containing a thrombin aptamer (TA) and the other one a partial complementary sequence to thrombin aptamer (TAC), were designed to anchor on gold nanoparticle (AuNP) surface. The hybridisation of these two DNA strands promoted the assembly of some AuNPs together and formed AuNP aggregates. The introduction of thrombin competitively bound to its aptamer and triggered the disassembly of AuNP aggregates. The change in plasmon absorption of AuNPs generated significant signal without requiring labeling or preprocessing steps. This simple one-step competitive assay had been demonstrated for the detection of thrombin with a detection limit of 0.81 pM and a dynamic range from 10 pM to 10 nM. Furthermore, this method was successfully demonstrated to perform analysis in 10-fold diluted serum solutions without sophisticated instruments. This sensitive and convenient strategy is expected to provide a prospective alternative in clinical application in a fast and straight forward manner. • Diblock oligonucleotides were designed to functionalise gold nanoparticle and form nanogold aggregates. • Disassembly of nanogold aggregates was triggered by thrombin. • The proposed simple and low cost sensing strategy exhibited high sensitivity and specificity for detection of thrombin. • Solution of pH had influence on the transition of nanogold aggregates from disassembly to aggregation.