Combining a loop-stem aptamer sequence with methylene blue: a simple assay for thrombin detection by resonance light scattering technique

An ingenious sensing strategy for detecting thrombin in human serum has been developed on the basis of a hairpin DNA sequence and resonance light scattering (RLS) technique. A thrombin aptamer sequence was embedded inside the hairpin DNA strand (H-eTBA), which was designed to be the loop-stem structure. Moreover, methylene blue (MB) was utilized as the RLS signal indicator according to its different affinity to single or double stranded DNA. Upon the addition of thrombin, the thrombin aptamer inside H-eTBA interacted specifically with thrombin. Thus the conformation of H-eTBA would change. After the introduction of the DNA strand (CTBA), which was complementary to H-eTBA, the amount of double stranded DNA would decrease as a consequence. Later when MB solution was added, the RLS signal would present various response values based on different amounts of thrombin. The determination of thrombin in human serum could be obtained with a detection limit of 0.32 nM and this specific sensor could be applied to detect thrombin practically. Furthermore, this aptasensor showed quite good selectivity and simplicity toward thrombin. Finally, the proposed sensing method showed its superiority with selectivity and practicability, which could be used as a simple platform for thrombin detection.