Aptamer Binding Assay for the E Antigen of Hepatitis B Using Modified Aptamers with G-Quadruplex Structures.

The e antigen of hepatitis B (HBeAg) is positively associated with an increased risk of developing liver cancer and cirrhosis in chronic hepatitis B (CHB) patients. Clinical monitoring of HBeAg provides guidance to the treatment of CHB and the assessment of disease progression. We describe here an affinity binding assay for HBeAg, which takes advantage of G-quadruplex aptamers for enhanced binding and stability. We demonstrate a strategy to improve the binding affinity of aptamers by modifying their sequences upon their G-quadruplex and secondary structures. On the basis of predicting a stable G-quadruplex and a secondary structure, we truncated 19 nucleotides (nt) from the primer regions of an 80-nt aptamer, and the resulting 61-nt aptamer enhanced binding affinity by 19 times (