Electrochemical differentiation of epitope-specific aptamers

DNA aptamers are promising immunoshielding agents that could protect oncolytic viruses (OVs) from neutralizing antibodies (nAbs) and increase the efficiency of cancer treatment. In the present Article, we introduce a novel technology for electrochemical differentiation of epitope-specific aptamers (eDEA) without selecting aptamers against individual antigenic determinants. For this purpose, we selected DNA aptamers that can bind noncovalently to an intact oncolytic virus, vaccinia virus (VACV), which can selectively replicate in and kill only tumor cells. The aptamers were integrated as a recognition element into a multifunctional electrochemical aptasensor. The developed aptasensor was used for the linear quantification of the virus in the range of 500-3000 virus particles with a detection limit of 330 virions. Also, the aptasensor was employed to compare the binding affinities of aptamers to VACV and to estimate the degree of protection of VACV using the anti-L1R neutralizing antibody in a displacement assay fashion. Three anti-VACV aptamer clones, vac2, vac4, and vac6, showed the best immunoprotection results and can be applied for enhanced delivery of VACV. Another two sequences, vac5 and vac46, exhibited high affinities to VACV without shielding it from nAb and can be further utilized in sandwich bioassays.