Abstract
A thorough selectivity study of DNA hybridization employing an electrochemical enzymatic genosensor is discussed here. After immobilizing on a gold film a 30-mer 3'-thiolated DNA strand, hybridization with a biotinylated complementary one takes place. Then, alkaline phosphatase is incorporated to the duplex through the interaction streptavidin-biotin. Enzymatic generation of indigo blue from 3-indoxyl phosphate and subsequent electrochemical detection was made. The influence of hybridization conditions was studied in order to better discern between fully complementary and mismatched strands. Detection of 3, 2 and 1 mismatch was possible. The type and location of the single-base mismatch, as well as the influence of the length of the strands was studied too. Mutations that suppose displacement of the reading frame were also considered. The effect of the concentration on the selectivity was tested, resulting a highly selective genosensor with an adequate sensitivity and stability.