Self-assembly of aptamer circular DNA nanostructures for controlled biocatalysis

Two kinds of circular DNA components are generated by the hybridization of short nucleic acids with the 3′ and 5′ ends of single-stranded DNA chains. The circular DNA components include, each, complementary domains for the anticocaine aptamer subunits, and sequencespecific domains for the auxiliary hybridization of programmed nucleic acid-functionalized proteins. The circular DNA components are selfassembled, in the presence of cocaine, into DNA nanowires (micrometer-long nanowires exhibiting heights of ca. 1.6-3.0 nm). Nucleic acids functionalized with glucose oxidase (GOx) and horseradish peroxidase (HRP) are hybridized with the circular DNA components to yield nanostructures consisting of HRP and GOx on the DNA scaffold. A biocatalytic cascade, where the GOx-catalyzed oxidization of glucose by O₂ yields H₂O ₂, and the resulting H₂O₂ oxidizes 2,2′-azino-bis[3-ethylbenzthiazoline-6-sulfonic acid] (ABTS^2-), in the presence of HRP, is activated by the system. The biocatalyzed oxidization of ABTS^2- on the DNA scaffold is 6-fold enhanced as compared to a nonbridged homogeneous system of the two biocatalysts. The enhanced biocatalytic cascade on the DNA scaffold is attributed to high local concentrations of the reactive components in the vicinity of biocatalysts.