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 sequence-specific domains for the auxiliary hybridization of programmed nucleic acid-functionalized proteins. The circular DNA components are self-assembled, 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 O-2 yields H2O2, 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.