DNA Dendrimer-Streptavidin Nanocomplex: an Efficient Signal Amplifier for Construction of Biosensing Platforms.

We develop a DNA dendrimer-streptavidin (SA) nanocomplex as a novel signal amplifier to create biosensing platforms for disease-related species. The DNA dendrimer-SA nanocomplex is fabricated by cross-linking the nonlinear hybridization chain reaction based DNA dendrimer with the SA-coupled linker DNA and possesses multiple sticky ends, a high molecular weight, and a hyperbranched nanostructure with large numbers of DNA duplexes. Taking advantage of the DNA dendrimer-SA nanocomplex and a label-free quartz crystal microbalance (QCM) technology, we first construct a mass-sensitive QCM biosensing platform for nucleic acids, which displays high selectivity and sensitivity, with a detection limit of 0.062 nM KRAS gene fragment. Then we present a fluorescent sensing strategy toward HeLa cells by functionalizing the DNA dendrimer-SA nanocomplex using the sgc8 aptamer and the SYBR Green I intercalating dye. The spiked recoveries of targets in physiological media are greater than 90%, demonstrating potential application of created biosensing platforms in clinical diagnosis. This work expands the rule set of designing DNA nanomaterials for development of biosensing strategies, and provides universal platforms for detecting disease-related species through simply altering the related capture and reporter DNA sequences.