Multifunctional DNA-Metal Nanohybrids Derived From DNA-MgPPi Microhybrids by Rolling Circle Amplification

Rolling circle amplification (RCA)-derived ultra-long DNA is highly attractive and versatile because of its diverse functionalities conferred by repeated DNA nanostructures. However, magnesium pyrophosphate (MgPPi) crystals, as byproducts of RCA, electrostatically interact with the DNA to form DNA microhybrids and hamper its broad bioapplications, as its large size is unfavorable for cellular uptake and decreases the density of functional DNA nanostructures. In this study, finely tuned synthesis strategies are developed to condense the microhybrids and replace non-functional MgPPi crystals with various functional metal nanostructures by reducing metal ions. By applying this condensation and reduction process to DNA templated by microhybrids, the particle size of organic-inorganic DNA-MgPPi microhybrids is gradually reconfigured into DNA-Au nanohybrids (≈15 fold difference). The effects of the ion concentration and metal ion type on the reduction process are systematically explored through morphological, structural, and compositional analyses. Upon formation of the nanohybrids, the preservation of Au nanostructures and polymerized DNA nanostructure-driven functions are evaluated. The nanohybrids demonstrated not only metal nanoparticle-based near-infrared absorbance but also DNA aptamer-mediated targeted intracellular delivery, indicating successful hybridization of functional organic-inorganic molecules. This synthesis method for RCA-originated ultra-long DNA-metal nanohybrids shows potential for a variety of biological applications.