Directing Multivalent Aptamer-Receptor Binding on the Cell Surface with Programmable Atom-Like Nanoparticles.

Multivalent interactions of biomolecules play pivotal roles in physiological and pathological settings. Whereas the directionality of the interactions is crucial, the state-of-the-art synthetic multivalent ligand-receptor systems generally lack programmable approaches for orthogonal directionality. Here, we report the design of programmable atom-like nanoparticles (aptPANs) to direct multivalent aptamer-receptor binding on the cell interface. The positions of the aptamer motifs can be prescribed on tetrahedral DNA frameworks to realize atom-like orthogonal valence and direction, enabling the construction of multivalent molecules with fixed aptamer copy numbers but different directionality. These directional-yet-flexible aptPAN molecules exhibit the adaptability to the receptor distribution on cell surfaces. We demonstrate the high-affinity tumor cell binding with a linear aptPAN oligomer (≈13-fold improved compared to free aptamers), which leads to ≈50 % suppression of cell growth.

Encoding quantized fluorescence states with fractal DNA frameworks.

Signal amplification in biological systems is achieved by cooperatively recruiting multiple copies of regulatory biomolecules. Nevertheless, the multiplexing capability of artificial fluorescent amplifiers is limited due to the size limit and lack of modularity. Here, we develop Cayley tree-like fractal DNA frameworks to topologically encode the fluorescence states for multiplexed detection of low-abundance targets. Taking advantage of the self-similar topology of Cayley tree, we use only 16 DNA strands to construct n-node (n = 53) structures of up to 5 megadalton. The high level of degeneracy allows encoding 36 colours with 7 nodes by site-specifically anchoring of distinct fluorophores onto a structure. The fractal topology minimises fluorescence crosstalk and allows quantitative decoding of quantized fluorescence states. We demonstrate a spectrum of rigid-yet-flexible super-multiplex structures for encoded fluorescence detection of single-molecule recognition events and multiplexed discrimination of living cells. Thus, the topological engineering approach enriches the toolbox for high-throughput cell imaging.

Preservation of DNA Nanostructure Carriers: Effects of Freeze-Thawing and Ionic Strength during Lyophilization and Storage.

DNA nanostructures have attracted wide interest in biomedical applications, especially as nanocarriers for drug delivery. Therefore, it is important to ensure the structural integrity of DNA nanostructures under ambient temperature storage. In this study, we examined lyophilization-based preservation of DNA nanostructures by investigating the structural integrity of different DNA nanostructures reconstituted from lyophilization. We demonstrated that lyophilization under appropriate ionic strength is amenable to the storage of DNA nanostructures. Compared with that stored in liquid solution, DNA nanostructure carriers reconstituted from lyophilization showed significantly better structural integrity after an accelerated aging test equivalent to 100-day room-temperature storage.