A DNA robotic switch with regulated autonomous display of cytotoxic ligand nanopatterns.

The clustering of death receptors (DRs) at the membrane leads to apoptosis. With the goal of treating tumours, multivalent molecular tools that initiate this mechanism have been developed. However, DRs are also ubiquitously expressed in healthy tissue. Here we present a stimuli-responsive robotic switch nanodevice that can autonomously and selectively turn on the display of cytotoxic ligand patterns in tumour microenvironments. We demonstrate a switchable DNA origami that normally hides six ligands but displays them as a hexagonal pattern 10 nm in diameter once under higher acidity. This can effectively cluster DRs and trigger apoptosis of human breast cancer cells at pH 6.5 while remaining inert at pH 7.4. When administered to mice bearing human breast cancer xenografts, this nanodevice decreased tumour growth by up to 70%. The data demonstrate the feasibility and opportunities for developing ligand pattern switches as a path for targeted treatment.

Wireframe DNA Origami for the Cellular Delivery of Platinum(II)-Based Drugs.

The DNA origami method has revolutionized the field of DNA nanotechnology since its introduction. These nanostructures, with their customizable shape and size, addressability, nontoxicity, and capacity to carry bioactive molecules, are promising vehicles for therapeutic delivery. Different approaches have been developed for manipulating and folding DNA origami, resulting in compact lattice-based and wireframe designs. Platinum-based complexes, such as cisplatin and phenanthriplatin, have gained attention for their potential in cancer and antiviral treatments. Phenanthriplatin, in particular, has shown significant antitumor properties by binding to DNA at a single site and inhibiting transcription. The present work aims to study wireframe DNA origami nanostructures as possible carriers for platinum compounds in cancer therapy, employing both cisplatin and phenanthriplatin as model compounds. This research explores the assembly, platinum loading capacity, stability, and modulation of cytotoxicity in cancer cell lines. The findings indicate that nanomolar quantities of the ball-like origami nanostructure, obtained in the presence of phenanthriplatin and therefore loaded with that specific drug, reduced cell viability in MCF-7 (cisplatin-resistant breast adenocarcinoma cell line) to 33%, while being ineffective on the other tested cancer cell lines. The overall results provide valuable insights into using wireframe DNA origami as a highly stable possible carrier of Pt species for very long time-release purposes.

Computer-Aided Design of A-Trail Routed Wireframe DNA Nanostructures with Square Lattice Edges.

In recent years, interest in wireframe DNA origami has increased, with different designs, software, and applications emerging at a fast pace. It is now possible to design a wide variety of shapes by starting with a 2D or 3D mesh and using different scaffold routing strategies. The design choices of the edges in wireframe structures can be important in some applications and have already been shown to influence the interactions between nanostructures and cells. In this work, we increase the alternatives for the design of A-trail routed wireframe DNA structures by using four-helix bundles (4HB). Our approach is based on the incorporation of additional helices to the edges of the wireframe structure to create a 4HB on a square lattice. We first developed the software for the design of these structures, followed by a demonstration of the successful design and folding of a library of structures, and then, finally, we investigated the higher mechanical rigidity of the reinforced structures. In addition, the routing of the scaffold allows us to easily incorporate these reinforced edges together with more flexible, single helix edges, thereby allowing the user to customize the desired stiffness of the structure. We demonstrated the successful folding of this type of hybrid structure and the different stiffnesses of the different parts of the nanostructures using a combination of computational and experimental techniques.

DNA Origami Penetration in Cell Spheroid Tissue Models is Enhanced by Wireframe Design.

As DNA origami applications in biomedicine are expanding, more knowledge is needed to assess these structures' interaction with biological systems. Here, uptake and penetration in cell and cell spheroid tissue models (CSTMs) are studied to elucidate whether differences in internal structure can be a factor in the efficacy of DNA-origami-based delivery. Two structures bearing largely similar features in terms of both geometry and molecular weight, but with different internal designs-being either compact, lattice-based origami or following an open, wireframe design-are designed. In CSTMs, wireframe rods are able to penetrate deeper than close-packed rods. Moreover, doxorubicin-loaded wireframe rods show a higher cytotoxicity in CSTMs. These results can be explained by differences in structural mechanics, local deformability, local material density, and accessibility to cell receptors between these two DNA origami design paradigms. In particular, it is suggested that the main reason for the difference in penetration dynamic arises from differences in interaction with scavenger receptors where lattice-based structures appear to be internalized to a higher degree than polygonal structures of the same size and shape. It is thus argued that the choice of structural design method constitutes a crucial parameter for the application of DNA origami in drug delivery.

Evolutionary Refinement of DNA Nanostructures Using Coarse-Grained Molecular Dynamics Simulations.

In the past decade, DNA nanostructures have made the leap from small assemblies of a handful of oligonucleotides to megadalton objects assembled from hundreds or thousands of component DNA strands. Most DNA designs today are either lattice based with simple and reliable design tools or lattice free with a larger shape space but more challenging design and lower rigidity. In parallel with the development of DNA nanostructures, software packages for the simulation of nucleic acids have seen rapid development allowing for the simulation of the dynamics of full DNA nanostructure assemblies. Here, we implement an unsupervised software based on the coarse-grained molecular dynamics package oxDNA to simulate DNA origami structures and evaluate their rigidity. From this, the software autonomously produces mutant structures by adding or removing base pairs or modifying the positions of internal supports. These mutant structures are iteratively generated and evaluated by simulation to create an in silico evolution toward more rigid DNA nanostructures.