Active Nuclear Import of Mammalian Cell-Expressible DNA Origami.

DNA origami enables the creation of complex 3D shapes from genetic material. Future uses could include the delivery of genetic instructions to cells, but nuclear import remains a major barrier to gene delivery due to the impermeability of the nuclear membrane. Here we realize active nuclear import of DNA origami objects in dividing and chemically arrested mammalian cells. We developed a custom DNA origami single-strand scaffold featuring a mammalian-cell expressible reporter gene (mCherry) and multiple Simian virus 40 (SV40) derived DNA nuclear targeting sequences (DTS). Inclusion of the DTS within DNA origami rescued gene expression in arrested cells, indicating that active transport into the nucleus occurs. Our work successfully adapts mechanisms known from viruses to promote the cellular expression of genetic instructions encoded within DNA origami objects.

Gene-encoding DNA origami for mammalian cell expression.

DNA origami may enable more versatile gene delivery applications through its ability to create custom nanoscale objects with specific targeting, cell-invading, and intracellular effector functionalities. Toward this goal here we describe the expression of genes folded in DNA origami objects delivered to mammalian cells. Genes readily express from custom-sequence single-strand scaffolds folded within DNA origami objects, provided that the objects can denature in the cell. We demonstrate enhanced gene expression efficiency by including and tuning multiple functional sequences and structures, including virus-inspired inverted-terminal repeat-like (ITR) hairpin motifs upstream or flanking the expression cassette. We describe gene-encoding DNA origami bricks that assemble into multimeric objects to enable stoichiometrically controlled co-delivery and expression of multiple genes in the same cells. Our work provides a framework for exploiting DNA origami for gene delivery applications.

Broad-Spectrum Virus Trapping with Heparan Sulfate-Modified DNA Origami Shells.

Effective broadband antiviral platforms that can act on existing viruses and viruses yet to emerge are not available, creating a need to explore treatment strategies beyond the trodden paths. Here, we report virus-encapsulating DNA origami shells that achieve broadband virus trapping properties by exploiting avidity and a widespread background affinity of viruses to heparan sulfate proteoglycans (HSPG). With a calibrated density of heparin and heparan sulfate (HS) derivatives crafted to the interior of DNA origami shells, we could encapsulate adeno, adeno-associated, chikungunya, dengue, human papilloma, noro, polio, rubella, and SARS-CoV-2 viruses or virus-like particles, in one and the same HS-functionalized shell system. Additional virus-type-specific binders were not needed for the trapping. Depending on the relative dimensions of shell to virus particles, multiple virus particles may be trapped per shell, and multiple shells can cover the surface of clusters of virus particles. The steric occlusion provided by the heparan sulfate-coated DNA origami shells can prevent viruses from further interactions with receptors, possibly including those found on cell surfaces.

Programmable icosahedral shell system for virus trapping.

Broad-spectrum antiviral platforms that can decrease or inhibit viral infection would alleviate many threats to global public health. Nonetheless, effective technologies of this kind are still not available. Here, we describe a programmable icosahedral canvas for the self-assembly of icosahedral shells that have viral trapping and antiviral properties. Programmable triangular building blocks constructed from DNA assemble with high yield into various shell objects with user-defined geometries and apertures. We have created shells with molecular masses ranging from 43 to 925 MDa (8 to 180 subunits) and with internal cavity diameters of up to 280 nm. The shell interior can be functionalized with virus-specific moieties in a modular fashion. We demonstrate this virus-trapping concept by engulfing hepatitis B virus core particles and adeno-associated viruses. We demonstrate the inhibition of hepatitis B virus core interactions with surfaces in vitro and the neutralization of infectious adeno-associated viruses exposed to human cells.