Xuyu Tan

The simultaneous intracellular delivery of multiple types of payloads, such as hydrophobic drugs and nucleic acids, typically requires complex carrier systems. Herein, we demonstrate a self-deliverable form of nucleic acid-drug nanostructure that is composed almost entirely of payload molecules. Upon light activation, the nanostructure sheds the nucleic acid shell, while the core, which consists of prodrug molecules, disintegrates via an irreversible self-immolative process, releasing free drug molecules and small molecule fragments. We demonstrate that the nanostructures exhibit enhanced stability against DNase I compared with free DNA, and that the model drug (camptothecin) released exhibits similar efficacy as free, unmodified drugs toward cancer cells.

Nucleic acids are generally regarded as the payload in gene therapy, often requiring a carrier for intracellular delivery. With the recent discovery that spherical nucleic acids enter cells rapidly, we demonstrate that nucleic acids also have the potential to act as a delivery vehicle. Herein, we report an amphiphilic DNA-paclitaxel conjugate, which forms stable micellar nanoparticles in solution. The nucleic acid component acts as both a therapeutic payload for intracellular gene regulation and the delivery vehicle for the drug component. A bioreductively activated, self-immolative disulfide linker is used to tether the drug, allowing free drug to be released upon cell uptake. We found that the DNA-paclitaxel nanostructures enter cells ∼100 times faster than free DNA, exhibit increased stability against nuclease, and show nearly identical cytotoxicity as free drug. These nanostructures allow one to access a gene target and a drug target using only the payloads themselves, bypassing the need for a cocarrier system.

Abstract Coronavirus disease 19 (COVID-19) is an emerging global health crisis. With over 7 million confirmed cases to date, this pandemic continues to expand, spurring research to discover vaccines and therapies. SARS-CoV-2 is the novel coronavirus responsible for this disease. It initiates entry into human cells by binding to angiotensin-converting enzyme 2 (ACE2) via the receptor binding domain (RBD) of its spike protein (S). Disrupting the SARS-CoV-2-RBD binding to ACE2 with designer drugs has the potential to inhibit the virus from entering human cells, presenting a new modality for therapeutic intervention. Peptide-based binders are an attractive solution to inhibit the RBD-ACE2 interaction by adequately covering the extended protein contact interface. Using molecular dynamics simulations based on the recently solved cryo-EM structure of ACE2 in complex with SARS-CoV-2-RBD, we observed that the ACE2 peptidase domain (PD) α1 helix is important for binding SARS-CoV-2-RBD. Using automated fast-flow peptide synthesis, we chemically synthesized a 23-mer peptide fragment of the ACE2 PD α1 helix (SBP1) composed entirely of proteinogenic amino acids. Chemical synthesis of SBP1 was complete in 1.5 hours, and after work up and isolation >20 milligrams of pure material was obtained. Bio-layer interferometry (BLI) revealed that SBP1 associates with micromolar affinity to insect-derived SARS-CoV-2-RBD protein obtained from Sino Biological. Association of SBP1 was not observed to an appreciable extent to HEK cell-expressed SARS-CoV-2-RBD proteins and insect-derived variants acquired from other vendors. Moreover, competitive BLI assays showed SBP1 does not outcompete ACE2 binding to Sino Biological insect-derived SARS-CoV-2-RBD. Further investigations are ongoing to gain insight into the molecular and structural determinants of the variable binding behavior to different SARS-CoV-2-RBD protein variants.

Significance Spherical nucleic acids (SNAs) made thus far are inherently polydisperse due to variations in surface nucleic acid density, particle size, or both. In this article, we describe the synthesis and characterization of two types of molecular SNAs with precise numbers of surface DNA strands using T 8 polyoctahedral silsesquioxane and buckminsterfullerene C 60 scaffolds. The surface DNA densities for these molecular structures fall inside the range of typical SNAs, which allows them to exhibit SNA-related properties, including enhanced cellular uptake and the ability to function as a gene regulation agent. With a route to molecularly pure SNAs opened, it becomes possible to use them to unveil the molecular details of SNA interactions with complementary ligands and living systems.