Rapid de novo discovery of peptidomimetic affinity reagents for human angiotensin converting enzyme 2.

Rapid discovery and development of serum-stable, selective, and high affinity peptide-based binders to protein targets are challenging. Angiotensin converting enzyme 2 (ACE2) has recently been identified as a cardiovascular disease biomarker and the primary receptor utilized by the severe acute respiratory syndrome coronavirus 2. In this study, we report the discovery of high affinity peptidomimetic binders to ACE2 via affinity selection-mass spectrometry (AS-MS).

Exploring the Structural Diversity of DNA Bottlebrush Polymers Using an Oligonucleotide Macromonomer Approach.

Herein, we demonstrate that macromonomers consisting of organics-soluble, chemically protected oligonucleotides (protDNA) and poly(ethylene glycol) (PEG) chains can be converted into bottlebrush polymers of distinct architectures via ring-opening metathesis polymerization (ROMP). Using a custom norbornene-containing phosphoramidite, two types of macromonomers were obtained: a linear norbornene-protDNA-PEG structure and a Y-shaped structure where the polymerizable norbornene group is situated at the junction where protDNA and PEG meet. With this strategy, the PEG chains can be placed either near the backbone of the bottlebrush or on its periphery, and in principle anywhere between these two extremes by adjusting the norbornene location, which makes this strategy attractive for constructing architecturally sophisticated oligonucleotide-containing copolymers.

Bottlebrush Polymer-Conjugated Melittin Exhibits Enhanced Antitumor Activity and Better Safety Profile.

Despite potency against a variety of cancers in preclinical systems, melittin (MEL), a major peptide in bee venom, exhibits non-specific toxicity, severe hemolytic activity, and poor pharmacological properties. Therefore, its advancement in the clinical translation system has been limited to early-stage trials. Herein, we report a biohybrid involving a bottlebrush-architectured poly(ethylene glycol) (PEG) and MEL.

Spherical Nucleic Acids for Topical Treatment of Hyperpigmentation.

Oligonucleotide-based materials such as spherical nucleic acid (SNA) have been reported to exhibit improved penetration through the epidermis and the dermis of the skin upon topical application. Herein, we report a self-assembled, skin-depigmenting SNA structure, which is based upon a bifunctional oligonucleotide amphiphile containing an antisense oligonucleotide and a tyrosinase inhibitor prodrug. The two components work synergistically to increase oligonucleotide cellular uptake, enhance drug solubility, and promote skin penetration.

Self-Assembled DNA-PEG Bottlebrushes Enhance Antisense Activity and Pharmacokinetics of Oligonucleotides.

Herein, we report a novel strategy to enhance the antisense activity and the pharmacokinetics of therapeutic oligonucleotides. Through the DNA hybridization chain reaction, DNA hairpins modified with poly(ethylene glycol) (PEG) form a bottlebrush architecture consisting of a double-stranded DNA backbone, PEG side chains, and antisense overhangs. The assembled structure exhibits high PEG density on the surface, which suppresses unwanted interactions between the DNA and proteins (e.

Self-immolative polymers in biomedicine.

Self-immolative polymers (SIPs) have been under development for over a decade, and efforts for their application followed shortly after their inception. One main area of application of SIPs is biomedicine, where they are used to construct devices and biosensors, develop new biotechnology abilities, or directly interface with the living system. Where traditional polymers are stable at room temperature, SIPs undergo rapid degradation when a labile capping group is removed, allowing SIPs to offer a highly unusual degradation profile compared with traditional polymers.

Nucleic acid-based drug delivery strategies.

Nucleic acids have not been widely considered as an optimal material for drug delivery. Indeed, unmodified nucleic acids are enzymatically unstable, too hydrophilic for cell uptake and payload encapsulation, and may cause unintended biological responses such as immune system activation and prolongation of the blood coagulation pathway. Recently, however, three major areas of development surrounding nucleic acids have made it worthwhile to reconsider their role for drug delivery.

Expanding the materials space of DNA via organic-phase ring-opening metathesis polymerization.

Herein, we develop a facile route to bring DNA to the organic phase, which greatly expands the types of structures accessible using DNA macromonomers. Phosphotriester- and exocyclic amine-protected DNA was synthesized and further modified with a norbornene moiety, which enables homopolymerization via ring-opening metathesis to produce brush-type DNA graft polymers in high yields. Subsequent deprotection cleanly reveals the natural phosphodiester DNA.

Bottlebrush-architectured poly(ethylene glycol) as an efficient vector for RNA interference in vivo.

Nonhepatic delivery of small interfering RNAs (siRNAs) remains a challenge for development of RNA interference-based therapeutics. We report a noncationic vector wherein linear poly(ethylene glycol) (PEG), a polymer generally considered as inert and safe biologically but ineffective as a vector, is transformed into a bottlebrush architecture. This topology provides covalently embedded siRNA with augmented nuclease stability and cellular uptake.

Modulating the Depolymerization of Self-Immolative Brush Polymers with Poly(benzyl ether) Backbones.

We have synthesized a series of stimuli-responsive brush polymers by grafting azide-terminated side chains onto a self-immolative, alkyne-bearing poly(benzyl ether) backbone, which is prepared by anionic polymerization of quinone methide-based monomers. Upon exposure to a decapping reagent (Pd(0) or F), these brush polymers undergo an irreversible degradation cascade from head to tail to yield individual side chains. It is observed that several factors affect the depolymerization kinetics, including solvent polarity, type of counterion, the rate of the decapping chemistry, and interestingly, the rigidity of the side chains.

Improving the Enzymatic Stability and the Pharmacokinetics of Oligonucleotides via DNA-Backboned Bottlebrush Polymers.

Herein, we design and synthesize site-specifically PEGylated oligonucleotide hairpins and demonstrate that their ability to undergo hybridization chain reaction is nearly unaffected by the PEGylation. The resulting DNA-backboned bottlebrush polymers with PEG side chains exhibit increased resistance against nucleolytic degradation, enhanced thermal stabilities, and elevated blood retention times in vivo, which collectively pave the way for more therapeutically focused DNA nanostructure designs.

Molecular spherical nucleic acids.

Herein, we report a class of molecular spherical nucleic acid (SNA) nanostructures. These nano-sized single molecules are synthesized from T polyoctahedral silsesquioxane and buckminsterfullerene C scaffolds, modified with 8 and 12 pendant DNA strands, respectively. These conjugates have different DNA surface densities and thus exhibit different levels of nuclease resistance, cellular uptake, and gene regulation capabilities; the properties displayed by the C SNA conjugate are closer to those of conventional and prototypical gold nanoparticle SNAs.

Depth-Profiling the Nuclease Stability and the Gene Silencing Efficacy of Brush-Architectured Poly(ethylene glycol)-DNA Conjugates.

PEGylation of an oligonucleotide using a brush polymer can improve its biopharmaceutical characteristics, including enzymatic stability and biodistribution. Herein, we quantitatively explore the nuclease accessibility of the nucleic acid as a function of "depth" toward the backbone of the brush polymer. It is found that protein accessibility decreases as the nucleotide is located closer to the backbone.

Modulating the Cellular Immune Response of Oligonucleotides by Brush Polymer-Assisted Compaction.

Unwanted stimulation of the innate immune system by foreign nucleic acids has been one of the major barriers preventing bioactive sequences from reaching market. Foreign nucleic acids can be recognized by multiple pattern recognition receptors (PRRs), which trigger a signaling cascade to activate host defense systems, leading to a range of side effects. This study demonstrates that polyethylene glycol (PEG)-modified DNA strands can greatly reduce the activation of the innate immune system, and the extent of reduction is dependent upon polymer architecture.

Photolabile Self-Immolative DNA-Drug Nanostructures.

It is often desirable to simultaneously target different cellular pathways to improve the overall efficacy of a drug or to circumvent drug resistance in therapeutic treatments. Nucleic acid therapy has been considered attractive for such combination therapies due to its possible synergistic effects with traditional chemotherapy, especially for targets that do not yet have small molecule inhibitors. However, the co-delivery of nucleic acids and chemotherapeutics typically involves the use of inherently cytotoxic/immunogenic, polycationic carrier systems, for which the benefit is often overshadowed by adverse side effects.

Effect of PEG Architecture on the Hybridization Thermodynamics and Protein Accessibility of PEGylated Oligonucleotides.

PEGylation is an attractive approach to modifying oligonucleotides intended for therapeutic purposes. PEG conjugation reduces protein interactions with the oligonucleotide, and helps to overcome their intrinsic biopharmaceutical shortcomings, such as poor enzymatic stability, rapid body clearance, and unwanted immunostimulation. However, the effect of PEG architecture and the manner in which the PEG component interferes with the hybridization of the oligonucleotide remain poorly understood.

Blurring the Role of Oligonucleotides: Spherical Nucleic Acids as a Drug Delivery Vehicle.

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.

Effective Antisense Gene Regulation via Noncationic, Polyethylene Glycol Brushes.

Negatively charged nucleic acids are often complexed with polycationic transfection agents before delivery. Herein, we demonstrate that a noncationic, biocompatible polymer, polyethylene glycol, can be used as a transfection vector by forming a brush polymer-DNA conjugate. The brush architecture provides embedded DNA strands with enhanced nuclease stability and improved cell uptake.

Providing Oligonucleotides with Steric Selectivity by Brush-Polymer-Assisted Compaction.

Difficult biopharmaceutical characteristics of oligonucleotides, such as poor enzymatic stability, rapid clearance by reticuloendothelial organs, immunostimulation, and coagulopathies, limit their application as therapeutics. Many of these side effects are initiated via sequence-specific or nonsequence-specific interactions with proteins. Herein, we report a novel form of brush-polymer/DNA conjugate that provides the DNA with nanoscale steric selectivity: Hybridization kinetics with complementary DNA remains nearly unaffected, but interactions with proteins are significantly retarded.

Light-triggered, self-immolative nucleic Acid-drug nanostructures.

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.

Facile synthesis of nucleic acid-polymer amphiphiles and their self-assembly.

A solid-phase synthesis for nucleic acid-polymer amphiphiles is developed. Using this strategy, several DNA-b-polymer amphiphiles are synthesized, and their self-assembly in aqueous solution is investigated. This general method can in principle be extended to nearly all polymers synthesized by atom transfer radical polymerization to produce a variety of nucleic acid-polymer conjugates.

Polycondensation of polymer brushes via DNA hybridization.

Triblock copolymer brushes were functionalized with nucleic acid sequences, which allowed the polymers to connect head-to-tail and form supramolecular nanostructures. Two approaches were designed and implemented, using either a palindromic DNA attached to both ends of the polymer or two different DNA sequences attached regiospecifically. Given appropriate conditions, the DNA-brush conjugates self-assembled to form either nanoworms with length up to several microns or cross-linked networks.