Harnessing Albumin as a Carrier for Cancer Therapies

DNA is traditionally known as a central genetic biomolecule in living systems. From an alternative perspective, DNA is a versatile molecular building-block for the construction of functional materials, in particular biomaterials, due to its intrinsic biological attributes, molecular recognition capability, sequence programmability, and biocompatibility. The topologies of DNA building-blocks mainly include linear, circular, and branched types. Branched DNA recently has been extensively employed as a versatile building-block to synthesize new biomaterials, and an assortment of promising applications have been explored. In this review, we discuss the progress on DNA functional materials assembled from branched DNA. We first briefly introduce the background information on DNA molecules and sketch the development history of DNA functional materials constructed from branched DNA. In the second part, the synthetic strategies of branched DNA as building-blocks are categorized into base-pairing assembly and chemical bonding. In the third part, construction strategies for the branched DNA-based functional materials are comprehensively summarized including tile-mediated assembly, DNA origami, dynamic assembly, and hybrid assembly. In the fourth part, applications including diagnostics, protein engineering, drug and gene delivery, therapeutics, and cell engineering are demonstrated. In the end, an insight into the challenges and future perspectives is provided. We envision that branched DNA functional materials can not only enrich the DNA nanotechnology by ingenious design and synthesis but also promote the development of interdisciplinary fields in chemistry, biology, medicine, and engineering, ultimately addressing the growing demands on biological and medical-related applications in the real world.

DNA Functional Materials Assembled from Branched DNA: Design, Synthesis, and Applications.

Fully addressable DNA nanostructures, especially DNA origami, possess huge potential to serve as inherently biocompatible and versatile molecular platforms. However, their use as delivery vehicles in therapeutics is compromised by their low stability and poor transfection rates. This study shows that DNA origami can be coated by precisely defined one-to-one protein-dendron conjugates to tackle the aforementioned issues. The dendron part of the conjugate serves as a cationic binding domain that attaches to the negatively charged DNA origami surface via electrostatic interactions. The protein is attached to dendron through cysteine-maleimide bond, making the modular approach highly versatile. This work demonstrates the coating using two different proteins: bovine serum albumin (BSA) and class II hydrophobin (HFBI). The results reveal that BSA-coating significantly improves the origami stability against endonucleases (DNase I) and enhances the transfection into human embryonic kidney (HEK293) cells. Importantly, it is observed that BSA-coating attenuates the activation of immune response in mouse primary splenocytes. Serum albumin is the most abundant protein in the blood with a long circulation half-life and has already found clinically approved applications in drug delivery. It is therefore envisioned that the proposed system can open up further opportunities to tune the properties of DNA nanostructures in biological environment, and enable their use in various delivery applications.

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Protein Coating of DNA Nanostructures for Enhanced Stability and Immunocompatibility.

DNA nanotechnology holds substantial promise for future biomedical engineering and the development of novel therapies and diagnostic assays. The subnanometer-level addressability of DNA nanostructures allows for their precise and tailored modification with numerous chemical and biological entities, which makes them fit to serve as accurate diagnostic tools and multifunctional carriers for targeted drug delivery. The absolute control over shape, size, and function enables the fabrication of tailored and dynamic devices, such as DNA nanorobots that can execute programmed tasks and react to various external stimuli. Even though several studies have demonstrated the successful operation of various biomedical DNA nanostructures both in vitro and in vivo, major obstacles remain on the path to real-world applications of DNA-based nanomedicine. Here, we summarize the current status of the field and the main implementations of biomedical DNA nanostructures. In particular, we focus on open challenges and untackled issues and discuss possible solutions.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/anie.201916390

Challenges and Perspectives of DNA Nanostructures in Biomedicine

DNA Nanostructures at the Interface with Biology

The development of nucleic acid therapeutics has been hampered by issues associated with their stability and in vivo delivery. To address these challenges, we describe a new strategy to engineer DNA structures with strong binding affinity to human serum albumin (HSA). HSA is the most abundant protein in the blood and has a long circulation half-life (19 days). It has been shown to hinder phagocytosis, is retained in tumors, and aids in cellular penetration. Indeed, HSA has already been successfully used for the delivery of small-molecule drugs and nanoparticles. We show that conjugating dendritic alkyl chains to DNA creates amphiphiles that exhibit high-affinity (Kd in low nanomolar range) binding to HSA. Notably, complexation with HSA did not hinder the activity of silencing oligonucleotides inside cells, and the degradation of DNA strands in serum was significantly slowed. We also show that, in a site-specific manner, altering the number and orientation of the amphiphilic ligand on a self-assembled DNA ...

Development of DNA Nanostructures for High-Affinity Binding to Human Serum Albumin

Biochemical networks interconnect, grow and evolve to express new properties as different chemical pathways are selected during a continuous cycle of energy consumption and transformation. In contrast, synthetic systems that push away from equilibrium usually return to the same self-assembled state, often generating waste that limits system recyclability and prevents the formation of adaptable networks. Here we show that annealing by slow proton dissipation selects for otherwise inaccessible morphologies of fibres built from DNA and cyanuric acid. Using single-molecule fluorescence microscopy, we observe that proton dissipation influences the growth mechanism of supramolecular polymerization, healing gaps within fibres and converting highly branched, interwoven networks into nanocable superstructures. Just as the growth kinetics of natural fibres determine their structural attributes to modulate function, our system of photoacid-enabled depolymerization and repolymerization selects for healed materials to yield organized, robust fibres. Our method provides a chemical route for error-checking, distinct from thermal annealing, that improves the morphologies and properties of supramolecular materials using out-of-equilibrium systems.

A dissipative pathway for the structural evolution of DNA fibres.

Templated synthesis of spherical RNA nanoparticles with gene silencing activity

Thermosetting supramolecular polymerization of compartmentalized DNA fibers with stereo sequence and length control

The self-assembly of block copolymers is often rationalized by structure and microphase separation; pathways that diverge from this parameter space may provide new mechanisms of polymer assembly. Here, we show that the sequence and length of single-stranded DNA directly influence the self-assembly of sequence-defined DNA block copolymers. While increasing the length of DNA led to predictable changes in self-assembly, changing only the sequence of DNA produced three distinct structures: spherical micelles (spherical nucleic acids, SNAs) from flexible poly(thymine) DNA, fibers from semirigid mixed-sequence DNA, and networked superstructures from rigid poly(adenine) DNA. The secondary structure of poly(adenine) DNA strands drives a temperature-dependent polymerization and assembly mechanism: copolymers stored in an SNA reservoir form fibers after thermal activation, which then aggregate upon cooling to form interwoven networks. DNA is often used as a programming code that aids in nanostructure addressability and function. Here, we show that the inherent physical and chemical properties of single-stranded DNA sequences also make them an ideal material to direct self-assembled morphologies and select for new methods of supramolecular polymerization.

Michael D. Dore

Papers

Development of DNA Nanostructures for High-Affinity Binding to Human Serum Albumin

A dissipative pathway for the structural evolution of DNA fibres.

Templated synthesis of spherical RNA nanoparticles with gene silencing activity

Thermosetting supramolecular polymerization of compartmentalized DNA fibers with stereo sequence and length control

DNA Sequence and Length Dictate the Assembly of Nucleic Acid Block Copolymers.