Photocontrolled Synthesis of Abiotic Sequence-Defined Oligo(Phosphodiester)s

Advanced Smart Biomaterials for Regenerative Medicine and Drug Delivery Based on Phosphoramidite Chemistry: From Oligonucleotides to Precision Polymers

Over decades of development, while phosphoramidite chemistry has been known as the leading method in commercial synthesis of oligonucleotides, it has also revolutionized the fabrication of sequence-defined polymers (SDPs), offering novel functional materials in polymer science and clinical medicine. This review has introduced the evolution of phosphoramidite chemistry, emphasizing its development from the synthesis of oligonucleotides to the creation of universal SDPs, which have unlocked the potential for designing programmable smart biomaterials with applications in diverse areas including data storage, regenerative medicine and drug delivery. The key methodologies, functions, biomedical applications, and future challenges in SDPs, have also been summarized in this review, underscoring the significance of breakthroughs in precisely synthesized materials.

Polymers Strive for Accuracy: From Sequence-Defined Polymers to mRNA Vaccines against COVID-19 and Polymers in Nucleic Acid Therapeutics

Unquestionably, polymers have influenced the world over the past 100 years. They are now more crucial than ever since the COVID-19 pandemic outbreak. The pandemic paved the way for certain polymers to be in the spotlight, namely sequence-defined polymers such as messenger ribonucleic acid (mRNA), which was the first type of vaccine to be authorized in the U.S. and Europe to protect against the SARS-CoV-2 virus. This rise of mRNA will probably influence scientific research concerning nucleic acids in general and RNA therapeutics in specific. In this Perspective, we highlight the recent trends in sequence-controlled and sequence-defined polymers. Then we discuss mRNA vaccines as an example to illustrate the need of ultimate sequence control to achieve complex functions such as specific activation of the immune system. We briefly present how mRNA vaccines are produced, the importance of modified nucleotides, the characteristic features, and the advantages and challenges associated with this class of vaccines. Finally, we discuss the chances and opportunities for polymer chemistry to provide solutions and contribute to the future progress of RNA-based therapeutics. We highlight two particular roles of polymers in this context. One represents conjugation of polymers to nucleic acids to form biohybrids. The other is concerned with advanced polymer-based carrier systems for nucleic acids. We believe that polymers can help to address present problems of RNA-based therapeutic technologies and impact the field beyond the COVID-19 pandemic.

Hierarchical Nanomaterials Assembled from Peptoids and Other Sequence-Defined Synthetic Polymers

In nature, the self-assembly of sequence-specific biopolymers into hierarchical structures plays an essential role in the construction of functional biomaterials. To develop synthetic materials that can mimic and surpass the function of these natural counterparts, various sequence-defined bio- and biomimetic polymers have been developed and exploited as building blocks for hierarchical self-assembly. This review summarizes the recent advances in the molecular self-assembly of hierarchical nanomaterials based on peptoids (or poly-N-substituted glycines) and other sequence-defined synthetic polymers. Modern techniques to monitor the assembly mechanisms and characterize the physicochemical properties of these self-assembly systems are highlighted. In addition, discussions about their potential applications in biomedical sciences and renewable energy are also included. This review aims to highlight essential features of sequence-defined synthetic polymers (e.g., high stability and protein-like high-information content) and how these unique features enable the construction of robust biomimetic functional materials with high programmability and predictability, with an emphasis on peptoids and their self-assembled nanomaterials.

Layered assembly of cationic and anionic supramolecular polymers

The chemical synthesis and the supramolecular assembly of an aromatic oligoamine are described. The self-assembly of the cationic oligomers in aqueous solution leads to the formation of vesicular objects. The assembly process of the oligomers is monitored by absorption and fluorescence spectroscopy and the formed vesicles are characterized by atomic force and transmission electron microscopy. The electrostatic complementarity of anionic supramolecular polymers sheets and the cationic vesicles is used for a layered assembly process.

Design of Abiological Digital Poly(phosphodiester)s

In biological systems, the storage and transfer of genetic information rely on sequence-controlled nucleic acids such as DNA and RNA. It has been realized for quite some time that this property is not only crucial for life but could also be very useful in human applications. For instance, DNA has been actively investigated as a digital storage medium over the past decade. Indeed, the "hard-disk of life" is an obvious choice and a highly optimized material for storing data. Through decades of nucleic acids research, technological tools for parallel synthesis and sequencing of DNA have been readily available. Consequently, it has already been demonstrated that different types of documents (e.g., texts, images, videos, and industrial data) can be stored in chemically synthesized DNA libraries. However, DNA is subject to biological constraints, and its molecular structure cannot be easily varied to match technological needs. In fact, DNA is not the only macromolecule that enables data storage. In recent years, it has been demonstrated that a wide variety of synthetic polymers can also be used for such a purpose. Indeed, modern polymer synthesis allows the preparation of synthetic macromolecules with precisely controlled monomer sequences. Altogether, about a dozens of synthetic digital polymers have already been described, and many more can be foreseen. Among them, sequence-defined poly(phosphodiester)s are one of the most promising options. These polymers are prepared by stepwise phosphoramidite chemistry like chemically synthesized oligonucleotides. However, they are constructed with non-natural building blocks and therefore share almost no structural characteristics with nucleic acids, except phosphate repeat units. Still, they contain readable digital messages that can be deciphered by nanopore sequencing or mass spectrometry sequencing. In this Account, we describe our recent research efforts in synthesizing and sequencing optimal abiological digital poly(phosphodiester)s. A major advantage of these polymers over DNA is that their molecular structure can easily be varied to tune their properties. During the last 5 years, we have engineered the molecular structure of these polymers to adjust crucial parameters such as the storage density, storage capacity, erasability, and readability. Consequently, high-capacity PPDE chains, containing hundreds of bits per chains, can now be synthesized and efficiently sequenced using a routine mass spectrometer. Furthermore, sequencing data can be automatically decrypted with the help of decoding software. This new type of coded matter can also be edited using practical physical triggers such as light and organized in space by programmed self-assembly. All of these recent improvements are summarized and discussed herein.

Multi-level patterning nucleic acid photolithography

The versatile and tunable self-assembly properties of nucleic acids and engineered nucleic acid constructs make them invaluable in constructing microscale and nanoscale devices, structures and circuits. Increasing the complexity, functionality and ease of assembly of such constructs, as well as interfacing them to the macroscopic world requires a multifaceted and programmable fabrication approach that combines efficient and spatially resolved nucleic acid synthesis with multiple post-synthetic chemical and enzymatic modifications. Here we demonstrate a multi-level photolithographic patterning approach that starts with large-scale in situ surface synthesis of natural, modified or chimeric nucleic acid molecular structures and is followed by chemical and enzymatic nucleic acid modifications and processing. The resulting high-complexity, micrometer-resolution nucleic acid surface patterns include linear and branched structures, multi-color fluorophore labeling and programmable targeted oligonucleotide immobilization and cleavage.

Sequence-defined non-natural polymers: synthesis and applications

Sequence-defined polymer: A promising gateway for the next generation polymeric materials and vast opportunities for new synthetic strategies, functional diversity and its material and biomedical applications.

Recent Developments in Solid-Phase Strategies towards Synthetic, Sequence-Defined Macromolecules

Sequence-control in synthetic polymers is an important contemporary research area because it provides the opportunity to create completely novel materials for structure-function studies. This is especially relevant for biomimetic polymers, bioactive and information security materials. The level of control is strongly dependent and inherent upon the polymerization technique utilized. Today, the most established method yielding monodispersity and monomer sequence-definition is solid-phase synthesis. This Focus Review highlights recent advances in solid-phase strategies to access synthetic, sequence-defined macromolecules. Alternatives strategies towards sequence-defined macromolecules are also briefly summarized.

Photoinduced ring-opening polymerisation of l-lactide via a photocaged superbase

The phototriggered ring-opening polymerisation of l-lactide is demonstrated for the first time using a photocaged tetramethylguanidine.