Visible Light Conjugation with Triazolinediones as a Route to Degradable Poly(ethylene glycol)-Lipids for mRNA Lipid Nanoparticle Formulation.

Polyethylene glycol (PEG) is considered as the gold standard for colloidal stabilization of nanomedicines, yet PEG is non-degradable and lacks functionality on the backbone. Herein, we introduce concomitantly PEG backbone functionality and degradability via a one-step modification with 1,2,4-triazoline-3,5-diones (TAD) under green light. The TAD-PEG conjugates are degradable in aqueous medium under physiological conditions, with the rate of hydrolysis depending on pH and temperature. Subsequently, a PEG-lipid is modified with TAD-derivatives and successfully used for messenger RNA (mRNA) lipid nanoparticle (LNP) delivery, thereby improving mRNA transfection efficiency on multiple cell cultures in vitro. In vivo, in mice, mRNA LNP formulation exhibited a similar tissue distribution as common LNPs, with a slight decrease in transfection efficiency. Our findings pave the road towards the design of degradable, backbone-functionalized PEG for applications in nanomedicine and beyond.

Reading Information Stored in Synthetic Macromolecules.

The storage of information in synthetic (macro)molecules provides an attractive alternative for current archival storage media, and the advancements made within this area have prompted the investigation of such molecules for numerous other applications (e.g., anti-counterfeiting tags, steganography). While different strategies have been described for storing information at the molecular level, this Perspective aims to provide a critical overview of the most prominent approaches that can be utilized for retrieving the encoded information. The major part will focus on the sequence determination of synthetic macromolecules, wherein information is stored by the precise arrangement of constituting monomers, with an emphasis on chemically aided strategies, (tandem) mass spectrometry, and nanopore sensing. In addition, recent progress in utilizing (mixtures of) small molecules for information storage will be discussed. Finally, the closing remarks aim to highlight which strategy we believe is the most suitable for a series of specific applications, and will also touch upon the future research avenues that can be pursued for reading (macro)molecular information.

Sequence-Defined Mikto-Arm Star-Shaped Macromolecules.

The synthesis of sequence-defined, discrete star-shaped macromolecules is a major challenge due to the lack of straightforward and versatile approaches. Here, a robust strategy is proposed that allows not only the preparation of sequence-defined mikto-arm star-shaped macromolecules but also the synthesis of a series of unprecedented discrete, multifunctional complex architectures with molar masses above 11 kDa. The iterative approach reported makes use of readily available building blocks and results in asymmetrically branched macromolecules with high purity and yields, which is showcased with monodisperse mikto-arm three-, four-, and five-arm star-shaped structures that were all characterized via LC-MS, MALDI-ToF, and NMR. This effective strategy drastically improves upon synthetic abilities of polymer chemists by enabling simultaneously sequence definition, precision insertion of branching points, as well as the orthogonal end-group functionalization of complex polymeric architectures. The presented approach, which can be translated to different platforms such as peptides and peptoids, is therefore particularly interesting in biomedical applications for which multiple different functional moieties on a single discrete macromolecule are needed.

Sequencing of Uniform Multifunctional Oligoesters via Random Chain Cleavages.

Sequence-defined polymers have been the object of many fascinating studies that focus on their implementation in both material and life science applications. In parallel, iterative synthetic methodologies have become more efficient, whereas the structure elucidation of these molecules is generally dependent on MS/MS analysis. Here, we report an alternative, simple strategy for the determination of the monomer order of uniform oligo(thioether ester)s. This approach, which relies on random cleavages of ester units within the macromolecular backbone via a basic treatment, enables the swift characterization of these macromolecules without the need for MS/MS. Consequently, this method can be used for decoding any information stored within the primary structure of oligoesters by means of ESI- or LC-MS. Finally, we speculate that a range of structurally diverse backbones could be susceptible towards this approach, which could promptly expand the library of chemically sequenceable macromolecules.

Rewritable Macromolecular Data Storage with Automated Read-out.

Rewriting data stored on synthetic macromolecules is an interesting feature, even though it is considered as being quite challenging within the area of digital macromolecules. In this context, we initially studied a strategy for modifying the position tag of sequence-encoded macromolecules in a reversible manner. The efficiency of this method, which relies on the orthogonal cleavage of a thioester moiety via aminolysis, was demonstrated by modifying parts of an exemplary sentence. Simultaneously, a novel algorithm was developed to ease the read-out of macromolecular information by means of MS/MS techniques. This program, Oligoreader, can identify potential information-containing macromolecules from a series of MS1 spectra, analyze the corresponding MS2 spectra, and finally decode the data. Consequently, the algorithm simplifies the entire read-out process by avoiding any interference from the operator, which increases the potential for blind sequencing of uniform macromolecules.

Sequence-Encoded Macromolecules with Increased Data Storage Capacity through a Thiol-Epoxy Reaction.

Sequence-encoded oligo(thioether urethane)s with two different coding monomers per backbone unit were prepared via a solid phase, two-step iterative protocol based on thiolactone chemistry. The first step of the synthetic cycle consists of the thiolactone ring opening with a primary amine, whereby the in situ released thiol is immediately reacted with an epoxide. In the second step, the thiolactone group is reinstalled to initiate the next cycle. This strategy allows to introduce two different coding monomers per synthetic cycle, rendering the resulting macromolecules especially attractive in the area of (macro)molecular data storage because of their increased data storage capacity. Subsequently, the efficiency of the herein reported synthesis route and the applicability of the dual-encoded sequence-defined macromolecules as a potential data storage platform have been demonstrated by unraveling the exact monomer order using tandem mass spectrometry techniques.

Applications of Discrete Synthetic Macromolecules in Life and Materials Science: Recent and Future Trends.

In the last decade, the field of sequence-defined polymers and related ultraprecise, monodisperse synthetic macromolecules has grown exponentially. In the early stage, mainly articles or reviews dedicated to the development of synthetic routes toward their preparation have been published. Nowadays, those synthetic methodologies, combined with the elucidation of the structure-property relationships, allow envisioning many promising applications. Consequently, in the past 3 years, application-oriented papers based on discrete synthetic macromolecules emerged. Hence, material science applications such as macromolecular data storage and encryption, self-assembly of discrete structures and foldamers have been the object of many fascinating studies. Moreover, in the area of life sciences, such structures have also been the focus of numerous research studies. Here, it is aimed to highlight these recent applications and to give the reader a critical overview of the future trends in this area of research.