100th Anniversary of Macromolecular Science Viewpoint: Toward Artificial Life-Supporting Macromolecules

Dynamic Assembly of DNA Nanostructures in Cancer Cells Enables the Coupling of Autophagy Activating and Real-Time Tracking

Developing dynamic nanostructures for in situ regulation of biological processes inside living cells is of great importance in biomedical research. Herein we report the cascaded assembly of Y-shaped branched DNA nanostructure (YDN) during intracellular autophagy. YDN contains one arm with semi-i-motif sequence and Cy3-BHQ2, and another arm with an apurinic/apyrimidinic (AP) site and Cy5-BHQ3. Upon uptake by cancer cells, intermolecular i-motif structures are formed in response to lysosomal H+, causing the formation of YDN-dimer and the recovery of Cy3 fluorescence; when escapes occur from the lysosome to the cytoplasm, the YDN-dimer responds to the overexpressed APE1, leading to the assembly of YDN into the DNA network and the fluorescence recovery of Cy5. Simultaneously, the cascaded assembly activates autophagy, and thus the process of assembly of YDN and autophagy flux can be spatiotemporally coupled. This work illustrates the potential of DNA nanostructures for the in situ regulation of intracellular dynamic events with spatiotemporal control.

Nucleic-Acid-Templated Synthesis of Smart Polymer Vectors for Gene Delivery

Nucleic acids are information-rich and readily available biomolecules, which can be used to template the polymerization of synthetic macromolecules. Here, we highlight the control over the size, composition, and sequence one can nowadays obtain by using this methodology. We also highlight how templated processes exploiting dynamic covalent polymerization can, in return, result in therapeutic nucleic acids fabricating their own dynamic delivery vector - a biomimicking concept that can provide original solutions for gene therapies.

Macromolecular Information Transfer

Macromolecular information transfer can be defined as the process by which a coded monomer sequence is communicated from one macromolecule to another. In such a transfer process, the information sequence can be kept identical, transformed into a complementary sequence or even translated into a different molecular language. Such mechanisms are crucial in biology and take place in DNA→DNA replication, DNA→RNA transcription and RNA→protein translation. In fact, there would be no life on Earth without macromolecular information transfer. Mimicking such processes with synthetic macromolecules would also be of major scientific relevance because it would open up new avenues for technological applications (e.g. data storage and processing) but also for the creation of artificial life. In this important context, this minireview summarizes recent research about information transfer in synthetic oligomers and polymers. Medium- and long-term perspectives are also discussed.

Waste-derived biocatalysts for pesticide degradation

A green approach to produce a cellulose-derived biocatalyst containing hydroxamic acids targeted for the neutralization of toxic organophosphates is shown. The cellulose source, rice husk, is among the largest agricultural waste worldwide and can be strategically functionalized, broadening its sustainable application. Herein, rice husk was oxidized in different degrees, leading to carboxylic acid-based colloidal and solid samples. These were functionalized with hydroxamic acids via amide bonds and fully characterized. The hydroxamic acid derived biocatalysts were evaluated in the cleavage of toxic organophosphates, including the pesticide Paraoxon. Catalytic increments reached up to 10⁷-fold compared to non-catalyzed reactions. Most impressively, the materials showed P atom-selectivity and recyclability features. This guarantees only one reaction pathway that leads to less toxic products, hereby, detoxifies. Overall, highly sustainable catalysts are presented, that benefits from waste source, its green functionalization and is successfully employed for the promotion of chemical security of threatening organophosphates. To the best of our knowledge, this is the first report of a hydroxamate-derived rice husk (selectively modified at the C6 of cellulose) and its application in organophosphates reaction.

On the photopolymerization of mevalonic lactone methacrylate: exposing the potential of an overlooked monomer

This manuscript will exhibit the photopolymerization of mevalonic lactone methacrylate, an overlooked monomer, and how functional polymers with lactone pendant units can be synthesized.

Two-Dimensional Polymers and Polymerizations

Synthetic chemists have developed robust methods to synthesize discrete molecules, linear and branched polymers, and disordered cross-linked networks. However, two-dimensional polymers (2DPs) prepared from designed monomers have been long missing from these capabilities, both as objects of chemical synthesis and in nature. Recently, new polymerization strategies and characterization methods have enabled the unambiguous realization of covalently linked macromolecular sheets. Here we review 2DPs and 2D polymerization methods. Three predominant 2D polymerization strategies have emerged to date, which produce 2DPs either as monolayers or multilayer assemblies. We discuss the fundamental understanding and scope of each of these approaches, including: the bond-forming reactions used, the synthetic diversity of 2DPs prepared, their multilayer stacking behaviors, nanoscale and mesoscale structures, and macroscale morphologies. Additionally, we describe the analytical tools currently available to characterize 2DPs in their various isolated forms. Finally, we review emergent 2DP properties and the potential applications of planar macromolecules. Throughout, we highlight achievements in 2D polymerization and identify opportunities for continued study.

Unraveling Sequence Effect on Glass Transition Temperatures of Discrete Unconjugated Oligomers

Sequence plays a critical role in enabling unique properties and functions of natural biomolecules, which has promoted the rapid advancement of synthetic sequence-defined polymers in recent decades. Particularly, investigation of short chain sequence-defined oligomers (also called discrete oligomers) on their properties has become a hot topic. However, most studies have focused on discrete oligomers with conjugated structures. In contrast, unconjugated oligomers remain relatively underexplored. In this study, three pairs of discrete oligomers with the same composition but different sequence for each pair are employed for investigating their glass transition temperatures (T_g s). The resultant T_g s of sequenced oligomers in each pair are found to be significantly different (up to 11.6 °C), attributable to variations in molecular packing as demonstrated by molecular dynamics and density function theory simulations. Intermolecular interaction is demonstrated to have less impact on T_g s than intramolecular interaction. The mechanistic investigation into two model dimers suggests that monomer sequence caused the difference in intramolecular rotational flexibility of the sequenced oligomers. In addition, despite having different monomer sequence and T_g s, the oligomers have very similar solubility parameters, which supports their potential use as effective oligomeric plasticizers to tune the T_g s of bulk polymer materials.

Sequence Control from Mixtures: Switchable Polymerization Catalysis and Future Materials Applications

There is an ever-increasing demand for higher-performing polymeric materials counterbalanced by the need for sustainability throughout the life cycle. Copolymers comprising ester, carbonate, or ether linkages could fulfill some of this demand as their monomer-polymer chemistry is closer to equilibrium, facilitating (bio)degradation and recycling; many monomers are or could be sourced from renewables or waste. Here, an efficient and broadly applicable route to make such copolymers is discussed, a form of switchable polymerization catalysis which exploits a single catalyst, switched between different catalytic cycles, to prepare block sequence selective copolymers from monomer mixtures. This perspective presents the principles of this catalysis, catalyst design criteria, the selectivity and structural copolymer characterization tools, and the properties of the resulting copolymers. Uses as thermoplastic elastomers, toughened plastics, adhesives, and self-assembled nanostructures, and for programmed degradation, among others, are discussed. The state-of-the-art research into both catalysis and products, as well as future challenges and directions, are presented.

Halogen-Bond Mediated 3D Confined Assembly of AB Diblock Copolymer and C Homopolymer Blends

Halogen-bond driven assembly, a world parallel to hydrogen-bond, has emerged as an attractive tool for constructing (macro)molecular arrangement. However, knowledge about halogen-bond mediated confined-assembly in emulsion droplets is limited so far. An I^…. N bond mediated confined-assembly pathway to enable order-order phase transitions is reported here. Compared to hydrogen bonds, the distinct features of halogen bonds (e.g., higher directionality, hydrophobicity, favored in polar solvents), offers opportunities to achieve novel nanostructures and materials. Polystyrene-b-poly(4-vinyl pyridine) (PS-b-P4VP) AB diblock copolymer is chosen as halogen acceptor, while an iodotetrafluorophenoxy substituted C-type homopolymer, (poly(3-(2,3,5,6-tetrafluoro-4-iodophenoxy)propyl acrylate), PTFIPA) is designed as halogen donor, synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Formation of halogen bonding donor-acceptor pairs between the PTFIPA homopolymer and the P4VP segments presented in PS-b-P4VP, increase the volume of P4VP domains, in turn inducing an order-to-order morphology transition sequence: changing from spherical → cylindrical → lamellar → inverse cylindrical, by tuning the PTFIPA content and choice of surfactant. Subsequent selective swelling/deswelling of the P4VP domains give rise to further internal morphology transitions, creating tailored mesoporous microparticles, disassembled nanodiscs, and superaggregates. It is believed that these results will stimulate further examinations of halogen bonding interactions in emulsion droplets and many areas of application.

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.

Protecting-Group-Free Iterative Exponential Growth Method for Synthesizing Sequence-Defined Polymers

As a main synthetic strategy for monodisperse sequence-defined polymers, the known iterative exponential growth (IEG) methods were all developed on protecting-group chemistry, where the additional deprotection reactions increased their synthetic steps and decreased their atom economy. In this study, we developed a protecting-group-free IEG method for the formation of sequence-defined polymers by combining three orthogonal click reactions of copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC), sulfur-fluoride exchange reaction (SuFEx), and Ugi four-component reaction (Ugi-4CR). In this approach, oligomer synthesis began with three parallel CuAAC, SuFEx, and Ugi-4CR couplings among three monomers each with two orthogonal clickable end groups. By iteratively applying parallel CuAAC, SuFEx, and Ugi-4CR to couple three resultant oligomers, each having two orthogonal clickable terminals, this approach could exponentially grow three different sequence-defined polymers simultaneously with high efficiency, requiring no protecting-group chemistry. Additionally, each Ugi-4CR coupling reaction could introduce two external side groups to provide the molecular variation and side-chain functionalization for the resultant sequence-defined polymers.

Geared Toward Applications: A Perspective on Functional Sequence-Controlled Polymers

Sequence-controlled polymers are an emerging class of synthetic polymers with a regulated sequence of monomers. In the past decade, tremendous progress has been made in the synthesis of polymers with the sophisticated sequence control approaching the level manifested in biopolymers. In contrast, the exploration of novel functions that can be achieved by controlling synthetic polymer sequences represents an emerging focus in polymer science. This Viewpoint will survey recent advances in the functional applications of sequence-controlled polymers and provide a perspective on the challenges and outlook for pursuing future applications of this fascinating class of macromolecules.

Reflection on the Matyjaszewski Lab Webinar Series and the Rise of Webinars in Polymer Chemistry

Webinar series are helping our community of polymer scientists to stay engaged and connected, despite the cancellation of in-person meetings and the periodic closure of laboratories to contain the spread of the coronavirus pandemic. The sustainable and inclusive character of these virtual events make them valuable learning and networking opportunities. As organizers of the Matyjaszewski Lab Webinar Series, we share herein our experience, highlighting the benefits of virtual meetings and providing a short guide for webinar organizers. Researchers, particularly young scientists, are encouraged to organize such virtual events to broaden their skills and strengthen their professional network.

Templated approach to well-defined, oxidatively coupled conjugated polymers

Templated oxidative polymerization affords organic soluble, oxidatively doped PEDOT-based polymers with controlled molecular weights and low dispersities (Đ ∼ 1.2) for the first time.

Chemical conjugation of nucleic acid aptamers and synthetic polymers

This minireview describes the synthesis, characterization and properties of aptamer–polymer conjugates. This new class of polymer bioconjugates combines the advantages of synthetic polymers and folded nucleic acids.

Damage and Repair in Informational Poly(N-substituted urethane)s

The degradation and repair of uniform sequence-defined poly(N-substituted urethane)s was studied. Polymers containing an ω-OH end-group and only ethyl carbamate main-chain repeat units rapidly degrade in NaOH solution through an ω→α depolymerization mechanism with no apparent sign of random chain cleavage. The degradation mechanism is not notably affected by the nature of the side-chain N-substituents and took place for all studied sequences. On the other hand, depolymerization is significantly influenced by the molecular structure of the main-chain repeat units. For instance, hexyl carbamate main-chain motifs block unzipping and can therefore be used to control the degradation of specific sequence sections. Interestingly, the partially degraded polymers can also be repaired; for example by using a combination of N,N'-disuccinimidyl carbonate with a secondary amine building-block. Overall, these findings open up interesting new avenues for chain-healing and sequence editing.

Supramolecular assembly of DNA-constructed vesicles

The self-assembly of DNA hybrids possessing tetraphenylethylene sticky ends at both sides into vesicular architectures in aqueous medium is demonstrated. Cryo-electron microscopy reveals the formation of different types of morphologies from the amphiphilic DNA-hybrids. Depending on the conditions, either an extended (sheet-like) or a compact (columnar) alignment of the DNA hybrids is observed. The different modes of DNA arrangement lead to the formation of vesicles appearing either as prolate ellipsoids (type I) or as spheres (type II). The type of packing has a significant effect on the accessibility of the DNA, as evidenced by intercalation and light-harvesting experiments. Only the vesicles exhibiting the sheet-like DNA alignment are accessible for intercalation by ethidium bromide or for the integration of chromophore-labelled DNA via a strand exchange process. The dynamic nature of type I vesicles enables their elaboration into artificial light-harvesting complexes by DNA-guided introduction of Cy3-acceptor chromophores. DNA-constructed vesicles of the kind shown here represent versatile intermediates that are amenable to further modification for tailored nanotechnology applications.

Solid-Phase Synthesis of Sequence-Defined Informational Oligomers

Genetic biopolymers utilize defined sequences and monomer-specific molecular recognition to store and transfer information. Synthetic polymers that mimic these attributes using reversible covalent chemistry for base-pairing pose unique synthetic challenges. Here, we describe a solid-phase synthesis methodology for the efficient construction of ethynyl benzene oligomers with specific sequences of aniline and benzaldehyde subunits. Handling these oligomers is complicated by the fact that they often exhibit multiple conformations because of intra- or intermolecular pairing. We describe conditions that allow the dynamic behavior of these oligomers to be controlled so that they may be manipulated and characterized without needing to mask the recognition units with protecting groups.

Selective Bond Cleavage in Informational Poly(Alkoxyamine Phosphodiester)s

The collision-induced dissociation (CID) of sequence-defined poly(alkoxyamine phosphodiester)s is studied by electrospray ionization mass spectrometry. These informational polymers are synthesized using three different nitroxide building blocks, namely proxyl-, SG1-, and TEMPO-derivatives. For a polymer containing TEMPO- and SG1-based main chain alkoxyamines, it is found that both types of alkoxyamines break in CID tandem mass spectrometry (MS/MS). However, SG1-sites are preferentially cleaved and this predominance can be increased by reducing collision energy, even though selective bond fragmentation is not observed. On the other hand, for a polymer containing proxyl- and SG1-alkoxyamines, selective bond cleavage is observed at all studied collision energies. The SG1-alkoxyamines can be first cleaved in MS/MS conditions and secondly the proxyl-alkoxyamines in pseudo-MS³ conditions. These results open up interesting new avenues for the design of readable, erasable or programmable informational polymers.

Stereocontrolled, multi-functional sequence-defined oligomers through automated synthesis

In this work, stereocontrolled sequence-defined oligomers were prepared using an automated thiolactone-based platform that allows post-synthesis functionalisation.