Grafting-From Proteins Using Metal-Free PET-RAFT Polymerizations under Mild Visible-Light Irradiation

Artificial Zymogen Based on Protein-Polymer Hybrids

This study explores the synthesis and application of artificial zymogens using protein-polymer hybrids to mimic the controlled enzyme activation observed in natural zymogens. Pro-trypsin (pro-TR) and pro-chymotrypsin (pro-CT) hybrids were engineered by modifying the surfaces of trypsin (TR) and chymotrypsin (CT) with cleavable peptide inhibitors utilizing surface-initiated atom transfer radical polymerization. These hybrids exhibited 70 and 90% reductions in catalytic efficiency for pro-TR and pro-CT, respectively, due to the inhibitory effect of the grafted peptide inhibitors. The activation of pro-TR by CT and pro-CT by TR resulted in 1.5- and 2.5-fold increases in enzymatic activity, respectively. Furthermore, the activated hybrids triggered an enzyme activation cascade, enabling amplification of activity through a dual pro-protease hybrid system. This study highlights the potential of artificial zymogens for therapeutic interventions and biodetection platforms by harnessing enzyme activation cascades for precise control of catalytic activity.

Thiol-selective native grafting from polymerization for the generation of protein-polymer conjugates

Protein-polymer conjugates combine properties of biopolymers and synthetic polymers, such as specific bioactivity and increased stability, with great benefits for various applications from catalysis to biomedicine. Furthermore, polymer conjugation can mimic important posttranslational modifications of proteins such as glycosylation. There are typically two approaches to create protein-polymer conjugates: the protein is functionalized in advance with an initiator for a grafting-from method or a previously produced polymer is conjugated to the protein via a grafting-to method. In this study, we present a new approach that uses native proteins and allows for direct grafting-from using a thiol-induced, light-activated controlled radical polymerization (TIRP) that is initiated at thiols from specific cysteine residues of the protein. This straightforward method is employed to introduce polymers onto proteins and enzymes without any prior protein modifications, it works in aqueous buffer and maintains the protein's native structure and activity. The resulting protein-polymer conjugates exhibit high molar masses and low dispersities. We demonstrate the versatility of this approach by introducing different types of polymers such as hydrophilic poly(2-hydroxyethyl acrylate) (pHEAA), temperature-responsive poly(N-isopropylacrylamide) (pNIPAM) as well as glycopolymers mimicking the natural protein glycosylation and enabling selective interactions. We present successful combinations of the protein and polymer functions e.g., temperature-induced aggregation leading to an increase in enzyme activity and the introduction of artificial glycosylation inducing specific protein-protein cluster formation and giving straightforward access to glycosurfaces. Based on this straightforward, potentially scalable yet highly controlled synthesis of protein-polymer conjugates, various areas of applications are envisioned ranging from biomedicine to material sciences.

Biomass-Derived Optically Clear Adhesives for Foldable Displays

Novel acrylate monomers, derived from terpenes are synthesized for use in optically clear adhesives (OCAs) suitable for foldable displays. These OCAs are prepared using visible-light-driven polymerization, an eco-friendly method. Through physical, rheological, and mechanical characterization, the prepared OCAs possess low modulus and exhibit outstanding creep and recovery properties, making them suitable for foldable devices.

Sequence-encoded bioactive protein-multiblock polymer conjugates via quantitative one-pot iterative living polymerization

Protein therapeutics are essential in treating various diseases, but their inherent biological instability and short circulatory half-lives in vivo pose challenges. Herein, a quantitative one-pot iterative living polymerization technique is reported towards precision control over the molecular structure and monomer sequence of protein-polymer conjugates, aiming to maximize physicochemical properties and biological functions of proteins. Using this quantitative one-pot iterative living polymerization technique, we successfully develop a series of sequence-controlled protein-multiblock polymer conjugates, enhancing their biostability, pharmacokinetics, cellular uptake, and in vivo biodistribution. All-atom molecular dynamics simulations are performed to disclose the definite sequence-function relationship of the bioconjugates, further demonstrating their sequence-encoded cellular uptake behavior and in vivo biodistribution in mice. Overall, this work provides a robust approach for creating precision protein-polymer conjugates with defined sequences and advanced functions as a promising candidate in disease treatment.

Aqueous photo-RAFT polymerization under ambient conditions: synthesis of protein-polymer hybrids in open air

A photoinduced reversible addition-fragmentation chain-transfer (photo-RAFT) polymerization technique in the presence of sodium pyruvate (SP) and pyruvic acid derivatives was developed. Depending on the wavelength of light used, SP acted as a biocompatible photoinitiator or promoter for polymerization, allowing rapid open-to-air polymerization in aqueous media. Under UV irradiation (370 nm), SP decomposes to generate CO2 and radicals, initiating polymerization. Under blue (450 nm) or green (525 nm) irradiation, SP enhances the polymerization rate via interaction with the excited state RAFT agent. This method enabled the polymerization of a range of hydrophilic monomers in reaction volumes up to 250 mL, eliminating the need to remove radical inhibitors from the monomers. In addition, photo-RAFT polymerization using SP allowed for the facile synthesis of protein-polymer hybrids in short reaction times (<1 h), low organic content (≤16%), and without rigorous deoxygenation and the use of transition metal photocatalysts. Enzymatic studies of a model protein (chymotrypsin) showed that despite a significant loss of protein activity after conjugation with RAFT chain transfer agents, the grafting polymers from proteins resulted in a 3-4-fold recovery of protein activity.

Hybrid Bonding Bottlebrush Polymers Grafted from a Supramolecular Polymer Backbone

Bottlebrush polymers, macromolecules consisting of dense polymer side chains grafted from a central polymer backbone, have unique properties resulting from this well-defined molecular architecture. With the advent of controlled radical polymerization techniques, access to these architectures has become more readily available. However, synthetic challenges remain, including the need for intermediate purification, the use of toxic solvents, and challenges with achieving long bottlebrush architectures due to backbone entanglements. Herein, we report hybrid bonding bottlebrush polymers (systems integrating covalent and noncovalent bonding of structural units) consisting of poly(sodium 4-styrenesulfonate) (p(NaSS)) brushes grafted from a peptide amphiphile (PA) supramolecular polymer backbone. This was achieved using photoinitiated electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization in water. The structure of the hybrid bonding bottlebrush architecture was characterized using cryogenic transmission electron microscopy, and its properties were probed using rheological measurements. We observed that hybrid bonding bottlebrush polymers were able to organize into block architectures containing domains with high brush grafting density and others with no observable brushes. This finding is possibly a result of dynamic behavior unique to supramolecular polymer backbones, enabling molecular exchange or translational diffusion of monomers along the length of the assemblies. The hybrid bottlebrush polymers exhibited higher solution viscosity at moderate shear, protected supramolecular polymer backbones from disassembly at high shear, and supported self-healing capabilities, depending on grafting densities. Our results demonstrate an opportunity for novel properties in easily synthesized bottlebrush polymer architectures built with supramolecular polymers that might be useful in biomedical applications or for aqueous lubrication.

Ultraviolet light blocking optically clear adhesives for foldable displays via highly efficient visible-light curing

In developing an organic light-emitting diode (OLED) panel for a foldable smartphone (specifically, a color filter on encapsulation) aimed at reducing power consumption, the use of a new optically clear adhesive (OCA) that blocks UV light was crucial. However, the incorporation of a UV-blocking agent within the OCA presented a challenge, as it restricted the traditional UV-curing methods commonly used in the manufacturing process. Although a visible-light curing technique for producing UV-blocking OCA was proposed, its slow curing speed posed a barrier to commercialization. Our study introduces a highly efficient photo-initiating system (PIS) for the rapid production of UV-blocking OCAs utilizing visible light. We have carefully selected the photocatalyst (PC) to minimize electron and energy transfer to UV-blocking agents and have chosen co-initiators that allow for faster electron transfer and more rapid PC regeneration compared to previously established amine-based co-initiators. This advancement enabled a tenfold increase in the production speed of UV-blocking OCAs, while maintaining their essential protective, transparent, and flexible properties. When applied to OLED devices, this OCA demonstrated UV protection, suggesting its potential for broader application in the safeguarding of various smart devices.

Design of an Oxygen-Tolerant Photo-RAFT System for Protein-Polymer Conjugation Achieving High Bioactivity

Protein-polymer conjugates have significant potential in pharmaceutical and biomedical applications. To enable their widespread use, robust conjugation techniques are crucial. This study introduces a photo-initiated reversible addition-fragmentation chain-transfer (Photo-RAFT) polymerization system that exhibits excellent oxygen tolerance. This system allows for the synthesis of protein-polymer conjugates with high bioactivity under mild and aerobic conditions. Three photocatalytic systems utilizing Eosin Y (EY) as the photocatalyst with two different cocatalysts (ascorbic acid and triethanolamine) were investigated, each generating distinct reactive oxygen species (ROS) such as singlet oxygen, superoxide, hydrogen peroxide, and hydroxyl radicals. The impact of these ROS on three model proteins (lysozyme, albumin, and myoglobin) was evaluated, demonstrating varying bioactivities based on the ROS produced. The EY/TEOA system was identified as the optimal photo-RAFT initiating system, enabling the preparation of protein-polymer conjugates under aerobic conditions while maintaining high protein enzymatic activity. To showcase the potential of this approach, lysozyme-poly(dimethylaminoethyl acrylate) conjugates were successfully prepared and exhibited enhanced antimicrobial property against Gram-positive and Gram-negative bacteria.

NIR-Photocontrolled Aqueous RAFT Polymerization with Polymerizable Water-Soluble Zinc Phthalocyanine as Photocatalyst

In order to give an answer for the challenges of long wavelength-photocontrolled radical polymerization in aqueous solutions and to address the shortcomings of conventional near-infrared (NIR) photocatalysts (PCs) that are difficult to subject to post-treatment, we designed and synthesized a series of β-tetra-substituted water-soluble zinc phthalocyanines (β-TS-Zns) as the NIR PCs for reversible addition-fragmentation chain transfer (RAFT) polymerization successfully under irradiation with NIR (λ_max = 730 nm) light at room temperature. Importantly, the NIR PCs can also be designed as polymerizable monomers and covalently loaded on the polymer chains, which are endowed with permanent NIR photocatalysis of the resultant polymers. Moreover, the polymerization can not only be carried out in water but also in phosphate buffer saline (PBS) solution, yielding polymers with controlled molar mass and narrow dispersities (Đ = 1.03-1.25). Therefore, this NIR-photocontrolled aqueous RAFT polymerization system may provide a charming strategy for possible applications in tissue engineering biomaterial in situ benefiting from the high penetration ability of NIR light.

Polynorbornene-based bioconjugates by aqueous grafting-from ring-opening metathesis polymerization reduce protein immunogenicity

Protein-polymer conjugates (PPCs) improve therapeutic efficacy of proteins and have been widely used for the treatment of various diseases such as cancer, diabetes, and hepatitis. PEGylation is considered as the "gold standard" in bioconjugation, although in practice its clinical applications are becoming limited because of extensive evidence of immunogenicity induced by pre-existing anti-PEG antibodies in patients. Here, optimized reaction conditions for living aqueous grafting-from ring-opening metathesis polymerization (ROMP) are utilized to synthesize water-soluble polynorbornene (PNB)-based PPCs of lysozyme (Lyz-PPCs) and bacteriophage Qβ (Qβ-PPCs) as PEG alternatives. Lyz-PPCs retain nearly 100% bioactivity and Qβ-PPCs exhibit up to 35% decrease in protein immunogenicity. Qβ-PPCs derived from NB-PEG show no reduction in recognition by anti-PEG antibodies while Qβ-PPCs derived from NB-Zwit show >95% reduction as compared with Qβ-PEG. This work demonstrates a new method for PPC synthesis and the utility of grafting from PPCs to evade immune recognition.

Automated prediction of site and sequence of protein modification with ATRP initiators

One of the most straightforward and commonly used chemical modifications of proteins is to react surface amino groups (lysine residues) with activated esters. This chemistry has been used to generate protein-polymer conjugates, many of which are now approved therapeutics. Similar conjugates have also been generated by reacting activated ester atom transfer polymerization initiators with lysine residues to create biomacromolecular initiators for polymerization reactions. The reaction between activated esters and lysine amino groups is rapid and has been consistently described in almost every publication on the topic as a “random reaction”. A random reaction implies that every accessible lysine amino group on a protein molecule is equally reactive, and as a result, that the reaction is indiscriminate. Nonetheless, the literature contradicts itself by also suggesting that some lysine amino groups are more reactive than others (as a function of pK_a, surface accessibility, temperature, and local environment). If the latter assumption is correct, then the outcome of these reactions cannot be random at all, and we should be able to predict the outcome from the structure of the protein. Predicting the non-random outcome of a reaction between surface lysines and reactive esters could transform the speed at which active bioconjugates can be developed and engineered. Herein, we describe a robust integrated tool that predicts the activated ester reactivity of every lysine in a protein, thereby allowing us to calculate the non-random sequence of reaction as a function of reaction conditions. Specifically, we have predicted the intrinsic reactivity of each lysine in multiple proteins with a bromine-functionalised N-hydroxysuccinimide initiator molecule. We have also shown that the model applied to PEGylation. The rules-based analysis has been coupled together in a single Python program that can bypass tedious trial and error experiments usually needed in protein-polymer conjugate design and synthesis.

A Water-Soluble Organic Photocatalyst Discovered for Highly Efficient Additive-Free Visible-Light-Driven Grafting of Polymers from Proteins at Ambient and Aqueous Environments

Since the pioneering discovery of a protein bound to poly(ethylene glycol), the utility of protein-polymer conjugates (PPCs) is rapidly expanding to currently emerging applications. Photoinduced energy/electron-transfer reversible addition-fragmentation chain-transfer (PET-RAFT) polymerization is a very promising method to prepare structurally well-defined PPCs, as it eliminates high-cost and time-consuming deoxygenation processes due to its oxygen tolerance. However, the oxygen-tolerance behavior of PET-RAFT polymerization is not well-investigated in aqueous environments, and thereby the preparation of PPCs using PET-RAFT polymerization needs a substantial amount of sacrificial reducing agents or inert-gas purging processes. Herein a novel water-soluble and biocompatible organic photocatalyst (PC) is reported, which enables visible-light-driven additive-free "grafting-from" polymerizations of a protein in ambient and aqueous environments. Interestingly, the developed PC shows unconventional "oxygen-acceleration" behavior for a variety of acrylic and acrylamide monomers in aqueous conditions without any additives, which are apparently distinct from previously reported systems. With such a PC, "grafting-from" polymerizations are successfully performed from protein in ambient buffer conditions under green light-emitting diode (LED) irradiation, which result in various PPCs that have neutral, anionic, cationic, and zwitterionic polyacrylates, and polyacrylamides. It is believed that this PC will be widely employed for a variety of photocatalysis processes in aqueous environments, including the living cell system.

Rational Design of Photocatalysts for Controlled Polymerization: Effect of Structures on Photocatalytic Activities

Over the past decade, the use of photocatalysts (PCs) in controlled polymerization has brought new opportunities in sophisticated macromolecular synthesis. However, the selection of PCs in these systems has been typically based on laborious trial-and-error strategies. To tackle this limitation, computer-guided rational design of PCs based on knowledge of structure-property-performance relationships has emerged. These rational strategies provide rapid and economic methodologies for tuning the performance and functionality of a polymerization system, thus providing further opportunities for polymer science. This review provides an overview of PCs employed in photocontrolled polymerization systems and summarizes their progression from early systems to the current state-of-the-art. Background theories on electronic transitions are also introduced to establish the structure-property-performance relationships from a perspective of quantum chemistry. Typical examples for each type of structure-property relationships are then presented to enlighten future design of PCs for photocontrolled polymerization.

Development of High Throughput Photopolymerizations Using Micron-Sized Ultrathin Metal-Organic Framework Nanosheets

Polymer syntheses in a high throughput format are still challenging due to the tedious procedures for prior deoxygenation and catalyst removal. Two-dimensional (2D) metal-organic framework (MOF) nanosheets are advantageous for elevating the catalytic efficiency and catalyst recyclability. Polymerization of a wide variety of monomers, including hydrophilic acrylamides and hydrophobic acrylates, was attempted directly in a multi-well plate by employing Zn-ZnPPF-2D nanosheets (PPF = porphyrin paddlewheel framework) as a heterogeneous photocatalyst. Various parameters such as monomer concentration, catalyst concentration and light wavelength were investigated with respect to their effects on polymerization rate and the degree of control over the molecular weight and molecular weight distribution. Due to the larger surface area and more accessible catalytic sites, the top-performing Zn-ZnPPF-2D exhibited fast polymerization kinetics over the Zn-ZnPPF-3D bulk crystals. In addition, the synthesis of triblock copolymers with a single loading of catalysts confirmed the outstanding catalytic performance of these 2D MOF catalysts. Finally, PET-RAFT polymerization was demonstrated to be achievable entirely in a microliter-scale human cell culture medium. As such, this strategy provides high levels of control and precision over macromolecular synthesis outcomes that best align with the requirements of high throughput approaches towards biological applications. This article is protected by copyright. All rights reserved.

Organic dyes supported on silicon-based materials: synthesis and applications as photocatalysts

The most important advance in photocatalysis in the last decade has been the synthesis and application of organic compounds to promote this process.

Aqueous Protein-Polymer Bioconjugation via Photoinduced RAFT Polymerization Using High Loading Heterogeneous Catalyst

Light-driven polymerization, such as photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization, enables biological benign conditions and versatile functional polymer structure design, which is readily used in protein-polymer bioconjugates. However, conventional metalloporphyrinic homogeneous catalysts for PET-RAFT polymerization suffer from limited aqueous solubility and tedious purification. Here we demonstrate the design of PET-RAFT photocatalyst from the reticular assembled Zr-porphyrinic metal-organic frameworks (MOFs), along with a biomacromolecule-based chain transfer agent, as efficient bioconjugation tools in water. Our methodology offers manufacturing advantages on bioconjugates under mild conditions such that MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) and cytotoxicity assays have shown the preservation of the protein integrity, bioactivity, and high cell viability after PET-RAFT polymerization. We find that the fast kinetics are benefiting from the ultrahigh loading of metalloporphyrins in MOF-525-Zn. This heterogeneous catalyst also allows us to maintain living characteristics to incorporate myriads of monomers into block copolymers. Other advantages like easy postreaction purification, reusability, and high oxygen tolerance even in an open system are demonstrated. This study provides a tool of highly efficient heterogeneous photocatalysts for polymer-protein bioconjugation in aqueous media and paves the road for biological applications.

High-Throughput Routes to Biomaterials Discovery

Many existing clinical treatments are limited in their ability to completely restore decreased or lost tissue and organ function, an unenviable situation only further exacerbated by a globally aging population. As a result, the demand for new medical interventions has increased substantially over the past 20 years, with the burgeoning fields of gene therapy, tissue engineering, and regenerative medicine showing promise to offer solutions for full repair or replacement of damaged or aging tissues. Success in these fields, however, inherently relies on biomaterials that are engendered with the ability to provide the necessary biological cues mimicking native extracellular matrixes that support cell fate. Accelerating the development of such "directive" biomaterials requires a shift in current design practices toward those that enable rapid synthesis and characterization of polymeric materials and the coupling of these processes with techniques that enable similarly rapid quantification and optimization of the interactions between these new material systems and target cells and tissues. This manuscript reviews recent advances in combinatorial and high-throughput (HT) technologies applied to polymeric biomaterial synthesis, fabrication, and chemical, physical, and biological screening with targeted end-point applications in the fields of gene therapy, tissue engineering, and regenerative medicine. Limitations of, and future opportunities for, the further application of these research tools and methodologies are also discussed.

Self-assembly of protein-polymer conjugates for drug delivery

Protein-polymer conjugates are a class of molecules that combine the stability of polymers with the diversity, specificity, and functionality of biomolecules. These bioconjugates can result in hybrid materials that display properties not found in their individual components and can be particularly relevant for drug delivery applications. Engineering amphiphilicity into these bioconjugate materials can lead to phase separation and the assembly of high-order structures. The assembly, termed self-assembly, of these hierarchical structures entails multiple levels of organization: at each level, new properties emerge, which are, in turn, influenced by lower levels. Here, we provide a critical review of protein-polymer conjugate self-assembly and how these materials can be used for therapeutic applications and drug delivery. In addition, we discuss central bioconjugate design questions and propose future perspectives for the field of protein-polymer conjugate self-assembly.

Polymers via Reversible Addition-Fragmentation Chain Transfer Polymerization with High Thiol End-Group Fidelity for Effective Grafting-To Gold Nanoparticles

End-group fidelity is the most important property for end-functional polymers. Compared to other controlled living polymerization methods, reversible addition-fragmentation chain transfer (RAFT) polymerization often yields polymers with a lower end-group fidelity, which greatly affects their applications. Herein, we report a staged-thermal-initiation RAFT polymerization for the synthesis of polymers with high thiol end-group fidelity and their high efficiencies for grafting to various gold nanoparticles (GNPs). We experimentally prove that the decrease of end-group fidelity with their molecular weight is caused by the gradual decomposition of the initiator rather than the degradation of chain-transfer agents. We show that the staged-thermal-initiation RAFT polymerization is more effective for synthesis of polymers with high thiol end-group fidelity. The grafting-to assays for various GNPs illustrate the positive correlation between the end-group fidelity of polymers and grafting-to efficiency. This work highlights the prospects for synthesis of high end-group fidelity polymers and their application in the preparation of nanoparticles-polymer hybrid materials.

New Light in Polymer Science: Photoinduced Reversible Addition-Fragmentation Chain Transfer Polymerization (PET-RAFT) as Innovative Strategy for the Synthesis of Advanced Materials

Photochemistry has attracted great interest in the last decades in the field of polymer and material science for the synthesis of innovative materials. The merging of photochemistry and reversible-deactivation radical polymerizations (RDRP) provides good reaction control and can simplify elaborate reaction protocols. These advantages open the doors to multidisciplinary fields going from composite materials to bio-applications. Photoinduced Electron/Energy Transfer Reversible Addition-Fragmentation Chain-Transfer (PET-RAFT) polymerization, proposed for the first time in 2014, presents significant advantages compared to other photochemical techniques in terms of applicability, cost, and sustainability. This review has the aim of providing to the readers the basic knowledge of PET-RAFT polymerization and explores the new possibilities that this innovative technique offers in terms of industrial applications, new materials production, and green conditions.

Reversible Deactivation Radical Polymerization: From Polymer Network Synthesis to 3D Printing

3D printing has changed the fabrication of advanced materials as it can provide customized and on-demand 3D networks. However, 3D printing of polymer materials with the capacity to be transformed after printing remains a great challenge for engineers, material, and polymer scientists. Radical polymerization has been conventionally used in photopolymerization-based 3D printing, as in the broader context of crosslinked polymer networks. Although this reaction pathway has shown great promise, it offers limited control over chain growth, chain architecture, and thus the final properties of the polymer networks. More fundamentally, radical polymerization produces dead polymer chains incapable of postpolymerization transformations. Alternatively, the application of reversible deactivation radical polymerization (RDRP) to polymer networks allows the tuning of network homogeneity and more importantly, enables the production of advanced materials containing dormant reactivatable species that can be used for subsequent processes in a postsynthetic stage. Consequently, the opportunities that (photoactivated) RDRP-based networks offer have been leveraged through the novel concepts of structurally tailored and engineered macromolecular gels, living additive manufacturing and photoexpandable/transformable-polymer networks. Herein, the advantages of RDRP-based networks over irreversibly formed conventional networks are discussed.

Thiol ligand capped quantum dot as an efficient and oxygen tolerance photoinitiator for aqueous phase radical polymerization and 3D printing under visible light

We report here a rapid visible-light-induced radical polymerization in aqueous media photoinitiated by only ppm level thiol ligand capped cadmium selenide quantum dots. The photoinitiation system could be readily employed for photo 3D printing.

Antifouling Surfaces Enabled by Surface Grafting of Highly Hydrophilic Sulfoxide Polymer Brushes

Antifouling surfaces are important in a broad range of applications. An effective approach to antifouling surfaces is to covalently attach antifouling polymer brushes. This work reports the synthesis of a new class of antifouling polymer brushes based on highly hydrophilic sulfoxide polymers by surface-initiated photoinduced electron/energy transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization. The sulfoxide polymer brushes are able to effectively reduce nonspecific adsorption of proteins and cells, demonstrating remarkable antifouling properties. Given the outstanding antifouling behavior of the sulfoxide polymers and versatility of surface-initiated PET-RAFT technology, this work presents a useful and general approach to engineering various material surfaces with antifouling properties, for potential biomedical applications in areas such as tissue engineering, medical implants, and regenerative medicine.

Biomolecular Densely Grafted Brush Polymers: Oligonucleotides, Oligosaccharides and Oligopeptides

In this Minireview, we describe synthetic polymers densely functionalized with sequence-defined biomolecular sidechains. We focus on synthetic brush polymers of oligonucleotides, oligosaccharides, and oligopeptides, prepared via graft-through polymerization from biomolecule functionalized monomers. The resulting structures are brush polymers wherein a biomolecular graft is positioned at each monomer backbone unit. We describe key synthetic milestones, identify synthetic opportunities, and highlight recent advances in the field, including biological applications.

Progress and Perspectives Beyond Traditional RAFT Polymerization

The development of advanced materials based on well-defined polymeric architectures is proving to be a highly prosperous research direction across both industry and academia. Controlled radical polymerization techniques are receiving unprecedented attention, with reversible-deactivation chain growth procedures now routinely leveraged to prepare exquisitely precise polymer products. Reversible addition-fragmentation chain transfer (RAFT) polymerization is a powerful protocol within this domain, where the unique chemistry of thiocarbonylthio (TCT) compounds can be harnessed to control radical chain growth of vinyl polymers. With the intense recent focus on RAFT, new strategies for initiation and external control have emerged that are paving the way for preparing well-defined polymers for demanding applications. In this work, the cutting-edge innovations in RAFT that are opening up this technique to a broader suite of materials researchers are explored. Emerging strategies for activating TCTs are surveyed, which are providing access into traditionally challenging environments for reversible-deactivation radical polymerization. The latest advances and future perspectives in applying RAFT-derived polymers are also shared, with the goal to convey the rich potential of RAFT for an ever-expanding range of high-performance applications.

Proteins Conjugated with Sulfoxide-Containing Polymers Show Reduced Macrophage Cellular Uptake and Improved Pharmacokinetics

The conjugation of hydrophilic polymers to proteins is an effective approach to prolonging their circulation time in the bloodstream and, hence, improving their delivery to the target region of interest. In this work, we report the synthesis of protein-polymer conjugates using a highly water-soluble sulfoxide-containing polymer, poly(2-(methylsulfinyl)ethyl acrylate) (PMSEA), through a combination of "grafting-to" and "grafting-from" methods. Oligomeric MSEA was synthesized by conventional reversible addition-fragmentation chain transfer (RAFT) polymerization and subsequently conjugated to lysozyme to produce a macromolecular chain transfer agent. This was followed by a visible light-mediated chain extension polymerization of MSEA to obtain a lysozyme-PMSEA conjugate (Lyz-PMSEA). It was found that the Lyz-PMSEA conjugate exhibited much reduced macrophage cellular uptake compared with unmodified and PEGylated lysozyme. Moreover, the Lyz-PMSEA conjugate was able to circulate longer in the bloodstream, demonstrating significantly improved pharmacokinetics demanded for pharmaceutical applications.

Enlightening advances in polymer bioconjugate chemistry: light-based techniques for grafting to and from biomacromolecules

Photochemistry has revolutionized the field of polymer-biomacromolecule conjugation. Ligation reactions necessitate biologically benign conditions, and photons have a significant energy advantage over what is available thermally at ambient temperature, allowing for rapid and unique reactivity. Photochemical reactions also afford many degrees of control, specifically, spatio-temporal control, light source tunability, and increased oxygen tolerance. Light-initiated polymerizations, in particular photo-atom-transfer radical polymerization (photo-ATRP) and photoinduced electron/energy transfer reversible addition-fragmentation chain transfer polymerization (PET-RAFT), have been used for grafting from proteins, DNA, and cells. Additionally, the spatio-temporal control inherent to light-mediated chemistry has been utilized for grafting biomolecules to hydrogel networks for many applications, such as 3-D cell culture. While photopolymerization has clear advantages, there are factors that require careful consideration in order to obtain optimal control. These factors include the photocatalyst system, light intensity, and wavelength. This Perspective aims to discuss recent advances of photochemistry for polymer biomacromolecule conjugation and potential considerations while tailoring these systems.

Recent trends in nanopore polymer functionalization

Functional nanopores play an essential role in many biotechnological applications such as sensing, or drug delivery. Prominent examples are polymer functionalized ceramic or solid state nanopores. Intensive research efforts led to a discovery of a plethora of polymer functionalized nanopores demonstrating gated molecular transport upon basically all common stimuli. Nevertheless, nature's biological pore transport precision is unreached. This can be, among others, ascribed to limits in design precision especially with respect to functionalization. Recent trends in polymer functionalized nanopores address the role of confinement and polymerization control, strategies toward more sustainable reaction conditions, such as visible light initiation and strategies toward nanoscale local placement of polymer functionalization. The resulting multi-stimuli responsive nanopore performance enables concerted release or transport, side selective separation and selective detection.

Protein-polymer bioconjugates via a versatile oxygen tolerant photoinduced controlled radical polymerization approach

The immense application potential of amphiphilic protein-polymer conjugates remains largely unexplored, as established "grafting from" synthetic protocols involve time-consuming, harsh and disruptive deoxygenation methods, while "grafting to" approaches result in low yields. Here we report an oxygen tolerant, photoinduced CRP approach which readily affords quantitative yields of protein-polymer conjugates within 2 h, avoiding damage to the secondary structure of the protein and providing easily accessible means to produce biomacromolecular assemblies. Importantly, our methodology is compatible with multiple proteins (e.g. BSA, HSA, GOx, beta-galactosidase) and monomer classes including acrylates, methacrylates, styrenics and acrylamides. The polymerizations are conveniently conducted in plastic syringes and in the absence of any additives or external deoxygenation procedures using low-organic content media and ppm levels of copper. The robustness of the protocol is further exemplified by its implementation under UV, blue light or even sunlight irradiation as well as in buffer, nanopure, tap or even sea water.