Synthesis of Polymer Bioconjugates via Photoinduced Atom Transfer Radical Polymerization under Blue Light Irradiation

Nucleic Acid-Binding Dyes as Versatile Photocatalysts for Atom-Transfer Radical Polymerization

Nucleic acid-binding dyes (NuABDs) are fluorogenic probes that light up after binding to nucleic acids. Taking advantage of their fluorogenicity, NuABDs have been widely utilized in the fields of nanotechnology and biotechnology for diagnostic and analytical applications. We demonstrate the potential of NuABDs together with an appropriate nucleic acid scaffold as an intriguing photocatalyst for precisely controlled atom-transfer radical polymerization (ATRP). Additionally, we systematically investigated the thermodynamic and electrochemical properties of the dyes, providing insights into the mechanism that drives the photopolymerization. The versatility of the NuABD-based platform was also demonstrated through successful polymerizations using several NuABDs in conjunction with diverse nucleic acid scaffolds, such as G-quadruplex DNA or DNA nanoflowers. This study not only extends the horizons of controlled photopolymerization but also broadens opportunities for nucleic acid-based materials and technologies, including nucleic acid-polymer biohybrids and stimuli-responsive ATRP platforms.

Tailored Branched Polymer-Protein Bioconjugates for Tunable Sieving Performance

Protein-polymer conjugates combine the unique properties of both proteins and synthetic polymers, making them important materials for biomedical applications. In this work, we synthesized and characterized protein-branched polymer bioconjugates that were precisely designed to retain protein functionality while preventing unwanted interactions. Using chymotrypsin as a model protein, we employed a controlled radical branching polymerization (CRBP) technique utilizing a water-soluble inibramer, sodium 2-bromoacrylate. The green-light-induced atom transfer radical polymerization (ATRP) enabled the grafting of branched polymers directly from the protein surface in the open air. The resulting bioconjugates exhibited a predetermined molecular weight, well-defined architecture, and high branching density. Conformational analysis by SEC-MALS validated the controlled grafting of branched polymers. Furthermore, enzymatic assays revealed that densely grafted polymers prevented protein inhibitor penetration, and the resulting conjugates retained up to 90% of their enzymatic activity. This study demonstrates a promising strategy for designing protein-polymer bioconjugates with tunable sieving behavior, opening avenues for applications in drug delivery and biotechnology.

Thermoresponsive Coiled-Coil Peptide-Polymer Grafts

Alkyl halide side groups are selectively incorporated into monodispersed, computationally designed coiled-coil-forming peptide nanoparticles. Poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) is polymerized from the coiled-coil periphery using photoinitiated atom transfer radical polymerization (photoATRP) to synthesize well-defined, thermoresponsive star copolymer architectures. This facile synthetic route is readily extended to other monomers for a range of new complex star-polymer macromolecules.

Highly Sensitive Detection of Bacteria by Binder-Coupled Multifunctional Polymeric Dyes

Infectious diseases caused by pathogens are a health burden, but traditional pathogen identification methods are complex and time-consuming. In this work, we have developed well-defined, multifunctional copolymers with rhodamine B dye synthesized by atom transfer radical polymerization (ATRP) using fully oxygen-tolerant photoredox/copper dual catalysis. ATRP enabled the efficient synthesis of copolymers with multiple fluorescent dyes from a biotin-functionalized initiator. Biotinylated dye copolymers were conjugated to antibody (Ab) or cell-wall binding domain (CBD), resulting in a highly fluorescent polymeric dye-binder complex. We showed that the unique combination of multifunctional polymeric dyes and strain-specific Ab or CBD exhibited both enhanced fluorescence and target selectivity for bioimaging of Staphylococcus aureus by flow cytometry and confocal microscopy. The ATRP-derived polymeric dyes have the potential as biosensors for the detection of target DNA, protein, or bacteria, as well as bioimaging.

Fully Oxygen-Tolerant Visible-Light-Induced ATRP of Acrylates in Water: Toward Synthesis of Protein-Polymer Hybrids

Over the last decade, photoinduced ATRP techniques have been developed to harness the energy of light to generate radicals. Most of these methods require the use of UV light to initiate polymerization. However, UV light has several disadvantages: it can degrade proteins, damage DNA, cause undesirable side reactions, and has low penetration depth in reaction media. Recently, we demonstrated green-light-induced ATRP with dual catalysis, where eosin Y (EYH₂) was used as an organic photoredox catalyst in conjunction with a copper complex. This dual catalysis proved to be highly efficient, allowing rapid and well-controlled aqueous polymerization of oligo(ethylene oxide) methyl ether methacrylate without the need for deoxygenation. Herein, we expanded this system to synthesize polyacrylates under biologically relevant conditions using Cu^II/Me₆TREN (Me₆TREN = tris[2-(dimethylamino)ethyl]amine) and EYH₂ at ppm levels. Water-soluble oligo(ethylene oxide) methyl ether acrylate (average M _n = 480, OEOA₄₈₀) was polymerized in open reaction vessels under green light irradiation (520 nm). Despite continuous oxygen diffusion, high monomer conversions were achieved within 40 min, yielding polymers with narrow molecular weight distributions (1.17 ≤ D̵ ≤ 1.23) for a wide targeted DP range (50-800). In situ chain extension and block copolymerization confirmed the preserved chain end functionality. In addition, polymerization was triggered/halted by turning on/off a green light, showing temporal control. The optimized conditions also enabled controlled polymerization of various hydrophilic acrylate monomers, such as 2-hydroxyethyl acrylate, 2-(methylsulfinyl)ethyl acrylate), and zwitterionic carboxy betaine acrylate. Notably, the method allowed the synthesis of well-defined acrylate-based protein-polymer hybrids using a straightforward reaction setup without rigorous deoxygenation.

Recent Advances in the Application of ATRP in the Synthesis of Drug Delivery Systems

Advances in atom transfer radical polymerization (ATRP) have enabled the precise design and preparation of nanostructured polymeric materials for a variety of biomedical applications. This paper briefly summarizes recent developments in the synthesis of bio-therapeutics for drug delivery based on linear and branched block copolymers and bioconjugates using ATRP, which have been tested in drug delivery systems (DDSs) over the past decade. An important trend is the rapid development of a number of smart DDSs that can release bioactive materials in response to certain external stimuli, either physical (e.g., light, ultrasound, or temperature) or chemical factors (e.g., changes in pH values and/or environmental redox potential). The use of ATRPs in the synthesis of polymeric bioconjugates containing drugs, proteins, and nucleic acids, as well as systems applied in combination therapies, has also received considerable attention.

Polymer Grafting and its chemical reactions

Polymer grafting is a technique to improve the morphology, chemical, and physical properties of the polymer. This technique has the potential to improve the existing conduction and properties of polymers other than charge transport; as a result, it enhances the solubility, nano-dimensional morphology, biocompatibility, bio-communication, and other property of parent polymer. A polymer's physicochemical properties can be modified even further by creating a copolymer with another polymer or by grafting. Here in the various chemical approaches for polymer grafting, like free radical, click reaction, amide formation, and alkylation have been discussed with their importance, moreover the process and its importance are covered comprehensively with their scientific explanation. The present review also covers the effectiveness of the graft-to approaches and its application in various fields, which will give reader a glimpse about polymer grafting and its uses.

Rapid Oxygen-Tolerant Synthesis of Protein-Polymer Bioconjugates via Aqueous Copper-Mediated Polymerization

The synthesis of protein-polymer conjugates usually requires extensive and costly deoxygenation procedures, thus limiting their availability and potential applications. In this work, we report the ultrafast synthesis of polymer-protein bioconjugates in the absence of any external deoxygenation via an aqueous copper-mediated methodology. Within 10 min and in the absence of any external stimulus such as light (which may limit the monomer scope and/or disrupt the secondary structure of the protein), a range of hydrophobic and hydrophilic monomers could be successfully grafted from a BSA macroinitiator, yielding well-defined polymer-protein bioconjugates at quantitative yields. Our approach is compatible with a wide range of monomer classes such as (meth) acrylates, styrene, and acrylamides as well as multiple macroinitiators including BSA, BSA nanoparticles, and beta-galactosidase from Aspergillus oryzae. Notably, the synthesis of challenging protein-polymer-polymer triblock copolymers was also demonstrated, thus significantly expanding the scope of our strategy. Importantly, both lower and higher scale polymerizations (from 0.2 to 35 mL) were possible without compromising the overall efficiency and the final yields. This simple methodology paves the way for a plethora of applications in aqueous solutions without the need of external stimuli or tedious deoxygenation.

Toward Green Atom Transfer Radical Polymerization: Current Status and Future Challenges

Reversible-deactivation radical polymerizations (RDRPs) have revolutionized synthetic polymer chemistry. Nowadays, RDRPs facilitate design and preparation of materials with controlled architecture, composition, and functionality. Atom transfer radical polymerization (ATRP) has evolved beyond traditional polymer field, enabling synthesis of organic-inorganic hybrids, bioconjugates, advanced polymers for electronics, energy, and environmentally relevant polymeric materials for broad applications in various fields. This review focuses on the relation between ATRP technology and the 12 principles of green chemistry, which are paramount guidelines in sustainable research and implementation. The green features of ATRP are presented, discussing the environmental and/or health issues and the challenges that remain to be overcome. Key discoveries and recent developments in green ATRP are highlighted, while providing a perspective for future opportunities in this area.

Enzyme Catalysis for Reversible Deactivation Radical Polymerization

Enzyme catalysis has been increasingly utilized in reversible deactivation radical polymerization (Enz-RDRP) on account of its mildness, efficiency, and sustainability. In this Minireview we discuss the key roles enzymes play in RDRP, including their ATRPase, initiase, deoxygenation, and photoenzyme activities. We use selected examples to highlight applications of Enz-RDRP in surface brush fabrication, sensing, polymerization-induced self-assembly, and high-throughput synthesis. We also give our reflections on the challenges and future directions of this emerging area.

Photoinduced Controlled/Living Polymerizations

The application of photochemistry in polymer synthesis is of interest due to the unique possibilities offered compared to thermochemistry, including topological and temporal control, rapid polymerization, sustainable low-energy processes, and environmentally benign features leading to established and emerging applications in adhesives, coatings, adaptive manufacturing, etc. In particular, the utilization of photochemistry in controlled/living polymerizations often offers the capability for precise control over the macromolecular structure and chain length in addition to the associated advantages of photochemistry. Herein, the latest developments in photocontrolled living radical and cationic polymerizations and their combinations for application in polymer syntheses are discussed. This Review summarizes and highlights recent studies in the emerging area of photoinduced controlled/living polymerizations. A discussion of mechanistic details highlights differences as well as parallels between different systems for different polymerization methods and monomer applicability.

Controlled Release of Exosomes Using Atom Transfer Radical Polymerization-Based Hydrogels

Exosomes are 30-200 nm sized extracellular vesicles that are increasingly recognized as potential drug delivery vehicles. However, exogenous exosomes are rapidly cleared from the blood upon intravenous delivery, which limits their therapeutic potential. Here, we report bioactive exosome-tethered poly(ethylene oxide)-based hydrogels for the localized delivery of therapeutic exosomes. Using cholesterol-modified DNA tethers, the lipid membrane of exosomes was functionalized with initiators to graft polymers in the presence of additional initiators and crosslinker using photoinduced atom transfer radical polymerization (ATRP). This strategy of tethering exosomes within the hydrogel network allowed their controlled release over a period of 1 month, which was much longer than physically entrapped exosomes. Exosome release profile was tuned by varying the crosslinking density of the polymer network and the use of photocleavable tethers allowed stimuli-responsive release of exosomes. The therapeutic potential of the hydrogels was assessed by evaluating the osteogenic potential of bone morphogenetic protein 2-loaded exosomes on C2C12 and MC3T3-E1 cells. Thus, ATRP-based exosome-tethered hydrogels represent a tunable platform with improved efficacy and an extended-release profile.

Functional DNA-Polymer Conjugates

DNA nanotechnology has seen large developments over the last 30 years through the combination of solid phase synthesis and the discovery of DNA nanostructures. Solid phase synthesis has facilitated the availability of short DNA sequences and the expansion of the DNA toolbox to increase the chemical functionalities afforded on DNA, which in turn enabled the conception and synthesis of sophisticated and complex 2D and 3D nanostructures. In parallel, polymer science has developed several polymerization approaches to build di- and triblock copolymers bearing hydrophilic, hydrophobic, and amphiphilic properties. By bringing together these two emerging technologies, complementary properties of both materials have been explored; for example, the synthesis of amphiphilic DNA-polymer conjugates has enabled the production of several nanostructures, such as spherical and rod-like micelles. Through both the DNA and polymer parts, stimuli-responsiveness can be instilled. Nanostructures have consequently been developed with responsive structural changes to physical properties, such as pH and temperature, as well as short DNA through competitive complementary binding. These responsive changes have enabled the application of DNA-polymer conjugates in biomedical applications including drug delivery. This review discusses the progress of DNA-polymer conjugates, exploring the synthetic routes and state-of-the-art applications afforded through the combination of nucleic acids and synthetic polymers.

Orthogonal Images Concealed Within a Responsive 6-Dimensional Hypersurface

A photochemical printer, equipped with a digital micromirror device (DMD), leads to the rapid elucidation of the kinetics of the surface-initiated atom-transfer radical photopolymerization of N,N-dimethylacrylamide (DMA) and N-isopropylacrylamide (NIPAM) monomers. This effort reveals conditions where polymer brushes of identical heights can be grown from each monomer. With these data, hidden images are created that appear upon heating the substrate above the lower critical solution temperature (LCST) of polyNIPAM. By introducing a third monomer, methacryloxyethyl thiocarbamoyl rhodamine B, a second, orthogonal image appears upon UV-irradiation. With these studies, it is shown how a new photochemical printer accelerates discovery, creates arbitrary patterns, and addresses long-standing problems in brush polymer and surface chemistry. With this technology in hand a new method is demonstrated to encrypt data within hypersurfaces.

Making ATRP More Practical: Oxygen Tolerance

Atom-transfer radical polymerization (ATRP) is a well-known technique for the controlled polymerization of vinyl monomers under mild conditions. However, as with any other radical polymerization, ATRP typically requires rigorous oxygen exclusion, making it time-consuming and challenging to use by nonexperts. In this Account, we discuss various approaches to achieving oxygen tolerance in ATRP, presenting the overall progress in the field.Copper-mediated ATRP, which we first discovered in the late 1990s, uses a Cu^I/L activator that reversibly reacts with the dormant C(sp³)-X polymer chain end, forming a X-Cu^II/L deactivator and a propagating radical. Oxygen interferes with activation and chain propagation by quenching the radicals and oxidizing the activator. At ATRP equilibrium, the activator is present at a much higher concentration than the propagating radicals. Thus, oxidation of the activator is the dominant inhibition pathway. In conventional ATRP, this reaction is irreversible, so oxygen must be strictly excluded to achieve good results.Over the last two decades, our group has developed several ATRP techniques based on the concept of regenerating the activator. When the oxidized activator is continuously converted back to its active reduced form, then the catalytic system itself can act as an oxygen scavenger. Regeneration can be accomplished by reducing agents and photo-, electro-, and mechanochemical stimuli. This family of methods offers a degree of oxygen tolerance, but most of them can tolerate only a limited amount of oxygen and do not allow polymerization in an open vessel.More recently, we discovered that enzymes can be used in auxiliary catalytic systems that directly deoxygenate the reaction medium and protect the polymerization process. We developed a method that uses glucose oxidase (GOx), glucose, and sodium pyruvate to very effectively scavenge oxygen and enable open-vessel ATRP. By adding a second enzyme, horseradish peroxidase (HPR), we managed to extend the role of the auxiliary enzymatic system to generating carbon-based radicals and changed ATRP from an oxygen-sensitive to an oxygen-fueled reaction.While performing control experiments for the enzymatic methods, we noticed that using sodium pyruvate under UV irradiation triggers polymerization without the presence of GOx. This serendipitous discovery allowed us to develop the first oxygen-proof, small-molecule-based, photoinduced ATRP system. It has oxygen tolerance similar to that of the enzymatic methods, exhibits superior compatibility with both aqueous media and organic solvents, and avoids problems associated with purifying polymers from enzymes. The system was able to rapidly polymerize N-isopropylacrylamide, a challenging monomer, with a high degree of control.These contributions have substantially simplified the use of ATRP, making it more practical and accessible to everyone.

Engineering exosome polymer hybrids by atom transfer radical polymerization

Exosomes are emerging as ideal drug delivery vehicles due to their biological origin and ability to transfer cargo between cells. However, rapid clearance of exogenous exosomes from the circulation as well as aggregation of exosomes and shedding of surface proteins during storage limit their clinical translation. Here, we demonstrate highly controlled and reversible functionalization of exosome surfaces with well-defined polymers that modulate the exosome's physiochemical and pharmacokinetic properties. Using cholesterol-modified DNA tethers and complementary DNA block copolymers, exosome surfaces were engineered with different biocompatible polymers. Additionally, polymers were directly grafted from the exosome surface using biocompatible photo-mediated atom transfer radical polymerization (ATRP). These exosome polymer hybrids (EPHs) exhibited enhanced stability under various storage conditions and in the presence of proteolytic enzymes. Tuning of the polymer length and surface loading allowed precise control over exosome surface interactions, cellular uptake, and preserved bioactivity. EPHs show fourfold higher blood circulation time without altering tissue distribution profiles. Our results highlight the potential of precise nanoengineering of exosomes toward developing advanced drug and therapeutic delivery systems using modern ATRP methods.

Evolution and applications of polymer brush hypersurface photolithography

Hypersurface photolithography creates arbitrary polymer brush patterns with independent control over feature diameter, height, and spacing between features, while controlling composition along a polymer chain and between features.

Combination of DNA with polymers

The preparation and applications of DNA containing polymers are comprehensively reviewed, and they are in the form of DNA−polymer covalent conjugators, supramolecular assemblies and hydrogels for advanced materials with promising features.

DNA-Polymer Nanostructures by RAFT Polymerization and Polymerization-Induced Self-Assembly

Nanostructures derived from amphiphilic DNA-polymer conjugates have emerged prominently due to their rich self-assembly behavior; however, their synthesis is traditionally challenging. Here, we report a novel platform technology towards DNA-polymer nanostructures of various shapes by leveraging polymerization-induced self-assembly (PISA) for polymerization from single-stranded DNA (ssDNA). A "grafting from" protocol for thermal RAFT polymerization from ssDNA under ambient conditions was developed and utilized for the synthesis of functional DNA-polymer conjugates and DNA-diblock conjugates derived from acrylates and acrylamides. Using this method, PISA was applied to manufacture isotropic and anisotropic DNA-polymer nanostructures by varying the chain length of the polymer block. The resulting nanostructures were further functionalized by hybridization with a dye-labelled complementary ssDNA, thus establishing PISA as a powerful route towards intrinsically functional DNA-polymer nanostructures.

Fully oxygen-tolerant atom transfer radical polymerization triggered by sodium pyruvate

ATRP (atom transfer radical polymerization) is one of the most robust reversible deactivation radical polymerization (RDRP) systems. However, the limited oxygen tolerance of conventional ATRP impedes its practical use in an ambient atmosphere. In this work, we developed a fully oxygen-tolerant PICAR (photoinduced initiators for continuous activator regeneration) ATRP process occurring in both water and organic solvents in an open reaction vessel. Continuous regeneration of the oxidized form of the copper catalyst with sodium pyruvate through UV excitation allowed the chemical removal of oxygen from the reaction mixture while maintaining a well-controlled polymerization of N-isopropylacrylamide (NIPAM) or methyl acrylate (MA) monomers. The polymerizations of NIPAM were conducted with 250 ppm (with respect to the monomer) or lower concentrations of CuBr2 and a tris[2-(dimethylamino)ethyl]amine ligand. The polymers were synthesized to nearly quantitative monomer conversions (>99%), high molecular weights (M n > 270 000), and low dispersities (1.16 < Đ < 1.44) in less than 30 min under biologically relevant conditions. The reported method provided a well-controlled ATRP (Đ = 1.16) of MA in dimethyl sulfoxide despite oxygen diffusion from the atmosphere into the reaction system.

Hydrophobic Interaction: A Promising Driving Force for the Biomedical Applications of Nucleic Acids

The comprehensive understanding and proper use of supramolecular interactions have become critical for the development of functional materials, and so is the biomedical application of nucleic acids (NAs). Relatively rare attention has been paid to hydrophobic interaction compared with hydrogen bonding and electrostatic interaction of NAs. However, hydrophobic interaction shows some unique properties, such as high tunability for application interest, minimal effect on NA functionality, and sensitivity to external stimuli. Therefore, the widespread use of hydrophobic interaction has promoted the evolution of NA-based biomaterials in higher-order self-assembly, drug/gene-delivery systems, and stimuli-responsive systems. Herein, the recent progress of NA-based biomaterials whose fabrications or properties are highly determined by hydrophobic interactions is summarized. 1) The hydrophobic interaction of NA itself comes from the accumulation of base-stacking forces, by which the NAs with certain base compositions and chain lengths show properties similar to thermal-responsive polymers. 2) In conjugation with hydrophobic molecules, NA amphiphiles show interesting self-assembly structures with unique properties in many new biosensing and therapeutic strategies. 3) The working-mechanisms of some NA-based complex materials are also dependent on hydrophobic interactions. Moreover, in recent attempts, NA amphiphiles have been applied in organizing macroscopic self-assembly of DNA origami and controlling the cell-cell interactions.

p-Substituted Tris(2-pyridylmethyl)amines as Ligands for Highly Active ATRP Catalysts: Facile Synthesis and Characterization

A facile and efficient two-step synthesis of p-substituted tris(2-pyridylmethyl)amine (TPMA) ligands to form Cu complexes with the highest activity to date in atom transfer radical polymerization (ATRP) is presented. In the divergent synthesis, p-Cl substituents in tris(4-chloro-2-pyridylmethyl)amine (TPMA^3Cl ) were replaced in one step and high yield by electron-donating cyclic amines (pyrrolidine (TPMA^PYR ), piperidine (TPMA^PIP ), and morpholine (TPMA^MOR )) by nucleophilic aromatic substitution. The [Cu^II (TPMA^NR2 )Br]⁺ complexes exhibited larger energy gaps between frontier molecular orbitals and >0.2 V more negative reduction potentials than [Cu^II (TPMA)Br]⁺ , indicating >3 orders of magnitude higher ATRP activity. [Cu^I (TPMA^PYR )]⁺ exhibited the highest reported activity for Br-capped acrylate chain ends in DMF, and moderate activity toward C-F bonds at room temperature. ATRP of n-butyl acrylate using only 10-25 part per million loadings of [Cu^II (TPMA^NR2 )Br]⁺ exhibited excellent control.

Catalytic Halogen Exchange in Miniemulsion ARGET ATRP: A Pathway to Well-Controlled Block Copolymers

Halogen exchange in atom transfer radical polymerization (ATRP) is an efficient way to chain-extend from a less active macroinitiator (MI) to a more active monomer. This has been previously achieved by using CuCl/L in the equimolar amount to P_n -Br MI in the chain extension step. However, this approach cannot be effectively applied in systems based on regeneration of activators (ARGET ATRP), since they operate with ppm amounts of catalysts. Herein, a catalytic halogen exchange procedure is reported using a catalytic amount of Cu in miniemulsion ARGET ATRP to chain-extend from a less active poly(n-butyl acrylate) (PBA) MI to a more active methyl methacrylate (MMA) monomer. Influence of different reagents on the initiation efficiency and dispersity is studied. Addition of 0.1 m NaCl or tetraethylammonium chloride to ATRP of MMA initiated by methyl 2-bromopropionate leads to high initiation efficiency and polymers with low dispersity. The optimized conditions are then employed in chain extension of PBA MI with MMA to prepare diblock and triblock copolymers.

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.

Oligonucleotide-Polymer Conjugates: From Molecular Basics to Practical Application

DNA exhibits many attractive properties, such as programmability, precise self-assembly, sequence-coded biomedical functions, and good biocompatibility; therefore, DNA has been used extensively as a building block to construct novel nanomaterials. Recently, studies on oligonucleotide-polymer conjugates (OPCs) have attracted increasing attention. As hybrid molecules, OPCs exhibit novel properties, e.g., sophisticated self-assembly behaviors, which are distinct from the simple combination of the functions of DNA and polymer, making OPCs interesting and useful. The synthesis and applications of OPCs are highly dependent on the choice of the polymer block, but a systematic summary of OPCs based on their molecular structures is still lacking. In order to design OPCs for further applications, it is necessary to thoroughly understand the structure-function relationship of OPCs. In this review, we carefully categorize recently developed OPCs by the structures of the polymer blocks, and discuss the synthesis, purification, and applications for each category. Finally, we will comment on future prospects for OPCs.

Preparation of Biomolecule-Polymer Conjugates by Grafting-From Using ATRP, RAFT, or ROMP

Biomolecule-polymer conjugates are constructs that take advantage of the functional or otherwise beneficial traits inherent to biomolecules and combine them with synthetic polymers possessing specially tailored properties. The rapid development of novel biomolecule-polymer conjugates based on proteins, peptides, or nucleic acids has ushered in a variety of unique materials, which exhibit functional attributes including thermo-responsiveness, exceptional stability, and specialized specificity. Key to the synthesis of new biomolecule-polymer hybrids is the use of controlled polymerization techniques coupled with either grafting-from, grafting-to, or grafting-through methodology, each of which exhibit distinct advantages and/or disadvantages. In this review, we present recent progress in the development of biomolecule-polymer conjugates with a focus on works that have detailed the use of grafting-from methods employing ATRP, RAFT, or ROMP.

Layered Co-Immobilization of β-Glucosidase and Cellulase on Polymer Film by Visible-Light-Induced Graft Polymerization

Exploring a suitable immobilization strategy to improve catalytic efficiency and reusability of cellulase is of great importance to lowering the cost and promoting the industrialization of cellulose-derived bioethanol. In this work, a layered structure with a thin PEG hydrogel as the inner layer and sodium polyacrylate (PAANa) brush as the outer layer was fabricated on low density polyethylene (LDPE) film by visible-light-induced graft polymerization. Two enzymes, β-glucosidase (BG) and cellulase, were separately coimmobilized onto this hierarchical film. As supplementary to cellulase for improving catalytic efficiency, BG was in situ entrapped into the inner PEG hydrogel layer during the graft polymerization from the LDPE surface. After graft polymerization of sodium acrylate on the PEG hydrogel layer was reinitiated, cellulase was covalently attached on the outer PAANa brush layer. Owing to the mild reaction condition (visible-light irradiation and room temperature), the immobilized BG could retain a high activity after the graft polymerization. The immobilization did not alter the optimal pH and temperature of BG or the optimal temperature of cellulase. However, the optimal pH of cellulase shifts to 5.0 after immobilization. Compared with the original activity of single cellulase system and isolated BG/cellulase immobilization system, the dual-enzyme system exhibited 82% and 20% increase in catalytic activity, respectively. The dual-enzyme system could maintain 93% of carboxymethylcellulose sodium salt (CMC) activity after repeating 10 cycles of hydrolysis and 89% of filter paper activity after 6 cycles relative to original activity, exhibiting excellent reusability. This layer coimmobilization system of BG and cellulase on the polymer film displays tremendous potential for practical application in a biorefinery.

Photochemical Reactions in the Synthesis of Protein-Drug Conjugates

The ability to modify biologically active molecules such as antibodies with drug molecules, fluorophores or radionuclides is crucial in drug discovery and target identification. Classic chemistry used for protein functionalisation relies almost exclusively on thermochemically mediated reactions. Our recent experiments have begun to explore the use of photochemistry to effect rapid and efficient protein functionalisation. This article introduces some of the principles and objectives of using photochemically activated reagents for protein ligation. The concept of simultaneous photoradiosynthesis of radiolabelled antibodies for use in molecular imaging is introduced as a working example. Notably, the goal of producing functionalised proteins in the absence of pre-association (non-covalent ligand-protein binding) introduces requirements that are distinct from the more regular use of photoactive groups in photoaffinity labelling. With this in mind, the chemistry of thirteen different classes of photoactivatable reagents that react through the formation of intermediate carbenes, electrophiles, dienes, or radicals, is assessed.

Atom Transfer Radical Polymerization for Biorelated Hybrid Materials

Proteins, nucleic acids, lipid vesicles, and carbohydrates are the major classes of biomacromolecules that function to sustain life. Biology also uses post-translation modification to increase the diversity and functionality of these materials, which has inspired attaching various other types of polymers to biomacromolecules. These polymers can be naturally (carbohydrates and biomimetic polymers) or synthetically derived and have unique properties with tunable architectures. Polymers are either grafted-to or grown-from the biomacromolecule's surface, and characteristics including polymer molar mass, grafting density, and degree of branching can be controlled by changing reaction stoichiometries. The resultant conjugated products display a chimerism of properties such as polymer-induced enhancement in stability with maintained bioactivity, and while polymers are most often conjugated to proteins, they are starting to be attached to nucleic acids and lipid membranes (cells) as well. The fundamental studies with protein-polymer conjugates have improved our synthetic approaches, characterization techniques, and understanding of structure-function relationships that will lay the groundwork for creating new conjugated biomacromolecular products which could lead to breakthroughs in genetic and tissue engineering.

Preparation of Well-Defined Polymers and DNA-Polymer Bioconjugates via Small-Volume eATRP in the Presence of Air

An aqueous electrochemically mediated atom transfer radical polymerization (eATRP) was performed in a small volume solution (75 μL) deposited on a screen-printed electrode (SPE). The reaction was open to air, thanks to the use of glucose oxidase (GOx) as an oxygen scavenger. Well-defined poly(2-(methylsulfinyl)ethyl acrylate) (PMSEA), poly(oligo(ethylene oxide) methyl ether methacrylate) (POEOMA), and corresponding DNA-polymer biohybrids were synthesized by the small-volume eATRP at room temperature. The reactions were simplified and polymerization rates increased by the application of the enzyme deoxygenating system and the compact electrochemical setup. Importantly, the volume of polymerization mixture was lowered to microliters, which not only decreases the cost for each reaction, but can also be potentially implemented in combinatorial chemistry and electrode-array configurations for high-throughput systems.