DNA-Mediated Step-Growth Polymerization of Bottlebrush Macromonomers

Surface Functionalization of Elastomers with Biopolymers

Biopolymer coatings on elastomeric surfaces have significant impact for advancements in biomedicine as they combine flexible devices with complex biological functionality. Biopolymers offer increased ability for antimicrobial coatings, sensing of relevant biological markers, and controlled drug delivery. The methodologies available to conjugate these important biopolymers to flexible elastomeric substrates are vast and rapidly evolving. This chapter aims to compile methodologies across the application space of biopolymer conjugation to elastomers. We present a guide to the field and methods ranging from surface activation and functionalization, grafting-to and grafting-from of biopolymers, and characterization of the resulting substrates.

Nucleolin-Targeting AS1411 Aptamer-Conjugated Nanospheres for Targeted Treatment of Glioblastoma

Post-operative chemotherapy is still required for the treatment of glioblastoma (GBM), for which nanocarrier-based drug delivery has been identified as one of the most effective methods. However, the blood-brain barrier (BBB) and non-specific delivery to non-tumor tissues can significantly limit drug accumulation in tumor tissues and cause damage to nearby normal tissues. This study describes a targeted cancer therapy approach that uses AS1411 aptamer-conjugated nanospheres (100-300 nm in size) loaded with doxorubicin (Dox) to selectively identify tumor cells overexpressing nucleolin (NCL) proteins. The study demonstrates that the active target model, which employs aptamer-mediated drug delivery, is more effective than non-specific enhanced permeability and maintenance (EPR)-mediated delivery and passive drug delivery in improving drug penetration and maintenance in tumor cells. Additionally, the study reveals the potential for anti-cancer effects through 3D spheroidal and in vivo GBM xenograft models. The DNA-protein hybrid nanospheres utilized in this study offer numerous benefits, such as efficient synthesis, structural stability, high drug loading, dye labeling, biocompatibility, and biodegradability. When combined with nanospheres, the 1411 aptamer has been shown to be an effective drug delivery carrier allowing for the precise targeting of tumors. This combination has the potential to produce anti-tumor effects in the active targeted therapy of GBM.

Organ/Cell-Selective Intracellular Delivery of Biologics via N-Acetylated Galactosamine-Functionalized Polydisulfide Conjugates

Biologics, including proteins and antisense oligonucleotides (ASOs), face significant challenges when it comes to achieving intracellular delivery within specific organs or cells through systemic administrations. In this study, we present a novel approach for delivering proteins and ASOs to liver cells, both in vitro and in vivo, using conjugates that tether N-acetylated galactosamine (GalNAc)-functionalized, cell-penetrating polydisulfides (PDSs). The method involves the thiol-bearing cargo-mediated ring-opening polymerization of GalNAc-functionalized lipoamide monomers through the so-called aggregation-induced polymerization, leading to the formation of site-specific protein/ASO-PDS conjugates with narrow dispersity. The hepatocyte-selective intracellular delivery of the conjugates arises from a combination of factors, including first GalNAc binding with ASGPR receptors on liver cells, leading to cell immobilization, and the subsequent thiol-disulfide exchange occurring on the cell surface, promoting internalization. Our findings emphasize the critical role of the close proximity of the PDS backbone to the cell surface, as it governs the success of thiol-disulfide exchange and, consequently, cell penetration. These conjugates hold tremendous potential in overcoming the various biological barriers encountered during systemic and cell-specific delivery of biomacromolecular cargos, opening up new avenues for the diagnosis and treatment of a range of liver-targeting diseases.

Recent progress of non-linear topological structure polymers: synthesis, and gene delivery

Currently, many types of non-linear topological structure polymers, such as brush-shaped, star, branched and dendritic structures, have captured much attention in the field of gene delivery and nanomedicine. Compared with linear polymers, non-linear topological structural polymers offer many advantages, including multiple terminal groups, broad and complicated spatial architecture and multi-functionality sites to enhance gene delivery efficiency and targeting capabilities. Nevertheless, the complexity of their synthesis process severely hampers the development and applications of nonlinear topological polymers. This review aims to highlight various synthetic approaches of non-linear topological architecture polymers, including reversible-deactivation radical polymerization (RDRP) including atom-transfer radical polymerization (ATRP), nitroxide-mediated polymerization (NMP), reversible addition-fragmentation chain transfer (RAFT) polymerization, click chemistry reactions and Michael addition, and thoroughly discuss their advantages and disadvantages, as well as analyze their further application potential. Finally, we comprehensively discuss and summarize different non-linear topological structure polymers for genetic materials delivering performance both in vitro and in vivo, which indicated that topological effects and nonlinear topologies play a crucial role in enhancing the transfection performance of polymeric vectors. This review offered a promising guideline for the design and development of novel nonlinear polymers and facilitated the development of a new generation of polymer-based gene vectors.

Supramolecular Polymerization of Polymeric Nanorods Mediated by Block Copolymers

Introducing a second component is an effective way to manipulate polymerization behavior. However, this phenomenon has rarely been observed in colloidal systems, such as polymeric nanoparticles. Here, we report the supramolecular polymerization of polymeric nanorods mediated by block copolymers. Experimental observations and simulation results illustrate that block copolymers surround the polymeric nanorods and mainly concentrate around the two ends, leaving the hydrophobic side regions exposed. These polymeric nanorods connect in a side-by-side manner through hydrophobic interactions to form bundles. As polymerization progresses, the block copolymers gradually deposit onto the bundles and finally assemble into helical nanopatterns on the outermost surface, which terminates the polymerization. It is anticipated that this work could offer inspiration for a general strategy of controllable supramolecular polymerization.

Fluorination Effects on the Drug Delivery Property of Cylindrical Polymer Brushes

Fluorination has been widely applied to improving the properties of small-molecule drugs. However, relatively little is known about the effects of fluorination on the drug delivery property of nanomaterials. In this paper, we synthesized a fluoroalkane-modified cylindrical polymer brush (CPB) BCPB-F and an alkane-modified analogue BCPB-H. Doxorubicin (DOX) was used as a model drug and was loaded onto the CPBs through a pH-responsive acylhydrazone linkage. High drug loading and good water solubility were achieved. The in vitro and in vivo experiments suggested that fluorination played an important role in improving the cellular uptake, blood circulation, tissue permeability, and tumor targeting ability of CPBs. Due to these superiorities, the DOX-loaded BCPB-F exhibited excellent antitumor efficacy and eradicated the tumors of mice after five-dose treatments. The well-defined structures of the drug-free and drug-loaded CPBs guaranteed the accuracy of the results. This work demonstrates that fluorination is a promising strategy to improve the overall properties of nanomedicines.

Kinetically Programming Copolymerization-like Coassembly of Multicomponent Nanoparticles with DNA

Programmable coassembly of multicomponent nanoparticles (NPs) into heterostructures has the capability to build upon nanostructured metamaterials with enhanced complexity and diversity. However, a general understanding of how to manipulate the sequence-defined heterostructures using straightforward concepts and quantitatively predict the coassembly process remains unreached. Drawing inspiration from the synthetic concepts of molecular block copolymers is extremely beneficial to achieve controllable coassembly of NPs and access mesoscale structuring mechanisms. We herein report a general paradigm of kinetic pathway guidance for the controllable coassembly of bivalent DNA-functionalized NPs into regular block-copolymer-like heterostructures via the stepwise polymerization strategy. By quantifying the coassembly kinetics and structural statistics, it is demonstrated that the coassembly of multicomponent NPs, through directing the specific pathways of prepolymer intermediates, follows the step-growth copolymerization mechanism. Meanwhile, a quantitative model is developed to predict the growth kinetics and outcomes of heterostructures, all controlled by the designed elements of the coassembly system. Furthermore, the stepwise polymerization strategy can be generalized to build upon a great variety of regular nanopolymers with complex architectures, such as multiblock terpolymers and ladder copolymers. Our theoretical and simulation results provide fundamental insights on quantitative predictions of the coassembly kinetics and coassembled outcomes, which can aid in realizing a diverse set of supramolecular DNA materials by the rational design of kinetic pathways.

Self-Assembled DNA-Protein Hybrid Nanospheres: Biocompatible Nano-Drug-Carriers for Targeted Cancer Therapy

We developed hybrid nanospheres comprised of two of the most important biomolecules in nature, DNA and proteins, which have excellent biocompatibility, high drug payload capacity, in vivo imaging ability, and in vitro/in vivo cancer targeting capability. The synthesis can be done in a facile one-pot assembly system that includes three steps: step-growth polymerization of two DNA oligomers, addition of streptavidin to assemble spherical hybrid nanostructures, and functionalization of hybrid nanospheres with biotinylated aptamers. To test the feasibility of cancer targeting and drug-loading capacity of the hybrid nanospheres, MUC1-specific aptamers (MA3) were conjugated to nanosphere surfaces (apt-nanospheres), and doxorubicin (Dox) was loaded into nanospheres by DNA intercalation. The successful construction of nanospheres and apt-nanospheres was confirmed by agarose gel electrophoresis and dynamic light scattering (DLS). Their uniform spherical morphology was confirmed by transmission electron microscopy (TEM). Fluorescence spectra of nanospheres demonstrated high Dox-loading capability and slow-release characteristics. In vitro MUC1-specific binding of the apt-nanospheres was confirmed by flow cytometry and confocal microscopy. Dox-loaded apt-nanospheres significantly increased cytotoxicity of the MUC1-positive cancer cells due to aptamer-mediated selective internalization, as shown via cell viability assays. Apt-nanospheres could also be imaged in vivo through the synthesis of hybrid nanospheres using fluorescent dye-conjugated DNA strands. Finally, in vivo specific targeting ability of apt-nanospheres was confirmed in a MUC1-positive 4T1 tumor-bearing mouse model, whereas apt-nanospheres did not cause any sign of systemic toxicity in normal mice. Taken together, our self-assembled DNA-streptavidin hybrid nanospheres show promise as a biocompatible cancer targeting material for contemporary nanomedical technology.

Molecular polymer bottlebrushes in nanomedicine: therapeutic and diagnostic applications

Molecular polymer bottlebrushes are densely grafted, individual macromolecules with nanoscale proportions. The last decade has seen an increased focus on this material class, especially in nanomedicine and for biomedical applications. This Feature Article provides an overview of major developments in this area to highlight the many opportunities that these polymer architectures bring to nano-bio research. The article covers aspects of bottlebrush synthesis and summarises their use in drug and gene delivery, imaging, as theranostics and as prototype materials to correlate nanoparticle structure and composition to biological function and behaviour. Areas for future research in this area are discussed.

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.

Synthetic Approaches for Copolymers Containing Nucleic Acids and Analogues: Challenges and Opportunities

A deep integration of nucleic acids with other classes of materials have become the basis of many useful technologies. Among these biohybrids, nucleic acid-containing copolymers has seen rapid development in both chemistry and application. This review focuses on the various synthetic approaches to access nucleic acid-polymer biohybrids spanning post-polymerization conjugation, nucleic acids in polymerization, solid-phase synthesis, and nucleoside/nucleobase-functionalized polymers. We highlight the challenges associated with working with nucleic acids with each approach and the ingenuity of the solutions, with the hope of lowering the entry barrier and inpsiring further investigations in this exciting area.

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.