Para-Fluoro Postpolymerization Chemistry of Poly(pentafluorobenzyl methacrylate): Modification with Amines, Thiols, and Carbonylthiolates

Facile Generation of Heterotelechelic Poly(2-Oxazoline)s Towards Accelerated Exploration of Poly(2-Oxazoline)-Based Nanomedicine

Controlling the end-groups of biocompatible polymers is crucial for enabling polymer-based therapeutics and nanomedicine. Typically, end-group diversification is a challenging and time-consuming endeavor, especially for polymers prepared via ionic polymerization mechanisms with limited functional group tolerance. In this study, we present a facile end-group diversification approach for poly(2-oxazoline)s (POx), enabling quick and reliable production of heterotelechelic polymers to facilitate POxylation. The approach relies on the careful tuning of reaction parameters to establish differential reactivity of a pentafluorobenzyl initiator fragment and the living oxazolinium chain-end, allowing the selective introduction of N-, S-, O-nucleophiles via the termination of the polymerization, and a consecutive nucleophilic para-fluoro substitution. The value of this approach for the accelerated development of nanomedicine is demonstrated through the synthesis of well-defined lipid-polymer conjugates and POx-polypeptide block-copolymers, which are well-suited for drug and gene delivery. Furthermore, we investigated the application of a lipid-POx conjugate for the formulation and delivery of mRNA-loaded lipid nanoparticles for immunization against the SARS-COV-2 virus, underscoring the value of POx as a biocompatible polymer platform.

Synthesis and biological properties of novel glucose-based fluoro segmented macromolecular architectures

The emergence of novel well-defined biological macromolecular architectures containing fluorine moieties displaying superior functionalities can satisfactorily address many biomedical challenges. In this research, ABA- and AB-type glucose-based biological macromolecules were synthesized using acryl-2,3,4,6-tetra-O-acetyl-D-glucopyranoside with pentafluorophenyl (FPM), pentafluorobenzyl (FBM), phenyl (PM) and benzyl (BM) methacrylate-based macro-RAFT agents following RAFT polymerization. The macro-RAFT agents and the corresponding copolymers were characterized by 19F, 1H, and 13C NMR and FTIR spectroscopic techniques to understand the chemical structure, molecular weight by size-exclusion chromatography, thermal analysis by TGA and DSC. Thermal stability (Td5%) of the FPM and FBM fluoro-based polymers was observed in the range of 219-267 °C, while the non-fluoro PM and BM polymers exhibited in the range of 216-264 °C. Among the macro-RAFT agents, PFPM (107 °C, ΔH: 0.613 J/g) and PPM (103 °C, ΔH: 0.455 J/g) showed higher Tm values, while among the block copolymers, PFBM-b-PG (123 °C, ΔH: 0.412 J/g) and PG-b-PFPM-b-PG (126 °C, ΔH: 0.525 J/g) exhibited higher Tm values. PFBMT and PPM macro-RAFT agents, PPM-b-PG and PG-b-PPM-b-PG copolymer spin-coated films showed the highest hydrophobicity (120°) among the synthesized polymers. The block copolymers exhibited self-assembled segregation by using relatively hydrophobic segments as the core and hydrophilic moieties as the corona. Synthesized biological macromolecules exhibit maximum antibacterial activity towards S. aureus than E. coli bacteria. Fluorophenyl (PFPM) and non-fluorobenzyl-based (PBMT) macro-RAFT agents exhibit low IC50 values, suggesting high cytotoxicity. All the triblock copolymers exhibit lesser cytotoxicity than the di-block polymers.

Thiol-triggered deconstruction of bifunctional silyl ether terpolymers via an SNAr-triggered cascade

While Si-containing polymers can often be deconstructed using chemical triggers such as fluoride, acids, and bases, they are resistant to cleavage by mild reagents such as biological nucleophiles, thus limiting their end-of-life options and potential environmental degradability. Here, using ring-opening metathesis polymerization, we synthesize terpolymers of (1) a "functional" monomer (e.g., a polyethylene glycol macromonomer or dicyclopentadiene); (2) a monomer containing an electrophilic pentafluorophenyl (PFP) substituent; and (3) a cleavable monomer based on a bifunctional silyl ether . Exposing these polymers to thiols under basic conditions triggers a cascade of nucleophilic aromatic substitution (SNAr) at the PFP groups, which liberates fluoride ions, followed by cleavage of the backbone Si-O bonds, inducing polymer backbone deconstruction. This method is shown to be effective for deconstruction of polyethylene glycol (PEG) based graft terpolymers in organic or aqueous conditions as well as polydicyclopentadiene (pDCPD) thermosets, significantly expanding upon the versatility of bifunctional silyl ether based functional polymers.

A mannosylated polymer with endosomal release properties for peptide antigen delivery

Peptide cancer vaccines have had limited clinical success despite their safety, characterization and production advantages. We hypothesize that the poor immunogenicity of peptides can be surmounted by delivery vehicles that overcome the systemic, cellular and intracellular drug delivery barriers faced by peptides. Here, we introduce Man-VIPER, a self-assembling (40-50 nm micelles), pH-sensitive, mannosylated polymeric peptide delivery platform that targets dendritic cells in the lymph nodes, encapsulates peptide antigens at physiological pH, and facilitates endosomal release of antigens at acidic endosomal pH through a conjugated membranolytic peptide melittin. We used d-melittin to improve the safety profile of the formulation without compromising the lytic properties. We evaluated polymers with both releasable (Man-VIPER-R) or non-releasable (Man-VIPER-NR) d-melittin. Both Man-VIPER polymers exhibited superior endosomolysis and antigen cross-presentation compared to non-membranolytic d-melittin-free analogues (Man-AP) in vitro. In vivo, Man-VIPER polymers demonstrated an adjuvanting effect, induced the proliferation of antigen-specific cytotoxic T cells and helper T cells compared to free peptides and Man-AP. Remarkably, antigen delivery with Man-VIPER-NR generated significantly more antigen-specific cytotoxic T cells than Man-VIPER-R in vivo. As our candidate for a therapeutic vaccine, Man-VIPER-NR exerted superior efficacy in a B16F10-OVA tumor model. These results highlight Man-VIPER-NR as a safe and powerful peptide cancer vaccine platform for cancer immunotherapy.

Azide Photochemistry in Acrylic Copolymers for Ultraviolet Cross-Linkable Pressure-Sensitive Adhesives: Optimization, Debonding-on-Demand, and Chemical Modification

Pressure-sensitive adhesives (PSAs) are usually made from viscoelastic, high-molecular-weight copolymers, which are fine-tuned by adjusting the comonomer ratios, molecular weights, and cross-link densities to optimize the adhesion properties for the desired end-use. To create a lightly cross-linked network, an ultraviolet (UV) photoinitiator can be incorporated. Here, we present the first use of perfluorophenylazide chemistry to control precisely a polyacrylate network for application as a PSA. Upon UV irradiation, the highly reactive nitrene from the azide moiety reacts with nearby molecules through a C-H insertion reaction, resulting in cross-linking via covalent bonding. This approach offers three benefits: (1) a means to optimize adhesive properties without the addition of an external photoinitiator; (2) the ability to switch off the tack adhesion on demand via a high cross-linking density; and (3) a platform for additional chemical modification. A series of poly(n-butyl acrylate-co-2,3,4,5,6-pentafluorobenzyl acrylate) or poly(PFBA-co-BA) copolymers were synthesized and modified post-polymerization into the photo-reactive poly(n-butyl acrylate-co-4-azido-2,3,5,6-tetrafluorobenzyl acrylate) [azide-modified poly(PFBA-co-BA)] with various molar contents. When cast into films, the azide-modified copolymers with a high azide content achieved a very high shear resistance after UV irradiation, whereas the tack and peel adhesion decreased strongly with the increase in azide content, indicating that excessive cross-linking occurred. These materials are thus photo-switchable. However, in the low range of azide content, an optimum probe tack adhesion energy was obtained in films with a 0.3 mol % azide content, where a long stress plateau (indicating good fibrillation) with a high plateau stress was observed. An optimum peel adhesion strength was achieved with 0.5 mol % azide. Thus, the adhesion was finely controlled by the degree of cross-linking of the PSA, as determined by the azide content of the copolymer chain. Finally, as a demonstration of the versatility and advantages of the material platform, we show an azide-aldehyde-amine multicomponent modification of the azide copolymer to make a dye-functionalized film that retains its adhesive properties. This first demonstration of using azide functionality has enormous potential for functional PSA design.

Polymerization-Induced Self-Assembly (PISA) for in situ drug encapsulation or drug conjugation in cancer application

HYPOTHESIS

We describe the possibility of using the same block copolymer carriers prepared by PISA for in situ drug encapsulation or drug conjugation.

EXPERIMENTS

Block copolymers containing poly((ethylene glycol) methacrylate)-co-poly(pentafluorophenyl methacrylate)-b-poly(hydroxypropyl methacrylate) (P((PEGMA-co-PFBMA)-b-PHPMA)) were synthesized at 10 wt% using PISA. The first approach involved in situ Doxorubicin (DOX) loading during PISA, while the second exhibited surface functionalization of PISA-made vesicles with dual drug therapies, N-acetyl cysteine (NAC) and DOX using para-fluoro-thiol reaction (PFTR) and carbodiimide chemistry, respectively. Cytotoxicity, cell uptake, and cell apoptosis were assessed on MDA-MB-231 cell lines.

FINDINGS

P((PEGMA-co-PFBMA)-b-PHPMA) nanocarriers were prepared, showing size and shape transformations from spheres, cylinders to raspberry-forming vesicles. DOX was readily loaded into NPs during PISA with relatively high encapsulation efficiency of 70 %, whereas the plain PISA-made vesicles could be functionalized with NAC and DOX at high yields. DOX-free NPs showed biocompatibility, whilst DOX-conjugated NPs imparted a concentration-dependent cytotoxicity, as well as an enhanced cell uptake compared to free DOX. The results demonstrated that the same PISA-derived self-assemblies enabled either in situ drug encapsulation, or post-polymerization surface engineering with useful functionalities upon tuning the macro-CTA block, thus holding promises for future drug delivery and biomedical applications.

Depolymerizable semi-fluorinated polymers for sustainable functional materials

Chemically recyclable semi-fluorinated polymers are demonstrated for the first time, and the hydrophobicity, self-assembly, and post-polymerization functionalization of these polymers are explored.

Core-functionalized nanoaggregates: preparation via polymerization-induced self-assembly and their applications

Core-functionalized nanoaggregates can be prepared by a combination of polymerization-induced self-assembly (PISA) and post-polymerization modification.

Solution self-assembly of fluorinated polymers, an overview

The incorporation of fluorinated moieties into a polymer can confer unique properties and often lead in solution to original morphologies endowed with rare properties.

Fluorinated Polymers via Para-Fluoro-Thiol and Thiol-Bromo Click Step Growth Polymerization

Click reactions are utilized widely to modify chain ends and side groups of polymers while click polymerizations based on step-growth polymerization of bifunctional monomers have recently attracted increased attention of polymer chemists. Herein, the combination of two highly efficient click reactions, namely para-fluoro-thiol click and thiol-bromo substitution reactions, is demonstrated to form fluorinated polymers with tuned hydrophobicity owing to the nature of the dithiol linker compound. The key compound in this study is 2,3,4,5,6-pentafluoro benzyl bromide that provides the combination of thiol click reactions. The thiols used here are 4,4-thiobisbenzenthiol, 2,2'-(ethylenedioxy) diethanethiol, and 1,2-ethanedithiol that allow tuning of the properties of obtained polymers. The step-growth click reaction conditions are optimized by screening the effect of reaction temperature, base, solvent, and stochiometric ratio of the compounds. Thermal properties and hydrophobicity of synthesized polymers are determined via water contact angle, thermogravimetric analysis and differential scanning calorimetry measurements, showing thermal stability up to 300 °C, glass transition temperatures ranging from -25 to 82 °C and water contact angles ranging from 55 to 90 °C.

An in-depth analysis approach enabling precision single chain nanoparticle design

The synthesis of single chain nanoparticles (SCNPs) is a vibrant field in macromolecular science. However, to achieve an in-depth understanding of the nature of intramolecular polymer folding, a step-change in the methodologies for SCNP analysis is required.

Sphere-to-worm morphological transitions and size changes through thiol–para-fluoro core modification of PISA-made nano-objects

Spherical diblock copolymer nanoparticles became larger spheres, unimers, or worm-shaped particles when functionalised via thiol–para-fluoro substitution in the core.

Visible light enabled para-fluoro-thiol ligation

The visible light-trigged para-fluoro-thiol ligation is demonstrated for first time by using the photogeneration of a superbase DBU.

The para-fluoro-thiol reaction as an efficient tool in polymer chemistry

The current literature describing the application of the para-fluoro–thiol reaction in the realm of macromolecular chemistry and the future of this coupling strategy are discussed.