Fluorogenic 1,3-Dipolar Cycloaddition within the Hydrophobic Core of a Shell Cross-Linked Nanoparticle

Catalytic activity of new heteroleptic [Cu(PPh3)2(β-oxodithioester)] complexes: click derived triazolyl glycoconjugates

Highly efficient and reusable precatalysts of Cu(i) β-oxodithioester PPh₃ complexes for the synthesis of triazolyl glycoconjugates under “click” conditions.

Highly efficient structurally characterised novel precatalysts: di- and mononuclear heteroleptic Cu(i) dixanthate/xanthate–phosphine complexes for azide–alkyne cycloadditions

Prominent catalytic activities of novel di- and mononuclear Cu(i) xanthate/phosphine complexes have been investigated for the synthesis of triazolyl glycoconjugates using Click approach.

Synthesis of Modular Brush Polymer-Protein Hybrids Using Diazotransfer and Copper Click Chemistry

Proteoglycans are important brush-like biomacromolecules, which serve a variety of functions in the human body. While protein-bottlebrush hybrids are promising proteoglycan mimics, many challenges still exist to robustly produce such polymers. In this paper, we report the modular synthesis of protein-brush hybrids containing elastin-like polypeptides (ELP) as model proteins by copper-catalyzed azide-alkyne cycloaddition. We exploit the recently discovered imidazole-1-sulfonyl azide (ISA) in a diazotransfer reaction to introduce an N-terminal azide onto an ELP. Next, we use a click reaction to couple the azido-ELP to an alkyne-terminated amine-rich polymer followed by a second diazotransfer step to produce an azide-rich backbone that serves as a scaffold. Finally, we used a second click reaction to graft alkyne-terminated poly(oligoethylene glycol methacrylate) (POEGMA) bristles to the azide-rich backbone to produce the final protein-bottlebrush hybrid. We demonstrate the effectiveness of this synthetic path at each step through careful characterization with ¹H NMR, FTIR, GPC, and diagnostic test reactions on SDS-PAGE. Final reaction products could be consistently obtained for a variety of different molecular weight backbones with final total grafting efficiencies around 70%. The high-yielding reactions employed in this highly modular approach allow for the synthesis of protein-bottlebrush hybrids with different proteins and brush polymers. Additionally, the mild reaction conditions used have the potential to avoid damage to proteins during synthesis.

Development of controlled drug delivery systems for bone fracture-targeted therapeutic delivery: A review

Impaired fracture healing is a major clinical problem that can lead to patient disability, prolonged hospitalization, and significant financial burden. Although the majority of fractures heal using standard clinical practices, approximately 10% suffer from delayed unions or non-unions. A wide range of factors contribute to the risk for nonunions including internal factors, such as patient age, gender, and comorbidities, and external factors, such as the location and extent of injury. Current clinical approaches to treat nonunions include bone grafts and low-intensity pulsed ultrasound (LIPUS), which realizes clinical success only to select patients due to limitations including donor morbidities (grafts) and necessity of fracture reduction (LIPUS), respectively. To date, therapeutic approaches for bone regeneration rely heavily on protein-based growth factors such as INFUSE, an FDA-approved scaffold for delivery of bone morphogenetic protein 2 (BMP-2). Small molecule modulators and RNAi therapeutics are under development to circumvent challenges associated with traditional growth factors. While preclinical studies has shown promise, drug delivery has become a major hurdle stalling clinical translation. Therefore, this review overviews current therapies employed to stimulate fracture healing pre-clinically and clinically, including a focus on drug delivery systems for growth factors, parathyroid hormone (PTH), small molecules, and RNAi therapeutics, as well as recent advances and future promise of fracture-targeted drug delivery.

RAFT polymerization to form stimuli-responsive polymers

Stimuli-responsive polymers respond to a variety of external stimuli, which include optical, electrical, thermal, mechanical, redox, pH, chemical, environmental and biological signals. This paper is concerned with the process of forming such polymers by RAFT polymerization.

Synthesis, photophysical and electrochemical properties and DSSC applications of triphenylamine chalcone dendrimers via click chemistry

Fluorene-cored dendrimers containing a triphenylamine chalcone unit at the periphery have been synthesized by click chemistry approach, and their photophysical and electrochemical properties have been investigated.

A dinuclear copper(i) thiodiacetate complex as an efficient and reusable ‘click’ catalyst for the synthesis of glycoconjugates

A novel Cu(i) complex as an efficient and reusable homogeneous “click” catalyst.

Core functionalization of semi-crystalline polymeric cylindrical nanoparticles using photo-initiated thiol-ene radical reactions

Sequential ring-opening and reversible addition-fragmentation chain transfer (RAFT) polymerization was used to form a triblock copolymer of tetrahydropyran acrylate (THPA), 5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one (MAC) and l-lactide. Concurrent deprotection of the THPA block and crystallization-driven self-assembly (CDSA) was undertaken and allowed for the formation of cylindrical micelles bearing allyl handles in a short outer core segment. These handles were further functionalized by different thiols using photo-initiated thiol-ene radical reactions to demonstrate that the incorporation of an amorphous PMAC block within the core does not disrupt CDSA and can be used to load the cylindrical nanoparticles with cargo.

Qualitative sensing of mechanical damage by a fluorogenic “click” reaction

A simple and unique damage-sensing tool mediated by a Cu(i)-catalyzed [3+2] cycloaddition reaction is reported, where a fluorogenic “click”-reaction highlights physical damage by a strong fluorescence increase accompanied by in situ monitoring of localized self-healing.

(PAA-g-PS)-co-PPEGMEMA asymmetric polymer brushes: synthesis, self-assembly, and encapsulating capacity for both hydrophobic and hydrophilic agents

(PAA-g-PS)-co-PPEGMEMA asymmetric polymer brushes formed large compound micelles in aqueous media for encapsulating both hydrophobic pyrene and hydrophilic Rhodamine 6G.

Facile preparation and properties of multifunctional polyacetylene via highly efficient click chemistry

A series of novel multifunctional polyacetylenes bearing oxadiazole and azo groups as molecular pendants were designed and synthesizedviahighly effective click chemistry.

A robust platform for functional microgels via thiol-ene achemistry with reactive polyether-based nanoparticles

We herein report the development of crosslinked polyether particles as a reactive platform for the preparation of functional microgels. Thiol-ene crosslinking of poly(allyl glycidyl ether) in miniemulsion droplets - stabilized by a surface active, bio-compatible polyethylene glycol block copolymer - resulted in colloidal gels with a PEG corona and an inner polymeric network containing reactive allyl units. The stability of the allyl groups allows the microgels to be purified and stored before a second, subsequent thiol-ene functionalization step allows a wide variety of pH- and chemically-responsive groups to be introduced into the nanoparticles. The facile nature of this synthetic platform enables the preparation of microgel libraries that are responsive to different triggers but are characterized by the same size distribution, surface functionality, and crosslinking density. In addition, the utilization of a crosslinker containing cleavable ester groups renders the resulting hydrogel particles degradable at elevated pH or in the presence of esterase under physiological conditions.

Solution processable polyamines via click chemistry for water purification

Highly stable amine functionalized polystyrenes were prepared and used for the removal of dissolved pollutants from water.

RAFT copolymerization of acid chloride-containing monomers

Controlled radical copolymerization of acid chloride-containing monomers via RAFT enabled direct synthesis of well-defined reactive polymers and their block polymers which can be readily functionalized further by postpolymerization modification.

pH-Regulated Controlled Swelling and Sustained Release from the Core Functionalized Amphiphilic Block Copolymer Micelle

pH-responsive amphiphilic block copolymers based on poly(ethylene glycol)monomethyl ether-b-poly(methyl methacrylate-co-methacrylamidepropanoic acid) (PEO-b-PMMA-co-PMAPA) with different MMA/MAPA ratios were synthesized from respective amine-reactive prepolymers based on poly(ethylene glycol)monomethyl ether-b-poly(methyl methacrylate-co-methacryloxysuccinimide) (PEO-b-PMMA-co-PMASI) in such a way that the pH-responsive carboxylic acid groups were randomly distributed in the hydrophobic (PMMA) block. In aqueous medium, they formed micellar aggregates. Control experiments showed stability and critical aggregation concentration and dye encapsulation properties were better for carboxylic acid functionalized micelles at acidic pH compared to a structurally similar block copolymer micelle that lacked any carboxylic acid group. This was attributed to H-bonding among the carboxylic acid groups. In basic pH upon deprotonation, controlled swelling of the aggregates was observed due to repulsion among the negatively charged carboxylate groups. The extent of swelling/deswelling was well controlled by simply changing the percentage of the pH-responsive units in the hydrophobic block and could be probed quantitatively by pH-dependent dynamic light scattering (DLS) and fluorescence resonance energy transfer (FRET) studies. The aggregates were able to encapsulate a hydrophobic guest such as pyrene at the interior of the micelle, and sustained release of this hydrophobic probe was achieved selectively at basic pH due to swelling of the micelles instead of complete disassembly that generally leads to burst release.

A "Mix-and-Click" Approach to Double Core-Shell Micelle Functionalization

A micellar scaffold formed by self-assembly of a reversible addition-fragmentation chain transfer (RAFT)-synthesized amphiphilic diblock copolymer has been prepared to contain two orthogonal click-compatible functionalities in the core and shell. These functionalities (norbornenes in the core and terminal alkynes in the shell) have been used as handles to modify the micellar assembly in the core using tetrazine-norbornene chemistry or the shell using the copper-catalyzed azide-alkyne reaction. Additionally, both core and shell modifications were carried out in a tandem, one-pot process using the orthogonal chemistries mentioned above. In all cases the reactions were found to be highly efficient, requiring little excess of the modifying small molecule and very simple to perform under ambient conditions.

Polymeric assemblies and nanoparticles with stimuli-responsive fluorescence emission characteristics

Fluorescent polymeric assemblies and nanoparticles (NPs) of nanoscale dimensions have become a focus of intensive investigations during the past few decades due to combined advantages such as improved biocompatibility, water dispersibility, stimuli-responsiveness, facile integration into optical detection devices, and the ability of further functionalization. In addition, the chemical composition and morphology of polymeric assemblies and NPs can be modulated via synthetic approaches, leading to the precise spatial organization of multiple fluorophores. Thus, polymeric assemblies and NPs have been utilized to optimize the photoluminescent properties of covalently or physically attached fluorophores and facilely modulate the fluorescence resonance energy transfer (FRET) processes when the polymeric matrix is endowed with stimuli-responsiveness. These fascinating fluorescent polymeric assemblies and NPs offer unique and versatile platforms for the construction of novel detection, imaging, biolabeling, and optoelectronic systems. This feature article focuses on the recent developments of polymeric assemblies and NPs-based stimuli-tunable fluorescent systems and highlights their future practical applications with selected literature reports.

Core-clickable PEG-branch-azide bivalent-bottle-brush polymers by ROMP: grafting-through and clicking-to

The combination of highly efficient polymerizations with modular "click" coupling reactions has enabled the synthesis of a wide variety of novel nanoscopic structures. Here we demonstrate the facile synthesis of a new class of clickable, branched nanostructures, polyethylene glycol (PEG)-branch-azide bivalent-brush polymers, facilitated by "graft-through" ring-opening metathesis polymerization of a branched norbornene-PEG-chloride macromonomer followed by halide-azide exchange. The resulting bivalent-brush polymers possess azide groups at the core near a polynorbornene backbone with PEG chains extended into solution; the structure resembles a unimolecular micelle. We demonstrate copper-catalyzed azide-alkyne cycloaddition (CuAAC) "click-to" coupling of a photocleavable doxorubicin (DOX)-alkyne derivative to the azide core. The CuAAC coupling was quantitative across a wide range of nanoscopic sizes (∼6-∼50 nm); UV photolysis of the resulting DOX-loaded materials yielded free DOX that was therapeutically effective against human cancer cells.