Double Thermoresponsive Block Copolymers Featuring a Biotin End Group

Sequential post-polymerization modification of a pentafluorophenyl ester-containing homopolymer: a convenient route to effective pH-responsive nanocarriers for anticancer drugs

Recently, pH-responsive polymeric micelles have gained significant attention as effective carriers for anti-cancer drug delivery. Herein, pH-responsive polymeric micelles were constructed by a simple post-polymerization modification of a single homopolymer, poly(pentafluorophenyl acrylate) (PPFPA). The PPFPA was first subjected to modification with 1-amino-2-propanol yielding the amphiphilic copolymer of poly(pentafluorophenyl acrylate)-ran-poly(N-(2-hydroxypropyl acrylamide)). A series of amphiphilic random copolymers of different compositions could self-assemble into spherical micelles with a unimodal size distribution in aqueous solution. Then, 1-(3-aminopropyl)imidazole (API), a reagent to introduce charge conversional entities, was reacted with the remaining PPFPA segment in the micellar core resulting in API-modified micelles which can encapsulate doxorubicin (DOX), a hydrophobic anti-cancer drug. As monitored by dynamic light scattering, the API-modified micelles underwent disintegration upon pH switching from 7.4 to 5.0, presumably due to imidazolyl group protonation. This pH-responsiveness of the API-modified micelles was responsible for the faster and greater in vitro DOX release in an acidic environment than neutral pH. Cellular uptake studies revealed that the developed carriers were internalized into MDA-MB-231 cells within 30 min via endocytosis and exhibited cytotoxicity in a dose-dependent manner.

Tuning the thermoresponsive properties of PEG-based fluorinated polymers and stimuli responsive drug release for switchable 19F magnetic resonance imaging

Switching on of the 19F MRI signal via stimuli-responsive release of hydrophobic drug from PEG-based partly-fluorinated polymers due to change in thermoresponsive properties.

Biotin-functionalized copolymeric PEG-PCL micelles for in vivo tumour-targeted delivery of artemisinin

Artemisinin is used as an antimalarial and anticancer agent with minimal toxic effects on the host body. Biotin-PEG-PCL polymers have been used for targeted drug delivery to cancer, as well as to improve the pharmacokinetics of the drug and reduce its effects. In this study, biotin-conjugated copolymers were fabricated with polymerization of the ring opening method and the properties of copolymer and nanoparticles were investigated using various techniques. The toxicity of artemisinin and its nanoparticles have been investigated on MCF-7 and normal HFF2 cells. The results showed that the encapsulation efficacy of artemisinin in nanoparticles was 45.5 ± 0.41%. The release profile of the drug indicates that the release is slow and controlled and is approximately pH dependent. The results of artemisinin cell culture on human breast cancer cells showed that biotin-PEG-PCL nanoparticles had an inhibitory effect on MCF-7 cells and had no toxic effects on HFF2 cells. Anticancer activity in vivo in the 4T1 breast cancer model showed that tumour volumes were decreased up 40 mm³ by ART-loaded micelles and 76 mm³ by free ART, compared to the control group (2150 mm). In vivo results showed that this formulation significantly increases the accumulation of substances in the tumours. Therefore, the molecular formulation of ART-based copolymers can be a desirable process for cancer treatment purposes.

The light-controlling of temperature-responsivity in stimuli-responsive polymers

Light-controlling of phase separation in temperature-responsive polymer solutions by using light-responsive materials for reversible controlling physical and chemical properties of the media with an out-of-system stimulus with tunable intensity.

Recent Advances in Dual Temperature Responsive Block Copolymers and Their Potential as Biomedical Applications

The development of stimuli responsive polymers has progressed significantly with novel preparation techniques, which has allowed access to new materials with unique properties. Dual thermoresponsive (double temperature responsive) block copolymers are particularly of interest as their properties can change depending on the lower critical solution temperature (LCST) or upper critical solution temperature (UCST) of each segment. For instance, these block copolymers can change from being hydrophilic, to amphiphilic or to hydrophobic simply by changing the solution temperature without any additional chemicals and the block copolymers can change from being fully solubilized to self-assembled structures to macroscopic aggregation/precipitation. Based on the unique solution properties, these dual thermo-responsive block copolymers are expected to be suitable for biomedical applications. This review is divided into three parts; LCST-LCST types of block copolymers, UCST-LCST types of block copolymers, and their potential as biomedical applications.

In situ synthesis of thermo-responsive ACB triblock terpolymer nanoparticles through seeded RAFT polymerization

ACB triblock terpolymer nanoparticles containing two thermo-responsive blocks are prepared by seeded RAFT polymerization and their thermo-response is checked.

Combining the incompatible: Block copolymers consecutively displaying activated esters and amines and their use as protein-repellent surface modifiers with multivalent biorecognition

We present the facile synthesis and orthogonal functionalization of diblock copolymers consisting of two incompatible segments, i.e. primary amines and activated esters, and demonstrate their use as protein-repellent brush layers with multivalent biorecognition.

Synthesis of well-defined α,ω-telechelic multiblock copolymers in aqueous medium: in situ generation of α,ω-diols

The synthesis of well-defined α,ω-dihydroxyl telechelic multiblock copolymers by sequential in situ chain extensions via aqueous Cu(0) mediated living radical polymerization (SET-LRP) is reported.

Doubly thermo-responsive nanoparticles constructed with two diblock copolymers prepared through the two macro-RAFT agents co-mediated dispersion RAFT polymerization

Doubly thermo-responsive nanoparticles constructed with two diblock copolymers were prepared, and the nanoparticles exhibit a two-step phase-transition with increasing temperature.

Physics in ordered and disordered colloidal matter composed of poly(N-isopropylacrylamide) microgel particles

This review collects and describes experiments that employ colloidal suspensions to probe physics in ordered and disordered solids and related complex fluids. The unifying feature of this body of work is its clever usage of poly(N-isopropylacrylamide) (PNIPAM) microgel particles. These temperature-sensitive colloidal particles provide experimenters with a 'knob' for in situ control of particle size, particle interaction and particle packing fraction that, in turn, influence the structural and dynamical behavior of the complex fluids and solids. A brief summary of PNIPAM particle synthesis and properties is given, followed by a synopsis of current activity in the field. The latter discussion describes a variety of soft matter investigations including those that explore formation and melting of crystals and clusters, and those that probe structure, rearrangement and rheology of disordered (jammed/glassy) and partially ordered matter. The review, therefore, provides a snapshot of a broad range of physics phenomenology which benefits from the unique properties of responsive microgel particles.

Multi-stimuli responsive polymers – the all-in-one talents

The integration of several responsive moieties within one polymer yields smart polymers exhibiting a multifaceted responsive behaviour.

Doubly thermo-responsive ABC triblock copolymer nanoparticles prepared through dispersion RAFT polymerization

Doubly thermo-responsive triblock copolymer nanoparticles are prepared by a dispersion RAFT polymerization and the nanoparticles exhibit a two-step phase-transition with increasing temperature.

Dual-temperature and pH responsive (ethylene glycol)-based nanogels via structural design

Dual-temperature and pH responsive (ethylene glycol)-based nanogels were synthesized. Both the core and the shell of the nanogels showed a lower critical solution temperature (LCST) and the LCST of the shell was strongly affected by the solution pH and salt concentration due to the presence of carboxylic acid groups at the nanogel surface.

Thiol–Thiosulfonate Chemistry in Polymer Science: Simple Functionalization of Polymers via Disulfide Linkages

Herein we highlight the reaction of thiols with thiosulfonates yielding asymmetric disulfides. The chapter begins with an overview of the synthesis and reactivity of functional thiosulfonates and is followed by a review of polymeric thiosulfonates. We then emphasize the novel use of thiosulfonates as trapping/functionalization agents for macromolecular thiols obtained from parent (co)polymers prepared by reversible addition‐fragmentation chain transfer (RAFT) radical polymerization. We also note how such facile disulfide‐forming chemistries can be readily employed simultaneously with other highly efficient coupling chemistries with an emphasis on the concurrent reaction of activated esters with amines in the presence of thiosulfonates. Finally, we discuss the use of methyl disulfide (SSMe) functional/end‐modified (co)polymers as reagents for the formation of polymeric self‐assembled monolayers (polymer brushes) on metal surfaces such as nanoparticles and quantum dots.

Switchable vesicles formed by diblock random copolymers with tunable pH- and thermo-responsiveness

The thermo-responsiveness of polymers in aqueous media can be tuned by the choice of comonomers used in the synthesis of block copolymers made of random sequences of the same comonomers but of different molar ratios. The same synthetic approach may be applied to other stimuli and we have made diblock random copolymers with both pH- and thermo-responsiveness and studied the formation of vesicles whose membrane core and coronas may be inverted in aqueous media. Sequential reversible addition-fragmentation chain transfer (RAFT) polymerization was used to prepare well-defined block copolymers in the form of AnBm-b-ApCq, where A, B, and C are N-n-propylacrylamide (nPA), 2-(diethylamino)ethyl methacrylate (DEAEMA), and N-ethylacrylamide (EA), respectively. This polymer shows interesting "schizophrenic" behavior in aqueous solutions. Both blocks are thermo-responsive, and one block is pH-responsive in which the tertiary amine group of DEAEMA may be protonated at a lower pH. A molecularly dissolved polymer is obtained at neutral pH and ambient temperature. At pH 7 and 37 °C, the polymer self-assembles into vesicles with the poly(nPA0.8-co-EA0.2) block as the membrane core (mean hydrodynamic diameter of the vesicles Dh = 148 nm). In an alkaline medium (pH 10) at 25 °C, the membrane core and the coronas of the vesicles are inverted with poly(nPA0.8-co-DEAEMA0.2) block forming the core (Dh = 60 nm). In addition, two-step phase transitions are observed in both alkaline and neutral solutions corresponding to the cloud points of the individual blocks. Here, the random nature of the blocks allows fine-tuning the thermo-responsiveness based solely on lower critical solution temperatures and its combination with pH-sensitivity provides vesicles with switchable membrane core and corona in aqueous solution.

Non-ionic, thermo-responsive DEA/DMA nanogels: synthesis, characterization, and use for DNA separations by microchip electrophoresis

Thermo-responsive polymer "nanogels" (crosslinked hydrogel particles with sub-100 nm diameters) are intriguing for many potential applications in biotechnology and medicine. There have been relatively few reports of electrostatically neutral, thermosensitive nanogels comprising a high fraction of hydrophilic co-monomer. Here we demonstrate the syntheses and characterization of novel, non-ionic nanogels based on random N,N-diethylacrylamide (DEA)/N,N-dimethylacrylamide (DMA) copolymers, made by free-radical, surfactant-free dispersion polymerization. The volume-phase transition temperatures of these DEA/DMA nanogels are strongly affected by co-monomer composition, providing a way to "tune" the phase transition temperature of these non-ionic nanogels. While DEA nanogels (comprising no DMA) can be obtained at 70 °C by standard emulsion precipitation, DEA/DMA random co-polymer nanogels can be obtained only in a particular range of temperatures, above the initial phase transition temperature and below the critical precipitation temperature of the DEA/DMA copolymer, controlled by co-monomer composition. Increasing percentages of DMA in the nanogels raises the phase transition temperature, and attenuates and broadens it as well. We find that concentrated DEA/DMA nanogel dispersions are optically clear at room temperature. This good optical clarity was exploited for their use in a novel DNA sieving matrix for microfluidic chip electrophoresis. An ultrafast, high-efficiency dsDNA separation was achieved in less than 120 s for dsDNA ranging from 75 bp to 15,000 bp.

End Group Reactions of RAFT-Prepared (Co)Polymers

This review highlights the chemistry of thiocarbonylthio groups with an emphasis on chemistry conducted at ω or α and ω chain-ends in copolymers prepared by reversible addition–fragmentation chain-transfer (RAFT) radical polymerization. We begin by giving a general overview of reactions associated with the thiocarbonylthio groups, followed by examples associated with macromolecular thiols.