Thermoresponsive core–shell–corona micelles of poly(ethyleneglycol)-b-poly(N-isopropylacrylamide)-b-polystyrene

Thermoresponsive Poly(glycidyl ether) Brush Coatings on Various Tissue Culture Substrates-How Block Copolymer Design and Substrate Material Govern Self-Assembly and Phase Transition

Thermoresponsive poly(glycidyl ether) brushes can be grafted to applied tissue culture substrates and used for the fabrication of primary human cell sheets. The self-assembly of such brushes is achieved via the directed physical adsorption and subsequent UV immobilization of block copolymers equipped with a short, photo-reactive benzophenone-based anchor block. Depending on the chemistry and hydrophobicity of the benzophenone anchor, we demonstrate that such block copolymers exhibit distinct thermoresponsive properties and aggregation behaviors in water. Independent on the block copolymer composition, we developed a versatile grafting-to process which allows the fabrication of poly(glycidyl ether) brushes on various tissue culture substrates from dilute aqueous-ethanolic solution. The viability of this process crucially depends on the chemistry and hydrophobicity of, both, benzophenone-based anchor block and substrate material. Utilizing these insights, we were able to manufacture thermoresponsive poly(glycidyl ether) brushes on moderately hydrophobic polystyrene and polycarbonate as well as on rather hydrophilic polyethylene terephthalate and tissue culture-treated polystyrene substrates. We further show that the temperature-dependent switchability of the brush coatings is not only dependent on the cloud point temperature of the block copolymers, but also markedly governed by the hydrophobicity of the surface-bound benzophenone anchor and the subjacent substrate material. Our findings demonstrate that the design of amphiphilic thermoresponsive block copolymers is crucial for their phase transition characteristics in solution and on surfaces.

Europium based coordination polyelectrolytes enable core-shell-corona micelles as luminescent probes

Core-shell-corona (CSC) micelles have multiple layers, which can serve as separate compartments. This property allows them to combine multiple functionalities in a single nanoparticle, with obvious application potential. Here, we propose a new type of CSC micelles with an apolar core and a polyelectrolyte complex shell incorporating coordination polymers. We obtain these particles by using a poly(styrene)-b-poly(vinyl pyridine)-b-poly(ethylene oxide) (PS-b-PVP-b-PEO) triblock copolymer with quaternized PVP blocks. This polymer leads to well-defined CSC micelles with a cationic shell, which allows us to entrap anionic coordination polymers without disturbing the micellar structure. Useful properties can be imported in this way, e.g., europium (Eu)-based coordination polymers endow the CSC micelles with strong luminescence. Moreover, copper ions (Cu2+) can quench the luminescence because they disturb the Eu-ligand coordination. Upon adding sulfide ions (S2-), copper ions precipitate as CuS and the Eu-ligand bond as well as the corresponding luminescence are restored. This effect is highly specific for Cu2+ and S2-: other cations or anions hardly interfere with this "on-off-on" luminescence response towards Cu2+ and S2-, demonstrating the selectivity of these CSC micelles as detectors of copper and sulfide ions.

Influence of Grafted Block Copolymer Structure on Thermoresponsiveness of Superparamagnetic Core-Shell Nanoparticles

The morphology and topology of thermoresponsive polymers have a strong impact on their responsive properties. Grafting onto spherical particles has been shown to reduce responsiveness and transition temperatures; grafting of block copolymers has shown that switchable or retained wettability of a surface or particle during desolvation of one block can take place. Here, doubly thermoresponsive block copolymers were grafted onto spherical, monodisperse, and superparamagnetic iron oxide nanoparticles to investigate the effect of thermal desolvation on spherical brushes of block copolymers. By inverting the block order, the influence of core proximity on the responsive properties of the individual blocks could be studied as well as their relative influence on the nanoparticle colloidal stability. The inner block was shown to experience a stronger reduction in transition temperature and transition enthalpy compared to the outer block. Still, the outer block also experiences a significant reduction in responsiveness due to the restricted environment in the nanoparticle shell compared to that of the free polymer state. The demonstrated pronounced distance dependence importantly implies the possibility, but also the necessity, to radially tailor polymer hydration transitions for applications such as drug delivery, hyperthermia, and biotechnological separation for which thermally responsive nanoparticles are being developed.

Synthesis of multifunctional poly(1-pyrenemethyl methacrylate)-b-poly(N-isopropylacrylamide)-b-poly(N-methylolacrylamide)s and their electrospun nanofibers for metal ion sensory applications

PPy-b-PNIPAAm-b-PNMA multifunctional triblock copolymers based electrospun nanofibers detected temperature variation or metal-ions with a high sensitivity.

In situ synthesis of thermo-responsive ABC triblock terpolymer nano-objects by seeded RAFT polymerization

Synthesis of thermo-responsive ABC triblock terpolymer nano-objects by seeded RAFT polymerization is achieved. At temperature above LCST, the triblock terpolymer nano-objects convert into multicompartment nanoparticles.

Poly(ethylene oxide) (PEO)-based ABC triblock terpolymers – synthetic complexity vs. application benefits

This review presents a short summary of possible synthetic routes for the synthesis of poly(ethylene oxide) (PEO) containing triblock terpolymers, as well as different applications in the bulk or in solution – including the preparation of porous materials, hybrid systems, and carriers for controlled drug delivery.

A new strategy to prepare thermo-responsive multicompartment nanoparticles constructed with two diblock copolymers

Thermo-responsive multicompartment nanoparticles containing a PS core, discrete PVEA nodules on the PS core and a PDMAEMA corona are prepared.

Rapid synthesis of near infrared polymeric micelles for real-time sentinel lymph node imaging

In this manuscript a synthetic methodology for developing sub 20 nm sized polymeric micellar nanoparticles designed for extravascular imaging and therapy is revealed. A simple, one-pot method is followed, which involves a rapid co-self-assembly of an amphiphilic diblock copolymer (PS-b-PAA) and polyoxyethylene (80) sorbitan monooleate in water. Sorbitan monooleate imparts stability to the micelles and helps to drive down the particle size below 20 nm. The particles are incorporated with a water soluble dye ADS832WS, which absorbs in the near infrared range (λ(ex) = 832 nm) for sensitive detection with optical and photoacoustic imaging techniques. A candidate lipophilic anti-angiogenic therapeutic agent fumagillin was also incorporated with high entrapment (>95%) efficiency. The effectiveness of this theranostic platform for real-time, high-resolution intraoperative photoacoustic imaging for facilitating direct assessment of the sentinel lymph nodes (SLN) in breast cancer staging is demonstrated. The technique offers huge potential providing faster resection of SLN and may minimize complications caused by axillary exploration due to mismarking with dyes or low-resolution imaging techniques. Finally, the biodistribution and organ accumulation of the intravenously and intradermally injected particles are studied in a rodent model by optical imaging. Data suggest that intraveneously injected NIR-polymeric nanoparticles follow a typical bio-distribution clearance path through the reticuloendothelial (RES) system. For the intradermally injected particles, a slower mechanism of clearance is noticed.

Synthesis, morphology, and sensory applications of multifunctional rod-coil-coil triblock copolymers and their electrospun nanofibers

We report the synthesis, morphology, and applications of conjugated rod-coil-coil triblock copolymers, polyfluorene-block-poly(N-isopropylacrylamide)-block-poly(N-methylolacrylamide) (PF-b-PNIPAAm-b-PNMA), prepared by atom transfer radical polymerization first and followed by click coupling reaction. The blocks of PF, PNIPAAm, and PNMA were designed for fluorescent probing, hydrophilic thermo-responsive and chemically cross-linking, respectively. In the following, the electrospun (ES) nanofibers of PF-b-PNIPAAm-b-PNMA were prepared in pure water using a single-capillary spinneret. The SAXS and TEM results suggested the lamellar structure of the PF-b-PNIPAAm-b-PNMA along the fiber axis. These obtained nanofibers showed outstanding wettability and dimension stability in the aqueous solution, and resulted in a reversible on/off transition on photoluminescence as the temperatures varied. Furthermore, the high surface/volume ratio of the ES nanofibers efficiently enhanced the temperature-sensitivity and responsive speed compared to those of the drop-cast film. The results indicated that the ES nanofibers of the conjugated rod-coil block copolymers would have potential applications for multifunctional sensory devices.

Local and systemic delivery of VEGF siRNA using polyelectrolyte complex micelles for effective treatment of cancer

For efficient cancer therapy, small interfering RNA (siRNA) should be stably and efficiently delivered into the target tissue and readily taken up by cancer cells. To address these needs, a polyelectrolyte complex (PEC) micelle-based siRNA delivery system was developed for anti-angiogenic gene therapy. The interaction between poly(ethylene glycol) (PEG)-conjugated vascular endothelial growth factor siRNA (VEGF siRNA-PEG) and polyethylenimine (PEI) led to the spontaneous formation of nanoscale polyelectrolyte complex micelles (VEGF siRNA-PEG/PEI PEC micelles), having a characteristic siRNA/PEI PEC inner core with a surrounding PEG shell layer. Intravenous as well as intratumoral administration of the PEC micelles significantly inhibited VEGF expression at the tumor tissue and suppressed tumor growth in an animal tumor model without showing any detectable inflammatory responses in mice. Upon examination of the PEC micelle distribution and in vivo optical imaging following intravenously injection, enhanced accumulation of the PEC micelles was also observed in the tumor region. This study demonstrates the feasibility of using PEC micelles as a potential carrier for therapeutic siRNAs in local and systemic treatment of cancer.