Multi-stimuli sensitive amphiphilic block copolymer assemblies

Self-assembly and dual-stimuli sensitivities of hydroxypropylcellulose-graft-poly(N,N-dimethyl aminoethyl methacrylate) copolymers in aqueous solution

The self-assembly and pH- and thermo-sensitivities properties of hydroxypropyl cellulose-graft-poly(N,N-dimethyl aminoethyl methacrylate) (HPC-g-PDMAEMA) copolymers in aqueous solutions were investigated by transmittance, dynamic light scattering (DLS), and (1)H NMR spectroscopy. Micelles with different structure can be formed by varying either pH value or temperature. At low pH, e.g., 3.0, the HPC backbone of the copolymer collapse to form the core of micelles stabilized with protonated PDMAEMA side chains on the surface of the micelles upon heating. At the medium pH, e.g., 8.1, both HPC backbone and PDMAEMA side chains collapse upon heating to form unstable aggregates. At high pH, e.g., 12.3, PDMAEMA side chains collapse first to form the core of micelles stabilized with HPC chains upon heating. Further heating the copolymer solution at this pH leads to the aggregation of the micelles due to the collapse of the shell HPC chains. The thermal sensitivity of the HPC-g-PDMAEMA copolymers is reversible.

Supramolecular assembly and small molecule recognition by genetically engineered protein block polymers composed of two SADs

Genetically engineered protein block polymers are an important class of biomaterials that have gained significant attention in recent years due to their potential applications in biotechnology, electronics and medicine. The majority of the protein materials have been composed of at least a single self-assembling domain (SAD), enabling the formation of supramolecular structures. Recently, we developed block polymers consisting of two distinct SADs derived from an elastin-mimetic polypeptide (E) and the alpha-helical COMPcc (C). These protein polymers, synthesized as the block sequences--EC, CE, and ECE--were assessed for overall conformation and macroscopic thermoresponsive behavior. Here, we investigate the supramolecular assembly as well as the small molecule binding and release profile of these block polymers. Our results demonstrate that the protein polymers assemble into particles as well as fully or partially networked structures in a concentration dependent manner that is distinct from the individual E and C homopolymers and the E+C non-covalent mixture. In contrast to synthetic block polymers, the structured assembly, binding and release abilities are highly dependent on the composition and orientation of the blocks. These results reveal the promise for these block polymers for therapeutic delivery and biomedical scaffolds.

Multicompartment micelle morphology evolution in degradable miktoarm star terpolymers

Multicompartment micelles with segmented wormlike structures consisting of alternating poly(ethylethylene) (PEE) and poly(gamma-methyl-epsilon-caprolactone) (PMCL) layers were formed upon dispersing samples of micro-[PEE][poly(ethylene oxide)][PMCL] (micro-EOC) miktoarm star block terpolymers in neutral water. Subjecting these dispersions to a pH 12 aqueous buffer at 50 degrees C led to the hydrolytic degradation of the PMCL chains. After 4 weeks, the majority of the micro-EOC molecules were degraded into PEE-b-poly(ethylene oxide) (EO) diblocks and PMCL homopolymers. Although the resulting EO diblocks were expected to assemble into simple cylindrical micelles, the actual "daughter micelle" morphologies were much richer. The initial segmented wormlike micelles evolved into raspberry-like vesicle structures composed of spherical PMCL subdomains embedded in a PEE matrix. This dramatic change in the morphology of the multicompartment micelles is due to rearrangement of micro-EOC/EO/PMCL composite micelles to a structure that minimizes unfavorable interfacial interactions between the three mutually immiscible polymers. This type of micelle-to-micelle morphological evolution induced by block degradation in a miktoarm star terpolymer system holds promise for the development of "smart" delivery capabilities.

Dual redox responsive assemblies formed from diselenide block copolymers

A block copolymer with diselenide bonds in the polymer backbone was reported. This block copolymer was capable of forming micellar aggregates that were responsive to redox stimuli. Compared with other redox responsive aggregates, this type of diselenide-containing block copolymer aggregates could be responsive to both oxidants and reductants even in a solution with a very low concentration under mild conditions.

Stimulus-responsive targeted nanomicelles for effective cancer therapy

Emerging nanotechnology has already developed various innovative nanomedicines. Nanomicelles, self-assemblies of block copolymers, are promising nanomedicines for targeted drug delivery and imaging. Stimulus-responsive targeted nanomicelles are designed to release drugs based on stimuli such as pH, temperature, redox potential, magnetism and ultrasound. This article will focus on recent advancements in the design of stimulus-responsive targeted nanomicelles loaded with anticancer drugs to fulfill the challenges associated with cancer cells (e.g., multidrug resistance) for the effective treatment of cancer. The significant toxicity issues and a possible future perspective associated with nanomicelles are also discussed here.