Rui Qi

Oxidation responsive mono-cleavable amphiphilic di-block polymer micelles labeled with a single diselenide

A novel diselenide-containing mono-cleavable amphiphilic di-block polymer, denoted MPEG-IPDI-SeSe-IPDI-PPG, composed of one hydrophilic poly(ethylene glycol) monomethyl ether (MPEG) block and one hydrophobic polypropylene glycol (PPG) block, was synthesized via four coupling reactions in sequence. MPEG-IPDI-SeSe-IPDI-PPG is able to self-assemble into spherical micelles in aqueous solution. Subsequently, it was found that the spherical micelles have a oxidation-responsiveness and undergo a morphology transformation from spherical micelles to large compound micelles (LCMs) in an oxidative environment (0.5%wt H2O2) due to the unique oxidation-responsive cleavage of the diselenide group, resulting in an initially fast release of loaded Rhodamine B (RB), followed by slow, continuously increasing release. It is anticipated that these mono-cleavable polymer micelles containing diselenide may find application in the field of drug delivery systems.

Oxidation- and thermo-responsive poly(N-isopropylacrylamide-co-2-hydroxyethyl acrylate) hydrogels cross-linked via diselenides for controlled drug delivery

A novel diselenide crosslinked poly(N-isopropylacrylamide-co-2-hydroxyethyl acrylate) hydrogel was successfully synthesized and characterized. The resultant hydrogel showed a swelling–shrinkage behavior as a function of external temperature because of the unique hydrophilic–hydrophobic transition of poly(N-isopropylacrylamide) (PNIPAM) segments. In addition to the temperature-dependent response, the oxidation-induced gel-to-sol transition of the hydrogel was also observed. The salicylic acid (SA) loaded hydrogels were prepared in order to investigate their stimuli-responsive release behaviors. The cumulative release profile of the SA-loaded hydrogels showed a thermo-induced slow sustained drug release and an oxidation-induced quick burst release, exhibiting temperature/oxidation dual-stimuli-responsive drug release. This novel type of hydrogels may hold great promise for controlled drug delivery systems.

An injectable, dual pH and oxidation-responsive supramolecular hydrogel for controlled dual drug delivery.

A novel pH and oxidation dual-responsive and injectable supramolecular hydrogel was developed, which was formed from multi-block copolymer poly(ether urethane) (PEU) and α-cyclodextrin (α-CD) inclusion complexes (ICs). The PEU copolymer was synthesized through a simple one-pot condensation polymerization of poly(ethylene glycol), di(1-hydroxyethylene) diselenide, dimethylolpropionic acid and 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate. In aqueous solution, the amphiphilic PEU copolymers could self-assemble into nanoparticles with dual pH and oxidation sensitivities, which can efficiently load and controllably release a hydrophobic drug indomethacin (IND). Then a dual-drug loaded supramolecular hydrogel was obtained by addition of α-CD and hydrophilic model drug (rhodamine B, RB) into the resulting IND-loaded PEU nanoparticle solution. The rheology studies showed that the supramolecular hydrogels with good injectability underwent a pH-induced reversible sol-gel transition and an oxidation-triggered degradation behavior. The in vitro drug release results demonstrated that the hydrogels showed dual drug release behavior and the release rates could be significantly accelerated by addition of an oxidizing agent (H2O2) or increasing the environmental pH. Therefore, this injectable and dual stimuli-responsive supramolecular hydrogel based codelivery systems could potentially be a promising candidate for controlled drug delivery systems.

Crystallization-Driven Self-Assembly of Rod-Coil-Rod Pseudopolyrotaxanes into Spherical Micelles, Nanorods, and Nanorings in Aqueous Solutions.

A novel rod-containing block copolymer is constructed by supramacromolecular self-assembly of α-cyclodextrin and a triblock copolymer with methoxy polyethylene glycol as the flanking chains and the midterm block alternately connected by 2,2-dimethylolbutyric acid and isophorone diisocyanate. The assembled rod-containing block copolymer shows an exciting phenomenon of concentration- and pH-dependent morphological switching of well-defined nanostructures. In the solutions at pH 9.2, spherical micelles, rod-like micelles, and hydrogel are observed successively with an increase of the concentration. Notably, the rod-like micelles are composed of spherical segments due to the combination of the crystalline cores of the spherical micelles. In addition, 1D nanostructures with different curvatures from linear rod-like micelles (pH 9.2) to ring-shaped micelles (pH 7.5) can be obtained by controlling the pH values of the assembled systems.

Aqueous Self-Assembly of Y-Shaped Amphiphilic Block Copolymers into Giant Vesicles

The preparation and aqueous self-assembly of newly Y-shaped amphiphilic block polyurethane (PUG) copolymers are reported here. These amphiphilic copolymers, designed to have two hydrophilic poly(ethylene oxide) (PEO) tails and one hydrophobic alkyl tail via a two-step coupling reaction, can self-assemble into giant unilamellar vesicles (GUVs) (diameter ≥ 1000 nm) with a direct dissolution method in aqueous solution, depending on their Y-shaped structures and initial concentrations. More interesting, the copolymers can self-assemble into various distinct nano-/microstructures, such as spherical micelles, small vesicles, and GUVs, with the increase of their concentrations. The traditional preparation methods of GUVs generally need conventional amphiphilic molecules and additional complicated conditions, such as alternating electrical field, buffer solution, or organic solvent. Therefore, the self-assembly of Y-shaped PUGs with a direct dissolution method in aqueous solution demonstrated in this study supplies a new clue to fabricate GUVs based on the geometric design of amphiphilic polymers.

Synthesis and surface activity of mono- and diphosphate ester mixture with different alkyl chain length

ABSTRACT A series of alkyl phosphate esters were synthesized and each of them was a mixture of monophosphate and diphosphate esters in a high or low mono/dimole ratio. The structure of hexadecyl phosphate ester with a low mono/dimole ratio was confirmed by FTIR, 1H NMR, and31P NMR. The surface tensions of these alkyl phosphate esters were analyzed using a surface tensionmeter. The results showed that the critical micelle concentration (CMC) and critical surface tension (γCMC) of phosphate esters with a high mono/di ratio decreased with the increase of alkyl chain length. However, for the phosphate esters with a low mono/di ratio, the CMC, and γCMC decreased initially and increased afterwards with the increase of alkyl chain length. Meanwhile, the butanol and octanol phosphate esters with a high mono/di ratio had higher CMC and γCMC than their low mono/di ones, while the dodecyl and hexadecyl phosphate esters presented an opposite result. The results indicated that the mono- and diphosphate esters in the mixture may have a synergistic effect on the arrangement of molecules. GRAPHICAL ABSTRACT

pH- and concentration-controlled self-assembly of spherical micelles with cavity, necklace and cylindrical micelles

A novel diblock copolymer with one block alternatively connected with hydrophobic motifs, hydrogen-bonding carbamates and pH-triggered carboxy groups was developed, which showed an exciting pH- and concentration-dependent self-assembly of spherical micelles with cavity, necklaces and cylindrical micelles.