Hao Yao

PGMA-based supramolecular hyperbranched polycations for gene delivery

Supramolecular chemistry has been widely applied in biomedical fields. It was reported that the topological structure has effects on the performance of gene delivery systems. Supramolecular polymer-like gene carriers with hyperbranched topological structures have still not been reported. In this work, a series of ethanolamine-functionalized polyglycidyl methacrylate (PGMA)-armed AB2 type macromonomers were synthesized based on atom transfer radical polymerization. The AB2 type macromonomers can self-assemble into supramolecular hyperbranched polymers by the host–guest interaction between adamantane and β-cyclodextrin. The biophysical properties of self-assembled and dissembled supramolecular hyperbranched polycations were evaluated in detail. The self-assembled supramolecular polycations with hyperbranched structures possessed higher pDNA condensation ability and much better gene transfection performances than the dissembled AB2 type counterparts. The present work would provide a new venue for designing advanced high-performance supramolecular hyperbranched nucleic acid-delivery systems.

Host-Guest Binding-Site-Tunable Self-Assembly of Stimuli-Responsive Supramolecular Polymers.

Despite the remarkable progress made in controllable self-assembly of stimuli-responsive supramolecular polymers (SSPs), a basic issue that has not been consideration to date is the essential binding site. The noncovalent binding sites, which connect the building blocks and endow supramolecular polymers with their ability to respond to stimuli, are expected to strongly affect the self-assembly of SSPs. Herein, the design and synthesis of a dual-stimuli thermo- and photoresponsive Y-shaped supramolecular polymer (SSP2) with two adjacent β-cyclodextrin/azobenzene (β-CD/Azo) binding sites, and another SSP (SSP1) with similar building blocks, but only one β-CD/Azo binding site as a control, are described. Upon gradually increasing the polymer solution temperature or irradiating with UV light, SSP2 self-assemblies with a higher binding-site distribution density; exhibits a flower-like morphology, smaller size, and more stable dynamic aggregation process; and greater controllability for drug-release behavior than those observed with SSP1 self-assemblies. The host-guest binding-site-tunable self-assembly was attributed to the positive cooperativity generated among adjacent binding sites on the surfaces of SSP2 self-assemblies. This work is beneficial for precisely controlling the structural parameters and controlled release function of SSP self-assemblies.

Adsorption characteristics of graphene oxide nanosheets on cement

Modifying cement with graphene oxide (GO) nanosheets tremendously improves its mechanical properties but decreases its fluidity. The adsorption characteristics between GO and cement play a pivotal role in the influence on fluidity. In this paper, the adsorption characteristics of graphene oxide nanosheets on cement were investigated using scanning electron microscopy (SEM), total organic carbon (TOC), Fourier transform infrared spectra (FTIR) and XPS analyses. The results show that GO nanosheets have a strong adsorption ability on the cement surface. The adsorption data was best fitted with the Freundlich adsorption isotherm model and described by a pseudo-second order kinetics model. The adsorption process includes a chemical reaction where the –COOH groups on the edge of the GO nanosheets react with metal cations. The adsorption layer thickness of the GO nanosheets on the cement was about 10.16 nm.

Morphology transitions of supramolecular hyperbranched polymers induced by double supramolecular driving forces

Tuning the morphology of supramolecular hyperbranched polymers (SHPs) in solution has theoretical and practical significance in SHP applications. This study successfully achieved SHP morphology transitions from branched supramolecular structures to spherical nanosized micelles in mixed solvents. Transmission electron microscopy, dynamic light scattering, 2D 1H NMR ROESY, and fluorescence emission spectroscopy confirmed these transitions. An AB2-type amphiphilic β-cyclodextrin (β-CD) monomer (Ada-CD2) exhibiting double supramolecular interactions was initially synthesized. SHPs based on Ada-CD2 were then formed in DMF–H2O mixed solvents through the host–guest inclusion interaction between β-CD and Ada. The formed SHPs disassembled with the addition of adamantane carboxylic sodium salt, which was a competitive guest. The SHPs reassembled into core–shell structured micelles based on the hydrophilic–hydrophobic interaction of the amphiphilic Ada-CD2 monomer.

Reversible Self-Assembly of Backbone-Thermoresponsive Long Chain Hyperbranched Poly(N-Isopropyl Acrylamide)

In this paper, we mainly described the reversible self-assembly of a backbone-thermoresponsive, long-chain, hyperbranched poly(N-isopropyl acrylamide) (LCHBPNIPAM) in aqueous solution. Here, we revealed a reversible self-assembly behavior of LCHBPNIPAM aqueous solution derived from temperature. By controlling the temperature of LCHBPNIPAM aqueous solution, we tune the morphology of the LCHBPNIPAM self-assemblies. When the solution temperature increased from the room temperature to the lower critical solution temperature of PNIPAM segments, LCHBPNIPAM self-assembled from multi-compartment vesicles into solid micelles. The morphology of LCHBPNIPAM self-assemblies changed from solid micelles to multi-compartment vesicles again when the temperature decreased back to the room temperature. The size presented, at first, an increase, and then a decrease, tendency in the heating-cooling process. The above thermally-triggered self-assembly behavior of LCHBPNIPAM aqueous solution was investigated by dynamic/static light scattering, transmission electron microscopy, atomic force microscopy, fluorescence spectroscopy, 1H nuclear magnetic resonance in D2O, and attenuated total reflectance Fourier transform infrared spectroscopy. These results indicated that LCHBPNIPAM aqueous solution presents a reversible self-assembly process. The controlled release behaviors of doxorubicin from the vesicles and micelles formed by LCHBPNIPAM further proved the feasibility of these self-assemblies as the stimulus-responsive drug delivery system.

Probing into the Supramolecular Driving Force of an Amphiphilic β-Cyclodextrin Dimer in Various Solvents: Host–Guest Recognition or Hydrophilic–Hydrophobic Interaction?

Tuning of the morphology and size of supramolecular self-assemblies is of theoretical and practical significance. To date, supramolecular driving forces in different solvents remain unclear. In this study, we first synthesized an amphiphilic β-cyclodextrin (β-CD) dimer that consists of one hydrophobic ibuprofen (Ibu) and two hydrophilic β-CD moieties (i.e., Ibu-CD2). Ibu-CD2 possesses double supramolecular driving forces, namely, the host-guest recognition and hydrophilic-hydrophobic interaction. The host-guest interaction of Ibu-CD2 induced the formation of branched supramolecular polymers (SPs) in pure water, whereas the hydrophilic-hydrophobic interaction generated spherical or irregular micelles in water/organic mixtures. The SP size increased with the increase in Ibu-CD2 concentration in pure water. By contrast, the size of micelles decreased with the increase in volume ratio of water in mixtures.

Cyclodextrin-tunable reversible self-assembly of a thermoresponsive Y-shaped polymer

Tuning the reversible self-assembly process of stimuli-responsive topological polymers in solution has theoretical and practical significance. In this study, we covalently incorporated β-cyclodextrin (β-CD) onto a thermoresponsive Y-shaped polymer to investigate the influence of β-CD on the morphology, size and reversibility of self-assemblies. Transmission electron microscopy, atomic force microscopy, and dynamic light scattering results indicated that the morphology and size of the polymer self-assemblies present a good reversibility during the whole heating–cooling process. The self-assembly morphology gradually changed from dot-like micelles to noticeable core-corona-structured micelles, and finally back to dot-like micelles again. Meantime, the size of self-assemblies first increased from several tens of nanometers to hundreds of nanometers, and then decreased to get close to the initial value. The attached β-CD units have a pronounced regulation effect on the reversible self-assembly process. The corresponding mechanism is attributed to the abilities of β-CD itself to conduct inclusion complexation, induce intermolecular hydrogen bonding interaction and present steric hindrance. Our study has expanded a new idea to reversibly tune the morphology and size of stimulus-responsive topological polymer self-assemblies.

Synthesis and Self-assembly Behaviors of the ABC Miktoarm Star Terpolymer

The ABC miktoarm star terpolymer MPEG-PTHF (-PDMA) was synthesized by the combination of click chemistry, atom transfer radical polymerization (ATRP) and cationic ring opening polymerization (CROP). A block copolymer of poly(ethylene glycol) (PEG) and poly(N,N-dimethylaminoethyl methacrylate) (PDMA) which bears an azido at diblock junction (MPEG-N3 (-PDMA)) was first prepared by atom transfer radical polymerization. Then, an alkynyl-terminated narrow distributed polytetrahydrofuran (PTHF-Alk) was synthesized as another building block via cationic ring opening polymerization. The well-defined ABC miktoarm star shaped terpolymer was afforded by clicking MPEG-N, (-PDMA) onto the chain end of PTHF-Alk. The structure of the star terpolymer was characterized by the FTIR,NMR and SEC/MALLS. The self-assembly behavior of the polymer were investigated by dynamic light scattering (DLS) and transmission electron microscopy (TEM). This star shaped terpolymer consists of a hydrophobic PTHF chain, a hydrophiphilic PEG chain and another stimuli-responsive PDMA chain. It can self-assemble into micelles with different sizes and morphologies at various pH values, such as 5. 0,7. 4 and 9. 5. The micellar size also exhibits temperature-dependence at pH 7. 4 and 9. 5. The variation of size and morphology of the micelles with the solution pH and temperature is ascribed to the pH- and thermo-responsive properties of the PDMA block.