Min-Min Fan

pH-Induced Shape-Memory Polymers

A novel pH sensitive shape-memory polymer (SMP) is prepared by cross-linking the β-cyclodextrin modified alginate (β-CD-Alg) and diethylenetriamine modified alginate (DETA-Alg): The pH reversible β-CD-DETA inclusion complexes serve as a reversible phase, and the cross-linked alginate chains serve as a fixing phase. It is shown that this material can be processed into temporary shape as we needs at pH 11.5 and recover to its initial shape at pH 7. The recovery ratio and the fixity ratio were 95.7 ± 0.9% and 94.8 ± 1.1%, respectively. Furthermore, this material showed good degradability and biocompatibility. Because the shape transition pH value is quite close to that of our body fluid and this pH triggered shape-memory effect is convenient and safe to use, this material has a high potential for medical application.

Self-assembly hollow nanosphere for enzyme encapsulation

This paper studies a kind of self-assembled hollow nanosphere for L-asparaginase encapsulation, and it was found that the hollow spheres not only enable a high loading of enzyme, but also show semi-permeability which could prevent the enzyme from leaving while allowing substrates and products to pass through to maintain the enzyme activity, and the encapsulated L-asparaginase showed significantly higher stability.

Supramolecular Network Based on the Self‐Assembly of γ‐Cyclodextrin with Poly(ethylene glycol) and its Shape Memory Effect

A novel supramolecular network has been prepared based on the formation of inclusion complexes between γ-cyclodextrin and poly(ethylene glycol), in which the PEG chains are interlocked by γ-CD rings. This PEG/γ-CD network exhibits good shape memory behavior because of the crosslinked structure. The crosslinked PEG/γ-CD inclusion complexes and PEG crystallites account for the fixing phase and reversible phase, respectively. The characteristics of the materials have been investigated by (1) H NMR spectroscopy, XRD, DSC, DMA, viscosity tests, and swelling measurements.

Encapsulation studies and selective membrane permeability properties of self-assembly hollow nanospheres

This paper presents a kind of self-assembled hollow nanosphere for enzyme encapsulation. The enzyme molecules were encapsulated in hollow spheres directly in aqueous solution through the self-assembly of rod-coil Alg-g-PEG and α-CDs complexes. These Alg-g-PEG/α-CD hollow spheres showed semi-permeability which could prevent big enzyme molecules from leaving while allowing small substrates and products to pass through to maintain the enzyme activity. The permeability properties of Alg-g-PEG/α-CD hollow nanospheres were investigated by encapsulating different probes. The results showed that the molar mass cutoff (MMCO) of these hollow nanospheres was between 20 and 40 kDa. The encapsulation capability of Alg-g-PEG/α-CD hollow nanospheres was also investigated, the results indicated a maximal values for L-asparaginase encapsulation. Furthermore, the encapsulation behavior for L-asparaginase showed PEG graft density (GD) dependence.

pH-responsive polymer-drug conjugates as multifunctional micelles for cancer-drug delivery

We developed a novel linear pH-sensitive conjugate methoxy poly(ethylene glycol)-4β-aminopodophyllotoxin (mPEG-NPOD-I) by a covalently linked 4β-aminopodophyllotoxin (NPOD) and PEG via imine bond, which was amphiphilic and self-assembled to micelles in an aqueous solution. The mPEG-NPOD-I micelles simultaneously served as an anticancer drug conjugate and as drug carriers. As a drug conjugate, mPEG-NPOD-I showed a significantly faster NPOD release at a mildly acidic pH of 5.0 and 4.0 than a physiological pH of 7.4. Notably, it was confirmed that this drug conjugate could efficiently deliver NPOD to the nuclei of the tumor cells and led to much more cytotoxic effects to A549, Hela, and HepG2 cancer cells than the parent NPOD. The half maximal inhibitory concentration (IC₅₀) of mPEG-NPOD-I was about one order magnitude lower than that of the NPOD. In vivo, mPEG-NPOD-I reduced the size of the tumors significantly, and the biodistribution studies indicated that this drug conjugate could selectively accumulate in tumor tissues. As drug carriers, the mPEG-NPOD-I micelles encapsulated hydrophobic PTX with drug-loading efficiencies of 57% and drug-loading content of 16%. The loaded PTX also showed pH-triggered fast release behavior, and good additive cytotoxicity effect was observed for the PEG-NPOD-I/PTX. We are convinced that these multifunctional drug conjugate micelles have tremendous potential for targeted cancer therapy.

Self-Assembly Pluronic and β-Cyclodextrin to Hollow Nanospheres for Enhanced Gene Delivery.

This paper studies a kind of hollow nanospheres prepared by self-assembly β-cyclodextrins (β-CDs) and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (pluronic F127) for gene delivery. It was found that this kind of hollow nanospheres enable load PEI10K/DNA and the resulting F127NH2 βCD/(PEI10K/DNA) with 0.08 µg/well DNA display equal or higher gene delivery capability compared to PEI10K/DNA with 1 µg/well DNA in the absence or presence of serum. The cytotoxicity of the nanospheres was over 100 times lower than that of PEI10K.

Photoreversible polymer-surfactant micelles using the molecular recognition of α-cyclodextrin.

Photoreversible micelles were achieved by a combination of commercially available components sodium alginate (Alg), tetradecyltrimethylammonium bromide (TTAB), α-cyclodextrin (α-CD), and 4-(phenylazo)benzoic acid (PBA). Under visible light irradiation, α-CD interacted more favorably with PBA than with alkyl chains of TTAB. Therefore, polymer-surfactant micelles were formed by the self-assembly of Alg and TTAB through electrostatic attraction. After UV irradiation, micelles were disrupted because PBA in the cis form lost its ability to complex with α-CD, and then the latter was interacted with TTAB to prevent the association of alkyl chains of TTAB. On alternating irradiation of this quaternary system with UV and visible light, this reversible micellization process can be recycled many times.

Synthesis of biocompatible hybrid magnetic hollow spheres based on encapsulation strategy

A kind of novel magnetic hollow spheres was prepared by encapsulating magnetofluid into polymeric hollow spheres. Polymeric hollow nanospheres were constructed by self-assembly of rod-coil complexes, in which the rod-like segments were formed by inclusion of α-cyclodextrins (α-CD) and grafting poly(ethylene glycol) (PEG) chains of chitosan-graft-PEG (CS-g-PEG). Structural characteristics of CS-g-PEG/α-CD hollow spheres were investigated in detail by NMR, XRD, TEM, etc. Furthermore, those hollow spheres showed a pH responsive property which induced a considerable change of their radius. Magnetofluid was physically entrapped into the empty domain while hollow spheres were formed, it was found that the hollow spheres can encapsulate large quantities of magnetofluid and the encapsulated magnetofluid still possess magnetic responsiveness properties. We expect that this strategy may be served as a novel and more straightforward approach to obtain magnetic hollow spheres for biomedical application.

Supramolecular assembly of cyclodextrin-based nanospheres for gene delivery

Summary Polymeric hollow nanospheres were prepared by self-assembly of rod-coil complexes, in which the rod-like segments were formed by inclusion complexes of β -cyclodextrins ( β -CDs) and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) diamines. Nanospheres encapsulating DNA or polyethylenimine/DNA (PEI/DNA) were synthesized and characterized in terms of their supramolecular structures, DNA binding and condensation ability, cytotoxicity, and in vitro gene transfection efficiency in HepG2 cells.

An insight into the influence of hydrogen bond acceptors on cellulose/1-allyl-3-methyl imidazolium chloride solution

Although ionic liquids have been well established as effective solvents for the dissolution and processing of natural cellulose fibers, the detailed dissolution mechanism at the molecular level still remains unclear. Herein, the turbidimetric measurement showed that the solubility of cellulose in 1-allyl-3-methyl imidazolium chloride (AmimCl) decreased with increasing temperature. The temperature dependence of the OH stretching vibration band of cellulose in AmimCl was investigated by infrared spectroscopy. The interaction between AmimCl and different hydrogen bond acceptors were investigated by turbidimetry and NMR spectroscopy, which indicated that the excellent compatibility of the hydrogen bond acceptors with AmimCl provides more interaction sites for the hydroxyl groups of the cellulose. In addition, ionic liquids with a similar anionic structure of hydrogen bond acceptors have been synthesized. This study provides a green and safe guide for the preparation of ionic liquids with excellent solubility of cellulose.