ABSTRACT
A novel redox-induced shape-memory polymer (SMP) is prepared by crosslinking ß-cyclodextrin modified chitosan (ß-CD-CS) and ferrocene modified branched ethylene imine polymer (Fc-PEI). The resulting ß-CD-CS/Fc-PEI contains two crosslinks: reversible redox-sensitive ß-CD-Fc inclusion complexes serving as reversible phases, and covalent crosslinks serving as fixing phases. It is shown that this material can be processed into temporary shapes as needed in the reduced state and recovers its initial shape after oxidation. The recovery ratio and the fixity ratio are both above 70%. Furthermore, after entrapping glucose oxidase (GOD) in the system, the material shows a shape memory effect in response to glucose. The recovery ratio and the fixity ratio are also above 70%.
Subject(s)
Glucose/pharmacology , Polymers/chemical synthesis , Chitosan/chemistry , Deuterium Oxide/chemistry , Ferrous Compounds/chemistry , Magnetic Resonance Spectroscopy , Mechanical Phenomena , Metallocenes , Oxidation-Reduction/drug effects , Polyethyleneimine/chemistry , Polymers/chemistry , beta-Cyclodextrins/chemistryABSTRACT
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.
Subject(s)
Micelles , Polymers/chemistry , Surface-Active Agents/chemistry , alpha-Cyclodextrins/chemistry , Benzoic Acid/chemistry , Models, Theoretical , Trimethyl Ammonium Compounds/chemistry , Ultraviolet RaysABSTRACT
A novel pH sensitive shape-memory polymer (SMP) is prepared by cross-linking the ß-cyclodextrin modified alginate (ß-CD-Alg) and diethylenetriamine modified alginate (DETA-Alg): The pH reversible ß-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.
Subject(s)
Alginates/chemistry , Biocompatible Materials/chemistry , Polymers/chemistry , Cross-Linking Reagents/chemistry , Hydrogen-Ion Concentration , Temperature , beta-Cyclodextrins/chemistryABSTRACT
This article studies the self-assembly of alginate-graft-poly(ethylene glycol) (Alg-g-PEG) and α-cyclodextrin (α-CD) in aqueous solution. It was found that they could form hollow spheres because of the formation of coil-rod Alg-g-PEG/α-CD inclusion complexes. In these Alg-g-PEG/α-CD complexes, the α-CDs are stacked along the PEG side chains to form a rod block, and alginate main chains act as a coil block. More rod-like blocks in Alg-g-PEG/α-CD favor the formation of small assemblies. The assemblies of Alg-g-PEG/α-CD show a dependence on concentration, temperature, pH, and salt concentration. At low concentration (below 0.125%) or high temperature (above 32 °C), Alg-g-PEG/α-CD particles were unstable and disrupted. Increasing the salt or decreasing the pH resulted in the aggregation of Alg-g-mPEG/α-CD particles, as detected by the increase in the recorded hydrodynamic diameter (D(h)).
Subject(s)
Alginates/chemistry , Nanospheres/chemistry , Polyethylene Glycols/chemistry , alpha-Cyclodextrins/chemistry , Glucuronic Acid/chemistry , Hexuronic Acids/chemistry , Molecular Structure , Particle Size , Porosity , Surface PropertiesABSTRACT
This paper describes the self-assembly of rod-coil inclusion complexes, polyethylenimine-poly(ethylene glycol)-α-cyclodextrin (PEI-PEG-α-CD). It is demonstrated that α-CDs should exclusively thread on the PEG block in PEI-PEG copolymers and the resulting complexes have both rigid block (PEG-α-CD) and coil block (protonated PEI). By varying the rigid block fraction, aggregates with hollow spheres or rod-like particles could be formed simply by self-assembly in aqueous solution.
