Synthesis of Poly(ε‐lysine)‐Grafted Dextrans and Their pH‐ and Thermosensitive Hydrogelation with Cyclodextrins

Abstract

To give pH sensitivity to a thermoreversible supramolecular-structured hydrogel system, poly(epsilon-lysine) (PL), as a cationic polymer, was grafted to dextran and used for inclusion complexation with alpha-cyclodextrins (alpha-CDs). The synthesized graft copolymer was characterized by 1H NMR spectroscopy, and the hydrogel formation was confirmed by X-ray diffraction and solid-state 13C NMR analysis. The hydrogelation was induced from a phase-separated structure of hydrated dextrans and hydrophobically aggregated inclusion complexes in buffer solution at pH 10.0. The prepared hydrogels showed thermoreversible gel-sol transitions as well as pH-sensitive phase transitions, which were recorded by the changes in UV/Vis transmittance. A rapid phase transition from gel to sol was observed upon decreasing the pH value to 4.0, which resulted from the dissociation process between the protonated guest polymer and alpha-CDs. The stimuli-responsive physical properties of the hydrogels were improved by modulating the degree of substitution of the grafted PL and the combination with alpha-CDs.

Cyclodextrin‐Based Supramolecular Assemblies and Hydrogels: Recent Advances and Future Perspectives

“…The hydrophobic interactions within the networks confer long‐term sustained release of various drug molecules, proteins, and amino acids where loading of the payload could be implemented under mild conditions (i.e., physiological pH and room temperature) and prior to gelation, which is particularly advantageous in the field of tissue engineering. In addition to thermo‐responsiveness, pH‐, photo‐, and redox‐responsiveness have also been incorporated into these systems by careful selection of the polymers. Although these systems may serve as scaffolds for sustained release systems, their true potential is yet to be realized, with many reports still in the in vitro stage using (model) drugs and proteins .…”

Effects of Dronedarone Started Rapidly After Amiodarone Discontinuation

“…The protonation degree of the amine groups of ε‐PL (p K a ≈ 9.0)55, 56 was adjusted with concentrated HCl from a naturally basic condition (pH 8.5), to neutral, and acidic (pH 4). With ε‐PL at pH 8.5, its protonation degree was expected to be very slightly, and ζ of the β‐carotene nanoparticles increased from −20 to −8 mV (Tab.…”

Cyclodextrin-Mediated Hierarchical Self-Assembly and Its Potential in Drug Delivery Applications

“…109,110 In an attempt to produce stiffer CD-PPRTX hydrogels, while decreasing the total weight concentrations of the starting components, the researchers also used interpeptide hydrogen bonding as an additional associative force. 111,112 For example, Dong et al demonstrated that usage of diblock copolymers containing PEG with molecular weight around 5 kDa and biodegradable polypeptide poly(L-glutamic acid) (PLG) leads to aCD-PPRTX hydrogels with remarkably high elastic storage modulus (G 0~1 0 4 Pa at 10 wt% vs. 10 3 Pa at 15 wt% for conventional amphiphilic hydrogels) and long-loaded doxorubicin release times. 111 This gel strengthening phenomenon was ascribed to extra hydrogen bonding between the PLG blocks under acidic pH and its synergy with polypseudorotaxane hydrogen bond-driven associations.…”