Thermoresponsive hydrogels in biomedical applications.

Graphene-polymer nanocomposites for structural and functional applications

Hydrogels in a historical perspective: from simple networks to smart materials.

Sonication-induced gelation of silk fibroin for cell encapsulation.

In situ gelling hydrogels for pharmaceutical and biomedical applications.

Synthesis, characterization and controlled drug release of thermosensitive IPN-PNIPAAm hydrogels.

Synthesis and characterization of partially biodegradable, temperature and pH sensitive Dex-MA/PNIPAAm hydrogels.

In this study, the effect of the level of crosslinking on the properties of poly(N-isopropylacrylamide) (PNIPAAm) hydrogels was investigated in terms of their lower critical solution temperature (LCST), interior morphology, equilibrium swelling, and deswelling and swelling kinetics. The thermal analysis showed that PNIPAAm hydrogels, having a wide range of crosslinking levels, exhibited almost the same LCSTs, and this was different from what the conventional theory would have predicted. Scanning electron micrographs revealed that the interior network structure of the PNIPAAm matrix became more porous with an increase in the level of crosslinking. This more porous matrix provided numerous water channels for water diffusion in or out of the matrix and, therefore, an improved response rate to the external temperature changes during the deswelling process and the swelling process.

Effect of the crosslinking level on the properties of temperature‐sensitive poly(N‐isopropylacrylamide) hydrogels

The dextran-allyl isocyanate/poly(N-iso-propylacrylamide) (Dex-AI/PNIPAAm) hydrogel was designed and prepared by copolymerization of the modified dextran with N-isopropylacrylamide(NIPAAm). Thisnovel Dex-AI/PNIPAAm hydrogel is biodegradable and intelligent due to its biodegradable dextran linkage and thermosensitive PNIPAAm moiety. With an increase in dextran content, it exhibits the increased lower critical solution temperature (LCST) and decreased porous microstructure. Also, the thermosensitivity of this hydrogel is also controllable and adjustable depending on the different compositions.

Novel biodegradable and thermosensitive Dex-AI/PNIPAAm hydrogel

A partially biodegradable and thermosensitive hybrid hydrogel network (DAN series) based on dextran-allylisocyanate (Dex-AI) and poly(N-isopropylacrylamide) (PNIPAAm) was synthesized via UV photocrosslinking. These hybrid hydrogels were characterized in terms of their chemical structure, thermal, mechanical, morphological and temperature-induced swelling properties. The effect of the composition ratio of Dex-AI to PNIPAAm on such properties were examined. The differential scanning calorimetry data show that this Dex-AI/PNIPAAm hybrid network has an increased lower critical solution temperature (LCST) and glass transition temperature (Tg) with an increase in the Dex-AI content. The interior morphology of these hybrid hydrogels revealed a decreased porous microstructure with an increase in the Dex-AI content in the hybrid network. Furthermore, if the Dex-AI composition became too high, a distinctive network structure with two different microporous structures appeared. The mechanical properties of these hybrid hydrogels also increased with an increase in the Dex-AI content. The temperature dependence of the swelling ratio, the deswelling kinetics as well as the reswelling kinetics was also characterized by gravimetric method. When comparing with a normal PNIPAAm hydrogel, these Dex-AI/PNIPAAm hybrid networks, due to the presence of Dex-AI moiety, also show improved temperature-induced intelligent properties, such as the faster and controllable response dynamics, which may find promising applications in a wide variety of fields, such as biomedical and bioengineering fields.

Da-Qing Wu

Papers

Synthesis, characterization and controlled drug release of thermosensitive IPN-PNIPAAm hydrogels.

Synthesis and characterization of partially biodegradable, temperature and pH sensitive Dex-MA/PNIPAAm hydrogels.

Effect of the crosslinking level on the properties of temperature‐sensitive poly(N‐isopropylacrylamide) hydrogels

Novel biodegradable and thermosensitive Dex-AI/PNIPAAm hydrogel

Synthesis and characterization of partially biodegradable and thermosensitive hydrogel.