Alkaline-urea aqueous solvent system provides a novel and important approach for the utilization of polysaccharide. As one of the most important polysaccharide, chitosan can be well dissolved in this solvent system, and the resultant hydrogel material possesses unique and excellent properties. Thus the sound understanding of the gelation process is fundamentally important. However, current study of the gelation process is still limited due to the absence of direct observation and the lack of attention on the entire process. Here we show the entire gelation process of chitosan LiOH-urea aqueous system by aggregation-induced emission fluorescent imaging. Accompanied by other pseudo in situ investigations, we propose the mechanism of gelation process, focusing on the formation of junction points including hydrogen bonds and crystalline.
Sugars are abundant
natural sources existing in biological systems,
and bioactive saccharides have attracted much more attention in the
field of biochemistry and biomaterials. For better understanding of
the sugar-based biomaterials and biological sciences, aggregation-induced
emission luminogens (AIE-gens) have been widely employed for detection,
tracing, and imaging. This review covers the applications of AIE molecules
on sugar-based biomaterials by three parts, polysaccharide, oligosaccharide,
and monosaccharide, mainly focusing on saccharide detection, stimuli
response materials preparation, bioimaging, and study of the AIE mechanism.
These excellent works suggest the promising future of the sugar-based
AIE bioconjugates, considering that the naturally designed and elaborately
functionalized saccharides play discriminate roles in biological processes
and AIE-tagged species may work as an indicator in each case. However,
there are a lot of sugar-based biological species that have not been
touched, such as mucopolysaccharides and glycoproteins on the cell
surface and in the cell plasma. Based on these features, we enthusiastically
look forward to more glorious developments in this bright research
area.
Hydrogels with organized structure have attracted remarkable attentions for bio-related applications. Among the preparation of hierarchical hydrogel materials, fabrication of hydrogel with multi-layers is an important branch. Although the generation mechanism of layers had been fully discussed, sub-layer structure was not sufficiently studied. In this research, multi-layered chitosan hydrogel with oriented structure was constructed, and the formation mechanism of orientation was proposed, based on gelation behavior and entanglement of polymer chains in the hydrogel-solution system. Employing the layered-oriented characteristic, chitosan hydrogel materials with various shapes and structure can be designed and fabricated.
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