Cationic quaternized chitosan bioconjugates with aggregation-induced emission features for cell imaging.

Fluorescent bioprobs are in urgent demand to monitor important biological events in biomedicine. However, the aggregation-caused quenching character, high toxicity, water-insolubility and easy leakage property of conventional small molecular dyes hinder the development in this area. In this work, an aggregation-induced emission (AIE) bioconjugate was synthesised by labeling tetraphenylethylene (TPE) to quaternized chitosan (QCS). The TPE-QCS bioconjugate emits strong fluorescence even in solid state, and is cationic and water-soluble over a wide range of pH values. The TPE-QCS aqueous solution stained HeLa cells by dose- and time-depent manner and imaged living cells with bright fluorescence. Futhermore, the cationic bioconjugate was readily internalized by cells through endocytosis, and further aggragated to large sizes and adhered to negatively charged organelle membranes inside cells achieving fluorescent cell imaging with fluorescence enhancement and leakage-free staining. The AIE-active TPE-QCS with cationic nature, good water-solubility over a wide pH range and unique cell imaging properties could trace HeLa cells for as long as 23 passages, that was obviously superior to existing commercial cellular tracer, so has promising application prospects as ultra long-term tracer in biomedical field.

Highly mineralized chitosan-based material with large size, gradient mineral distribution and hierarchical structure.

Nature materials constituted with organic and inorganic components have hierarchical structure and superior performance. Although a variety of techniques have been developed to mimic microstructure and properties of natural mineralized materials, facile and rapid fabrication of large-size bulk materials with high calcium content under ambient conditions still remains a major challenge. Here, we present a feasible and versatile route to a highly mineralized material with an in situ preparation method where gelation and mineralization occur simultaneously. Meanwhile, hierarchically ordered hydrogel microstructures are formed during the gelation, and controllable inorganic gradient distribution forms along with mineralization spontaneously. With the achievement of high mineral content by the assistance of urea, this fabrication route is facile and efficient, only taking several hours to complete the gelation and mineralization, and large-scale materials are prepared readily. This chitosan matrix-directed mineralization represents a rational and promising strategy for fast fabrication of highly mineralized material with hierarchical structure on a large scale, and the chitosan-based mineralized material has great potential for applications in bone repairing and tissue engineering.

Construction of ordered structure in polysaccharide hydrogel: A review.

Hydrogels are three-dimensional, hydrophilic, polymeric networks, held together by a variety of physical or chemical crosslinks. Among the numerous polymers that can be employed to fabricate hydrogel, polysaccharides have attracted enormous attention due to their peculiar properties that make them suitable for various applications. Compared with homogeneous hydrogels, hydrogels with ordered structures on various length scales are endowed with excellent properties and promising applications in materials science. In the present review, a wide range of techniques were introduced and discussed, which had been utilized to construct ordered hierarchical structures in polysaccharide hydrogels. These techniques focused on the construction of multi-layered and orientated structure, which are two typical and very important forms of hierarchical structure.