A new avenue to the synthesis of GAG-mimicking polymers highly promoting neural differentiation of embryonic stem cells.

A new strategy for the fabrication of glycosaminoglycan (GAG) analogs was proposed by copolymerizing the sulfonated unit and the glyco unit, 'splitted' from the sulfated saccharide building blocks of GAGs. The synthetic polymers can promote cell proliferation and neural differentiation of embryonic stem cells with the effects even better than those of heparin.

A fluorogenic probe with aggregation-induced emission characteristics for carboxylesterase assay through formation of supramolecular microfibers.

Herein, we report a novel fluorescent "light-up" probe useful for carboxylesterase assay that is based on a tetraphenylethylene derivative containing carboxylic ester groups. The specific cleavage of the carboxylic ester bonds by carboxylesterase results in the generation of a relatively hydrophobic moiety that self-assembles into supramolecular microfibers, thus giving rise to "turn-on" fluorescent signals. A high sensitivity towards carboxylesterase was achieved with a detection limit as low as 29 pM, which is much lower than the corresponding assays based on other fluorescent approaches.

6-O-sulfated chitosan promoting the neural differentiation of mouse embryonic stem cells.

Embryonic stem cells (ESCs) can be induced to differentiate into nerve cells, endowing them with potential applications in the treatment of neurological diseases and neural repair. In this work, we report for the first time that sulfated chitosan can promote the neural differentiation of ESCs. As a type of sulfated glycosaminoglycan analog, sulfated chitosan with well-defined sulfation sites and a controlled degree of sulfation (DS) were prepared through simple procedures and the influence of sulfated glycosaminoglycan on neural differentiation of ESCs was investigated. Compared with other sulfation sites, 6-O-sulfated chitosan showed the most optimal effects. By monitoring the expression level of neural differentiation markers using immunofluorescence staining and PCR, it was found that neural differentiation was better enhanced by increasing the DS of 6-O-sulfated chitosan. However, increasing the DS by introducing another sulfation site in addition to the 6-O site to chitosan did not promote neural differentiation as much as 6-O-sulfated chitosan, indicating that compared with DS, the sulfation site is more important. Additionally, the optimal concentration and incubation time of 6-O-sulfated chitosan were investigated. Together, our results indicate that the sulfate site and the molecular structure in a sulfated polysaccharide are very important for inducing the differentiation of ESCs. Our findings may help to highlight the role of sulfated polysaccharide in inducing the neural differentiation of ESCs.

Maintaining the pluripotency of mouse embryonic stem cells on gold nanoparticle layers with nanoscale but not microscale surface roughness.

Efficient control of the self-renewal and pluripotency maintenance of embryonic stem cell (ESC) is a prerequisite for translating stem cell technologies to clinical applications. Surface topography is one of the most important factors that regulates cell behaviors. In the present study, micro/nano topographical structures composed of a gold nanoparticle layer (GNPL) with nano-, sub-micro-, and microscale surface roughnesses were used to study the roles of these structures in regulating the behaviors of mouse ESCs (mESCs) under feeder-free conditions. The distinctive results from Oct-4 immunofluorescence staining and quantitative real-time polymerase chain reaction (qPCR) demonstrate that nanoscale and low sub-microscale surface roughnesses (Rq less than 392 nm) are conducive to the long-term maintenance of mESC pluripotency, while high sub-microscale and microscale surface roughnesses (Rq greater than 573 nm) result in a significant loss of mESC pluripotency and a faster undirectional differentiation, particularly in long-term culture. Moreover, the likely signalling cascades engaged in the topological sensing of mESCs were investigated and their role in affecting the maintenance of the long-term cell pluripotency was discussed by analyzing the expression of proteins related to E-cadherin mediated cell-cell adhesions and integrin-mediated focal adhesions (FAs). Additionally, the conclusions from MTT, cell morphology staining and alkaline phosphatase (ALP) activity assays show that the surface roughness can provide a potent regulatory signal for various mESC behaviors, including cell attachment, proliferation and osteoinduction.

Incorporation of tyrosine phosphate into tetraphenylethylene affords an amphiphilic molecule for alkaline phosphatase detection, hydrogelation and calcium mineralization.

Simple conjugation of tyrosine-phosphate with tetraphenylethylene generates a new amphiphile, which not only undergoes enzymatic dephosphorylation to generate a relative hydrophobic residue for alkaline phosphatase (ALP) detection with significant enhancement of the fluorescence signals, but also self-assembles in water to result in a novel supramolecular hydrogel with gelation-enhanced fluorescence emission features upon the changes of pH. In addition, the highly ordered micelle nanostructures self-assembled from this amphiphile exhibit the ability to serve as efficient templates to promote the nucleation and growth of calcium phosphate. Since amino acids and peptides are an important class of bioactive entities whose functions range from biomolecular recognition to supramolecular self-assembly, this study demonstrates the potential to generate an amphiphile with a novel molecular architecture from the TPE and amino acid conjugate with multifunctional properties.