Background: Electrospinning is a widely used technology that can produce scaffolds with high porosity and surface area for bone regeneration. However, the small pore sizes in electrospun scaffolds constrain cell growth and tissue-ingrowth. In this study, novel drugloading core-shell scaffolds were fabricated via electrospinning and freeze drying to facilitate the repair of tibia bone defects in rabbit models. Materials and Methods: The collagen core scaffolds were freeze-dried containing icariin (ICA)-loaded chitosan microspheres. The shell scaffolds were electrospun using collagen, polycaprolactone and hydroxyapatite materials to form CPH composite scaffolds with the ones containing ICA microspheres named CPHI. The core-shell scaffolds were then crosslinked by genipin. The morphology, microstructure, physical and mechanical properties of the scaffolds were assessed. Rat marrow mesenchymal stem cells from the wistar rat were cultured with the scaffolds. The cell adhesion and proliferation were analysed. Adult rabbit models with tibial plateau defects were used to evaluate the performance of these scaffolds in repairing the bone defects over 4 to 12 weeks. Results: The results reveal that the novel drug-loading core-shell scaffolds were successfully fabricated, which showed good physical and chemical properties and appropriate mechanical properties. Furthermore, excellent cells attachment was observed on the CPHI scaffolds. The results from radiography, micro-computed tomography, histological and immunohistochemical analysis demonstrated that abundant new bones were formed on the CPHI scaffolds. Conclusion: These new core-shell composite scaffolds have great potential for bone tissue engineering applications and may lead to effective bone regeneration and repair.
In this paper, a series of novel acridine derived bisbenzimidazolium macrocyclic fluorescent sensors were designed and synthesized. X-ray crystal structures demonstrated the self-assembly behavior of these cyclophanes in the solid state driven by hydrogen bond and π-π interactions. Anion binding studies of these sensors revealed a significant effect of the macrocyclic size and rigidity for H2PO4(-) sensing via the obvious turn-on as well as bathochromic-shift in fluorescence emission. Different cavity size or rigidity of the sensors showed different bathochromic-shifts (from 36 to 126 nm) in fluorescence emission induced by H2PO4(-), which resulted in significant color changes of fluorescence from blue to orange red, orange, green and blue-green respectively. The unique fluorescence response toward H2PO4(-) may be attributed to H2PO4(-)-induced assembly of sensors forming the excimer between two acridine rings to a different extent.
Vitrimer is a new reprocessable thermosetting polymer based on the exchange of dynamic covalent bonds. However, the vitrimer reported in the literatures can usually be reprocessed at very high temperature, while the vitrimer reprocessed at a relatively low temperature exhibits poor mechanical properties. It is still a great challenge to design mechanically robust vitrimer with a moderate reprocessing temperature. Herein, a polyurethane‐urea vitrimer elastomer including N,N′‐diaryl urea with electron donating effect is first reported, and it possesses a moderately remoldable temperature (100 °C, 23% of soft segments content) and robust mechanic al performance. The associative exchange mechanism of N,N′‐diaryl urea with electron donating effect is investigated by the stress relaxation, variable temperature Fourier transform infrared spectra of elastomer, as well as nuclear magnetic resonance spectra, and Fourier transform infrared spectra based on model compounds. Besides, for the preparation of polyurethane‐urea vitrimer elastomers, all monomers are directly from commercial raw materials, thereby providing a possibility of large‐scale production for the polyurethane‐urea vitrimers.
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