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Abstract To investigate the effect and mechanism of chitosan nanoparticles (CSNPs) on the germination and seedling growth of wheat (Triticum aestivum L.), we conducted systematic research on the impact of different concentrations (1–100 μg/mL) of CSNPs and chitosan (CS). The result of energy-dispersive spectroscopy (EDS) and confocal laser scanning microscopy (CLSM) showed that adsorption of CSNPs on the surface of wheat seeds was higher than that of CS. CSNPs had growth promoting effect at a lower concentration (5 μg/mL) compared with CS (50 μg/mL). In addition, the application of 5 μg/mL CSNPs induced the auxin-related gene expression, accelerated indole-3-acetic acid (IAA) biosynthesis and transport, and reduced IAA oxidase activity resulting in the increase of IAA concentration in wheat shoots and roots. The results suggest that CSNPs have positive effect on seed germination and seedling growth of wheat at a lower concentration than CS due to higher adsorption on the surface of wheat seeds. Highlights • CSNPs could promote growth at a lower concentration about 10 fold than CS. • CSNPs promote wheat growth by activating IAA signaling pathway. • The CSNPs adsorption is stronger than that of CS on the surface of wheat seed by EDS and CLSM. [ABSTRACT FROM AUTHOR]

Background: In the process of bone defective reparation and engineered bone tissue construction, osteoblasts are adhered to the surface of the scaffold materials and impart the external mechanical load to the osteoblasts. So, the dynamic mechanical property of the scaffolds play an important role in the bone tissue repair and it is valuable to research. Material type and the architectural design of scaffolds are also important to facilitate cell and tissue growth. The aim of this study was to prepare a kind of material with good pore connectivity and analyze its dynamic mechanical property.Methods: Fabrication and characterization of micro-hydroxyapatite(m-HA)/chitosan(CS) polymer composite scaffolds with well interconnected spherical pore architectures were reports. Micro-HA was prepared by being calcined and ball milled. Paraffin spheres in the range of 160-330 µm were fabricated with a dispersion method and used as the porogen in the fabrication of the scaffolds. Polymer scaffolds were fabricated by the technique of compression molding and particulate leaching method. The effects of the porogen content on the properties of the scaffolds were studied.Results: With the increase of porogen, the pore of the scaffolds increased and became interconnected. Cyclic loading of three scaffolds were tested with 10 % strain under four levels of loading frequency, 0.1, 0.5, 1 and 1.5 Hz. The porous composite scaffolds exhibited a viscosity-elastic behaviour with a maximum stress of 3-4 kPa. At each frequency, modulus value is decreased with the paraffin microspheres content, but there was no significance difference in the peak stress of the three samples. All the samples tested displayed clear hysteresis loops. There was no significance difference in the peak hysteresis of the three samples, and the hysteresis difference values between the sixth compression cycle and the initial cycle for three samples was similar, with no statistically significant differences.Conclusions: Micro-HA/CS composite scaffolds with interconnected spherical macropores were fabricated using pherical paraffin as porogen. The porous composite scaffolds exhibited a viscosity-elastic behaviour with good repeatability. It is benefit to study the influence of the mechanical load on the cell of the scaffold. [ABSTRACT FROM AUTHOR]

Introduction: In this study, the silk fibroin blended constructs were produced, scaffold performances of different kinds of scaffold were analyzed, and the better type for tissue engineering was optimized. Methods: The silk fibroin/collagen (SF/C) and silk fibroin/chitosan (SF/CS) were made using a freeze-drying technique, porosity, water absorption expansion rate, mechanical properties and pore size of different scaffold was detected. Bone marrow mesenchymal stem cells (BMSCs) of 4-week-old male Wistar rats were separated by density gradient centrifugation, third generation BMSCs were seeded onto scaffolds, cultured 14 days, proliferation and metabolize of cells were detected in different time using the thiazolyl blue tetrazolium bromide (MTT) assay method, and cell morphology and distribution were observed by histological analysis and scanning electron microscopy (SEM). Results: Porosity, water absorption expansion rate and Young's modulus of SF/C were significantly higher than SF/CS ( p < 0.05); pore size of SF/C and SF/CS was 103 ± 12 and 76 ± 11 μm and had no significant differences between two types ( p > 0.05); MTT results showed that the metabolism of cells in the SF/C was better than SF/CS; after cultivation for 14 days, in the inner zone of scaffolds, cells staining were little or absent from SF/CS, lots of cells staining were existing in SF/C; pore size was consistent, holes communicated with each other better, stem cells grew well inside the scaffolds, extended fully and secreted much extracellular matrix under SEM in SF/C scaffold; internal structure of SF/CS was disorder, holes size were not consistent, and did not communicated with each other and cells were partly dead. Conclusion: Compared with SF/CS, SF/C scaffold showed better porosity, water absorption expansion rate, elasticity modulus and pore size, cells grow well inside the scaffolds, and was more suitable for tissue engineering. [ABSTRACT FROM AUTHOR]

• Association between quaternary chitosan and alginate were regulated via hydration. • Less hydrated counter anion Cl− bound more strongly to positive groups on polymer. • There was a pH transition point of thermal change of association. • Solution's pH had more effect on the hydration of polymers than counter ions. Studies on interactions between oppositely charged polysaccharides have gathered great interest. We proposed that the association between oppositely charged polymers could be regulated via hydration. A comparison study was carried out by using quaternary chitosan with different counterions(Cl−, Ac−, OH−) and sodium alginate. The results showed that the association between quaternary chitosan with less hydrated counter anion Cl− and sodium alginate was weaker than that between quaternary chitosan with more hydrated counter anion Ac− and sodium alginate. There was a pH transition point of thermal change of association between oppositely charged polymers, as the solution's pH had more effect on the hydration of polymers than counter ions. Further studies showed that a fraction of Cl− was still attracted by polycation in the complex and competed with the interaction of polyanion after complexation. The competitive combination was critical for the property (such as self healing behavior) of the carbohydrate polymer complex. [ABSTRACT FROM AUTHOR]

The property of collagen–chitosan porous scaffold varies according to cross-linking density and scaffold composition. This study was designed to compare the properties of collagen–chitosan porous scaffolds cross-linked with γ-irradiation and carbodiimide (CAR) for the first time. Eleven sets of collagen–chitosan scaffolds containing different concentrations of chitosan at a 5% increasing gradient were fabricated. Fourier transform infrared spectroscopy was performed to confirm the success of cross-linking in the scaffolds. The scaffold morphology was evaluated under scanning electron microscope (SEM). SEM revealed that chitosan was an indispensable material for the fabrication of γ-ray irradiation scaffold. The microstructure of γ-ray irradiation scaffold was less stable than those of alternative scaffolds. Based upon swelling ratio, porosity factor, and collagenase degradation, γ-ray irradiation scaffold was less stable than CAR and 25% proportion of chitosan scaffolds. Mechanical property determines the orientation in γ-irradiation and CAR scaffold.In vitrodegradation test indicated that γ-irradiation and CAR cross-linking can elevate the scaffold biocompatibility. Compared with γ-ray irradiation, CAR cross-linked scaffold containing 25% chitosan can more significantly enhance the bio-stability and biocompatibility of collagen–chitosan scaffolds. CAR cross-linked scaffold may be the best choice for future tissue engineering. [ABSTRACT FROM PUBLISHER]