Rheological, microstructural, andin vitrocharacterization of hybrid chitosan-polylactic acid/hydroxyapatite composites

Bioactive injectable triple acting thermosensitive hydrogel enriched with nano-hydroxyapatite for bone regeneration: in-vitro characterization, Saos-2 cell line cell viability and osteogenic markers evaluation

Hydrogels forming in-situ have gained great attention in the area of bone tissue engineering recently, they were also showed to be a good and less invasive alternative to surgically applied ones. The primal focus of this study was to prepare chitosan-glycerol phosphate thermosensitive hydrogel formed in-situ and loaded with risedronate (bone resorption inhibitor) in an easy way with no requirement of complicated processes or large number of equipment. Then we investigated its effectiveness for bone regeneration. In-situ forming hydrogels were prepared using chitosan cross-linked with glycerol phosphate and loaded with risedronate and nano-hydroxyapatite as bone cement. The prepared hydrogels were characterized by analyzing their gelation time at 37 °C, % porosity, swelling index, in-vitro degradation, rheological properties, and in-vitro drug release. Results showed that the in-situ hydrogels prepared using 2.5% (w/v) chitosan cross-linked with 50% (w/v) glycerol phosphate in the ratio (9:1, v/v) reinforced with 20 mg/mL and nano-hydroxyapatite possessed the most sustained drug release profile. This optimized formulation was further evaluated using DSC and FTIR studies, in addition to their morphological properties using scanning electron microscopy. The effect on Saos-2 cell line viability was evaluated also using MTT assay on the optimized hydrogel formulation in addition to their action on cell proliferation using fluorescence microscope. Moreover, calcium deposition on the hydrogel and alkaline phosphatase activity were evaluated. Risedronate-nano-hydroxyapatite loaded hydrogels significantly enhanced the Saos-2 cell proliferation in addition to enhanced alkaline phosphatase activity and calcium deposition. Such results suggest that risedronate-nano-hydroxyapatite loaded hydrogels present great biocompatibility for bone regeneration. Proliferation of cells, as well as deposition of mineral on the hydrogel, was an evidence of the biocompatible nature of the hydrogel. This hydrogel formed in-situ present a good less invasive alternative for bone tissue engineering.

Fabrication and characterization of melt-blended polylactide-chitin composites and their foams

This study details the fabrication and foaming of melt-blended polylactide (PLA) and chitin composites. The chitin used for compounding was as-received, as chitin nanowhiskers and as chitin nanowhiskers with a compatibilizing agent. The chitin nanowhiskers were produced by an acid-hydrolysis technique and their morphology was examined with transmission electron microscopy. The composite morphology was characterized with scanning electron microscopy and was related to the observed thermal, rheological, and mechanical behaviors of the composites. Chitin was found to decrease the thermal stability of the composites. Addition of chitin was also found to reduce the viscosity of the composites, which is believed to be because of the hydrolysis of PLA during melt blending of chitin in suspension. The stiffness of the composites was found to increase with increasing chitin content while the strength was found to decrease. Porous PLA—chitin composites were produced by a two-step batch-foaming technique, and the expansion behavior was correlated with the visco-elastic observations. The statistical significance of chitin type and composition dependence on the mechanical properties and foam morphologies were evaluated.

Construction of a fluorescent nanostructured chitosan-hydroxyapatite scaffold by nanocrystallon induced biomimetic mineralization and its cell biocompatibility

Biomaterial surfaces and their nanostructures can significantly influence cell growth and viability. Thus, manipulating surface characteristics of scaffolds can be a potential strategy to control cell functions for stem cell tissue engineering. In this study, in order to construct a hydroxyapatite (HAp) coated genipin-chitosan conjugation scaffold (HGCCS) with a well-defined HAp nanostructured surface, we have developed a simple and controllable approach that allows construction of a two-level, three-dimensional (3D) networked structure to provide sufficient calcium source and achieve desired mechanical function and mass transport (permeability and diffusion) properties. Using a nontoxic cross-linker (genipin) and a nanocrystallon induced biomimetic mineralization method, we first assembled a layer of HAp network-like nanostructure on a 3D porous chitosan-based framework. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) analysis confirm that the continuous network-like nanostructure on the channel surface of the HGCCS is composed of crystalline HAp. Compressive testing demonstrated that the strength of the HGCCS is apparently enhanced because of the strong cross-linking of genipin and the resulting reinforcement of the HAp nanonetwork. The fluorescence properties of genipin-chitosan conjugation for convenient monitoring of the 3D porous scaffold biodegradability and cell localization in the scaffold was specifically explored using confocal laser scanning microscopy (CLSM). Furthermore, through scanning electron microscope (SEM) observation and immunofluorescence measurements of F-actin, we found that the HAp network-like nanostructure on the surface of the HGCCS can influence the morphology and integrin-mediated cytoskeleton organization of rat bone marrow-derived mesenchymal stem cells (BMSCs). Based on cell proliferation assays, rat BMSCs tend to have higher viability on HGCCS in vitro. The results of this study suggest that the fluorescent two-level 3D nanostructured chitosan-HAp scaffold will be a promising scaffold for bone tissue engineering application.