beta-TCP/MCPM-based premixed calcium phosphate cements.

Novel premixed calcium phosphate cements (CPCs) were prepared by combining cement liquids comprised of glycerol or polyethylene glycol with CPC powders that consisted of beta-tricalcium phosphate (beta-TCP) and monocalcium phosphate monohydrate (MCPM). Changing the powder to liquid mass ratio enabled the setting time to be regulated, and improved the compressive strength of the CPCs. Although some ratios of the new premixed CPCs had long setting times, these ranged from 12.4 to 27.8 min which is much shorter than the hour or more reported previously for a premixed CPC. The premixed CPCs had tolerable washout resistance before final setting, and the cements had strengths matching that of cancellous bone (5-10 MPa); their maximum compressive strength was up to 12 MPa. The inflammatory response around the premixed CPCs implanted in the subcutaneous tissue in rabbits was more prominent than that of apatite cement. These differences might be due to the much faster resorption rate of the premixed CPCs.

[Studies on the progress of premixed calcium phosphate cements].

Calcium phosphate cement (CPC) is considered as an important bone repairing materials due to its excellent biocompatibility, osteoconductivity and remodellability, the study about its performance is still a hot topic in the field of bone tissue engineering. Premixed calcium phosphate cements (PCPC) has advantages that can save operatiion time,be convenient to the operation and preservation compared with the traditional way of immediately mixing calcium phosphate cement. PCCP has overcome the shortcomings of uneven and inadequate mixing, and can be arbitrarily remodeled according to the shape of defect, thus researches on PCCP has also become more and more interested

A study on biomineralization behavior of N-methylene phosphochitosan scaffolds.

Biomimetic growth of calcium phosphate over natural polymer may be an effective approach to constituting an organic/inorganic composite scaffold for bone tissue engineering. In this work, N-methylene phosphochitosan (NMPCS) was prepared via formaldehyde addition and condensation with phosphoric acid in a step that allowed homogeneous modification without obvious deterioration in chitosan (CS) properties. The NMPCS obtained was characterized by using FT-IR and elemental analysis. The macroporous scaffolds were fabricated through a freeze-drying technique. A comparative study on NMPCS and CS scaffold biomimetic mineralization was carried out in different media, i.e, a simulated body fluid (SBF) or alternative CaCl(2) and Na(2)HPO(4) solutions respectively. Apatite formation within NMPCS and CS scaffolds was identified with FT-IR, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and X-ray diffractometery (XRD). The results revealed alternate soaking of the scaffolds in CaCl(2) and Na(2)HPO(4) solutions was better than soaking in SBF solution alone in relation to apatite deposition on the scaffold pore walls. Biomineralization provides an approach to improve nature derived materials, e.g., chitosan derivative NMPCS properties e.g., compressive modulus, etc. SEM image of a NMPCS/apatite composite scaffold.

A preliminary study on chitosan and gelatin polyelectrolyte complex cytocompatibility by cell cycle and apoptosis analysis.

In this study, L929 cell adhesion, proliferation and apoptosis were investigated on chitosan (CS) and chitosan-gelatin (CS-Gel) membranes having different degrees of deacetylation (DD). The mitochondrial activity [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay results demonstrated that the DD played a key role in the L929 cell adhesion. Indeed, the higher the DD of a CS membrane, the stronger the cell adhesion. The cell cycle analysis showed that the CS surface inhibits most of the cells entering the cell cycle and the DD of CS had little effect on the cell cycle progression. On the other hand, this study also confirmed that CS, blended with Gel, induced L929 cells to enter the cell cycle, encouraged proliferation, decreased the degree of apoptosis on the CS membranes, and are comparable to the results from L929 cells on tissue culture plates. In brief, CS modified with Gel improves cytocompatibility by shielding the positively charged CS with a high charge density.

The properties of chitosan-gelatin membranes and scaffolds modified with hyaluronic acid by different methods.

The objective of the present study was to investigate the properties of chitosan-gelatin membranes or scaffolds, which were modified by incorporation of hyaluronic acid in the surface or bulk phase through co-crosslinking with N,N-(3-dimethylamino-propyl)-N'-ethyl carbodiimide (EDC) and N-hydroxysuccinimide (NHS) in 2-morpholinoethane sulfonic acid (MES) buffer. The comparative study on properties of surface modification (HA(S)) and polyblend membranes (HA(C)) revealed that gelatin was enriched on the surface of HA(C), while hyaluronic acid was enriched on the surface of the HA(S). The HA(S) membranes made by surface modification method had a characteristic surface morphology. The corresponding scaffolds were prepared through freeze-drying. The incorporation of hyaluronic acid improved flexibility and fibroblasts adhesion, while slowing down the rate of biodegradation of chitosan-gelatin scaffold. Human fibroblasts adhered and proliferated well on the membranes or scaffolds in vitro.

Structure and properties of bilayer chitosan-gelatin scaffolds.

Chitosan-gelatin hybrid polymer network scaffolds were prepared via the freeze-drying technique by using the ice microparticle as a porogen. Monolayer and bilayer scaffolds were obtained by using different pre-freezing methods. The novel bilayer scaffolds were prepared via contact with -56 degrees C lyophilizing plate directly, then lyophilized. The properties of chitosan-gelatin scaffolds, such as microstructure, physical and mechanical and degradable properties, were studied. These results suggested that the porosity and pore size of the scaffolds could be modulated with thermodynamic and kinetic parameters of ice formation. The scaffolds prepared from chitosan and gelatin can be utilized as a promising matrix for tissue engineering.

[Tissue engineering study on chitosan-gelatin/hydroxyapatite composite scaffolds--osteoblasts culture].

OBJECTIVE: To investigate the behavior of rat calvarial osteoblasts cultured on chitosan-gelatin/hydroxyapatite (CS-Gel/HA) composite scaffolds. METHODS: The rat calvarial osteoblasts (the 3rd passage) were seeded at a density of 1.01 x 10(6) cells/ml onto the CS-Gel/HA composite scaffolds having porosity 85.20%, 90.40% and 95.80%. Cell number was counted after cultured for 3 days, 1 week, 2 weeks and 3 weeks. Cell proliferation, bone-like tissue formation, and mineralization were separately detected by HE, von Kossa histological staining techniques. RESULTS: The CS-Gel/HA composite scaffolds supported the attachment of seeded rat calvarial osteoblasts. Cells proliferated faster in scaffold with higher porosity 90.40% and 95.80% than scaffold with lower porosity 85.20%. The osteoblasts/scaffold constructs were feasible for mineral deposition, and bone-like tissue formation in 3 weeks. CONCLUSION: This study suggests the feasibility of using CS-Gel/HA composite scaffolds for bone tissue engineering.