Tetracalcium Phosphate Biocement Hardened with a Mixture of Phytic Acid-Phytase in the Healing Process of Osteochondral Defects in Sheep.

Hyaline articular cartilage has unique physiological, biological, and biomechanical properties with very limited self-healing ability, which makes the process of cartilage regeneration extremely difficult. Therefore, research is currently focused on finding new and potentially better treatment options. The main objective of this in vivo study was to evaluate a novel biocement CX consisting of tetracalcium phosphate-monetit biocement hardened with a phytic acid-phytase mixture for the regeneration of osteochondral defects in sheep. The results were compared with tetracalcium phosphate-monetit biocement with classic fast-setting cement systems and untreated defects. After 6 months, the animals were sacrificed, and the samples were evaluated using macroscopic and histologic methods as well as X-ray, CT, and MR-imaging techniques. In contrast to the formation of fibrous or fibrocartilaginous tissue on the untreated side, treatment with biocements resulted in the formation of tissue with a dominant hyaline cartilage structure, although fine fibres were present (p < 0.001). There were no signs of pathomorphological changes or inflammation. Continuous formation of subchondral bone and hyaline cartilage layers was present even though residual biocement was observed in the trabecular bone. We consider biocement CX to be highly biocompatible and suitable for the treatment of osteochondral defects.

A Chitosan-Based Biomaterial Combined with Mesenchymal Stem Cell-Conditioned Medium for Wound Healing and Skin Regeneration.

The aim of this study was to provide a beneficial treatment effect of novel chitosan bio-polymeric material enriched with mesenchymal stem cell products derived from the canine adipose tissue (AT-MSC) on the artificial skin defect in a rabbit model. For the objectivity of the regeneration evaluation, we used histological analysis and a scoring system created by us, taking into account all the attributes of regeneration, such as inflammatory reaction, necrosis, granulation, formation of individual skin layers and hair follicles. We observed an acceleration and improvement in the healing of an artificially created skin defect after eight and ten weeks in comparison with negative control (spontaneous healing without biomaterial). Moreover, we were able to described hair follicles and epidermis layer in histological skin samples treated with a chitosan-based biomaterial on the eighth week after grafting.

Novel Biocement/Honey Composites for Bone Regenerative Medicine.

New biocements based on a powdered mixture of calcium phosphate/monetite (TTCPM) modified with the addition of honey were prepared by mixing the powder and honey liquid components at a non-cytotoxic concentration of honey (up to 10% (w/v)). The setting process of the cements was not affected by the addition of honey, and the setting time of ~4 min corresponded to the fast setting calcium phosphate cements (CPCs). The cement powder mixture was completely transformed into calcium-deficient nanohydroxyapatite after 24 h of hardening in a simulated body fluid, and the columnar growth of long, needle-like nanohydroxyapatite particles around the original calcium phosphate particles was observed in the honey cements. The compressive strength of the honey cements was reduced with the content of honey in the cement. Comparable antibacterial activities were found for the cements with honey solutions on Escherichia coli, but very low antibacterial activities were found for Staphylococcus aureus for all the cements. The enhanced antioxidant inhibitory activity of the composite extracts was verified. In vitro cytotoxicity testing verified the non-cytotoxic nature of the honey cement extracts, and the addition of honey promoted alkaline phosphatase activity, calcium deposit production, and the upregulation of osteogenic genes (osteopontin, osteocalcin, and osteonectin) by mesenchymal stem cells, demonstrating the positive synergistic effect of honey and CPCs on the bioactivity of cements that could be promising therapeutic candidates for the repair of bone defects.

Long-Bone-Regeneration Process in a Sheep Animal Model, Using Hydroxyapatite Ceramics Prepared by Tape-Casting Method.

This study was designed to investigate the effects of hydroxyapatite (HA) ceramic implants (HA cylinders, perforated HA plates, and nonperforated HA plates) on the healing of bone defects, addressing biocompatibility, biodegradability, osteoconductivity, osteoinductivity, and osteointegration with the surrounding bone tissue. The HA ceramic implants were prepared using the tape-casting method, which allows for shape variation in samples after packing HA paste into 3D-printed plastic forms. In vitro, the distribution and morphology of the MC3T3E1 cells grown on the test discs for 2 and 9 days were visualised with a fluorescent live/dead staining assay. The growth of the cell population was clearly visible on the entire ceramic surfaces and very good osteoblastic cell adhesion and proliferation was observed, with no dead cells detected. A sheep animal model was used to perform in vivo experiments with bone defects created on the metatarsal bones, where histological and immunohistochemical tissue analysis as well as X-ray and CT images were applied. After 6 months, all implants showed excellent biocompatibility with the surrounding bone tissue with no observed signs of inflammatory reaction. The histomorphological findings revealed bone growth immediately over and around the implants, indicating the excellent osteoconductivity of the HA ceramic implants. A number of islands of bone tissue were observed towards the centres of the HA cylinders. The highest degree of biodegradation, bioresorption, and new bone formation was observed in the group in which perforated HA plates were applied. The results of this study suggest that HA cylinders and HA plates may provide a promising material for the functional long-bone-defect reconstruction and further research.

Regenerative Potential of Hydroxyapatite-Based Ceramic Biomaterial on Mandibular Cortical Bone: An In Vivo Study.

Reconstruction of bone defects and maintaining the continuity of the mandible is still a challenge in the maxillofacial surgery. Nowadays, the biomedical research within bone defect treatment is focussed on the therapy of using innovative biomaterials with specific characteristics consisting of the body's own substances. Hydroxyapatite ceramic scaffolds have fully acceptable phase compositions, microstructures and compressive strengths for their use in regenerative medicine. The innovative hydroxyapatite ceramics used by us were prepared using the tape-casting method, which allows variation in the shape of samples after packing hydroxyapatite paste to 3D-printed plastic form. The purpose of our qualitative study was to evaluate the regenerative potential of the innovative ceramic biomaterial prepared using this method in the therapy of the cortical bone of the lower jaw in four mature pigs. The mandible bone defects were evaluated after different periods of time (after 3, 4, 5 and 6 months) and compared with the control sample (healthy cortical bone from the opposite side of the mandible). The results of the morphological, clinical and radiological investigation and hardness examination confirmed the positive regenerative potential of ceramic implants after treatment of the mandible bone defects in the porcine mandible model.

The Influence of Nanosilica on Properties of Cement Based on Tetracalcium Phosphate/Monetite Mixture with Addition of Magnesium Pyrophoshate.

The effect of nanosilica on the microstructure setting process of tetracalcium phosphate/nanomonetite calcium phosphate cement mixture (CPC) with the addition of 5 wt% of magnesium pyrophosphate (assigned as CT5MP) and osteogenic differentiation of mesenchymal stem cells cultured in cement extracts were studied. A more compact microstructure was observed in CT5MP cement with 0.5 wt% addition of nanosilica (CT5MP1Si) due to the synergistic effect of Mg2P2O7 particles, which strengthened the cement matrix and nanosilica, which supported gradual growth and recrystallization of HAP particles to form compact agglomerates. The addition of 0.5 wt% of nanosilica to CT5MP cement caused an increase in CS from 18 to 24 MPa while the setting time increased almost twofold. It was verified that adding nanosilica to CPC cement, even in a low amount (0.5 and 1 wt% of nanosilica), positively affected the injectability of cement pastes and differentiation of cells with upregulation of osteogenic markers in cells cultured in cement extracts. Results revealed appropriate properties of these types of cement for filling bone defects.

Characterization of Tetracalcium Phosphate/Monetite Biocement Modified by Magnesium Pyrophosphate.

Magnesium pyrophosphate modified tetracalcium phosphate/monetite cement mixtures (MgTTCPM) were prepared by simple mechanical homogenization of compounds in a ball mill. The MgP2O7 was chosen due to the suitable setting properties of the final cements, in contrast to cements with the addition of amorphous (Ca, Mg) CO3 or newberite, which significantly extended the setting time even in small amounts (corresponding ~to 1 wt% of Mg in final cements). The results showed the gradual dissolution of the same amount of Mg2P2O7 phase, regardless of its content in the cement mixtures, and the refinement of formed HAP nanoparticles, which were joined into weakly and mutually bound spherical agglomerates. The compressive strength of composite cements was reduced to 14 MPa and the setting time was 5-10 min depending on the composition. Cytotoxicity of cements or their extracts was not detected and increased proliferative activity of mesenchymal stem cells with upregulation of osteopontin and osteonectin genes was verified in cells cultured for 7 and 15 days in cement extracts. The above facts, including insignificant changes in the pH of simulated body fluid solution and mechanical strength close to cancellous bone, indicate that MgTTCPM cement mixtures could be suitable biomaterials for use in the treatment of bone defects.

Osteogenic potential and properties of injectable silk fibroin/tetracalcium phosphate/monetite composite powder biocement systems.

The powdered cement tetracalcium phosphate/monetite/silk fibroin composite (CFIB) was prepared by simple mechanical milling of tetracalcium phosphate/monetite powder mixture with fibrous soluble silk fibroin (SF). The powder composite cement mixtures contained 5 and 10 wt % of SF and 2% NaH2 PO4 solution with 0.1% genipin was used as a liquid component. The setting time of CFIB cement increased with addition of SF from 5 to 25 min in fully injectable cement with 10 wt % of SF. The compressive strength of hardened composites was reduced to 14 MPa which is close to strength of cancellous bone. The 8% of SF from origin amount in CFIB composites was only desorbed from cements after 7 days soaking in simulated body fluid (SBF). It was found almost full transformation of calcium phosphate components in composite to rod-like nanohydroxyapatite after hardening of CFIB cements in SBF. The SF in hardened cements was present in fine globular form after dissolution, actively affected the fluidity of pastes, morphology of hydroxyapatite particles, and microstructure. The excellent cell proliferation and a high over expression of osteogenic gene markers in MSCs were confirmed after the long-time cultivation in CFIB10 cement extract. Injectable CFIB10 cements have appropriate properties for utilization in bone defect treatments with possible positive effect on healing process.

In Vivo Study of Osteochondral Defect Regeneration Using Innovative Composite Calcium Phosphate Biocement in a Sheep Model.

This study aimed to clarify the therapeutic effect and regenerative potential of the novel, amino acids-enriched acellular biocement (CAL) based on calcium phosphate on osteochondral defects in sheep. Eighteen sheep were divided into three groups, the treated group (osteochondral defects filled with a CAL biomaterial), the treated group with a biocement without amino acids (C cement), and the untreated group (spontaneous healing). Cartilages of all three groups were compared with natural cartilage (negative control). After six months, sheep were evaluated by gross appearance, histological staining, immunohistochemical staining, histological scores, X-ray, micro-CT, and MRI. Treatment of osteochondral defects by CAL resulted in efficient articular cartilage regeneration, with a predominant structural and histological characteristic of hyaline cartilage, contrary to fibrocartilage, fibrous tissue or disordered mixed tissue on untreated defect (p < 0.001, modified O'Driscoll score). MRI results of treated defects showed well-integrated and regenerated cartilage with similar signal intensity, regularity of the articular surface, and cartilage thickness with respect to adjacent native cartilage. We have demonstrated that the use of new biocement represents an effective solution for the successful treatment of osteochondral defects in a sheep animal model, can induce an endogenous regeneration of cartilage in situ, and provides several benefits for the design of future therapies supporting osteochondral defect healing.

Tetracalcium Phosphate/Monetite/Calcium Sulfate Hemihdrate Biocement Powder Mixtures Prepared by the One-Step Synthesis for Preparation of Nanocrystalline Hydroxyapatite Biocement-Properties and In Vitro Evaluation.

A modified one-step process was used to prepare tetracalcium phosphate/monetite/calcium sulfate hemihydrate powder cement mixtures (CAS). The procedure allowed the formation of monetite and calcium sulfate hemihydrate (CSH) in the form of nanoparticles. It was hypothesized that the presence of nanoCSH in small amounts enhances the in vitro bioactivity of CAS cement in relation to osteogenic gene markers in mesenchymal stem cells (MSCs). The CAS powder mixtures with 15 and 5 wt.% CSH were prepared by milling powder tetracalcium phosphate in an ethanolic solution of both orthophosphoric and sulfuric acids. The CAS cements had short setting times (around 5 min). The fast setting of the cement samples after the addition of the liquid component (water solution of NaH2PO4) was due to the partial formation of calcium sulfate dihydrate and hydroxyapatite before soaking in SBF with a small change in the original phase composition in cement powder samples after milling. Nanocrystalline hydroxyapatite biocement was produced by soaking of cement samples after setting in simulated body fluid (SBF). The fast release of calcium ions from CAS5 cement, as well as a small rise in the pH of SBF during soaking, were demonstrated. After soaking in SBF for 7 days, the final product of the cement transformation was nanocrystalline hydroxyapatite. The compressive strength of the cement samples (up to 30 MPa) after soaking in simulated body fluid (SBF) was comparable to that of bone. Real time polymerase chain reaction (RT-PCR) analysis revealed statistically significant higher gene expressions of alkaline phosphatase (ALP), osteonectin (ON) and osteopontin (OP) in cells cultured for 14 days in CAS5 extract compared to CSH-free cement. The addition of a small amount of nanoCSH (5 wt.%) to the tetracalcium phosphate (TTCP)/monetite cement mixture significantly promoted the over expression of osteogenic markers in MSCs. The prepared CAS powder mixture with its enhanced bioactivity can be used for bone defect treatment and has good potential for bone healing.

Characterization of Properties, In Vitro and In Vivo Evaluation of Calcium Phosphate/Amino Acid Cements for Treatment of Osteochondral Defects.

Novel calcium phosphate cements containing a mixture of four amino acids, glycine, proline, hydroxyproline and either lysine or arginine (CAL, CAK) were characterized and used for treatment of artificial osteochondral defects in knee. It was hypothesized that an enhanced concentration of extracellular collagen amino acids (in complex mixture), in connection with bone cement in defect sites, would support the healing of osteochondral defects with successful formation of hyaline cartilage and subchondral bone. Calcium phosphate cement mixtures were prepared by in situ reaction in a planetary ball mill at aseptic conditions and characterized. It was verified that about 30-60% of amino acids remained adsorbed on hydroxyapatite particles in cements and the addition of amino acids caused around 60% reduction in compressive strength and refinement of hydroxyapatite particles in their microstructure. The significant over-expression of osteogenic genes after the culture of osteoblasts was demonstrated in the cement extracts containing lysine and compared with other cements. The cement pastes were inserted into artificial osteochondral defects in the medial femoral condyle of pigs and, after 3 months post-surgery, tissues were analyzed macroscopically, histologically, immunohistochemically using MRI and X-ray methods. Analysis clearly showed the excellent healing process of artificial osteochondral defects in pigs after treatment with CAL and CAK cements without any inflammation, as well as formation of subchondral bone and hyaline cartilage morphologically and structurally identical to the original tissues. Good integration of the hyaline neocartilage with the surrounding tissue, as well as perfect interconnection between the neocartilage and new subchondral bone tissue, was demonstrated. Tissues were stable after 12 months' healing.

Injectable Enzymatically Hardened Calcium Phosphate Biocement.

(1) Background: The preparation and characterization of novel fully injectable enzymatically hardened tetracalcium phosphate/monetite cements (CXI cements) using phytic acid/phytase (PHYT/F3P) hardening liquid with a small addition of polyacrylic acid/carboxymethyl cellulose anionic polyelectrolyte (PAA/CMC) and enhanced bioactivity. (2) Methods: Composite cements were prepared by mixing of calcium phosphate powder mixture with hardening liquid containing anionic polyelectrolyte. Phase and microstructural analysis, compressive strength, release of ions and in vitro testing were used for the evaluation of cement properties. (3) Results: The simple possibility to control the setting time of self-setting CXI cements was shown (7-28 min) by the change in P/L ratio or PHYT/F3P reaction time. The wet compressive strength of cements (up to 15 MPa) was close to cancellous bone. The increase in PAA content to 1 wt% caused refinement and change in the morphology of hydroxyapatite particles. Cement pastes had a high resistance to wash-out in a short time after cement mixing. The noncytotoxic character of CX cement extracts was verified. Moreover, PHYT supported the formation of Ca deposits, and the additional synergistic effect of PAA and CMC on enhanced ALP activity was found, along with the strong up-regulation of osteogenic gene expressions for osteopontin, osteocalcin and IGF1 growth factor evaluated by the RT-qPCR analysis in osteogenic αMEM 50% CXI extracts. (4) Conclusions: The fully injectable composite calcium phosphate bicements with anionic polyelectrolyte addition showed good mechanical and physico-chemical properties and enhanced osteogenic bioactivity which is a promising assumption for their application in bone defect regeneration.

Enzymatically hardened calcium phosphate biocement with phytic acid addition.

Novel enzymatically hardened tetracalcium phosphate/monetite cements were prepared applying phytic acid/phytase (PHYT/F3P) mixture as hardening liquid after dissolving in acetic acid solution (CX cement). Properties of the cements were compared with classic cement hardened with 2% NaH2PO4 (C cement) and cement hardened with acetic acid solution (CAC cement) only. In the microstructure of CX cement, columnar growth of hydroxyapatite particles was found in the form of walls around hydroxyapatite agglomerates originated from tetracalcium phosphate which were mutually separated by a material depleted low density zone. Wet compressive strengths (CS) of all cements were practically identical contrary to about 30% higher dry CS's of CX and CAC cements due to specific microstructure. It was verified noncytotoxic character of CX cement extracts and positive effect of CX cement on ALP activity and cell behavior during cultivation. The final Ca/P molar ratio and setting time of cement were effectively controlled by the amount of phytic acid and the change in PHYT/F3P mass ratio, or reaction time in hardening liquid, respectively.

Polyhydroxybutyrate/Chitosan 3D Scaffolds Promote In Vitro and In Vivo Chondrogenesis.

The articular cartilage is an avascular and aneural tissue and its injuries result mostly in osteoarthritic changes and formation of fibrous tissue. Efforts of scientists worldwide are focused on restoration of cartilage with increase in life quality of patients. Novel polymeric polyhydroxybutyrate/chitosan (PCH) porous 3D scaffolds were developed and characterized. The rat mesenchymal stem cells (MSCs) were seeded in vitro on PCH scaffolds by a simple filtration of MSCs suspension over scaffolds using syringe. The chondrogenesis of cell-scaffold constructs was carried out in supplemented chondrogenic cultivation medium. After 2 and 4 weeks of in vitro culturing cell-scaffold constructs in chondrogenic differentiation medium, the cartilage extracellular matrix components like glycosaminoglycans and collagens were identified in scaffolds by biochemical assays and histological and immunohistochemical staining. Preliminary in vivo experiments with acellular scaffolds, which filled the artificially created cartilage defect in sheep knee were done and evaluated. Cells released from the bone marrow cavity have penetrated into acellular PCH scaffold in cartilage defect and induced tissue formation similar to hyaline cartilage. The results demonstrated that PCH scaffolds supported chondrogenic differentiation of MSCs in vitro. Acellular PCH scaffolds were successfully utilized in vivo for reparation of artificially created knee cartilage defects in sheep and supported wound healing and formation of hyaline cartilage-like tissue.

In vitro cytotoxicity of calcium phosphate cement reinforced with multiwalled carbon nanotubes.

The in vitro cytotoxicity of both the multiwalled carbon nanotubes (MWCNT) in suspension with culture medium and the tetracalcium phosphate/monetite cement with addition of 0.8 wt% of MWCNTs on fibroblasts and osteoblasts were studied. The cytotoxicity was evaluated by MTS test (formazan) and live/dead staining. No cytotoxicity of MWCNT extract was measured contrary to about 60% reduction in proliferation of fibroblasts in MWCNT suspension as compared with negative control. The several contact cytotoxicity of MWCNT composite cement surfaces on seeded cells was demonstrated by MTS test and live/dead staining of damaged fibroblasts and dead osteoblasts after 72 h of culture. The detailed microstructure analysis showed a significant refinement of the surface texture due to the formation of thin needle-like hydroxyapatite particles on MWCNTs and this effect could be responsible for cytotoxicity of composites.

The Serum Protein Profile and Acute Phase Proteins in the Postoperative Period in Sheep after Induced Articular Cartilage Defect.

Although several new implants have been developed using animal studies for the treatment of osteochondral and cartilage defects, there is a lack of information on the possible metabolic and biochemical reactions of the body to the implantation of biomaterials and cartilage reconstruction. Therefore, this study was aimed at evaluating the serum protein pattern and the alterations in the concentrations of selected acute phase proteins in five clinically healthy female sheep before and after the reconstruction of experimentally induced articular cartilage defects using polyhydroxybutyrate/chitosan based biopolymer material. The concentrations of total serum proteins (TSP), protein fractions, and selected acute phase proteins-serum amyloid A (SAA), haptoglobin (Hp), and C-reactive protein (CRP)-were measured before and on days seven, 14, and 30 after the surgical intervention. The TSP concentrations showed no marked differences during the evaluated period. Albumin values decreased on day seven and day 14 after surgery. In the concentrations of α1-, α2-, ß-, and γ2-globulins, a gradual significant increase was observed during the postoperative period (p < 0.05). The γ1-globulins decreased slightly seven days after surgery. The concentrations of SAA, Hp, and CRP increased significantly after the surgical intervention with a subsequent decrease on day 30. Presented results suggest marked alterations in the serum protein pattern after surgical intervention.

Preclinical alternative model for analysis of porous scaffold biocompatibility in bone tissue engineering.

Using scaffolds with appropriate porosity represents a potential approach for repair of critical-size bone defects. Vascularization is essential for bone formation and healing. This study investigates methods for monitoring angiogenesis within porous biopolymer scaffolds on the basis of polyhydroxybutyrate (PHB)/chitosan. We use the chick and quail chorioallantoic membrane (CAM) assay as an in vivo model focused on the formation of new blood vessels inside the implant structure. Chemical properties of the surface in biopolymer scaffold matrix were characterized as well as the tissue reaction of the CAM. Implantation of a piece of polymer scaffold results in vascular reaction, documented visually and by ultrasound biomicroscopy. Histological analysis shows myofibroblast reaction (smooth muscle actin-positive cells) without excessive collagen deposition. Cell invasion is observed inside the implant, and QH1 marker, detecting hemangioblasts and endothelial cells of quail origin, confirms the presence of vascular network. The CAM assay is a rapid and easy way to test biocompatibility and vasculogenic potential of new candidate scaffolds for bone tissue bioengineering with respect to the 3R´ s.

Hydrolysis, setting properties and in vitro characterization of wollastonite/newberyite bone cement mixtures.

Bone cements based on magnesium phosphates such as newberyite (N; MgHPO4.3H2O) have been shown as potential bone substitutes due to their biocompatibility, biodegradability and ability to support osteoblast differentiation and proliferation. Newberyite can hydrolyze to hydrated magnesium phosphate compounds (e.g. bobierite (Mg3(PO4)2.8H2O)) at alkaline conditions. In this study, 25 and 50 wt% of crystalline ߠ-wollastonite (woll; CaSiO3) was admixed to newberyite powder in order to both enhance the acid-base hydrolysis of newberyite and to produce a functional bone cement. The setting process of wollastonite/newberyite cement mixtures started with the hydrolysis of the wollastonite with further transformation of newberyite into bobierite and the formation of magnesium silicate phase. The results demonstrated that 25 wollastonite/newberyite and 50 wollastonite/newberyite cement pastes at optimal powder/liquid ratios had final setting times of ∼34 and 25 min and compressive strength values of 18 and 32 MPa after seven days setting, respectively. The tests of cytotoxicity of cement extracts on osteoblastic cells and contact cytotoxicity of the cement substrates showed different results. The osteoblasts cultured in cement extracts readily proliferated which confirmed the non-cytotoxic concentration of ions released from both cements. On the other hand, a strong cytotoxic character of 25 wollastonite/newberyite sample surface in contrary to high (∼80%) proliferation activity of cells on the 50 wollastonite/newberyite cement substrate was observed. The differences in cell proliferation activity was attributed to different surface topographies of cement substrates, where needle-like precipitated microcrystals of magnesium phosphate phase (in 25 wollastonite/newberyite cement) prevented the adhesion and proliferation of osteoblasts contrary to the smoother surface covered by extremely fine nanoparticles in the 50 wollastonite/newberyite cement.

In vitro and in vivo study of microporous ceramics using MC3T3 cells, CAM assay and a pig animal model.

Bone tissue engineering combines biomaterials with biologically active factors and cells to hold promise for reconstructing craniofacial defects. In this study the biological activity of biphasic hydroxyapatite ceramics (HA; a bone substitute that is a mixture of hydroxyapatite and ß-tricalcium phosphate in fixed ratios) was characterized (1) in vitro by assessing the growth of MC3T3 mouse osteoblast lineage cells, (2) in ovo by using the chick chorioallantoic membrane (CAM) assay and (3) in an in vivo pig animal model. Biocompatibility, bioactivity, bone formation and biomaterial degradation were detected microscopically and by radiology and histology. HA ceramics alone demonstrated great biocompatibility on the CAM as well as bioactivity by increased proliferation and alkaline phosphatase secretion of mouse osteoblasts. The in vivo implantation of HA ceramics with bone marrow mesenchymal stem cells (MMSCs) showed de novo intramembranous bone healing of critical-size bone defects in the right lateral side of pig mandibular bodies after 3 and 9 weeks post-implantation. Compared with the HA ceramics without MMSCs, the progress of bone formation was slower with less-developed features. This article highlights the clinical use of microporous biphasic HA ceramics despite the unusually shaped elongated micropores with a high length/width aspect ratio (up to 20) and absence of preferable macropores (>100 µm) in bone regenerative medicine.

Effect of enzymatic degradation of chitosan in polyhydroxybutyrate/chitosan/calcium phosphate composites on in vitro osteoblast response.

Polyhydroxybutyrate/chitosan/calcium phosphate composites are interesting biomaterials for utilization in regenerative medicine and they may by applied in reconstruction of deeper subchondral defects. Insufficient informations were found in recent papers about the influence of lysozyme degradation of chitosan in calcium phosphate/chitosan based composites on in vitro cytotoxicity and proliferation activity of osteoblasts. The effect of enzymatic chitosan degradation on osteoblasts proliferation was studied on composite films in which the porosity of origin 3D scaffolds was eliminated and the surface texture was modified. The significantly enhanced proliferation activity with faster population growth of osteoblasts were found on enzymatically degraded biopolymer composite films with α-tricalcium phosphate and nanohydroxyapatite. No cytotoxicity of composite films prepared from lysozyme degraded scaffolds containing a large fraction of low molecular weight chitosans (LMWC), was revealed after 10 days of cultivation. Contrary to above in the higher cytotoxicity origin untreated nanohydroxyapatite films and porous composite scaffolds. The results showed that the synergistic effect of surface distribution, morphology of nanohydroxyapatite particles, microtopography and the presence of LMWC due to chitosan degradation in composite films were responsible for compensation of the cytotoxicity of nanohydroxyapatite composite films or porous composite scaffolds.