Fracture modes under uniaxial compression in hydroxyapatite scaffolds fabricated by robocasting

The fracture modes of hydroxyapatite (HA) scaffolds fabricated by direct-write assembly (robocasting) are analyzed in this work. Concentrated HA inks with suitable viscoelastic properties were developed to enable the fabrication of prototype structures consisting of a 3-D square mesh of interpenetrating rods. The fracture behavior of these model scaffolds under compressive stresses is determined from in situ uniaxial tests performed in two different directions: perpendicular to the rods and along one of the rod directions. The results are analyzed in terms of the stress field calculated by finite element modeling (FEM). This analysis provides valuable insight into the mechanical behavior of scaffolds for bone tissue engineering applications fabricated by robocasting.     

Sintering and robocasting of beta-tricalcium phosphate scaffolds for orthopaedic applications

beta-Tricalcium phosphate (beta-TCP) scaffolds with designed, three-dimensional (3-D) geometry and mesoscale porosity have been fabricated by direct-write assembly (robocasting) techniques. Concentrated beta-TCP inks with suitable viscoelastic properties were developed to enable the fabrication of the complex 3-D structures. A comprehensive study of the sintering behavior of TCP as a function of the calcium content in the starting powder was also carried out, and the optimal heat treatment for fabricating scaffolds with dense beta-TCP rods has been determined. Such analysis provides clues to controlling the microstructure of the fabricated structures and, therefore, enabling the fabrication by robocasting of TCP scaffolds with tailored performance for bone tissue engineering applications.     

Mechanical properties of calcium phosphate coatings deposited by laser ablation

Amorphous calcium phosphate and crystalline hydroxyapatite coatings with different morphologies were deposited onto Ti-6Al-4V substrates by means of the laser ablation technique. The strength of adhesion of the coatings to the substrate and their mode of fracture were evaluated through the scratch test technique and scanning electron microscopy. The effect of wet immersion on the adhesion was also assessed. The mechanisms of failure and the critical load of delamination differ significantly depending on the phase and structure of the coatings. The HA coatings with granular morphology have higher resistance to delamination as compared to HA coatings with columnar morphology. This fact has been related to the absence of stresses for the granular morphology.     

Mechanical properties of porous, electrosprayed calcium phosphate coatings

Mechanical properties of calcium phosphate coatings (CaP), deposited using the electrostatic spray deposition (ESD) technique, have been characterized using a range of analytical techniques, including tensile testing (ASTM C633), fatigue testing (ASTM E855), and scratch testing using blunt and sharp scratch styli. Moreover, a simple explantation procedure was successfully introduced using ESD-coated, threaded dental implants to characterize the mechanical performance of CaP coatings qualitatively under conditions that mimic clinical situations as close as possible. Generally, all analysis techniques revealed that ESD coatings need to be crystallized in order to ensure interfacial adhesion to the substrate and sufficient mechanical strength of the superficial reticular structure. Crystalline carbonated hydroxyapatite coatings (CHA, heat-treated at 700 degrees C) were resistant to fatigue as well as to plastic ploughing deformation by means of various scratch styli, and the fragile surface structure of ESD coatings was maintained to a large extent after unscrewing CHA-coated dental implants from femoral condyles of goat cadavers. From these experiments, it was concluded that interfacial adhesion of crystalline CHA ESD coatings to the titanium substrate was sufficient, but that mechanical strength of the superficial architecture of ESD coatings need to be optimized for applications where high shear and compressive stresses are imposed onto the rather fragile coating surface of reticular ESD morphologies.     

Mechanical and structural characterisation of completely degradable polylactic acid/calcium phosphate glass scaffolds

This study involves the mechanical and structural characterisation of completely degradable scaffolds for tissue engineering applications. The scaffolds are a composite of polylactic acid (PLA) and a soluble calcium phosphate glass, and are thus completely degradable. A factorial experimental design was applied to optimise scaffold composition prior to simultaneous microtomography and micromechanical testing. Synchrotron X-ray microtomography combined with in situ micromechanical testing was performed to obtain three-dimensional (3D) images of the scaffolds under compression. The 3D reconstruction was converted into a finite element mesh which was validated by simulating a compression test and comparing it with experimental results. The experimental design reveals that larger glass particle and pore sizes reduce the stiffness of the scaffolds, and that the porosity is largely unaffected by changes in pore sizes or glass weight content. The porosity ranges between 93% and 96.5%, and the stiffness ranges between 50 and 200 kPa. X-ray projections show a homogeneous distribution of the glass particles within the PLA matrix, and illustrate pore-wall breakage under strain. The 3D reconstructions are used qualitatively to visualise the distribution of the phases of the composite material, and to follow pore deformation under compression. Quantitatively, scaffold porosity, pore interconnectivity and surface/volume ratios have been calculated. Finite element analysis revealed the stress and strain distribution in the scaffold under compression, and could be used in the future to characterise the mechanical properties of the scaffolds.     

Mechanical properties of bioactive glass (13-93) scaffolds fabricated by robotic deposition for structural bone repair

There is a need to develop synthetic scaffolds to repair large defects in load-bearing bones. Bioactive glasses have attractive properties as a scaffold material for bone repair, but data on their mechanical properties are limited. The objective of the present study was to comprehensively evaluate the mechanical properties of strong porous scaffolds of silicate 13-93 bioactive glass fabricated by robocasting. As-fabricated scaffolds with a grid-like microstructure (porosity 47%, filament diameter 330 μm, pore width 300 μm) were tested in compressive and flexural loading to determine their strength, elastic modulus, Weibull modulus, fatigue resistance, and fracture toughness. Scaffolds were also tested in compression after they were immersed in simulated body fluid (SBF) in vitro or implanted in a rat subcutaneous model in vivo. As fabricated, the scaffolds had a strength of 86 ± 9 MPa, elastic modulus of 13 ± 2 GPa, and a Weibull modulus of 12 when tested in compression. In flexural loading the strength, elastic modulus, and Weibull modulus were 11 ± 3 MPa, 13 ± 2 GPa, and 6, respectively. In compression, the as-fabricated scaffolds had a mean fatigue life of ～10⁶ cycles when tested in air at room temperature or in phosphate-buffered saline at 37 °C under cyclic stresses of 1–10 or 2–20 MPa. The compressive strength of the scaffolds decreased markedly during the first 2 weeks of immersion in SBF or implantation in vivo, but more slowly thereafter. The brittle mechanical response of the scaffolds in vitro changed to an elasto-plastic response after implantation for longer than 2–4 weeks in vivo. In addition to providing critically needed data for designing bioactive glass scaffolds, the results are promising for the application of these strong porous scaffolds in loaded bone repair.     

Fabrication and in vitro characterization of three-dimensional organic/inorganic scaffolds by robocasting

A key issue for the fabrication of scaffolds for tissue engineering is the development of processing techniques flexible enough to produce materials with a wide spectrum of solubility (bioresorption rates) and mechanical properties matching those of calcified tissues. These techniques must also have the capability of generating adequate porosity to further serve as a framework for cell penetration, new bone formation, and subsequent remodeling. In this study we show how hybrid organic/inorganic scaffolds with controlled microstructures can be built using robotic assisted deposition at room temperature. Polylactide or polycaprolactone scaffolds with pore sizes ranging between 200-500 microm and hydroxyapatite contents up to 70 wt % were fabricated. Compressive tests revealed an anisotropic behavior of the scaffolds, strongly dependant on their chemical composition. The inclusion of an inorganic component increased their stiffness but they were not brittle and could be easily machined even for ceramic contents up to 70 wt %. The mechanical properties of hybrid scaffolds did not degrade significantly after 20 days in simulated body fluid. However, the stiffness of pure polylactide scaffolds increased drastically due to polymer densification. Scaffolds containing bioactive glasses were also printed. After 20 days in simulated body fluid they developed an apatite layer on their surface.     

3D生物描绘孔结构可控钙磷硅基骨修复支架的生物力学性能

目的设计和制备新型钙磷硅基骨修复支架,研究其在不同外力作用下体外生物力学性能。方法以自固化磷酸钙骨水泥(calcium phosphate cement,CPC)、介孔硅酸钙(mesporous calcium silicate,MCS)为原料,通过3D生物描绘技术构建孔径分别为350、500μm的MCS/CPC复合支架。采用扫描电镜观察支架表面形貌;分别通过万能力学试验机和动态力学分析仪,考察具有不同孔道结构MCS/CPC支架的抗压力学性能和不同频率动态周期性载荷作用下的力学性能。结果通过3D生物描绘技术能够实现对钙磷硅基骨修复支架内部孔道结构的可控制备。孔径为350μm的MCS/CPC支架具有较高的抗压力学强度[(9.80±0.39)MPa]和抗压模量[(132.50±4.30)MPa];此外,载荷频率在1~100 Hz范围内,孔径为350μm的支架具有较高的储能模量。结论通过3D生物描绘技术制备的孔径为350μm的MCS/CPC复合支架不仅具有规则的连通孔道,还具有较高的抗压力学性能,能在动态载荷作用下保持结构稳定,适合作为一种新型的骨缺损修复材料。     

Mechanical properties and cell cultural response of polycaprolactone scaffolds designed and fabricated via fused deposition modeling

A number of different processing techniques have been developed to design and fabricate three-dimensional (3D) scaffolds for tissue-engineering applications. The imperfection of the current techniques has encouraged the use of a rapid prototyping technology known as fused deposition modeling (FDM). Our results show that FDM allows the design and fabrication of highly reproducible bioresorbable 3D scaffolds with a fully interconnected pore network. The mechanical properties and in vitro biocompatibility of polycaprolactone scaffolds with a porosity of 61 +/- 1% and two matrix architectures were studied. The honeycomb-like pores had a size falling within the range of 360 x 430 x 620 microm. The scaffolds with a 0/60/120 degrees lay-down pattern had a compressive stiffness and a 1% offset yield strength in air of 41.9 +/- 3.5 and 3.1 +/- 0.1 MPa, respectively, and a compressive stiffness and a 1% offset yield strength in simulated physiological conditions (a saline solution at 37 degrees C) of 29.4 +/- 4.0 and 2.3 +/- 0.2 MPa, respectively. In comparison, the scaffolds with a 0/72/144/36/108 degrees lay-down pattern had a compressive stiffness and a 1% offset yield strength in air of 20.2 +/- 1.7 and 2.4 +/- 0.1 MPa, respectively, and a compressive stiffness and a 1% offset yield strength in simulated physiological conditions (a saline solution at 37 degrees C) of 21.5 +/- 2.9 and 2.0 +/- 0.2 MPa, respectively. Statistical analysis confirmed that the five-angle scaffolds had significantly lower stiffness and 1% offset yield strengths under compression loading than those with a three-angle pattern under both testing conditions (p < or = 0.05). The obtained stress-strain curves for both scaffold architectures demonstrate the typical behavior of a honeycomb structure undergoing deformation. In vitro studies were conducted with primary human fibroblasts and periosteal cells. Light, environmental scanning electron, and confocal laser microscopy as well as immunohistochemistry showed cell proliferation and extracellular matrix production on the polycaprolactone surface in the 1st culturing week. Over a period of 3-4 weeks in a culture, the fully interconnected scaffold architecture was completely 3D-filled by cellular tissue. Our cell culture study shows that fibroblasts and osteoblast-like cells can proliferate, differentiate, and produce a cellular tissue in an entirely interconnected 3D polycaprolactone matrix.     

Physical and degradation properties of PLGA scaffolds fabricated by salt fusion technique

Tissue engineering scaffolds require a controlled pore size and interconnected pore structures to support the host tissue growth. In the present study, three dimensional (3D) hybrid scaffolds of poly lactic acid (PLA) and poly glycolic acid (PGA) were fabricated using solvent casting/particulate leaching. In this case, partially fused NaCl particles were used as porogen (200-300µ) to improve the overall porosity (≥90%) and internal texture of scaffolds. Differential scanning calorimeter (DSC) analysis of these porous scaffolds revealed a gradual reduction in glass transition temperature (Tg) (from 48°C to 42.5°C) with increase in hydrophilic PGA content. The potential applications of these scaffolds as implants were further tested for their biocompatibility and biodegradability in four simulated body fluid (SBF) types in vitro. Whereas, simulated body fluid (SBF) Type1 with the optimal amount of HCO₃⁻ ions was found to be more appropriate and sensible for testing the bioactivity of scaffolds. Among three combinations of polymer scaffolds, sample B with a ratio of 75:25 of PLA: PGA showed greater stability in body fluids (pH 7.2) with an optimum degradation rate (9% to 12% approx). X-ray diffractogram also confirmed a thin layer of hydroxyapatite deposition over sample B with all SBF types in vitro.     

Porous morphology, porosity, mechanical properties of poly(alpha-hydroxy acid)-tricalcium phosphate composite scaffolds fabricated by low-temperature deposition

Tissue engineering is expected to construct complicated hominine organs composed of many different types of cells. One of the key points is the accurate controlling of scaffold material and porous morphology point by point. A new direct rapid prototyping process called low-temperature deposition manufacturing (LDM) was proposed to fabricate scaffolds. The new process integrated extrusion/jetting and phase separation and therefore could fabricate scaffolds with hierarchical porous structures creating a wonderful environment for the growth of new tissue. The interconnected computer-designed macropores allow cells in the new tissue to grow throughout the scaffold. Also, the parameter-controlled micropores let nutrition in and metabolic wastes out. The macrocellular morphology, microcellular morphology, porosity, and mechanical properties of the poly(alpha-hydroxy acid)-TCP composite scaffolds prepared by the proposed method are investigated. These scaffolds with high controllability would potentially play an important role in tissue engineering. LDM could also be combined with multinozzle deposition or cell deposition to exactly control materials or cells point by point. This might bring a breakthrough to the engineered fabrication of complicated organs.     

双相钙磷生物陶瓷/硫酸钙骨水泥多孔三维支架的生物性能

背景：随着组织工程技术的发展,多孔生物陶瓷被越来越多的运用到骨缺损的修复中,当前的研究主要集中在这种生物陶瓷的合成及其各项性能的评价。 目的：研究一种新型骨水泥的制备方法并测定其理化性能及与成骨细胞的生物相容性。 方法：共沉淀法制备双相钙磷生物陶瓷粉体,利用胶体团聚成颗粒,烧结后得到颗粒状、多孔羟基磷灰石/磷酸三钙生物陶瓷,并按不同比例与高纯度医用半水硫酸钙混合制备钙磷陶瓷/硫酸钙骨水泥。 结果与结论：X射线衍射证实合成物质为双相钙磷陶瓷,颗粒状双相钙磷陶瓷具有多孔网状结构,骨水泥在   3 min内保持可塑状态,固化时间为15 min,固化温度为36.5 ℃,压缩强度最高为5.82 MPa,MTT毒性级为0级,成骨细胞在材料表面生长良好。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程全文链接：     

磷酸钙及硫酸钙支架在骨组织工程中的研究进展

BACKGROUND: It is a hotspot that calcium phosphate and calcium sulphate as the main ingredients are combined with one or more other materials to improve or increase the performance of bone tissue engineering scaffolds. OBJECTIVE: To introduce the research advance of these two kinds of scaffolds in bone tissue engineering. METHODS: The articles related to the bone tissue engineering published during January 2000 to June 2015 were retrieved from CNKI and PubMed databases by computer. The key words were “bone tissue engineering, scaffold, calcium phosphate, calcium sulphate, vascularization” in Chinese and English, respectively. ESULTS AND CONCLUSION: Calcium phosphate and calcium sulfate are characterized as having good biocompatibility, biodegradability, osteoconductivity and complete bone substitutability. However, single use of calcium phosphate or calcium sulfate scaffold has certain disadvantages, both of which are difficult to fully meet the requirements of the bone defect repair. Improvement can be acquired in the mechanical strength, injectability and biodegradability, as well as drug-loading and pro-angiogenesis of the scaffold in combination with other materials. In the basal and clinical research, we should explore and develop ideal scaffolds in on the basis of therapeutic aim. However, most of the scaffold studies are still at the extracorporeal and animal experiment stage, and the comparative studies on composite scaffolds and optimal proportion of those composite scaffolds still need to be further investigated.      

壳聚糖与海藻酸钙双相陶瓷骨支架的机械性能及细胞相容性

BACKGROUND: Hydroxyapatite/β-tricalcium phosphate biphasic ceramic bone has good cell compatibility, but its mechanical properties are poor. OBJECTIVE: To construct chitosan/ or calcium alginate/biphasic ceramic bone scaffolds and to detect their mechanical properties and cytocompatibility. METHODS: Different concentrations of chitosan (2%, 4%, 7%, 10%) or calcium alginate (3%, 4%, 5%, 7%) were mixed with biphasic ceramic bone to prepare chitosan/biphasic ceramic bone scaffold and calcium alginate/biphasic ceramic bone scaffold. Their morphology and structure, coagulation time, anti-dissolution properties, shear force, compressive strength and cell compatibility were detected. RESULTS AND CONCLUSION: (1) Coagulation time: with the concentration increase, the initial and final setting time of these two kinds of composite scaffolds were prolonged to some extent. (2) Scanning electron microscopy: these two kinds of composite scaffolds showed porous microstructures with different pore sizes. (3) Anti-dissolution properties: the calcium alginate/biphasic ceramic bone scaffold (3%, 4%, 5%, 7%) and chitosan/biphasic ceramic bone scaffold (7%, 10%) had good anti-dissolution properties in the liquid. (4) Mechanical strength: with the concentration increase, the shear force and compressive strength of the calcium alginate/biphasic ceramic bone scaffold were reduced. (5) Cell compatibility: the cytotoxicity of chitosan/ or calcium alginate/biphasic ceramic bone scaffolds was graded as 0-1 or 2-3, respectively. These results show that the chitosan/biphasic ceramic bone scaffold has better mechanical properties and cell compatibility than the calcium alginate/biphasic ceramic bone scaffold.      

Vascularization and biocompatibility of scaffolds consisting of different calcium phosphate compounds

Scaffolds for tissue engineering of bone should mimic bone matrix and promote vascular ingrowth. Whether synthetic hydroxyapatite and acellular dentin, both materials composed from calcium phosphate, fulfill these material properties has not been studied yet. Therefore, we herein studied in vivo the host angiogenic and inflammatory response to these biomaterials. Porous scaffolds of hydroxyapatite and isogeneic acellular dentin were implanted into the dorsal skinfold chamber of balb/c mice. Additional animals received perforated implants of isogeneic calvarial bone displaying pores similar in size and structure to those of both scaffolds. Chambers of animals without implants served as controls. Angiogenesis and neovascularization as well as inflammatory leukocyte-endothelial cell interaction and microvascular leakage were analyzed over a 14-day time period using intravital fluorescence microscopy. Implantation of both hydroxyapatite and dentin scaffolds showed a slight increase in leukocyte recruitment compared with controls. This was associated with an elevation of microvascular permeability, which was comparable to that observed in response to isogeneic bone. In addition, hydroxyapatite as well as dentin scaffolds induced a marked angiogenic response, which resulted in complete vascularization of the implants until day 14. Of interest, in hydroxyapatite scaffolds, the newly formed capillaries were not as densely meshed as in dentin scaffolds, in which the functional capillary density was comparable to that measured in bone implants. Hydroxyapatite and, in particular, dentin scaffolds promote vascularization and exhibit a biocompatibility comparable to that of isogeneic bone. This may guarantee the rapid incorporation of these materials into the host tissue.     

Mechanical and biological properties of hydroxyapatite/tricalcium phosphate scaffolds coated with poly(lactic-co-glycolic acid)

Regeneration of bone, cartilage and osteochondral tissues by tissue engineering has attracted intense attention due to its potential advantages over the traditional replacement of tissues with synthetic implants. Nevertheless, there is still a dearth of ideal or suitable scaffolds based on porous biomaterials, and the present study was undertaken to develop and evaluate a useful porous composite scaffold system. Here, hydroxyapatite (HA)/tricalcium phosphate (TCP) scaffolds (average pore size: 500 μm; porosity: 87%) were prepared by a polyurethane foam replica method, followed by modification with infiltration and coating of poly(lactic-co-glycolic acid) (PLGA). The thermal shock resistance of the composite scaffolds was evaluated by measuring the compressive strength before and after quenching or freezing treatment. The porous structure (in terms of pore size, porosity and pore interconnectivity) of the composite scaffolds was examined. The penetration of the bone marrow stromal stem cells into the scaffolds and the attachment of the cells onto the scaffolds were also investigated. It was shown that the PLGA incorporation in the HA/TCP scaffolds significantly increased the compressive strength up to 660 kPa and the residual compressive strength after the freezing treatment decreased to 160 kPa, which was, however, sufficient for the scaffolds to withstand subsequent cell culture procedures and a freeze–drying process. On the other hand, the PLGA coating on the strut surfaces of the scaffolds was rather thin (<5 μm) and apparently porous, maintaining the high open porosity of the HA/TCP scaffolds, resulting in desirable migration and attachment of the bone marrow stromal stem cells, although a thicker PLGA coating would have imparted a higher compressive strength of the PLGA-coated porous HA/TCP composite scaffolds.     

In vitro evaluation of potential calcium phosphate scaffolds for tissue engineering

Nanocrystalline calcium phosphates are very interesting candidates as scaffolds for bone tissue engineering. These materials show excellent in vivo biocompatibility, cell proliferation, and resorption. In this work we have studied the osteoblast-like cell behavior seeded onto HA and BCP synthesized by controlled crystallization method and treated at different temperatures. In vitro cell attachment, proliferation, differentiation, spreading, and cytotoxicity tests have been carried out. The results can be explained as a function of the phase composition and microstructure. Under in vitro closed conditions, nanocrystalline HA depletes the calcium of the medium avoiding cell proliferation, whereas well-crystallized HA enhances high cell proliferation. On the other hand, nanocrystalline BCPs supply Ca(2+) to the medium due to the higher solubility of the beta-TCP component, allowing an excellent in vitro cellular response when osteoblast-like cells are seeded on it. These features make BCPs excellent candidates as scaffolds for bone tissue engineering.     

Direct write assembly of calcium phosphate scaffolds using a water-based hydrogel

The development of materials to support bone regeneration requires flexible fabrication technologies able to tailor chemistry and architecture for specific applications. In this work we describe the preparation of ceramic-based inks for robotic-assisted deposition (robocasting) using Pluronic^® F-127 solutions. This approach allows the preparation of pseudoplastic inks with solid contents ranging between 30 and 50 vol.%, enabling them to flow through a narrow printing nozzle while supporting the weight of the printed structure. Ink formulation does not require manipulation of the pH or the use of highly volatile organic components. Therefore, the approach can be used to prepare materials with a wide range of compositions, and here we use it to build hydroxyapatite (HA), β-tricalcium phosphate (β-TCP) and biphasic (HA/β-TCP) structures. The flow of the inks is controlled by the Pluronic^® content and the particle size distribution of the ceramic powders. The use of wide size distributions favors flow through the narrow printing nozzles and we have been able to use printing nozzles as narrow as 100 μm in diameter, applying relatively low printing pressures. The microporosity of the printed lines increases with increasing Pluronic^® content and lower sintering temperatures. Microporosity can play a key role in determining the biological response to the materials, but it also affects the strength of the structure.     

Mechanical and acid neutralizing properties and bacteria inhibition of amorphous calcium phosphate dental nanocomposite

Dental composites do not hinder bacteria colonization and plaque formation. Caries at the restoration margins is a frequent reason for replacement of existing restorations, which accounts for 50 to 70% of all restorations. The objectives of this study were to examine the filler level effect on nanocomposite containing nanoparticles of amorphous calcium phosphate (NACP) and investigate the load-bearing and acid-neutralizing properties and bacteria inhibition. NACP with 116-nm particle size were synthesized via a spray-drying technique and incorporated into a resin. Flexural strength of nanocomposite with 10 to 30% NACP fillers matched the strength of a commercial hybrid composite (p > 0.1). Nanocomposite with 40% NACP matched the strength of a microfill composite, which was 2-fold that of a resin-modified glass ionomer. Nanocomposite with 40% NACP neutralized a lactic acid solution of pH 4 by rapidly increasing the pH to 5.69 in 10 min. In contrast, the commercial controls had pH staying at near 4. Using Streptoccocus mutans, an agar disk-diffusion test showed no inhibition zone for commercial controls. In contrast, the inhibition zone was (2.5 ± 0.7) mm for nanocomposite with 40% NACP. Crystal violet staining showed that S. mutans coverage on nanocomposite was 1/4 that on commercial composite. In conclusion, novel calcium-phosphate nanocomposite matched the mechanical properties of commercial composite and rapidly neutralized lactic acid of pH 4. The nanocomposite appeared to moderately reduce the S. mutans growth, and further study is needed to obtain strong antimicrobial properties. The new nanocomposite may have potential to reduce secondary caries and restoration fracture, two main challenges facing tooth cavity restorations.     

Ultrasound effect on osteoblast precursor cells in trabecular calcium phosphate scaffolds

This study investigated the in vitro effect of low-intensity pulsed ultrasound (LIPUS) on human embryonic palatal mesenchyme cells (HEPM, CRL-1486, ATCC, Manassas, VA), an osteoblast precursor cell line, during early adhesion to calcium phosphate scaffolds. Hydroxyapatite (HA) and beta-tricalcium phosphate (TCP) ceramic scaffolds were produced by a template coating method. Phospho-specific antibody cell-based ELISA (PACE) technique was utilized on stress activation proteins, including the extracellular signal-regulated kinase (ERK1/2), P38, c-Jun N-terminal kinase (JNK) and the anti-apoptosis mediator protein kinase B (PKB/AKT). Cell-based ELISAs were also performed on the membrane anchoring protein vinculin and alpha6beta4 integrin. LIPUS stimulated activation of PERK 1/2, PJNK, PP38 and vinculin in traditional two-dimensional (2-D) culture. Calcium release from the scaffolds was partially involved in the activation of PERK 1/2 when cell response was compared between culture on 2-D surfaces and three-dimensional (3-D) HA and TCP scaffolds. Effects of calcium extracted media from scaffolds alone could not account for the full activation of PJNK, PP38, PAKT, vinculin and alpha6beta4 integrin. LIPUS stimulation further increased PERK activity on TCP scaffolds corresponding with an increase in both vinculin and alpha6beta4 integrin levels. It was concluded from this study that LIPUS treatment can significantly affect stress signaling mediators and adhesion proteins in osteoblast precursor cells during the early cell-attachment phase to trabecular patterned scaffolds.