Osteoblast growth on titanium foils coated with hydroxyapatite by pulsed laser ablation

There Are over 60 Ways to Produce Biocompatible Calcium Orthophosphate (CaPO4) Deposits on Various Substrates

A The present overview describes various production techniques for biocompatible calcium orthophosphate (abbreviated as CaPO4) deposits (coatings, films and layers) on the surfaces of various types of substrates to impart the biocompatible properties for artificial bone grafts. Since, after being implanted, the grafts always interact with the surrounding biological tissues at the interfaces, their surface properties are considered critical to clinical success. Due to the limited number of materials that can be tolerated in vivo, a new specialty of surface engineering has been developed to desirably modify any unacceptable material surface characteristics while maintaining the useful bulk performance. In 1975, the development of this approach led to the emergence of a special class of artificial bone grafts, in which various mechanically stable (and thus suitable for load-bearing applications) implantable biomaterials and artificial devices were coated with CaPO4. Since then, more than 7500 papers have been published on this subject and more than 500 new publications are added annually. In this review, a comprehensive analysis of the available literature has been performed with the main goal of finding as many deposition techniques as possible and more than 60 methods (double that if all known modifications are counted) for producing CaPO4 deposits on various substrates have been systematically described. Thus, besides the introduction, general knowledge and terminology, this review consists of two unequal parts. The first (bigger) part is a comprehensive summary of the known CaPO4 deposition techniques both currently used and discontinued/underdeveloped ones with brief descriptions of their major physical and chemical principles coupled with the key process parameters (when possible) to inform readers of their existence and remind them of the unused ones. The second (smaller) part includes fleeting essays on the most important properties and current biomedical applications of the CaPO4 deposits with an indication of possible future developments.

In-Vitro Phenotypic Response of Human Osteoblasts to Different Degrees of Titanium Surface Roughness

Objectives: This study aimed to investigate human osteoblast (HOB) responses towards different degrees of titanium (Ti) implant surface roughness. Methods: Four degrees of Ti surface roughness were investigated on a micrometer roughness scale: smooth (S: 0.08−0.1 µm), minimally rough (MM: 0.3−0.5 µm), moderately rough (MR: 1.2−1.4 µm), and rough (R: 3.3−3.7 µm). HOB cells were cultured, expanded, and maintained according to the supplier’s protocol. Cell proliferation and cytotoxicity were assessed at day 1, 3, 5, and 10 using alamarBlue and lactate dehydrogenase colorimetric assays. Data were analyzed with one-way ANOVA, two-way ANOVA, and Tukey’s post hoc test (p = 0.05 for all tests). Results: There was no significant difference in the cell proliferation or cytotoxicity of the HOB cells in contact with the different degrees of Ti surface roughness. There was, however, a significant time effect on cell proliferation (p < 0.0001) with different exposure durations for each roughness degree. Furthermore, a positive correlation (non-significant) between proliferation and cytotoxicity was observed for all investigated degrees of surface roughness. Conclusion: All investigated roughness degrees showed comparable HOB proliferation, with the MR surface presenting the highest percentage, followed by the R, MM, ad S, surfaces, respectively. The S surface showed the highest cytotoxic effect on HOBs; however, it did not reach the cytotoxic level suggested by the ISO for any medical device to be considered cytotoxic.

Characterization and Bone Response of Carbonate-Containing Apatite-Coated Titanium Implants Using an Aqueous Spray Coating

We performed thin carbonate-containing apatite (CA) coating on titanium (Ti) by an aqueous spray coating (ASC) method that consisted of a Ca-CO₃-PO₄ complex. Two different CA coatings were produced by two different spray amounts and were heat-treated after spraying. We evaluated three-dimensional structures, adhesiveness to Ti, and durability of the CA film. In addition, we performed immersion experiments in simulated body fluid (SBF), and bone responses were evaluated after implantation into a femoral bone defect in rats. The bonding ability of ASC-coated implant into the bone was examined by push-in tests. Unique network structures with small particles were identified on CA coatings. Although heat treatment produced no significant difference in surface morphology, scratch tests revealed that heat treatment improved the adhesion of CA coatings to Ti. Crystal formation progressed on CA-coated specimens, and the sample placement direction influenced crystal formation and growth in SBF immersion. Animal implantation experiments revealed significantly greater bone-to-implant contact ratio and bone mass in both cortical and bone marrow, respectively, four weeks after implantation. Push-in tests suggested that the bonding of the CA coating to Ti is clinically acceptable. Therefore, we conclude that CA coating to Ti by the ASC method would be possible for clinical applications, including dentistry.

Calcium Phosphate Bioceramics: A Review of Their History, Structure, Properties, Coating Technologies and Biomedical Applications

Calcium phosphate (CaP) bioceramics are widely used in the field of bone regeneration, both in orthopedics and in dentistry, due to their good biocompatibility, osseointegration and osteoconduction. The aim of this article is to review the history, structure, properties and clinical applications of these materials, whether they are in the form of bone cements, paste, scaffolds, or coatings. Major analytical techniques for characterization of CaPs, in vitro and in vivo tests, and the requirements of the US Food and Drug Administration (FDA) and international standards from CaP coatings on orthopedic and dental endosseous implants, are also summarized, along with the possible effect of sterilization on these materials. CaP coating technologies are summarized, with a focus on electrochemical processes. Theories on the formation of transient precursor phases in biomineralization, the dissolution and reprecipitation as bone of CaPs are discussed. A wide variety of CaPs are presented, from the individual phases to nano-CaP, biphasic and triphasic CaP formulations, composite CaP coatings and cements, functionally graded materials (FGMs), and antibacterial CaPs. We conclude by foreseeing the future of CaPs.

Calcium orthophosphate deposits: Preparation, properties and biomedical applications

Since various interactions among cells, surrounding tissues and implanted biomaterials always occur at their interfaces, the surface properties of potential implants appear to be of paramount importance for the clinical success. In view of the fact that a limited amount of materials appear to be tolerated by living organisms, a special discipline called surface engineering was developed to initiate the desirable changes to the exterior properties of various materials but still maintaining their useful bulk performances. In 1975, this approach resulted in the introduction of a special class of artificial bone grafts, composed of various mechanically stable (consequently, suitable for load bearing applications) implantable biomaterials and/or bio-devices covered by calcium orthophosphates (CaPO4) to both improve biocompatibility and provide an adequate bonding to the adjacent bones. Over 5000 publications on this topic were published since then. Therefore, a thorough analysis of the available literature has been performed and about 50 (this number is doubled, if all possible modifications are counted) deposition techniques of CaPO4 have been revealed, systematized and described. These CaPO4 deposits (coatings, films and layers) used to improve the surface properties of various types of artificial implants are the topic of this review.

Inorganic-organic thin implant coatings deposited by lasers

The lifetime of bone implants inside the human body is directly related to their osseointegration. Ideally, future materials should be inspired by human tissues and provide the material structure-function relationship from which synthetic advanced biomimetic materials capable of replacing, repairing, or regenerating human tissues can be produced. This work describes the development of biomimetic thin coatings on titanium implants to improve implant osseointegration. The assembly of an inorganic-organic biomimetic structure by UV laser pulses is reported. The structure consists of a hydroxyapatite (HA) film grown onto a titanium substrate by pulsed-laser deposition (PLD) and activated by a top fibronectin (FN) coating deposited by matrix-assisted pulsed laser evaporation (MAPLE). A pulsed KrF* laser source (λ = 248 nm, τ = 25 ns) was employed at fluences of 7 and 0.7J/cm(2) for HA and FN transfer, respectively. Films approximately 1500 and 450 nm thick were obtained for HA and FN, respectively. A new cryogenic temperature-programmed desorption mass spectrometry analysis method was employed to accurately measure the quantity of immobilized protein. We determined that less than 7 μg FN per cm(2) HA surface is adequate to improve adhesion, spreading, and differentiation of osteoprogenitor cells. We believe that the proposed fabrication method opens the door to combining and immobilizing two or more inorganic and organic materials on a solid substrate in a well-defined manner. The flexibility of this method enables the synthesis of new hybrid materials by simply tailoring the irradiation conditions according to the thermo-physical properties of the starting materials.

Non-mulberry silk fibroin influence osteogenesis and osteoblast-macrophage cross talk on titanium based surface

The titanium and its alloys are used as orthopedic dental implants due to their mechanical and bio-inert properties. The bare metal implants are not the ultimate answer for better osteogenesis and implant integration. Physical and chemical modifications are carried out to achieve the goal of improved adhesion and differentiation of the osteoblast. In this work, the silk fibroins from both mulberry and non-mulberry sources are used for surface modification. Silk fibroins are immobilized on titanium surface to facilitate the initial cell adhesion followed by improved cell spreading and better mineralization in order to achieve enhanced osseointegration. The immunological responses along with the effect of cytokines on osteoblast adhesion and function are investigated. The non-mulberry fibroin performs better in the context of the cell adherence and differentiation, which lead to better mineralization. The results indicate that the silk fibroin from non-mulberry source can be used for better osteogenesis on orthopedic implants.

Optimal Conditions of Electrostatic Spray Deposition (ESD) for Composite Biomaterials Coating for Biomedical Applications

Various types of metals and alloys are used for medical implants due to their excellent mechanical properties and corrosion resistance; however, their lacks of osteoinductive properties bring about the introduction of biomaterials which can help enhancing the bioactivity between the bones and the implants. Hydroxyapatite (Ca10(PO4)6(OH)2, or HA) which is one of the calcium phosphates that has similar mineral constituents of human bone, has been used as coating material to the metals/alloys substrate. Coating HA usually involves high-temperature such as the plasma spraying coating, which can alter the crystal structure of the HA partially become amorphous. The amorphous nature of HA lessen the benefits of coating with the biomaterial HA. Electrostatic spray deposition (ESD) was used in this research due to the fact that this process is simple, economical, and room-temperature operated. The preliminary results showed a promising thickness layer of about 40 μm; however, the adhesion of the coated layer to the stainless steel 316L was improved by mixing the HA powder with phosphate bioglass and cured in the vacuum furnace at 700oC. Taguchi experimental design technique was used for screening several ESD process parameters: powder feed rate, voltage, current, air volume, distances, time, and nozzle types to significant factors to the coated thickness of the ESD process. The results showed that feed rate, air volume, and time were the significant factors and then Full factorial analysis and response surface method was used for obtaining optimal conditions for the coating, as well as the predicted equation for determine the thickness coated layer with significant factors.

Calcium orthophosphate coatings, films and layers

In surgical disciplines, where bones have to be repaired, augmented or improved, bone substitutes are essential. Therefore, an interest has dramatically increased in application of synthetic bone grafts. As various interactions among cells, surrounding tissues and implanted biomaterials always occur at the interfaces, the surface properties of the implants are of the paramount importance in determining both the biological response to implants and the material response to the physiological conditions. Hence, a surface engineering is aimed to modify both the biomaterials, themselves, and biological responses through introducing desirable changes to the surface properties of the implants but still maintaining their bulk mechanical properties. To fulfill these requirements, a special class of artificial bone grafts has been introduced in 1976. It is composed of various mechanically stable (therefore, suitable for load bearing applications) biomaterials and/or bio-devices with calcium orthophosphate coatings, films and layers on their surfaces to both improve interactions with the surrounding tissues and provide an adequate bonding to bones. Many production techniques of calcium orthophosphate coatings, films and layers have been already invented and new promising techniques are continuously investigated. These specialized coatings, films and layers used to improve the surface properties of various types of artificial implants are the topic of this review.

Laser surface modification of titanium substrate for pulsed laser deposition of highly adherent hydroxyapatite

Biomedical implant devices made out of titanium and its alloys are benefited by a modified surface or a bioactive coating to enhance bone bonding ability and to function effectively in vivo for the intended period of time. In this respect hydroxyapatite coating developed through pulsed laser deposition is a promising approach. Since the success of the bioactive ceramic coated implant depends mainly on the substrate-coating strength; an attempt has been made to produce micro patterned surface structure on titanium substrate for adherent hydroxyapatite coating. A pulsed Nd-YAG laser beam (355 nm) with 10 Hz repetition rate was used for surface treatment of titanium as well as hydroxyapatite deposition. The unfocussed laser beam was used to modify the substrate surface with 500-18,000 laser pulses while keeping the polished substrate in water. Hydroxyapatite deposition was done in a vacuum deposition chamber at 400 °C with the focused laser beam under 1 × 10⁻³ mbar oxygen pressure. Deposits were analyzed to understand the physico-chemical, morphological and mechanical characteristics. The obtained substrate and coating surface morphology indicates that laser treatment method can provide controlled micro-topography. Scratch test analysis and microindentation hardness values of coating on laser treated substrate indicate higher mechanical adhesion with respect to coatings on untreated substrates.

Functional Coatings or Films for Hard-Tissue Applications

Metallic biomaterials like stainless steel, Co-based alloy, Ti and its alloys are widely used as artificial hip joints, bone plates and dental implants due to their excellent mechanical properties and endurance. However, there are some surface-originated problems associated with the metallic implants: corrosion and wear in biological environments resulting in ions release and formation of wear debris; poor implant fixation resulting from lack of osteoconductivity and osteoinductivity; implant-associated infections due to the bacterial adhesion and colonization at the implantation site. For overcoming these surface-originated problems, a variety of surface modification techniques have been used on metallic implants, including chemical treatments, physical methods and biological methods. This review surveys coatings that serve to provide properties of anti-corrosion and anti-wear, biocompatibility and bioactivity, and antibacterial activity.

Crystallographically engineered, hydrothermally crystallized hydroxyapatite films: an in vitro study of bioactivity

The aim of this study was to evaluate the bioactivity of hydroxyapatite films composed of hexagonal single crystals that display {1010} and {0001} crystallographic faces. The effect of engineered [0001] crystallographic orientation was investigated in parallel. Films were deposited by triethyl phosphate/ethylenediamine-tetraacetic acid doubly regulated hydrothermal crystallization on Ti6Al4V substrates (10, 14, 24 h). Bioactivity was investigated by analysis of MC3T3-E1 pre-osteoblast spreading using scanning electron microscopy and quantitative analysis of cell metabolic activity (Alamar Blue) (0-28 days). Scanning electron microscopy and X-ray diffraction were used to evaluate the ability of films to support the differentiation of MC3T3-E1 pre-osteoblasts into matrix-secreting, mineralizing osteoblasts. Results demonstrated that all films enabled MC3T3-E1 cells to spread, grow, and differentiate into matrix-secreting osteoblasts, which deposited biomineral that could not be removed after extraction of organic material. Differences in [0001] HA crystallographic orientation were not, however, found to significantly affect bioactivity. Based on these results, it is concluded that these hydrothermal hydroxyapatite films are non-toxic, bioactive, osteoconductive, and biomineral bonding. The lack of a relationship between reported hydroxyapatite crystallographic face specific protein adsorption and bulk HA bioactivity are discussed in terms of crystallographic texture, surface roughness, assay robustness, and competitive protein adsorption.

Physicochemical investigation of pulsed laser deposited carbonated hydroxyapatite films on titanium

Carbonated hydroxyapatite (CHA)-coated titanium can find wide applications as bone substitute implant in bone and dental surgery and orthopedics, promoting osseointegration with a host bone and ensuring biocompatibility and bioactivity. In this work, carbonated hydroxyapatite films were prepared on titanium substrates by pulsed laser deposition at different substrate temperatures ranging from 30 to 750 degrees C. The properties of films were investigated by scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray diffraction, and Fourier transform infrared spectroscopy. Vickers microhardness measurements of the composite film-substrate systems were performed, and the intrinsic hardness of films was separated from the composite hardness using a "law-of-mixtures" approach and taking into account the indentation size effect. The prepared CHA films are nearly stoichiometric with a Ca/P atomic ratio of 2.0-2.2. The films deposited in the 30-500 degrees C temperature range are about 9 microm thick, amorphous, having an average roughness of 60 nm. At higher temperature, 700-750 degrees C, the films are about 4 microm thick, show a finer surface morphology and an average roughness of 20 nm. At 750 degrees C the films are amorphous, whereas at 700 degrees C they are crystalline and textured along the (202) and (212) directions. The intrinsic hardness of the films increased with an increase in substrate temperature, being as low as 5 GPa at 30 degrees C and reaching a high value of 28 GPa at 700 degrees C. The rich information gained by the joint use of the mentioned techniques allowed a comprehensive characterization of this system.

Biocompatibility and osteogenic potential of human fetal femur-derived cells on surface selective laser sintered scaffolds

For optimal bone regeneration, scaffolds need to fit anatomically into the requisite bone defects and, ideally, augment cell growth and differentiation. In this study we evaluated novel computationally designed surface selective laser sintering (SSLS) scaffolds for their biocompatibility as templates, in vitro and in vivo, for human fetal femur-derived cell viability, growth and osteogenesis. Fetal femur-derived cells were successfully cultured on SSLS-poly(d,l)-lactic acid (SSLS-PLA) scaffolds expressing alkaline phosphatase activity after 7days. Cell proliferation, ingrowth, Alcian blue/Sirius red and type I collagen positive staining of matrix deposition were observed for fetal femur-derived cells cultured on SSLS-PLA scaffolds in vitro and in vivo. SSLS-PLA scaffolds and SSLS-PLA scaffolds seeded with fetal femur-derived cells implanted into a murine critical-sized femur segmental defect model aided the regeneration of the bone defect. SSLS techniques allow fabrication of biocompatible/biodegradable scaffolds, computationally designed to fit any defect, providing a template for cell osteogenesis in vitro and in vivo.

In vitro study of hydroxyapatite-based photocurable polymer composites prepared by laser stereolithography and supercritical fluid extraction

The fabrication of three-dimensional (3-D) structures using computer-controlled ultraviolet (UV) photopolymerization of acrylates (laser stereolithography) often results in the trapping of residual unreacted monomer and initiator. These residuals can leach from the finished structure and affect the biological response of cells and tissues. Thus the potential applications of these structures for tissue engineering have not been fully realized. In this paper we demonstrate that conventional post-lithography treatments followed by processing in the environmentally benign solvent, supercritical carbon dioxide (scCO(2)), dramatically increased biocompatibility. The scCO(2) processing of pure polyacrylate and polyacrylate/hydroxyapatite composite structures extracts residuals from all structures including those that had received full conventional post-lithography treatment (acetone washing/UV drying). Human osteoblast cells seeded on the extracted surfaces of these structures demonstrated increased cell attachment and proliferation on the scCO(2)-treated materials.

The Role of Nitric Oxide on the Proliferation of a Human Osteoblast Cell Line Stimulated With Hydroxyapatite

The aim of the present study was to test the hypothesis that the proliferation of a human osteoblast cell line (HOS cells) stimulated with hydroxyapatite (HA) may be regulated by nitric oxide (NO). The cells were cultured on the surface of HA. Medium or cells alone were used as controls. L-arginine, D-arginine, 7-NI (an nNOS inhibitor), L-NIL (an iNOS inhibitor), L-NIO (an eNOS inhibitor) or carboxy PTIO, a NO scavenger, was added in the HA-exposed cell cultures. The cells were also precoated with anti-human integrin αV antibody. The levels of nitrite were determined spectrophotometrically. Cell proliferation was assessed by colorimetric assay. The results showed increased nitrite production and cell proliferation by HA-stimulated HOS cells up to day 3 of cultures. Anti-integrin αV antibody, L-NIO, or carboxy PTIO suppressed, but L-arginine enhanced, nitrite production and cell proliferation of HA-stimulated HOS cells. The results of the present study suggest, therefore, that interaction between HA and HOS cell surface integrin αV molecule may activate eNOS to catalyze NO production which, in turn, may regulate the cell proliferation in an autocrine fashion.

Biocompatibility evaluation of a novel hydroxyapatite-polymer coating for medical implants (in vitro tests)

Nanocomposites consisting of hydroxyapatite (HA) and a sodium maleate copolymer (maleic polyelectrolyte), synthesized by hydrothermal method and deposited on titanium substrates by Matrix Assisted Pulsed Laser Evaporation (MAPLE) technique were tested for the biological properties. Coating bioanalysis was carried out by triple staining of actin, microtubules and nuclei followed by immunofluorescence microscopy. Within 24 h cells that occupied the biomaterial surface displayed the morphology and cytoskeleton pattern similar to the controls. Cells grown on nanocomposite coated surfaces had a higher proliferation rate than their counterparts grown on Ti coated with HA alone, indicating that maleic polyelectrolyte improved surface bio-adhesive characteristics. The capacity to induce cell attachment, spreading and proliferation demonstrated the potential of Ti coated with HA-polymer nanocomposites to be used as scaffolds in dental or orthopedic implantology.

Cytocompatibility of calcium phosphate coatings deposited by an ArF pulsed laser

In the current studies, we deposited ultra-thin hydroxyapatite films on a pure titanium substrate by pulsed laser deposition, and we examined the effects of these surfaces on rat bone marrow (RBM) cells. This method allowed deposition of 500-, 2,000-, and 5,000-A-thick hydroxyapatite films. X-ray diffraction showed that the amorphous films recrystallized to a hydroxyapatite crystal structure after annealing. The proliferation of RBM cells was unaffected by the hydroxyapatite films, but osteocalsin and alkaline phosphatase mRNA and protein levels were elevated in cells grown on 2,000- and 5,000-A-thick films. These results indicate that ultra-thin hydroxyapatite films generated by pulsed laser deposition are better at promoting osteogenesis than pure titanium surfaces.

Human osteoblast cell spreading and vinculin expression upon biomaterial surfaces

Any biomaterial implanted within the human body is influenced by the interactions that take place between its surface and the surrounding biological milieu. These interactions are known to influence the tissue interface dynamic, and thus act to emphasize the need to study cell-surface interactions as part of any biomaterial design process. The work described here investigates the relationship between human osteoblast attachment, spreading and focal contact formation on selected surfaces using immunostaining and digital image processing for vinculin, a key focal adhesion component. Our observations show that a relationship exists between levels of cell attachment, the degree of vinculin-associated plaque formation and biocompatibility. It also suggests that cell adhesion is not indicative of how supportive a substrate is to cell spreading, and that cell spreading does not correlate with focal contact formation.

Cytocompatibility of calcium phosphate coatings deposited by an ArF pulsed laser

In the current studies, we deposited ultra-thin hydroxyapatite films on a pure titanium substrate by pulsed laser deposition, and we examined the effects of these surfaces on rat bone marrow (RBM) cells. This method allowed deposition of 500-, 2000-, and 5000-Angstrom-thick hydroxyapatite films. X-ray diffraction showed that the amorphous films recrystallized to a hydroxyapatite crystal structure after annealing. The proliferation of RBM cells was unaffected by the hydroxyapatite films, but osteocalsin and alkaline phosphatase mRNA and protein levels were elevated in cells grown on 2000- and 5000-Angstrom-thick films. These results indicate that ultra-thin hydroxyapatite films generated by pulsed laser deposition are better at promoting osteogenesis than pure titanium surfaces.

Effect of calcium, zinc and magnesium on the attachment and spreading of osteoblast like cells onto ceramic matrices

Calcium phosphate ceramic has been widely used as bone substitute materials. Neumerours approaches have been investigated to develop tissue-engineered scaffold from hydroxyapatite because of its advantages like osteoconduction. We have developed porous ceramic matrices from nanoparticles of calcium phosphate containing zinc and magnesium. Mimicking the grain size of natural bone enhances the bone forming function of cells. Osteoblast-like MG63 cells were cultured on to these porous ceramic matrices. Cell adhesion and spreading onto these matrices were studied for 24 h and 5 days in vitro. It was observed that on calcium phosphate matrix, containing a combination of zinc and magnesium, the osteoblast adhesion and spreading was significant on 5th day. This appeared to be comparable to the hydroxyapatite control. This makes it a promising candidate as a bone tissue-engineering scaffold.

Ion implantation modified stainless steel as a substrate for hydroxyapatite deposition. Part I. Surface modification and characterization

Material surfaces play critical role in biology and medicine since most biological reactions occur on surfaces and interfaces. There are many examples showing that the surface properties of the materials control and are directly involved in biological reactions and processes in-vitro like blood compatibility, protein absorption, cell development, etc. The rules that govern the diversity of biological surface phenomenon are fundamental physical laws. Stainless steel doped with Cr, Ni and Mo is widely used material in medicine and dentistry due to its excellent corrosion resistance and mechanical properties. The interest in this material has stimulated extensive studies on improving its bone-bonding properties. This paper describes the surface modification of Cr-Ni stainless steel (AISI 316) by a whole surface sequential implantation of Ca and P ions (the basic ions of hydroxyapatite). Three groups of stainless steel samples are prepared: (i) ion-implanted, (ii) ion-implanted and thermally treated at 600( composite function)C in air for 1 h and (iii) initials. The surface chemistry and topography before and after the surface modification are characterized by X-ray photoelectron spectroscopy, Auger electron spectroscopy, magic mirror method, atomic force microscopy and contact angle measurements.

Human osteoblast response to pulsed laser deposited calcium phosphate coatings

Octacalcium phosphate (OCP) and Mn(2+)-doped carbonate hydroxyapatite (Mn-CHA) thin films were deposited on pure, highly polished and chemically etched Ti substrates with pulsed laser deposition. The coatings exhibit different composition, crystallinity and morphology that might affect their osteoconductivity. Human osteoblasts were cultured on the surfaces of OCP and Mn-CHA thin films, and the cell attachment, proliferation and differentiation were evaluated up to 21 days. The cells showed a normal morphology and a very good rate of proliferation and viability in every experimental time. Alkaline phosphatase activity was always higher than the control and Ti groups. From days 7 to 21 collagen type I production was higher in comparison with control and Ti groups. The level of transforming growth factor beta 1 (TGF-beta1) was lower at 3 and 7 days, but reached the highest values during following experimental times (14 and 21 days). Our data demonstrate that both calcium phosphate coatings favour osteoblasts proliferation, activation of their metabolism and differentiation.

In Vitro Biocompatibility of a New Titanium-29Niobium-13Tantalum-4.6Zirconium Alloy With Osteoblast-Like MG63 Cells

BACKGROUND

Titanium-29niobium-13tantalum-4.6zirconium (TiNb) has recently been developed as a new implant material. TiNb is composed of non-toxic elements and has a lower modulus of elasticity than the other titanium alloys. However, its biocompatibility has not been adequately characterized. The aim of this study was to evaluate the biocompatibility of TiNb using an osteoblast-titanium co-culture system.

METHODS

MG63 cells were cultured on three kinds of titanium disks: TiNb, pure titanium (pTi), and titanium-6aluminum-4vanadium (TiAl), prepared with two different surfaces, a polished and acid-etched surface and a machined-grooved surface. The surface topography and roughness were evaluated by scanning electron microscopy (SEM). After 48 hours culture, the number of proliferating cells and prostaglandin E2 (PGE2) production in the culture supernatant were determined.

RESULTS

There was no significant difference in surface roughness among the three titanium disks with a polished and acid-etched surface. After 48 hours of culture, the number of cells was significantly reduced on pTi and TiAl compared to TiNb and the control. PGE2 production was significantly higher on pTi than on TiAl, TiNb, and the control. We further examined the effect of surface roughness on PGE2 production using machine-grooved titanium disks. While pTi and TiAl stimulated the production of PGE2 depending on surface roughness, roughened TiNb did not affect PGE2 production.

CONCLUSIONS

These results suggest that TiNb may exhibit favorable biocompatibility because it has an efficient surface topography for cell proliferation, and the level of PGE2 production does not depend on surface roughness. We conclude that TiNb may be useful as an implant material.

Biocompatible Mn2+-doped carbonated hydroxyapatite thin films grown by pulsed laser deposition

Mn(2+)-doped carbonated hydroxyapatite (Mn-CHA) thin films were obtained by pulsed laser deposition on Ti substrates. The results of the performed complementary diagnostic techniques, X-ray diffraction, infrared spectroscopy, X-ray photoelectron spectroscopy, and energy dispersive X-ray spectroscopy investigations indicate that the films are crystalline with a Ca/P ratio of about 1.64-1.66. The optimum conditions, when nearly stoichiometric crystalline thin films were deposited, were found to be 10 Pa oxygen pressure, 400 degrees C substrate temperature, and postdeposition heat treatment in water vapors at the same substrate temperature. The films were seeded with L929 fibroblast and hFOB1.19 osteoblast cells and subjected to in vitro tests. Both fibroblast and osteoblast cells have a good adherence on the Mn-CHA film and on the Ti or polystyrene references. Proliferation and viability tests showed that osteoblast cells growth on Mn-CHA-coated Ti was enhanced as compared to uncoated pure Ti surfaces. Caspase-1 activity was not affected significantly by the material, showing that Mn-CHA does not induce apoptosis of cultured cells. These results demonstrate that Mn-CHA films on Ti should provoke a faster osteointegration of the coated implants as compared to pure Ti. (c) 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 353-358, 2004.

Physiological strains induce differentiation in human osteoblasts cultured on orthopaedic biomaterial

We have developed an in vitro mechanical stretching model of osteoblastic cells cultured on metallic biomaterials in order to study the effects of mechanical strain on osteointegration of orthopaedic implants. Titanium alloy discs coated with alumina or hydroxyapatite were used as substrates. Three Dynacell devices were especially designed to apply cyclic strains on rigid biomaterials. The regimen (600 mu epsilon strains, 0.25Hz) was defined on the basis of physiological data and estimated deformation on hip stem prostheses. The performances of these apparatus were reproducible and provided controlled deformations. Human osteosarcoma cell line MG-63, human osteoblasts obtained from primary cultures and ROS 17/2.8 rat osteosarcoma cells were used as cell models. Cell behaviour was assessed in terms of growth and alkaline phosphatase (ALP) activity by in situ assays for two regimens: 15-min deformations repeated three times a day to mimic rehabilitation exercises and 24-h continuous deformations. We demonstrated that continuous deformation did not affect the growth and ALP activity of MG-63 cells, in contrast with sequential deformations which had no effect on cell number, but which stimulated ALP activity after 5 days of stretching. This sequential regimen can also modify the behaviour of human bone-derived cells resulting in increased proliferation after 5 days and stimulation of ALP activity after 15 days. ROS 17/2.8 rat osteosarcoma cells submitted to sequential deformations responded faster than other cell lines by increasing their ALP activity only after 1 day of stretching. Like MG-63 cells, proliferation of the ROS 17/2.8 rat osteosarcoma cell line was not affected by sequential deformations. This study suggests that short, repeated deformations defined to mimic rehabilitation exercises recommended after prostheses implantation are more likely to exert beneficial effects on implanted bone than continuous strains.

Chemically patterned, metal-oxide-based surfaces produced by photolithographic techniques for studying protein- and cell-interactions. II: Protein adsorption and early cell interactions

Protein adsorption and adhesion of primary human osteoblasts on chemically patterned, metal-oxide-based surfaces comprising combinations of titanium, aluminium, vanadium and niobium were investigated. Single metal samples with a homogeneous surface and bimetal samples with a surface pattern produced by photolithographic techniques were used. The physical and chemical properties of the samples have been extensively characterised and are presented in a companion paper. Here, we describe their properties in terms of cell responses during the initial 24h of cell culture. Regarding the cell number and activity there was no significant difference between any of the single metal surfaces. However the morphology of cells on vanadium surfaces became spindle-like. In contrast to the behaviour on single metal samples, cells exhibited a pronounced reaction on bimetallic surfaces that contained aluminium. Cells tended to stay away from aluminium, which was the least favoured metal in all two-metal combinations. An initial cell alignment relative to the pattern geometry was detectable after 2h and was fully developed after 18h of incubation. The organisation of f-actin and microtubules as well as the localisation of vinculin were all more pronounced on non-aluminium regions. We hypothesised that the differences in cell response could be associated with differences in the adsorption of serum proteins onto the various metal oxides. Protein adsorption experiments were performed using microscopy in conjunction with immunofluorescent stains. They indicated that both fibronectin and albumin adsorption were significantly greater on the non-aluminium regions, suggesting that differences in cellular response correlate with a modulation of the concentration of serum proteins on the surface.