Surface oxide net charge of a titanium alloy: modulation of fibronectin-activated attachment and spreading of osteogenic cells

Effects of Nanomaterials on Synthesis and Degradation of the Extracellular Matrix

Extracellular matrix (ECM) remodeling is accompanied by the continuous synthesis and degradation of the ECM components. This dynamic process plays an important role in guiding cell adhesion, migration, proliferation, and differentiation, as well as in tissue development, body repair, and maintenance of homeostasis. Nanomaterials, due to their photoelectric and catalytic properties and special structure, have garnered much attention in biomedical fields for use in processes such as tissue engineering and disease treatment. Nanomaterials can reshape the cell microenvironment by changing the synthesis and degradation of ECM-related proteins, thereby indirectly changing the behavior of the surrounding cells. This review focuses on the regulatory role of nanomaterials in the process of cell synthesis of different ECM-related proteins and extracellular protease. We discuss influencing factors and possible related mechanisms of nanomaterials in ECM remodeling, which may provide different insights into the design and development of nanomaterials for the treatment of ECM disorder-related diseases.

Fibronectin Conformations after Electrodeposition onto 316L Stainless Steel Substrates Enhanced Early-Stage Osteoblasts' Adhesion but Affected Their Behavior

The implantation of metallic orthopedic prostheses is increasingly common due to an aging population and accidents. There is a real societal need to implement new metal implants that combine durability, good mechanical properties, excellent biocompatibility, as well as affordable costs. Since the functionalization of low-cost 316L stainless steel substrates through the successive electrodeposition of a polypyrrole film (PPy) and a calcium phosphate deposit doped with silicon was previously carried out by our labs, we have also developed a bio-functional coating by electrodepositing or oxidating of fibronectin (Fn) coating. Fn is an extracellular matrix glycoprotein involved in cell adhesion and differentiation. Impacts of either electrodeposition or oxidation on the structure and functionality of Fn were first studied. Thus, electrodeposition is the technique that permits the highest deposition of fibronectin, compared to adsorption or oxidation. Furthermore, electrodeposition seems to strongly modify Fn conformation by the formation of intermingled long fibers, resulting in changes to the accessibility of the molecular probes tested (antibodies directed against Fn whole molecule and Fn cell-binding domain). Then, the effects of either electrodeposited Fn or oxidized Fn were validated by the resulting pre-osteoblast behavior. Electrodeposition reduced pre-osteoblasts' ability to remodel Fn coating on supports because of a partial modification of Fn conformation, which reduced accessibility to the cell-binding domain. Electrodeposited Fn also diminished α5 integrin secretion and clustering along the plasma membrane. However, the N-terminal extremity of Fn was not modified by electrodeposition as demonstrated by Staphylococcus aureus attachment after 3 h of culture on a specific domain localized in this region. Moreover, the number of pre-osteoblasts remains stable after 3 h culture on either adsorbed, oxidized, or electrodeposited Fn deposits. In contrast, mitochondrial activity and cell proliferation were significantly higher on adsorbed Fn compared with electrodeposited Fn after 48 h culture. Hence, electro-deposited Fn seems more favorable to pre-osteoblast early-stage behavior than during a longer culture of 24 h and 48 h. The electrodeposition of matrix proteins could be improved to maintain their bio-activity and to develop this promising, fast technique to bio-functionalize metallic implants.

Lithium-Modified TiO2 Surface by Anodization for Enhanced Protein Adsorption and Cell Adhesion

Promoting osseointegration is an essential step in improving implant success rates. Lithium has gradually gained popularity for promoting alkaline phosphatase activity and osteogenic gene expression in osteoblasts. The incorporation of lithium into a titanium surface has been reported to change its surface charge, thereby enhancing its biocompatibility. In this study, we applied anodization as a novel approach to immobilizing Li on a titanium surface and evaluated the changes in its surface characteristics. The objective of this study was to determine the effect of Li treatment of titanium on typical proteins, such as albumin, laminin, and fibronectin, in terms of their adsorption level as well as on the attachment of osteoblast cells. Titanium disks were acid-etched by 66 wt % H2SO4 at 120 °C for 90 s and set as the control group. The etched samples were placed in contact with an anode, while a platinum bar served as the counter electrode. Both electrodes were mounted on a custom electrochemical cell filled with 1 M LiCl. The samples were anodized at constant voltages of 1, 3, and 9 V. Scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) results showed no significant differences in the topography. However, the ζ potentials of the 3 V group were higher than those of the control group at a physiological pH of 7.4. Interestingly, the adsorption level of the extracellular matrix protein was mostly enhanced on the 3 V-anodized surface. The number of attached cells on the Li-anodized surfaces increased. The localization of vinculin at the tips of the stretching cytoplasmic projections was observed more frequently in the osteoblasts on the 3 V-anodized surface. Although the optimal concentration or voltage for Li application should be investigated further, this study suggests that anodization could be an effective method to immobilize lithium ions on a titanium surface and that modifying the surface charge characteristics enables a direct protein-to-material interaction with enhanced biological adhesion.

Modulation of Cell Response through the Covalent Binding of Fibronectin to Titanium Substrates

Titanium (Ti-6Al-4V) substrates were functionalized through the covalent binding of fibronectin, and the effect of the existence of this extracellular matrix protein on the surface of the material was assessed by employing mesenchymal stem cell (MSC) cultures. The functionalization process comprised the usage of the activation vapor silanization (AVS) technique to deposit a thin film with a high surface density of amine groups on the material, followed by the covalent binding of fibronectin to the amine groups using the N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide (EDC/NHS) crosslinking chemistry. The biological effect of the fibronectin on murine MSCs was assessed in vitro. It was found that functionalized samples not only showed enhanced initial cell adhesion compared with bare titanium, but also a three-fold increase in the cell area, reaching values comparable to those found on the polystyrene controls. These results provide compelling evidence of the potential to modulate the response of the organism to an implant through the covalent binding of extracellular matrix proteins on the prosthesis.

The influence of nanotopography on cell behaviour through interactions with the extracellular matrix – A review

Nanotopography presents an effective physical approach for biomaterial cell manipulation mediated through material-extracellular matrix interactions. The extracellular matrix that exists in the cellular microenvironment is crucial for guiding cell behaviours, such as determination of integrin ligation and interaction with growth factors. These interactions with the extracellular matrix regulate downstream mechanotransductive pathways, such as rearrangements in the cytoskeleton and activation of signal cascades. Protein adsorption onto nanotopography strongly influences the conformation and distribution density of extracellular matrix and, therefore, subsequent cell responses. In this review, we first discuss the interactive mechanisms of protein physical adsorption on nanotopography. Secondly, we summarise advances in creating nanotopographical features to instruct desired cell behaviours. Lastly, we focus on the cellular mechanotransductive pathways initiated by nanotopography. This review provides an overview of the current state-of-the-art designs of nanotopography aiming to provide better biomedical materials for the future.

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A comprehensive overview of nanotopography fabrication, and nanotopography regulates various cell behaviours.

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The interactive physical adsorption between nanotopography and extracellular matrix.

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Nanotopography initiates the cellular mechanotransductive pathways and downstream signalling cascades.

Integrated osteochondral differentiation of mesenchymal stem cells on biomimetic nanofibrous mats with cell adhesion-generated piezopotential gradients

Biomimetic piezoelectric scaffolds provide a noninvasive method for in vivo cell regulation and tissue regeneration. Herein, considering the gradually varied piezoelectric properties of native cartilage and bone tissues, we fabricated biomimetic electrospun poly(L-lactic acid) (PLLA) nanofibrous mats with gradient piezoelectric properties to induce the integrated osteochondral differentiation of rat mesenchymal stem cells (MSCs). Nanofibrous mats are polarized under electric fields with linear variation of strength to generate gradient piezoelectricity, and cell adhesion-derived contraction forces could produce gradient piezoelectric potential on the scaffolds. Our results demonstrated that the piezoelectric potential could positively modulate cell adhesion, intracellular calcium transients, Ca²⁺ binding proteins, and differentiation-related genes. In addition, the differentiation of MSCs into osteogenic and chondrogenic lineages was integrated on a single scaffold at different areas with relatively high and low piezoelectricity values, respectively. The continuous gradient scaffold exhibited the potential to provide a smooth transition between the cartilage and bone, offering new insights to probe the regeneration mechanisms of the osteochondral tissue in a single scaffold and inspiring a future efficient and rational design of piezoelectric smart biomaterials for tissue engineering.

Titanium and Protein Adsorption: An Overview of Mechanisms and Effects of Surface Features

Titanium and its alloys, specially Ti6Al4V, are among the most employed materials in orthopedic and dental implants. Cells response and osseointegration of implant devices are strongly dependent on the body-biomaterial interface zone. This interface is mainly defined by proteins: They adsorb immediately after implantation from blood and biological fluids, forming a layer on implant surfaces. Therefore, it is of utmost importance to understand which features of biomaterials surfaces influence formation of the protein layer and how to guide it. In this paper, relevant literature of the last 15 years about protein adsorption on titanium-based materials is reviewed. How the surface characteristics affect protein adsorption is investigated, aiming to provide an as comprehensive a picture as possible of adsorption mechanisms and type of chemical bonding with the surface, as well as of the characterization techniques effectively applied to model and real implant surfaces. Surface free energy, charge, microroughness, and hydroxylation degree have been found to be the main surface parameters to affect the amount of adsorbed proteins. On the other hand, the conformation of adsorbed proteins is mainly dictated by the protein structure, surface topography at the nano-scale, and exposed functional groups. Protein adsorption on titanium surfaces still needs further clarification, in particular concerning adsorption from complex protein solutions. In addition, characterization techniques to investigate and compare the different aspects of protein adsorption on different surfaces (in terms of roughness and chemistry) shall be developed.

Effects of Surface Modification on Adsorption Behavior of Cell and Protein on Titanium Surface by Using Quartz Crystal Microbalance System

Primary stability and osseointegration are major challenges in dental implant treatments, where the material surface properties and wettability are critical in the early formation of hard tissue around the implant. In this study, a quartz crystal microbalance (QCM) was used to measure the nanogram level amount of protein and bone marrow cells adhered to the surfaces of titanium (Ti) surface in real time. The effects of ultraviolet (UV) and atmospheric-pressure plasma treatment to impart surface hydrophilicity to the implant surface were evaluated. The surface treatment methods resulted in a marked decrease in the surface carbon (C) content and increase in the oxygen (O) content, along with super hydrophilicity. The results of QCM measurements showed that adhesion of both adhesive proteins and bone marrow cells was enhanced after surface treatment. Although both methods produced implants with good osseointegration behavior and less reactive oxidative species, the samples treated with atmospheric pressure plasma showed the best overall performance and are recommended for clinical use. It was verified that QCM is an effective method for analyzing the initial adhesion process on dental implants.

The change of surface charge by lithium ion coating enhances protein adsorption on titanium

Surface charge is one of the essential physicochemical properties of titanium surfaces for extracellular protein adsorption. Titanium surfaces are generally electronegatively charged at physiological pH. Typical cellular adhesive proteins and cell membranes are also negatively charged. Therefore, there are no direct electric interactions between proteins and titanium surfaces at physiological pH. The objective of this study was to determine how different electrical charges on titanium surfaces affect protein adsorption. Commercially pure grade-2 titanium disks, 19 mm in diameter and 1.5 mm in thickness, having acid-etched micro-roughed surfaces, were prepared. Electropositive charge was supplied by soaking in LiOH solution at concentrations of 0.05, 0.1, 0.25, 0.5, and 1.0 M. After LiOH treatment, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were performed. The zeta potential, isoelectric point, and wettability of titanium surfaces were measured. The adsorption levels of proteins, including albumin, laminin, and fibronectin, were evaluated. Osteoblastic cell attachment level was also determined. Incorporation of Li was detected in the oxide layer of titanium without surface morphological modification. The zeta potential was shifted up and the isoelectric point was increased from 3.94 to 5.63 by LiOH treatment. Long-term super-hydrophilicity was also obtained on Li-treated surfaces. The adsorption of albumin and laminin increased with increasing concentration of LiOH treatment solution, whereas fibronectin adsorption was highest upon treatment with 0.25 M. The osteoblastic cell attachment level was shown to be dependent on the amount of fibronectin adsorbed. In conclusion, LiOH treatment enhances biological adhesion on titanium with an increase in surface charge and hydrophilicity. This study suggests that modifying the surface charge provides a direct protein-to-materials interaction and the optimal application of Li should be investigated further.

Composite Lipid Bilayers from Cell Membrane Extracts and Artificial Mixes as a Cell Culture Platform

An artificial lipid bilayer is the closest possible model for the cell membrane. Despite that, current methods of lipid bilayer assembly and functionalization do not provide a satisfactory mimic of the cell-cell contact due to the inability to recreate an asymmetrical multicomponent system. In the current work, a method to produce an integrated solid-supported lipid bilayer combining natural extracts from cell membranes and artificially made lipid vesicles is proposed. This simple method allows delivery of transmembrane proteins and components of the extracellular matrix into the substrate. Biocompatibility of the composite natural/artificial lipid bilayers is evaluated by their interactions with the cardiomyocyte-like HL-1 cell line. Compared with fully artificial mixes, composite lipid bilayers allow cells to adhere and develop a morphologically more normal cytoskeleton.

Preparation and cytocompatibility of a novel bismuth aluminate/calcium phosphate cement with high radiopacity

In a minimally invasive surgery, using a bone cement being radiologically detectable is vital to the success of the procedure and avoiding cement leakage in the early stage. The radiopacity of calcium phosphate cement (CPC) is inadequate, thus limiting its clinic application in this area. In this work, bismuth aluminate (BiA) was employed as a radiopaque agent for CPC. The influences of BiA on physicochemical, radiopaque and in vitro biocompatible properties of CPC were investigated. With the increasing content of BiA, the setting time and the compressive strength of CPC were augmented, while the injectability of the cement pastes was reduced. The radiopacity of CPC was significantly improved by adding more than 6 wt.% BiA. CPC specimens with less than 12 wt.% BiA showed good cellular affinity. Moreover, the CPC containing 6 and 9 wt.% BiA promoted the cell growth and ALP activity of mouse bone marrow mesenchymal stem cells when compared with the control. On the basis of its improved radiopacity and cytocompatibility, the radiopaque CPC with 6 ~ 9 wt.% BiA is expected to be a potential substitute for bone defect restoration via minimally invasive surgery. CPC with bismuth aluminate reveals better radiopacity and cell affinity along with proper physicochemical properties.

The impact of photofunctionalized gold nanoparticles on osseointegration

OBJECTIVES

The aims of this study were to create a new surface topography using simulated body fluids (SBF) and Gold Nanoparticles (GNPs) and then to assess the influence of UV Photofunctionalization (PhF) on the osteogenic capacity of these surfaces.

MATERIALS AND METHODS

Titanium plates were divided into six groups All were acid etched with 67% Sulfuric acid, 4 were immersed in SBF and 2 of these were treated with 10 nm GNPs. Half of the TiO2 plates were photofunctionalized to be compared with the non-PhF ones. Rat's bone marrow stem cells were seeded into the plates and then CCK8 assay, cell viability assay, immunofluorescence, and Scanning electron microscopy (SEM) were done after 24 hours. Gene expression analysis was done using real time quantitative PCR (qPCR) one week later to check for the mRNA expression of Collagen-1, Osteopontin and Osteocalcin. Alkaline phosphatase (ALP) activity was assessed after 2 weeks of cell seeding.

RESULTS

Our new topography has shown remarkable osteogenic potential. The new surface was the most biocompatible, and the 10 nm GNPs did not show any cytotoxicity. There was a significant increase in bioactivity, enhanced gene expressions and ALP activity.

CONCLUSIONS

GNPs enhances osteogenic differentiation of stem cells and Photofunctionalizing GNPs highly increases this. We have further created a novel highly efficient topography which highly enhances the speed and extent of osseointegration. This may have great potential for improving treatment outcomes for implant, maxillofacial as well as orthopedic patients.

Impact of surface topography and coating on osteogenesis and bacterial attachment on titanium implants

Titanium (Ti) plays a predominant role as the material of choice in orthopaedic and dental implants. Despite the majority of Ti implants having long-term success, premature failure due to unsuccessful osseointegration leading to aseptic loosening is still too common. Recently, surface topography modification and biological/non-biological coatings have been integrated into orthopaedic/dental implants in order to mimic the surrounding biological environment as well as reduce the inflammation/infection that may occur. In this review, we summarize the impact of various Ti coatings on cell behaviour both in vivo and in vitro. First, we focus on the Ti surface properties and their effects on osteogenesis and then on bacterial adhesion and viability. We conclude from the current literature that surface modification of Ti implants can be generated that offer both osteoinductive and antimicrobial properties.

Surface nanotopography-induced favorable modulation of bioactivity and osteoconductive potential of anodized 3D printed Ti-6Al-4V alloy mesh structure

The objective of the study described here is to fundamentally elucidate the biological response of 3D printed Ti-6Al-4V alloy mesh structures that were surface modified to introduce titania nanotubes with an average pore size of ∼80 nm via an electrochemical anodization process from the perspective of enhancing bioactivity. The bioactivity of the mesh structures were analyzed through immersion test in simulated body fluid, which confirmed the nucleation and growth of fine globular nanoscale apatite on the nanoporous titania-modified (anodized) mesh structure surface, and agglomerated apatite with fine flakes of apatite crystals on as-fabricated mesh structure surface, that were rich in calcium and phosphorous. The cellular activity of bioactive anodized mesh structure was explored in terms of cell–material interactions involving adhesion, proliferation, synthesis of extracellular and intracellular proteins, differentiation, and mineralization. Cells adhered with a sheet-like morphology on as-fabricated mesh structure, whereas, on anodized mesh structure, numerous filopodia-like cellular extensions interacting with nanotube pores were observed. The formation of a bioactive nanoscale apatite, cell–nanotube interactions as imaged via electron microscopy, higher expression of proteins (actin, vinculin, fibronectin, and alkaline phosphatase (ALP)), and calcium content points toward the determining role of anodized mesh structure in modulating osteoblasts functions. The unique combination of nanoporous bioactive titania and interconnected porous architecture of anodized titanium alloy mesh structure provided a multimodal roughness surface ranging from nano to micro to macroscale, which helps in attaining strong primary and secondary fixation of the implant device along with the pathway for supply of nutrients and oxygen to cells and tissue.

Laser-modified titanium surfaces enhance the osteogenic differentiation of human mesenchymal stem cells

Background

Titanium surfaces have been modified by various approaches with the aim of improving the stimulation of osseointegration. Laser beam (Yb-YAG) treatment is a controllable and flexible approach to modifying surfaces. It creates a complex surface topography with micro and nano-scaled patterns, and an oxide layer that can improve the osseointegration of implants, increasing their usefulness as bone implant materials.

Methods

Laser beam irradiation at various fluences (132, 210, or 235 J/cm²) was used to treat commercially pure titanium discs to create complex surface topographies. The titanium discs were investigated by scanning electron microscopy, X-ray diffraction, and measurement of contact angles. The surface generated at a fluence of 235 J/cm² was used in the biological assays. The behavior of mesenchymal stem cells from an umbilical cord vein was evaluated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, a mineralization assay, and an alkaline phosphatase activity assay and by carrying out a quantitative real-time polymerase chain reaction for osteogenic markers. CHO-k1 cells were also exposed to titanium discs in the MTT assay.

Results

The best titanium surface was that produced by laser beam irradiation at 235 J/cm² fluence. Cell proliferation analysis revealed that the CHO-k1 and mesenchymal stem cells behaved differently. The laser-processed titanium surface increased the proliferation of CHO-k1 cells, reduced the proliferation of mesenchymal stem cells, upregulated the expression of the osteogenic markers, and enhanced alkaline phosphatase activity.

Conclusions

The laser-treated titanium surface modulated cellular behavior depending on the cell type, and stimulated osteogenic differentiation. This evidence supports the potential use of laser-processed titanium surfaces as bone implant materials, and their use in regenerative medicine could promote better outcomes.

Bio-functionalization of grade V titanium alloy with type I human collagen for enhancing and promoting human periodontal fibroblast cell adhesion - an in-vitro study

Surface modification of medical grade V titanium alloy (Ti-6Al-4V) with biomolecules is an important and vital step for tailoring it for various biomedical applications. Present study investigates theinfluence of type I human collagen (T1HC) bio-conjugation through a three stage process. Polished grade V titanium alloy discs were functionalizedwith free OH group by means of controlled heat and alkali treatment followed by coating of 3-aminopropyltriethoxy (APTES) silane couplingagent. T1HC were bio-conjugated through 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide hydrochloride N-hydroxysuccinimide (EDCNHS)coupling reaction. At each stage, grade V titanium alloy surfaces were characterized by atomic force microscopy (AFM), scanning electronmicroscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and Xrayphotoelectron spectroscopy (XPS). FTIR and XPS studies confirms thecovalent attachment of APTES with titanium alloy surface while terminalamine groups of APTES remained free for further attachment of T1HCthrough covalent bond. Aqueous stability of bio-conjugated titanium discsat various pH and time intervals (i.e. at pH of 5.5, 6.8 and 8.0 at timeinterval of 27 and 48h) confirmed the stability of T1HC bioconjugated collagen on titanium surface. Further human periodontalfibroblast cell line (HPdlF) culture revealed enhanced adhesion on theT1HC bio-conjugated surface compared to the polystyrene and polishedgrade V titanium alloy surfaces.

Fabrication of Biocompatible Potassium Sodium Niobate Piezoelectric Ceramic as an Electroactive Implant

The discovery of piezoelectricity in natural bone has attracted extensive research in emulating biological electricity for various tissue regeneration. Here, we carried out experiments to build biocompatible potassium sodium niobate (KNN) ceramics. Then, influence substrate surface charges on bovine serum albumin (BSA) protein adsorption and cell proliferation on KNN ceramics surfaces was investigated. KNN ceramics with piezoelectric constant of ~93 pC/N and relative density of ~93% were fabricated. The adsorption of protein on the positive surfaces (Ps) and negative surfaces (Ns) of KNN ceramics with piezoelectric constant of ~93 pC/N showed greater protein adsorption capacity than that on non-polarized surfaces (NPs). Biocompatibility of KNN ceramics was verified through cell culturing and live/dead cell staining of MC3T3. The cells experiment showed enhanced cell growth on the positive surfaces (Ps) and negative surfaces (Ns) compared to non-polarized surfaces (NPs). These results revealed that KNN ceramics had great potential to be used to understand the effect of surface potential on cells processes and would benefit future research in designing piezoelectric materials for tissue regeneration.

In Vitro Biocompatibility of Si Alloyed Multi-Principal Element Carbide Coatings

In the current study, we have examined the possibility to improve the biocompatibility of the (TiZrNbTaHf)C through replacement of either Ti or Ta by Si. The coatings were deposited on Si and 316L stainless steel substrates by magnetron sputtering in an Ar+CH₄ mixed atmosphere and were examined for elemental composition, chemical bonds, surface topography, surface electrical charge and biocompatible characteristics. The net surface charge was evaluated at nano and macroscopic scale by measuring the electrical potential and work function, respectively. The biocompatible tests comprised determination of cell viability and cell attachment to the coated surface. The deposited coatings had C/(metal+Si) ratios close to unity, while a mixture of metallic carbide, free-carbon and oxidized species formed on the film surface. The coatings’ surfaces were smooth and no influence of surface roughness on electrical charge or biocompatibility was found. The biocompatible characteristics correlated well with the electrical potential/work function, suggesting a significant role of surface charge in improving biocompatibility, particularly cell attachment to coating's surface. Replacement of either Ti or Ta by Si in the (TiZrNbTaHf)C coating led to an enhanced surface electrical charge, as well as to superior biocompatible properties, with best results for the (TiZrNbSiHf)C coating.

Improved proliferation and osteogenic differentiation of human mesenchymal stem cells on a titanium biomaterial grafted with poly(sodium styrene sulphonate) and coated with a platelet-rich plasma proteins biofilm

In order to replace damaged or lost bone in the human body, it is necessary to produce ‘spare body parts’ which are dependent on the use of biomaterial and stem cells and are referred to as ‘tissue engineering’. Surface modification and stem cell interaction of orthopaedic implants offer a promising approach and are investigated here specifically to improve osseointegration of the biomaterial. Osseointegration of titanium implants used in orthopaedic surgery requires that osseo-progenitor cells attach and adhere to the surface, proliferate, then differentiate into osteoblasts and, finally, produce a mineralised matrix. The surface modification of titanium with anionic polymer combined with coating of platelet-rich plasma is provided to create a favourable environment to promote early and strong fixation of implants. The ability of progenitor cells to attach to the surface during early stages is important in the development of new tissue structures; therefore, we developed in our laboratory a strategy involving the grafting of titanium implants with a polymer of sodium styrene sulphonate (poly(sodium styrene sulphonate)) and a biofilm coating of platelet-rich plasma which enables human mesenchymal stem cell interactions. The resulting biomaterial, titanium-poly(sodium styrene sulphonate) and coating of platelet-rich plasma, Ti-poly(sodium styrene sulphonate)–platelet-rich plasma was developed in order to further improve the biomaterial. In this work, we studied and characterised the ‘in vitro’ response of human mesenchymal stem cells to titanium biomaterial grafted with poly(sodium styrene sulphonate) bioactive polymer and coated with platelet-rich plasma proteins (Ti-poly(sodium styrene sulphonate)–platelet-rich plasma). This study shows an increased cell proliferation with Ti-poly(sodium styrene sulphonate)–platelet-rich plasma compared to foetal calf serum and an enhancement of the Ti-poly(sodium styrene sulphonate)–platelet-rich plasma effects on osteoblast differentiation. The results suggest that Ti-poly(sodium styrene sulphonate)–platelet-rich plasma would be a suitable scaffold for bone tissue engineering.

The functional response of bioactive titania-modified three-dimensional Ti-6Al-4V mesh structure toward providing a favorable pathway for intercellular communication and osteoincorporation

The objective of the study is to fundamentally elucidate the biological response of 3D printed mesh structures subjected to plasma electrolytic oxidation process through the study of osteoblast functions. The cellular activity of plasma electrolytic-oxidized mesh structure was explored in terms of cell-to-cell communication involving proliferation, synthesis of extracellular and intracellular proteins, and mineralization. Upon plasma electrolytic oxidation of the mesh structure, a thin layer of bioactive titania with pore size 1-3 µm was nucleated on the surface. The combination of microporous bioactive titania and interconnected porous architecture provided the desired pathway for supply of nutrients and oxygen to cells and tissue and a favorable osteogenic microenvironment for tissue on-growth and in-growth, in relation to the unmodified mesh structure. The formation of a confluent layer as envisaged via electron microscopy and quantitative assessment of the expression level of proteins (actin, vinculin, and fibronectin) point toward the determining role of surface-modified mesh structure in modulating osteoblasts functions. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2488-2501, 2016.

Biomineralization on single crystalline rutile: the modulated growth of hydroxyapatite by fibronectin in a simulated body fluid

The aim of this study is to probe the complex interaction between surface bioactivity and protein adsorption on single crystalline rutile.

Interplay between self-assembled structure of bone morphogenetic protein-2 (BMP-2) and osteoblast functions in three-dimensional titanium alloy scaffolds: Stimulation of osteogenic activity

Three-dimensional cellular scaffolds are receiving significant attention in bone tissue engineering to treat segmental bone defects. However, there are indications of lack of significant osteoinductive ability of three-dimensional cellular scaffolds. In this regard, the objective of the study is to elucidate the interplay between bone morphogenetic protein (BMP-2) and osteoblast functions on 3D mesh structures with different porosities and pore size that were fabricated by electron beam melting. Self-assembled dendritic microstructure with interconnected cellular-type morphology of BMP-2 on 3D scaffolds stimulated osteoblast functions including adhesion, proliferation, and mineralization, with prominent effect on 2-mm mesh. Furthermore, immunofluorescence studies demonstrated higher density and viability of osteoblasts on lower porosity mesh structure (2 mm) as compared to 3- and 4-mm mesh structures. Enhanced filopodia cellular extensions with extensive cell spreading was observed on BMP-2 treated mesh structures, a behavior that is attributed to the unique self-assembled structure of BMP-2 that effectively communicates with the cells. The study underscores the potential of BMP-2 in imparting osteoinductive capability to the 3D printed scaffolds.

Potential mechanism for osseointegration of dental implants in Zucker diabetic fatty rats

Our aim was to investigate the impact of diabetes mellitus and different durations of glycaemic control on early osseointegration of dental implants, and to explore possible mechanisms by measuring the expression of integrin α5β1 and fibronectin in bone around the implant. We divided 33 male Zucker diabetic fatty (ZDF) rats aged 3 months into 3 groups. The first group comprised diabetic rats with dental implants (controls); the second group was treated with insulin and implants were placed simultaneously (exenatide alone group); and the third group was treated with insulin until the serum glucose was at a constant concentration (< 16 mmol/L), and implants were then inserted (exenatide+normal glucose group). Rats were killed 7, 14, 30, and 60 days after implants had been inserted. The expression of integrin α5β1 and fibronectin in bone around the implants was detected by immunohistochemical analysis in each group. The expression in the exenatide+normal glucose group was stronger than in the other 2 groups. Fourteen days after implantation, expression of integrin α5β1 in the exenatide alone group was significantly stronger than that in the control group (p=0.027), and 60 days after implantation the expression of fibronectin in the exenatide alone group was also significantly stronger than that among the controls (p=0.001). Both fibronectin and integrin α5β1 participate in the adhesion of osteoblasts and act as signals at the bone/implant interface. Diabetes interferes with the osseointegration of implants by deferring expression of fibronectin and integrin α5β1.

Good hydration and cell-biological performances of superparamagnetic calcium phosphate cement with concentration-dependent osteogenesis and angiogenesis induced by ferric iron

Superparamagnetic Fe³⁺-doped calcium phosphate cement (Fe-CPC) has prospective applications in bone remodeling due to its good hydration properties and significant effect on osteogenesis and angiogenesis.

Immobilization of hyaluronic acid on plasma-sprayed porous titanium coatings for improving biological properties

In the present study, hyaluronic acid (HyA) was covalently immobilized onto titanium coatings to improve their biological properties. Diffuse reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were employed to characterize the HyA-modified titanium coating. HyA-modified titanium coatings possess better cell-material interaction, and human mesenchymal stem cells present good adhesive morphologies on the surface of TC-AAH. The results of subsequent cellular evaluation showed that the immobilization of HyA on titanium coatings could improve hMSC attachment, proliferation, and differentiation. In vivo evaluation of implants in rabbit femur condyle defect model showed improvements of early osseointegration and bone-to-implant contact of TC-AAH. In conclusion, immobilization of HyA could improve biological properties of titanium coatings.

Heat and radiofrequency plasma glow discharge pretreatment of a titanium alloy: evidence [corrected] for enhanced osteoinductive properties

It is believed that orthopedic and implant longevity can be improved by optimizing fixation, or direct bone-implant contact, through the stimulation of new bone formation around the implant. The purpose of this study was to determine whether heat (600°C) or radiofrequency plasma glow discharge (RFGD) pretreatment of Ti6Al4V stimulated calcium-phosphate mineral formation in cultures of attached MC3T3 osteoprogenitor cells with or without a fibronectin coating. Calcium-phosphate mineral was analyzed by flame atomic absorption spectrophotometry, scanning electron microscopy (SEM)/electron dispersive X-ray microanalysis (EDAX) and Fourier transformed infrared spectroscopy (FTIR). RFGD and heat pretreatments produced a general pattern of increased total soluble calcium levels, although the effect of heat pretreatment was greater than that of RFGD. SEM/EDAX showed the presence of calcium-and phosphorus-containing particles on untreated and treated disks that were more numerous on fibronectin-coated disks. These particles were observed earliest (1 week) on RFGD-pretreated surfaces. FTIR analyses showed that the heat pretreatment produced a general pattern of increased levels of apatite mineral at 2-4 weeks; a greater effect was observed for fibronectin-coated disks compared to uncoated disks. The observed findings suggest that heat pretreatment of Ti6Al4V increased the total mass of the mineral formed in MC3T3 osteoprogenitor cell cultures more than RFGD while the latter pretreatment hastened the early deposition of mineral. These findings help to support the hypothesis that the pretreatments enhance the osteoinductive properties of the alloy.

Heat and radiofrequency plasma glow discharge pretreatment of a titanium alloy promote bone formation and osseointegration

Orthopedic and dental implants manifest increased failure rates when inserted into low density bone. We determined whether chemical pretreatments of a titanium alloy implant material stimulated new bone formation to increase osseointegration in vivo in trabecular bone using a rat model. Titanium alloy rods were untreated or pretreated with heat (600°C) or radiofrequency plasma glow discharge (RFGD). The rods were then coated with the extracellular matrix protein fibronectin (1 nM) or left uncoated and surgically implanted into the rat femoral medullary cavity. Animals were euthanized 3 or 6 weeks later, and femurs were removed for analysis. The number of trabeculae in contact with the implant surface, surface contact between trabeculae and the implant, and the length and area of bone attached to the implant were measured by histomorphometry. Implant shear strength was measured by a pull-out test. Both pretreatments and fibronectin enhanced the number of trabeculae bonding with the implant and trabeculae-to-implant surface contact, with greater effects of fibronectin observed with pretreated compared to untreated implants. RFGD pretreatment modestly increased implant shear strength, which was highly correlated (r(2) = 0.87-0.99) with measures of trabecular bonding for untreated and RFGD-pretreated implants. In contrast, heat pretreatment increased shear strength 3-5-fold for both uncoated and fibronectin-coated implants at 3 and 6 weeks, suggesting a more rapid increase in implant-femur bonding compared to the other groups. In summary, our findings suggest that the heat and RFGD pretreatments can promote the osseointegration of a titanium alloy implant material.

Structure-activity relationship of human bone sialoprotein peptides

In the current study, the relationship between the structure of the RGD-containing human bone sialoprotein (hBSP) peptide 278-293 and its attachment activity toward osteoblast-like (MC3T3) cells was investigated. This goal was accomplished by examining the comparative cell-attachment activities of several truncated forms of peptide 278-293. Computer modeling of the various peptides was also performed to assess the role of secondary structure in peptide bioactivity. Elimination of tyrosine-278 at the N-terminus resulted in a more dramatic loss of cell-attachment activity compared with the removal of either tyrosine-293 or the arg-ala-tyr (291-293) tripeptide. Although replacement of the RGD (arg-gly-asp) peptide moiety with peptide KAE (lys-ala-glu) resulted in a dramatic loss of cell-attachment activity, a peptide containing RGE (arg-gly-glu) in place of RGD retained 70-85% of the parental peptide's attachment activity. These results suggest that the N-terminal RGD-flanking region of hBSP peptide 278-293, in particular the tyrosine-278 residue, represents a second cell-attachment site that stabilizes the RGD-integrin receptor complex. Computer modeling also suggested that a β-turn encompassing RGD or RGE in some of the hBSP peptides may facilitate its binding to integrins by increasing the exposure of the tripeptide. This knowledge may be useful in the future design of biomimetic peptides which are more effective in promoting the attachment of osteogenic cells to implant surfaces in vivo.

Titanium dioxide nanoparticles disturb the fibronectin-mediated adhesion and spreading of pre-osteoblastic cells

In the context of rapid development of nanoparticles (NPs) for industrial applications, the question of their toxicity and biological effects must be considered. In this work, we have assessed the influence of titanium dioxide NPs on the adhesion and spreading of MC-3T3 pre-osteoblasts by using a cell subclone that does not produce its own extracellular matrix. Petri dishes were coated with the important adhesion protein fibronectin (Fn). By incubating these Fn-coated surfaces with different amounts of TiO(2) NPs, we have shown that the adhesion of pre-osteoblasts is disturbed, with an important decrease in the number of adherent cells (from 40 to 75% depending upon the concentration and type of NPs). Petri-dish surfaces were analyzed with environmental scanning electron microscropy (ESEM), with images showing that TiO(2) NP aggregates are bound to the layer of adsorbed Fn molecules. The cells cultured on these Fn/NP surfaces adopted an irregular shape and an aberrant organization of actin cytoskeleton, as revealed by fluorescence microscopy. Most importantly, these results, taken together, have revealed that the actin cytoskeleton forms abnormal aggregates, even on top of the nucleus, that coincide with the presence of large aggregates of NPs on top of cells. On the basis of these observations, we propose that some Fn molecules are able to desorb from the Petri dish surface to coat TiO(2) NPs. Fn/NP complexes are not attached firmly enough on the surface to allow for normal cell adhesion/spreading and the development of tense actin fibers. These results stress the paramount need for the assessment of the toxicology of NPs, with special attention to their interactions with biomolecules.

The osteogenic differentiation improvement of human mesenchymal stem cells on titanium grafted with polyNaSS bioactive polymer

Osseointegration of metallic implants used in orthopedic surgery requires that osteoprogenitor cells attach and adhere to the surface, then proliferate, differentiate into osteoblasts, and finally produce mineralized matrix. Because the ability of progenitor cells to attach to a scaffold surface during early stages is important in the development of new tissue structures, we developed in our laboratory, a strategy involving grafting of implants with a polymer of sodium styrene sulfonate (polyNaSS) used as a scaffold which enables human mesenchymal stem cells (hMSCs) interactions. In the present study, we investigated the cellular response of hMSCs to polyNaSS surfaces of titanium (Ti). In particular, cell proliferation, cell viability, cell differentiation, and cell spreading were evaluated. Results showed that cell proliferation and cell viability did not differ with any statistical significance between modified and unmodified Ti surfaces. Interestingly, culture of MSCs on polyNaSS surfaces resulted in a significant increase of cell spreading and cell differentiation compared with the other tested surfaces. These results suggest that titanium surface grafted with polyNaSS is a suitable scaffold for bone tissue engineering.

Effects of coating a titanium alloy with fibronectin on the expression of osteoblast gene markers in the MC3T3 osteoprogenitor cell line

PURPOSE

A number of environmental and patient-related factors contribute to implant failure. A significant fraction of these failures can be attributed to limited osseointegration resulting from poor bone healing responses. The overall goal of this study was to determine whether surface treatment of a titanium-aluminum-vanadium alloy (Ti-6Al-4V) implant material in combination with a biomimetic protein coating could promote the differentiation of attached osteoblastic cells. The specific aims of the study were to investigate whether osteoprogenitor cells cultured on a rigorously cleaned implant specimen showed a normal pattern of differentiation and whether preadsorbed fibronectin accelerated or enhanced osteoblast differentiation.

MATERIALS AND METHODS

Ti-6Al-4V disks were rigorously cleaned, passivated in nitric acid, and dry heat- sterilized; some of the disks were then coated with 1 nmol/L fibronectin. MC3T3 osteoprogenitor cells were then cultured on the pretreated disks for several weeks. Quantitative real-time polymerase chain reaction was performed to measure changes over time in the mRNA levels of osteoblast genes.

RESULTS

Fibronectin increased the peak expression of all analyzed osteoblast gene markers. "Early" genes that normally mark the proliferative phase (0 to 10 days) of osteoblastic development showed peak expression within the first 10 days after cell attachment to the titanium alloy. In contrast, "late" genes that normally mark the differentiation (10 to 20 days) and mineralization (20 to 36 days) phases of osteoblastogenesis achieved peak expression only after approximately 3 to 4 weeks of culture.

CONCLUSIONS

Osteoprogenitors cultured on a rigorously cleaned Ti-6Al-4V alloy were found to demonstrate a normal pattern of osteoblast differentiation. Preadsorbed fibronectin was observed to stimulate osteoblast differentiation during the mineralization phase of osteoblastogenesis.

PIIID-formed (Ti, O)/Ti, (Ti, N)/Ti and (Ti, O, N)/Ti coatings on NiTi shape memory alloy for medical applications

(Ti, O)/Ti, (Ti, N)/Ti and (Ti, O, N)/Ti composite coatings were fabricated on NiTi shape memory alloy via plasma immersion ion implantation and deposition (PIIID). Surface morphology of samples was investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Cross-sectional morphology indicated that the PIIID-formed coatings were dense and uniform. X-ray diffraction (XRD) was used to characterize the phase composition of samples. X-ray photoelectron spectroscopy (XPS) results showed that the surface of coated NiTi SMA samples was Ni-free. Nanoindentation measurements and pin-on-disc tests were carried out to evaluate mechanical properties and wear resistance of coated NiTi SMA, respectively. For the in vitro biological assessment of the composite coatings in terms of cell morphology and cell viability, osteoblast-like SaOS-2 cells and breast cancer MCF-7 cells were cultured on NiTi SMA samples, respectively. SaOS-2 cells attached and spread better on coated NiTi SMA. Viability of MCF-7 cells showed that the PIIID-formed composite coatings were noncytotoxic and coated samples were more biocompatible than uncoated samples.

Heat or radiofrequency plasma glow discharge treatment of a titanium alloy stimulates osteoblast gene expression in the MC3T3 osteoprogenitor cell line

Purpose

The purpose of this study was to determine whether increasing the Ti6Al4V surface oxide negative charge through heat (600℃) or radiofrequency plasma glow discharge (RFGD) pretreatment, with or without a subsequent coating with fibronectin, stimulated osteoblast gene marker expression in the MC3T3 osteoprogenitor cell line.

Methods

Quantitative real-time polymerase chain reaction was used to measure changes over time in the mRNA levels for osteoblast gene markers, including alkaline phosphatase, bone sialoprotein, collagen type I (α1), osteocalcin, osteopontin and parathyroid hormone-related peptide (PTH-rP), and the osteoblast precursor genes Runx2 and osterix.

Results

Osteoprogenitors began to differentiate earlier on disks that were pretreated with heat or RFGD. The pretreatments increased gene marker expression in the absence of a fibronectin coating. However, pretreatments increased osteoblast gene expression for fibronectin-coated disks more than uncoated disks, suggesting a surface oxide-mediated specific enhancement of fibronectin's bioactivity. Heat pretreatment had greater effects on the mRNA expression of genes for PTH-rP, alkaline phosphatase and osteocalcin while RFGD pretreatment had greater effects on osteopontin and bone sialoprotein gene expression.

Conclusions

The results suggest that heat and RFGD pretreatments of the Ti6Al4V surface oxide stimulated osteoblast differentiation through an enhancement of (a) coated fibronectin's bioactivity and (b) the bioactivities of other serum or matrix proteins. The quantitative differences in the effects of the two pretreatments on osteoblast gene marker expression may have arisen from the unique physico-chemical characteristics of each resultant oxide surface. Therefore, engineering the Ti6Al4V surface oxide to become more negatively charged can be used to accelerate osteoblast differentiation through fibronectin-dependent and independent mechanisms.

Titanium alloy surface oxide modulates the conformation of adsorbed fibronectin to enhance its binding to α(5) β(1) integrins in osteoblasts

Our laboratory has previously demonstrated that heat (600°C) or radiofrequency plasma glow discharge (RFGD) pretreatment of a titanium alloy (Ti6Al4V) increased the net negative charge of the alloy's surface oxide and the attachment of osteoblastic cells to adsorbed fibronectin. The purpose of the current study was to investigate the biological mechanism by which these surface pretreatments enhance the capacity of fibronectin to stimulate osteoblastic cell attachment. Each pretreatment was found to increase the binding (measured by ELISA) of a monoclonal anti-fibronectin Ig to the central integrin-binding domain of adsorbed fibronectin, and to increase the antibody's inhibition of osteogenic cell attachment (measured by hexosaminidase assay). Pretreatments also increased the binding (measured by ELISA) of anti-integrin IgG's to the α(5) and β(1) integrin subunits that became attached to fibronectin during cell incubation. These findings suggest that negatively charged surface oxides of Ti6Al4V cause conformational changes in fibronectin that increase the availability of its integrin-binding domain to α(5) β(1) integrins.

Adhesion of osteoblasts to a nanorough titanium implant surface

This work considers the adhesion of cells to a nanorough titanium implant surface with sharp edges. The basic assumption was that the attraction between the negatively charged titanium surface and a negatively charged osteoblast is mediated by charged proteins with a distinctive quadrupolar internal charge distribution. Similarly, cation-mediated attraction between fibronectin molecules and the titanium surface is expected to be more efficient for a high surface charge density, resulting in facilitated integrin mediated osteoblast adhesion. We suggest that osteoblasts are most strongly bound along the sharp convex edges or spikes of nanorough titanium surfaces where the magnitude of the negative surface charge density is the highest. It is therefore plausible that nanorough regions of titanium surfaces with sharp edges and spikes promote the adhesion of osteoblasts.

Surface oxide net charge of a titanium alloy: comparison between effects of treatment with heat or radiofrequency plasma glow discharge

In the current study, we have compared the effects of heat and radiofrequency plasma glow discharge (RFGD) treatment of a Ti6Al4V alloy on the physico-chemical properties of the alloy's surface oxide. Titanium alloy (Ti6Al4V) disks were passivated alone, heated to 600 °C, or RFGD plasma treated in pure oxygen. RFGD treatment did not alter the roughness, topography, elemental composition or thickness of the alloy's surface oxide layer. In contrast, heat treatment altered oxide topography by creating a pattern of oxide elevations approximately 50-100 nm in diameter. These nanostructures exhibited a three-fold increase in roughness compared to untreated surfaces when RMS roughness was calculated after applying a spatial high-pass filter with a 200 nm-cutoff wavelength. Heat treatment also produced a surface enrichment in aluminum and vanadium oxides. Both RFGD and heat treatment produced similar increases in oxide wettability. Atomic force microscopy (AFM) measurements of metal surface oxide net charge signified by a long-range force of attraction to or repulsion from a (negatively charged) silicon nitride AFM probe were also obtained for all three experimental groups. Force measurements showed that the RFGD-treated Ti6Al4V samples demonstrated a higher net positive surface charge at pH values below 6 and a higher net negative surface charge at physiological pH (pH values between 7 and 8) compared to control and heat-treated samples. These findings suggest that RFGD treatment of metallic implant materials can be used to study the role of negatively charged surface oxide functional groups in protein bioactivity, osteogenic cell behavior and osseointegration independently of oxide topography.