Bioactive nanocomposite coatings of collagen/hydroxyapatite on titanium substrates

Calcium Orthophosphate (CaPO4) Containing Composites for Biomedical Applications: Formulations, Properties, and Applications

The goal of this review is to present a wide range of hybrid formulations and composites containing calcium orthophosphates (abbreviated as CaPO4) that are suitable for use in biomedical applications and currently on the market. The bioactive, biocompatible, and osteoconductive properties of various CaPO4-based formulations make them valuable in the rapidly developing field of biomedical research, both in vitro and in vivo. Due to the brittleness of CaPO4, it is essential to combine the desired osteologic properties of ceramic CaPO4 with those of other compounds to create novel, multifunctional bone graft biomaterials. Consequently, this analysis offers a thorough overview of the hybrid formulations and CaPO4-based composites that are currently known. To do this, a comprehensive search of the literature on the subject was carried out in all significant databases to extract pertinent papers. There have been many formulations found with different material compositions, production methods, structural and bioactive features, and in vitro and in vivo properties. When these formulations contain additional biofunctional ingredients, such as drugs, proteins, enzymes, or antibacterial agents, they offer improved biomedical applications. Moreover, a lot of these formulations allow cell loading and promote the development of smart formulations based on CaPO4. This evaluation also discusses basic problems and scientific difficulties that call for more investigation and advancements. It also indicates perspectives for the future.

Biomimetic 3D-printed PCL scaffold containing a high concentration carbonated-nanohydroxyapatite with immobilized-collagen for bone tissue engineering: enhanced bioactivity and physicomechanical characteristics

A challenging approach of three-dimensional (3D)-biomimetic scaffold design for bone tissue engineering is to improve scaffold bioactivity and mechanical properties. We aimed to design and fabricate 3D-polycaprolactone (PCL)-based nanocomposite scaffold containing a high concentration homogeneously distributed carbonated-nanohydroxyapatite (C-nHA)-particles in combination with immobilized-collagen to mimic real bone properties. PCL-scaffolds without/with C-nHA at 30%, 45%, and 60% (wt/wt) were 3D-printed. PCL/C-nHA60%-scaffolds were surface-modified by NaOH-treatment and collagen-immobilization. Physicomechanical and biological properties were investigated experimentally and by finite-element (FE) modeling. Scaffold surface-roughness enhanced by increasing C-nHA (1.7 - 6.1-fold), but decreased by surface-modification (0.6-fold). The contact angle decreased by increasing C-nHA (0.9 - 0.7-fold), and by surface-modification (0.5-fold). The zeta potential decreased by increasing C-nHA (3.2-9.9-fold). Average elastic modulus, compressive strength, and reaction force enhanced by increasing C-nHA and by surface-modification. FE modeling revealed that von Mises stress distribution became less homogeneous by increasing C-nHA, and by surface-modification. Maximal von Mises stress for 2% compression strain in all scaffolds did not exceed yield stress for bulk-material. 3D-printed PCL/C-nHA60% with surface-modification enhanced pre-osteoblast spreading, proliferation, collagen deposition, alkaline phosphatase activity, and mineralization. In conclusion, a novel biomimetic 3D-printed PCL-scaffold containing a high concentration C-nHA with surface-modification was successfully fabricated. It exhibited superior physicomechanical and biological properties, making it a promising biomaterial for bone tissue engineering.

Review of the Applications of Biomedical Compositions Containing Hydroxyapatite and Collagen Modified by Bioactive Components

Regenerative medicine is becoming a rapidly evolving technique in today's biomedical progress scenario. Scientists around the world suggest the use of naturally synthesized biomaterials to repair and heal damaged cells. Hydroxyapatite (HAp) has the potential to replace drugs in biomedical engineering and regenerative drugs. HAp is easily biodegradable, biocompatible, and correlated with macromolecules, which facilitates their incorporation into inorganic materials. This review article provides extensive knowledge on HAp and collagen-containing compositions modified with drugs, bioactive components, metals, and selected nanoparticles. Such compositions consisting of HAp and collagen modified with various additives are used in a variety of biomedical applications such as bone tissue engineering, vascular transplantation, cartilage, and other implantable biomedical devices.

Biologically Inspired Collagen/Apatite Composite Biomaterials for Potential Use in Bone Tissue Regeneration-A Review

Type I collagen and nanocrystalline-substituted hydroxyapatite are the major components of a natural composite—bone tissue. Both of these materials also play a significant role in orthopedic surgery and implantology; however, their separate uses are limited; apatite is quite fragile, while collagen’s mechanical strength is very poor. Therefore, in biomaterial engineering, a combination of collagen and hydroxyapatite is used, which provides good mechanical properties with high biocompatibility and osteoinduction. In addition, the porous structure of the composites enables their use not only as bone defect fillers, but also as a drug release system providing controlled release of drugs directly to the bone. This feature makes biomimetic collagen–apatite composites a subject of research in many scientific centers. The review focuses on summarizing studies on biological activity, tested in vitro and in vivo.

Bioceramic Layers with Antifungal Properties

The sol-gel method was used to synthesize the silver doped hydroxyapatite (Ag:HAp) gels in order to produce the antifungal composite layers. The pure Ti disks were used as the substrate for the composite layers. Important information about suspensions used to make Ag:HAp composite layers were obtained from an ultrasonic technique. The identification of the phase composition of the Ag:HAp composite layers was accomplished X-ray diffraction (XRD). The morphology and the thickness of the layers was evaluated using scanning electron microscopy (SEM). The uniform distribution of the constituent elements (Ag, Ca, P, and O) in both analyzed samples was observed. The antifungal activity of the samples against Candida albicans ATCC 10231 microbial strain were investigated immediately after their preparation and six months later. SEM and confocal laser scanning microscopy (CLSM) images showed that the composite layers at the two time intervals exhibited a strong antifungal activity against Candida albicans ATCC 10231 and completely inhibited the biofilm formation.

Collagen and Hydroxyapatite Scaffolds Activate Distinct Osteogenesis Signaling Pathways in Adult Adipose-Derived Multipotent Stromal Cells

Osteogenic cell signaling pathway disruption varies among bone diseases. This investigation was designed to identify adipose-derived multipotent stromal cell (ASC) and bone graft scaffold combinations for local, targeted restoration of gene expression and extracellular matrix (ECM) deposition. Human ASC osteogenesis on bone graft materials was quantified following culture in stromal (S), osteogenic (O), or osteogenic for 48 h followed by stromal medium (OS) to test the two-part hypothesis: (1) identical ASC isolates on distinct bone graft scaffolds demonstrate unique viability, differentiation, ECM production, and gene expression in the same culture conditions; (2) identical ASC-bone graft scaffold combinations have different cell viability, differentiation, ECM production, and gene expression when cultured in S, O, or OS medium. Three commercially available bone graft scaffold materials, type I bovine collagen (C), hydroxyapatite + β-tricalcium phosphate + type I bovine collagen (HT), and β-tricalcium phosphate + type I bovine collagen (CT) were evaluated. Passage 3 ASCs were loaded onto scaffold blocks with a spinner flask bioreactor, and constructs were cultured up to 28 days. Cell viability, gene expression (alkaline phosphatase [ALPL], osteoprotegerin [TNFRSF11B], osteocalcin [BGLAP], cannabinoid receptors type I [CNR1] and II [CNR2], receptor activator of nuclear factor kappa β ligand [TNFSF11]), as well as ECM DNA, collagen, sulfated glycosaminoglycan, and protein content were quantified. Matrix organization was evaluated with scanning electron microscopy. Effects of scaffold, medium, or culture duration on cell viability were minimal. Significantly higher initial ALPL expression decreased with time, while BGLAP expression increased in HT constructs in O medium, and the constructs had the most abundant ECM components and ultrastructural organization. There was a similar, although delayed, pattern of gene expression and greater ECM collagen with less organization in C constructs in O medium. Higher CNR1 expression in C versus higher TNFRSF11B/TNFSF11 expression in HT constructs throughout the study support stimulation of unique osteogenic signaling pathways by identical cell isolates. These results suggest that bone scaffold composition may be used to selectively target specific osteogenic cell signaling pathways in ASC constructs to stimulate ECM deposition based on therapeutic needs.

Review of Bionanocomposite Coating Films and Their Applications

The properties of a composite material depend on its constituent materials such as natural biopolymers or synthetic biodegradable polymers and inorganic or organic nanomaterials or nano-scale minerals. The significance of bio-based and synthetic polymers and their drawbacks on coating film application is currently being discussed in research papers and articles. Properties and applications vary for each novel synthetic bio-based material, and a number of such materials have been fabricated in recent years. This review provides an in-depth discussion on the properties and applications of biopolymer-based nanocomposite coating films. Recent works and articles are cited in this paper. These citations are ubiquitous in the development of novel bionanocomposites and their applications.

Calcium Orthophosphate-Containing Biocomposites and Hybrid Biomaterials for Biomedical Applications

The state-of-the-art on calcium orthophosphate (CaPO4)-containing biocomposites and hybrid biomaterials suitable for biomedical applications is presented. Since these types of biomaterials offer many significant and exciting possibilities for hard tissue regeneration, this subject belongs to a rapidly expanding area of biomedical research. Through the successful combinations of the desired properties of matrix materials with those of fillers (in such systems, CaPO4 might play either role), innovative bone graft biomaterials can be designed. Various types of CaPO4-based biocomposites and hybrid biomaterials those are either already in use or being investigated for biomedical applications are extensively discussed. Many different formulations in terms of the material constituents, fabrication technologies, structural and bioactive properties, as well as both in vitro and in vivo characteristics have been already proposed. Among the others, the nano-structurally controlled biocomposites, those containing nanodimensional compounds, biomimetically fabricated formulations with collagen, chitin and/or gelatin, as well as various functionally graded structures seem to be the most promising candidates for clinical applications. The specific advantages of using CaPO4-based biocomposites and hybrid biomaterials in the selected applications are highlighted. As the way from a laboratory to a hospital is a long one and the prospective biomedical candidates have to meet many different necessities, the critical issues and scientific challenges that require further research and development are also examined.

A novel simple one-step air jet spinning approach for deposition of poly(vinyl acetate)/hydroxyapatite composite nanofibers on Ti implants

A biocompatible coating consists of a poly(vinyl acetate)/hydroxyapatite (PVAc/HA) composite nanofiber mat was applied to NaOH-treated titanium metal by means of a novel, facile and efficient air jet spinning (AJS) approach. Results showed that HA nanoparticles (NPs) strongly embedded onto the AJS single fiber surface resulting in a strong chemical interfacial bonding between the two phases due to the difference in kinetic energies. It was proven that AJS membrane coatings can provide significant improvement in the corrosion resistance of titanium substrate. Interestingly, the biocompatibility using MC3T3-E1 osteoblast to the PVAc/HA fiber composite layer coated on Ti was significantly higher than pure titanium-substrates.

Mineralized collagen coatings formed by electrochemical deposition

Understanding and controlling the process of electrochemical deposition (ECD) of a mineralized collagen coating on metallic orthopedic implants is important for engineering highly bioactive coatings. In this work, the influence of different ECD parameters was investigated. The results showed that the mineralization degree of the coatings increased with deposition time, voltage potential and H2O2 addition, while chitosan addition led to weakening of mineralization, heavy mineralization resulted in a porous coating morphology. Furthermore, two typical coatings, dense and porous, were analyzed to investigate their microstructure and evaluated for their cytocompatibility; the dense coating showed better osteoblast adhesion and proliferation. Based on our understanding of how the different coating parameters influenced the coating, we proposed an ECD process in which the pH gradient near the cathode and the collagen isoelectric point were suggested to play crucial roles in controlling the mineralization and morphology of the coatings. The proposed ECD process may offer a guide for controlled deposition of a desired bioactive coating.

Effects of hydroxyapatite and PDGF concentrations on osteoblast growth in a nanohydroxyapatite-polylactic acid composite for guided tissue regeneration

The technique of guided tissue regeneration (GTR) has evolved over recent years in an attempt to achieve periodontal tissue regeneration by the use of a barrier membrane. However, there are significant limitations in the currently available membranes and overall outcomes may be limited. A degradable composite material was investigated as a potential GTR membrane material. Polylactic acid (PLA) and nanohydroxyapatite (nHA) composite was analysed, its bioactive potential and suitability as a carrier system for growth factors were assessed. The effect of nHA concentrations and the addition of platelet derived growth factor (PDGF) on osteoblast proliferation and differentiation was investigated. The bioactivity was dependent on the nHA concentration in the films, with more apatite deposited on films containing higher nHA content. Osteoblasts proliferated well on samples containing low nHA content and differentiated on films with higher nHA content. The composite films were able to deliver PDGF and cell proliferation increased on samples that were pre-absorbed with the growth factor. nHA-PLA composite films are able to deliver active PDGF. In addition the bioactivity and cell differentiation was higher on films containing more nHA. The use of a nHA-PLA composite material containing a high concentration of nHA may be a useful material for GTR membrane as it will not only act as a barrier, but may also be able to enhance bone regeneration by delivery of biologically active molecules.

An artificial fusion protein between bone morphogenetic protein 2 and titanium-binding peptide is functional in vivo

The purpose of this study was to investigate osteogenesis using an artificial fusion protein (AFP) composed of modified bone morphogenetic protein 2 (BMP-2) with a titanium (Ti)-binding peptide (TBP) motif on a Ti surface in vivo. In the in vivostudy, 5-μm thick Ti was coated with electron cyclotron resonance sputtering on a porous carbon scaffold which was then dipped in one of three different mixtures of collagen gel: (1) collagen gel only, (2) collagen gel with TBP, and (3) collagen gel with the AFP between BMP-2 and the TBP motif (AFP-TBP-BMP-2). These scaffolds were then implanted into rat abdominal muscles and were studied histologically at various times and the expression of several bone-related protein messenger RNAs (mRNAs) was also analyzed. The Ti-coated scaffold of the collagen gel with AFP-TBP-BMP-2 produced cartilage in the muscle and the expression of alkaline phosphatase, bone sialoprotein, and runt-related gene 2 mRNAs was significantly increased. These results suggest that the scaffold of the collagen gel with AFP-TBP-BMP-2 accelerates osteogenesis in vivo.

Electrospun hydroxyapatite-containing chitosan nanofibers crosslinked with genipin for bone tissue engineering

Reconstruction of large bone defects remains problematic in orthopedic and craniofacial clinical practice. Autografts are limited in supply and are associated with donor site morbidity while other materials show poor integration with the host's own bone. This lack of integration is often due to the absence of periosteum, the outer layer of bone that contains osteoprogenitor cells and is critical for the growth and remodeling of bone tissue. In this study we developed a one-step platform to electrospin nanofibrous scaffolds from chitosan, which also contain hydroxyapatite nanoparticles and are crosslinked with genipin. We hypothesized that the resulting composite scaffolds represent a microenvironment that emulates the physical, mineralized structure and mechanical properties of non-weight bearing bone extracellular matrix while promoting osteoblast differentiation and maturation similar to the periosteum. The ultrastructure and physicochemical properties of the scaffolds were studied using scanning electron microscopy and spectroscopic techniques. The average fiber diameters of the electrospun scaffolds were 227 ± 154 nm as spun, and increased to 335 ± 119 nm after crosslinking with genipin. Analysis by X-ray diffraction, Fourier transformed infrared spectroscopy and energy dispersive spectroscopy confirmed the presence of characteristic features of hydroxyapatite in the composite chitosan fibers. The Young's modulus of the composite fibrous scaffolds was 142 ± 13 MPa, which is similar to that of the natural periosteum. Both pure chitosan scaffolds and composite hydroxyapatite-containing chitosan scaffolds supported adhesion, proliferation and osteogenic differentiation of mouse 7F2 osteoblast-like cells. Expression and enzymatic activity of alkaline phosphatase, an early osteogenic marker, were higher in cells cultured on the composite scaffolds as compared to pure chitosan scaffolds, reaching a significant, 2.4 fold, difference by day 14 (p < 0.05). Similarly, cells cultured on hydroxyapatite-containing scaffolds had the highest rate of osteonectin mRNA expression over 2 weeks, indicating enhanced osteoinductivity of the composite scaffolds. Our results suggest that crosslinking electrospun hydroxyapatite-containing chitosan with genipin yields bio-composite scaffolds, which combine non-weight-bearing bone mechanical properties with a periosteum-like environment. Such scaffolds will facilitate the proliferation, differentiation and maturation of osteoblast-like cells. We propose that these scaffolds might be useful for the repair and regeneration of maxillofacial defects and injuries.

Electrospun nanostructured fibers of collagen-biomimetic apatite on titanium alloy

Titanium and its alloys are currently the mainly used materials to manufacture orthopaedic implants due to their excellent mechanical properties and corrosion resistance. Although these materials are bioinert, the improvement of biological properties (e.g., bone implant contact) can be obtained by the application of a material that mimics the bone extracellular matrix. To this aim, this work describes a new method to produce nanostructured collagen-apatite composites on titanium alloy substrate, by combining electrospinning and biomimetic mineralization. The characterization results showed that the obtained mineralized scaffolds have morphological, structural, and chemical compositional features similar to natural bone extracellular matrix. Finally, the topographic distribution of the chemical composition in the mineralized matrix evaluated by Fourier Transform Infrared microspectroscopy demonstrated that the apatite nanocrystals cover the collagen fibers assembled by the electrospinning.

The role of hydroxyapatite in citric acid-based nanocomposites: surface characteristics, degradation, and osteogenicity in vitro

The incorporation of nanoscale hydroxyapatite (HA) into biodegradable polymers can potentially mimic the native structure of bone and influence the mechanical properties and the extent of bioactivity. In this study nanocomposites of poly(1,8-octanediol-co-citrate) (POC) containing 40, 50, and 60 wt.% HA (POC-HA) were fabricated and characterized. Nanocomposite hydrophilicity and the degradation properties in vitro were evaluated via contact angle measurements, scanning electron microscopy (SEM), and mass loss measurements. Human mesenchymal stem cells (hMSC) were cultured on POC-HA nanocomposites in both growth and osteogenic media. Cell proliferation, alkaline phosphatase activity, and osteocalcin were measured. The equilibrium water in air contact angles confirmed all of the nanocomposites to be hydrophilic (23.4 ± 8.1°, 27 ± 9.1°, and 27.7 ± 3.5° for 40, 50, and 60 wt.% HA, respectively). Over a period of 26 weeks the degradation rate increased with decreasing HA content and pore formation was evident for POC-HA containing 40 wt.% HA, whereas POC with 50 and 60 wt.% HA lacked pores (mass loss at 26 weeks for 40, 50, and 60 wt.% HA, 27.4 ± 1.6%, 17.7 ± 1.6%, and 6.3 ± 2.6%, respectively). hMSC adhered and proliferated well on all composites, confirming biocompatibility for at least 21 days. An increase in adhesion and proliferation was found with increasing HA nanoparticle content (ng DNA at day 21 for 40, 50, and 60 wt.% HA, 130.4 ± 49.4, 184.4 ± 86.4, 314.1 ± 92.3). Alkaline phosphatase activity and osteocalcin concentration correlated with HA content (alkaline phosphate activity in expansion medium and osteogenic medium for 40, 50, and 60 wt.% HA, 256.1 ± 71.8%, 304.0 ± 128.7%, and 500.2 ± 89.9%, and 358.4 ± 124.1%, 653.7 ± 216.5%, and 814.4 ± 68.8%, respectively; osteocalcin concentration in expansion medium and osteogenic medium for 40, 50, and 60 wt.% HA, 236.9 ± 7.8%, 253.0 ± 7.5%, and 285.2 ± 11.4%, and 265.8 ± 15.0%, 288.3 ± 17.9%, and 717.3 ± 38.7%, respectively). This study provides insight into how the HA nanoparticle content can modulate the cell compatibility and physical properties of POC-HA nanocomposites.

Biocomposites and hybrid biomaterials based on calcium orthophosphates

The state-of-the-art of biocomposites and hybrid biomaterials based on calcium orthophosphates that are suitable for biomedical applications is presented in this review. Since these types of biomaterials offer many significant and exciting possibilities for hard tissue regeneration, this subject belongs to a rapidly expanding area of biomedical research. Through successful combinations of the desired properties of matrix materials with those of fillers (in such systems, calcium orthophosphates might play either role), innovative bone graft biomaterials can be designed. Various types of biocomposites and hybrid biomaterials based on calcium orthophosphates, either those already in use or being investigated for biomedical applications, are extensively discussed. Many different formulations, in terms of the material constituents, fabrication technologies, structural and bioactive properties as well as both in vitro and in vivo characteristics, have already been proposed. Among the others, the nanostructurally controlled biocomposites, those containing nanodimensional compounds, biomimetically fabricated formulations with collagen, chitin and/or gelatin as well as various functionally graded structures seem to be the most promising candidates for clinical applications. The specific advantages of using biocomposites and hybrid biomaterials based on calcium orthophosphates in the selected applications are highlighted. As the way from the laboratory to the hospital is a long one, and the prospective biomedical candidates have to meet many different necessities, this review also examines the critical issues and scientific challenges that require further research and development.

Functionalization of titanium based metallic biomaterials for implant applications

Surface immobilization with active functional molecules (AFMs) on a nano-scale is a main field in the current biomaterial research. The functionalization of a vast number of substances and molecules, ranging from inorganic calcium phosphates, peptides and proteins, has been investigated throughout recent decades. However, in vitro and in vivo results are heterogeneous. This may be attributed partially to the limits of the applied immobilization methods. Therefore, this paper highlights the advantages and limitations of the currently applied methods for the biological nano-functionalization of titanium-based biomaterial surfaces. The second part describes a newer immobilization system, using the nanomechanical fixation of at least partially single-stranded nucleic acids (NAs) into an anodic titanium oxide layer as an immobilization principle and their hybridization ability for the functionalization of the surface with active functional molecules conjugated to the respective complementary NA strands.

Comparative assessment of structural and biological properties of biomimetically coated hydroxyapatite on alumina (alpha-Al2O3) and titanium (Ti-6Al-4V) alloy substrates

Previous reports have shown the use of hydroxyapatite (HAp) and related calcium phosphate coatings on metal and nonmetal substrates for preparing tissue-engineering scaffolds, especially for osteogenic differentiation. These studies have revealed that the structural properties of coated substrates are dependent significantly on the method and conditions used for coating and also whether the substrates had been modified prior to the coating. In this article, we have done a comparative evaluation of the structural features of the HAp coatings, prepared by using simulated body fluid (SBF) at 25 degrees C for various time periods, on a nonporous metal substrate titanium-aluminium-vanadium (Ti-6Al-4V) alloy and a bioinert ceramic substrate alpha-alumina (alpha-Al(2)O(3)), with and without their prior treatment with the globular protein bovine serum albumin (BSA). Our analysis of these substrates by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) spectrometry showed significant and consistent differences in the quantitative and qualitative properties of the coatings. Interestingly, the bioactivity of these substrates in terms of supporting in vitro cell adhesion and spreading, and in vivo effects of implanted substrates, showed a predictable pattern, thus indicating that some coated substrates prepared under our conditions could be more suitable for biological/biomedical applications.

Effects of chitosan-coated pressed calcium sulfate pellets combined with recombinant human bone morphogenetic protein 2 on bone formation in femoral condyle-contained bone defects

Calcium sulfate has a rapid degradation rate and little osteoinductive capability. Chitosan-coated pressed calcium sulfate pellets combined with recombinant human bone morphogenetic protein 2 (rhBMP-2) have been developed that exhibit decreased resorption speed and increased compressive strength and osteoinduction. A rabbit femoral condyle-contained bone defect model was used to study the restoration of the defects treated with chitosan-coated pressed calcium sulfate pellets combined with rhBMP-2, chitosan-coated pressed calcium sulfate pellets, and uncoated pressed calcium sulfate pellets. No pellets were implanted in the control group. After 3 and 13 weeks, the results indicated that chitosan-coated pressed calcium sulfate pellets exhibited relatively slower resorption that closely coincides with the growth rate of new bone and enhanced osteogenesis when combined with rhBMP-2.

Biological nano-functionalization of titanium-based biomaterial surfaces: a flexible toolbox

Surface functionalization with bioactive molecules (BAMs) on a nanometre scale is a main field in current biomaterial research. The immobilization of a vast number of substances and molecules, ranging from inorganic calcium phosphate phases up to peptides and proteins, has been investigated throughout recent decades. However, in vitro and in vivo results are heterogeneous. This may be at least partially attributed to the limits of the applied immobilization methods. Therefore, this paper highlights, in the first part, advantages and limits of the currently applied methods for the biological nano-functionalization of titanium-based biomaterial surfaces. The second part describes a new immobilization system recently developed in our groups. It uses the nanomechanical fixation of at least partially single-stranded nucleic acids (NAs) into an anodic titanium oxide layer as an immobilization principle and their hybridization ability for the functionalization of the surface with BAMs conjugated to the respective complementary NA strands.

The osteogenic effect of electrosprayed nanoscale collagen/calcium phosphate coatings on titanium

For orthopedic and dental implants, the ultimate goal is to obtain a life-long secure anchoring of the implant in the native surrounding bone. To this end, nanoscale calcium phosphate (CaP) and collagen-CaP (col-CaP) composite coatings have been successfully deposited using the electrospray deposition (ESD) technique. In order to study to what extent the thickness of these coatings can be reduced without losing coating osteogenic properties, we have characterized the mechanical and biological coating properties using tape tests (ASTM D-3359) and in vitro cell culture experiments, respectively. Co-deposition of collagen significantly improved coating adhesive and cohesive strength, resulting in a remarkably high coating retention of up to 97% for coating thicknesses below 100 nm. In vitro cell culture experiments showed that electrosprayed CaP and col-CaP composite coatings enhanced osteoblast differentiation, leading to improved mineral deposition. This effect was most pronounced upon co-deposition of collagen with CaP, and these coatings displayed osteogenic effects even for a coating thickness of below 100 nm.

Biomimetic helical rosette nanotubes and nanocrystalline hydroxyapatite coatings on titanium for improving orthopedic implants

Natural bone consists of hard nanostructured hydroxyapatite (HA) in a nanostructured protein-based soft hydrogel template (ie, mostly collagen). For this reason, nanostructured HA has been an intriguing coating material on traditionally used titanium for improving orthopedic applications. In addition, helical rosette nanotubes (HRNs), newly developed materials which form through the self-assembly process of DNA base pair building blocks in body solutions, are soft nanotubes with a helical architecture that mimics natural collagen. Thus, the objective of this in vitro study was for the first time to combine the promising attributes of HRNs and nanocrystalline HA on titanium and assess osteoblast (bone-forming cell) functions. Different sizes of nanocrystalline HA were synthesized in this study through a wet chemical precipitation process following either hydrothermal treatment or sintering. Transmission electron microscopy images showed that HRNs aligned with nanocrystalline HA, which indicates a high affinity between both components. Some of the nanocrystalline HA formed dense coatings with HRNs on titanium. More importantly, results demonstrated enhanced osteoblast adhesion on the HRN/nanocrystalline HA-coated titanium compared with conventional uncoated titanium. Among all the HRN/nanocrystalline HA coatings tested, osteoblast adhesion was the greatest when HA nanometer particle size was the smallest. In this manner, this study demonstrated for the first time that biomimetic HRN/nanocrystalline HA coatings on titanium were cytocompatible for osteoblasts and, thus, should be further studied for improving orthopedic implants.