The modulation of stem cell behaviors by functionalized nanoceramic coatings on Ti-based implants

3D Printed Pedicle Screws with Microarc Oxidation Ceramic Interfaces Enhance Osteointegration and Orthopedic Fixation Feasibility

Effective osteointegration is of great importance for pedicle screws in spinal fusion surgeries. However, the lack of osteoinductive activity of current screws diminishes their feasibility for osteointegration and fixation, making screw loosening a common complication worldwide. In this study, Ti-6Al-4V pedicle screws with full through-hole design were fabricated via selective laser melting (SLM) 3D printing and then deposited with porous oxide coatings by microarc oxidation (MAO). The porous surface morphology of the oxide coating and the release of bioactive ions could effectively support cell adhesion, migration, vascularization, and osteogenesis in vitro. Furthermore, an in vivo goat model demonstrated the efficacy of modified screws in improving bone maturation and osseointegration, thus providing a promising method for feasible orthopedic internal fixation.

Fabrication and Characterization of Porous Diopside/Akermanite Ceramics with Prospective Tissue Engineering Applications

Tissue engineering requires new materials that can be used to replace damaged bone parts. Since hydroxyapatite, currently widely used, has low mechanical resistance, silicate ceramics can represent an alternative. The aim of this study was to obtain porous ceramics based on diopside (CaMgSi2O6) and akermanite (Ca2MgSi2O7) obtained at low sintering temperatures. The powder synthesized by the sol-gel method was pressed in the presence of a porogenic agent represented by commercial sucrose in order to create the desired porosity. The ceramic bodies obtained after sintering thermal treatment at 1050 °C and 1250 °C, respectively, were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) to determine the chemical composition. The open porosity was situated between 32.5 and 34.6%, and the compressive strength had a maximum value of 11.4 MPa for the samples sintered at 1250 °C in the presence of a 20% wt porogenic agent. A cell viability above 70% and the rapid development of an apatitic phase layer make these materials good candidates for use in hard tissue engineering.

Titanium Surface-Grafted Zwitterionic Polymers with an Anti-Polyelectrolyte Effect Enhances Osteogenesis

Zwitterionic polymers have attracted considerable attention because of their anti-adsorption and unique anti-polyelectrolyte effects and was widely used in surface modification. In this study, zwitterionic copolymers (poly (sulfobetaine methacrylate-co-butyl acrylate) (pSB) coating on the surface of a hydroxylated titanium sheet using surface-initiated atom transfer radical polymerization (SI-ATRP) was successfully constructed. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and Water contact angle (WCA) analysis proved the successful preparation of the coating. The swelling effect caused by the anti-polyelectrolyte effect was reflected in the simulation experiment in vitro, and this coating can promote the proliferation and osteogenesis of MC3T3-E1. Therefore, this study provides a new strategy for designing multifunctional biomaterials for implant surface modifications.

Electrospun fibers coated with nanostructured biomimetic hydroxyapatite: A new platform for regeneration at the bone interfaces

Reconstruction of gradient organic/inorganic tissues is a challenging task in orthopaedics. Indeed, to mimic tissue characteristics and stimulate bone regeneration at the interface, it is necessary to reproduce both the mineral and organic components of the tissue ECM, as well as the micro/nano-fibrous morphology. To address this goal, we propose here novel biomimetic patches obtained by the combination of electrospinning and nanostructured bone apatite. In particular, we deposited apatite on the electrospun fibers by Ionized Jet Deposition, a plasma-assisted technique that allows conformal deposition and the preservation in the coating of the target's stoichiometry. The damage to the substrate and fibrous morphology is a polymer-dependent aspect, that can be avoided by properly selecting the substrate composition and deposition parameters. In fact, all the tested polymers (poly(l-lactide), poly(D,l-lactide-co-glycolide, poly(ε-caprolactone), collagen) were effectively coated, and the morphological and thermal characterization revealed that poly(ε-caprolactone) suffered the least damage. The coating of collagen fibers, on the other hand, destroyed the fiber morphology and it could only be performed when collagen is blended with a more resistant synthetic polymer in the nanofibers. Due to the biomimetic composition and multiscale morphology from micro to nano, the poly(ε-caprolactone)-collagen biomimetic patches coated with bone apatite supported MSCs adhesion, patch colonization and early differentiation, while allowing optimal viability. The biomimetic coating allowed better scaffold colonization, promoting cell spreading on the fibers.

Recent Developments in Coatings for Orthopedic Metallic Implants

Titanium, stainless steel, and CoCrMo alloys are the most widely used biomaterials for orthopedic applications. The most common causes of orthopedic implant failure after implantation are infections, inflammatory response, least corrosion resistance, mismatch in elastic modulus, stress shielding, and excessive wear. To address the problems associated with implant materials, different modifications related to design, materials, and surface have been developed. Among the different methods, coating is an effective method to improve the performance of implant materials. In this article, a comprehensive review of recent studies has been carried out to summarize the impact of coating materials on metallic implants. The antibacterial characteristics, biodegradability, biocompatibility, corrosion behavior, and mechanical properties for performance evaluation are briefly summarized. Different effective coating techniques, coating materials, and additives have been summarized. The results are useful to produce the coating with optimized properties.

Nanostructure and biomimetics orchestrate mesenchymal stromal cell differentiation: An in vitro bioactivity study on new coatings for orthopedic applications

The choice of the appropriate material having suitable compositional and morphological surface characteristics, is a crucial step in the development of orthopedic implants. The purpose of this paper is to elucidate, on this regard, the influence of two important hits, i.e., biogenic apatite with bone-like composition and nanostructured morphology, providing the evidence of the efficacy of nanostructured biogenic apatite coatings in favoring adhesion, growth, proliferation, and in vitro osteogenic differentiation of human mesenchymal stromal cells (hMSCs) isolated from the bone marrow. The specific features of this coating in terms of topographical and biochemical cues, obtained by Ionized Jet Deposition, are perceived by hMSCs, as suggested by changes in different morphologic parameters as Aspect Ratio or Elongation index, suggesting the impact exerted by the nanostructure on early adhesion events, cytoskeleton organization, and cells fate. In addition, the nanostructured CaP coating sustained the metabolic activity of the cells and facilitated the osteogenic differentiation of MSC by supporting the osteogenesis-related gene expression. These findings support the use of a combined approach between technological advancement and instructive surfaces, both from the topographical and the biochemical point of view, in order to manufacture smart biomaterials able to respond to different needs of the orthopedic practice.

Nanointeraction: The profound influence of nanostructured and nano-drug delivery biomedical implant surfaces on cell behavior

Nanostructured surfaces feature promising biological properties on biomaterials attracting large interest at basic research, implant industry development, and bioengineering applications. Thou, nanoscale interactions at a molecular and cellular level are not yet completely understood and its biological and clinical implications need to be further elucidated. As follows, the aim of this comprehensive review was to evaluate nanostructured surfaces at biomedical implants focusing on surface development, nanostructuration, and nanoengineered drug delivery systems that can induce specific cell interactions in all relevant aspects of biological, reparative, anti-bacterial, anti-inflammatory and clinical processes. The methods and the physio-chemical properties involved in nanotopography performance, the main cellular characteristics involved at surface/cell interaction, and a summary of results and outlooks reported in studies applying nanostructured surfaces and nano-drug delivery systems is presented. The future prospects and commercial translation of this developing field, particularly concerning multifunctional nanostructured surfaces and its clinical implications are further discussed. At a cellular level, nanostructured biomedical implant surfaces can enhance osteogenesis by targeting osteoblasts, osteocytes, and mesenchymal cells, stimulate fibroblast/epithelial cells proliferation and adherence, inhibit bacterial cell proliferation and biofilm accumulation, and act as immune-modulating surfaces targeting macrophages and reducing pro-inflammatory cytokine expression. Moreover, several methodological options to create drug-delivery systems on metallic implant surfaces are available, however, the clinical translation is yet incomplete. The efficiency of which nanostructured/nano-delivery surfaces may target specific cell interactions and favor clinical outcomes needs to be further elucidated in pre-clinical and clinical studies, along with engineering solutions for commercial translation and approval of controlling agencies.

Gingival Response to Dental Implant: Comparison Study on the Effects of New Nanopored Laser-Treated vs. Traditional Healing Abutments

The health of peri-implant soft tissues is important for the long-term success rate of dental implants and the surface topography is pivotal in influencing it. Thus, the aim of this study was to evaluate, in human patients, the inflammatory mucosal microenvironment in the tissue surrounding a new, nanoscale, laser-treated healing abutment characterized by engineered nanopores versus a standard machined-surface. Analyses of anti- and pro-inflammatory markers, cytokeratins, desmosomal proteins and scanning electron microscopy were performed in 30 soft-tissue biopsies retrieved during second-stage surgery. The results demonstrate that the soft tissue surrounding the laser-treated surface was characterized by a lower grade of inflammation than the one facing the machined-surface, which, in turn, showed a disrupted epithelium and altered desmosomes. Moreover, higher adhesion of the epithelial cells on the laser-treated surface was detected compared to the machined one. In conclusion, the laser-treated surface topography seems to play an important role not only in cell adhesion, but also on the inflammatory makers’ expression of the soft tissue microenvironment. Thus, from a clinical point of view, the use of this kind of topography may be of crucial importance not only on healing abutments but also on prosthetic ones.

Effect of Sintering Temperature of Bioactive Glass Nanoceramics on the Hemolytic Activity and Oxidative Stress Biomarkers in Erythrocytes

INTRODUCTION

The nature of the surface is critical in determining the biological activity of silica powders. A novel correlation between toxicity and surface properties of bioactive glass ceramics (BGCs) synthesized via the sol-gel method was attempted in this study.

METHODS

The behavior of BGCs after their attachment to the surface of red blood cells (RBCs) was evaluated and their toxic effects were determined based on hemolysis, membrane injury via anti-phosphotyrosine immunoblot of Band 3, lipid peroxidation, potential to generate reactive oxygen species, and antioxidant enzyme production. In particular, three BGCs were synthesized and treated at three sintering temperatures (T1 = 835 °C, T2 = 1000 °C and T3 = 1100 °C) to investigate possible relation between surface charge or structure and hemolytic potential.

RESULTS

Their toxicity based on hemolysis was dose dependent, while BGC-T2 had the best hemocompatibility in compare with the other BGCs.No BGCs in dosages lower than 0.125 mg/mL could damage erythrocytes. On the other hand, all BGCs promoted the production of reactive oxygen species in certain concentrations, with the BGC-T2 producing the lowest ROS and increasing the glutathione levels in RBCs protecting their damage.

CONCLUSIONS

The results suggest that various factors such as size, a probable different proportion of surface silanols, a balanced mechanism between calcium and magnesium cellular uptake or the different crystalline nature may have contributed to this finding; however, future research is needed to clarify the underlying mechanisms.

In-vivo performance of plasma-sprayed CaO-MgO-SiO2-based bioactive glass-ceramic coating on Ti-6Al-4V alloy for bone regeneration

The CaO-MgO-SiO₂-based bioactive glass-ceramic coating (named M2) on Ti-6Al-4V alloy has been proven to behave well in vitro. But how to make full sense of its performances in terms of osteogenesis and osseointegration in vivo matters very much. For this, the M2-coated Ti-6Al-4V cylinders were prepared by atmospheric plasma spraying (APS) and implanted into New Zealand rabbit for 1, 2 and 3 months, respectively, by setting commercial HA-coated Ti-6Al-4V as the control. It is encouraging that, the two groups bonded with the surrounding tissues stably and newly formed bone grew towards or around the implants after 3-month implantation according to radiographic images. From the histological sections, it is obvious that, compared to the control, the M2-coated implant was more favorable for the osteogenesis and neo-vascularisation in the whole experimental process and demonstrated a better osseointegration with the host bone, indicating the former possessed better osteoconductivity, osteoinductivity and osteogenic ability. The study indicated that the M2-coated Ti-6Al-4V implant exerted a great potential to substitute the commercial HA-coated Ti-6Al-4V implant in repairing load-bearing bone defects.

Electrochemically grown functionalized -Multi-walled carbon nanotubes/hydroxyapatite hybrids on surgical grade 316L SS with enhanced corrosion resistance and bioactivity

Coatings using functionalized multi-walled carbon nanotubes (f-MWCNTs)/hydroxyapatite (HAP) on 316 L Stainless Steel by electrodeposition at the parameter of "-1.5 V" for 30 min. with three electrode set-up configuration and optimization of various concentrations of f-MWCNTs from 1 to 5% were done to improve the coating characteristics for future biomedical applications. The obtained coatings were characterized by Fourier Transformed-Infra Red spectroscopy (FT-IR) and X-ray diffractometer (XRD) to reveal the phase formation in the composites. With various additions of f-MWCNTs, the HAP phase was found to be retained. The growth of HAP on f-MWCNTs was analyzed by High-resolution Transmission Electron Microscope (HR-TEM) and the morphology of composite was found to be of the needle and flower-like particles. To understand the corrosion resistance effect of the developed HAP/f-MWCNTs composite in SBF, electrochemical investigations were carried out using Impedance and Tafel polarization analysis. From the results, it was observed that the coatings have enhanced corrosion resistance behavior and bioactivity. In addition, the Vickers Hardness study proved that the prepared HAP/fMWCNTs composite coating was found to have improved hardness value of (H_v) 390.2 ± 8.0. Thus, the electrodeposited composite coating on 316 L SS substrate can be effectively deployed for biomedical applications.

Effect of employing ultrasonic waves during pulse electrochemical deposition on the characteristics and biocompatibility of calcium phosphate coatings

In the present work, we investigated the effect of employing ultrasonic waves during pulse electrochemical deposition on surface topography, chemical composition and biocompatibility of calcium phosphate (Ca-P) coatings. The SEM and 3D AFM images showed that the anodized titanium surface was covered with the uniform and refined size of plate-like Ca-P crystals, when the ultrasonic treatment of the electrolyte with power of 60 W was carried out during deposition. In contrast, for the Ca-P; 0 W coating applied under only the magnetic stirring of the electrolyte, the microstructure was non-uniform and some Ca-P crystals with the larger size were randomly observed in different regions, causing a rougher surface. The FTIR results also revealed that employing the ultrasound increases the deposition of a coating involved in only the most stable Ca-P phase of carbonated hydroxyapatite (CHA). However, in the absence of ultrasound, besides the prominent phase of CHA, some less stable Ca-P phases like octa calcium phosphate (OCP) and brushite were also formed in the Ca-P; 0 W coating. The Ca-P; 60 W coating showed the higher ability for apatite biomineralization after a 7-day immersion in the simulated body fluid (SBF). This coating also provided a better surface for the cellular activity, as compared to the Ca-P; 0 W coating.

Nano Ag/ZnO-Incorporated Hydroxyapatite Composite Coatings: Highly Effective Infection Prevention and Excellent Osteointegration

Interfacial characteristics play an important role in infection prevention and osteointegration of artificial bone implants. In this work, both Ag nanoparticles (AgNPs) and ZnO NPs are incorporated into hydroxyapatite (HA) nanopowders and deposited onto Ti6Al4V (Ti6) implants by laser cladding. The composite coatings possess a hierarchical surface structure with homogeneous distributions of Ag and ZnO. The Ag and ZnO NPs that are immobilized by laser cladding ensure long-term and gradual release of Ag and Zn ions at low cumulative concentrations of 36.2 and 56.4 μg/L after immersion for 21 days. A large concentration of Ag released initially increases the cytotoxicity but the large initial ZnO content enhances the cell viability and osteogenetic ability. The nano Ag/ZnO-embedded HA coating (Ag/ZnO/HA = 7:3:90 wt %, namely Ag7ZnO3HA) exhibits optimal antibacterial efficacy and osteogenetic capability, as exemplified by the broad spectrum antibacterial efficacy of 96.5 and 85.8% against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), respectively, together with enhanced osteoinductivity with higher alkaline phosphatase (ALP) activity of 134.60 U/g protein compared to 70.79 U/g protein for the untreated implants after culturing for 7 days. The rabbit femoral implant model further confirms that the optimized composite coating accelerates the formation of new bone tissues indicating 87.15% of the newly formed bone area and osteointegration showing 83.75% of the bone-implant contact area even in the presence of injected S. aureus. The laser-cladded Ag7ZnO3HA composite coatings are promising metallic implants with excellent intrinsic antibacterial activity and osteointegration ability.