Functionalized coatings by cold spray: An in vitro study of micro- and nanocrystalline hydroxyapatite compared to porous titanium

Surface Functionalization of Titanium-Based Implants with a Nanohydroxyapatite Layer and Its Impact on Osteoblasts: A Systematic Review

This study aims to evaluate the influence of a nanohydroxyapatite layer applied to the surface of titanium or titanium alloy implants on the intricate process of osseointegration and its effect on osteoblast cell lines, compared to uncoated implants. Additionally, the investigation scrutinizes various modifications of the coating and their consequential effects on bone and cell line biocompatibility. On the specific date of November 2023, an exhaustive electronic search was conducted in esteemed databases such as PubMed, Web of Science, and Scopus, utilizing the meticulously chosen keywords ((titanium) AND ((osteoblasts) and hydroxyapatite)). Methodologically, the systematic review meticulously adhered to the PRISMA protocol. Initially, a total of 1739 studies underwent scrutiny, with the elimination of 741 duplicate records. A further 972 articles were excluded on account of their incongruence with the predefined subjects. The ultimate compilation embraced 26 studies, with a predominant focus on the effects of nanohydroxyapatite coating in isolation. However, a subset of nine papers delved into the nuanced realm of its modifiers, encompassing materials such as chitosan, collagen, silver particles, or gelatine. Across many of the selected studies, the application of nanohydroxyapatite coating exhibited a proclivity to enhance the osseointegration process. The modifications thereof showcased a positive influence on cell lines, manifesting in increased cellular spread or the attenuation of bacterial activity. In clinical applications, this augmentation potentially translates into heightened implant stability, thereby amplifying the overall procedural success rate. This, in turn, renders nanohydroxyapatite-coated implants a viable and potentially advantageous option in clinical scenarios where non-modified implants may not suffice.

Advanced Functional Metal-Ceramic and Ceramic Coatings Deposited by Low-Pressure Cold Spraying: A Review

Based on the recent analysis of various databases, cold spray (CS), the newest method among thermal spraying technologies, has received the unabated attention of hundreds of researchers continuously since its invention in the 1980s. The significance of CS lies in the low process temperature, which usually ensures compressive residual stresses and allows for the formation of coatings on a thermally sensitive substrate. This paper concerns the low-pressure cold spray (LPCS) variant employed for forming metal matrix composites (MMCs) with high ceramic contents and all-ceramic coatings. At the very beginning, the influence of LPCS process parameters on deposition efficiency (DE) is analysed. In the next part, the most useful feedstock powder preparation techniques for LCPS are presented. Due to the combination of bottom-up powder production methods (e.g., sol-gel (SG)) with LCPS, the metal matrix that works as a binder for ceramic particles in MMC coatings can be removed, resulting in all-ceramic coatings. Furthermore, with optimization of spraying parameters, it is possible to predict and control phase transformation in the feedstock material. Further in the paper, differences in the bonding mechanism of metal–ceramic mixtures and ceramic particles are presented. The properties and applications of various MMC and ceramic coatings are also discussed. Finally, the exemplary direction of CS development is suggested.

Characterization and evaluation of a femtosecond laser-induced osseointegration and an anti-inflammatory structure generated on a titanium alloy

Cell–material interactions during early osseointegration of the bone–implant interface are critical and involve crosstalk between osteoblasts and osteoclasts. The surface properties of titanium implants also play a critical role in cell–material interactions. In this study, femtosecond laser treatment and sandblasting were used to alter the surface morphology, roughness and wettability of a titanium alloy. Osteoblasts and osteoclasts were then cultured on the resulting titanium alloy disks. Four disk groups were tested: a polished titanium alloy (pTi) control; a hydrophilic micro-dislocation titanium alloy (sandblasted Ti (STi)); a hydrophobic nano-mastoid Ti alloy (femtosecond laser-treated Ti (FTi)); and a hydrophilic hierarchical hybrid micro-/nanostructured Ti alloy [femtosecond laser-treated and sandblasted Ti (FSTi)]. The titanium surface treated by the femtosecond laser and sandblasting showed higher biomineralization activity and lower cytotoxicity in simulated body fluid and lactate dehydrogenase assays. Compared to the control surface, the multifunctional titanium surface induced a better cellular response in terms of proliferation, differentiation, mineralization and collagen secretion. Further investigation of macrophage polarization revealed that increased anti-inflammatory factor secretion and decreased proinflammatory factor secretion occurred in the early response of macrophages. Based on the above results, the synergistic effect of the surface properties produced an excellent cellular response at the bone–implant interface, which was mainly reflected by the promotion of early ossteointegration and macrophage polarization.

Electrospinning Nanofiber-Reinforced Aerogels for the Treatment of Bone Defects

Objective: Application of aerogels in bone tissue engineering is an emerging field, while the reports of electrospinning nanofiber-reinforced aerogels are limited. This research aimed at fabricating the nanofiber-reinforced aerogels and evaluating their physiochemical and biological properties. Approach: The chitosan (CS) aerogels incorporated with cellulose acetate (CA) and poly (ɛ-caprolactone) (PCL) nanofibers were fabricated via ball milling and freeze-drying techniques. Scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectrum, X-ray photoelectron spectroscopy (XPS), compressive experiment, and in vitro experiment were conducted to assess their physiochemical properties and biological behavior. Results: The SEM examination showed that satisfying morphology was attained in the CA/PCL/CS aerogels with incorporation of CA/PCL nanofibers and CS solution. The results of FT-IR and XPS indicated the perfect incorporation of CA, PCL, and CS. A compressive experiment confirmed that the CA/PCL/CS aerogels enhanced the compressive modulus of the pure CS aerogel. For in vitro experiment, the CA/PCL/CS composite scaffolds were proven to possess better cytocompatibility compared with the pure CS. Also, cells on the CA/PCL/CS showed well-extended morphology and could infiltrate into a porous scaffold. Furthermore, confocal experiment revealed that the CA/PCL/CS could also promote the osteogenic differentiation of MC3T3-E1 cells. Innovation: This study fabricated the nanofiber-reinforced aerogels mainly to optimize the cell/material interaction of the pure CS scaffold. Conclusion: The CA/PCL nanofibers not only improved the mechanical property of the CS aerogel to some extent but also facilitated cell adhesion and osteogenic differentiation. Thus, it could be considered a promising candidate for bone tissue engineering.

Novel porous Ti35Zr28Nb scaffolds fabricated by powder metallurgy with excellent osteointegration ability for bone-tissue engineering applications

Titanium (Ti) based porous alloys have been widely used as orthopedic implants. However, the successful applications of these porous Ti alloys need to have the ability to mimic the mechanical properties of natural bone. Novel porous Ti35Zr28Nb scaffolds were fabricated via powder metallurgy (PM), and the fabricated scaffold with 61.1% porosity exhibited favorable mechanical properties with a compression yield strength of 132.5 ± 3.5 MPa and an elastic modulus of 2.9 ± 0.4 GPa, which are desired mechanical properties for bone implant material applications. The extracts of the porous Ti35Zr28Nb scaffolds showed no toxic effect on cell proliferation in vitro and their cytotoxicity grade was at level 0, similar to that of as-cast pure Ti and Ti-6Al-4 V alloy. Additionally, the extracellular alkaline phosphatase (ALP) level of MC3T3-E1 indicated that the bone matrix synthesis on the porous Ti35Zr28Nb scaffolds was slightly higher than that of as-cast Ti-6Al-4 V and pure Ti alloys. After implantation in rat distal femurs for 8 weeks, the porous Ti35Zr28Nb scaffolds were surrounded by new bone tissue, and the numbers of red blood cells, white blood cells, immunocyte cells, and neutrophil cells returned to the normal levels, which indicate that the porous Ti35Zr28Nb scaffolds possess good in vivo osteointegration ability and hemocompatibility. It hence can be concluded that the PM-fabricated Ti35Zr28Nb scaffolds, which have desired mechanical properties and excellent biocompatibility and osteointegration, are a promising candidate alloy for bone-tissue engineering applications in orthopedics.

In vitro and in vivo evaluations of mechanical properties, biocompatibility and osteogenic ability of sintered porous titanium alloy implant

A new sintering technique using Ti6Al4V powder suspension was performed to prepare porous Ti6Al4V alloys. The porous alloys could be fabricated with different porosities and pore sizes by controlling the quantity and size of spacer particles added to the Ti6Al4V powder. The characteristics and biological properties of the porous Ti6Al4V with two different porosities were evaluated by mechanical tests, cell tests and implantation. Dense Ti6Al4V was used as the control. Compared with the control group, the porous Ti6Al4V showed good biocompatibility and osteogenic ability, which makes this type of porous alloy a good prospective material for biomedical application. And compared with 50% porosity, the alloy with 75% porosity had the optimal mechanical properties, and suitable pore size and porosity, which allowed more bone ingrowth.