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

In Vitro Evaluation of Ag- and Sr-Doped Hydroxyapatite Coatings for Medical Applications

Osseointegration plays the most important role in the success of an implant. One of the applications of hydroxyapatite (HAp) is as a coating for metallic implants due to its bioactive nature, which improves osteoconduction. The purpose of this research was to assess the in vitro behavior of HAp undoped and doped with Ag and/or Sr obtained by galvanostatic pulsed electrochemical deposition. The coatings were investigated in terms of chemical bonds, contact angle and surface free energy, electrochemical behavior, in vitro biomineralization in acellular media (SBF and PBS), and biocompatibility with preosteoblasts cells (MC3T3-E1 cell line). The obtained results highlighted the beneficial impact of Ag and/or Sr on the HAp. The FTIR spectra confirmed the presence of hydroxyapatite within all coatings, while in terms of wettability, the contact angle and surface free energy investigations showed that all surfaces were hydrophilic. The in vitro behavior of MC3T3-E1 indicated that the presence of Sr in the HAp coatings as a unique doping agent or in combination with Ag elicited improved cytocompatibility in terms of cell proliferation and osteogenic differentiation. Therefore, the composite HAp-based coatings showed promising potential for bone regeneration applications.

Fabrication of porous gehlenite coating on Al2O3-ZrO2-SiC composite ceramics and its in vitro biological activities

Porous gehlenite coatings on Al₂O₃-ZrO₂-SiC composite ceramics were prepared by electro-spraying technique combined with reactive sintering method. The influences of gehlenite coating on the mechanical property of the ceramics and biological activity of the coating were investigated. The results indicated that the gehlenite coating has limited influences on flexural strength and fracture toughness of the ceramics, and the coating has elastic modulus of 82 GPa, hardness of 2.2 GPa, and adhesive strength of 1512 mN, suggesting its potential application in load-bearing ceramic implants. Simulated body fluid soaking test, CCK-8 and alkaline phosphatase activity assay demonstrated that the porous gehlenite coating has strong mineralization ability, which promotes proliferation and differentiation of MC3T3-E1 cells. These excellent biological performances can be attributed to the synergistic effect of the porous surface of the coating and its release of Ca²⁺ and Si⁴⁺.

Effect of hydroxy groups and microtopography generated by a nanosecond-pulsed laser on pure Ti surfaces

In this paper, we study a process for modifying the surface microtopography of the Ti oxide layer using a nanosecond-pulsed laser (NPL). Even now, the mechanism by which hydroxyl groups are generated on the titanium surface treated by NPL is not clear. Hence, we evaluated the surface properties of the NPL defocus distances on pure titanium surfaces, and investigated the relationship between the generation of hydroxyapatites/cell viability and the titanium surface characteristics. The NPL defocus distance was varied from 0 to 4 mm. Defocus distances of 0 and 2 mm generated microtopographical features on the titanium surface, and the resulting surfaces exhibited a greater density of OH groups than the surface treated with a defocus distance of 4 mm. The surfaces treated using defocus distances of 0 and 2 mm were found to be coated with microspherical hydroxyapatite composed of coexisting plate- and needle-like crystals after immersion in simulated body fluid, and alkaline phosphatase activity assays indicated improved cell compatibility. The improvements in biocompatibility and cell compatibility were due to the pocket-like microtopographical structures formed along the processing trace. These pockets contained a large amount of OH groups, and promoted the growth of hydroxyapatite.

Diatom-Inspired Silica Nanostructure Coatings with Controllable Microroughness Using an Engineered Mussel Protein Glue to Accelerate Bone Growth on Titanium-Based Implants

Silica nanoparticles (SiNPs) have been utilized to construct bioactive nanostructures comprising surface topographic features and bioactivity that enhances the activity of bone cells onto titanium-based implants. However, there have been no previous attempts to create microrough surfaces based on SiNP nanostructures even though microroughness is established as a characteristic that provides beneficial effects in improving the biomechanical interlocking of titanium implants. Herein, a protein-based SiNP coating is proposed as an osteopromotive surface functionalization approach to create microroughness on titanium implant surfaces. A bioengineered recombinant mussel adhesive protein fused with a silica-precipitating R5 peptide (R5-MAP) enables direct control of the microroughness of the surface through the multilayer assembly of SiNP nanostructures under mild conditions. The assembled SiNP nanostructure significantly enhances the in vitro osteogenic cellular behaviors of preosteoblasts in a roughness-dependent manner and promotes the in vivo bone tissue formation on a titanium implant within a calvarial defect site. Thus, the R5-MAP-based SiNP nanostructure assembly could be practically applied to accelerate bone-tissue growth to improve the stability and prolong the lifetime of medical implantable devices.

In vitro biological outcome of laser application for modification or processing of titanium dental implants

There are numerous functions for laser in modern implant dentistry including surface treatment, surface coating, and implant manufacturing. As laser application may potentially improve osseointegration of dental implants, we systematically reviewed the literature for in vitro biological responses to laser-modified or processed titanium dental implants. The literature was searched in PubMed, ISI Web, and Scopus, using keywords "titanium dental implants," "laser," "biocompatibility," and their synonyms. After screening the 136 references obtained, 28 articles met the inclusion criteria. We found that Nd:YAG laser was the most commonly used lasers in the treatment or processing of titanium dental implants. Most of the experiments used cell attachment and cell proliferation to investigate bioresponses of the implants. The most commonly used cells in these assays were osteoblast-like cells. Only one study was conducted in stem cells. These in vitro studies reported higher biocompatibility in laser-modified titanium implants. It seems that laser radiation plays a vital role in cell response to dental implants; however, it is necessary to accomplish more studies using different laser types and parameters on various cells to offer a more conclusive result.

Advances in the surface modification techniques of bone-related implants for last 10 years

At the time of implanting bone-related implants into human body, a variety of biological responses to the material surface occur with respect to surface chemistry and physical state. The commonly used biomaterials (e.g. titanium and its alloy, Co-Cr alloy, stainless steel, polyetheretherketone, ultra-high molecular weight polyethylene and various calcium phosphates) have many drawbacks such as lack of biocompatibility and improper mechanical properties. As surface modification is very promising technology to overcome such problems, a variety of surface modification techniques have been being investigated. This review paper covers recent advances in surface modification techniques of bone-related materials including physicochemical coating, radiation grafting, plasma surface engineering, ion beam processing and surface patterning techniques. The contents are organized with different types of techniques to applicable materials, and typical examples are also described.

Pulsed laser deposition and in vitro characteristics of triphasic – HASi composition on titanium

Pulsed laser deposition was used to deposit bioactive triphasic glass-ceramic composition (HASi) over titanium substrate using dense HASi target. Bioactive glass compositions are considered the most useful synthetic materials for immediate bone attachment because of its bioresorption, osteoconduction and osteointegration characteristics under in vivo conditions. The disadvantage of its brittleness associated with bioactive glass-ceramics has prompted its coating over metallic implants for the combination of duo mechanical and bioactive properties. The hard HASi target was able to undergo laser ablation under ambient gas pressure without bulk erosion of the target. Laser deposition was found to be efficient in depositing triphasic composition for immediate bone integration. The target and deposits were analyzed for the phase, composition and microstructural characteristics by means of X-ray diffraction, Fourier transform infrared spectroscopy, energy-dispersive X-ray analysis and scanning electron microscopy. Simultaneously, the adherent nature and mechanical behaviour of deposits were confirmed by scratch test and micro-indentation methods. Further, the in vitro dissolution and bioactivity were assessed by soaking in simulated body fluid followed by elemental analysis using inductively coupled plasma spectroscopy. The deposits were found to be cell-friendly, which was indicated by the phenomenology of stem cells under in vitro conditions.

Preparation and analysis of chemically gradient functional bioceramic coating formed by pulsed laser deposition

Bioactive ceramic coatings based on calcium phosphates yield better functionality in the human body for a variety of metallic implant devices including orthopaedic and dental prostheses. In the present study chemically and hence functionally gradient bioceramic coating was obtained by pulsed laser deposition method. Calcium phosphate bioactive ceramic coatings based on hydroxyapatite (HA) and tricalcium phosphate (TCP) were deposited over titanium substrate to produce gradation in physico-chemical characteristics and in vitro dissolution behaviour. Sintered targets of HA and α-TCP were deposited in a multi target laser deposition system. The obtained deposits were characterized by X-ray diffraction, fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray analysis. Inductively coupled plasma spectroscopy was used to estimate the in vitro dissolution behaviour of coatings. The variation in mechanical property of the gradient layer was evaluated through scratch test and micro-indentation hardness. The bioactivity was examined in vitro with respect to the ability of HA layer to form on the surface as a result of contact with simulated body fluid. It could be inferred that chemically gradient functional bioceramic coating can be produced by laser deposition of multiple sintered targets with variable chemical composition.