Multifunctional commercially pure titanium for the improvement of bone integration: Multiscale topography, wettability, corrosion resistance and biological functionalization

Current developments and future perspectives of nanotechnology in orthopedic implants: an updated review

Orthopedic implants are the most commonly used fracture fixation devices for facilitating the growth and development of incipient bone and treating bone diseases and defects. However, most orthopedic implants suffer from various drawbacks and complications, including bacterial adhesion, poor cell proliferation, and limited resistance to corrosion. One of the major drawbacks of currently available orthopedic implants is their inadequate osseointegration at the tissue-implant interface. This leads to loosening as a result of immunological rejection, wear debris formation, low mechanical fixation, and implant-related infections. Nanotechnology holds the promise to offer a wide range of innovative technologies for use in translational orthopedic research. Nanomaterials have great potential for use in orthopedic applications due to their exceptional tribological qualities, high resistance to wear and tear, ability to maintain drug release, capacity for osseointegration, and capability to regenerate tissue. Furthermore, nanostructured materials possess the ability to mimic the features and hierarchical structure of native bones. They facilitate cell proliferation, decrease the rate of infection, and prevent biofilm formation, among other diverse functions. The emergence of nanostructured polymers, metals, ceramics, and carbon materials has enabled novel approaches in orthopaedic research. This review provides a concise overview of nanotechnology-based biomaterials utilized in orthopedics, encompassing metallic and nonmetallic nanomaterials. A further overview is provided regarding the biomedical applications of nanotechnology-based biomaterials, including their application in orthopedics for drug delivery systems and bone tissue engineering to facilitate scaffold preparation, surface modification of implantable materials to improve their osteointegration properties, and treatment of musculoskeletal infections. Hence, this review article offers a contemporary overview of the current applications of nanotechnology in orthopedic implants and bone tissue engineering, as well as its prospective future applications.

Translation of nanotechnology-based implants for orthopedic applications: current barriers and future perspective

The objective of bioimplant engineering is to develop biologically compatible materials for restoring, preserving, or altering damaged tissues and/or organ functions. The variety of substances used for orthopedic implant applications has been substantially influenced by modern material technology. Therefore, nanomaterials can mimic the surface properties of normal tissues, including surface chemistry, topography, energy, and wettability. Moreover, the new characteristics of nanomaterials promote their application in sustaining the progression of many tissues. The current review establishes a basis for nanotechnology-driven biomaterials by demonstrating the fundamental design problems that influence the success or failure of an orthopedic graft, cell adhesion, proliferation, antimicrobial/antibacterial activity, and differentiation. In this context, extensive research has been conducted on the nano-functionalization of biomaterial surfaces to enhance cell adhesion, differentiation, propagation, and implant population with potent antimicrobial activity. The possible nanomaterials applications (in terms of a functional nanocoating or a nanostructured surface) may resolve a variety of issues (such as bacterial adhesion and corrosion) associated with conventional metallic or non-metallic grafts, primarily for optimizing implant procedures. Future developments in orthopedic biomaterials, such as smart biomaterials, porous structures, and 3D implants, show promise for achieving the necessary characteristics and shape of a stimuli-responsive implant. Ultimately, the major barriers to the commercialization of nanotechnology-derived biomaterials are addressed to help overcome the limitations of current orthopedic biomaterials in terms of critical fundamental factors including cost of therapy, quality, pain relief, and implant life. Despite the recent success of nanotechnology, there are significant hurdles that must be overcome before nanomedicine may be applied to orthopedics. The objective of this review was to provide a thorough examination of recent advancements, their commercialization prospects, as well as the challenges and potential perspectives associated with them. This review aims to assist healthcare providers and researchers in extracting relevant data to develop translational research within the field. In addition, it will assist the readers in comprehending the scope and gaps of nanomedicine's applicability in the orthopedics field.

Recent advances on nanomaterials for antibacterial treatment of oral diseases

An imbalance of bacteria in oral environment can lead to a variety of oral diseases, such as periodontal disease, dental caries, and peri-implant inflammation. In the long term, in view of the increasing bacterial resistance, finding suitable alternatives to traditional antibacterial methods is an important research today. With the development of nanotechnology, antibacterial agents based on nanomaterials have attracted much attention in dental field due to their low cost, stable structures, excellent antibacterial properties and broad antibacterial spectrum. Multifunctional nanomaterials can break through the limitations of single therapy and have the functions of remineralization and osteogenesis on the basis of antibacterial, which has made significant progress in the long-term prevention and treatment of oral diseases. In this review, we have summarized the applications of metal and their oxides, organic and composite nanomaterials in oral field in recent five years. These nanomaterials can not only inactivate oral bacteria, but also achieve more efficient treatment and prevention of oral diseases by improving the properties of the materials themselves, enhancing the precision of targeted delivery of drugs and imparting richer functions. Finally, future challenges and untapped potential are elaborated to demonstrate the future prospects of antibacterial nanomaterials in oral field.

Influence of Er:YAG laser irradiation on surface properties of Ti-6Al-4V machined and hydroxyapatite coated

Surface treatment by laser irradiation can change the topography of titanium; however, little is known about the changes it causes when applied to other coatings. This study aimed to evaluate the influence of Er:YAG laser irradiation on the surface properties of titanium-aluminum-vanadium (Ti-6Al-4V) discs. Four Ti-6Al-4V surfaces were evaluated (n = 10): CON-control, machined without surface treatment; LT-machined + laser treatment; HA-hydroxyapatite coating; and LT-HA-hydroxyapatite coating + laser treatment. For the laser treatment, an Er:YAG laser with a wavelength of 2940 nm, a frequency of 10 Hz, and an energy density of 12.8 J/cm2 was used. The morphology of the coating was investigated by scanning electron microscopy and the surface composition by energy-dispersive X-ray spectroscopy. The influence of laser irradiation treatment on roughness and wettability was also evaluated. The Er:YAG laser promoted a significant reduction in the roughness Sa (p < 0.05) and in the contact angle (p = 0.002) of the LT surface compared to the CON surface. On the LT-HA surface, a significant decrease in roughness was observed only for the Rz parameter (p = 0.015) and an increase in the contact angle (p < 0.001) compared to the HA surface. The use of the Er:YAG laser with the evaluated parameters decreased the surface roughness and improved the wetting capacity of machined without surface treatment. In the group with hydroxyapatite coating, the laser influenced the surface roughness only for the parameter Rz and reduced their wetting capacity.

How Streptococcus mutans Affects the Surface Topography and Electrochemical Behavior of Nanostructured Bulk Ti

The metabolization of carbohydrates by Streptococcus mutans leads to the formation of lactic acid in the oral cavity, which can consequently accelerate the degradation of dental implants fabricated from commercially available microcrystalline Ti. Microstructure influences surface topography and hence interaction between bacteria cells and Ti surfaces. This work offers the first description of the effect of S. mutans on the surface topography and properties of nanostructured bulk Ti, which is a promising candidate for modern narrow dental implants owing to its superior mechanical strength. It was found that S. mutans incubation resulted in the slight, unexpected decrease of surface nanoroughness, which was previously developed owing to privileged oxidation in areas of closely spaced boundaries. However, despite the changes in nanoscale surface topography, bacteria incubation did not reduce the high level of protection afforded by the oxide layer formed on the nanostructured Ti surface. The results highlight the need–hitherto ignored–to consider Ti microstructure when analyzing its behavior in the presence of carbohydrate-metabolizing bacteria.

Effects of rmBMP-7 on Osteoblastic Cells Grown on a Nanostructured Titanium Surface

This study evaluates the effects of the availability of exogenous BMP-7 on osteoblastic cells’ differentiation on a nanotextured Ti surface obtained by chemical etching (Nano-Ti). The MC3T3-E1 and UMR-106 osteoblastic cell lines were cultured for 5 and 7 days, respectively, on a Nano-Ti surface and on a control surface (Control-Ti) in an osteogenic medium supplemented with either 40 or 200 ng/mL recombinant mouse (rm) BMP-7. The results showed that MC3T3-E1 cells exhibited distinct responsiveness when exposed to each of the two rmBMP-7 concentrations, irrespective of the surface. Even with 40 ng/mL rmBMP-7, important osteogenic effects were noticed for Control-Ti in terms of cell proliferation potential; Runx2, Osx, Alp, Bsp, Opn, and Smad1 mRNA expression; and in situ ALP activity. For Nano-Ti, the effects were limited to higher Alp, Bsp, and Opn mRNA expression and in situ ALP activity. On both surfaces, the osteogenic potential of UMR-106 cultures remained unaltered with 40 ng/mL rmBMP-7, but it was significantly reduced when the cultures were exposed to the 200 ng/mL concentration. The availability of rmBMP-7 to pre-osteoblastic cells at the concentrations used alters the expression profile of osteoblast markers, indicative of the acquisition of a more advanced stage of osteoblastic differentiation. This occurs less pronouncedly on the nanotextured Ti and without reflecting in higher mineralized matrix production by differentiated osteoblasts on both surfaces.

Surface Characteristics and In-Vitro Studies of TiO2 Coatings by Plasma Electrolytic Oxidation in Potassium-Phosphate Electrolyte

Plasma electrolytic oxidation (PEO) was used to produce titanium oxide (TiO2) coatings on Ti surface in potassium - phosphate electrolyte. The morphology, wettability, phase, and chemical compositions were studied as a function of processing parameters. The bioactivity of the coating was assessed by the ability to form biomimetic apatite in-vitro using cell culture medium. In-vitro studies using human mesenchymal stem cells were also conducted to evaluate cells' proliferation and viability of the treated Ti. The results revealed that the produced TiO2 coatings comprised pore features with the pore size increasing with applied current density and treatment duration due to high energy discharge channels at higher potential. The PEO treated Ti exhibited superhydrophilic characteristics with a contact angle <1°. The findings indicated that the large actual surface area produced by the PEO treatment and the presence of negatively charge P O 4 3 - are the key factors for the superhydrophilic behavior. The in-vitro studies revealed that the PEO treated groups had higher amount of biomimetic apatite formation compared to the as-polished Ti. The PEO treatment significantly enhanced the cells' adhesion and growth after 24 and 72 hrs compared to the untreated Ti. A significant difference in the bioactivity was not observed between anatase and rutile.

Customized additive manufacturing of porous Ti6Al4V scaffold with micro-topological structures to regulate cell behavior in bone tissue engineering

Scaffold micro-topological structure plays an important role in the regulation of cell behavior in bone tissue engineering. This paper investigated the effect of 3D printing parameters on the scaffold micro-topological structure and its subsequent cell behaviors. By setting of different 3D printing parameters, i.e., the 3D printing laser power, the scanning interval and the thickness of sliced layers, the highest resolution up to 20 μm can be precisely fabricated. Scaffolds' characterization results indicated that the laser power affected the forming quality of melt tracks, the scanning interval distance determined the size of regularly arranged pores, and the thickness of sliced layers affected the morphological and structural characteristics. By regulating of these printing parameters, customized porous Ti6Al4V scaffold with varied hierarchical micro-topological structure can be obtained. In vitro cell culturing results showed that the regular porous micro-topological structure of scaffolds with the aperture close to cell size was more suitable for cell proliferation and adhesion. The overall distribution of cells on regular porous scaffolds was similar to the orderly arrangement of cultivated crops in the field. The findings suggested that customization of the scaffold provided an effective way to regulate cellular behavior and biological properties.

Influence of surface pre-treatment with mechanical polishing, chemical, electrochemical and ion sputter etching on the surface properties, corrosion resistance and MG-63 cell colonization of commercially pure titanium

The impact of four pre-treatment techniques on the surface morphology and chemistry, residual stress, mechanical properties, corrosion resistance in a physiological saline solution and cell colonization of commercially pure titanium is examined in detail. Mechanical polishing, electrochemical etching, chemical etching in Kroll's reagent, and ion sputter etching with argon ions were applied. Surface morphologies reflect the nature of surface layer removal. Significant roughening of the surface and a characteristic microtopology become apparent as a result of the sensitivity of chemical and ion sputter etching to the grain orientation. The hardness in the near surface region was controlled by the amount of residual stress. Etching of the stressed surface layer led to a reduction in residual stress and surface hardness. A compact passivation layer composed of TiO, TiO₂ and Ti₂O₃ native oxides imparted high corrosion resistance to the surface after mechanical polishing, chemical and electrochemical etching. The ion sputter etched surface showed substantially reduced corrosion resistance, where the corrosion process was controlled by electron transfer. The specific topology affected the adhesion of the cell to the surface rather than the cell area coverage. The cell area coverage increased with the corrosion stability of the surface.

Wettability and pre-osteoblastic behavior evaluations of a dense bovine hydroxyapatite ceramics

In this study, the wettability, cell viability, and roughness of an experimental dense bovine hydroxyapatite [Ca₁₀(PO₄)₆(OH)₂] ceramic block were evaluated so that, in the future, it could be used as a base material for dental implants. The results to commercial zirconia and a commercially pure titanium (Ti) alloy were compared. The surface roughness and contact angles were measured. An in vitro evaluation was conducted by means of tests in which pre-osteoblastic MC3T3-E1 cells were placed in indirect and direct contact with these materials. For cell viability, a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and crystal violet test were conducted. A qualitative analysis was conducted using variable pressure scanning electron microscopy (SEM). No statistically significant differences were observed in wettability and roughness tests among the groups. In both the MTT assay and crystal violet test, all groups demonstrated satisfactory results without cytotoxicity. SEM showed cell adhesion and cell proliferation results on the material surfaces after 24 h and 48 h. In conclusion, this dense Ca₁₀ (PO₄)₆(OH)₂ ceramic can be considered as a potential biocompatible material.

Surface and mechanical properties of a nanostructured citrate hydroxyapatite coating on pure titanium

The presence of a biomimetic HAP coating on titanium surface, which reduces the structural stiffness, is essential to improve implants biocompatibility and osteointegration. In this study, new citrate-HAP (cHAP) coatings were produced by a simple hydrothermal method on pure titanium (Ti) surface, without requiring any additional pretreatment on this metal surface. The formed cHAP coatings consisting of nanorod-like hydroxyapatite particles, conferred nanoroughness and wettability able to endow improved biological responses. Indeed, the presence of citrate species in the precipitate medium seems to be responsible for controlling the morphology of the new coatings. The presence of citrate groups on the surface of cHAP coatings, identified by chemical composition analysis, due to their implication in bone metabolism can additionally bring an add-value for bone implant applications. From a mechanical point of view, the Finite Element algorithm showing that cHAP coatings tend to decrease the mechanical stress at pure Ti, further favors these new coatings applicability. Overall, the simple and expedite strategy used to developed new biomimetic coatings of citrate-HAP resulted in improved physicochemical, morphological and mechanical properties of Ti, which can endeavor improved implantable materials in bone healing surgical procedures.

Nano-scale modification of titanium implant surfaces to enhance osseointegration

The main aim of this review study was to report the state of art on the nano-scale technological advancements of titanium implant surfaces to enhance the osseointegration process. Several methods of surface modification are chronologically described bridging ordinary methods (e.g. grit blasting and etching) and advanced physicochemical approaches such as 3D-laser texturing and biomimetic modification. Functionalization procedures by using proteins, peptides, and bioactive ceramics have provided an enhancement in wettability and bioactivity of implant surfaces. Furthermore, recent findings have revealed a combined beneficial effect of micro- and nano-scale modification and biomimetic functionalization of titanium surfaces. However, some technological developments of implant surfaces are not commercially available yet due to costs and a lack of clinical validation for such recent surfaces. Further in vitro and in vivo studies are required to endorse the use of enhanced biomimetic implant surfaces. STATEMENT OF SIGNIFICANCE: Grit-blasting followed by acid-etching is currently used for titanium implant modifications, although recent technological biomimetic physicochemical methods have revealed enhanced osteoconductive and anti-microbial outcomes. An improvement in wettability and bioactivity of titanium implant surfaces has been accomplished by combining micro and nano-scale modification and functionalization with protein, peptides, and bioactive compounds. Such morphological and chemical modification of the titanium surfaces induce the migration and differentiation of osteogenic cells followed by an enhancement of the mineral matrix formation that accelerate the osseointegration process. Additionally, the incorporation of bioactive molecules into the nanostructured surfaces is a promising strategy to avoid early and late implant failures induced by the biofilm accumulation.

Osteogenic activity and antibacterial ability on titanium surfaces modified with magnesium-doped titanium dioxide coating

Aim: To improve the bioactivity and antibacterial activity of titanium (Ti) implants. Materials & methods: Magnesium (Mg)-doped titanium dioxide microporous coatings (Mg-TiO₂) were prepared on the surface of Ti implants by plasma electrolytic oxidation. Results: Ti surfaces were covered with porous Mg-TiO₂, and Mg was evenly distributed throughout the coating. Mg-TiO₂ could not only promote osteoblast adhesion, proliferation and differentiation but also inhibit the colonization and growth of Staphylococcus. In addition, Mg-TiO₂ may promote osteogenesis through the ERK/c-Fos signaling pathway as well as the early osseointegration of Ti implants. Conclusion: Mg-TiO₂ has both osteogenic and antibacterial effects and thus presents important theoretical significance and clinical potential.

A New Highly Hydrophilic Electrochemical Implant Titanium Surface: A Histological and Biomechanical In Vivo Study

PURPOSE

The aim was to compare the osseointegration degree and secondary implant stability between implants with different surface treatments.

MATERIALS AND METHODS

A novel electrochemical treatment was applied to modify the sandblasted and acid-etched surface (SLA) to obtain the new hydrophilic Feeling (FEL) surface presenting a highly soluble and homogenous film made of calcium and phosphorus nanocrystals. Twenty 3.8 × 10-mm dynamix implants (Cortex) were inserted in sheep iliac crests. Sheep were killed after 2 months. Bone-to-implant contact percentage (%BIC) and biomechanical parameters, such as implant stability quotient (ISQ) and value of actual micromotion (VAM), were evaluated for each implants.

RESULTS

No implant failures were observed. Implants of test group showed %BIC value 30% higher in respect with control group (P = 0.001). No statistical differences were detected between the 2 groups in VAM and ISQ values.

CONCLUSION

Both surface treatments were highly osteoconductive because they were able to significantly increase the bone density onto implant surface in respect with that in which they were inserted (D4 bone density). The hydrophilic FEL surface demonstrated an increase of about 216% in BIC in respect with host bone density and an additional 30% more in respect with SLA surface. Faster osseointegration process is desirable in case of early implant loading protocol.

Temperature-tunable wettability on a bioinspired structured graphene surface for fog collection and unidirectional transport

We designed a type of smart bioinspired wettable surface with tip-shaped patterns by combining polydimethylsiloxane (PDMS) and graphene (PDMS/G). The laser etched porous graphene surface can produce an obvious wettability change between 200 °C and 0 °C due to a change in aperture size and chemical components. We demonstrate that the cooperation of the geometrical structure and the controllable wettability play an important role in water gathering, and surfaces with tip-shaped wettability patterns can quickly drive tiny water droplets toward more wettable regions, so making a great contribution to the improvement of water collection efficiency. In addition, due to the effective cooperation between super hydrophobic and hydrophilic regions of the special tip-shaped pattern, unidirectional water transport on the 200 °C heated PDMS/G surface can be realized. This study offers a novel insight into the design of temperature-tunable materials with interphase wettability that may enhance fog collection efficiency in engineering liquid harvesting equipment, and realize unidirectional liquid transport, which could potentially be applied to the realms of microfluidics, medical devices and condenser design.

Non-Washed Resorbable Blasting Media (NWRBM) on Titanium Surfaces could Enhance Osteogenic Properties of MSCs through Increase of miRNA-196a And VCAM1

Surface topography of Titanium (Ti) dental implants strongly influences osseointegration. In the present work, we have analyzed the influence of two Ti implant surfaces characterized by similar microtopography but different nanotopography and chemistry on the osteoblastic phenotype of Dental Pulp Stem Cells (DPSCs). The effect on osteogenic differentiation, extracellular matrix (ECM) and cell adhesion molecules production have been evaluated by means of molecular biology analyses. The morphology of the cells grown onto these surfaces has been analyzed with SEM and immunofluorescence (IF), and the safety of the surfaces has been tested by using karyotype analysis, Ames test and hemocompatibility assay. Results showed that starting from 15 days of DPSCs culture, a substantial expression of osteoblast specific markers and a strong increase of cell adhesion molecules can be detected. In particular, when DPSCs are seeded on the Ti implants expression of microRNA (miRNA)-196a, which is involved in osteoblastic commitment of stem cells, and of Vascular Cell Adhesion Molecule 1 (VCAM1), a factor involved in angiogenesis, is strongly enhanced.