Titanium dioxide nanotubes of defined diameter enhance mesenchymal stem cell proliferation via JNK- and ERK-dependent up-regulation of fibroblast growth factor-2 by T lymphocytes

The Delivery and Activation of Growth Factors Using Nanomaterials for Bone Repair

Bone regeneration is a comprehensive process that involves different stages, and various growth factors (GFs) play crucial roles in the entire process. GFs are currently widely used in clinical settings to promote bone repair; however, the direct application of GFs is often limited by their fast degradation and short local residual time. Additionally, GFs are expensive, and their use may carry risks of ectopic osteogenesis and potential tumor formation. Nanomaterials have recently shown great promise in delivering GFs for bone regeneration, as they can protect fragile GFs and control their release. Moreover, functional nanomaterials can directly activate endogenous GFs, modulating the regeneration process. This review provides a summary of the latest advances in using nanomaterials to deliver exogenous GFs and activate endogenous GFs to promote bone regeneration. We also discuss the potential for synergistic applications of nanomaterials and GFs in bone regeneration, along with the challenges and future directions that need to be addressed.

Topography-mediated immunomodulation in osseointegration; Ally or Enemy

Osteoimmunology is at full display during endosseous implant osseointegration. Bone formation, maintenance and resorption at the implant surface is a result of bidirectional and dynamic reciprocal communication between the bone and immune cells that extends beyond the well-defined osteoblast-osteoclast signaling. Implant surface topography informs adherent progenitor and immune cell function and their cross-talk to modulate the process of bone accrual. Integrating titanium surface engineering with the principles of immunology is utilized to harness the power of immune system to improve osseointegration in healthy and diseased microenvironments. This review summarizes current information regarding immune cell-titanium implant surface interactions and places these events in the context of surface-mediated immunomodulation and bone regeneration. A mechanistic approach is directed in demonstrating the central role of osteoimmunology in the process of osseointegration and exploring how regulation of immune cell function at the implant-bone interface may be used in future control of clinical therapies. The process of peri-implant bone loss is also informed by immunomodulation at the implant surface. How surface topography is exploited to prevent osteoclastogenesis is considered herein with respect to peri-implant inflammation, osteoclastic precursor-surface interactions, and the upstream/downstream effects of surface topography on immune and progenitor cell function.

Delivering Mechanical Stimulation to Cells: State of the Art in Materials and Devices Design

Biochemical signals, such as growth factors, cytokines, and transcription factors are known to play a crucial role in regulating a variety of cellular activities as well as maintaining the normal function of different tissues and organs. If the biochemical signals are assumed to be one side of the coin, the other side comprises biophysical cues. There is growing evidence showing that biophysical signals, and in particular mechanical cues, also play an important role in different stages of human life ranging from morphogenesis during embryonic development to maturation and maintenance of tissue and organ function throughout life. In order to investigate how mechanical signals influence cell and tissue function, tremendous efforts have been devoted to fabricating various materials and devices for delivering mechanical stimuli to cells and tissues. Here, an overview of the current state of the art in the design and development of such materials and devices is provided, with a focus on their design principles, and challenges and perspectives for future research directions are highlighted.

Nanostructured Titanium Implant Surface Facilitating Osseointegration from Protein Adsorption to Osteogenesis: The Example of TiO2 NTAs

Titanium implants have been widely applied in dentistry and orthopedics due to their biocompatibility and resistance to mechanical fatigue. TiO₂ nanotube arrays (TiO₂ NTAs) on titanium implant surfaces have exhibited excellent biocompatibility, bioactivity, and adjustability, which can significantly promote osseointegration and participate in its entire path. In this review, to give a comprehensive understanding of the osseointegration process, four stages have been divided according to pivotal biological processes, including protein adsorption, inflammatory cell adhesion/inflammatory response, additional relevant cell adhesion and angiogenesis/osteogenesis. The impact of TiO₂ NTAs on osseointegration is clarified in detail from the four stages. The nanotubular layer can manipulate the quantity, the species and the conformation of adsorbed protein. For inflammatory cells adhesion and inflammatory response, TiO₂ NTAs improve macrophage adhesion on the surface and induce M2-polarization. TiO₂ NTAs also facilitate the repairment-related cells adhesion and filopodia formation for additional relevant cells adhesion. In the angiogenesis and osteogenesis stage, TiO₂ NTAs show the ability to induce osteogenic differentiation and the potential for blood vessel formation. In the end, we propose the multi-dimensional regulation of TiO₂ NTAs on titanium implants to achieve highly efficient manipulation of osseointegration, which may provide views on the rational design and development of titanium implants.

Modification of implant surfaces to stimulate mesenchymal cell activation

BACKGROUND

The process of osteointegration, as key point has the activation of mesenchymal cells at implant-bone interspace, their differentiation into osteoblasts and connection between the implant surface and the surrounding bone.

MAIN TEXT

Implant surfaces composed by biocompatible, organism-friendly materials require changes in content and surface morphology; changes that may further stimulate mesenchymal cell activation. The way the implant surfaces are affected with advantages and disadvantages, that typically bring each methodology, is also the purpose of this study. The study is of review type, based on finding articles about implant surface modification, with the aim of promoting the mesenchymal cell activation, utilizing keyword combination.

CONCLUSIONS

Implant success beyond the human element of the practicioner and the protocol element of implant treatment, also relies on the application of the right type of implant, at the right implant site, in accordance with oral and individual health status of the patient. Implant success does not depend on type of "coating" material of the implants. Based at this physiological process, the success or implant failure is not a process depending on the type of selected implant, because types of synthetic or natural materials that promote osteointegration are relatively in large number.

The Effect of Ultraviolet Treatment on TiO2 Nanotubes: A Study of Surface Characteristics, Bacterial Adhesion, and Gingival Fibroblast Response

Titanium dioxide (TiO2) nanotubes are emerging as a provocative target for oral implant research. The aim of this study was to evaluate the effect of UV on the wettability behavior, bacterial colonization, and fibroblast proliferation rate of TiO2 nanotube surfaces prepared using different anodization voltages and aimed for use as implant abutment materials. Four different experimental materials were prepared: (1) TiO2 nanotube 10 V; (2) TiO2 nanotube 15 V; (3) TiO2 nanotube 20 V; and (4) commercial pure titanium as a control group. TiO2 nanotube arrays were prepared in an aqueous electrolyte solution of hydrofluoric acid (HF, 0.5 vol.%). Different anodization voltages were used to modify the morphology of the TiO2 nanotubes. Equilibrium contact angles were measured using the sessile drop method with a contact angle meter. The investigated surfaces (n = 3) were incubated at 37 °C in a suspension of Streptococcus mutans (S. mutans) for 30 min for bacterial adhesion and 3 days for biofilm formation. Human gingival fibroblasts were plated and cultured on the experimental substrates for up to 7 days and the cell proliferation rate was assessed using the AlamarBlue assayTM (BioSource International, Camarillo, CA, USA). The data were analyzed using one-way ANOVA followed by Tukey’s post-hoc test. Water contact angle measurements on the TiO2 after UV treatment showed an overall hydrophilic behavior regardless of the anodization voltage. The ranking of the UV-treated surfaces of experimental groups from lowest to highest for bacterial adhesion was: TiO2 nanotube 20 V < Ti and TiO2 nanotube 15 V < TiO2 nanotube 10 V (p < 0.05), and for bacterial biofilm formation was: TiO2 nanotube 20 V-TiO2 nanotube 10 V < Ti-TiO2 nanotube 15 V (p < 0.05). Fibroblast cell proliferation was lower on TiO2 nanotube surfaces throughout the incubation period and UV light treatment showed no enhancement in cellular response. UV treatment enhances the wettability behavior of TiO2 nanotube surfaces and could result in lower bacterial adhesion and biofilm formation.

Role of Hippo-YAP Signaling in Osseointegration by Regulating Osteogenesis, Angiogenesis, and Osteoimmunology

The social demand for dental implantation is growing at a rapid rate, while dentists are faced with the dilemma of implantation failures associated with unfavorable osseointegration. Clinical-friendly osteogenesis, angiogenesis and osteoimmunology around dental implants play a pivotal role in a desirable osseointegration and it's increasingly appreciated that Hippo-YAP signaling pathway is implicated in those biological processes both in vitro and in vivo in a variety of study. In this article we review the multiple effects of Hippo-YAP signaling in osseointegration of dental implants by regulating osteogenesis, angiogenesis and osteoimmunology in peri-implant tissue, as well as highlight prospective future directions of relevant investigation.

Surface modification of titanium manufactured through selective laser melting inhibited osteoclast differentiation through mitogen-activated protein kinase signaling pathway

Selective laser melting used in manufacturing custom-made titanium implants becomes more popular. In view of the important role played by osteoclasts in peri-implant bone resorption and osseointegration, we modified selective laser melting-manufactured titanium surfaces using sandblasting/alkali-heating and sandblasting/acid-etching, and investigated their effect on osteoclast differentiation as well as their underlying mechanisms. The properties of the surfaces, including elements, roughness, wettability and topography, were analyzed. We evaluated the proliferation and morphology of primary mouse bone marrow-derived monocytes, as well as induced osteoclasts derived from bone marrow-derived monocytes, on samples. Then, osteoclast differentiation was determined by the tartrate-resistant acid phosphatase activity assay, calcitonin receptors immunofluorescence staining and the expression of osteoclast-related genes. The results showed that sandblasting/alkali-heating established nanonet structure with the lowest water contact angle, and both sandblasting/alkali-heating and sandblasting/acid-etching significantly decreased surface roughness and heterogeneity compared with selective laser melting. Surface modifications of selective laser melting-produced titanium altered bone marrow-derived monocyte morphology and suppressed bone marrow-derived monocyte proliferation and osteoclastogenesis in vitro (sandblasting/alkali-heating>sandblasting/acid-etching>selective laser melting). These surface modifications reduced the activation of extracellular signal-regulated kinase and c-Jun N-terminal kinases compared to native-selective laser melting. Sandblasting/alkali-heating additionally blocked tumor necrosis factor receptor-associated factor 6 recruitment. The results suggested that sandblasting/alkali-heating and sandblasting/acid-etching modifications on selective laser melting titanium could inhibit osteoclast differentiation through suppressing extracellular signal-regulated kinase and c-Jun N-terminal kinase phosphorylation in mitogen-activated protein kinase signaling pathway and provide a promising technique which might reduce peri-implant bone resorption for optimizing native-selective laser melting implants.