An updated review and recent advancements in carbon-based bioactive coatings for dental implant applications

BACKGROUND

Surface coating of dental implants with a bioactive biomaterial is one of the distinguished approaches to improve the osseointegration potential, antibacterial properties, durability, and clinical success rate of dental implants. Carbon-based bioactive coatings, a unique class of biomaterial that possesses excellent mechanical properties, high chemical and thermal stability, osteoconductivity, corrosion resistance, and biocompatibility, have been utilized successfully for this purpose.

AIM

This review aims to present a comprehensive overview of the structure, properties, coating techniques, and application of the various carbon-based coatings for dental implant applicationswith a particular focuson Carbon-based nanomaterial (CNMs), which is an advanced class of biomaterials.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Available articles on carbon coatings for dental implants were reviewed using PubMed, Science Direct, and Google Scholar resources. Carbon-based coatings are non-cytotoxic, highly biocompatible, chemically inert, and osteoconductive, which allows the bone cells to come into close contact with the implant surface and prevents bacterial attachment and growth. Current research and advancements are now more focused on carbon-based nanomaterial (CNMs), as this emerging class of biomaterial possesses the advantage of both nanotechnology and carbon and aligns closely with ideal coating material characteristics. Carbon nanotubes, graphene, and its derivatives have received the most attention for dental implant coating. Various coating techniques are available for carbon-based materials, chosen according to substrate type, application requirements, and desired coating thickness. Vapor deposition technique, plasma spraying, laser deposition, and thermal spraying techniques are most commonly employed to coat the carbon structures on the implant surface. Longer duration trials and monitoring are required to ascertain the role of carbon-based bioactive coating for dental implant applications.

Focal adhesion kinase (FAK): its structure, characteristics, and signaling in skeletal system

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase and distributes important regulatory functions in skeletal system. Mesenchymal stem cell (MSC) possesses significant migration and differentiation capacity, is an important source of distinctive bone cells production and a prominent bone development pathway. MSC has a wide range of applications in tissue bioengineering and regenerative medicine, and is frequently employed for hematopoietic support, immunological regulation, and defect repair, although current research is insufficient. FAK has been identified to cross-link with many other keys signaling pathways in bone biology and is considered as a fundamental "crossroad" on the signal transduction pathway and a "node" in the signal network to mediate MSC lineage development in skeletal system. In this review, we summarized the structure, characteristics, cellular signaling, and the interactions of FAK with other signaling pathways in the skeletal system. The discovery of FAK and its mediated molecules will lead to a new knowledge of bone development and bone construction as well as considerable potential for therapeutic use in the treatment of bone-related disorders such as osteoporosis, osteoarthritis, and osteosarcoma.

Functional engineering strategies of 3D printed implants for hard tissue replacement

Three-dimensional printing technology with the rapid development of printing materials are widely recognized as a promising way to fabricate bioartificial bone tissues. In consideration of the disadvantages of bone substitutes, including poor mechanical properties, lack of vascularization and insufficient osteointegration, functional modification strategies can provide multiple functions and desired characteristics of printing materials, enhance their physicochemical and biological properties in bone tissue engineering. Thus, this review focuses on the advances of functional engineering strategies for 3D printed biomaterials in hard tissue replacement. It is structured as introducing 3D printing technologies, properties of printing materials (metals, ceramics and polymers) and typical functional engineering strategies utilized in the application of bone, cartilage and joint regeneration.

Femtosecond laser optimization of PEEK: efficient bioactivity achieved by synergistic surface chemistry and structures

Poly-ether-ether-ketone (PEEK) is considered a potential orthopedic material due to the excellent mechanical properties and chemical resistance, but its biological inertness hampers its further clinical application. In this study, advanced femtosecond laser microfabrication technology was utilized to induce the change of the surface characteristics of PEEK to improve its bioactivity. Meanwhile, the mechanism of surface reaction and improved bioactivity was interpreted in detail from the perspective of material science. The surface physical-chemical characterization results showed that femtosecond laser etching could increase the surface energy, and the contents of active sites including amorphous carbon and carbon-hydroxyl on PEEK surfaces. In vitro validation experiments demonstrated that the samples etched with a femtosecond laser had a better ability to induce apatite deposition and cell proliferation than those treated with popular sulfonation modification, which would lead to better bioactivity and osteointegration. The current work fully presents the mechanism of the femtosecond laser low-temperature plasma effect on PEEK and the resulting surface characteristics, which could broaden the application of PEEK in the orthopedic field. Moreover, it has great potential in the surface design and modification of other biomaterials with enhanced bioactivity.

Modifying a 3D-Printed Ti6Al4V Implant with Polydopamine Coating to Improve BMSCs Growth, Osteogenic Differentiation, and In Situ Osseointegration In Vivo

Nowadays, 3D printing technology has been applied in dentistry to fabricate customized implants. However, the biological performance is unsatisfactory. Polydopamine (PDA) has been used to immobilize bioactive agents on implant surfaces to endow them with multiple properties, such as anti-infection and pro-osteogenesis, benefiting rapid osseointegration. Herein, we fabricated a PDA coating on a 3D-printed implant surface (3D-PDA) via the in situ polymerization method. Then the 3D-PDA implants' pro-osteogenesis capacity and the osseointegration performance were evaluated in comparison with the 3D group. The in vitro results revealed that the PDA coating modification increased the hydrophilicity of the implants, promoting the improvement of the adhesion, propagation, and osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) in vitro. Additionally, the 3D-PDA implant improved osteointegration performance in vivo. The present study suggested that PDA coating might be a feasible strategy to optimize 3D-printed implant surfaces, making a preliminary research basis for the subsequent work to immobilize bioactive factors on the 3D-printed implant surface.

In situ construction of a nano-structured akermanite coating for promoting bone formation and osseointegration of Ti-6Al-4V implants in a rabbit osteoporosis model

With the aging population worldwide, osteoporosis, as an age-related bone metabolic disease, is becoming a hot issue in public health. However, it is still a great challenge to realize osteoporotic bone healing due to the alteration of the bone microenvironment in osteoporosis patients. In this study, a nano-structured akermanite (nAK) coating was in situ constructed on Ti-6Al-4V implants to improve osteoporotic bone repair. In vitro studies indicated that both the surface nano-topography and bioactive ions released from the nAK coatings promoted the proliferation, osteogenesis, angiogenesis and inhibited osteoclastogenesis of ovariectomy rabbit-derived bone marrow mesenchymal stem cells (OVX-rBMSCs). Furthermore, the nAK-coated Ti-6Al-4V implants improved new bone formation and osseointegration in an osteoporosis rabbit model in vivo. These results indicated that the AK coating with a nano-structured surface on the Ti-6Al-4V implant could synergistically promote bone formation and osseointegration for osteoporosis patients. This may be a promising strategy to improve the bone regeneration and osseointegration capability of orthopedic implants under osteoporosis conditions.

Enhanced osteogenic activity and antibacterial performance in vitro of polyetheretherketone by plasma-induced graft polymerization of acrylic acid and incorporation of zinc ions

Polyetheretherketone (PEEK) has been widely used in the fields of orthopedics and trauma, but weak osteointegration and bacterial infection affect its long-term stability and repair effects. Surface modification is an effective way to improve the osteogenic and antibacterial activity of PEEK implants. In the present study, a layer of acrylic acid (AA) polymer coating loaded with zinc ions (Zn²⁺) was constructed on the surface of PEEK (PEEK-AA-Zn) using a strategy of combining plasma-induced graft polymerization with a chemical immersion technique. Successful construction of the AA coating remarkably enhanced the hydrophilicity of PEEK, and effectively loaded and released Zn²⁺. In vitro cell culture using MC3T3-E1 preosteoblasts showed that the Zn²⁺ released from PEEK-AA-Zn promoted cell proliferation and elevated gene expression levels of alkaline phosphatase (ALP), osteocalcin (OCN) and bone sialoprotein (BSP). Antibacterial tests revealed that PEEK-AA-Zn efficiently inhibited the proliferation of Staphylococcus aureus (S. aureus). These results suggest that the combined method of graft polymerization and ion incorporation endows PEEK with excellent osteogenic and antibacterial activity, which provides a wide range of possibilities for developing PEEK implants with multifunctional properties for bone tissue repair.

Engineering Single-Atomic Iron-Catalyst-Integrated 3D-Printed Bioscaffolds for Osteosarcoma Destruction with Antibacterial and Bone Defect Regeneration Bioactivity

Effective antitumor therapeutics with distinctive bactericidal and osteogenic properties are in high demand for comprehensive osteosarcoma treatment. Here, a "scaffold engineering" strategy that integrates highly active single-atomic iron catalysts (FeSAC) into a 3D printed bioactive glass (BG) scaffold is reported. Based on the atomically dispersed iron species within the catalysts, the engineered FeSAC displays prominent Fenton catalytic activity to generate toxic hydroxyl radicals (•OH) in response to the microenvironment specific to osteosarcoma. In addition, the constructed FeSAC-BG scaffold can serve as a sophisticated biomaterial platform for efficient osteosarcoma ablation, with concomitant bacterial sterilization via localized hyperthermia-reinforced nanocatalytic therapeutics. The destruction of the osteosarcoma, as well as the bacterial foci, can be achieved, further preventing susceptible chronic osteomyelitis during osteogenesis. In particular, the engineered FeSAC-BG scaffold is identified with advances in accelerated osteoconduction and osteoinduction, ultimately contributing to the sophisticated therapeutics and management of osteosarcoma. This work broadens the biomedical potential of single-atom catalysts and offers a comprehensive clinically feasible strategy for overall osteosarcoma therapeutics, bacterial inhibition, and tissue regeneration.

Advances in 3D-Printed Surface-Modified Ca-Si Bioceramic Structures and Their Potential for Bone Tumor Therapy

Bioceramics such as calcium silicate (Ca-Si), have gained a lot of interest in the biomedical field due to their strength, osteogenesis capability, mechanical stability, and biocompatibility. As such, these materials are excellent candidates to promote bone and tissue regeneration along with treating bone cancer. Bioceramic scaffolds, functionalized with appropriate materials, can achieve desirable photothermal effects, opening up a bifunctional approach to osteosarcoma treatments-simultaneously killing cancerous cells while expediting healthy bone tissue regeneration. At the same time, they can also be used as vehicles and cargo structures to deliver anticancer drugs and molecules in a targeted manner to tumorous tissue. However, the traditional synthesis routes for these bioceramic scaffolds limit the macro-, micro-, and nanostructures necessary for maximal benefits for photothermal therapy and drug delivery. Therefore, a different approach to formulate bioceramic scaffolds has emerged in the form of 3D printing, which offers a sustainable, highly reproducible, and scalable method for the production of valuable biomedical materials. Here, calcium silicate (Ca-Si) is reviewed as a novel 3D printing base material, functionalized with highly photothermal materials for osteosarcoma therapy and drug delivery platforms. Consequently, this review aims to detail advances made towards functionalizing 3D-printed Ca-Si and similar bioceramic scaffold structures as well as their resulting applications for various aspects of tumor therapy, with a focus on the external surface and internal dispersion functionalization of the scaffolds.

Surface engineering of biomaterials in orthopedic and dental implants: Strategies to improve osteointegration, bacteriostatic and bactericidal activities

BACKGROUND

The success of biomedical implants in orthopedic and dental applications is usually limited due to insufficient bone-implant integration, and implant-related infections. Biointerfaces are critical in regulating their interactions and the desirable performance of biomaterials in biological environment. Surface engineering has been widely studied to realize better control of the interface interaction to further enhance the desired behavior of biomaterials.

PURPOSE AND SCOPE

This review aims to investigate surface coating strategies in hard tissue applications to address insufficient osteointegration and implant-related infection problems.

SUMMARY

We first focused on surface coatings to enhance the osteointegration and biocompatibility of implants by emphasizing calcium phosphate-related, nanoscale TiO₂ -related, bioactive tantalum-based and biomolecules incorporated coatings. Different coating strategies such as plasma spraying, biomimetic deposition, electrochemical anodization and LENS are discussed. We then discussed techniques to construct anti-adhesive and bactericidal surface while emphasizing multifunctional surface coating techniques that combine potential osteointegration and antibacterial activities. The effects of nanotopography via TiO₂ coatings on antibacterial performance are interesting and included. A smart bacteria-responsive titanium dioxide nanotubes coating is also attractive and elaborated.

CONCLUSION

Developing multifunctional surface coatings combining osteogenesis and antimicrobial activity is the current trend. Surface engineering methods are usually combined to obtain hierarchical multiscale surface structures with better biofunctionalization outcomes.

A novel multifunctional carbon aerogel-coated platform for osteosarcoma therapy and enhanced bone regeneration

Nowadays, groundbreaking strategies are urgently needed to address drug resistance, osteolysis, bone defects and other predicaments impeding the therapeutic efficacy of osteosarcoma. Among them, photothermal therapy (PTT), using systematically administrated nanoagents, exhibits attractive therapeutic efficacy, yet is powerless in bone defect regeneration. Herein, a novel multifunctional beta-tricalcium phosphate (β-Ca3(PO4)2, β-TCP) bioceramic platform-coated with carbon aerogel (CA), which was initially developed for tumor therapy, was fabricated. On account of the desirable photothermal capabilities of CA, sufficient hyperthermia is generated under the irradiation of an 808 nm laser to achieve a thorough ablation of osteosarcoma tumors. Furthermore, CA-coated surfaces provide extra roughness and a higher specific surface area, which promoted the protein recruitment ability and osteogenesis via a fibronectin (FN)-mediated signaling pathway. The photothermal therapeutic efficacy and osteogenesis capability of CA-coated β-TCP-C suggests a novel approach for the treatment of osteosarcoma and provides provoking inspiration for the prospective bio-application of CA.

Osteoconductive and Osteoinductive Surface Modifications of Biomaterials for Bone Regeneration: A Concise Review

The main aim of bone tissue engineering is to fabricate highly biocompatible, osteoconductive and/or osteoinductive biomaterials for tissue regeneration. Bone implants should support bone growth at the implantation site via promotion of osteoblast adhesion, proliferation, and formation of bone extracellular matrix. Moreover, a very desired feature of biomaterials for clinical applications is their osteoinductivity, which means the ability of the material to induce osteogenic differentiation of mesenchymal stem cells toward bone-building cells (osteoblasts). Nevertheless, the development of completely biocompatible biomaterials with appropriate physicochemical and mechanical properties poses a great challenge for the researchers. Thus, the current trend in the engineering of biomaterials focuses on the surface modifications to improve biological properties of bone implants. This review presents the most recent findings concerning surface modifications of biomaterials to improve their osteoconductivity and osteoinductivity. The article describes two types of surface modifications: (1) Additive and (2) subtractive, indicating biological effects of the resultant surfaces in vitro and/or in vivo. The review article summarizes known additive modifications, such as plasma treatment, magnetron sputtering, and preparation of inorganic, organic, and composite coatings on the implants. It also presents some common subtractive processes applied for surface modifications of the biomaterials (i.e., acid etching, sand blasting, grit blasting, sand-blasted large-grit acid etched (SLA), anodizing, and laser methods). In summary, the article is an excellent compendium on the surface modifications and development of advanced osteoconductive and/or osteoinductive coatings on biomaterials for bone regeneration.

Advances of nanomaterial applications in oral and maxillofacial tissue regeneration and disease treatment

Using bioactive nanomaterials in clinical treatment has been widely aroused. Nanomaterials provide substantial improvements in the prevention and treatment of oral and maxillofacial diseases. This review aims to discuss new progresses in nanomaterials applied to oral and maxillofacial tissue regeneration and disease treatment, focusing on the use of nanomaterials in improving the quality of oral and maxillofacial healthcare, and discuss the perspectives of research in this arena. Details are provided on the tissue regeneration, wound healing, angiogenesis, remineralization, antitumor, and antibacterial regulation properties of nanomaterials including polymers, micelles, dendrimers, liposomes, nanocapsules, nanoparticles and nanostructured scaffolds, etc. Clinical applications of nanomaterials as nanocomposites, dental implants, mouthwashes, biomimetic dental materials, and factors that may interact with nanomaterials behaviors and bioactivities in oral cavity are addressed as well. In the last section, the clinical safety concerns of their usage as dental materials are updated, and the key knowledge gaps for future research with some recommendation are discussed. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement.

Involvement of FAK/P38 Signaling Pathways in Mediating the Enhanced Osteogenesis Induced by Nano-Graphene Oxide Modification on Titanium Implant Surface

BACKGROUND

Titanium implants are widely used in dental and orthopedic medicine. Nevertheless, there is limited osteoinductive capability of titanium leading to a poor or delayed osseointegration, which might cause the failure of the implant therapy. Therefore, appropriate modification on the titanium surface for promoting osseointegration of existing implants is still pursued.

PURPOSE

Graphene oxide (GO) is a promising candidate to perform implant surface biofunctionalization for modulating the interactions between implant surface and cells. So the objective of this study was to fabricate a bioactive GO-modified titanium implant surface with excellent osteoinductive potential and further investigate the underlying biological mechanisms.

MATERIALS AND METHODS

The large particle sandblasting and acid etching (SLA, commonly used in clinical practice) surface as a control group was first developed and then the nano-GO was deposited on the SLA surface via an ultrasonic atomization spraying technique to create the SLA/GO group. Their effects on rat bone marrow mesenchymal stem cells (BMSCs) responsive behaviors were assessed in vitro, and the underlying biological mechanisms were further systematically investigated. Moreover, the osteogenesis performance in vivo was also evaluated.

RESULTS

The results showed that GO coating was fabricated on the titanium substrates successfully, which endowed SLA surface with the improved hydrophilicity and protein adsorption capacity. Compared with the SLA surface, the GO-modified surface favored cell adhesion and spreading, and significantly improved cell proliferation and osteogenic differentiation of BMSCs in vitro. Furthermore, the FAK/P38 signaling pathways were proven to be involved in the enhanced osteogenic differentiation of BMSCs, accompanied by the upregulated expression of focal adhesion (vinculin) on the GO coated surface. The enhanced bone regeneration ability of GO-modified implants when inserted into rat femurs was also observed and confirmed that the GO coating induced accelerated osseointegration and osteogenesis in vivo.

CONCLUSION

GO modification on titanium implant surface has potential applications for achieving rapid bone-implant integration through the mediation of FAK/P38 signaling pathways.

Nanoparticles modified by polydopamine: Working as "drug" carriers

Inspired by the mechanism of mussel adhesion, polydopamine (PDA), a versatile polymer for surface modification has been discovered. Owing to its unique properties like extraordinary adhesiveness, excellent biocompatibility, mild synthesis requirements, as well as distinctive drug loading approach, strong photothermal conversion capacity and reactive oxygen species (ROS) scavenging facility, various PDA-modified nanoparticles have been desired as drug carriers. These nanoparticles with diverse nanostructures are exploited in multifunctions, consisting of targeting, imaging, chemical treatment (CT), photodynamic therapy (PDT), photothermal therapy (PTT), tissue regeneration ability, therefore have attracted great attentions in plenty biomedical applications. Herein, recent progress of PDA-modified nanoparticle drug carriers in cancer therapy, antibiosis, prevention of inflammation, theranostics, vaccine delivery and adjuvant, tissue repair and implant materials are reviewed, including preparation of PDA-modified nanoparticle drug carriers with various nanostructures and their drug loading strategies, basic roles of PDA surface modification, etc. The advantages of PDA modification in overcoming the existing limitations of cancer therapy, antibiosis, tissue repair and the developing trends in the future of PDA-modified nanoparticle drug carriers are also discussed.

•

Multifunctional PDA-modified drug systems are introduced in terms of classification, synthesis and drug loading strategies.

•

Basic roles of PDA surface modification in the drug systems are discussed.

•

Biomedical applications and unique advantages of the PDA-modified nanoparticle working as drug carriers are illustrated.

•

Challenges and perspectives for future development are proposed.

A comparative study of the osteogenic performance between the hierarchical micro/submicro-textured 3D-printed Ti6Al4V surface and the SLA surface

Three-dimensional (3D) printed titanium and its alloys have broad application prospect in the field of biomedical implant materials, although the biological performance of the original surface should be improved. Learning from the development experience of conventional titanium implants, to construct a hierarchical hybrid topological surface is the future direction of efforts. Since the original 3D-printed (3D hereafter) Ti6Al4V surface inherently has micron-scale features, in the present study, we introduced submicron-scale pits on the original surface by acid etching to obtain a hierarchical micro/submicro-textured surface. The characteristic and biological performance of the 3D-printed and acid-etched (3DA hereafter) surface were evaluated in vitro and in vivo, compared with the conventional sandblasted, large-grit, acid-etched (SLA hereafter) surface. Our results suggested the adhesion, proliferation and osteogenic differentiation of bone marrow derived mesenchymal stromal cells (BMSCs), as well as the in vivo osseointegration on 3DA surfaces were significantly improved. However, the overall osteogenic performance of the 3DA surface was not as good as the conventional SLA surface.