Strontium (Sr) and silver (Ag) loaded nanotubular structures with combined osteoinductive and antimicrobial activities

Drug Delivery Systems Based on Titania Nanotubes and Active Agents for Enhanced Osseointegration of Bone Implants

TiO2 nanotubes (TNTs) are attractive nanostructures for localized drug delivery. Owing to their excellent biocompatibility and physicochemical properties, numerous functionalizations of TNTs have been attempted for their use as therapeutic agent delivery platforms. In this review, we discuss the current advances in the applications of TNT-based delivery systems with an emphasis on the various functionalizations of TNTs for enhancing osteogenesis at the bone-implant interface and for preventing implant-related infection. Innovation of therapies for enhancing osteogenesis still represents a critical challenge in regeneration of bone defects. The overall concept focuses on the use of osteoconductive materials in combination with the use of osteoinductive or osteopromotive factors. In this context, we highlight the strategies for improving the functionality of TNTs, using five classes of bioactive agents: growth factors (GFs), statins, plant derived molecules, inorganic therapeutic ions/nanoparticles (NPs) and antimicrobial compounds.

Improved Immunoregulation of Ultra-Low-Dose Silver Nanoparticle-Loaded TiO2 Nanotubes via M2 Macrophage Polarization by Regulating GLUT1 and Autophagy

Introduction

The bone regeneration of endosseous implanted biomaterials is often impaired by the host immune response, especially macrophage-related inflammation which plays an important role in the bone healing process. Thus, it is a promising strategy to design an osteo-immunomodulatory biomaterial to take advantage of the macrophage-related immune response and improve the osseointegration performance of the implant.

Methods

In this study, we developed an antibacterial silver nanoparticle-loaded TiO₂ nanotubes (Ag@TiO₂-NTs) using an electrochemical anodization method to make the surface modification and investigated the influences of Ag@TiO₂-NTs on the macrophage polarization, osteo-immune microenvironment as well as its potential molecular mechanisms in vitro and in vivo.

Results

The results showed that Ag@TiO₂-NTs with controlled releasing of ultra-low-dose Ag⁺ ions had the excellent ability to induce the macrophage polarization towards the M2 phenotype and create a suitable osteo-immune microenvironment in vitro, via inhibiting PI3K/Akt, suppressing the downstream effector GLUT1, and activating autophagy. Moreover, Ag@TiO₂-NTs surface could improve bone formation, suppress inflammation, and promote osteo-immune microenvironment compared to the TiO₂-NTs and polished Ti surfaces in vivo. These findings suggested that Ag@TiO₂-NTs with controlled releasing of ultra-low-dose Ag⁺ ions could not only inhibit the inflammation process but also promote the bone healing by inducing healing-associated M2 polarization.

Discussion

Using this surface modification strategy to modulate the macrophage-related immune response, rather than prevent the host response, maybe a promising strategy for implant surgeries in the future.

Enhanced osteogenic differentiation of osteoblasts on CaTiO3 nanotube film

Improved implant-bone interface interaction for rapid formation of strong and long-lasting bond is significantly important in orthopedic clinics. Herein, Ca-doped TiO₂ nanotube film (M-CaNTs) with enhanced adhesion strength was fabricated on titanium (Ti) surface by an anodization-hydrothermal treatment. Results showed that TiO₂ nanotube film (M-NTs) fabricated by modified anodization was amorphous, exhibiting 100-nm diameter and 12-nm tube wall thickness. After hydrothermal treatment, the nanotubular structure of M-CaNTs kept integrated, but was volume-expanded, exhibiting a decreased diameter (∼ 60 nm) and an increased wall thickness (∼ 30 nm). The formation of M-CaNTs proceeded preferentially at the interior surfaces of the closely aligned nanotubes, involving an in situ dissolution-recrystallization process. Though the adhesion strength of M-CaNTs was weakened by the volume-expansion derived internal stress, it was still higher than that of the traditionally obtained one. In the in vitro investigations, the combination of nanotubular structure and Ca²⁺ could expectedly enhance the attachment, spreading and proliferation of MC3T3-E1 cells, as well as promote the expressions of bone-specific genes, intracellular proteins and ALP activity, which in turn accelerated collagen secretion and ECM mineralization. This work provides an attractive potential for the surface modification of Ti-based implants in clinical application.

Polymeric and inorganic nanoscopical antimicrobial fillers in dentistry

Failure of dental treatments is mainly due to the biofilm accumulated on the dental materials. Many investigations have been conducted on the advancements of antimicrobial dental materials. Polymeric and inorganic nanoscopical agents are capable of inhibiting microorganism proliferation. Applying them as fillers in dental materials can achieve enhanced microbicidal ability. The present review provides a broad overview on the state-of-the-art research in the field of antimicrobial fillers which have been adopted for incorporation into dental materials over the last 5 years. The antibacterial agents and applications are described, with the aim of providing information for future investigations. STATEMENT OF SIGNIFICANCE: Microbial infection is the primary cause of dental treatment failure. The present review provides an overview on the state-of-art in the field of antimicrobial nanoscopical or polymeric fillers that have been applied in dental materials. Trends in the biotechnological development of these antimicrobial fillers over the last 5 years are reviewed to provide a backdrop for further advancement in this field of research.

Advances in dual functional antimicrobial and osteoinductive biomaterials for orthopaedic applications

A vast growing problem in orthopaedic medicine is the increase of clinical cases with antibiotic resistant pathogenic microbes, which is predicted to cause higher mortality than all cancers combined by 2050. Bone infectious diseases limit the healing ability of tissues and increase the risk of future injuries due to pathologic tissue remodelling. The traditional treatment for bone infections has several drawbacks and limitations, such as lengthy antibiotic treatment, extensive surgical interventions, and removal of orthopaedic implants and/or prosthesis, all of these resulting in long-term rehabilitation. This is a huge burden to the public health system resulting in increased healthcare costs. Current technologies e.g. co-delivery systems, where antibacterial and osteoinductive agents are delivered encounter challenges such as site-specific delivery, sustained and prolonged release, and biocompatibility. In this review, these aspects are highlighted to promote the invention of the next generation biomaterials to prevent and/or treat bone infections and promote tissue regeneration.

Effect of anodized zirconium implants on early osseointegration process in adult rats: a histological and histomorphometric study

Since surface plays a key role in bioactivity, the response of the host to the biomaterial will determine the success or failure of the prosthesis. The purpose of this study is to make an exhaustive analysis of the histological and histochemical characteristics of new bone tissue around Zr implants anodized at 60 V (Zr60) supported by histomorphometric methods in a rat model. Fibrous tissue was observed around the control implants (Zr0) and osteoblasts were identified on the trabeculae close to the implantation site that showed typical cytological characteristics of active secretory cells, regardless of the surface condition. The histomorphometrical analysis revealed a significant increase in cancellous bone volume, trabecular thickness and in trabecular number together with a decrease in trabecular separation facing Zr60. TRAP staining showed that there was a relative increase in the number of osteoclasts for Zr60. In addition, a larger number of osteoclast with a greater number of nuclei were detected in the tibiae for Zr60. This research demonstrated that the new bone microarchitecture in contact with Zr60 is able to improve the early stages of the osseointegration process and consequently the primary stability of implants which is a crucial factor to reduce recovery time for patients.

Achievements in the Topographic Design of Commercial Titanium Dental Implants: Towards Anti-Peri-Implantitis Surfaces

Titanium and its alloys constitute the gold standard materials for oral implantology in which their performance is mainly conditioned by their osseointegration capacity in the host's bone. We aim to provide an overview of the advances in surface modification of commercial dental implants analyzing and comparing the osseointegration capacity and the clinical outcome exhibited by different surfaces. Besides, the development of peri-implantitis constitutes one of the most common causes of implant loss due to bacteria colonization. Thus, a synergic response from industry and materials scientists is needed to provide reliable technical and commercial solutions to this issue. The second part of the review focuses on an update of the recent findings toward the development of new materials with osteogenic and antibacterial capacity that are most likely to be marketed, and their correlation with implant geometry, biomechanical behavior, biomaterials features, and clinical outcomes.

Comprehensive In Vitro Testing of Calcium Phosphate-Based Bioceramics with Orthopedic and Dentistry Applications

Recently, a large spectrum of biomaterials emerged, with emphasis on various pure, blended, or doped calcium phosphates (CaPs). Although basic cytocompatibility testing protocols are referred by International Organization for Standardization (ISO) 10993 (parts 1-22), rigorous in vitro testing using cutting-edge technologies should be carried out in order to fully understand the behavior of various biomaterials (whether in bulk or low-dimensional object form) and to better gauge their outcome when implanted. In this review, current molecular techniques are assessed for the in-depth characterization of angiogenic potential, osteogenic capability, and the modulation of oxidative stress and inflammation properties of CaPs and their cation- and/or anion-substituted derivatives. Using such techniques, mechanisms of action of these compounds can be deciphered, highlighting the signaling pathway activation, cross-talk, and modulation by microRNA expression, which in turn can safely pave the road toward a better filtering of the truly functional, application-ready innovative therapeutic bioceramic-based solutions.

Antibacterial Nanostructured Ti Coatings by Magnetron Sputtering: From Laboratory Scales to Industrial Reactors

Based on an already tested laboratory procedure, a new magnetron sputtering methodology to simultaneously coat two-sides of large area implants (up to ~15 cm²) with Ti nanocolumns in industrial reactors has been developed. By analyzing the required growth conditions in a laboratory setup, a new geometry and methodology have been proposed and tested in a semi-industrial scale reactor. A bone plate (DePuy Synthes) and a pseudo-rectangular bone plate extracted from a patient were coated following the new methodology, obtaining that their osteoblast proliferation efficiency and antibacterial functionality were equivalent to the coatings grown in the laboratory reactor on small areas. In particular, two kinds of experiments were performed: Analysis of bacterial adhesion and biofilm formation, and osteoblasts–bacteria competitive in vitro growth scenarios. In all these cases, the coatings show an opposite behavior toward osteoblast and bacterial proliferation, demonstrating that the proposed methodology represents a valid approach for industrial production and practical application of nanostructured titanium coatings.

Strontium Effects on Human Gingival Fibroblasts

Strontium is a naturally occurring alkaline earth metal that has been shown to be useful not only in the treatment and prevention of osteoporosis but also in the treatment of dentinal hypersensitivity in the oral cavity; strontium is also an effective cariostatic, antiplaque, antigingivitis agent. Relatively little is known, however, about the effects of strontium on gingival fibroblasts. The purpose of the present investigation was to conduct in vitro studies on the potential for strontium to positively affect the activity of these cells such that it might be effective in the enhancement of gingival attachment to surfaces, such as healing abutments in implants in the oral cavity. The results indicate that strontium added as strontium citrate (0.5–1.0 mM), both in the absence and presence of a healing abutment, increases human gingival cell activity and decreases apoptosis in these cells. Scanning electron microscopy studies also reveal that the addition of strontium increases attachment of gingival fibroblasts to the surfaces of healing abutments. These studies provide the basis for further investigations on the use of strontium in the prevention and treatment of peri-implantitis by maximizing the formation of a peri-implant soft-tissue barrier.

Nanomaterial-Based Approaches for Neural Regeneration

Mechanical, thermal, chemical, or ischemic injury of the central or peripheral nervous system results in neuron loss, neurite damage, and/or neuronal dysfunction, almost always accompanied by sensorimotor impairment which alters the patient's life quality. The regenerative strategies for the injured nervous system are currently limited and mainly allow partial functional recovery, so it is necessary to develop new and effective approaches for nervous tissue regenerative therapy. Nanomaterials based on inorganic or organic and composite or hybrid compounds with tunable physicochemical properties and functionality proved beneficial for the transport and delivery/release of various neuroregenerative-relevant biomolecules or cells. Within the following paragraphs, we will emphasize that nanomaterial-based strategies (including nanosized and nanostructured biomaterials) represent a promising alternative towards repairing and regenerating the injured nervous system.

Effects of Programmed Local Delivery from a Micro/Nano-Hierarchical Surface on Titanium Implant on Infection Clearance and Osteogenic Induction in an Infected Bone Defect

The two major causes for implant failure are postoperative infection and poor osteogenesis. Initial period of osteointegration is regulated by immunocytes and osteogenic-related cells resulting in inflammatory response and tissue healing. The healing phase can be influenced by various environmental factors and biological cascade effect. To synthetically orchestrate bone-promoting factors on biomaterial surface, built is a dual delivery system coated on a titanium surface (abbreviated as AH-Sr-AgNPs). The results show that this programmed delivery system can release Ag⁺ and Sr²⁺ in a temporal-spatial manner to clear pathogens and activate preosteoblast differentiation partially through manipulating the polarization of macrophages. Both in vitro and in vivo assays show that AH-Sr-AgNPs-modified surface renders a microenvironment adverse for bacterial survival and favorable for macrophage polarization (M2), which further promotes the differentiation of preosteoblasts. Infected New Zealand rabbit femoral metaphysis defect model is used to confirm the osteogenic property of AH-Sr-AgNPs implants through micro-CT, histological, and histomorphometric analyses. These findings demonstrate that the programmed surface with dual delivery of Sr²⁺ and Ag⁺ has the potential of achieving an enhanced osteogenic outcome through favorable immunoregulation.

Long-lasting bactericidal activity through selective physical puncture and controlled ions release of polydopamine and silver nanoparticles-loaded TiO2 nanorods in vitro and in vivo

Background: Titanium (Ti) implant-associated infection, which is mostly caused by bacterial adhesion and biofilm formation, may result in implant failure and secondary surgery. Thus it is an urgent issue to prevent bacterial infections at the earliest step.

Purpose: To develop a novel surface strategy of polydopamine (PDA) and silver (Ag) nanoparticle-loaded TiO₂ nanorods (NRDs) coatings on Ti alloy.

Materials and methods: Ag-TiO₂@PDA NRDs was fabricated on Ti alloy by hydrothermal synthesis. The antibacterial activity of Ag-TiO₂@PDA NRDs against Escherichia coli and methicillin-resistant Staphylococcus aureus were tested by FE-SEM, Live/Dead staining, zone of inhibition, bacteria counting method and protein leakage analysis in vitro. In addition, an implant infection model was conducted and the samples were tested by X-ray, Micro-CT and histological analysis in vivo. Besides, cell morphology and cytotoxicity of Mouse calvarial cells (MC3T3-E1) were characterized by FE-SEM, immunofluorescence and CCK-8 test in vitro.

Results: Our study successfully developed a new surface coating of Ag-TiO₂@PDA NRDs. The selective physical puncture of bacteria and controlled release of Ag+ ions of Ag-TiO₂@PDA NRDs achieved a long-lasting bactericidal ability and anti-biofilm activity with satisfied biocompatibility.

Conclusion: This strategy may be promising for clinical applications to reduce the occurrence of infection in the implant surgeries

Antibacterial potential associated with drug-delivery built TiO2 nanotubes in biomedical implants

The fast evolution of surface treatments for biomedical implants and the concern with their contact with cells and microorganisms at early phases of bone healing has boosted the development of surface topographies presenting drug delivery potential for, among other features, bacterial growth inhibition without impairing cell adhesion. A diverse set of metal ions and nanoparticles (NPs) present antibacterial properties of their own, which can be applied to improve the implant local response to contamination. Considering the promising combination of nanostructured surfaces with antibacterial materials, this critical review describes a variety of antibacterial effects attributed to specific metals, ions and their combinations. Also, it explains the TiO2 nanotubes (TNTs) surface creation, in which the possibility of aggregation of an active drug delivery system is applicable. Also, we discuss the pertinent literature related to the state of the art of drug incorporation of NPs with antibacterial properties inside TNTs, along with the promising future perspectives of in situ drug delivery systems aggregated to biomedical implants.

Engineered titanium implants for localized drug delivery: recent advances and perspectives of Titania nanotubes arrays

INTRODUCTION

Therapeutics delivery to bones to treat skeletal diseases or prevent postsurgical infections is challenging due to complex and solid bone structure that limits blood supply and diffusion of therapeutics administered by systemic routes to reach effective concentration. Titanium (Ti) and their alloys are employed as mainstream implant materials in orthopedics and dentistry; having superior mechanical/biocompatibility properties which could provide an alternative solution to address this problem.

AREAS COVERED

This review presents an overview of recent development of Ti drug-releasing implants, with emphasis on nanoengineered Titania nanotubes (TNTs) structures, for solving key problems to improve implants osseointegration, overcome inflammation and infection together with providing localized drug delivery (LDD) for bone diseases including cancer. Critical analysis of the advantages/disadvantages of developed concepts is discussed, their drug loading/releasing performances and specific applications.

EXPERT OPINION

LDD to bones can address many disorders and postsurgical conditions such as inflammation, implants rejection and infection. To this end, TNTs-Ti implants represent a potential promise for the development of new generation of multifunctional implants with drug release functions. Even this concept is extensively explored recently, there is a strong need for more preclinical studies using animal models to confirm the long-term safety and stability of TNTs-Ti implants for real-life medical applications.

The interactions of dendritic cells with osteoblasts on titanium surfaces: an in vitro investigation

OBJECTIVES

Osteoimmune interactions possess a critical part in the integration of materials and hosts. Dendritic cells (DCs) are the most common members of osteoimmune cells family. The titanium surfaces of dental implants tend to promote a mature dendritic cell phenotype with increased proinflammatory secretion. However, very little is known to the effects of this microenvironment on the behaviors of cells around implants, especially osteoblasts, and how the tissue integrations take place on such biomaterial surfaces. Therefore, the present study was to investigate the interactions of DCs with osteoblasts on titanium surfaces. DCs seeded on PT and SLA titanium surfaces were compared by assays for the proliferations, surface markers, and inflammatory genes expressions.

MATERIALS AND METHODS

DCs seeded on PT and SLA titanium surfaces were compared by assays for the proliferations, surface markers, and inflammatory genes expressions. Next, we harvested the dendritic cell-conditioned medium (CM) and investigated the effects of CM on MC3T3-E1.

RESULTS

The results showed an increase in CD86 and proinflammatory expressions of DCs seeded on PT and SLA surfaces, as well as a decrease in anti-inflammatory cytokines. The CM from titanium surfaces inhibited the osteoblast differentiation with reduced expression of osteogenic genes RUNX2, COL1, ALP, and OCN and decreased ALP activity as well as Alizarin red staining.

CONCLUSION

These findings suggested that titanium surfaces switch DCs toward maturation phenotypes and thus inhibit the differentiation and mineralization of osteoblasts.

CLINICAL RELEVANCE

Knowing the significant impact of immune cells on osteogenesis behaviors, some efforts to decrease the immune reaction might be of clinical significance. Favorable immune environments can increase the dental implants survival rate in patients.

Poly(dopamine) and Ag nanoparticle-loaded TiO2 nanotubes with optimized antibacterial and ROS-scavenging bioactivities

AIM

To create polydopamine (PDA) and Ag nanoparticle-loaded TiO₂ nanotubes coating on titanium (Ti) alloy.

MATERIALS & METHODS

TiO₂-PDA-Ag coating was fabricated on Ti implants by electrochemical anodization. The in vitro and in vivo bactericidal and antibiofilm activities were tested. Intracellular reactive oxygen species (ROS) and antioxidative capability were measured, and cell proliferation, adhesion and cell morphology were characterized.

RESULTS

TiO₂-PDA-Ag coating showed satisfactory bactericidal and antibiofilm activities in vitro and in vivo, improved Ag release pattern, evident ROS scavenging properties and enhanced cell adhesion and proliferation.

CONCLUSION

Our study successfully fabricated a PDA and Ag nanoparticle-loaded TiO₂ nanotubes coating on Ti alloy. The improved Ag release kinetics and ROS-scavenging properties achieve an optimal balance between antibacterial ability and biocompatibility.

Biocompatibility evaluation of antibacterial Ti-Ag alloys with nanotubular coatings

BACKGROUND

Implant-related infection is a major problem postsurgery. As an alternative to a localized antibiotic release system, we used Ag to fabricate Ti-Ag alloys with nanotubular coatings (TiAg-NTs). Ag has excellent antibacterial properties, but its biological toxicity is a concern. Therefore, we performed biological experiments both in vitro and in vivo to evaluate the biocompatibility of TiAg-NTs with different concentrations of Ag (1%, 2%, and 4%).

METHODS

For in vitro experiments, cytocompatibility, including cell attachment, viability, and proliferation, was tested, and genes and proteins related to osteogenic differentiation were also evaluated. For in vivo assays, the rat femoral condylar insertion model was used, and micro-computed tomography (micro-CT) and histological analysis were conducted to analyze bone formation around implants at 1, 2, and 4 weeks after surgery.

RESULTS

Both in vitro and in vivo results indicate that Ti2%Ag-NT showed comparable cytocompatibility with commercially pure Ti (cp-Ti), and it could achieve good osseointegration with the surrounding bone tissue.

CONCLUSION

We thus believe that Ti2%Ag-NT is a potential biomaterial for orthopedics.

A facile fabrication of novel stuff with antibacterial property and osteogenic promotion utilizing red phosphorus and near-infrared light

Bone-implant materials are important for bone repairing and orthopedics surgery, which include bone plates and bone nails. These materials need to be designed not only considering its biostability and biocompatibility, but also their by-products induced infection after therapy or long-time treatment in vivo. Thus, the development of novel implant materials is quite urgent. Red phosphorus has great biocompatibility and exhibits efficient photothermal ability. Herein, a red phosphorus/IR780/arginine-glycine-asparticacid-cysteine (RGDC) coating on titanium bone-implant was prepared. The temperature sensitivity of Staphylococcus aureus biofilm is enhanced in the presence of ROS produced by IR780 with 808 nm light irradiation. With keeping the cells and tissues normal, a high antibacterial performance can be realized by near-infrared (808 nm) irradiated within 10 min at 50 °C. Besides the high effective antibacterial efficacy provided by photothermal therapy (PTT) and photodynamic therapy (PDT), the RGDC decorated surface can also possess an excellent performance in osteogenesis in vivo.

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A red phosphorus/IR780/arginine-glycine-asparticacid-cysteine (RGDC) coating on titanium bone-implant was prepared.

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The temperature sensitivity of Staphylococcus aureus biofilm is enhanced in the presence of ROS produced by IR780.

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A high antibacterial performance can be realized by near-infrared (808 nm) irradiated within 10 min at 50 °C.

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RGDC modified implants exhibit an excellent performance in osteogenesis in vivo.

Antibacterial surface modification of titanium implants in orthopaedics

The use of biomaterials in orthopaedics for joint replacement, fracture healing and bone regeneration is a rapidly expanding field. Infection of these biomaterials is a major healthcare burden, leading to significant morbidity and mortality. Furthermore, the cost to healthcare systems is increasing dramatically. With advances in implant design and production, research has predominately focussed on osseointegration; however, modification of implant material, surface topography and chemistry can also provide antibacterial activity. With the increasing burden of infection, it is vitally important that we consider the bacterial interaction with the biomaterial and the host when designing and manufacturing future implants. During this review, we will elucidate the interaction between patient, biomaterial surface and bacteria. We aim to review current and developing surface modifications with a view towards antibacterial orthopaedic implants for clinical applications.

Synergistic effects of titania nanotubes and silicon to enhance the osteogenic activity

In this study, titania nanotubes (TNTs) incorporating silicon (Si) were formed on Ti disks using anodization and electron beam evaporation (EBE) technology to improve the osteogenic activity. The amount of Si was exquisitely adjusted by controlling the duration of EBE to optimize the biofunctionality. As the Si was incorporated, the samples exhibited hydrophilic surfaces. Long lasting and controllable Si release was observed from the EBE-modified samples without cytotoxicity. Moreover, initial cell adhesion, spreading, proliferation and osteogenic differentiation of MC3T3-E1 cells were evaluated. The results showed a notable enhancement of spreading, osteogenesis and differentiation of cells on silicon-coated TNTs (Si-TNTs). In particular, samples with highest amount of silicon (∼5.93% Si) displayed greatest augmentation of ALP activity, osteogenic-related gene expression and mineralization compared to the others in the present study. It was indicated that the modification with TNTs and appropriated Si content resulted in enhanced osteoblastic spreading, proliferation and differentiation, and therefore has the potential for future applications in the field of orthopedics.

Potential antibacterial mechanism of silver nanoparticles and the optimization of orthopedic implants by advanced modification technologies

Infection, as a common postoperative complication of orthopedic surgery, is the main reason leading to implant failure. Silver nanoparticles (AgNPs) are considered as a promising antibacterial agent and always used to modify orthopedic implants to prevent infection. To optimize the implants in a reasonable manner, it is critical for us to know the specific antibacterial mechanism, which is still unclear. In this review, we analyzed the potential antibacterial mechanisms of AgNPs, and the influences of AgNPs on osteogenic-related cells, including cellular adhesion, proliferation, and differentiation, were also discussed. In addition, methods to enhance biocompatibility of AgNPs as well as advanced implants modifications technologies were also summarized.

An overview of application of silver nanoparticles for biomaterials in dentistry

Oral cavity is a gateway to the entire body and protection of this gateway is a major goal in dentistry. Plaque biofilm is a major cause of majority of dental diseases and although various biomaterials have been applied for their cure, limitations pertaining to the material properties prevent achievement of desired outcomes. Nanoparticle applications have become useful tools for various dental applications in endodontics, periodontics, restorative dentistry, orthodontics and oral cancers. Off these, silver nanoparticles (AgNPs) have been used in medicine and dentistry due to its antimicrobial properties. AgNPs have been incorporated into biomaterials in order to prevent or reduce biofilm formation. Due to greater surface to volume ratio and small particle size, they possess excellent antimicrobial action without affecting the mechanical properties of the material. This unique property of AgNPs makes these materials as fillers of choice in different biomaterials whereby they play a vital role in improving the properties. This review aims to discuss the influence of addition of AgNPs to various biomaterials used in different dental applications.

Effect of a biomimetic titania mesoporous coating doped with Sr on the osteogenic activity

Fabrication of titanium (Ti)-based biomedical implants with appropriate topography as well as capacity for drug delivery is highly pursued in the field of orthopedic and dental implants. In this study, a biomimetic mesoporous coating imbedded with strontium (MPs-Sr) is prepared by the high current anodization (HCA) and hydrothermal treatment (HT). This coating provides a more stable mechanical performance than the conventional nanotube arrays. The Sr loading is regulated by the HT reaction time and the Sr is released in a controllable manner from the MPs-Sr surface. The hydrophilic performance of MPs-Sr are significantly improved. Furthermore, it is showed that the attachment and spreading of preosteoblast MC3T3-E1 cells are significantly up-regulated by the nanoscale topology of MPs and the doped Sr. The improved collagen secretion and matrix mineralization levels of cells are closely related with the Sr release. The excellent osteogenic properties of MPs-Sr samples highlight their promising potential for use in clinical application.

Comparing the effect of strontium-functionalized and fluoride-modified surfaces on early osseointegration

BACKGROUND

Studies have shown that medical devices comprising strontium contribute to bone healing and osseointegration. The aim of this study was to evaluate the in vivo performance of surface-functionalized implants (Ti-Sr-O) showing predictable release characteristics of strontium and compare it to performance a commercially available fluoride-modified surface.

METHODS

Ti-Sr-O functionalized, fluoride-modified,  Grade 4 titanium implants were inserted in the femoral condyle of adult male New Zealand white rabbits. Atomic absorption spectrometry (AAS) was utilized to monitor strontium blood serum levels. Two weeks after insertion, histomorphometric evaluation was performed with respect to bone-to-implant contact (BIC%) and bone formation (BF%) using defined regions of interest.

RESULTS

Mean values for BIC% showed a comparable degree of osseointegration for Ti-Sr-O and the fluoride-modified surface, while BF% revealed a significant difference in increased BF with Ti-Sr-O. AAS measurements did not indicate any influence of the Ti-Sr-O modified implants on the strontium blood serum concentrations.

CONCLUSIONS

Within the limitations of this study, it was shown that the Ti-Sr-O coating, with sustained release characteristics of strontium, enhanced bone apposition and, thus, could find practical applications, e.g., within the field of medical implantology.

Osteoinductivity and Antibacterial Properties of Strontium Ranelate-Loaded Poly(Lactic-co-Glycolic Acid) Microspheres With Assembled Silver and Hydroxyapatite Nanoparticles

Bone-related infection rates are 4–64% in long open bone fractures and nearly 1% in joint-related surgeries. Treating bone infections and infection-related bone loss is very important. The present study prepared strontium ranelate (SR)-loaded poly(lactic-co-glycolic acid) (PLGA) microspheres (PM) with assembled silver nanoparticles (AgNPs) and hydroxyapatite nanoparticles (HANPs) (SR-PM-Ag-HA) through a novel solid-in-oil nanosuspension (S/O/N) method to achieve osteoinductivity and antibacterial properties. We evaluated the microstructure, drug release, biocompatibility, osteoinductivity, and antibacterial activity in vitro. The microspheres showed a stable shape and size. The cumulative drug release reached a maximum of ∼90% after 22 days. All groups loaded with SR enhanced MC3T3-E1 cell proliferation to a greater degree than pure PM. The osteoinductivity behavior was investigated by ALP staining and real-time PCR of osteogenic differentiation marker genes. The antibacterial activity was evaluated using antibacterial ability and biofilm formation assays. SR-PM-Ag-HA greatly enhanced osteogenic differentiation and showed excellent antibacterial properties. These results indicated that SR-PM-Ag-HA could be biocompatible and suitable for drug delivery, osteoinduction, and antibiosis, and therefore, have potential applications in the treatment of bone-related infections and promotion of bone formation at infected sites.

Effect of strontium surface-functionalized implants on early and late osseointegration: A histological, spectrometric and tomographic evaluation

Numerous in vivo, in vitro and clinical studies report on beneficial effects of strontium with respect to increased bone growth. Based on this knowledge the aim of this study was to evaluate early and late osseointegration stages of functionalized titanium implants showing sustained release of strontium (Sr) and further investigate its potential systemic effect. Strontium functionalized (Ti-Sr-O) and Grade 4 (Control) titanium implants were inserted in the femoral condyle of New Zealand White rabbits. The Ti-Sr-O coating was characterized using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectrometry (EDX) for structure, coating thickness and chemical composition. Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) was used to evaluate released strontium in vitro while Atomic Absorption Spectrometry (AAS) was utilized to monitor serum levels of strontium and calcium. Additionally, histological and tomographic analysis of bone-to-implant contact (BIC%) and bone formation (BF%) was performed, following implantation periods of two or twelve weeks, respectively. Median values for BIC% for Ti-Sr-O revealed significant differences within the two- and twelve-week observation periods, while exceeding BF% was discovered especially after twelve weeks when performing the histological evaluation. The results from the micro-computed tomography (µ-CT) showed no significant differences, when comparing the experimental groups. AAS measurements did not indicate a systemic effect by the local strontium release. Within the limitations of the study, it was shown that a Ti-Sr-O coating with sustained release characteristics of strontium, accelerates bone apposition and represents a potential potent surface modification for endosseous medical implant devices.

STATEMENT OF SIGNIFICANCE

This study presents first data with respect to early and late in vivo response on a strontium functionalized titanium surface comprising a nanotopography manufactured by a magnetron sputtering process. We investigated different osseointegration stages of screw-shaped implants with dental implant geometries in a rabbit femur model observing beneficial effects of the functionalized surface on bone-to-implant contact and bone formation caused by tailored release of the bone anabolic strontium. Histomorphometrical data revealed that a functionalized titanium surface with controlled liberation of strontium accelerates osseointegration while spectrometry measurements did not indicate a potential systemic effect of this osteoinductive agent and could thus have impact on modifications of medical implant devices.

Progress in TiO2 nanotube coatings for biomedical applications: a review

Titanium dioxide nanotubes (TNTs) have drawn wide attention and been extensively applied in the field of biomedicine, due to their large specific surface area, good corrosion resistance, excellent biocompatibility, and enhanced bioactivity. This review describes the preparation of TNTs and the surface modification that entrust the nanotubes with better antibacterial property and enhanced osteoblast adhesion, proliferation, and differentiation. Considering the contact between TNTs' surface and surrounding tissues after implantation, the interactions between TNTs (with properties including their diameter, length, wettability, and crystalline phase) and proteins, platelets, bacteria, and cells are illustrated. The state of the art in the applications of TNTs in dentistry, orthopedic implants, and cardiovascular stents are introduced. In particular, the application of TNTs in biosensing has attracted much attention due to its ability for the rapid diagnosis of diseases. Finally, the difficulties and challenges in the practical application of TNTs are also discussed.

Biofunctional Sr- and Si-loaded titania nanotube coating of Ti surfaces by anodization-hydrothermal process

BACKGROUND

Two frequent problems associated with titanium (Ti) surfaces of bone/dental implants are their corrosion and lack of native tissue integration.

METHODS

Here, we present an anodization-hydrothermal method for coating Ti surfaces with a layer of silicon (Si)- and strontium (Sr)-loaded titania nanotubes (TNs). The Ti surfaces coated with such a layer (Si-Sr-TNs) were characterized with different techniques.

RESULTS

The results indicate that the Si4+ and Sr2+ ions were evenly incorporated into the TNs and that the Si-Sr-TN layer provides good protection against corrosive media like simulated body fluid. The excellent cytocompatibility of the coating was confirmed in vitro by the significant growth and differentiation of MC3T3-E1 osteoblastic cells.

CONCLUSION

Being easily and economically fabricated, the Si-Sr-TN surfaces may find their niche in clinical applications, thanks to their excellent biological activity and corrosion resistance.

The effects of Sr-incorporated micro/nano rough titanium surface on rBMSC migration and osteogenic differentiation for rapid osteointegration

MNT-Sr can promote rBMSC osteogenic differentiation and significantly enhance rBMSC migration and homing via activation of SDF-1α/CXCR4 signaling.

Investigation of osteogenic responses of Fe-incorporated micro/nano-hierarchical structures on titanium surfaces

Fe incorporated micro/nano topographical titanium substrates are fabricated to synergistically regulate osteogenic responses in vitro and osseointegration in vivo.

Effect of titanium implants with strontium incorporation on bone apposition in animal models: A systematic review and meta-analysis

This systematic review aims to assess the efficacy of titanium (Ti) implant surfaces with or without strontium (Sr) incorporation on osseointegration in animal experimental studies. An electronic search was conducted using databases of PubMed and EMBASE up to November 2016 to identify studies focusing on osseointegration of strontium-modified titanium implants following PRISMA criteria. The primary outcome was the percentage of bone-to-implant contact (BIC) around the implants with or without strontium-modified surface. Of the 1320 studies, 17 studies fulfilling the inclusion criteria were finally included. A random effect meta-analysis was conducted based on BIC in 17 studies, and the results demonstrated considerable heterogeneity (I² = 79%). A sensitivity analysis found that three studies using the same surface modification method were the major source of the heterogeneity. Therefore, exploratory subgroup analysis was performed. Subgroup one including 14 studies showed a standard mean differences (SMD) of 1.42 (95% CI, 1.13-1.71) with no heterogeneity (I² = 0.0%), while subgroup two including the other three studies showed a SMD of 9.49.95% CI, 7.51-11.47) with low heterogeneity (I² = 0.1%). Sr-modified implants in both subgroups showed significantly higher BIC than unmodified implants (P < 0.01). The results showed a statistically significant effect of Sr-modified titanium implant surfaces on osseointegration and bone apposition in animal models.

Immunomodulatory Effects of Calcium and Strontium Co-Doped Titanium Oxides on Osteogenesis

The effects of calcium (Ca) or strontium (Sr) on host osteogenesis and immune responses have been investigated separately. In clinical practice, these two elements may both be present around an orthopedic device, but their potential synergistic effects on osteogenesis and the immune response have not been explored to date. In this work, we investigated the immunomodulatory effects of Ca and Sr co-doped titanium oxides on osteogenesis in vitro using the mouse macrophage cell line RAW 264.7 alone and in co-culture with mouse bone mesenchymal stem cells (BMSCs), and in vivo using a mouse air-pouch model. Coatings containing Ca and Sr at different concentration ratios were fabricated on titanium substrates using micro-arc oxidation and electrochemical treatment. The in vitro and in vivo results demonstrated that the Ca and Sr concentration ratio has a marked influence on macrophage polarization. The coating with a Ca/Sr ratio of 2:1 was superior to those with other Ca and/or Sr concentrations in terms of modulating M2 polarization, which enhanced osteogenic differentiation of mouse BMSCs in co-culture. These findings suggest that the osteoimmunomodulatory effect of a titanium-oxide coating can be enhanced by modulating the concentration ratio of its components.

Strontium-doped hydroxyapatite polysaccharide materials effect on ectopic bone formation

Previous studies performed using polysaccharide-based matrices supplemented with hydroxyapatite (HA) particles showed their ability to form in subcutaneous and intramuscular sites a mineralized and osteoid tissue. Our objectives are to optimize the HA content in the matrix and to test the combination of HA with strontium (Sr-HA) to increase the matrix bioactivity. First, non-doped Sr-HA powders were combined to the matrix at three different ratios and were implanted subcutaneously for 2 and 4 weeks. Interestingly, matrices showed radiolucent properties before implantation. Quantitative analysis of micro-CT data evidenced a significant increase of mineralized tissue formed ectopically with time of implantation and allowed us to select the best ratio of HA to polysaccharides of 30% (w/w). Then, two Sr-substitution of 8% and 50% were incorporated in the HA powders (8Sr-HA and 50Sr-HA). Both Sr-HA were chemically characterized and dispersed in matrices. In vitro studies performed with human mesenchymal stem cells (MSCs) demonstrated the absence of cytotoxicity of the Sr-doped matrices whatever the amount of incorporated Sr. They also supported osteoblastic differentiation and activated the expression of one late osteoblastic marker involved in the mineralization process i.e. osteopontin. In vivo, subcutaneous implantation of these Sr-doped matrices induced osteoid tissue and blood vessels formation.

Biotransformation of Silver Released from Nanoparticle Coated Titanium Implants Revealed in Regenerating Bone

Antimicrobial silver nanoparticle coatings have attracted interest for reducing prosthetic joint infection. However, few studies report in vivo investigations of the biotransformation of silver nanoparticles within the regenerating tissue and its impact on bone formation. We present a longitudinal investigation of the osseointegration of silver nanoparticle-coated additive manufactured titanium implants in rat tibial defects. Correlative imaging at different time points using nanoscale secondary ion mass spectrometry, transmission electron microscopy (TEM), histomorphometry, and 3D X-ray microcomputed tomography provided quantitative insight from the nano- to macroscales. The quality and quantity of newly formed bone is comparable between the uncoated and silver coated implants. The newly formed bone demonstrates a trabecular morphology with bone being located at the implant surface, and at a distance, at two weeks. Nanoscale elemental mapping of the bone-implant interface showed that silver was present primarily in the osseous tissue and colocalized with sulfur. TEM revealed silver sulfide nanoparticles in the newly regenerated bone, presenting strong evidence that the previously in vitro observed biotransformation of silver to silver sulfide occurs in vivo.

Emerging Trends in Micro- and Nanoscale Technologies in Medicine: From Basic Discoveries to Translation

We discuss the state of the art and innovative micro- and nanoscale technologies that are finding niches and opening up new opportunities in medicine, particularly in diagnostic and therapeutic applications. We take the design of point-of-care applications and the capture of circulating tumor cells as illustrative examples of the integration of micro- and nanotechnologies into solutions of diagnostic challenges. We describe several novel nanotechnologies that enable imaging cellular structures and molecular events. In therapeutics, we describe the utilization of micro- and nanotechnologies in applications including drug delivery, tissue engineering, and pharmaceutical development/testing. In addition, we discuss relevant challenges that micro- and nanotechnologies face in achieving cost-effective and widespread clinical implementation as well as forecasted applications of micro- and nanotechnologies in medicine.

Atomic Layer Deposition of a Silver Nanolayer on Advanced Titanium Orthopedic Implants Inhibits Bacterial Colonization and Supports Vascularized de Novo Bone Ingrowth

Joint replacement surgery is associated with significant morbidity and mortality following infection with either methicillin-resistant Staphylococcus aureus (MRSA) or Staphylococcus epidermidis. These organisms have strong biofilm-forming capability in deep wounds and on prosthetic surfaces, with 10³ -10⁴ microbes resulting in clinically significant infections. To inhibit biofilm formation, we developed 3D titanium structures using selective laser melting and then coated them with a silver nanolayer using atomic layer deposition. On bare titanium scaffolds, S. epidermidis growth was slow but on silver-coated implants there were significant further reductions in both bacterial recovery (p < 0.0001) and biofilm formation (p < 0.001). MRSA growth was similarly slow on bare titanium scaffolds and not further affected by silver coating. Ultrastructural examination and viability assays using either human bone or endothelial cells, demonstrated strong adherence and growth on titanium-only or silver-coated implants. Histological, X-ray computed microtomographic, and ultrastructural analyses revealed that silver-coated titanium scaffolds implanted into 2.5 mm defects in rat tibia promoted robust vascularization and conspicuous bone ingrowth. We conclude that nanolayer silver of titanium implants significantly reduces pathogenic biofilm formation in vitro, facilitates vascularization and osseointegration in vivo making this a promising technique for clinical orthopedic applications.

Strontium-loaded titania nanotube arrays repress osteoclast differentiation through multiple signalling pathways: In vitro and in vivo studies

The loosening of implants is an important clinical issue, particularly for patients with osteoporosis. In these patients, an implant should preferably both promote osteoblast differentiation and repress osteoclastic resorption. In the present study, we fabricated coatings containing TiO2 nanotubes (NTs) incorporated with strontium (Sr) on titanium (Ti) surfaces through hydrothermal treatment. The amount of loaded Sr was controlled by hydrothermally treating the samples in a Sr(OH)2 solution for 1 and 3 h (samples NT-Sr1h and NT-Sr3h, respectively) and found that both types of NT-Sr samples inhibited osteoclast differentiation by reducing the expression of osteoclast marker genes. Additionally, this inhibitory effect was mainly attributed to suppression of RANKL-induced activation of nuclear factor-κB (NF-κB). Moreover, NT-Sr also inhibited the Akt and nuclear factor of activated T-cell cytoplasmic 1 (NFATc1) signalling pathways. Interestingly, we also found that NT-Sr promoted RANKL-induced extracellular signal-regulated kinase (ERK) phosphorylation. Using ovariectomised rats as a model, we observed that NT-Sr prevented bone loss in vivo. In conclusion, our findings demonstrate that NT-Sr might effectively inhibit osteoclast differentiation by repressing the NF-κB and Akt/NFATc1 pathways and by negatively regulating the ERK pathway in vitro and in vivo.

Mussel-Inspired Multifunctional Hydrogel Coating for Prevention of Infections and Enhanced Osteogenesis

Prevention of postsurgery infection and promotion of biointegration are the key factors to achieve long-term success in orthopedic implants. Localized delivery of antibiotics and bioactive molecules by the implant surface serves as a promising approach toward these goals. However, previously reported methods for surface functionalization of the titanium alloy implants to load bioactive ingredients suffer from time-consuming complex processes and lack of long-term stability. Here, we present the design and characterization of an adhesive, osteoconductive, and antimicrobial hydrogel coating for Ti implants. To form this multifunctional hydrogel, a photo-cross-linkable gelatin-based hydrogel was modified with catechol motifs to enhance adhesion to Ti surfaces and thus promote coating stability. To induce antimicrobial and osteoconductive properties, a short cationic antimicrobial peptide (AMP) and synthetic silicate nanoparticles (SNs) were introduced into the hydrogel formulation. The controlled release of AMP loaded in the hydrogel demonstrated excellent antimicrobial activity to prevent biofilm formation. Moreover, the addition of SNs to the hydrogel formulation enhanced osteogenesis when cultured with human mesenchymal stem cells, suggesting the potential to promote new bone formation in the surrounding tissues. Considering the unique features of our implant hydrogel coating, including high adhesion, antimicrobial capability, and the ability to induce osteogenesis, it is believed that our design provides a useful alternative method for bone implant surface modification and functionalization.

Silver-loaded nanotubular structures enhanced bactericidal efficiency of antibiotics with synergistic effect in vitro and in vivo

Antibiotic-resistant bacteria have become a major issue due to the long-term use and abuse of antibiotics in treatments in clinics. The combination therapy of antibiotics and silver (Ag) nanoparticles is an effective way of both enhancing the antibacterial effect and decreasing the usage of antibiotics. Although the method has been proved to be effective in vitro, no in vivo tests have been carried out at present. Herein, we described a combination therapy of local delivery of Ag and systemic antibiotics treatment in vitro in an infection model of rat. Ag nanoparticle-loaded TiO₂ nanotube (NT) arrays (Ag-NTs) were fabricated on titanium implants for a customized release of Ag ion. The antibacterial properties of silver combined with antibiotics vancomycin, rifampin, gentamicin, and levofloxacin, respectively, were tested in vitro by minimum inhibitory concentration (MIC) assay, disk diffusion assay, and antibiofilm formation test. Enhanced antibacterial activity of combination therapy was observed for all the chosen bacterial strains, including gram-negative Escherichia coli (ATCC 25922), gram-positive Staphylococcus aureus (ATCC 25923), and methicillin-resistant Staphylococcus aureus (MRSA; ATCC 33591 and ATCC 43300). Moreover, after a relative short (3 weeks) combinational treatment, animal experiments in vivo further proved the synergistic antibacterial effect by X-ray and histological and immunohistochemical analyses. These results demonstrated that the combination of Ag nanoparticles and antibiotics significantly enhanced the antibacterial effect both in vitro and in vivo through the synergistic effect. The strategy is promising for clinical application to reduce the usage of antibiotics and shorten the administration time of implant-associated infection.

Osteogenic activity and angiogenesis of a SrTiO3 nano-gridding structure on titanium surface

Dual effect of alveolate double-layered SrTiO₃ nano-gridding based on Ti substrate: osteogenic activity and angiogenesis.

Dental implants modified with drug releasing titania nanotubes: therapeutic potential and developmental challenges

INTRODUCTION

The transmucosal nature of dental implants presents a unique therapeutic challenge, requiring not only rapid establishment and subsequent maintenance of osseointegration, but also the formation of resilient soft tissue integration. Key challenges in achieving long-term success are sub-optimal bone integration in compromised bone conditions and impaired trans-mucosal tissue integration in the presence of a persistent oral microbial biofilm. These challenges can be targeted by employing a drug-releasing implant modification such as TiO₂ nanotubes (TNTs), engineered on titanium surfaces via electrochemical anodization. Areas covered: This review focuses on applications of TNT-based dental implants towards achieving optimal therapeutic efficacy. Firstly, the functions of TNT implants will be explored in terms of their influence on osseointegration, soft tissue integration and immunomodulation. Secondly, the developmental challenges associated with such implants are reviewed including sterilization, stability and toxicity. Expert opinion: The potential of TNTs is yet to be fully explored in the context of the complex oral environment, including appropriate modulation of alveolar bone healing, immune-inflammatory processes, and soft tissue responses. Besides long-term in vivo assessment under masticatory loading conditions, investigating drug-release profiles in vivo and addressing various technical challenges are required to bridge the gap between research and clinical dentistry.

Immobilizing bacitracin on titanium for prophylaxis of infections and for improving osteoinductivity: An in vivo study

Bacitracin immobilized on the titanium (Ti) surface significantly improves anti-bacterial activity and biocompatibility in vitro. In the current study, we investigated the biologic performance (bactericidal effect and bone-implant integration) of bacitracin-modified Ti in vivo. A rat osteomyelitis model with femoral medullary cavity placement of Ti rods was employed to analyze the prophylactic effect of bacitracin-modified Ti (Ti-BC). Thirty-six female Sprague Dawley (SD) rats were used to establish the Ti implant-associated infection. The Ti and Ti-BC rods were incubated with and without Staphylococcus aureus to mimic the contaminated Ti rod and were implanted into the medullary cavity of the left femur, and sterile Ti rods were used as the blank control. After 3 weeks, the bone pathology was evaluated using X-ray and micro-computed tomography (micro-CT) analysis. For the investigation of the Ti-BC implant osseointegration in vivo, fifteen SD rats were divided into three groups (N=5), namely Ti, Ti-dopamine immobilized (Ti-DOPA), and Ti-BC. Ti rods were implanted into the left femoral cavity and micro-CT and histological evaluation was conducted after 12 weeks. The in vivo study indicated that Ti-immobilized bacitracin owned the prophylaxis potential for the infection associated with the Ti implants and allowed for the osseointegration. Thus, the multiple biofunctionalized Ti implants could be realized via immobilization of bacitracin, making them promising candidates for preventing the Ti implant-associated infections while retaining the osseointegration effects.

Titania nanotubes for orchestrating osteogenesis at the bone-implant interface

Titanium implants can fail due to inappropriate biomechanics at the bone-implant interface that leads to suboptimal osseointegration. Titania nanotubes (TNTs) fabricated on Ti implants by the electrochemical process have emerged as a promising modification strategy to facilitate osseointegration. TNTs enable augmentation of bone cell functions at the bone-implant interface and can be tailored to incorporate multiple functionalities including the loading of active biomolecules into the nanotubes to target anabolic processes in bone conditions such as osteoporotic fractures. Advanced functions can be introduced, including biopolymers, nanoparticles and electrical stimulation to release growth factors in a desired manner. This review describes the application of TNTs for enhancing osteogenesis at the bone-implant interface, as an alternative approach to systemic delivery of therapeutic agents.

Osteogenic and angiogenic activities of silicon-incorporated TiO2 nanotube arrays

Silicon-doped TiO₂ nanotube arrays may promote implant osseointegration through upregulating osteoblast and endothelial cell functions.