Decreased Staphylococcus epidermis adhesion and increased osteoblast functionality on antibiotic-loaded titania nanotubes

Surface modifications and coatings to improve osseointegration and antimicrobial activity on titanium surfaces: A statistical review over the last decade

Background

Titanium (Ti) is commonly employed therapeutically in many medical sectors associated with bone healing because of its superior mechanical properties and capacity to osseointegrate in the host bone tissue. The titanium surfaces may now be functionalized to offer additional and potentially valuable features. This review article discusses many titanium implant surface modifications, emphasizing their biological significance and the challenges that each one mainly addresses. Before reviewing the genuine reason for titanium surface modification in implanted devices, we briefly explore the process of osseointegration, enhancement of antibacterial properties, biocompatibility, and the historical significance of titanium as an implantable material, and the significant challenges involved. The various physical and chemical alterations that could take place on Ti surfaces are next examined. The rest of our talk will focus on creating inorganic and organic coatings for implanted Ti devices. Finally, we present a synopsis of the surface modification strategies currently being evaluated in clinical settings.

Target

This systematic review aims to evaluate research on titanium implants with significant surface modifications, coatings, and antibacterial capabilities.

Methods

Following the PRISMA paradigm, we searched for three electronic databases (Web of Science, PubMed Central, and Google Scholar) using the keywords "titanium implants," "titanium surface modification," and "titanium osseointegration," and "titanium antibacterial activity."

Results

We identified 1,39,336 articles overall that were published between 2012 and 2021, and we then focused on 8917 articles that concentrated on a particular topic. Clear inclusion and exclusion criteria were used in a rigorous screening procedure. Articles that didn't meet certain requirements (were irrelevant, used incorrect techniques, had unsuitable data values, or were only brief letters or communications) were eliminated. Finally, 120 research publications in total are taken into account for this extensive systematic review.

Conclusion

The report summarises current information on titanium implants with significant surface modifications, antibacterial activity, and coatings. It also gives some strong recommendations for future study topics.

Multiscale metal-based nanocomposites for bone and joint disease therapies

Bone and joint diseases are debilitating conditions that can result in significant functional impairment or even permanent disability. Multiscale metal-based nanocomposites, which integrate hierarchical structures ranging from the nanoscale to the macroscale, have emerged as a promising solution to this challenge. These materials combine the unique properties of metal-based nanoparticles (MNPs), such as enzyme-like activities, stimuli responsiveness, and photothermal conversion, with advanced manufacturing techniques, such as 3D printing and biohybrid systems. The integration of MNPs within polymer or ceramic matrices offers a degree of control over the mechanical strength, antimicrobial efficacy, and the manner of drug delivery, whilst concomitantly promoting the processes of osteogenesis and chondrogenesis. This review highlights breakthroughs in stimulus-responsive MNPs (e.g., photo-, magnetically-, or pH-activated systems) for on-demand therapy and their integration with biocomposite hybrids containing cells or extracellular vesicles to mimic the native tissue microenvironment. The applications of these composites are extensive, ranging from bone defects, infections, tumors, to degenerative joint diseases. The review emphasizes the enhanced load-bearing capacity, bioactivity, and tissue integration that can be achieved through hierarchical designs. Notwithstanding the potential of these applications, significant barriers to progress persist, including challenges related to long-term biocompatibility, regulatory hurdles, and scalable manufacturing. Finally, we propose future directions, including machine learning-guided design and patient-specific biomanufacturing to accelerate clinical translation. Multiscale metal-based nanocomposites, which bridge nanoscale innovations with macroscale functionality, are a revolutionary force in the field of biomedical engineering, providing personalized regenerative solutions for bone and joint diseases.

Antibacterial coatings for dental implants: A systematic review

OBJECTIVES

Despite the high survival rates of dental implants, peri-implantitis is a prevalent complication. Peri-implantitis is related to biofilm that adheres to the surface of implants and causes peri-implant chronic inflammation and bone destruction. Different surface treatments have been proposed to prevent biofilm formation. The objective of this systematic review was analyzing different types of antimicrobial coatings and identifying the most effective one(s) to control bacterial colonization over extended periods of analysis.

DATA, SOURCES AND STUDY SELECTION

We performed a bibliographic search in Pubmed and Cochrane base of articles published after 2010 to answer, according to the PICO system, the following question: What is the most effective antibacterial surface coating for dental implants? Only papers including a minimum follow-up bacteria growth analysis for at least 48 h were selected. After selection, the studies were classified using the PRISMA system. A total of 40 studies were included.

CONCLUSIONS

Three main categories of coatings were identified: Antibacterial peptides, synthetic antimicrobial molecules (polymers, antibiotics, …), and metallic nanoparticles (silver). Antibacterial peptide coatings to modify dental implant surfaces have been the most studied and effective surface modification to control bacterial colonization over extended periods of incubation as they are highly potent, durable and biocompatible. However, more in vitro and pre-clinical studies are needed to assess their true potential as a technology for preventing peri-implant infections.

In Vitro Evaluation of Probiotic Properties and Anti-Pathogenic Effects of Lactobacillus and Bifidobacterium Strains as Potential Probiotics

Probiotics restore gut microbial balance, thereby providing health-promoting effects to the host. They have long been suggested for managing intestinal disorders caused by pathogens and for improving gut health. This study evaluated the probiotic properties and anti-pathogenic effects of specific probiotic strains against the intestinal pathogens Staphylococcus aureus and Escherichia coli. The tested strains-Lactiplantibacillus plantarum LC27, Limosilactobacillus reuteri NK33, Lacticaseibacillus rhamnosus NK210, Bifidobacterium longum NK46, and Bifidobacterium bifidum NK175-were able to survive harsh conditions simulating gastric and intestinal fluids. These strains exhibited good auto-aggregation abilities (41.8-92.3%) and ideal hydrophobicity (30.9-85.6% and 38.3-96.1% for xylene and chloroform, respectively), along with the ability to co-aggregate with S. aureus (40.6-68.2%) and E. coli (38.6-75.2%), indicating significant adhesion levels to Caco-2 cells. Furthermore, these strains' cell-free supernatants (CFSs) demonstrated antimicrobial and antibiofilm activity against S. aureus and E. coli. Additionally, these strains inhibited gas production by E. coli through fermentative activity. These findings suggest that the strains tested in this study have potential as novel probiotics to enhance gut health.

TiO2 nanotubes with customized diameters for local drug delivery systems

In this study, we evaluated the drug release behavior of diameter customized TiO2 nanotube layers fabricated by anodization with various applied voltage sequences: conventional constant applied potentials of 20 V (45 nm) and 60 V (80 nm), a 20/60 V stepped potential (50 nm [two-diameter]), and a 20-60 V swept potential (49 nm [full-tapered]) (values in parentheses indicate the inner tube diameter at the top part of nanotube layers). The structures of the 50 nm (two-diameter) and 49 nm (full-tapered) samples had smaller inner diameters at the top part of nanotube layers than that of the 80 nm sample, while the outer diameters at the bottom part of nanotube layers were almost the same size as the 80 nm sample. The 80 nm sample, which had the largest nanotube diameter and length, exhibited the greatest burst release, followed by the 50 nm (two-diameter), 49 nm (full-tapered), and 45 nm samples. The initial burst released drug amounts and release rates from the 50 nm (two-diameter) and 49 nm (full-tapered) samples were significantly suppressed by the smaller tube top. On the other hand, the largest proportion of the slow released drug amount to the total released drug amount was observed for the 50 nm (two-diameter) sample. Thus, 50 nm (two-diameter) achieved suppressed initial burst release and large storage capacity. Therefore, this study has, for the first time, applied TiO2 nanotube layers with modulated diameters (two-diameter and full-tapered) to the realization of a localized drug delivery system (LDDS) with customized drug release properties.

TiO2 nanotubes as an antibacterial nanotextured surface for dental implants: Systematic review and meta-analysis

OBJECTIVES

Nanotechnology is constantly advancing in dental science, progressing several features aimed at improving dental implants. An alternative for surface treatment of dental implants is electrochemical anodization, which may generate a nanotubular surface (TiO2 nanotubes) with antibacterial potential and osteoinductive features. This systematic review and meta-analysis aims to elucidate the possible antibacterial properties of the surface in question compared to the untreated titanium surface.

SOURCES

For that purpose, was performed a systematic search on the bases PubMed, Lilacs, Embase, Web Of Science, Cinahl, and Cochrane Central, as well as, manual searches and gray literature.

STUDY SELECTION

The searches resulted in 742 articles, of which 156 followed for full-text reading. Then, 37 were included in the systematic review and 8 were included in meta-analysis.

RESULTS

Fifteen studies revealed significant antibacterial protection using TiO2 nanotube surfaces, while 15 studies found no statistical difference between control and nanotextured surfaces. Meta-analysis of in vitro studies demonstrated relevant bacterial reduction only for studies investigating Staphylococcus aureus in a period of 6 h. Meta-analysis of in vivo studies revealed three times lower bacterial adhesion and proliferation on TiO2 nanotube surfaces.

CONCLUSIONS

TiO2 nanotube topography as a surface for dental implants in preclinical research has demonstrated a positive relationship with antibacterial properties, nevertheless, factors such as anodization protocols, bacteria strains, and mono-culture methods should be taken into consideration, consequently, further studies are necessary to promote clinical translatability.

An Overview of Hydrothermally Synthesized Titanate Nanotubes: The Factors Affecting Preparation and Their Promising Pharmaceutical Applications

Recently, titanate nanotubes (TNTs) have been receiving more attention and becoming an attractive candidate for use in several disciplines. With their promising results and outstanding performance, they bring added value to any field using them, such as green chemistry, engineering, and medicine. Their good biocompatibility, high resistance, and special physicochemical properties also provide a wide spectrum of advantages that could be of crucial importance for investment in different platforms, especially medical and pharmaceutical ones. Hydrothermal treatment is one of the most popular methods for TNT preparation because it is a simple, cost-effective, and environmentally friendly water-based procedure. It is also considered as a strong candidate for large-scale production intended for biomedical application because of its high yield and the special properties of the resulting nanotubes, especially their small diameters, which are more appropriate for drug delivery and long circulation. TNTs' properties highly differ according to the preparation conditions, which would later affect their subsequent application field. The aim of this review is to discuss the factors that could possibly affect their synthesis and determine the transformations that could happen according to the variation of factors. To fulfil this aim, relevant scientific databases (Web of Science, Scopus, PubMed, etc.) were searched using the keywords titanate nanotubes, hydrothermal treatment, synthesis, temperature, time, alkaline medium, post treatment, acid washing, calcination, pharmaceutical applications, drug delivery, etc. The articles discussing TNTs preparation by hydrothermal synthesis were selected, and papers discussing other preparation methods were excluded; then, the results were evaluated based on a careful reading of the selected articles. This investigation and comprehensive review of different parameters could be the answer to several problems concerning establishing a producible method of TNTs production, and it might also help to optimize their characteristics and then extend their application limits to further domains that are not yet totally revealed, especially the pharmaceutical industry and drug delivery.

Fit and forget: The future of dental implant therapy via nanotechnology

Unlike orthopedic implants, dental implants require the orchestration of both osseointegration at the bone-implant interface and soft-tissue integration at the transmucosal region in a complex oral micro-environment with ubiquitous pathogenic bacteria. This represents a very challenging environment for early acceptance and long-term survival of dental implants, especially in compromised patient conditions, including aged, smoking and diabetic patients. Enabling advanced local therapy from the surface of titanium-based dental implants via novel nano-engineering strategies is emerging. This includes anodized nano-engineered implants eluting growth factors, antibiotics, therapeutic nanoparticles and biopolymers to achieve maximum localized therapeutic action. An important criterion is balancing bioactivity enhancement and therapy (like bactericidal efficacy) without causing cytotoxicity. Critical research gaps still need to be addressed to enable the clinical translation of these therapeutic dental implants. This review informs the latest developments, challenges and future directions in this domain to enable the successful fabrication of clinically-translatable therapeutic dental implants that would allow for long-term success, even in compromised patient conditions.

Antibacterial coatings on orthopedic implants

With the aging of population and the rapid improvement of public health and medical level in recent years, people have had an increasing demand for orthopedic implants. However, premature implant failure and postoperative complications frequently occur due to implant-related infections, which not only increase the social and economic burden, but also greatly affect the patient's quality of life, finally restraining the clinical use of orthopedic implants. Antibacterial coatings, as an effective strategy to solve the above problems, have been extensively studied and motivated the development of novel strategies to optimize the implant. In this paper, a variety of antibacterial coatings recently developed for orthopedic implants were briefly reviewed, with the focus on the synergistic multi-mechanism antibacterial coatings, multi-functional antibacterial coatings, and smart antibacterial coatings that are more potential for clinical use, thereby providing theoretical references for further fabrication of novel and high-performance coatings satisfying the complex clinical needs.

Craniofacial therapy: advanced local therapies from nano-engineered titanium implants to treat craniofacial conditions

Nano-engineering-based tissue regeneration and local therapeutic delivery strategies show significant potential to reduce the health and economic burden associated with craniofacial defects, including traumas and tumours. Critical to the success of such nano-engineered non-resorbable craniofacial implants include load-bearing functioning and survival in complex local trauma conditions. Further, race to invade between multiple cells and pathogens is an important criterion that dictates the fate of the implant. In this pioneering review, we compare the therapeutic efficacy of nano-engineered titanium-based craniofacial implants towards maximised local therapy addressing bone formation/resorption, soft-tissue integration, bacterial infection and cancers/tumours. We present the various strategies to engineer titanium-based craniofacial implants in the macro-, micro- and nano-scales, using topographical, chemical, electrochemical, biological and therapeutic modifications. A particular focus is electrochemically anodised titanium implants with controlled nanotopographies that enable tailored and enhanced bioactivity and local therapeutic release. Next, we review the clinical translation challenges associated with such implants. This review will inform the readers of the latest developments and challenges related to therapeutic nano-engineered craniofacial implants.

Strategies to Mitigate and Treat Orthopaedic Device-Associated Infections

Orthopaedic device implants play a crucial role in restoring functionality to patients suffering from debilitating musculoskeletal diseases or to those who have experienced traumatic injury. However, the surgical implantation of these devices carries a risk of infection, which represents a significant burden for patients and healthcare providers. This review delineates the pathogenesis of orthopaedic implant infections and the challenges that arise due to biofilm formation and the implications for treatment. It focuses on research advancements in the development of next-generation orthopaedic medical devices to mitigate against implant-related infections. Key considerations impacting the development of devices, which must often perform multiple biological and mechanical roles, are delineated. We review technologies designed to exert spatial and temporal control over antimicrobial presentation and the use of antimicrobial surfaces with intrinsic antibacterial activity. A range of measures to control bio-interfacial interactions including approaches that modify implant surface chemistry or topography to reduce the capacity of bacteria to colonise the surface, form biofilms and cause infections at the device interface and surrounding tissues are also reviewed.

Fabrication of gentamicin loaded Col-I/HA multilayers modified titanium coatings for prevention of implant infection

In this study, gentamicin loaded collagen I/hyaluronic acid multilayers modified titanium coating (TC-AA(C/H)6-G) was fabricated via a layer-by-layer (LBL) covalent immobilization method. The drug releasing properties of collagen I/Hyaluronic acid (Col-I/HA) multilayers and the effect of loaded gentamicin on the antibacterial properties and cytocompatibility of modified TC were investigated. The gentamicin release assay indicated that the Col-I/HA multilayers modified TC exhibited agreeable drug-loading amount (537.22 ± 29.66 µg of gentamicin) and controlled-release performance (240 h of sustained release time). TC-AA(C/H)6-G revealed satisfactory antibacterial activity and inhibited the colonization and biofilm formation of S. aureus. Fortunately, the functions of hMSCs on TC-AA(C/H)6-G did not affected by the loaded gentamicin, and TC-AA(C/H)6-G could improve the adhesion, proliferation and osteogenic differentiation of cells, as well as TC-AA(C/H)6. In vivo animal study indicated that TC-AA(C/H)6-G could effectively control intramedullary cavity infection caused by S. aureus and prevent bone destruction.

Preventing Peri-implantitis: The Quest for a Next Generation of Titanium Dental Implants

Titanium and its alloys are frequently the biomaterial of choice for dental implant applications. Although titanium dental implants have been utilized for decades, there are yet unresolved issues pertaining to implant failure. Dental implant failure can arise either through wear and fatigue of the implant itself or peri-implant disease and subsequent host inflammation. In the present report, we provide a comprehensive review of titanium and its alloys in the context of dental implant material, and how surface properties influence the rate of bacterial colonization and peri-implant disease. Details are provided on the various periodontal pathogens implicated in peri-implantitis, their adhesive behavior, and how this relationship is governed by the implant surface properties. Issues of osteointegration and immunomodulation are also discussed in relation to titanium dental implants. Some impediments in the commercial translation for a novel titanium-based dental implant from "bench to bedside" are discussed. Numerous in vitro studies on novel materials, processing techniques, and methodologies performed on dental implants have been highlighted. The present report review that comprehensively compares the in vitro, in vivo, and clinical studies of titanium and its alloys for dental implants.

Effect of bone-shaped nanotube-hydrogel drug delivery system for enhanced osseointegration

Anodic titanium dioxide nanotubes (TNT) have a range of beneficial theranostic properties. However, a lack of effective osseointegration is a problem frequently associated with the titanium dental implant surface. Here, we investigated whether bone-shaped nanotube titanium implants could enhance osseointegration via promoting initial release of vascular endothelial growth factor 165 (VEGF165) and dual release of recombinant human bone morphogenetic protein-2 (rhBMP-2). Thus, we generated cylindrical-shaped nanotubes (TNT1) and bone-shaped nanotubes (TNT2) through voltage-varying and time-varying electrochemical anodization methods, respectively. Additionally, we prepared rhBMP-2-loaded cylindrical-shaped nanotubes/VEGF165-loaded hydrogel (TNT-F1) and rhBMP-2-loaded bone-shaped nanotubes/VEGF165-loaded hydrogel (TNT-F2) drug delivery systems. We evaluated the characteristics and release kinetics of the drug delivery systems, and then analyzed the cytocompatibility and osteogenic differentiation of these specimens with mesenchymal stem cells (MSCs) in vitro. Finally, we utilized a rat femur defect model to test the bone formation capacity of nanotube-hydrogel drug delivery system in vivo. Among these different nanotubes structures, the bone-shaped one was the optimum structure for growth factor release.

Antimicrobial potential and osteoblastic cell growth on electrochemically modified titanium surfaces with nanotubes and selenium or silver incorporation

Titanium nanotube surfaces containing silver, zinc, and copper have shown antimicrobial effects without decreasing osteoblastic cell growth. In this in-vitro study we present first results on the biological evaluation of surface modifications by incorporating selenium and silver compounds into titanium-dioxide (TiO₂) nanotubes by electrochemical deposition. TiO₂-nanotubes (TNT) and Phosphate-doped TNT (pTNT) were grown on the surface of Ti6Al4V discs by anodization. Hydroxyapatite (HA), selenium (Se) and silver (Ag) compounds were incorporated by electrochemical deposition. Colony forming units of Staphylococcus epidermidis (DSM 3269) were significantly decreased in SepTNT (0.97 ± 0.18 × 10⁶ CFU/mL), SepTNT-HA (1.2 ± 0.39 × 10⁶ CFU/mL), AgpTNT (1.36 ± 0.42 × 10⁶ CFU/mL) and Ag₂SepTNT (0.999 ± 0.12 × 10⁶ CFU/mL) compared to the non-modified control (2.2 ± 0.21 × 10⁶ CFU/mL). Bacterial adhesion was calculated by measuring the covered area after fluorescence staining. Adhesion was lower in SepTNT (37.93 ± 12%; P = 0.004), pTNT (47.3 ± 6.3%, P = 0.04), AgpTNT (24.9 ± 1.8%; P < 0.001) and Ag₂SepTNT (14.9 ± 4.9%; P < 0.001) compared to the non-modified control (73.7 ± 11%). Biofilm formation and the growth of osteoblastic cells (MG-63) was observed by using Crystal Violet staining. Biofilm formation was reduced in SepTNT (22 ± 3%, P = 0.02) and Ag₂SepTNT discs (23 ± 11%, P = 0.02) compared to the non-modified control (54 ± 8%). In comparison with the non-modified control the modified SepTNT-HA and pTNT surfaces showed a significant higher covered area with osteoblastic MG-63-cells. Scanning electron microscope (SEM) images confirmed findings regarding bacterial and osteoblastic cell growth. These findings show a potential synergistic effect by combining selenium and silver with titanium nanotubes.

Construction of Local Drug Delivery System on Titanium-Based Implants to Improve Osseointegration

Titanium and its alloys are the most widely applied orthopedic and dental implant materials due to their high biocompatibility, superior corrosion resistance, and outstanding mechanical properties. However, the lack of superior osseointegration remains the main obstacle to successful implantation. Previous traditional surface modification methods of titanium-based implants cannot fully meet the clinical needs of osseointegration. The construction of local drug delivery systems (e.g., antimicrobial drug delivery systems, anti-bone resorption drug delivery systems, etc.) on titanium-based implants has been proved to be an effective strategy to improve osseointegration. Meanwhile, these drug delivery systems can also be combined with traditional surface modification methods, such as anodic oxidation, acid etching, surface coating technology, etc., to achieve desirable and enhanced osseointegration. In this paper, we review the research progress of different local drug delivery systems using titanium-based implants and provide a theoretical basis for further research on drug delivery systems to promote bone–implant integration in the future.

Latest Trends in Surface Modification for Dental Implantology: Innovative Developments and Analytical Applications

An increase in the world population and its life expectancy, as well as the ongoing concern about our physical appearance, have elevated the relevance of dental implantology in recent decades. Engineering strategies to improve the survival rate of dental implants have been widely investigated, focusing on implant material composition, geometry (usually guided to reduce stiffness), and interface surrounding tissues. Although efforts to develop different implant surface modifications are being applied in commercial dental prostheses today, the inclusion of surface coatings has gained special interest, as they can be tailored to efficiently enhance osseointegration, as well as to reduce bacterial-related infection, minimizing peri-implantitis appearance and its associated risks. The use of biomaterials to replace teeth has highlighted the need for the development of reliable analytical methods to assess the therapeutic benefits of implants. This literature review considers the state-of-the-art strategies for surface modification or coating and analytical methodologies for increasing the survival rate for teeth restoration.

Flumequine-loaded titanate nanotubes as antibacterial agents for aquaculture farms

Flumequine (FLUM), a quinolone-derived antibiotic is one of the most prescribed drugs in aquaculture farms. However, its intensive use becomes worrisome because of its environmental risks and the emergence of FLUM-resistant bacteria. To overcome these problems we propose in this study the encapsulation and the delivery of FLUM by titanate nanotubes (TiNTs). Optimal FLUM loading was reached by suspending the dehydrated powder nanomaterials (FLUM : TiNTs ratio = 1 : 5) in ethanol. The drug entrapment efficiency was calculated to be 80% approximately with a sustained release in PBS at 37 °C up to 5 days. Then FLUM@TiNTs was evaluated for both its in vitro drug release and antimicrobial activity against Escherichia coli (E. coli). Spectacularly high antibacterial activity compared to those of free FLUM antibiotic was obtained confirming the efficiency of TiNTs to protect FLUM from rapid degradation and transformation within bacteria improving thereby its antibacterial effect. Indeed FLUM@TiNTs was efficient to decrease gradually the bacterial viability to reach ≈5% after 5 days versus ≈75% with free FLUM. Finally, the ex vivo permeation experiments on sea bass (Dicentrachus labrax) intestine shows that TiNTs act to increase the intestinal permeation of FLUM during the experiment. Indeed the encapsulated FLUM flux increased 12 fold (1.46 μg cm² h⁻¹) compared to the free antibiotic (0.18 μg cm² h⁻¹). Thanks to its physical properties (diameter 10 nm, tubular shape…) and its high stability in the simulated intestinal medium, TiNTs are easy internalized by enterocytes, thus involving an endocytosis mechanism, and then improve intestinal permeation of FLUM. Taken together, FLUM@TiNTs hold potential as an effective approach for enhancing the antimicrobial activity of FLUM and pave the way not only for future pharmacokinetic studies in the treatment and targeting of fish infections but also for instating of novel strategies that overcome the challenges associated with the abusive use of antibiotics in fish farming.

Flumequine (FLUM), a quinolone-derived antibiotic is one of the most prescribed drugs in aquaculture farms.

Electrical stimulation of titanium to promote stem cell orientation, elongation and osteogenesis

Electrical stimulation of cells allows exogenous electric signals as stimuli to manipulate cell growth, preferential orientation and bone remodelling. In this study, commercially pure titanium discs were utilised in combination with a custom-built bioreactor to investigate the cellular responses of human mesenchymal stem cells via in-vitro functional assays. Finite element analysis revealed the homogeneous delivery of electric field in the bioreactor chamber with no detection of current density fluctuation in the proposed model. The custom-built bioreactor with capacitive stimulation delivery system features long-term stimulation with homogeneous electric field, biocompatible, sterilisable, scalable design and cost-effective in the manufacturing process. Using a continuous stimulation regime of 100 and 200 mV/mm on cp Ti discs, viability tests revealed up to an approximately 5-fold increase of cell proliferation rate as compared to non-stimulated controls. The human mesenchymal stem cells showed more elongated and differentiated morphology under this regime, with evidence of nuclear elongation and cytoskeletal orientation perpendicular to the direction of electric field. The continuous stimulation did not cause pH fluctuations and hydrogen peroxide production caused by Faradic reactions, signifying the suitability for long-term toxic free stimulation as opposed to the commonly used direct stimulation regime. An approximate of 4-fold increase in alkaline phosphatase production and approximately 9-fold increase of calcium deposition were observed on 200 mV/mm exposed samples relative to non-stimulated controls. It is worth noting that early stem cell differentiation and matrix production were observed under the said electric field even without the presence of chemical inductive growth factors. STATEMENT OF SIGNIFICANCE: This manuscript presents a study on combining pure titanium (primarily preferred as medical implant materials) and electrical stimulation in a purpose-built bioreactor with capacitive stimulation delivery system. A continuous capacitive stimulation regime on titanium disc has resulted in enhanced stem cell orientation, nuclei elongation, proliferation and differentiation as compared to non-stimulated controls. We believe that this manuscript creates a paradigm for future studies on the evolution of healthcare treatments in the area of targeted therapy on implantable and wearable medical devices through tailored innovative electrical stimulation approach, thereby influencing therapeutic conductive and electroactive biomaterials research prospects and development.

pH-Responsive ECM Coating on Ti Implants for Antibiosis in Reinfected Models

Reinfection of implants during their service life causes troubles to patients. Traditionally, physical loading or chemical bonding of antibacterial agents on implant surfaces cannot settle the repeated bacterial invasion after a period of implantation. In this work, a pH-responsive extracellular matrix (ECM) coating was fabricated on Ti. It consisted of hydroxyapatite (HA) nanorods, antimicrobial peptide (AMP) cross-linked collagen I nanonets (CA nanonets), and physically loaded AMPs. CA nanonets formed in the interspaces of HA nanorods and had an average pore size of 46.5 nm. With the increase in the weight ratio of AMP cross-linkers in collagen I (from 0 to 1:3), the isoelectric points of CA nanonets increased. CA nanonets linked with 50 wt % of AMPs (HCA1) had an isoelectric point of about 7, and their zeta potential shifted from electronegativity to electropositivity when the pH value changed from 7.4 to 6.0. Compared with other nanonets, HCA1 showed a pH-responsive blast release of physically loaded AMPs. It was due to the electrostatic repulsion between the physically adsorbed AMPs and HCA1 after a shift in the potential. In vitro, all the CA nanonets were cytocompatible and exhibited significant short-term antibacterial performance; however, just HCA1 showed outstanding long-time responsive antibacterial activity; in vivo, HCA1 inhibited bacterial infection and suppressed the inflammatory response, especially in a reinfected model, indicating its potential application in Ti implants to mitigate the risk of reinfection.

Fabrication and functionalization of biocompatible carboxymethyl chitosan/gelatin membranes via anodic electrophoretic deposition

A biocompatible CMC/G membrane for titanium substrates has been fabricated in an eco-friendly manner and could be a promising carrier for negatively charged agents.

Analytical Techniques for the Characterization of Bioactive Coatings for Orthopaedic Implants

The development of bioactive coatings for orthopedic implants has been of great interest in recent years in order to achieve both early- and long-term osseointegration. Numerous bioactive materials have been investigated for this purpose, along with loading coatings with therapeutic agents (active compounds) that are released into the surrounding media in a controlled manner after surgery. This review initially focuses on the importance and usefulness of characterization techniques for bioactive coatings, allowing the detailed evaluation of coating properties and further improvements. Various advanced analytical techniques that have been used to characterize the structure, interactions, and morphology of the designed bioactive coatings are comprehensively described by means of time-of-flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), 3D tomography, quartz crystal microbalance (QCM), coating adhesion, and contact angle (CA) measurements. Secondly, the design of controlled-release systems, the determination of drug release kinetics, and recent advances in drug release from bioactive coatings are addressed as the evaluation thereof is crucial for improving the synthesis parameters in designing optimal bioactive coatings.

Infection microenvironment-related antibacterial nanotherapeutic strategies

The emergence and spread of antibiotic resistance is one of the biggest challenges in public health. There is an urgent need to discover novel agents against the occurrence of multidrug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci. The drug-resistant pathogens are able to grow and persist in infected sites, including biofilms, phagosomes, or phagolysosomes, which are more difficult to eradicate than planktonic ones and also foster the development of drug resistance. For years, various nano-antibacterial agents have been developed in the forms of antibiotic nanocarriers. Inorganic nanoparticles with intrinsic antibacterial activity and inert nanoparticles assisted by external stimuli, including heat, photon, magnetism, or sound, have also been discovered. Many of these strategies are designed to target the unique microenvironment of bacterial infections, which have shown potent antibacterial effects in vitro and in vivo. This review summarizes ongoing efforts on antibacterial nanotherapeutic strategies related to bacterial infection microenvironments, including targeted antibacterial therapy and responsive antibiotic delivery systems. Several grand challenges and future directions for the development and translation of effective nano-antibacterial agents are also discussed. The development of innovative nano-antibacterial agents could provide powerful weapons against drug-resistant bacteria in systemic or local bacterial infections in the foreseeable future.

Improved Biocompatibility of TiO2 Nanotubes via Co-Precipitation Loading with Hydroxyapatite and Gentamicin

The antibacterial properties of titanium make it useful for clinical applications. Hydroxyapatite (HA) is widely utilized as a coating on orthopedic implants to improve osteointegration. Titanium oxide nanotubes (TNT) are recognized as a promising solution for local antibiotic therapy in bone implants. It is demonstrated that the utilization of HA-coated titanium can improve the biocompatibility of bone implants. This research aims to examine the antibacterial properties and biocompatibility of the TiO2 nanotubes by loading HA and gentamicin. In vitro testing, the characterization of drug release, cell adhesion and proliferation, bacteria culture, and antibacterial tests were conducted. During the in vivo experiments, Staphylococcus aureus was implanted into the femur of rats. The animals were sacrificed at four weeks followed by microbiological and clinical assessments on the bone, which were conducted by removing the implants followed by agar plating. The in vitro cell incubation demonstrated that the TiO2 nanotubes loaded with hydroxyapatite and gentamicin had better cellular compatibility compared to Cp–Ti. In addition, in vitro elution testing showed that gentamicin was released from the hydroxyapatite/TiO2 nanotubes for as long as 22 days. The release time was much longer than the TNT loaded with gentamicin at only 6 h. All animals in the gentamicin/HA/TNT group were free of infection compared to those in the Cp–Ti, TNT, and HA/gentamicin/TNT groups. There was a considerable reduction in the rates of infection among the rats with gentamicin-HA-TNT coatings compared to standard titanium. These results indicated that the co-precipitation of gentamicin and HA loading using the TNT method provided a novel prophylactic method against prosthetic infections and other biomedical applications.

Recent Strategies to Combat Infections from Biofilm-Forming Bacteria on Orthopaedic Implants

Biofilm-related implant infections (BRII) are a disastrous complication of both elective and trauma orthopaedic surgery and occur when an implant becomes colonised by bacteria. The definitive treatment to eradicate the infections once a biofilm has established is surgical excision of the implant and thorough local debridement, but this carries a significant socioeconomic cost, the outcomes for the patient are often poor, and there is a significant risk of recurrence. Due to the large volumes of surgical procedures performed annually involving medical device implantation, both in orthopaedic surgery and healthcare in general, and with the incidence of implant-related infection being as high as 5%, interventions to prevent and treat BRII are a major focus of research. As such, innovation is progressing at a very fast pace; the aim of this study is to review the latest interventions for the prevention and treatment of BRII, with a particular focus on implant-related approaches.

Microbial Decontamination and Antibacterial Activity of Nanostructured Titanium Dental Implants: A Narrative Review

Peri-implantitis is the major cause of the failure of dental implants. Since dental implants have become one of the main therapies for teeth loss, the number of patients with peri-implant diseases has been rising. Like the periodontal diseases that affect the supporting tissues of the teeth, peri-implant diseases are also associated with the formation of dental plaque biofilm, and resulting inflammation and destruction of the gingival tissues and bone. Treatments for peri-implantitis are focused on reducing the bacterial load in the pocket around the implant, and in decontaminating surfaces once bacteria have been detached. Recently, nanoengineered titanium dental implants have been introduced to improve osteointegration and provide an osteoconductive surface; however, the increased surface roughness raises issues of biofilm formation and more challenging decontamination of the implant surface. This paper reviews treatment modalities that are carried out to eliminate bacterial biofilms and slow their regrowth in terms of their advantages and disadvantages when used on titanium dental implant surfaces with nanoscale features. Such decontamination methods include physical debridement, chemo-mechanical treatments, laser ablation and photodynamic therapy, and electrochemical processes. There is a consensus that the efficient removal of the biofilm supplemented by chemical debridement and full access to the pocket is essential for treating peri-implantitis in clinical settings. Moreover, there is the potential to create ideal nano-modified titanium implants which exert antimicrobial actions and inhibit biofilm formation. Methods to achieve this include structural and surface changes via chemical and physical processes that alter the surface morphology and confer antibacterial properties. These have shown promise in preclinical investigations.

Multifunctional Titanium Surfaces for Orthopedic Implants: Antimicrobial Activity and Enhanced Osseointegration

The use of implants in orthopedics and dental practice is a widespread surgical procedure to treat diverse diseases. However, peri-implantitis due to infections and/or poor osseointegration can lead to metallic implant failure. The aim of this study was to develop a multifunctional coating on titanium (Ti) surfaces, to simultaneously deal with both issues, by combining antibacterial silver nanoparticles (AgNPs) and regenerative properties of lactoferrin (Lf). A simple and cost-effective methodology that allows the direct multifunctionalization of Ti surfaces was developed. The modified surfaces were characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy, and contact angle measurements. Additionally, in vitro preosteoblast cell adhesion, cell viability, and differentiation were evaluated. The antibacterial capability of the surfaces was tested against Staphylococcus aureus as a prosthesis infection model strain. Our results showed that Lf adsorbed on both Ti surfaces and Ti surfaces with adsorbed AgNPs. Simultaneously, the presence of Lf and AgNPs notably improved preosteoblast adhesion, proliferation, and differentiation, whereas it reduced the bacterial colonization by 97.7%. Our findings indicate that this simple method may have potential applications in medical devices to both improve osseointegration and reduce bacterial infection risk, enhancing successful implantation and patients' quality of life.

Antibiotic-loaded amphora-shaped pores on a titanium implant surface enhance osteointegration and prevent infections

Artificial prostheses for joint replacement are indispensable in orthopedic surgery. Unfortunately, the implanted surface is attractive to not only host cells but also bacteria. To enable better osteointegration, a mechanically stable porous structure was created on a titanium surface using laser treatment and metallic silver particles were embedded in a hydrophilic titanium oxide layer on top. The laser structuring resulted in unique amphora-shaped pores. Due to their hydrophilic surface conditions and capillary forces, the pores can be loaded preoperative with the antibiotic of choice/need, such as gentamicin. Cytotoxicity and differentiation assays with primary human osteoblast-like cells revealed no negative effect of the surface modification with or without gentamicin loading. An in vivo biocompatibility study showed significantly enhanced osteointegration as measured by push-out testing and histomorphometry 56 days after the implantation of the K-wires into rat femora. Using a S. aureus infection model, the porous, silver-coated K-wires slightly reduced the signs of bone destruction, while the wires were still colonized after 28 days. Loading the amphora-shaped pores with gentamicin significantly reduced the histopathological signs of bone destruction and no bacteria were detected on the wires. Taken together, this novel surface modification can be applied to new or established orthopedic implants. It enables preoperative loading with the antibiotic of choice/need without further equipment or post-coating, and supports osteointegration without a negative effect of the released dug, such as gentamicin.

Vancomycin Hydrochloride Loaded Hydroxyapatite Mesoporous Microspheres with Micro/Nano Surface Structure to Increase Osteogenic Differentiation and Antibacterial Ability

As infection induced by the implant will lead to operation failure, the implant material must be endowed with certain antibacterial properties. Hydroxyapatite (HA) mesoporous microspheres have been widely used in bone repair due to their advantages, including simple synthesis, good osteogenic properties and drug loading capacity. In this study, vancomycin hydrochloride-loaded mesoporous hydroxyapatite microspheres with micro/nanosurface structures were synthesized to increase osteogenic differentiation and antibacterial ability. Phytic acid (IP6) was used as a template to prepare mesoporous hydroxyapatite microspheres composed of fibres, flakes and smooth surfaces by the hydrothermal homogeneous precipitation method, and the corresponding specific surface areas were 65.20 m²/g, 75.13 m²/g and 71.27 m²/g, respectively. Vancomycin hydrochloride (Van) was used as the drug model to study the drug loading and release characteristics of the microspheres, as well as the in vitro antibacterial properties after treatment. In addition, during cocultivation with MC3T3-E1 preosteoblasts, HA microspheres assembled via flakes exhibited better cell compatibility, which promoted cell proliferation, alkaline phosphatase (ALP) activity, and the formation of calcium nodules and increased the expression of osteogenic differentiation-related proteins such as Runx-2, osteopontin (OPN) and collagen I (COL I). These results indicated that the HA microspheres prepared in this experiment have broad application prospects in drug delivery systems and bone repair.

Antibacterial metals and alloys for potential biomedical implants

Metals and alloys, including stainless steel, titanium and its alloys, cobalt alloys, and other metals and alloys have been widely used clinically as implant materials, but implant-related infection or inflammation is still one of the main causes of implantation failure. The bacterial infection or inflammation that seriously threatens human health has already become a worldwide complaint. Antibacterial metals and alloys recently have attracted wide attention for their long-term stable antibacterial ability, good mechanical properties and good biocompatibility in vitro and in vivo. In this review, common antibacterial alloying elements, antibacterial standards and testing methods were introduced. Recent developments in the design and manufacturing of antibacterial metal alloys containing various antibacterial agents were described in detail, including antibacterial stainless steel, antibacterial titanium alloy, antibacterial zinc and alloy, antibacterial magnesium and alloy, antibacterial cobalt alloy, and other antibacterial metals and alloys. Researches on the antibacterial properties, mechanical properties, corrosion resistance and biocompatibility of antibacterial metals and alloys have been summarized in detail for the first time. It is hoped that this review could help researchers understand the development of antibacterial alloys in a timely manner, thereby could promote the development of antibacterial metal alloys and the clinical application.

Research to Clinics: Clinical Translation Considerations for Anodized Nano-Engineered Titanium Implants

Titania nanotubes (TNTs) fabricated on titanium orthopedic and dental implants have shown significant potential in "proof of concept" in vitro, ex vivo, and short-term in vivo studies. However, most studies do not focus on a clear direction for future research towards clinical translation, and there exists a knowledge gap in identifying key research challenges that must be addressed to progress to the clinical setting. This review focuses on such challenges with respect to anodized titanium implants modified with TNTs, including optimized fabrication on clinically utilized microrough surfaces, clinically relevant bioactivity assessments, and controlled/tailored local release of therapeutics. Further, long-term in vivo investigations in compromised animal models under loading conditions are needed. We also discuss and detail challenges and progress related to the mechanical stability of TNT-based implants, corrosion resistance/electrochemical stability, optimized cleaning/sterilization, packaging/aging, and nanotoxicity concerns. This extensive, clinical translation focused review of TNTs modified Ti implants aims to foster improved understanding of key research gaps and advances, informing future research in this domain.

Understanding and optimizing the antibacterial functions of anodized nano-engineered titanium implants

Nanoscale surface modification of titanium-based orthopaedic and dental implants is routinely applied to augment bioactivity, however, as is the case with other cells, bacterial adhesion is increased on nano-rough surfaces. Electrochemically anodized Ti implants with titania nanotubes (TNTs) have been proposed as an ideal implant surface with desirable bioactivity and local drug release functions to target various conditions. However, a comprehensive state of the art overview of why and how such TNTs-Ti implants acquire antibacterial functions, and an in-depth knowledge of how topography, chemistry and local elution of potent antibiotic agents influence such functions has not been reported. This review discusses and details the application of nano-engineered Ti implants modified with TNTs for maximum local antibacterial functions, deciphering the interdependence of various characteristics and the fine-tuning of different parameters to minimize cytotoxicity. An ideal implant surface should cater simultaneously to ossoeintegration (and soft-tissue integration for dental implants), immunomodulation and antibacterial functions. We also evaluate the effectiveness and challenges associated with such synergistic functions from modified TNTs-implants. Particular focus is placed on the metallic and semi-metallic modification of TNTs towards enabling bactericidal properties, which is often dose dependent. Additionally, there are concerns over the cytotoxicity of these therapies. In that light, research challenges in this domain and expectations from the next generation of customizable antibacterial TNTs implants towards clinical translation are critically evaluated. STATEMENT OF SIGNIFICANCE: One of the major causes of titanium orthopaedic/dental implant failure is bacterial colonization and infection, which results in complete implant failure and the need for revision surgery and re-implantation. Using advanced nanotechnology, controlled nanotopographies have been fabricated on Ti implants, for instance anodized nanotubes, which can accommodate and locally elute potent antibiotic agents. In this pioneering review, we shine light on the topographical, chemical and therapeutic aspects of antibacterial nanotubes towards achieving desirable tailored antibacterial efficacy without cytotoxicity concerns. This interdisciplinary review will appeal to researchers from the wider scientific community interested in biomaterials science, structure and function, and will provide an improved understanding of controlling bacterial infection around nano-engineered implants, aimed at bridging the gap between research and clinics.

Toward Bactericidal Enhancement of Additively Manufactured Titanium Implants

Implant-associated infections (IAIs) are among the most intractable and costly complications in implant surgery. They can lead to surgery failure, a high economic burden, and a decrease in patient quality of life. This manuscript is devoted to introducing current antimicrobial strategies for additively manufactured (AM) titanium (Ti) implants and fostering a better understanding in order to pave the way for potential modern high-throughput technologies. Most bactericidal strategies rely on implant structure design and surface modification. By means of rational structural design, the performance of AM Ti implants can be improved by maintaining a favorable balance between the mechanical, osteogenic, and antibacterial properties. This subject becomes even more important when working with complex geometries; therefore, it is necessary to select appropriate surface modification techniques, including both topological and chemical modification. Antibacterial active metal and antibiotic coatings are among the most commonly used chemical modifications in AM Ti implants. These surface modifications can successfully inhibit bacterial adhesion and biofilm formation, and bacterial apoptosis, leading to improved antibacterial properties. As a result of certain issues such as drug resistance and cytotoxicity, the development of novel and alternative antimicrobial strategies is urgently required. In this regard, the present review paper provides insights into the enhancement of bactericidal properties in AM Ti implants.

Advancing of titanium medical implants by surface engineering: recent progress and challenges

Introduction:Titanium (Ti) and their alloys are used as main implant materials in orthopedics and dentistry for decades having superior mechanical properties, chemical stability and biocompatibility. Their rejections due lack of biointegration and bacterial infection are concerning with considerable healthcare costs and impacts on patients. To address these limitations, conventional Ti implants need improvements where the use of surface nanoengineering approaches and the development of a new generation of implants are recognized as promising strategies.Areas covered:This review presents an overview of recent progress on the application of surface engineering methods to advance Ti implants enable to address their key limitations. Several promising surface engineering strategies are presented and critically discussed to generate advanced surface properties and nano-topographies (tubular, porous, pillars) able not only to improve their biointegration, antibacterial performances, but also to provide multiple functions such as drug delivery, therapy, sensing, communication and health monitoring underpinning the development of new generation and smart medical implants.Expert opinion:Recent advances in cell biology, materials science, nanotechnology and additive manufacturing has progressively influencing improvements of conventional Ti implants toward the development of the next generation of implants with improved performances and multifunctionality. Current research and development are in early stage, but progressing with promising results and examples of moving into in-vivo studies an translation into real applications.

Titanium dioxide nanotubes as drug carriers for infection control and osteogenesis of bone implants

Titanium implants have been widely used as one of the most effective treatments of bone defects. However, the lack of osteogenesis and bacteria-resistant activities result in high infection and loosening rates of titanium implants. Anodic oxidation could easily construct titanium dioxide nanotubes (TNTs) array on the surface of titanium, and the rough surface of TNTs is beneficial to the growth of osteoblast-related cells on the surface. And TNTs could be excellent drug carriers because of their single-entry tubular hollow structure. In this review, we aim at detailing the application of TNTs as drug carriers in the field of bone implants. Starting from the topography of TNTs, we illustrated the biological activity of the TNTs surface, the drugs for loading in TNTs, and the controlled and responsive release strategies of drug-loaded TNTs, respectively. At the end of this review, the shortcomings of TNTs as the drug carrier in the field of bone implants are discussed, and the development direction of this research field is also prospected.

Antibiotic-Loaded MMT/PLL-Based Coating on the Surface of Endosseous Implants to Suppress Bacterial Infections

BACKGROUND

Bone infections remain one of the most common and serious complications of orthopedic surgery, posing a tremendous economic burden to society and patients. This is because bacteria colonize and multiply on the surface of the implant. The (MMT/PLL)8 multilayer films have been shown to effectively release antibiotics depending on the changes in the microenvironment. Here, vancomycin was loaded into the (MMT/PLL)8 multilayer films, which were prepared to be used as a local delivery system for the treatment of bone infections.

METHODS

We used the layer-by-layer self-assembly method to prepare VA-loaded coatings (MMT/PLL-VA)8 consisting of montmorillonite (MMT), poly-L-lysine (PLL), and VA. The thickness and surface morphology of coatings were characterized using spectroscopic ellipsometry and scanning electron microscopy (SEM). In order to evaluate the drug release behavior from coatings in different media, we measured the size of the zone of inhibition. Additionally, in vitro antibacterial activity was assessed using the shake-flask culture method and SEM images, while that of in vivo was evaluated by establishing an animal model of bone infection.

RESULTS

Our findings revealed that small-molecule antibiotics were successfully loaded into the (MMT/PLL-VA)8 multilayer film structure during the hierarchical self-assembly process and subsequently the multilayer film structure depicted linear growth behavior. The PLL in the multilayer films was progressively degraded which triggered the VA release when contacted with CMS or bacterial infections. The release of VA from multilayer film structure depends on the concentration changes of CMS. Notably, the multilayer films presented great in vitro cell compatibility. Moreover, the prepared antibacterial multilayer films showed excellent antibacterial property by killing more than 99.99% of S. aureus in 24 h. More importantly, we found that multilayer film exhibits good sterilization effect and biocompatibility under the stimulation of bacterial liquid both in vitro and in vivo antibacterial ability tests.

CONCLUSION

Altogether, this study shows that (MMT/PLL-VA)8 multilayer films containing CMS and bacteria-responsive drug release properties posess high bactericidal activity and good biocompatibility. This finding provides a novel strategy for the treatment of bone infections.

Antimicrobial loading of nanotubular titanium surfaces favoring surface coverage by mammalian cells over bacterial colonization

Titanium is frequently used for dental implants, percutaneous pins and screws or orthopedic joint prostheses. Implant surfaces can become peri-operatively contaminated by surgically introduced bacteria during implantation causing lack of surface coverage by mammalian cells and subsequent implant failure. Especially implants that have to function in a bacteria-laden environment such as dental implants or percutaneous pins, cannot be surgically implanted while being kept sterile. Accordingly, contaminating bacteria adhering to implant surfaces hamper successful surface coverage by mammalian cells required for long-term functioning. Here, nanotubular titanium surfaces were prepared and loaded with Ag nanoparticles or gentamicin with the aim of killing contaminating bacteria in order to favor surface coverage by mammalian cells. In mono-cultures, unloaded nanotubules did not cause bacterial killing, but loading of Ag nanoparticles or gentamicin reduced the number of adhering Staphylococcus aureus or Pseudomonas aeruginosa CFUs. A gentamicin-resistant Staphylococcus epidermidis was only killed upon loading with Ag nanoparticles. However, unlike low-level gentamicin loading, loading with Ag nanoparticles also caused tissue-cell death. In bi-cultures, low-level gentamicin-loading of nanotubular titanium surfaces effectively eradicated contaminating bacteria favoring surface coverage by mammalian cells. Thus, care must be taken in loading nanotubular titanium surfaces with Ag nanoparticles, while low-level gentamicin-loaded nanotubular titanium surfaces can be used as a local antibiotic delivery system to negate failure of titanium implants due to peri-operatively introduced, contaminating bacteria without hampering surface coverage by mammalian cells.

Mixed oxide nanotubes in nanomedicine: A dead-end or a bridge to the future?

Nanomedicine has seen a significant rise in the development of new research tools and clinically functional devices. In this regard, significant advances and new commercial applications are expected in the pharmaceutical and orthopedic industries. For advanced orthopedic implant technologies, appropriate nanoscale surface modifications are highly effective strategies and are widely studied in the literature for improving implant performance. It is well-established that implants with nanotubular surfaces show a drastic improvement in new bone creation and gene expression compared to implants without nanotopography. Nevertheless, the scientific and clinical understanding of mixed oxide nanotubes (MONs) and their potential applications, especially in biomedical applications are still in the early stages of development. This review aims to establish a credible platform for the current and future roles of MONs in nanomedicine, particularly in advanced orthopedic implants. We first introduce the concept of MONs and then discuss the preparation strategies. This is followed by a review of the recent advancement of MONs in biomedical applications, including mineralization abilities, biocompatibility, antibacterial activity, cell culture, and animal testing, as well as clinical possibilities. To conclude, we propose that the combination of nanotubular surface modification with incorporating sensor allows clinicians to precisely record patient data as a critical contributor to evidence-based medicine.

Layered double hydroxide-based antioxidant dispersions with high colloidal and functional stability

Highly stable antioxidant dispersions were designed on the basis of ring-opened ellagic acid (EA) intercalated into MgAl-layered double hydroxide (LDH) nanoparticles. The morphology of the composite was delicately modified with ethanolic washing to obtain EtOH-EA-LDH with a high specific surface area. The colloidal stability was optimized by surface functionalization with positively charged polyelectrolytes. Polyethyleneimine (PEI), protamine sulfate (PS) and poly(acrylamide-co-diallyl dimethyl ammonium chloride) (PAAm-co-DADMAC) was adsorbed onto the surface of the oppositely charged EtOH-EA-LDH leading to charge neutralization and overcharging at appropriate doses. Formation of adsorbed polyelectrolyte layers provided remarkable colloidal stability for the EtOH-EA-LDH. Modification with PEI and PAAm-co-DADMAC outstandingly improved the resistance of the particles against salt-induced aggregation with a critical coagulation concentration value above 1 M, while only limited stability was achieved by covering the nanoparticles with PS. The high antioxidant activity of EtOH-EA-LDH was greatly preserved upon polyelectrolyte coating, which was proved in the scavenging of radicals in the test reaction applied. Hence, an active antioxidant nanocomposite of high drug dose and remarkable colloidal stability was obtained to combat oxidative stress in systems of high electrolyte concentrations.

How microbes read the map: Effects of implant topography on bacterial adhesion and biofilm formation

Microbes have remarkable capabilities to attach to the surface of implanted medical devices and form biofilms that adversely impact device function and increase the risk of multidrug-resistant infections. The physicochemical properties of biomaterials have long been known to play an important role in biofilm formation. More recently, a series of discoveries in the natural world have stimulated great interest in the use of 3D surface topography to engineer antifouling materials that resist bacterial colonization. There is also increasing evidence that some medical device surface topographies, such as those designed for tissue integration, may unintentionally promote microbial attachment. Despite a number of reviews on surface topography and biofilm control, there is a missing link between how bacteria sense and respond to 3D surface topographies and the rational design of antifouling materials. Motivated by this gap, we present a review of how bacteria interact with surface topographies, and what can be learned from current laboratory studies of microbial adhesion and biofilm formation on specific topographic features and medical devices. We also address specific biocompatibility considerations and discuss how to improve the assessment of the anti-biofilm performance of topographic surfaces. We conclude that 3D surface topography, whether intended or unintended, is an important consideration in the rational design of safe medical devices. Future research on next-generation smart antifouling materials could benefit from a greater focus on translation to real-world applications.

β-FeOOH/Fe-TiO2 heterojunctions on Ti for bacteria inactivation under light irradiation and biosealing

Intraosseous transcutaneous implants transferring mechanical stress directly from the skeleton to a prosthesis are an area of biological mechanics. However, bacterial invasion and weak biosealing with skin tissue usually induce implant failure. In this paper, composite coatings consisting of β-FeOOH as an outer layer and Fe-TiO₂ as an inner layer were prepared on Ti via micro-arc oxidation and hydrothermal treatment (HT). The surface microstructures and optical absorption properties of the coatings were observed, the production of reactive oxygen species (ROS) was measured, Staphylococcus aureus (S. aureus) and fibroblast behaviors were studied in vitro, and bacteria inactivation and skin tissue responses on different surfaces were evaluated in vivo. The results show that Fe³⁺ was doped into TiO₂ and β-FeOOH nanoparticles were gradually deposited on TiO₂ during HT treatment, forming β-FeOOH/Fe-TiO₂ heterojunctions. The light absorption of the composite coatings shifted to the longer wavelength region because of a narrowed TiO₂ bandgap and the formation of heterojunctions. Under light irradiation, photoinduced electrons and holes on the heterojunctions were separated efficiently. Via optimizing the amount of Fe³⁺ in TiO₂, ROS that formed at the heterojunctions after light irradiation for 10 min could kill 80% of S. aureus compared with pure Ti in vitro, but they did not affect fibroblast behavior, including proliferation and phenotyping. In vivo, the optimized β-FeOOH/Fe-TiO₂ heterojunctions, upon light irradiation, could inhibit bacterial infection, suppress an inflammatory response, and promote integration with skin tissue. Such results provide a new perspective suggesting the potential application of β-FeOOH/Fe-TiO₂ heterojunctions in percutaneous Ti implants, especially in infected cases.

Effects of the local administration of antibiotics on bone formation on implant surface in animal models: A systematic review and meta-analysis

PURPOSE

This review aimed to evaluate the effects of the local delivery of antibiotics incorporated in implant surfaces on some quantitative parameters of bone formation.

MATERIALS AND METHODS

An electronic search was undertaken in three databases (PubMed, Scopus, Embase) in addition to hand searching. The search was limited to animal experiments using endosseous implants combined with localized antibiotics release. Meta-analyses were performed for the percentages of bone volume (BV) and bone-to-implant contact (BIC).

RESULTS

Nine studies met the inclusion criteria. Several methods were identified for local delivery of antibiotics at the bone-implant interface, but the most commonly used method was by coating (incorporating the implant surface with the antibiotic agents). Different antibiotic agents were used, namely bacitracin, doxycycline, enoxacin, gentamicin, minocycline, tobramycin, and vancomycin. There was no statistically significant difference in the percentage of BIC between implants with or without localized antibiotic release (P = 0.59). The meta-analysis revealed higher BV around implants coated with antibiotics compared to control groups (without antibiotics) (P < 0.01).

CONCLUSION

It is suggested that the local administration of antibiotics around implants did not adversely affect the percentage of direct bone contact around implants, with a tendency for a slightly better bone formation around implants when combined with local administration of antibiotics. It is a matter of debate whether these in vivo results will have the same effect in the clinical setting. However, the risk of bias of these studies may, to some extent, question the validity of these results.

Mechano-Bactericidal Titanium Surfaces for Bone Tissue Engineering

Despite advances in the development of bone substitutes and strict aseptic procedures, the majority of failures in bone grafting surgery are related to nosocomial infections. Development of biomaterials combining both osteogenic and antibiotic activity is, therefore, a crucial public health issue. Herein, two types of intrinsically bactericidal titanium supports were fabricated by using commercially scalable techniques: plasma etching or hydrothermal treatment, which display two separate mechanisms of mechano-bactericidal action. Hydrothermal etching produces a randomly nanostructured surface with sharp nanosheet protrusions killing bacteria via cutting of the cell membrane, whereas plasma etching of titanium produces a microscale two-tier hierarchical topography that both reduce bacterial attachment and rupture those bacteria that encounter the surface. The adhesion, growth, and proliferation of human adipose-derived stem cells (hASCs) on the two mechano-bactericidal topographies were assessed. Both types of supports allowed the growth and proliferation of the hASCs in the same manner and cells retained their stemness and osteogenic potential. Furthermore, these supports induced osteogenic differentiation of hASCs without the need of differentiation factors, demonstrating their osteoinductive properties. This study proves that these innovative mechano-bactericidal titanium surfaces with both regenerative and bactericidal properties are a promising solution to improve the success rate of reconstructive surgery.

Preparation and characterization of a novel polylactic acid/hydroxyapatite composite scaffold with biomimetic micro-nanofibrous porous structure

Combining synthetic polymer scaffolds with inorganic bioactive factors is widely used to promote the bioactivity and bone conductivity of bone tissue. However, except for the chemical composition of scaffold, the biomimetic structure also plays an important role in its application. In this study, we report the fabrication of polylactic acid/hydroxyapatite (PLA/HA) composite nanofibrous scaffolds via phase separation method to mimic the native extracellular matrix (ECM). The SEM analysis showed that the addition of HA dramatically impacted the morphology of the PLA matrix, which changed from 3D nanofibrous network structure to a disorderly micro-nanofibrous porous structure. At the same time, HA particles could be evenly dispersed at the end of the fiber. The FTIR and XRD demonstrated that there was not any chemical interaction between PLA and HA. Thermal analyses showed that HA could decrease the crystallization of PLA, but improve the thermal decomposition temperature of the composite scaffold. Moreover, water contact angle analysis of the PLA/HA composite scaffold demonstrated that the hydrophilicity increased with the addition of HA. Furthermore, apatite-formation ability tests confirmed that HA could not only more and faster induced the deposition of weak hydroxyapatite but also induced specific morphology of HA.

Improved osteogenic activity and inhibited bacterial biofilm formation on andrographolide-loaded titania nanotubes

Background

Delivery of local drugs with a titania nanotube is an attractive approach to combat implant-related infection. Our earlier study has confirmed that nanotubes loaded with gentamicin could significantly improve the antibacterial ability. On this basis, the used andrographolide in this paper has a high antibacterial activity, which cannot only avoid the evolution of antibiotic-resistant bacteria but also has simultaneously excellent biocompatibility with osteogenic cells.

Methods

Two mg of andrographolide was loaded into titania nanotubes, which were fabricated into different diameters (50 and 100 nm) and 200 nm length by the method of lyophilization and vacuum drying. We chose a standard strain, Staphylococcus epidermidis (American Type Culture Collection 35984), and two clinical isolates, S. aureus 376 and S. epidermidis 389 to research the bacterial adhesion at 6, 12 and 24 hours and biofilm formation at 48, and 72 hours on the andrographolide-loaded nanotubes (NT-A) using the diffusion plate method. Smooth titanium (smooth Ti) and nanotubes with no drug loading (NT) were also inclusive and analyzed. Furthermore, the Sprague-Dawley (SD) rats mesenchymal stem cells were used to assess the influence of nanotubular topographies on the osteogenic differentiation of mesenchymal stem cells.

Results

Our results showed that NT-A could inhibit bacterial adhesion and biofilm formation on implant surfaces. NT-A and NT, especially those with 100 nm diameters, were found to significantly promoted cell attachment, proliferation, diffusion, and osteogenic differentiation when compared with smooth Ti, while the same diameter in NT-A and NT did not differ.

Conclusions

Titania nanotube modification and andrographolide loading can significantly improve the antibacterial ability and osteogenic activity of orthopedic implants. Nanotubes-based local delivery could be a promising strategy for combating implant-associated infection.