Antibacterial activity and cytocompatibility of an implant coating consisting of TiO2 nanotubes combined with a GL13K antimicrobial peptide

Dhvar5-chitosan nanogels and their potential to improve antibiotics activity

Infection is one of the main causes of orthopedic implants failure, with antibiotic-resistant bacteria playing a crucial role in this outcome. In this work, antimicrobial nanogels were developed to be applied in situ as implant coating to prevent orthopedic-device-related infections. To that regard, a broad-spectrum antimicrobial peptide, Dhvar5, was grafted onto chitosan via thiol-norbornene "photoclick" chemistry. Dhvar5-chitosan nanogels (Dhvar5-NG) were then produced using a microfluidic system. Dhvar5-NG (1010 nanogels (NG)/mL) with a Dhvar5 concentration of 6 μg/mL reduced the burden of the most critical bacteria in orthopedic infections - methicillin-resistant Staphylococcus aureus (MRSA) - after 24 h in medium supplemented with human plasma proteins. Transmission electron microscopy showed that Dhvar5-NG killed bacteria by membrane disruption and cytoplasm release. No signs of cytotoxicity against a pre-osteoblast cell line were verified upon incubation with Dhvar5-NG. To further explore therapeutic alternatives, the potential synergistic effect of Dhvar5-NG with antibiotics was evaluated against MRSA. Dhvar5-NG at a sub-minimal inhibitory concentration (109 NG/mL) demonstrated synergistic effect with oxacillin (4-fold reduction: from 2 to 0.5 μg/mL) and piperacillin (2-fold reduction: from 2 to 1 μg/mL). This work supports the use of Dhvar5-NG as adjuvant of antibiotics to the prevention of orthopedic devices-related infections.

Interpenetrating nanofibrillar membrane of self-assembled collagen and antimicrobial peptides for enhanced bone regeneration

Bone regeneration remains a major clinical challenge, especially when infection necessitates prolonged antibiotic treatment. This study presents a membrane composed of self-assembled and interpenetrating GL13K, an antimicrobial peptide (AMP) derived from a salivary protein, in a collagen membrane for antimicrobial activity and enhanced bone regeneration. Commercially available collagen membranes were immersed in GL13K solution, and self-assembly was initiated by raising the solution pH to synthesize the multifunctional membrane called COL-GL. COL-GL was composed of interpenetrating large collagen fibers and short GL13K nanofibrils, which increased hydrophobicity, reduced biodegradation from collagenase, and stiffened the matrix compared to control collagen membranes. Incorporation of GL13K led to antimicrobial and anti-fouling activity against early oral surface colonizer Streptococcus gordonii while not affecting fibroblast cytocompatibility or pre-osteoblast osteogenic differentiation. GL13K in solution also reduced macrophage inflammatory cytokine expression and increased pro-healing cytokine expression. Bone formation in a rat calvarial model was accelerated at eight weeks with COL-GL compared to the gold-standard collagen membrane based on microcomputed tomography and histology. Interpenetration of GL13K within collagen sidesteps challenges with antimicrobial coatings on bone regeneration scaffolds while increasing bone regeneration. This strength makes COL-GL a promising approach to reduce post-surgical infections and aid bone regeneration in dental and orthopedic applications. STATEMENT OF SIGNIFICANCE: The COL-GL membrane, incorporating the antimicrobial peptide GL13K within a collagen membrane, signifies a noteworthy breakthrough in bone regeneration strategies for dental and orthopedic applications. By integrating self-assembled GL13K nanofibers into the membrane, this study successfully addresses the challenges associated with antimicrobial coatings, exhibiting improved antimicrobial and anti-fouling activity while preserving compatibility with fibroblasts and pre-osteoblasts. The accelerated bone formation observed in a rat calvarial model emphasizes the potential of this innovative approach to minimize post-surgical infections and enhance bone regeneration outcomes. As a promising alternative for future therapeutic interventions, this material tackles the clinical challenges of extended antibiotic treatments and antibiotic resistance in bone regeneration scenarios.

Tetrahedral framework nucleic acids/hyaluronic acid-methacrylic anhydride hybrid hydrogel with antimicrobial and anti-inflammatory properties for infected wound healing

Bacterial resistance and excessive inflammation are common issues that hinder wound healing. Antimicrobial peptides (AMPs) offer a promising and versatile antibacterial option compared to traditional antibiotics, with additional anti-inflammatory properties. However, the applications of AMPs are limited by their antimicrobial effects and stability against bacterial degradation. TFNAs are regarded as a promising drug delivery platform that could enhance the antibacterial properties and stability of nanodrugs. Therefore, in this study, a composite hydrogel (HAMA/t-GL13K) was prepared via the photocross-linking method, in which tFNAs carry GL13K. The hydrogel was injectable, biocompatible, and could be instantly photocured. It exhibited broad-spectrum antibacterial and anti-inflammatory properties by inhibiting the expression of inflammatory factors and scavenging ROS. Thereby, the hydrogel inhibited bacterial infection, shortened the wound healing time of skin defects in infected skin full-thickness defect wound models and reduced scarring. The constructed HAMA/tFNA-AMPs hydrogels exhibit the potential for clinical use in treating microbial infections and promoting wound healing.

Overview of strategies to improve the antibacterial property of dental implants

The increasing number of peri-implant diseases and the unsatisfactory results of conventional treatment are causing great concern to patients and medical staff. The effective removal of plaque which is one of the key causes of peri-implant disease from the surface of implants has become one of the main problems to be solved urgently in the field of peri-implant disease prevention and treatment. In recent years, with the advancement of materials science and pharmacology, a lot of research has been conducted to enhance the implant antimicrobial properties, including the addition of antimicrobial coatings on the implant surface, the adjustment of implant surface topography, and the development of new implant materials, and significant progress has been made in various aspects. Antimicrobial materials have shown promising applications in the prevention of peri-implant diseases, but meanwhile, there are some shortcomings, which leads to the lack of clinical widespread use of antimicrobial materials. This paper summarizes the research on antimicrobial materials applied to implants in recent years and presents an outlook on the future development.

Smart dental materials for antimicrobial applications

Smart biomaterials can sense and react to physiological or external environmental stimuli (e.g., mechanical, chemical, electrical, or magnetic signals). The last decades have seen exponential growth in the use and development of smart dental biomaterials for antimicrobial applications in dentistry. These biomaterial systems offer improved efficacy and controllable bio-functionalities to prevent infections and extend the longevity of dental devices. This review article presents the current state-of-the-art of design, evaluation, advantages, and limitations of bioactive and stimuli-responsive and autonomous dental materials for antimicrobial applications. First, the importance and classification of smart biomaterials are discussed. Second, the categories of bioresponsive antibacterial dental materials are systematically itemized based on different stimuli, including pH, enzymes, light, magnetic field, and vibrations. For each category, their antimicrobial mechanism, applications, and examples are discussed. Finally, we examined the limitations and obstacles required to develop clinically relevant applications of these appealing technologies.

Antimicrobial Peptides: Challenging Journey to the Pharmaceutical, Biomedical, and Cosmeceutical Use

Antimicrobial peptides (AMPs), or host defence peptides, are short proteins in various life forms. Here we discuss AMPs, which may become a promising substitute or adjuvant in pharmaceutical, biomedical, and cosmeceutical uses. Their pharmacological potential has been investigated intensively, especially as antibacterial and antifungal drugs and as promising antiviral and anticancer agents. AMPs exhibit many properties, and some of these have attracted the attention of the cosmetic industry. AMPs are being developed as novel antibiotics to combat multidrug-resistant pathogens and as potential treatments for various diseases, including cancer, inflammatory disorders, and viral infections. In biomedicine, AMPs are being developed as wound-healing agents because they promote cell growth and tissue repair. The immunomodulatory effects of AMPs could be helpful in the treatment of autoimmune diseases. In the cosmeceutical industry, AMPs are being investigated as potential ingredients in skincare products due to their antioxidant properties (anti-ageing effects) and antibacterial activity, which allows the killing of bacteria that contribute to acne and other skin conditions. The promising benefits of AMPs make them a thrilling area of research, and studies are underway to overcome obstacles and fully harness their therapeutic potential. This review presents the structure, mechanisms of action, possible applications, production methods, and market for AMPs.

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.

Antibacterial peptides-loaded bioactive materials for the treatment of bone infection

Bacterial bone infection in open fractures is an urgent problem to solve in orthopedics. Antimicrobial peptides (AMPs), as a part of innate immune defense, have good biocompatibility. Their antibacterial mechanism and therapeutic application against bacteria have been widely studied. Compared with traditional antibiotics, AMPs do not easily cause bacterial resistance and can be a reliable substitute for antibiotics in the future. Therefore, various physical and chemical strategies have been developed for the combined application of AMPs and bioactive materials to infected sites, which are conducive to maintaining the local stability of AMPs, reducing many complications, and facilitating bone infection resolution. This review explored the molecular structure, function, and direct and indirect antibacterial mechanisms of AMPs, introduced two important AMPs (LL-37 and β-defensins) in bone tissues, and reviewed advanced AMP loading strategies and different bioactive materials. Finally, the latest progress and future development of AMPs-loaded bioactive materials for the promotion of bone infection repair were discussed. This study provided a theoretical basis and application strategy for the treatment of bone infection with AMP-loaded bioactive materials.

Peptide–Polymer Conjugates: A Promising Therapeutic Solution for Drug-Resistant Bacteria

By 2050, it is estimated that 10 million people will die of drug-resistant bacterial infection caused by antibiotic abuse. Antimicrobial peptide (AMP) is widely used to prevent such circumstances, for the positively charged AMPs can kill drug-resistant bacteria by destroying negatively charged bacterial cell membrane, and has excellent antibacterial efficiency and low drug resistance. However, due to the defects in low in vivo stability, easy degradation, and certain cytotoxicity, its practical clinical application is limited. The emergence of peptide–polymer conjugates (PPC) helps AMPs overcome these shortcomings. By combining with functional polymers, the positive charge of AMPs is partially shielded, and its stability and water solubility are improved, so as to prolong the in vivo circulation time of AMPs and reduce its cytotoxicity. At the same time, the self-assembly ability of PPC enables it to assemble into different nanostructures to undertake specific antibacterial tasks. At present, PPC is mainly used in wound dressing, bone tissue repair, antibacterial coating of medical devices, nerve repair, tumor treatment, and oral health maintenance. In this study, we summarize the structure, synthesis methods, and the clinical applications of PPC, so as to present the current challenges and discuss the future prospects of antibacterial therapeutic materials.

Antibacterial Ti-Cu implants: A critical review on mechanisms of action

Titanium (Ti) has been widely used for manufacturing of bone implants because of its mechanical properties, biological compatibility, and favorable corrosion resistance in biological environments. However, Ti implants are prone to infection (peri-implantitis) by bacteria which in extreme cases necessitate painful and costly revision surgeries. An emerging, viable solution for this problem is to use copper (Cu) as an antibacterial agent in the alloying system of Ti. The addition of copper provides excellent antibacterial activities, but the underpinning mechanisms are still obscure. This review sheds light on such mechanisms and reviews how incorporation of Cu can render Ti–Cu implants with antibacterial activity. The review first discusses the fundamentals of interactions between bacteria and implanted surfaces followed by an overview of the most common engineering strategies utilized to endow an implant with antibacterial activity. The underlying mechanisms for antibacterial activity of Ti–Cu implants are then discussed in detail. Special attention is paid to contact killing mechanisms because the misinterpretation of this mechanism is the root of discrepancies in the literature.

Antimicrobial peptides for bone tissue engineering: Diversity, effects and applications

Bone tissue engineering has been becoming a promising strategy for surgical bone repair, but the risk of infection during trauma repair remains a problematic health concern worldwide, especially for fracture and infection-caused bone defects. Conventional antibiotics fail to effectively prevent or treat bone infections during bone defect repair because of drug-resistance and recurrence, so novel antibacterial agents with limited resistance are highly needed for bone tissue engineering. Antimicrobial peptides (AMPs) characterized by cationic, hydrophobic and amphipathic properties show great promise to be used as next-generation antibiotics which rarely induce resistance and show potent antibacterial efficacy. In this review, four common structures of AMPs (helix-based, sheet-based, coil-based and composite) and related modifications are presented to identify AMPs and design novel analogs. Then, potential effects of AMPs for bone infection during bone repair are explored, including bactericidal activity, anti-biofilm, immunomodulation and regenerative properties. Moreover, we present distinctive applications of AMPs for topical bone repair, which can be either used by delivery system (surface immobilization, nanoparticles and hydrogels) or used in gene therapy. Finally, future prospects and ongoing challenges are discussed.

Antibacterial properties of laser-encapsulated titanium oxide nanotubes decorated with nanosilver and covered with chitosan/Eudragit polymers

To provide antibacterial properties, the titanium samples were subjected to electrochemical oxidation in the fluoride-containing diethylene glycol-based electrolyte to create a titanium oxide nanotubular surface. Afterward, the surface was covered by sputtering with silver 5 nm film, and the tops of the nanotubes were capped using laser treatment, resulting in an appearance of silver nanoparticles (AgNPs) of around 30 nm in diameter on such a modified surface. To ensure a controlled release of the bactericidal substance, the samples were additionally coated with a pH-sensitive chitosan/Eudragit 100 coating, also exhibiting bactericidal properties. The modified titanium samples were characterized using SEM, EDS, AFM, Raman, and XPS techniques. The wettability, corrosion properties, adhesion of the coating to the substrate, the release of AgNPs into solutions simulating body fluids at different pH, and antibacterial properties were further investigated. The obtained composite coatings were hydrophilic, adjacent to the surface, and corrosion-resistant. An increase in the amount of silver released as ions or metallic particles into a simulated body fluid solution at acidic pH was observed for modified samples with the biopolymer coating after three days of exposure avoiding burst effect. The proposed modification was effective against both Gram-positive and Gram-negative bacteria.

The antimicrobial effect of doxycycline and doped ZnO in TiO2 nanotubes synthesized on the surface of orthodontic mini-implants

Objectives:

Anchorage preservation is crucial in orthodontic treatment success. Mini-implants make a revolution in this domain. The failure of orthodontic mini-implants due to inflammation and infection is one of the reasons for anchorage loss. The purpose of this study was to evaluate the effect of a novel mini-implant surface modification to improve resistance against microbial contamination and surrounding tissue inflammation.

Material and Methods:

Twenty-four orthodontic mini-implants (Jeil Medical Corporation, Korea) with 1.6 mm diameter and 8 mm length were randomly divided into three groups: Group 1: Control group, Group 2: Nanotubes were made on the surface with anodisation, and Group 3: Zinc Oxide (ZnO) doped into nanotubes, and then doxycycline is added to them. The anti-bacterial efficacy against Porphyromonas gingivalis was evaluated using the disk diffusion method. To analyze data, Kruskal–Wallis, Friedman, and Wilcoxon tests were done. The significance level was set at 0.05.

Results:

No zone of the inhibition was formed in Groups 1 and 2. In Group 3, the mean (SD) diameter of the inhibition zone in the first 5-day to sixth 5-day were 38.7(8.2), 25(4.8), 17.8(5.6), 7.63(5.37), 1.5(2.83), and 0 millimeters, respectively.

Conclusion:

Nanotubes containing doped ZnO and Doxycycline are capable of preventing bacterial growth around the mini implant surfaces for at least up to 30 days. To manage inflammation of surrounding tissues of mini-implants, nanotubes are not effective alone. Therefore, the presence of diffusible materials in addition to nanotubes on the surface of mini-implants is necessary.

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.

Polymeric Coatings and Antimicrobial Peptides as Efficient Systems for Treating Implantable Medical Devices Associated-Infections

Many infections are associated with the use of implantable medical devices. The excessive utilization of antibiotic treatment has resulted in the development of antimicrobial resistance. Consequently, scientists have recently focused on conceiving new ways for treating infections with a longer duration of action and minimum environmental toxicity. One approach in infection control is based on the development of antimicrobial coatings based on polymers and antimicrobial peptides, also termed as “natural antibiotics”.

Antimicrobial coating strategy to prevent orthopaedic device-related infections: recent advances and future perspectives

The rapid development of multidrug-resistant (MDR) bacteria and biofilm-related infections (BRIs) has urgently called for new strategies to combat severe orthopaedic device-related infections (ODRIs). Antimicrobial coating has emerged as a promising strategy in halting the incidence of ODRIs and treating ODRIs in long term. With the advancement of material science and biotechnology, numerous antimicrobial coatings have been reported in literature, showing superior antimicrobial and osteogenic functions. This review has specifically discussed the currently developed antimicrobial coatings in the perspective of drug release from the coating system, focusing on their realization of controlled and on demand antimicrobial agents release, as well as multi-functionality. Acknowledging the multidisciplinary nature of antimicrobial coating, the conceptual design, the deposition method and the therapeutic effect of the antimicrobial coatings have been described in detail and discussed critically. Particularly, the challenges and opportunities on the way toward the clinical translation of antimicrobial coatings have been highlighted.

In vitro behaviour of human gingival fibroblasts cultured on 3D-printed titanium alloy with hydrogenated TiO2 nanotubes

Selective laser melting (SLM), as one of the most common 3D-printed technologies, can form personalized implants, which after further surface modification can obtain excellent osseointegration. To study the surface properties of SLM titanium alloy (Ti6Al4V) with hydrogenated titanium dioxide (TiO₂)nanotubes (TNTs) and its influence on the biological behaviour of human gingival fibroblasts (HGFs), we used SLM to prepare 3D-printed titanium alloy samples (3D-Ti), which were electrochemically anodizing to fabricate 3D-TNTs and then further hydrogenated at high temperature to obtain 3D-H₂-TNTs. Polished cast titanium alloy (MP-Ti) was used as the control group. The surface morphology, hydrophilicity and roughness of MP-Ti, 3D-Ti, 3D-TNTs and 3D-H₂-TNTs were measured and analysed by scanning electron microscopy (SEM), contact angle metre, surface roughness measuring instrument and atomic force microscope, respectively. HGFs were cultured on the four groups of samples, and the cell morphology was observed by SEM. Fluorescence staining (DAPI) was used to observe the number of adhered cell nuclei, while a cell counting kit (CCK-8) was used to detect the early adhesion and proliferation of HGFs. Fluorescence quantitative real time polymerase chain reaction (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA) were used to detect the expression of adhesion-related genes and fibronectin (FN), respectively. The results of this in vitro comparison study indicated that electrochemical anodic oxidation and high-temperature hydrogenation can form a superhydrophilic micro-nano composite morphology on the surface of SLM titanium alloy, which can promote both the early adhesion and proliferation of human gingival fibroblasts and improve the expression of cell adhesion-related genes and fibronectin. Graphical abstract.

"Dual-functional" strontium titanate nanotubes designed based on fusion peptides simultaneously enhancing anti-infection and osseointegration

Currently, there is an increasing clinical demand for implants that effectively resist bacterial infections while promoting osseointegration. In this study, the fusion peptide technology was used to linearly fuse the antimicrobial peptide (AMP, HHC36) and the bone-promoting peptide (RGD), so that the titanium (Ti)-based implant modified by the polypeptide had the dual function of "antibacterial-promoting bone". Firstly, self-organized vertically-oriented strontium-doped titanium dioxide nanotubes (STN) were manufactured by anodizing and hydrothermal synthesis methods. Secondly, the fusion peptide (HHC36-RGD) was loaded into the tubular structure by a simple vacuum-assisted physical adsorption method. Finally, STN loaded with HHC36-RGD (H-R-STN) was obtained. The characterization results demonstrated that the surface of the H-R-STN had a roughness and hydrophilicity that promoted cell adhesion. Additionally, electrochemical tests showed that H-R-STN coating can reduce the corrosion rate of pure Ti. The fusion peptide and Sr²⁺ in H-R-STN were released in the initial fast and subsequent slow kinetic model. Expected, H-R-STN can kill more than 99% of clinically common pathogenic bacteria (Staphylococcus aureus and Escherichia coli), and significantly inhibit the formation of bacterial biofilms. Simultaneously, under the synergistic effect of RGD in the fusion peptide and strontium in STN, H-R-STN markedly promoted the adhesion and proliferation of mouse osteoblasts, and significantly promoted osteogenic markers (alkaline phosphatase, runt-related transcription, collagen, mineralization) expression. In summary, the bifunctional titanium-based implant constructed by H-R-STN in this article can effectively prevent bacterial infections and promote early osseointegration. The main advantage of the titanium surface treatment method of the study was that its simplicity, low cost, especially its versatility made it a promising anti-infective bone repair material.

Antimicrobial peptide-based materials: opportunities and challenges

The multifunctional properties of antimicrobial peptides (AMPs) make them attractive candidates for the treatment of various diseases. AMPs are considered alternatives to antibiotics due to the rising number of multidrug-resistant...

Application of Antimicrobial Peptides on Biomedical Implants: Three Ways to Pursue Peptide Coatings

Biofilm formation and inflammations are number one reasons of implant failure and cause a severe number of postoperative complications every year. To functionalize implant surfaces with antibiotic agents provides perspectives to minimize and/or prevent bacterial adhesion and proliferation. In recent years, antimicrobial peptides (AMP) have been evolved as promising alternatives to commonly used antibiotics, and have been seen as potent candidates for antimicrobial surface coatings. This review aims to summarize recent developments in this field and to highlight examples of the most common techniques used for preparing such AMP-based medical devices. We will report on three different ways to pursue peptide coatings, using either binding sequences (primary approach), linker layers (secondary approach), or loading in matrixes which offer a defined release (tertiary approach). All of them will be discussed in the light of current research in this area.

Martins MC, Costa F. Antimicrobial Peptides in the Battle against Orthopedic Implant-Related Infections: A Review

Prevention of orthopedic implant-related infections is a major medical challenge, particularly due to the involvement of biofilm-encased and multidrug-resistant bacteria. Current therapies, based on antibiotic administration, have proven to be insufficient, and infection prevalence may rise due to the dissemination of antibiotic resistance. Antimicrobial peptides (AMPs) have attracted attention as promising substitutes of conventional antibiotics, owing to their broad-spectrum of activity, high efficacy at very low concentrations, and, importantly, low propensity for inducing resistance. The aim of this review is to offer an updated perspective of the development of AMPs-based preventive strategies for orthopedic and dental implant-related infections. In this regard, two major research strategies are herein addressed, namely (i) AMP-releasing systems from titanium-modified surfaces and from bone cements or beads; and (ii) AMP immobilization strategies used to graft AMPs onto titanium or other model surfaces with potential translation as coatings. In overview, releasing strategies have evolved to guarantee higher loadings, prolonged and targeted delivery periods upon infection. In addition, avant-garde self-assembling strategies or polymer brushes allowed higher immobilized peptide surface densities, overcoming bioavailability issues. Future research efforts should focus on the regulatory demands for pre-clinical and clinical validation towards clinical translation.

The prospects of antimicrobial coated medical implants

The implants are increasingly being a part of modern medicine in various surgical procedures for functional or cosmetic purposes. The progressive use of implants is associated with increased infectious complications and prevention of such infections always remains precedence in the clinical settings. The preventive approaches include the systemic administration of antimicrobial agents before and after the surgical procedures as well as the local application of antibiotics. The relevant literature and existing clinical practices have highlighted the role of antimicrobial coating approaches in the prevention of implants associated infections, although the applications of these strategies are not yet standardized, and the clinical efficacy is not much clear. The adequate data from the randomized control trials is challenging because of the unavailability of a large sample size although it is compulsory in this context to assess the clinical efficacy of preemptive practices. This review compares the efficacy of preventive approaches and the prospects of antimicrobial-coated implants in preventing implant-related infections.

A Novel Surface Modification Strategy via Photopolymerized Poly-Sulfobetaine Methacrylate Coating to Prevent Bacterial Adhesion on Titanium Surfaces

Recent investigations on the anti-adhesive properties of polysulfobetaine methacrylate (pSBMA) coatings had shown promising potential as antifouling surfaces and have given the impetus for the present paper, where a pSBMA coating is applied via photopolymerization on a macro-roughened, sandblasted, and acid-etched titanium implant surface in order to assess its antifouling properties. Current emphasis is placed on how the coating is efficient against the adhesion of Enterococcus faecalis by quantitative assessment of colony forming units and qualitative investigation of fluorescence imaging and scanning electron microscopy. pSBMA coatings via photopolymerization of titanium surfaces seems to be a promising antiadhesion strategy, which should bring substantial benefits once certain aspects such as biodegradation and osseointegration were addressed. Additionally, commercial SAL-titanium substrates may be coated with the super-hydrophilic coating, appearing resistant to physiological salt concentrations and most importantly lowering E. faecalis colonization significantly, compared to titanium substrates in the as-received state. It is very likely that pSBMA coatings may also prevent the adhesion of other germs.

Visible light-induced antibacterial and osteogenic cell proliferation properties of hydrogenated TiO2 nanotubes/Ti foil composite

We successfully fabricated the hydrogenated TiO₂ nanotubes/Ti foil (H-TNTs/f-Ti) composite via one-step anodization and two-step annealing. H-TNTs/f-Ti composite had a higher visible light-induced photoelectric response and more hydroxyl functional groups compared with Ti foil and unmodified TiO₂ nanotubes/Ti foil composite, which contributed to limiting the proliferation of Streptococcus mutans and Porphyromonas gingivalis, promoting the proliferation of MC3T3-E1 cell on the hydroxylated surface, and improving the biocompatibility with osteogenic cells. Our study provides a simple and effective method for significantly improving dental implant efficacy.

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.

Tetrahedral DNA nanostructure improves transport efficiency and anti-fungal effect of histatin 5 against Candida albicans

OBJECTIVES

Anti-microbial peptides (AMPs) have been comprehensively investigated as a novel alternative to traditional antibiotics against microorganisms. Meanwhile, Tetrahedral DNA nanostructures (TDNs) have gained attention in the field of biomedicine for their premium biological effects and transportation efficiency as delivery vehicles. Hence, in this study, TDN/Histatin 5 (His-5) was synthesized and the transport efficiency and anti-fungal effect were measured to evaluate the promotion of His-5 modified by TDNs.

MATERIALS AND METHODS

Tetrahedral DNA nanostructures/His-5 complex was prepared via electrostatic attraction and characterized by transmission electron microscopy (TEM), polyacrylamide gel electrophoresis (PAGE), dynamic light scattering (DLS) and electrophoretic light scattering (ELS). The anti-fungal effect of the TDN/His-5 complex was evaluated by determining the growth curve and colony-forming units of C. albicans. The morphological transformation of C. albicans was observed by light microscope and scanning electron microscope (SEM). Immunofluorescence was performed, and potassium efflux was detected to mechanistically demonstrate the efficacy of TDN/His-5.

RESULTS

The results showed that Histatin 5 modified by TDNs had preferable stability in serum and was effectively transported into C. albicans, leading to the increased formation of intracellular reactive oxygen species, higher potassium efflux and enhanced anti-fungal effect against C. albicans.

CONCLUSIONS

Our study showed that TDN/His-5 was synthesized successfully. And by the modification of TDNs, His-5 showed increased transport efficiency and improved anti-fungal effect.

Metallic-nanoparticle release systems for biomedical implant surfaces: effectiveness and safety

The current focus of bioengineering for implant devices involves the development of functionalized surfaces, bioactive coatings, and metallic nanoparticles (mNPs) with a controlled release, together with strategies for the application of drugs in situ, aiming at reducing infection rates, with an improvement of clinical outcomes. Controversially, negative aspects, such as cytotoxicity, mNP incorporation, bioaccumulation, acquired autoimmunity, and systemic toxicity have gained attention at the same status of importance, concerning the release of mNPs from these surface systems. The balance between the promising prospects of system releasing mNPs and the undesirable long-term adverse reactions require further investigation. The scarcity of knowledge and the methods of analysis of nanoscale-based systems to control the sequence of migration, interaction, and nanoparticle incorporation with human tissues raise hesitation about their efficacy and safety. Looking ahead, this innovative approach requires additional scientific investigation for permitting an evolution of implants without counterpoints, while updating implant surface technologies to a new level of development. This critical review has explored the promising properties of metals at the nano-scale to promote broad-spectrum bacterial control, allowing for a decrease in using systemic antibiotics. Attempts have also been made to discuss the existing limitations and the future challenges regarding these technologies, besides the negative findings that are explored in the literature.

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

BACKGROUND

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

PURPOSE AND SCOPE

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

SUMMARY

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

CONCLUSION

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

Orchestrating soft tissue integration at the transmucosal region of titanium implants

Osseointegration at the bone-implant interface and soft tissue integration (STI) at the trans-mucosal region are crucial for the long-term success of dental implants, especially in compromised patient conditions. The STI quality of conventional smooth and bio-inert titanium-based implants is inferior to that of natural tissue (i.e. teeth), and hence various surface modifications have been suggested. This review article compares and contrasts the various modification strategies (physical, chemical and biological) utilized to enhance STI of Ti implants. It also details the STI challenges associated with conventional Ti-based implants, current surface modification strategies and cutting-edge nano-engineering solutions. The topographical, biological and therapeutic advances achievable via electrochemically anodized Ti implants with TiO₂ nanotubes/nanopores are highlighted. Finally, the status and future directions of such nano-engineered implants is discussed, with emphasis on bridging the gap between research and clinical translation.

Overview of Antibacterial Strategies of Dental Implant Materials for the Prevention of Peri-Implantitis

As dental implants have become one of the main treatment options for patients with tooth loss, the number of patients with peri-implant diseases has increased. Similar to periodontal diseases, peri-implant diseases have been associated with dental plaque formation on implants. Unconventional approaches have been reported to remove plaque from infected implants, but none of these methods can completely and permanently solve the problem of bacterial invasion. Fortunately, the constant development of antibacterial implant materials is a promising solution to this situation. In this review, the development and study of different antibacterial strategies for dental implant materials for the prevention of peri-implantitis are summarized. We hope that by highlighting the advantages and limitations of these antimicrobial strategies, we can assist in the continued development of oral implant materials.

Osseointegration and antibacterial effect of an antimicrobial peptide releasing mesoporous titania implant

Medical devices such as orthopedic and dental implants may get infected by bacteria, which results in treatment using antibiotics. Since antibiotic resistance is increasing in society there is a need of finding alternative strategies for infection control. One potential strategy is the use of antimicrobial peptides, AMPs. In this study, we investigated the antibiofilm effect of the AMP, RRP9W4N, using a local drug-delivery system based on mesoporous titania covered titanium implants. Biofilm formation was studied in vitro using a safranine biofilm assay and LIVE/DEAD staining. Moreover, we investigated what effect the AMP had on osseointegration of commercially available titanium implants in vivo, using a rabbit tibia model. The results showed a sustained release of AMP with equal or even better antibiofilm properties than the traditionally used antibiotic Cloxacillin. In addition, no negative effects on osseointegration in vivo was observed. These combined results demonstrate the potential of using mesoporous titania as an AMP delivery system and the potential use of the AMP RRP9W4N for infection control of osseointegrating implants.

Biomimetic mineralized hybrid scaffolds with antimicrobial peptides

Infection in hard tissue regeneration is a clinically-relevant challenge. Development of scaffolds with dual function for promoting bone/dental tissue growth and preventing bacterial infections is a critical need in the field. Here we fabricated hybrid scaffolds by intrafibrillar-mineralization of collagen using a biomimetic process and subsequently coating the scaffold with an antimicrobial designer peptide with cationic and amphipathic properties. The highly hydrophilic mineralized collagen scaffolds provided an ideal substrate to form a dense and stable coating of the antimicrobial peptides. The amount of hydroxyapatite in the mineralized fibers modulated the rheological behavior of the scaffolds with no influence on the amount of recruited peptides and the resulting increase in hydrophobicity. The developed scaffolds were potent by contact killing of Gram-negative Escherichia coli and Gram-positive Streptococcus gordonii as well as cytocompatible to human bone marrow-derived mesenchymal stromal cells. The process of scaffold fabrication is versatile and can be used to control mineral load and/or intrafibrillar-mineralized scaffolds made of other biopolymers.

•

A biomimetic intrafibrillar-mineralized scaffold was prepared using a non-classical pathway for mineralization.

•

The mineralized scaffold was stably coated with designer antimicrobial peptide GL13K.

•

The hybrid scaffold was cytocompatible and potent against biofilms of model Gram-positive and Gram-negative bacteria.

•

The mineral content affected the rheological properties of the scaffolds, but not the loading of antimicrobial peptides.

Ways to control harmful biofilms: prevention, inhibition, and eradication

Biofilms are complex microbial architectures that encase microbial cells in a matrix comprising self-produced extracellular polymeric substances. Microorganisms living in biofilms are much more resistant to hostile environments than their planktonic counterparts and exhibit enhanced resistance against the microbicides. From the human perspective, biofilms can be classified into beneficial, neutral, and harmful. Harmful biofilms impact food safety, cause plant and animal diseases, and threaten medical fields, making it urgent to develop effective and robust strategies to control harmful biofilms. In this review, we discuss various strategies to control biofilm formation on infected tissues, implants, and medical devices. We classify the current strategies into three main categories: (i) changing the properties of susceptible surfaces to prevent biofilm formation; (ii) regulating signalling pathways to inhibit biofilm formation; (iii) applying external forces to eradicate the biofilm. We hope this review would motivate the development of innovative and effective strategies for controlling harmful biofilms.

Impacts of a Nano-Laponite Ceramic on Surface Performance, Apatite Mineralization, Cell Response, and Osseointegration of a Polyimide-Based Biocomposite

INTRODUCTION

Polyimide (PI) exhibits good biocompatibility and high mechanical strength, but biological inertness that does not stimulate bone regeneration, while laponite possesses excellent bioactivity.

METHODS

In this study, to improve the bioactivity of PI, nano-laponite ceramic (LC)-PI composites (LPCs) were fabricated by melt processing as implantable materials for bone repair.

RESULTS

The compressive strength, hydrophilicity, and surface roughness of LPCs with 40 w% LC content (LPC40s) were higher than LPC20s, and LPC20s higher than pure PI. In addition, no apatite mineralization occurred on PI, while apatite mineralized on LPCs in simulated body fluid. Compared with LPC20, more apatite deposited on LPC40, indicating good bioactivity. Moreover, the adhesion, proliferation, and alkaline phosphatase activity of rat bone mesenchymal stem cells on LPCs significantly increased with LC content increasing in vitro. Furthermore, the evaluations of animal experiments (micro-CT, histology, and pushout load) revealed that compared with LPC20 and PI, LPC40 significantly enhanced osteogenesis and osseointegration in vivo.

DISCUSSION

Incorporation of LC into PI obviously improved not only surface physicochemical properties but also biological properties of LPCs. LPC40 with high LC content displayed good biocompatibility and bioactivity, which markedly promoted osteogenesis and osseointegration. Therefore, with its superior biocompatibility and bioactivity, LPC40 could be an alternative candidate as an implant for orthopedic applications.

Antimicrobial peptides - Advances in development of therapeutic applications

The severe infection is becoming a significant health problem which threaten the lives of patients and the safety and economy of society. In the way of finding new strategy, antimicrobial peptides (AMPs) - an important part of host defense family, emerged with tremendous potential. Up to date, huge numbers of AMPs has been investigated from both natural and synthetic sources showing not only the ability to kill microbial pathogens but also propose other benefits such as wound healing, anti-tumor, immune modulation. In this review, we describe the involvements of AMPs in biological systems and discuss the opportunity in developing AMPs for clinical applications. In the detail, their properties in antibacterial activity is followed by their application in some infection diseases and cancer. The key discussions are the approaches to improve biological activities of AMPs either by modifying chemical structure or incorporating into delivery systems. The new applications and perspectives for the future of AMPs would open the new era of their development.

Strategies for antimicrobial peptide coatings on medical devices: a review and regulatory science perspective

Indwelling and implanted medical devices are subject to contamination by microbial pathogens during surgery, insertion or injection, and ongoing use, often resulting in severe nosocomial infections. Antimicrobial peptides (AMPs) offer a promising alternative to conventional antibiotics to reduce the incidence of such infections, as they exhibit broad-spectrum antimicrobial activity against Gram-negative and Gram-positive bacteria, microbial biofilms, fungi, and viruses. In this review-perspective, we first provide an overview of the progress made in this field over the past decade with an emphasis on the local release of AMPs from implant surfaces and immobilization strategies for incorporating these agents into a wide range of medical device materials. We then provide a regulatory science perspective addressing the characterization and testing of AMP coatings based on the type of immobilization strategy used with a focus on the US market regulatory niche. Our goal is to help narrow the gulf between academic studies and preclinical testing, as well as to support a future literature base in order to develop the regulatory science of antimicrobial coatings.

Nanomaterials in Dentistry: State of the Art and Future Challenges

Nanomaterials are commonly considered as those materials in which the shape and molecular composition at a nanometer scale can be controlled. Subsequently, they present extraordinary properties that are being useful for the development of new and improved applications in many fields, including medicine. In dentistry, several research efforts are being conducted, especially during the last decade, for the improvement of the properties of materials used in dentistry. The objective of the present article is to offer the audience a complete and comprehensive review of the main applications that have been developed in dentistry, by the use of these materials, during the last two decades. It was shown how these materials are improving the treatments in mainly all the important areas of dentistry, such as endodontics, periodontics, implants, tissue engineering and restorative dentistry. The scope of the present review is, subsequently, to revise the main applications regarding nano-shaped materials in dentistry, including nanorods, nanofibers, nanotubes, nanospheres/nanoparticles, and zeolites and other orders porous materials. The results of the bibliographic analysis show that the most explored nanomaterials in dentistry are graphene and carbon nanotubes, and their derivatives. A detailed analysis and a comparative study of their applications show that, although they are quite similar, graphene-based materials seem to be more promising for most of the applications of interest in dentistry. The bibliographic study also demonstrated the potential of zeolite-based materials, although the low number of studies on their applications shows that they have not been totally explored, as well as other porous nanomaterials that have found important applications in medicine, such as metal organic frameworks, have not been explored. Subsequently, it is expected that the research effort will concentrate on graphene and zeolite-based materials in the coming years. Thus, the present review paper presents a detailed bibliographic study, with more than 200 references, in order to briefly describe the main achievements that have been described in dentistry using nanomaterials, compare and analyze them in a critical way, with the aim of predicting the future challenges.

Customized Therapeutic Surface Coatings for Dental Implants

Dental implants are frequently used to support fixed or removable dental prostheses to replace missing teeth. The clinical success of titanium dental implants is owed to the exceptional biocompatibility and osseointegration with the bone. Therefore, the enhanced therapeutic effectiveness of dental implants had always been preferred. Several concepts for implant coating and local drug delivery had been developed during the last decades. A drug is generally released by diffusion-controlled, solvent-controlled, and chemical controlled methods. Although a range of surface modifications and coatings (antimicrobial, bioactive, therapeutic drugs) have been explored for dental implants, it is still a long way from designing sophisticated therapeutic implant surfaces to achieve the specific needs of dental patients. The present article reviews various interdisciplinary aspects of surface coatings on dental implants from the perspectives of biomaterials, coatings, drug release, and related therapeutic effects. Additionally, the various types of implant coatings, localized drug release from coatings, and how released agents influence the bone–implant surface interface characteristics are discussed. This paper also highlights several strategies for local drug delivery and their limitations in dental implant coatings as some of these concepts are yet to be applied in clinical settings due to the specific requirements of individual patients.

Enhanced antibacterial properties of orthopedic implants by titanium nanotube surface modification: a review of current techniques

Prosthesis-associated infections are one of the main causes of implant failure; thus it is important to enhance the long-term antibacterial ability of orthopedic implants. Titanium dioxide nanotubes (TNTs) are biomaterials with good physicochemical properties and biocompatibility. Owing to their inherent antibacterial and drug-loading ability, the antibacterial application of TNTs has received increasing attention. In this review, the process of TNT anodizing fabrication is summarized. Also, the mechanism and the influencing factors of the antibacterial property of bare TNTs are explored. Furthermore, different antibacterial strategies for carrying drugs, as well as modifications to prolong the antibacterial effect and reduce drug-related toxicity are discussed. In addition, antibacterial systems based on TNTs that can automatically respond to infection are introduced. Finally, the currently faced problems are reviewed and potential solutions are proposed. This review provides new insight on TNT fabrication and summarizes the most advanced antibacterial strategies involving TNTs for the enhancement of long-term antibacterial ability and reduction of toxicity.

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.

Surface treatment strategies to combat implant-related infection from the beginning

Orthopaedic implants are recognised as important therapeutic devices in the successful clinical management of a wide range of orthopaedic conditions. However, implant-related infections remain a challenging and not uncommon issue in patients with implanted instrumentation or medical devices. Bacterial adhesion and formation of biofilm on the surface of the implant represent important processes towards progression of infection. Given the intimate association between infection and the implant surface, adequate treatment of the implant surface may help mitigate the risk of infection. This review summarises the current surface treatment technologies and their role in prevention of implant-related infection from the beginning.

Translational potential of this article

Despite great technological advancements, the prevalence of implant-related infections remains high. Four main challenges can be identified. (i) Insufficient mechanical stability can cause detachment of the implant surface coating, altering the antimicrobial ability of functionalized surfaces. (ii) Regarding drug-loaded coatings, a stable drug release profile is of vital importance for achieving effective bactericidal effect locally; however, burst release of the loaded antibacterial agents remains common. (iii) Although many coatings and modified surfaces provide superior antibacterial action, such functionalisation of surfaces sometimes has a detrimental effect on tissue biocompatibility, impairing the integration of the implants into the surrounding tissue. (iv) Biofilm eradication at the implant surface remains particularly challenging. This review summarised the recent progress made to address the aforementioned problems. By providing a perspective on state-of-the-art surface treatment strategies for medical implants, we hope to support the timely adoption of modern materials and techniques into clinical practice.

Antibiofilm Peptides and Peptidomimetics with Focus on Surface Immobilization

Bacterial biofilms pose a major threat to public health, as they are associated with at least two thirds of all infections. They are highly resilient and render conventional antibiotics inefficient. As a part of the innate immune system, antimicrobial peptides have drawn attention within the last decades, as some of them are able to eradicate biofilms at sub-minimum inhibitory concentration (MIC) levels. However, peptides possess a number of disadvantages, such as susceptibility to proteolytic degradation, pH and/or salinity-dependent activity and loss of activity due to binding to serum proteins. Hence, proteolytically stable peptidomimetics were designed to overcome these drawbacks. This paper summarizes the current peptide and peptidomimetic strategies for combating bacteria-associated biofilm infections, both in respect to soluble and surface-functionalized solutions.

Effects of hydrogenated TiO2 nanotube arrays on protein adsorption and compatibility with osteoblast-like cells

Background

Modified titanium (Ti) substrates with titanium dioxide (TiO₂) nanotubes have broad usage as implant surface treatments and as drug delivery systems.

Methods

To improve drug-loading capacity and accelerate bone integration with titanium, in this study, we hydrogenated anodized titanium dioxide nanotubes (TNTs) by a thermal treatment. Three groups were examined, namely: hydrogenated TNTs (H₂-TNTs, test), unmodified TNTs (air-TNTs, control), and Ti substrates (Ti, control).

Results

Our results showed that oxygen vacancies were present in all the nanotubes. The quantity of -OH groups greatly increased after hydrogenation. Furthermore, the protein adsorption and loading capacity of the H₂-TNTs were considerably enhanced as compared with the properties of the air-TNTs (P<0.05). Additionally, time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used to investigate the interactions of TNTs with proteins. During the protein-loading process, the H₂-TNTs not only enabled rapid protein adsorption, but also decreased the rate of protein elution compared with that of the air-TNTs. We found that the H₂-TNTs exhibited better biocompatibility than the air-TNT and Ti groups. Both cell adhesion activity and alkaline phosphatase activity were significantly improved toward MG-63 human osteoblast-like cells as compared with the control groups (P<0.05).

Conclusion

We conclude that hydrogenated TNTs could greatly improve the loading capacity of bioactive molecules and MG-63 cell proliferation.