Inhibited bacterial biofilm formation and improved osteogenic activity on gentamicin-loaded titania nanotubes with various diameters

Insight into antibacterial effect of titanium nanotubular surfaces with focus on Staphylococcus aureus and Pseudomonas aeruginosa

Materials used for orthopedic implants should not only have physical properties close to those of bones, durability and biocompatibility, but should also exhibit a sufficient degree of antibacterial functionality. Due to its excellent properties, titanium is still a widely used material for production of orthopedic implants, but the unmodified material exhibits poor antibacterial activity. In this work, the physicochemical characteristics, such as chemical composition, crystallinity, wettability, roughness, and release of Ti ions of the titanium surface modified with nanotubular layers were analyzed and its antibacterial activity against two biofilm-forming bacterial strains responsible for prosthetic joint infection (Staphylococcus aureus and Pseudomonas aeruginosa) was investigated. Electrochemical anodization (anodic oxidation) was used to prepare two types of nanotubular arrays with nanotubes differing in dimensions (with diameters of 73 and 118 nm and lengths of 572 and 343 nm, respectively). These two surface types showed similar chemistry, crystallinity, and surface energy. The surface with smaller nanotube diameter (TNT-73) but larger values of roughness parameters was more effective against S. aureus. For P. aeruginosa the sample with a larger nanotube diameter (TNT-118) had better antibacterial effect with proven cell lysis. Antibacterial properties of titanium nanotubular surfaces with potential in implantology, which in our previous work demonstrated a positive effect on the behavior of human gingival fibroblasts, were investigated in terms of surface parameters. The interplay between nanotube diameter and roughness appeared critical for the bacterial fate on nanotubular surfaces. The relationship of nanotube diameter, values of roughness parameters, and other surface properties to bacterial behavior is discussed in detail. The study is believed to shed more light on how nanotubular surface parameters and their interplay affect antibacterial activity.

Evaluation of bioactivity and antibacterial properties of Ti6Al4V-based green biocomposite implant encompassing TiO2 nanotube arrays and garlic extract

This study involved the incorporation of an antibacterial garlic extract into titanium oxide nanotubes (TNTs) formed via the anodization of Ti6Al4V implants. The garlic extract, obtained through low-temperature extraction aided by ultrasound waves, was loaded into the nanotubes. The presence of the nanotubes was confirmed through X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and scanning electron microscopy (SEM). Fourier-transform infrared spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC-MS) were used to investigate the presence of bioactive compounds, particularly sulfur compounds responsible for garlic's antibacterial effects. The impact of loading two concentrations (0.1 and 0.2 g per milliliter) of garlic extract on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria was examined. Results indicated a decrease in the growth range of S. aureus from 109 to 106 (CFU/ml) and E. coli from 1011 to 109 (CFU/ml) upon treatment. Additionally, cell adhesion and viability tests conducted on MG63 cells revealed an 8% increase in cell viability with the 0.1 g per milliliter concentration and a 35% decrease with the 0.2 g per milliliter concentration of garlic extract after 72 h of incubation (They have been evaluated by Microculture tetrazolium (MTT) assay). GC-MS analysis identified the presence of diethyl phthalate compounds in the garlic extract, suggesting a potential correlation with cellular toxicity observed in the sample with the higher concentration (0.2 g per milliliter) of garlic extract. Overall, the TNTs loaded with 0.1 g per milliliter of garlic extract simultaneously demonstrated antibacterial activity, cell viability, adhesion, and growth enhancement.

Antimicrobial behavior of nanocoated orthodontic micro-implants: An in vitro study

OBJECTIVE

The need to overcome the failure of orthodontic micro-implants which might reach to 30% has led to the development of different methods, one of which is nanoparticle deposition.

AIM OF STUDY

To evaluate the anti-microbial efficiency of TiO2 and ZnO nanoparticles (NP) when used as a coating for orthodontic micro-implants.

METHODS

Thirty titanium alloy micro-implants were used in the presented study. They were divided into three groups according to the coating method and the coating materials used: the control group without surface coating; the titanium dioxide (TiO2)-coated group, in which direct current (DC) spattering was used to coat the micro-implants with a TiO2 layer; and the TiO2 and zinc oxide (TiO2ZnO)-coated group, in which the micro-implants were coated with a TiO2 layer via direct current (DC) spattering and a zinc oxide (ZnO) layer via laser vacuum. The micro-implant surfaces were characterized using scanning electron microscopy (SEM) and an energy-dispersive spectrometer (EDS). The antibacterial susceptibility was assessed using gram-positive and gram-negative bacteria.

RESULTS

SEM and EDS tests confirmed the coating of the micro-implants in the TiO2- and TiO2ZnO-coated groups. The micro-implants in the TiO2- and TiO2ZnO-coated groups demonstrated higher antibacterial ability than the control group.

CONCLUSION

This study demonstrated the significance of improving the surface of orthodontic micro-implants by coating them with TiO2 and ZnO nanoparticles to improve osseointegration and prevent biofilm formation.

Gentamicin Eluting 3D-Printed Implants for Preventing Post-Surgical Infections in Bone Fractures

A surgically implantable device is an inevitable treatment option for millions of people worldwide suffering from diseases arising from orthopedic injuries. A global paradigm shift is currently underway to tailor and personalize replacement or reconstructive joints. Additive manufacturing (AM) has provided dynamic outflow to the customized fabrication of orthopedic implants by enabling need-based design and surface modification possibilities. Surgical grade 316L Stainless Steel (316L SS) is promising with its cost, strength, composition, and corrosion resistance to fabricate 3D implants. This work investigates the possibilities of application of the laser powder bed fusion (L-PBF) technique to fabricate 3D-printed (3DP) implants, which are functionalized with a multilayered antimicrobial coating to treat potential complications arising due to postsurgical infections (PSIs). Postsurgical implant-associated infection is a primary reason for implantation failure and is complicated mainly by bacterial colonization and biofilm formation at the installation site. PLGA (poly-d,l-lactide-co-glycolide), a biodegradable polymer, was utilized to impart multiple layers of coating using the airbrush spray technique on 3DP implant surfaces loaded with gentamicin (GEN). Various PLGA-based polymers were tested to optimize the ideal lactic acid: glycolic acid ratio and molecular weight suited for our investigation. 3D-Printed PLGA-GEN substrates sustained the release of gentamicin from the surface for approximately 6 weeks. The 3DP surface modification with PLGA-GEN facilitated cell adhesion and proliferation compared to control surfaces. The cell viability studies showed that the implants were safe for application. The 3DP PLGA-GEN substrates showed good concentration-dependent antibacterial efficacy against the common PSI pathogen Staphylococcus aureus (S. aureus) and Staphylococcus epidermidis (S. epidermidis). The GEN-loaded substrates demonstrated antimicrobial longevity and showed significant biofilm growth inhibition compared to control. The substrates offered great versatility regarding the in vitro release rates, antimicrobial properties, and biocompatibility studies. These results radiate great potential in future human and veterinary clinical applications pertinent to complications arising from PSIs, focusing on personalized sustained antibiotic delivery.

Development of Silver-Containing Hydroxyapatite-Coated Antimicrobial Implants for Orthopaedic and Spinal Surgery

The prevention of surgical site infections is directly related to the minimization of surgical invasiveness, and is in line with the concept of minimally invasive spine therapy (MIST). In recent years, the incidence of postoperative infections has been increasing due to the increased use of spinal implant surgery in patients at high risk of infection, including the elderly and easily infected hosts, the limitations of poor bone marrow transfer of antibiotics, and the potential for contamination of surgical gloves and instruments. Thus, the development of antimicrobial implants in orthopedic and spinal surgery is becoming more and more popular, and implants with proven antimicrobial, safety, and osteoconductive properties (i.e., silver, iodine, antibiotics) in vitro, in vivo, and in clinical trials have become available for clinical use. We have developed silver-containing hydroxyapatite (Ag-HA)-coated implants to prevent post-operative infection, and increase bone fusion capacity, and have successfully commercialized antibacterial implants for hip prostheses and spinal interbody cages. This narrative review overviews the present status of available surface coating technologies and materials; describes how the antimicrobial, safety, and biocompatibility (osteoconductivity) of Ag-HA-coated implants have been demonstrated for commercialization; and reviews the clinical use of antimicrobial implants in orthopedic and spinal surgery, including Ag-HA-coated implants that we have developed.

Engineered titania nanomaterials in advanced clinical applications

Significant advancement in the field of nanotechnology has raised the possibility of applying potent engineered biocompatible nanomaterials within biological systems for theranostic purposes. Titanium dioxide (titanium(IV) oxide/titania/TiO2) has garnered considerable attention as one of the most extensively studied metal oxides in clinical applications. Owing to the unique properties of titania, such as photocatalytic activity, excellent biocompatibility, corrosion resistance, and low toxicity, titania nanomaterials have revolutionized therapeutic approaches. Additionally, titania provides an exceptional choice for developing innovative medical devices and the integration of functional moieties that can modulate the biological responses. Thus, the current review aims to present a comprehensive and up-to-date overview of TiO2-based nanotherapeutics and the corresponding future challenges.

Classification and research progress of implant surface antimicrobial techniques

Due to the good biocompatibility and ideal mechanical property, titanium implants have been widely used in dental clinic and orthopedic surgery. However, bacteria induced infection can cause per-implant inflammation and decrease the success rate of implant surgery. Therefore, developing antimicrobial techniques is essential to successful application of titanium implants. Many surface antimicrobial techniques, including antimicrobial coating and surface modifications, have been explored and they always exert antimicrobial effect by reducing bacterial adhesion, inhibiting their metabolism, or destructing cell structure. In this paper, different surface antimicrobial techniques and their recent research progress are reviewed to provide a brief insight on this area.

Antibiotics- and Heavy Metals-Based Titanium Alloy Surface Modifications for Local Prosthetic Joint Infections

Prosthetic joint infection (PJI) is the second most common cause of arthroplasty failure. Though infrequent, it is one of the most devastating complications since it is associated with great personal cost for the patient and a high economic burden for health systems. Due to the high number of patients that will eventually receive a prosthesis, PJI incidence is increasing exponentially. As these infections are provoked by microorganisms, mainly bacteria, and as such can develop a biofilm, which is in turn resistant to both antibiotics and the immune system, prevention is the ideal approach. However, conventional preventative strategies seem to have reached their limit. Novel prevention strategies fall within two broad categories: (1) antibiotic- and (2) heavy metal-based surface modifications of titanium alloy prostheses. This review examines research on the most relevant titanium alloy surface modifications that use antibiotics to locally prevent primary PJI.

Gentamicin-Releasing Titania Nanotube Surfaces Inhibit Bacteria and Support Adipose-Derived Stem Cell Growth in Cocultures

Infection is the second leading cause of failure of orthopedic implants following incomplete osseointegration. Materials that increase the antimicrobial properties of surfaces while maintaining the ability for bone cells to attach and proliferate could reduce the failure rates of orthopedic implants. In this study, titania nanotubes (Nts) were modified with chitosan/heparin polyelectrolyte multilayers (PEMs) for gentamicin delivery. The antimicrobial activity of the surfaces was tested by coculturing bacteria with mammalian cells. Over 60% of gentamicin remained on the surface after an initial burst release on the first day. Antimicrobial activity of these surfaces was determined by exposure to Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) for up to 24 h. Gentamicin surfaces had less live E. coli and S. aureus by 6 h and less E. coli by 24 h compared to Nt surfaces. S. aureus and human adipose-derived stem cells (hADSCs) were cocultured on surfaces for up to 7 days to characterize the so-called "race to the surface" between bacteria and mammalian cells, which is hypothesized to ultimately determine the outcome of orthopedic implants. By day 7, there was no significant difference in bacteria between surfaces with gentamicin adsorbed on the surface and surfaces with gentamicin in solution. However, gentamicin delivered in solution is toxic to hADSCs. Alternatively, gentamicin presented from PEMs enhances the antimicrobial properties of the surfaces without inhibiting hADSC attachment and cell growth. Delivering gentamicin from the surfaces is therefore superior to delivering gentamicin in solution and represents a strategy that could improve the antimicrobial activity of orthopedic implants and reduce risk of failure due to infection, without reducing mammalian cell attachment.

Novel Strategies to Combat Bacterial Biofilms

Biofilms are considered as a severe problem in the treatment of bacterial infections; their development causes some noticeable resistance to antibacterial agents. Biofilms are responsible for at least two-thirds of all infections, displaying promoted resistance to classical antibiotic treatments. Therefore, finding new alternative therapeutic approaches is essential for the treatment and inhibition of biofilm-related infections. Therefore, this review aims to describe the potential therapeutic strategies that can inhibit bacterial biofilm development; these include the usage of antiadhesion agents, AMPs, bacteriophages, QSIs, aptamers, NPs and PNAs, which can prevent or eradicate the formation of biofilms. These antibiofilm agents represent a promising therapeutic target in the treatment of biofilm infections and development of a strong capability to interfere with different phases of the biofilm development, including adherence, polysaccharide intercellular adhesion (PIA), quorum sensing molecules and cell-to-cell connection, bacterial aggregation, planktonic bacteria killing and host-immune response modulation. In addition, these components, in combination with antibiotics, can lead to the development of some kind of powerful combined therapy against bacterial biofilm-related infections.

Inhibitory properties of Chinese Herbal Formula SanHuang decoction on biofilm formation by antibiotic-resistant Staphylococcal strains

The aim of this study was to explore the effect of Chinese herbal SanHuang decoction (SH) on biofilm formation of antibiotic-resistant Staphylococci on titanium surface, and to explore its mechanism. Biofilm-forming ATCC 35984, ATCC 43300 and MRSE 287 were used in this study. The MICs of SH and vancomycin against Staphylococci were determined by the broth microdilution method. Six groups were designed, namely control group (bacteria cultured with medium), 1/8MIC SH group (1MIC SH was diluted by 1/8 using TSB or saline), 1/4MIC SH group, 1/2MIC SH group, 1MIC SH group and vancomycin group (bacteria cultured with 1MIC vancomycin). The inhibitory effect on bacterial adhesion and biofilm formation were observed by the spread plate method, CV staining, SEM, and CLSM. Real-time PCR was performed to determine the effect of SH on the expression levels of ica AD and ica R gene in ATCC 35984 during the biofilm formation. The strains were found to be susceptible to SH and vancomycin with MIC of 38.75 mg/ml and 2.5 μg/ml, respectively. SH with 1 MIC and 1/2 MIC could inhibit the bacteria adhesion, showing only scattered adhesion from SEM. CLSM showed that SH with 1 MIC and 1/2 MIC inhibited the biofilm formation. The quantitative results of the spread plate method and CV staining showed that there was significant differences between the SH groups (P < 0.05). Further, with an increase in SH concentration, the inhibitory effect became more obvious when compared with control group. Among the groups, vancomycin had the strongest inhibitory effect on bacterial adhesion and biofilm formation (P < 0.01). With an increase in SH concentration, the expression levels of ica AD decreased, and the expression of ica R increased correspondingly (P < 0.05). In conclusions, SH can inhibit the biofilm formation of antibiotic-resistant Staphylococci. Its probable mechanistic activity may be through the inhibition of polysaccharide intercellular adhesin synthesis by down-regulating the expression of ica AD gene.

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.

Biomaterials against Bone Infection

Chronic bone infection is considered as one of the most problematic biofilm-related infections. Its recurrent and resistant nature, high morbidity, prolonged hospitalization, and costly medical care expenses have driven the efforts of the scientific community to develop new therapies to improve the standards used today. There is great debate on the management of this kind of infection in order to establish consistent and agreed guidelines in national health systems. The scientific research is oriented toward the design of anti-infective biomaterials both for prevention and cure. The properties of these materials must be adapted to achieve better anti-infective performance and good compatibility, which allow a good integration of the implant with the surrounding tissue. The objective of this review is to study in-depth the antibacterial biomaterials and the strategies underlying them. In this sense, this manuscript focuses on antimicrobial coatings, including the new technological advances on surface modification; scaffolding design including multifunctional scaffolds with both antimicrobial and bone regeneration properties; and nanocarriers based on mesoporous silica nanoparticles with advanced properties (targeting and stimuli-response capabilities).

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.

Microbiological and Cellular Evaluation of a Fluorine-Phosphorus-Doped Titanium Alloy, a Novel Antibacterial and Osteostimulatory Biomaterial with Potential Applications in Orthopedic Surgery

Joint prosthesis failure is mainly related to aseptic loosening and prosthetic joint infections, both of which are associated with high morbidity and substantial costs for patients and health systems. The development of a biomaterial that is capable of stimulating bone growth while minimizing bacterial adhesion would reduce the incidence of prosthetic failure. We report antibacterial and osteostimulatory effects in a novel fluorine-phosphorus (F-P)-doped TiO₂ oxide film grown on Ti-6Al-4V alloy with a nanostructure of bottle-shaped nanotubes (bNT) using five bacterial species (Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa, and Stenotrophomonas maltophilia) and MCT3T3-E1 osteoblastic cells. The interaction between the bacteria and bNT Ti-6Al-4V was complex, as the adhesion of four bacterial species decreased (two staphylococcus species, E. coli, and S. maltophilia), and the viability of staphylococci and S. maltophilia also decreased because of the aluminum (Al) released by bNT Ti-6Al-4V. This released Al can be recruited by the bacteria through siderophores and was retained only by the Gram-negative bacteria tested. P. aeruginosa showed higher adhesion on bNT Ti-6Al-4V than on chemically polished (CP) samples of Ti-6Al-4V alloy and an ability to mobilize Al from bNT Ti-6Al-4V. The cell adhesion and proliferation of MCT3T3-E1 osteoblastic cells significantly increased at 48 and 168 h, as did the matrix mineralization of these cells and the gene expression levels of three of the most important markers related to bone differentiation. According to our results, the bNT Ti-6Al-4V alloy could have clinical application, preventing infection and stimulating bone growth and thus preventing the two main causes of joint prosthesis failure.IMPORTANCE This work evaluates F-P-doped bNT Ti-6Al-4V from microbiological and cellular approaches. The bacterial results highlight that the antibacterial ability of bNT Ti-6Al-4V is the result of a combination of antiadhesive and bactericidal effects exerted by Al released from the alloy. The cell results highlight that F-P bNT Ti-6Al-4V alloy increases osseointegration due to modification of the chemical composition of the alloy resulting from P incorporation and not due to the nanostructure, as reported previously. A key finding was the detection of Al release from inside the bNT Ti-6Al-4V nanostructures, a result of the nanostructure growth during the anodizing process that is in part responsible for its bactericidal effect.

Decreased Porphyromonas gingivalis adhesion and improved biocompatibility on tetracycline-loaded TiO2 nanotubes: an in vitro study

Background

Titanium dioxide (TiO₂) nanotubes are often used as carriers for loading materials such as drugs, proteins, and growth factors.

Materials and methods

In this study, we loaded tetracycline onto TiO₂ nanotubes to demonstrate its antibacterial properties and biocompatibility. The two-layered anodic TiO₂ nanotubes with a honeycomb-like porous structure were fabricated by using a two-step anodization, and they were loaded with tetracycline by using a simplified lyophilization method and vacuum drying. Their physical properties, such as chemical compositions, wettability, and surface morphologies of the different samples, were observed and measured by X-ray photoelectron spectroscopy (XPS), contact angle measurement, and scanning electron microscopy (SEM). The in vitro growth behaviors of mouse bone marrow stromal cells (BMSCs) on these substrates were investigated.

Results

The TiO₂ nanotube (NT) substrates and the tetracycline-loaded TiO₂ nanotube (NT-T) substrates revealed a crucial potential for promoting the adhesion, proliferation, and differentiation of BMSCs. Similarly, the NT-T substrates displayed a sudden release of tetracycline in the first 15 minutes of their administration, and the release tended to be stable 90 minutes later. The antibacterial performances of the prepared substrates were assessed with Porphyromonas gingivalis. The result showed that NT and NT-T substrates had antibacterial capacities.

Conclusion

Overall, this research provides a promising method with potential for clinical translation by allowing local slow release of antimicrobial compounds by loading them onto constructed nanotubes.

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.

Antibiotic release from F-doped nanotubular oxide layer on TI6AL4V alloy to decrease bacterial viability

We aimed to evaluate the release of two antibiotics: gentamicin and vancomycin loaded into F-doped nanotubular anodic oxide layers, as well as their bactericide effect. F-doped nanotubular oxide layers fabricated on Ti-6Al-4V loaded with gentamicin (Gm), vancomycin (Vm) and their mixture (Gm + Vm) by a previously described loading method. Antibiotic release was studied by RP-HPLC and by a biological method. Bactericidal activity was evaluated by a bacterial adherence protocol described previously using on three clinically important bacterial species. The antibiotic release steady up to 120 and 180 min for Gm and Vm, respectively, and despite the antibiotic concentration decreased, their biological activity was maintained over time. The number of living bacteria of three species tested on NT-Gm specimens was significantly lower than on NT specimens without antibiotics (P < 0.01). There are significant differences among NT-Gm and NT-Gm + Vm specimens (P < 0.05) for S. aureus 15981, S. epidermidis ATCC 35984, and P. aeruginosa ATCC 27853 and no differences between NT-Vm and NT-Gm + Vm for staphylococci (P > 0.05). In conclusion, this Gm + Vm loading method added to the properties of F-doped nanotubular oxide layers fabricated on Ti-6Al-4V, and therefore surfaces with antibacterial, biocompatible, tissue integration stimulating and spread-spectrum bactericidal properties can be obtained.

The Incorporation of Strontium in a Sodium Alginate Coating on Titanium Surfaces for Improved Biological Properties

Orthopedic implant failure is mainly attributed to the poor bonding of the implant to bone tissue. An effective approach to minimize the implant failure would be modifying the surface of the implant. Strontium (Sr) can stimulate the proliferation and differentiation of osteoblasts and reduce the activity of osteoclasts. In this study, a titanium (Ti) surface was successively functionalized by covalently grafting dopamine, sodium alginate (SA), and Sr²⁺ via the electrostatic immobilization method. The as-prepared coatings on the Ti surface were characterized by using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and contact angle. The results indicated that the Sr-incorporated coatings were successfully prepared and that Sr distributed uniformly on the surface. A long-lasting and sustained Sr release had been observed in Sr²⁺ release studies. The Ti/DOPA/SA/Sr exhibited little cytotoxicity and a robust effect of Sr incorporation on the adhesion and spreading of MG63 cells. The proliferation and alkaline phosphatase (ALP) activity of MG63 cells were enhanced by immobilizing Sr²⁺ on the SA-grafted Ti. The Sr-containing coatings, which displayed excellent biocompatibility and osteogenic activity, may provide a promising solution for promoting the tissue integration of implants.

Gentamicin coating of nanotubular anodized titanium implant reduces implant-related osteomyelitis and enhances bone biocompatibility in rabbits

Titanium and titanium alloy are widely used as orthopedic implants for their favorable mechanical properties and satisfactory biocompatibility. The aim of the present study was to investigate the antibacterial effect and bone cell biocompatibility of a novel implant made with nanotubular anodized titanium coated with gentamicin (NTATi-G) through in vivo study in rabbits. The animals were divided into four groups, each receiving different kinds of implants, that is, NTATi-G, titanium coated with gentamicin (Ti-G), nanotubular anodized titanium uncoated with gentamicin (NTATi) and titanium uncoated with gentamicin (Ti). The results showed that NTATi-G implant prevented implant-related osteomyelitis and enhanced bone biocompatibility in vivo. Moreover, the body temperature of rabbits in NTATi-G and Ti-G groups was lower than those in Ti groups, while the weight of rabbits in NTATi-G and Ti-G groups was heavier than those in NTATi and Ti groups, respectively. White blood cell counts in NTATi-G group were lower than NTATi and Ti groups. Features of myelitis were observed by X-ray films in the NTATi and Ti groups, but not in the NTATi-G and Ti-G groups. The radiographic scores, which assessed pathology and histopathology in bone tissues, were significantly lower in the NTATi-G and Ti-G groups than those in the NTATi and Ti groups, respectively (P<0.05). Meanwhile, explants and bone tissue culture demonstrated significantly less bacterial growth in the NTATi-G and Ti-G groups than in the NTATi and Ti groups, respectively (P<0.01). The bone volume in NTATi-G group was greater than Ti-G group, and little bone formation was seen in NTATi and Ti groups.

Bacterial inhibition potential of quaternised chitosan-coated VICRYL absorbable suture: An in vitro and in vivo study

BACKGROUND/OBJECTIVE

As a widely used absorbable suture with antibacterial property, triclosan- coated polyglactin suture (Vicryl Plus) has been extensively utilized to reduce the occurrence rate of surgical site infections (SSIs) in orthopaedic surgery. However, the potential toxicity and side-effects of triclosan raised increasing concerns about its biological safety. This study aimed to investigate the antimicrobial activity and biocompatibility of quaternised chitosan-coated Vicryl suture (HV) both in vitro and in vivo.

METHODS

In this study, a modified chitosan derivate, (hydroxypropyltrimethyl ammonium chloride chitosan, HACC), was coated over the surface of the absorbable Vicryl suture. Two standard bacteria strains, Staphylococcus epidermidis (ATCC35984) and methicillin-resistant Staphylococcus aureus (ATCC43300), were selected to evaluate bacterial adhesion and biofilm formation on the sutures at 6, 24 and 48 h in vitro. Additionally, human skin-derived fibroblasts cells were used to test the cytocompatibility of the sutures. Furtherly, sutures contaminated with methicillin-resistant S. aureus were implanted subcutaneously in SD rats in order to confirm the in vivo antibacterial performance and biocompatibility.

RESULTS

We found that HACC-coated Vicryl suture (HV) exhibited significant anti-bacterial effects on the two tested strains. The bacterial attachment and biofilm formation on the surface of the HV sutures were found to be comparable to that of Vicryl Plus sutures (VP). Moreover, all the four tested sutures presented good cytocompatibility with human skin-derived fibroblasts cells. Histology and immunohistochemistry results indicated that the infections and inflammations were significantly inhibited around the HV and VP sutures.

CONCLUSION

In general, the present study demonstrated that the quaternised chitosan coating is a flexible and cost-effective alternative strategy to prevent the suture related surgical site infections in orthopaedic practices.

Cytocompatibility with osteogenic cells and enhanced in vivo anti-infection potential of quaternized chitosan-loaded titania nanotubes

Infection is one of the major causes of failure of orthopedic implants. Our previous study demonstrated that nanotube modification of the implant surface, together with nanotubes loaded with quaternized chitosan (hydroxypropyltrimethyl ammonium chloride chitosan, HACC), could effectively inhibit bacterial adherence and biofilm formation in vitro. Therefore, the aim of this study was to further investigate the in vitro cytocompatibility with osteogenic cells and the in vivo anti-infection activity of titanium implants with HACC-loaded nanotubes (NT-H). The titanium implant (Ti), nanotubes without polymer loading (NT), and nanotubes loaded with chitosan (NT-C) were fabricated and served as controls. Firstly, we evaluated the cytocompatibility of these specimens with human bone marrow-derived mesenchymal stem cells in vitro. The observation of cell attachment, proliferation, spreading, and viability in vitro showed that NT-H has improved osteogenic activity compared with Ti and NT-C. A prophylaxis rat model with implantation in the femoral medullary cavity and inoculation with methicillin-resistant Staphylococcus aureus was established and evaluated by radiographical, microbiological, and histopathological assessments. Our in vivo study demonstrated that NT-H coatings exhibited significant anti-infection capability compared with the Ti and NT-C groups. In conclusion, HACC-loaded nanotubes fabricated on a titanium substrate show good compatibility with osteogenic cells and enhanced anti-infection ability in vivo, providing a good foundation for clinical application to combat orthopedic implant-associated infections.

In vivo evaluation of the anti-infection potential of gentamicin-loaded nanotubes on titania implants

Titanium-based implants have been widely used in orthopedic surgery; however, failures still occur. Our in vitro study has demonstrated that gentamicin-loaded, 80 nm-diameter nanotubes possessed both antibacterial and osteogenic activities. Thus, the aim of this study was to further investigate the in vivo anti-infection effect of the titanium implants with gentamicin-loaded nanotubes. Thirty-six male Sprague Dawley rats were used to establish an implant-associated infection model. A volume of 50 μL Staphylococcus aureus suspension (1×10⁵ CFU/mL) was injected into the medullary cavity of the left femur, and then the titanium rods without modification (Ti), titanium nanotubes without drug loading (NT), and gentamicin-loaded titanium nanotubes (NT-G) were inserted with phosphate-buffered saline-inoculated Ti rods as a blank control. X-ray images were obtained 1 day, 21 days, and 42 days after surgery; micro-computed tomography, microbiological, and histopathological analyses were used to evaluate the infections at the time of sacrifice. Radiographic signs of bone infection, including osteolysis, periosteal reaction, osteosclerosis, and damaged articular surfaces, were demonstrated in the infected Ti group and were slightly alleviated in the NT group but not observed in the NT-G group. Meanwhile, the radiographic and gross bone pathological scores of the NT-G group were significantly lower than those of the infected Ti group (P<0.01). Explant cultures revealed significantly less bacterial growth in the NT-G group than in the Ti and NT groups (P<0.01), and the NT group showed decreased live bacterial growth compared with the Ti group (P<0.01). Confocal laser scanning microscopy, scanning electron microscopy, and histopathological observations further confirmed decreased bacterial burden in the NT-G group compared with the Ti and NT groups. We concluded that the NT-G coatings can significantly prevent the development of implant-associated infections in a rat model; therefore, they may provide an effective drug-loading strategy to combat implant-associated infections in clinic.

Inhibited Bacterial Adhesion and Biofilm Formation on Quaternized Chitosan-Loaded Titania Nanotubes with Various Diameters

Titania nanotube-based local drug delivery is an attractive strategy for combating implant-associated infection. In our previous study, we demonstrated that the gentamicin-loaded nanotubes could dramatically inhibit bacterial adhesion and biofilm formation on implant surfaces. Considering the overuse of antibiotics may lead to the evolution of antibiotic-resistant bacteria, we synthesized a new quaternized chitosan derivative (hydroxypropyltrimethyl ammonium chloride chitosan, HACC) with a 27% degree of substitution (DS; referred to as 27% HACC) that had a strong antibacterial activity and simultaneously good biocompatibility with osteogenic cells. Titania nanotubes with various diameters (80, 120, 160, and 200 nm) and 200 nm length were loaded with 2 mg of HACC using a lyophilization method and vacuum drying. Two standard strain, methicillin-resistant Staphylococcus aureus (American Type Culture Collection 43300) and Staphylococcus epidermidis (American Type Culture Collection 35984), and two clinical isolates, S. aureus 376 and S. epidermidis 389, were selected to investigate the bacterial adhesion at 6 h and biofilm formation at 24, 48, and 72 h on the HACC-loaded nanotubes (NT-H) using the spread plate method, confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM). Smooth titanium (Smooth Ti) was also investigated and compared. We found that NT-H could significantly inhibit bacterial adhesion and biofilm formation on its surface compared with Smooth Ti, and the NT-H with 160 nm and 200 nm diameters had stronger antibacterial activity because of the extended HACC release time of NT-H with larger diameters. Therefore, NT-H can significantly improve the antibacterial ability of orthopedic implants and provide a promising strategy to prevent implant-associated infections.

Antibacterial Effects and Biocompatibility of Titania Nanotubes with Octenidine Dihydrochloride/Poly(lactic-co-glycolic acid)

Titanium (Ti) implants with long-term antibacterial ability and good biocompatibility are highly desirable materials that can be used to prevent implant-associated infections. In this study, titania nanotubes (TNTs) were synthesized on Ti surfaces through electrochemical anodization. Octenidine dihydrochloride (OCT)/poly(lactic-co-glycolic acid) (PLGA) was infiltrated into TNTs using a simple solvent-casting technique. OCT/PLGA-TNTs demonstrated sustained drug release and maintained the characteristic hollow structures of TNTs. TNTs (200 nm in diameter) alone exhibited slight antibacterial effect and good osteogenic activity but also evidently impaired adhesion and proliferation of bone marrow mesenchymal stem cells (BMSCs). OCT/PLGA-TNTs (100 nm in diameter) supported BMSC adhesion and proliferation and showed good osteogenesis-inducing ability. OCT/PLGA-TNTs also exhibited good long-term antibacterial ability within the observation period of 7 d. The synthesized drug carrier with relatively long-term antibacterial ability and enhanced excellent biocompatibility demonstrated significant potential in bone implant applications.

Bioactive coatings for orthopaedic implants-recent trends in development of implant coatings

Joint replacement is a major orthopaedic procedure used to treat joint osteoarthritis. Aseptic loosening and infection are the two most significant causes of prosthetic implant failure. The ideal implant should be able to promote osteointegration, deter bacterial adhesion and minimize prosthetic infection. Recent developments in material science and cell biology have seen the development of new orthopaedic implant coatings to address these issues. Coatings consisting of bioceramics, extracellular matrix proteins, biological peptides or growth factors impart bioactivity and biocompatibility to the metallic surface of conventional orthopaedic prosthesis that promote bone ingrowth and differentiation of stem cells into osteoblasts leading to enhanced osteointegration of the implant. Furthermore, coatings such as silver, nitric oxide, antibiotics, antiseptics and antimicrobial peptides with anti-microbial properties have also been developed, which show promise in reducing bacterial adhesion and prosthetic infections. This review summarizes some of the recent developments in coatings for orthopaedic implants.