Release of Cu2+ from a copper-filled TiO2 coating in a rabbit model for total knee arthroplasty

Antibacterial copper-filled TiO2 coating of cardiovascular implants to prevent infective endocarditis-A pilot study

BACKGROUND

Infective endocarditis (IE) poses a significant health risk, especially in patients with prosthetic heart valves. Despite advances in treatment, mortality rates remain high. This study aims to investigate the antibacterial properties of a copper titanium dioxide (4× Cu-TiO2) coating on cardiovascular implants against Staphylococcus aureus, a common causative agent of IE.

METHODS

Titanium oxide carriers functionalized with copper ions were employed as an antibacterial coating for heart and vascular prostheses. The coating's antibacterial efficacy was assessed using S. aureus ATCC 29213. Microscopic evaluations were conducted on both biological and artificial materials. Antibacterial activity was qualitatively assessed via a modified disc diffusion method and quantitatively measured through colony counts in NaCl suspensions.

RESULTS

The coating process was successfully applied to all tested cardiovascular prosthetic materials. Qualitative assessments of antibacterial effectiveness revealed an absence of bacterial growth in the area directly beneath the coated valve. Quantitative evaluations showed a significant reduction in bacterial colonization on coated mechanical valves, with 2.95 × 104 CFU per valve, compared to 1.91 × 105 CFU in control valves.

CONCLUSIONS

The 4× Cu-TiO2 coating demonstrated promising antibacterial properties against S. aureus, suggesting its potential as an effective strategy for reducing the risk of bacterial colonization of cardiovascular implants. Further studies are needed to assess the longevity of the coating and its efficacy against other pathogens.

Current Progress and Future Perspectives in Contact and Releasing-Type Antimicrobial Coatings of Orthopaedic Implants: A Systematic Review Analysis Emanated from In Vitro and In Vivo Models

Background: Despite the expanding use of orthopedic devices and the application of strict pre- and postoperative protocols, the elimination of postoperative implant-related infections remains a challenge. Objectives: To identify and assess the in vitro and in vivo properties of antimicrobial-, silver- and iodine-based implants, as well as to present novel approaches to surface modifications of orthopedic implants. Methods: A systematic computer-based review on the development of these implants, on PubMed and Web of Science databases, was carried out according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Results: Overall, 31 in vitro and 40 in vivo entries were evaluated. Regarding the in vitro studies, antimicrobial-based coatings were assessed in 12 entries, silver-based coatings in 10, iodine-based in 1, and novel-applied coating technologies in 8 entries. Regarding the in vivo studies, antimicrobial coatings were evaluated in 23 entries, silver-coated implants in 12, and iodine-coated in 1 entry, respectively. The application of novel coatings was studied in the rest of the cases (4). Antimicrobial efficacy was examined using different bacterial strains, and osseointegration ability and biocompatibility were examined in eukaryotic cells and different animal models, including rats, rabbits, and sheep. Conclusions: Assessment of both in vivo and in vitro studies revealed a wide antimicrobial spectrum of the coated implants, related to reduced bacterial growth, inhibition of biofilm formation, and unaffected or enhanced osseointegration, emphasizing the importance of the application of surface modification techniques as an alternative for the treatment of orthopedic implant infections in the clinical settings.

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.

Antibacterial Activity of Ag-Hydroxyapatite Coating Against Hematogenous Infection by Methicillin-Resistant Staphylococcus aureus in the Rat Femur

Several antibacterial materials have been developed to prevent periprosthetic joint infection and thus prevent serious complications for patients and surgeons. However, no study has addressed the activity of antibacterial materials against hematogenous infection. The present study evaluated the antibacterial activity of a silver-containing hydroxyapatite-coated implant against methicillin-resistant Staphylococcus aureus (MRSA) hematogenous infection. Implants coated with hydroxyapatite and silver-hydroxyapatite were inserted into rats' right and left femurs, respectively, after which the animals were infected with S. aureus via a tail vessel. About 10⁷ colony-forming units was the optimal bacterial number for the establishment of S. aureus hematogenous infection. Bacterial loads and C-reactive protein in the blood were measured to confirm bacteremia and inflammation. Fourteen days after the infection, bacterial loads were statistically lower in the femurs containing silver-hydroxyapatite-coated implants than in those with hydroxyapatite-coated implants (p = 0.022). Thus, silver-hydroxyapatite-coated implants might provide antibacterial activity against MRSA hematogenous infection in the postoperative period. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2655-2660, 2019.

Antibacterial Effect of a 4x Cu-TiO₂ Coating Simulating Acute Periprosthetic Infection-An Animal Model

The purpose of our study was to investigate the antibacterial effect of a spacer (Ti6Al4V) coated with 4x Cu-TiO₂ in an animal model simulating an acute periprosthetic infection by Staphylococcus aureus. Ti6Al4 bolts contaminated with Staphylococcus aureus were implanted into the femoral condyle of rabbits (n = 36) divided into 3 groups. After one week in group 1 (control) the bolts were removed without any replacement. In group2 Ti6Al4V bolts with a 4x Cu-TiO₂ coating and in group 3 beads of a gentamicin-PMMA chain were imbedded into the borehole. Microbiological investigation was performed at the primary surgery, at the revision surgery and after scarification of the rabbits 3 weeks after the first surgery. Blood tests were conducted weekly. The initial overall infection rate was 88.9%. In group 2 and 3 a significant decrease of the infection rate was shown in contrast to the control group. The C-reactive protein (CRP) levels declined one week after the first surgery except in the control group where the CRP level even increased. This is the first in vivo study that demonstrated the antibacterial effects of a fourfold Cu-TiO₂ coating. For the future, the coating investigated could be a promising option in the treatment of implant-associated infections.

Antimicrobial and bone-forming activity of a copper coated implant in a rabbit model

Current strategies in implant technology are directed to generate bioactive implants that are capable to activate the regenerative potential of the surrounding tissue. On the other hand, implant-related infections are a common problem in orthopaedic trauma patients. To meet both challenges, i.e. to generate a bone implant with regenerative and antimicrobial characteristics, we tested the use of copper coated nails for surgical fixation in a rabbit model. Copper acetate was galvanically deposited with a copper load of 1 µg/mm² onto a porous oxide layer of Ti6Al4V nails, which were used for the fixation of a tibia fracture, inoculated with bacteria. After implantation of the nail the concentration of copper ions did not increase in blood which indicates that copper released from the implant was locally restricted to the fracture site. After four weeks, analyses of the extracted implants revealed a distinct antimicrobial effect of copper, because copper completely prevented both a weak adhesion and firm attachment of biofilm-forming bacteria on the titanium implant. To evaluate fracture healing, radiographic examination demonstrated an increased callus index in animals with copper coated nails. This result indicates a stimulated bone formation by releasing copper ions. We conclude that the use of implants with a defined load of copper ions enables both prevention of bacterial infection and the stimulation of regenerative processes.

Antifouling and antimicrobial biomaterials: an overview

The use of implantable medical devices is a common and indispensable part of medical care for both diagnostic and therapeutic purposes. However, as side effect, the implant of medical devices quite often leads to the occurrence of difficult-to-treat infections, as a consequence of the colonization of their abiotic surfaces by biofilm-growing microorganisms increasingly resistant to antimicrobial therapies. A promising strategy to combat device-related infections is based on anti-infective biomaterials that either repel microbes, so they cannot attach to the device surfaces, or kill them in the surrounding areas. In general, such biomaterials are characterized by antifouling coatings, exhibiting low adhesion or even repellent properties towards microorganisms, or antimicrobial coatings, able to kill microbes approaching the surface. In this light, the present overview will address the development in the last two decades of antifouling and antimicrobial biomaterials designed to potentially limit the initial stages of microbial adhesion, as well as the microbial growth and biofilm formation on medical device surfaces.

Recent coating developments for combination devices in orthopedic and dental applications: A literature review

Orthopedic and dental implants have been used successfully for decades to replace or repair missing or damaged bones, joints, and teeth, thereby restoring patient function subsequent to disease or injury. However, although device success rates are generally high, patient outcomes are sometimes compromised due to device-related problems such as insufficient integration, local tissue inflammation, and infection. Many different types of surface coatings have been developed to address these shortcomings, including those that incorporate therapeutic agents to provide localized delivery to the surgical site. While these coatings hold enormous potential for improving device function, the list of requirements that an ideal combination coating must fulfill is extensive, and no single coating system today simultaneously addresses all of the criteria. Some of the primary challenges related to current coatings are non-optimal release kinetics, which most often are too rapid, the potential for inducing antibiotic resistance in target organisms, high susceptibility to mechanical abrasion and delamination, toxicity, difficult and expensive regulatory approval pathways, and high manufacturing costs. This review provides a survey of the most recent developments in the field, i.e., those published in the last 2-3years, with a particular focus on technologies that have potential for overcoming the most significant challenges facing therapeutically-loaded coatings. It is concluded that the ideal coating remains an unrealized target, but that advances in the field and emerging technologies are bringing it closer to reality. The significant amount of research currently being conducted in the field provides a level of optimism that many functional combination coatings will ultimately transition into clinical practice, significantly improving patient outcomes.

Antibacterial and Biocompatible Titanium-Copper Oxide Coating May Be a Potential Strategy to Reduce Periprosthetic Infection: An In Vitro Study

BACKGROUND

Periprosthetic infections are devastating for patients and more efficacious preventive strategies are needed. Surface-modified implants using antibacterial coatings represent an option to cope with this problem; however, manufacturing limitations and cytotoxicity have curbed clinical translation. Among metals with antibacterial properties, copper has shown superior in vitro antibacterial performance while maintaining an acceptable cytotoxicity profile. A thin film containing copper could prevent early biofilm formation to limit periprosthetic infections. This pilot study presents the in vitro antibacterial effect, cytotoxicity, and copper ion elution pattern of a thin film of titanium-copper oxide (TiCuO).

QUESTIONS/PURPOSES

(1) Do titanium alloy (Ti6Al4V) discs coated with a thin film of TiCuO reduce Staphylococcus epidermidis biofilm and planktonic cell density compared with uncoated discs? (2) Do Ti6Al4V discs coated with a thin film of TiCuO affect normal human osteoblast viability compared with untreated cells? (3) Is copper ion concentration generated by coated discs lower than previously published copper ion concentrations that cause 50% toxicity in similar human cell lines in vitro (TC50)?

METHODS

Ninety Ti6Al4V discs (12.5 mm diameter; 1.25 mm thick) were used in this study. Seventy-two Ti6Al4V discs were coated with a thin film of either titanium oxide (TiO) or TiCuO containing 20%, 40%, or 80% copper using high-power impulse magnetron sputtering (HiPIMS). Eighteen Ti6Al4V discs remained uncoated for control purposes. We tested antibacterial properties of S epidermidis grown on discs in wells containing growth medium. After 24 hours, planktonic bacteria as well as biofilms removed by sonication were quantitatively cultured. Annexin/Pi staining was used to quantify in vitro normal human osteoblast cell viability at 24 hours and Day 7, respectively. Copper elution was measured at Days 1, 2, 3, 7, 14, and 28 using an inductively coupled plasma mass spectrometer to analyze aliquots of culture medium. Copper ion concentration achieved at 24 hours was compared with previously published TC50 for gingival fibroblast, a phenotypically similar cell line with available data regarding copper ion exposure.

RESULTS

Discs coated with TiCuO 80% copper showed greater biofilm and planktonic cell density reduction when compared with other tested compositions (analysis of variance [ANOVA]; p < 0.001). Discs coated with TiCuO 80% copper showed mean biofilm and planktonic cell density of 4.0 log₁₀ (SD = 0.4) and 5.7 log₁₀ (SD = 0.2). Discs coated with TiCuO 80% showed a mean difference in biofilm and planktonic cell density of 2.5 log₁₀ (95% confidence interval [CI], 1.9-3.1 log_10; p < 0.001) and 1.2 (95% CI, 0.6-1.8; p < 0.001), respectively, when compared with uncoated discs. Normal human osteoblast viability did not differ among all groups at 24 hours (ANOVA; p = 0.2) and Day 7 (ANOVA; p = 0.7). Discs coated with TiCuO 80% copper showed a mean difference (95% CI) in relative cell viability (%) at 24 hours and Day 7 of 31.1 (95% CI, -19.4 to 81.7; p = 0.4) and -5.0 (95% CI, -7.8 to 17.9; p = 0.9), respectively, when compared with untreated cells. For all TiCuO-coated discs, copper ion elution peaked at 24 hours and slowly decreased in a curvilinear fashion to nearly undetectable levels by Day 28. Discs coated with TiCuO 80% copper showed mean copper ion concentration at 24 hours of 269.4 µmol/L (SD = 25.2 µmol/L) and this concentration was lower than previously published TC50 for similar human cell lines at 24 hours (344 µmol/L, SEM = 44 µmol/L).

CONCLUSIONS

This pilot study demonstrates a proof of concept that a thin-film implant coating with TiCuO can provide a potent local antibacterial environment while remaining relatively nontoxic to a human osteoblast cell line. Further research in an animal model will be necessary to establish efficacy and safety of this technique and whether it might be useful in the design of implants.

CLINICAL RELEVANCE

A thin film coating with TiCuO demonstrates high antibacterial activity and low cellular cytotoxicity to human osteoblasts in vitro. Taken together, these properties represent a potential strategy for preventing periprosthetic infection if further work in animal models can confirm these results in vivo.