Surface coating of orthopedic implant to enhance the osseointegration and reduction of bacterial colonization: a review

Synergistic NIR and ultrasound-responsive tellurium nanorods for enhanced antibacterial and osteogenic activity

Bacterial infections and deficient osteogenic activity are the primary factors contributing to the failure of orthopedic implants. In recent years, light- and sound-based external stimulus-responsive therapies have emerged as highly effective in killing drug-resistant bacteria. In this study, we successfully synthesized tellurium nanorods coated with bovine serum albumin (Te@BSA). This novel nanomaterial exhibits excellent biocompatibility and possesses near-infrared light (NIR) and ultrasound (US) synergistic response properties. At a concentration of 100 μg/mL, Te@BSA nanorods, under combined NIR and US treatment, achieved 94 % bacterial eradication against drug-resistant strains, while maintaining cell viability above 90 % in osteoblast cultures. This dual-modality approach minimizes the risk of local thermal damage associated with conventional photothermal therapy, enhancing osteogenic activity by up to 150 % upon NIR exposure. By combining photothermal therapy and sonodynamic therapy, we achieved a remarkable antibacterial effect and enhanced osteogenic capacities in a mild and controlled manner. This study successfully balances antibacterial and osteogenic capabilities. These light- and sound-based external stimulus-responsive strategies aslo offer new perspectives and valuable insights for the surface modification of orthopedic implants.

Microfilm Coatings: A Biomaterial-Based Strategy for Modulating Femoral Deflection

Wear on the surface of the femoral head increases the risk of hip and femur fractures. Biomechanical experiments conducted on the femur are based on its bending and torsional rigidities. Studies regarding the deflection of the femur bone when the femoral head is coated with microfilms composed of durable and compatible biomaterials are poor. This study aimed to investigate the effects of different biomaterial microfilm coatings over the femoral head on the deflection of the human femur. We utilized 2023 R1 finite element analysis (FEA) software to model the directional deformation on the femoral head and examine the femur's deflection with varying microfilm thicknesses. The deflection of the femur bone was reported when the femoral head was uncoated and coated with titanium, stainless steel, and pure gold microfilms of different thicknesses (namely, 50, 75, and 100 μm). Our results show that the femur's minimum and maximum deflection occurred for stainless steel and gold, respectively. The deformation of the femur was lower when the femoral head was coated with a 50-micrometer microfilm of stainless steel, compared to the deformation obtained with gold and titanium. When the thickness of the microfilm for each of the materials was increased, the deformation continued to decrease. The minimum deformation of the femur occurred for a thickness of 100 μm with stainless steel, followed by titanium and gold. The difference in the directional deformation of the femur between the materials was more significant when the coating was 100 μm, compared to the thicknesses of 50 and 75 μm. The findings of this study are expected to significantly contribute to the development of advanced medical techniques to enhance the quality of life for patients with femur bone-related issues. This information can be used to develop more resilient coatings that can withstand wear and tear.

Multifunctionally disordered TiO2 nanoneedles prevent periprosthetic infection and enhance osteointegration by killing bacteria and modulating the osteoimmune microenvironment

Rationale: Total hip arthroplasty (THA) and total knee arthroplasty (TKA) are effective interventions for end-stage osteoarthritis; however, periprosthetic infection is a devastating complication of arthroplasty. To safely prevent periprosthetic infection and enhance osteointegration, the surface modification strategy was utilized to kill bacteria, modulate the osteoimmune microenvironment, and improve new bone formation. Methods: We used the hydrothermal method to fabricate a bionic insect wing with the disordered titanium dioxide nanoneedle (TNN) coating. The mussel-inspired poly-dopamine (PDA) and antibacterial silver nanoparticles (AgNPs) were coated on TNN, named AgNPs-PDA@TNN, to improve the biocompatibility and long-lasting bactericidal capacity. The physicochemical properties of the engineered specimen were evaluated with SEM, AFM, XPS spectrum, and water contact assay. The biocompatibility, bactericidal ability, and the effects on macrophages and osteogenic differentiation were assessed with RT-qPCR, Western blotting, live/dead staining, immunofluorescent staining, etc. Results: The AgNPs-PDA@TNN were biocompatible with macrophages and exhibited immunomodulatory ability to promote M2 macrophage polarization. In addition, AgNPs-PDA@TNN ameliorated the cytotoxicity caused by AgNPs, promoted cell spreading, and increased osteogenesis and matrix deposition of BMSCs. Furthermore, AgNPs-PDA@TNN exhibited bactericidal ability against E. coli and S. aureus by the bionic nanostructure and coated AgNPs. Various imaging analyses indicated the enhanced bactericidal ability and improved new bone formation by AgNPs-PDA@TNN in vivo. H&E, Gram, and Masson staining, verified the improved bone formation, less inflammation, infection, and fibrosis encapsulation. The immunofluorescence staining confirmed the immunomodulatory ability of AgNPs-PDA@TNN in vivo. Conclusion: The bionic insect wing AgNPs-PDA@TNN coating exhibited bactericidal property, immunomodulatory ability, and enhanced osteointegration. Thus, this multidimensional bionic implant surface holds promise as a novel strategy to prevent periprosthetic infection.

Advancing Diagnostic Techniques for Implant-Related Infections: the Synergistic Effect of Sonication and Dithiothreitol

PURPOSE

Implant-related infections represent a significant complication contributing to increased morbidity and mortality. Determining the microbial agent causing the infection is crucial for successful treatment. Despite the incidence of periprosthetic joint infections (PJIs) rising over time, no diagnostic test with 100% sensitivity is available to identify these infections accurately. The present study aims to determine whether combining sonication with Dithiothreitol (DTT) enhances the accuracy and sensitivity in diagnosing implant-related infections.

METHODS

Specifically, the present study included 30 patients, who underwent implant removal due to suspicion of infection. Implants were divided into two segments: one was processed using the sonication method and the other one by combining DTT and sonication.

RESULTS

The mean +/-SD was 81.17 +/- 67.53 CFU/mL for the sonication group and 109.7 +/-62.78 CFU/mL for the combination group.

CONCLUSION

The results of our study indicate that the combination of DTT and sonication increases the colony count by about 28.53 CFU/mL, which enhances the possibility of detecting orthopaedic implant associated infections.

Bioresorbable Polyester Coatings with Antifouling and Antimicrobial Properties for Prevention of Biofilm Formation in Early Stage Infections on Ti6Al4V Hard-Tissue Implants

Implants made from titanium are used as prostheses because of their biocompatibility and their mechanical properties close to those of human bone. However, the risk of bacterial infection is always a major concern during surgery, and the development of biofilm can make these infections difficult to treat. A promising strategy to mitigate against bacterial infections is the use of antifouling and antimicrobial coatings, where bioresorbable polymers can play an important role due to their controlled degradability and sustained drug release, as well as excellent biocompatibility. In the present study, poly(d,l-lactide) (PDLLA) and poly[d,l-lactide-co-methyl ether poly(ethylene glycol)] (PDLLA-PEG) were studied, varying the PEG content (20-40% w/w) to analyze the effectiveness of PEG as an antifouling molecule. In addition, silver sulfadiazine (AgSD) was used as an additional antimicrobial agent with a concentration ≤5% w/w and incorporated into the PEGylated polymers to create a polymer with both antifouling and antimicrobial properties. Polymers synthesized were applied using spin coating to obtain homogeneous coatings to protect samples made from titanium/aluminum/vanadium (Ti6Al4V). The polymer coatings had a smoothing effect in comparison to that of the uncoated material, decreasing the contact area available for bacterial colonization. It was also noted that PEG addition into the polymeric chain developed amphiphilic materials with a decrease in contact angle from the most hydrophobic (Ti6Al4V) to the most hydrophilic PDLLA-PEG (60/40), highlighting the increase in water uptake contributing to the hydration layer formation, which confers the antifouling effect on the coating. This study demonstrated that the addition of PEG above 20% w/w and AgSD above 1% w/v into the formulation was able to decrease bacterial adherence against clinically relevant biofilm former strains Staphylococcus aureus and Pseudomonas aeruginosa.

Silver phosphate-modified carbonate apatite honeycomb scaffolds for anti-infective and pigmentation-free bone tissue engineering

Bone regeneration using synthetic materials has a high rate of surgical site infection, resulting in severe pain for patients and often requiring revision surgery. We propose Ag3PO4-based surface modification and structural control of scaffolds for preventing infections in bone regeneration. We demonstrated the differences in toxicity and antibacterial activity between in vitro and in vivo studies and determined the optimal silver content in terms of overall anti-infection effects, bone regeneration, toxicity, and pigmentation. A honeycomb structure comprising osteoconductive and resorbable carbonate apatite (CAp) was used as the base scaffold. CAp in the scaffold surface was partially replaced with different concentrations of Ag3PO4 via controlled dissolution-precipitation reactions in an AgNO3 solution. Both bone regeneration and infection prevention were achieved at 860-2300 ppm of silver. Despite the absence of Ag3PO4, honeycomb scaffolds were less susceptible to infection, even under conditions where infection occurs in clinically used three-dimensional porous scaffolds. Regardless of in vitro cytotoxicity at >5200 ppm of silver, increasing the silver content to 21,000 ppm did not adversely affect in vivo bone formation and scaffold resorption or cause acute systemic toxicity. Rather, bone formation was enhanced with 5200 ppm of silver. However, pigmentation was observed at that concentration. Hence, we concluded that the optimal silver concentration range is 860-2300 ppm for anti-infective and pigmentation-free bone regeneration. Bone regeneration was achieved via surface modification, resulting in the rapid release of silver ions immediately after implantation, followed by gradual release over several months. The scaffold structure may also aid in preventing bacterial growth within the scaffolds.

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.

Advancements in Aerogel Technology for Antimicrobial Therapy: A Review

This paper explores the latest advancements in aerogel technology for antimicrobial therapy, revealing their interesting capacity that could improve the current medical approaches for antimicrobial treatments. Aerogels are attractive matrices because they can have an antimicrobial effect on their own, but they can also provide efficient delivery of antimicrobial compounds. Their interesting properties, such as high porosity, ultra-lightweight, and large surface area, make them suitable for such applications. The fundamentals of aerogels and mechanisms of action are discussed. The paper also highlights aerogels' importance in addressing current pressing challenges related to infection management, like the limited drug delivery alternatives and growing resistance to antimicrobial agents. It also covers the potential applications of aerogels in antimicrobial therapy and their possible limitations.

Electrophoretic Deposition of 58S Bioactive Glass- Polymer Composite Coatings on 316L Stainless Steel: An Optimization for Corrosion, Bioactivity, and Cytocompatibility

This study presents a facile fabrication of 58S bioactive glass (BG)-polymer composite coatings on a 316L stainless steel (SS) substrate using the electrophoretic deposition technique. The suspension characteristics and deposition kinetics of BG, along with three different polymers, namely ethylcellulose (EC), poly(acrylic acid) (PAA), and polyvinylpyrrolidone (PVP), have been utilized to fabricate the coatings. Among all coatings, 58S BG and EC polymers are selected as the final composite coating (EC6) owing to their homogeneity and good adhesion. EC6 coating exhibits a thickness of ∼18 μm and an average roughness of ∼2.5 μm. Herein, EC6 demonstrates better hydroxyapatite formation compared to PAA and PVP coatings in simulated body fluid-based mineralization studies for a period of 28 days. Corrosion studies of EC6 in phosphate-buffered saline further confirm the higher corrosion resistance properties after 14 days. In vitro cytocompatibility studies using human placental mesenchymal stem cells demonstrate an increase in cellular viability, attachment, and higher proliferation compared to the bare SS substrate. EC6 coatings promote osteogenic differentiation, which is confirmed via the upregulation of the OPN and OCN genes. Moreover, the EC6 sample exhibits improved antibacterial properties against Escherichia coli and Staphylococcus aureus compared to the uncoated ones. The findings of this work emphasize the potential of electrophoretically fabricated BG-EC composite coatings on SS substrates for orthopedic applications.

Antibiofilm and antithrombotic hydrogel coating based on superhydrophilic zwitterionic carboxymethyl chitosan for blood-contacting devices

Blood-contacting devices must be designed to minimize the risk of bloodstream-associated infections, thrombosis, and intimal lesions caused by surface friction. However, achieving effective prevention of both bloodstream-associated infections and thrombosis poses a challenge due to the conflicting nature of antibacterial and antithrombotic activities, specifically regarding electrostatic interactions. This study introduced a novel biocompatible hydrogel of sodium alginate and zwitterionic carboxymethyl chitosan (ZW@CMC) with antibacterial and antithrombotic activities for use in catheters. The ZW@CMC hydrogel demonstrates a superhydrophilic surface and good hygroscopic properties, which facilitate the formation of a stable hydration layer with low friction. The zwitterionic-functionalized CMC incorporates an additional negative sulfone group and increased negative charge density in the carboxyl group. This augmentation enhances electrostatic repulsion and facilitates the formation of hydration layer. This leads to exceptional prevention of blood clotting factor adhesion and inhibition of biofilm formation. Subsequently, the ZW@CMC hydrogel exhibited biocompatibility with tests of in vitro cytotoxicity, hemolysis, and catheter friction. Furthermore, in vivo tests of antithrombotic and systemic inflammation models with catheterization indicated that ZW@CMC has significant advantages for practical applications in cardiovascular-related and sepsis treatment. This study opens a new avenue for the development of chitosan-based multifunctional hydrogel for applications in blood-contacting devices.

What to Know about Antimicrobial Coatings in Arthroplasty: A Narrative Review

Periprosthetic joint infections (PJIs) are one of the most worrying complications orthopedic surgeons could face; thus, methods to prevent them are evolving. Apart from systemic antibiotics, targeted strategies such as local antimicrobial coatings applied to prosthetics have been introduced. This narrative review aims to provide an overview of the main antimicrobial coatings available in arthroplasty orthopedic surgery practice. The search was performed on the PubMed, Web of Science, SCOPUS, and EMBASE databases, focusing on antimicrobial-coated devices used in clinical practice in the arthroplasty world. While silver technology has been widely adopted in the prosthetic oncological field with favorable outcomes, recently, silver associated with hydroxyapatite for cementless fixation, antibiotic-loaded hydrogel coatings, and iodine coatings have all been employed with promising protective results against PJIs. However, challenges persist, with each material having strengths and weaknesses under investigation. Therefore, this narrative review emphasizes that further clinical studies are needed to understand whether antimicrobial coatings can truly revolutionize the field of PJIs.

Role of Dithiothreitol in Detection of Orthopaedic Implant-Associated Infections

Orthopaedic implant-associated infections (OIAIs) represent a notable complication of contemporary surgical procedures, exerting a considerable impact on patient outcomes and escalating healthcare expenditures. Prompt diagnosis holds paramount importance in managing OIAIs, with sonication widely acknowledged as the preferred method for detecting biofilm-associated infections. Recently, dithiothreitol (DTT) has emerged as a potential substitute for sonication, owing to its demonstrated ability to impede biofilm formation. This study aimed to compare the efficacy of DTT with sonication in identifying microorganisms within implants. Conducted as a prospective cohort investigation, the study encompassed two distinct groups: patients with suspected infections undergoing implant removal (Group A) and those slated for hardware explantation (Group B). Hardware segments were assessed for biofilm-related microorganisms using both sonication and DTT, with a comparative analysis of the two methods. A total of 115 patients were enrolled. In Group A, no statistically significant disparity was observed between DTT and sonication. DTT exhibited a sensitivity of 89.47% and specificity of 96.3%. Conversely, in Group B, both DTT and sonication fluid cultures yielded negative results in all patients. Consequently, this investigation suggests that DTT holds comparable efficacy to sonication in detecting OIAIs, offering a novel, cost-effective, and readily accessible diagnostic modality for identifying implant-associated infections.

Potential Exploration of Biocompatible Carbon-Coated MoSe2 Nanoparticles for Exploration of the Photothermal Potential in the Treatment of Human Choriocarcinoma

Background

Molybdenum diselenide (MoSe2), as a nano near-infrared absorber, has been widely studied in the field of photothermal therapy of cancer. However, there is little research on its application in the treatment of human choriocarcinoma.

Methods and Results

In this paper, a new type of carbon-coated MoSe2 (MEC) nanoparticles was prepared by a one-step hydrothermal method. The chemical characterization including SEM, TEM, EDS, XRD, FT-IR, TGA, Roman, and XPS showed that MEC was successfully synthesized. MEC exhibited a high photothermal conversion efficiency (50.97%) and extraordinary photothermal stability under laser irradiation. The cell experiment results showed that MEC had good biocompatibility on normal cells while significant photothermal effect on human choriocarcinoma (JEG-3) cells, achieving a good anticancer effect. The level of reactive oxygen species (ROS) in JEG-3 cells was significantly increased under the combination of MEC nanoparticles and near-infrared radiation. MEC nanoparticles could induce apoptosis of JEG-3 cells in combination with near-infrared radiation. Finally, transcriptomic analysis verified that MEC combined with laser radiation could inhibit DNA replication and induce apoptosis, thus improving its therapeutic effect on human choriocarcinoma.

Conclusion

MEC nanoparticles exert an excellent photothermal effect and may become an important candidate drug for the treatment of human choriocarcinoma.

Recent Advances in Antibacterial Coatings to Combat Orthopedic Implant-Associated Infections

Implant-associated infections (IAIs) represent a major health burden due to the complex structural features of biofilms and their inherent tolerance to antimicrobial agents and the immune system. Thus, the viable options to eradicate biofilms embedded on medical implants are surgical operations and long-term and repeated antibiotic courses. Recent years have witnessed a growing interest in the development of robust and reliable strategies for prevention and treatment of IAIs. In particular, it seems promising to develop materials with anti-biofouling and antibacterial properties for combating IAIs on implants. In this contribution, we exclusively focus on recent advances in the development of modified and functionalized implant surfaces for inhibiting bacterial attachment and eventually biofilm formation on orthopedic implants. Further, we highlight recent progress in the development of antibacterial coatings (including self-assembled nanocoatings) for preventing biofilm formation on orthopedic implants. Among the recently introduced approaches for development of efficient and durable antibacterial coatings, we focus on the use of safe and biocompatible materials with excellent antibacterial activities for local delivery of combinatorial antimicrobial agents for preventing and treating IAIs and overcoming antimicrobial resistance.

Titanium-Doped Diamond-like Carbon Layers as a Promising Coating for Joint Replacements Supporting Osteogenic Differentiation of Mesenchymal Stem Cells

Diamond-like carbon (DLC) layers are known for their high corrosion and wear resistance, low friction, and high biocompatibility. However, it is often necessary to dope DLC layers with additional chemical elements to strengthen their adhesion to the substrate. Ti-DLC layers (doped with 0.4, 2.1, 3.7, 6.6, and 12.8 at.% of Ti) were prepared by dual pulsed laser deposition, and pure DLC, glass, and polystyrene (PS) were used as controls. In vitro cell-material interactions were investigated with an emphasis on cell adhesion, proliferation, and osteogenic differentiation. We observed slightly increasing roughness and contact angle and decreasing surface free energy on Ti-DLC layers with increasing Ti content. Three-week biological experiments were performed using adipose tissue-derived stem cells (ADSCs) and bone marrow mesenchymal stem cells (bmMSCs) in vitro. The cell proliferation activity was similar or slightly higher on the Ti-doped materials than on glass and PS. Osteogenic cell differentiation on all materials was proved by collagen and osteocalcin production, ALP activity, and Ca deposition. The bmMSCs exhibited greater initial proliferation potential and an earlier onset of osteogenic differentiation than the ADSCs. The ADSCs showed a slightly higher formation of focal adhesions, higher metabolic activity, and Ca deposition with increasing Ti content.

Fabrication and evaluation of silver modified micro/nano structured titanium implant

In order to enhance the antibacterial property of titanium implant without inducing obvious cytotoxicity, the combination of Ag nanolayer and micro/nano surface structure was conducted by magnetron sputtering and hot-alkali treatment in this study. A series of specimens (AH-Ti, AH-Ti/Ag0.25, AH-Ti/Ag1, AH-Ti/Ag2, and AH-Ti/Ag5) were prepared with different sputtering durations (0 min, 0.25 min, 1 min, 2 min, 5 min), respectively, all realizing long-term release of Ag+. In vitro experiments indicated that AH-Ti/Ag1 group possessed good cytocompatibility, nice osteogenic ability, and excellent antibacterial efficiency as well. In addition, AH-Ti/Ag0.25 showed good biocompatibility, while the reduction of S.aureus (78.5%) was not enough compared with AH-Ti/Ag1. Although the AH-Ti/Ag2 and AH-Ti/Ag5 group showed superior antibacterial activity, their obvious cytotoxicity caused low ALP and mineralization level. Therefore, the design of suitable Ag nanolayer coating combined with micro/nano surface structure (AH-Ti/Ag1) might be a promising strategy to enhance osteogenic property and maintain excellent antibacterial ability at the same time.

A strategy for enhancing bioactivity and osseointegration with antibacterial effect by incorporating magnesium in polylactic acid based biodegradable orthopedic implant

Biodegradable orthopedic implants are essential for restoring the physiological structure and function of bone tissue while ensuring complete degradation after recovery. Polylactic acid (PLA), a biodegradable polymer, is considered a promising material due to its considerable mechanical properties and biocompatibility. However, further improvements are necessary to enhance the mechanical strength and bioactivity of PLA for reliable load-bearing orthopedic applications. In this study, a multifunctional PLA-based composite was fabricated by incorporating tricalcium phosphate (TCP) microspheres and magnesium (Mg) particles homogenously at a volume fraction of 40 %. This approach aims to enhance mechanical strength, accelerate pore generation, and improve biological and antibacterial performance. Mg content was incorporated into the composite at varying values of 1, 3, and 5 vol% (referred to as PLA/TCP-1 Mg, PLA/TCP-3 Mg, and PLA/TCP-5 Mg, respectively). The compressive strength and stiffness were significantly enhanced in all composites, reaching 87.7, 85.9, and 84.1 MPa, and 2.7, 3.0, and 3.1 GPa, respectively. The degradation test indicated faster elimination of the reinforcers as the Mg content increased, resulting in accelerated pore generation to induce enhanced osseointegration. Because PLA/TCP-3 Mg and PLA/TCP-5 Mg exhibited cracks in the PLA matrix due to rapid corrosion of Mg forming corrosion byproducts, to optimize the Mg particle content, PLA/TCP-1 Mg was selected for further evaluation. As determined by in vitro biological and antibacterial testing, PLA/TCP-1 Mg showed enhanced bioactivity with pre-osteoblast cells and exhibited antibacterial properties by suppressing bacterial colonization. Overall, the multifunctional PLA/TCP-Mg composite showed improved mechanobiological performance, making it a promising material for biodegradable orthopedic implants.

Titanium Alloy Implants with Lattice Structures for Mandibular Reconstruction

In recent years, the field of mandibular reconstruction has made great strides in terms of hardware innovations and their clinical applications. There has been considerable interest in using computer-aided design, finite element modelling, and additive manufacturing techniques to build patient-specific surgical implants. Moreover, lattice implants can mimic mandibular bone's mechanical and structural properties. This article reviews current approaches for mandibular reconstruction, their applications, and their drawbacks. Then, we discuss the potential of mandibular devices with lattice structures, their development and applications, and the challenges for their use in clinical settings.

Recent Progress in antibacterial hydrogel coatings for targeting biofilm to prevent orthopedic implant-associated infections

The application of orthopedic implants for bone tissue reconstruction and functional restoration is crucial for patients with severe bone fractures and defects. However, the abiotic nature of orthopedic implants allows bacterial adhesion and colonization, leading to the formation of bacterial biofilms on the implant surface. This can result in implant failure and severe complications such as osteomyelitis and septic arthritis. The emergence of antibiotic-resistant bacteria and the limited efficacy of drugs against biofilms have increased the risk of orthopedic implant-associated infections (OIAI), necessitating the development of alternative therapeutics. In this regard, antibacterial hydrogels based on bacteria repelling, contact killing, drug delivery, or external assistance strategies have been extensively investigated for coating orthopedic implants through surface modification, offering a promising approach to target biofilm formation and prevent OIAI. This review provides an overview of recent advancements in the application of antibacterial hydrogel coatings for preventing OIAI by targeting biofilm formation. The topics covered include: (1) the mechanisms underlying OIAI occurrence and the role of biofilms in exacerbating OIAI development; (2) current strategies to impart anti-biofilm properties to hydrogel coatings and the mechanisms involved in treating OIAI. This article aims to summarize the progress in antibacterial hydrogel coatings for OIAI prevention, providing valuable insights and facilitating the development of prognostic markers for the design of effective antibacterial orthopedic implants.

Shaping the Future of Antimicrobial Therapy: Harnessing the Power of Antimicrobial Peptides in Biomedical Applications

Antimicrobial peptides (AMPs) have emerged as a promising class of bioactive molecules with the potential to combat infections associated with medical implants and biomaterials. This review article aims to provide a comprehensive analysis of the role of antimicrobial peptides in medical implants and biomaterials, along with their diverse clinical applications. The incorporation of AMPs into various medical implants and biomaterials has shown immense potential in mitigating biofilm formation and preventing implant-related infections. We review the latest advancements in biomedical sciences and discuss the AMPs that were immobilized successfully to enhance their efficacy and stability within the implant environment. We also highlight successful examples of AMP coatings for the treatment of surgical site infections (SSIs), contact lenses, dental applications, AMP-incorporated bone grafts, urinary tract infections (UTIs), medical implants, etc. Additionally, we discuss the potential challenges and prospects of AMPs in medical implants, such as effectiveness, instability and implant-related complications. We also discuss strategies that can be employed to overcome the limitations of AMP-coated biomaterials for prolonged longevity in clinical settings.

Immune response to foreign materials in spinal fusion surgery

Spinal fusion surgery is a common procedure used to stabilize the spine and treat back pain. The procedure involves the use of foreign materials such as screws, rods, or cages, which can trigger a foreign body reaction, an immune response that involves the activation of immune cells such as macrophages and lymphocytes. The foreign body reaction can impact the success of spinal fusion, as it can interfere with bone growth and fusion. This review article provides an overview of the cellular and molecular events in the foreign body reaction, the impact of the immune response on spinal fusion, and strategies to minimize its impact. By carefully considering the use of foreign materials and optimizing surgical techniques, the impact of the foreign body reaction can be reduced, leading to better outcomes for patients.

Polyetheretherketone implants with hierarchical porous structure for boosted osseointegration

BACKGROUND

Good osseointegration is the key to the long-term stability of bone implants. Thermoplastic polyetheretherketone (PEEK) has been widely used in orthopedics; however, its inherent biological inertia causes fibrous tissue to wrap its surface, which leads to poor osseointegration and thus greatly limits its clinical applications.

METHODS

Herein, we developed a facile yet effective surface modification strategy. A commonly used sulfonation coupled with "cold pressing" treatment in the presence of porogenic agent formed a three-dimensional hierarchical porous structure on PEEK surface. Subsequently, the effects of porous surface on the in vitro adhesion, proliferation and differentiation of rat bone marrow-derived mesenchymal stem cells (BMSCs) were evaluated. Finally, the osteoinduction and osseointegration of surface-porous PEEK implant were examined in the rat distal femoral defect model.

RESULTS

In vitro results showed that the surface modification did not significantly affect the mechanical performance and cytocompatibility of PEEK substance, and the porous structure on the modified PEEK substrate provided space for cellular ingrowth and enhanced osteogenic differentiation and mineralization of BMSCs. In vivo tests demonstrated that the surface-porous PEEK implant could effectively promote new bone formation and had higher bone-implant contact rate, thereby achieving good bone integration with the surrounding host bone. In addition, this modification technique was also successfully demonstrated on a medical PEEK interbody fusion cage.

CONCLUSION

The present study indicates that topological morphology plays a pivotal role in determining implant osseointegration and this facile and effective modification strategy developed by us is expected to achieve practical applications quickly.

Progress in Surface Modification of Titanium Implants by Hydrogel Coatings

Although titanium and titanium alloys have become the preferred materials for various medical implants, surface modification technology still needs to be strengthened in order to adapt to the complex physiological environment of the human body. Compared with physical or chemical modification methods, biochemical modification, such as the introduction of functional hydrogel coating on implants, can fix biomolecules such as proteins, peptides, growth factors, polysaccharides, or nucleotides on the surface of the implants, so that they can directly participate in biological processes; regulate cell adhesion, proliferation, migration, and differentiation; and improve the biological activity on the surface of the implants. This review begins with a look at common substrate materials for hydrogel coatings on implant surfaces, including natural polymers such as collagen, gelatin, chitosan, and alginate, and synthetic materials such as polyvinyl alcohol, polyacrylamide, polyethylene glycol, and polyacrylic acid. Then, the common construction methods of hydrogel coating (electrochemical method, sol-gel method and layer-by-layer self-assembly method) are introduced. Finally, five aspects of the enhancement effect of hydrogel coating on the surface bioactivity of titanium and titanium alloy implants are described: osseointegration, angiogenesis, macrophage polarization, antibacterial effects, and drug delivery. In this paper, we also summarize the latest research progress and point out the future research direction. After searching, no previous relevant literature reporting this information was found.

Improved osteogenic activity of NiTi orthopedic implant by HAp-Nb2O5 composite coatings: Materials and biological points of view

The surface properties of NiTi, as an interface between the synthetic implant and living tissue, play a vital role in guaranteeing implantation success, especially during the initial stage. This contribution endeavors to enhance the surface features of NiTi orthopedic implants through the application of HAp-based coatings, placing emphasis on assessing the influence of Nb₂O₅ particles concentration in the electrolyte on resultant properties of HAp-Nb₂O₅ composite electrodeposits. The coatings were electrodeposited via pulse current mode under galvanostatic current control from an electrolyte containing 0-1 g/L of Nb₂O₅ particles. Surface morphology, topography, and phase composition were evaluated using FESEM, AFM, and XRD, respectively. EDS was employed to study surface chemistry. In vitro biomineralization and osteogenic activity of the samples were studied by immersing the samples in SBF and incubating them with osteoblastic SAOS-2 cells, respectively. The added Nb₂O₅ particles, at the optimum concentration, stimulated biomineralization, suppressed the Ni ion leaching, and improved SAOS-2 cell adhesion and proliferation. NiTi implant coated by HAp-0.50 g/L Nb₂O₅ layer showed tremendous osteogenic properties. Overall, the HAp-Nb₂O₅ composite layers bring forth fascinating coating in vitro biological performance, reducing Ni leaching, and promoting osteogenic activity, which are fundamental for the successful use of NiTi in vivo.

A dual functional Ti-Ga alloy: inhibiting biofilm formation and osteoclastogenesis differentiation via disturbing iron metabolism

BACKGROUND

Although biomedical implants have been widely used in orthopedic treatments, two major clinical challenges remain to be solved, one is the bacterial infection resulting in biofilm formation, and the other is aseptic loosening during implantation due to over-activated osteoclastogenesis. These factors can cause many clinical issues and even lead to implant failure. Thus, it is necessary to endow implants with antibiofilm and aseptic loosening-prevention properties, to facilitate the integration between implants and bone tissues for successful implantation. To achieve this goal, this study aimed to develop a biocompatible titanium alloy with antibiofilm and anti-aseptic loosening dual function by utilizing gallium (Ga) as a component.

METHODS

A series of Ti-Ga alloys were prepared. We examined the Ga content, Ga distribution, hardness, tensile strength, biocompatibility, and anti-biofilm performance in vitro and in vivo. We also explored how Ga³⁺ ions inhibited the biofilm formation of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) and osteoclast differentiation.

RESULTS

The alloy exhibited outstanding antibiofilm properties against both S. aureus and E. coli in vitro and decent antibiofilm performance against S. aureus in vivo. The proteomics results demonstrated that Ga³⁺ ions could disturb the bacterial Fe metabolism of both S. aureus and E. coli, inhibiting bacterial biofilm formation. In addition, Ti-Ga alloys could inhibit receptor activator of nuclear factor-κB ligand (RANKL)-dependent osteoclast differentiation and function by targeting iron metabolism, then suppressing the activation of the NF-κB signaling pathway, thus, showing their potential to prevent aseptic loosening.

CONCLUSION

This study provides an advanced Ti-Ga alloy that can be used as a promising orthopedic implant raw material for various clinical scenarios. This work also revealed that iron metabolism is the common target of Ga³⁺ ions to inhibit biofilm formation and osteoclast differentiation.

Multifunctional antibacterial chitosan-based hydrogel coatings on Ti6Al4V biomaterial for biomedical implant applications

Among biomedical community, great efforts have been realized to develop antibacterial coatings that avoid implant-associated infections. To date, conventional mono-functional antibacterial strategies have not been effective enough for successful long-term implantations. Consequently, researchers have recently focused their attention on novel bifunctional or multifunctional antibacterial coatings, in which two or more antibacterial mechanisms interact synergistically. Thus, in this work different chitosan-based (CHI) hydrogel coatings were created on Ti6Al4V surface using genipin (Ti-CHIGP) and polyethylene glycol (Ti-CHIPEG) crosslinking agents. Hydrogel coatings demonstrated an exceptional in vivo biocompatibility plus a remarkable ability to promote cell proliferation and differentiation. Lastly, hydrogel coatings demonstrated an outstanding bacteria-repelling (17-28 % of S. aureus and 33-43 % of E. coli repelled) and contact killing (186-222 % of S. aureus and 72-83 % of E. coli damaged) ability. Such bifunctional antibacterial activity could be further improved by the controlled release of drugs resulting in powerful multifunctional antibacterial coatings.

Peri-implantation tissue reactions during the insertion of contaminated implants with a composite antibacterial coating

Background. Protection against microbial colonization of surface fixators for osteosynthesis reduces the number of infectious complications. The aim of the study was to assess the biological compatibility of implants with a composite antibacterial coating under microbial load. Methods. Fragments of steel carpal pins with four-component antimicrobial coating based on polylactide, polyurethane, ciprofloxacin and silver nanoparticles were contaminated by methicillin resistant Staphylococcus aureus. They were implanted in rats within the quadriceps femoris. Contaminated uncoated pins were used as a control. The animals were withdrawn from the experiment on the 2nd, 4th, 7th day after implantation. Pathohistological tissue specimens of the periimplantation zone were prepared. A semiquantitative assessment of periimplantation tissue reactions was performed. Results. The microbial load was (1,120,26)*106 S. aureus cells for the control implants and (0,860,31)*106 cells for implants with antibacterial coating. Tissue inflammatory reactions on the second day of implantation were equally evident in the control and investigated groups. There was a significant reduction in the number of immune cells and necrotic detritus, as well as increased growth of connective tissue and neoangiogenesis in the experimental group by the 4th day. The appearance of a less pronounced well-vascularized fibrous capsule around the experimental implants was noted by the 7th day. It indicates a more favorable healing of soft tissues in comparison with the control. Conclusions. Weak morphological manifestations of tissue reactions in response to the fitting of contaminated implants with an antibacterial coating can be associated with both the direct antimicrobial effect of the coating components and the anti-inflammatory activity of silver nanoparticles and ciprofloxacin included in its composition. Keywords: implants, antibacterial coating, ciprofloxacin, silver nanoparticles, Staphylococcus aureus, contamination, tissue reactions.

Biominerals Added Bioresorbable Calcium Phosphate Loaded Biopolymer Composites

Nanocrystalline calcium phosphate (CP) bioceramic coatings and their combination with biopolymers are innovative types of resorbable coatings for load-bearing implants that can promote the integration of metallic implants into human bodies. The nanocrystalline, amorphous CP particles are an advantageous form of the various calcium phosphate phases since they have a faster dissolution rate than that of crystalline hydroxyapatite. Owing to the biomineral additions (Mg, Zn, Sr) in optimized concentrations, the base CP particles became more similar to the mineral phase in human bones (dCP). The effect of biomineral addition into the CaP phases was thoroughly studied. The results showed that the shape, morphology, and amorphous characteristic slightly changed in the case of biomineral addition in low concentrations. The optimized dCP particles were then incorporated into a chosen polycaprolactone (PCL) biopolymer matrix. Very thin, non-continuous, rough layers were formed on the surface of implant substrates via the spin coating method. The SEM elemental mapping proved the perfect incorporation and distribution of dCP particles into the polymer matrix. The bioresorption rate of thin films was followed by corrosion measurements over a long period of time. The corrosion results indicated a faster dissolution rate for the dCP-PCL composite compared to the dCP and CP powder layers.

Natural Coatings and Surface Modifications on Magnesium Alloys for Biomedical Applications

Magnesium (Mg) alloys have great potential in biomedical applications due to their incomparable properties regarding other metals, such as stainless steels, Co-Cr alloys, and titanium (Ti) alloys. However, when Mg engages with body fluids, its degradation rate increases, inhibiting the complete healing of bone tissue. For this reason, it has been necessary to implement protective coatings to control the rate of degradation. This review focuses on natural biopolymer coatings used on Mg alloys for resorbable biomedical applications, as well as some modification techniques implemented before applying natural polymer coatings to improve their performance. Issues such as improving the corrosion resistance, cell adhesion, proliferation, and biodegradability of natural biopolymers are discussed through their basic comparison with inorganic-type coatings. Emphasis is placed on the expected biological behavior of each natural polymer described, to provide basic information as a reference on this topic.

Behavior of Calcium Phosphate-Chitosan-Collagen Composite Coating on AISI 304 for Orthopedic Applications

Calcium phosphate/chitosan/collagen composite coating on AISI 304 stainless steel was investigated. Coatings were realized by galvanic coupling that occurs without an external power supply because it begins with the coupling between two metals with different standard electrochemical potentials. The process consists of the co-deposition of the three components with the calcium phosphate crystals incorporated into the polymeric composite of chitosan and collagen. Physical-chemical characterizations of the samples were executed to evaluate morphology and chemical composition. Morphological analyses have shown that the surface of the stainless steel is covered by the deposit, which has a very rough surface. XRD, Raman, and FTIR characterizations highlighted the presence of both calcium phosphate compounds and polymers. The coatings undergo a profound variation after aging in simulated body fluid, both in terms of composition and structure. The tests, carried out in simulated body fluid to scrutinize the corrosion resistance, have shown the protective behavior of the coating. In particular, the corrosion potential moved toward higher values with respect to uncoated steel, while the corrosion current density decreased. This good behavior was further confirmed by the very low quantification of the metal ions (practically absent) released in simulated body fluid during aging. Cytotoxicity tests using a pre-osteoblasts MC3T3-E1 cell line were also performed that attest the biocompatibility of the coating.

Numerical Analysis of Zirconium and Titanium Implants under the Effect of Critical Masticatory Load

Dental implants have become an alternative to replace the teeth of people suffering from edentulous and meet the physiological and morphological characteristics (recovering 95% of the chewing function). The evolution and innovation of biomaterials for dental implants have had a trajectory that dates back to prehistory, where dental pieces were replaced by ivory or seashells, to the present day, where they are replaced by metallic materials such as titanium or ceramics such as zirconium or fiberglass. The numerical evaluation focuses on comparing the stress distribution and general displacement between different dental implants and a healthy tooth when applying a force of 850 N. For the analysis, a model of the anatomical structure was developed of a healthy tooth considering three essential parts of the tooth (enamel, dentin, and pulp). The tooth biomodel was established through computed tomography. Three dental implant models were considered by changing the geometry of the abutment. A structural simulation was carried out by applying the finite element method (FEM). In addition, the material considered for the analyses was zirconium oxide (ZrO2), which was compared against titanium alloy (Ti6Al4V). The analyses were considered with linear, isotropic, and homogeneous properties. The variables included in the biomodeling were the modulus of elasticity, Poisson's ratio, density, and elastic limit. The results obtained from the study indicated a significant difference in the biomechanical behavior of the von Mises forces and the displacement between the healthy tooth and the titanium and zirconium implant models. However, the difference between the titanium implant and the zirconium implant is minimal because one is more rigid, and the other is more tenacious.

Preparation and Properties of Partial-Degradable ZrO2-Chitosan Particles-GelMA Composite Scaffolds

In the field of bone repair, the inorganic-organic composite scaffold is a promising strategy for mimicking the compositions of the natural bone. In addition, as implants for repairing load-bearing sites, an inert permanent bone substitute composites with bioactive degradable ingredients may make full use of the composite scaffold. Herein, the porous zirconia (ZrO₂) matrix was prepared via the template replication method, and the partial degradable ZrO₂-chitosan particles-GelMA composite scaffolds with different chitosan/GelMA volume ratios were prepared through the vacuum infiltration method. Dynamic light scattering (DLS) and the scanning electron microscope (SEM) were adopted to observe the size of the chitosan particles and the morphologies of the composites scaffold. The mechanical properties, swelling properties, and degradation properties of the composite scaffolds were also characterized by the mechanical properties testing machine and immersion tests. The CCK-8 assay was adopted to test the biocompatibility of the composite scaffold preliminarily. The results show that chitosan particles as small as 60 nm were obtained. In addition, the ratio of chitosan/GelMA can influence the mechanical properties and the swelling and degradation behaviors of the composites scaffold. Furthermore, improved cell proliferation performance was obtained for the composite scaffolds.