Implant-associated Infections Research Articles

Emerging Strategies to Prevent Bacterial Infections on Titanium-Based Implants.

Titanium and titanium alloys remain the gold standard for dental and orthopedic implants. These materials are heavily used because of their bioinert nature, robust mechanical properties, and seamless integration with bone. However, implant-associated infections (IAIs) remain one of the leading causes of implant failure. Eradicating an IAI can be difficult since bacteria can form biofilms on the medical implant, protecting the bacterial cells against systemic antibiotics and the host's immune system. If the infection is not treated promptly and aggressively, device failure is inevitable, leading to costly multi-step revision surgeries. To circumvent this dire situation, scientists and engineers continue to develop novel strategies to protect the surface of medical implants from bacteria. In this review, details on emerging strategies to prevent infection in titanium implants are reported. These strategies include anti-adhesion properties provided by polymers, superhydrophobic, superhydrophilic, and liquid-infused surface coatings, as well as strategies and coatings employed to lyse the bacteria. Additionally, commercially available technologies and those under preclinical trials are examined while discussing current and future trends.

Macrophage-to-osteocyte communication: Impact in a 3D in vitro implant-associated infection model

Macrophages and osteocytes are important regulators of inflammation, osteogenesis and osteoclastogenesis. However, their interactions under adverse conditions, such as biomaterial-associated infection (BAI) are not fully understood. We aimed to elucidate how factors released from macrophages modulate osteocyte responses in an in vitro indirect 3D co-culture model. Human monocyte-derived macrophages were cultured on etched titanium disks and activated with either IL-4 cytokine (anti-inflammatory M2 phenotype) or Staphylococcus aureus secreted virulence factors to simulate BAI (pro-inflammatory M1 phenotype). Primary osteocytes in collagen gels were then stimulated with conditioned media (CM) from these macrophages. The osteocyte response was analyzed by gene expression, protein secretion, and immunostaining. M1 phenotype macrophages were confirmed by IL-1β and TNF-α secretion, and M2 macrophages by ARG-1 and MRC-1.Osteocytes receiving M1 CM revealed bone inhibitory effects, denoted by reduced secretion of bone formation osteocalcin (BGLAP) and increased secretion of the bone inhibitory sclerostin (SOST). These osteocytes also downregulated the pro-mineralization gene PHEX and upregulated the anti-mineralization gene MEPE. Additionally, exhibited pro-osteoclastic potential by upregulating pro-osteoclastic gene RANKL expression. Nonetheless, M1-stimulated osteocytes expressed a higher level of the potent pro-osteogenic factor BMP-2 in parallel with the downregulation of the bone inhibitor genes DKK1 and SOST, suggesting a compensatory feedback mechanisms. Conversely, M2-stimulated osteocytes mainly upregulated anti-osteoclastic gene OPG expression, suggesting an anti-catabolic effect. Altogether, our findings demonstrate a strong communication between M1 macrophages and osteocytes under M1 (BAI)-simulated conditions, suggesting that the BAI adverse effects on osteoblastic and osteoclastic processes in vitro are partly mediated via this communication. Statement of significanceBiomaterial-associated infections are major challenges and the underlying mechanisms in the cellular interactions are missing, especially among the major cells from the inflammatory side (macrophages as the key cell in bacterial clearance) and the regenerative side (osteocyte as main regulator of bone). We evaluated the effect of macrophage polarization driven by the stimulation with bacterial virulence factors on the osteocyte function using an indirect co-culture model, hence mimicking the scenario of a biomaterial-associated infection. The results suggest that at least part of the adverse effects of biomaterial associated infection on osteoblastic and osteoclastic processes in vitro are mediated via macrophage-to-osteocyte communication.

Osseointegrative and antimicrobial properties of graphene oxide nano coated dental implants: A systematic review.

Osseointegration stands as a pivotal concept within the realm of dental implants, signifying the intricate process through which a dental implant integrates with the adjoining bone tissue. Graphene oxide (GO) has been shown to promote osseointegration, the process by which the implant fuses with the surrounding bone. The objective of this study was to assess the osseointegrative and antimicrobial properties of GO nano coated dental implants. A systematic search was conducted using electronic databases (e.g., PubMed, Scopus, Web of Science) to identify relevant studies published. Inclusion criteria encompassed studies that evaluated the effects of GO nano coating on osseointegrative and antimicrobial characteristics of dental implants. Studies not written in English and published before 2012 were excluded. The initial search yielded a total of 127 potential studies, of which six met the inclusion criteria and five were included in the review. These studies provided data on GO nano coated dental implants and their osseointegrative and antimicrobial properties. All the included studies showed moderate risk of bias. None of the studies provided information related to sample size calculation or sampling technique. The findings from the included studies demonstrated that GO nano coating had a positive impact on osseointegrative properties of dental implants. Enhanced bone-implant contact and increased bone density were observed in animals and humans receiving GO nano coated implants. Furthermore, the antimicrobial properties of GO nano coating were found to inhibit bacterial colonization and biofilm formation on the implant surface, reducing the risk of implant-associated infections. The findings indicate that GO nano coating holds promise in enhancing the success rate and longevity of dental implants. However, more studies with larger sample sizes, are needed to further strengthen the evidence and determine the long-term effects of GO nano coated dental implants.

In vitro and in vivo evaluation of the layer-by-layer vancomycin with poly(ε-caprolactone) nanosphere-coated Schanz pins for prolonged release

In this research, the effect of layer-by-layer (spray and dip) coating followed by annealing of vancomycin (VCM) and poly(ε-caprolactone) nanospheres (PCLnp) on Schanz pins for prolonged antibacterial activity was investigated. Nanospheres were prepared using the high-pressure homogenizer method and characterized by both functional groups and particle size. The in vitro release profile revealed that after 28 days, the cumulative release of VCM from the VCM-PCLnp coated pins was 753.68 ± 0.19 μg. The coated pins released VCM at a concentration greater than the minimum inhibitory concentration (MIC) and sustained this release for 28 days. Irritation, hemolysis, sensitization, and cytotoxicity assays confirmed that VCM-PCLnp coated pins were highly biocompatible. Additionally, antibacterial assays against methicillin-resistant Staphylococcus aureus (MRSA) revealed prolonged antibacterial resistance. Specifically, the assays demonstrated effective inhibition of Staphylococcus aureus (S. aureus), including the methicillin-resistant strain. This approach involves coating the implants with antibiotics and polymeric nanospheres using a layer-by-layer (dip and spray) method to prolong their antibacterial activity. The results of this study show great promise for successfully treating implant-associated infections. Consequently, we recommend this method for coating other medical devices.

The Low-Abundance Plasma Proteome Reveals Differentially Abundant Proteins Associated with Breast Implant Capsular Contracture: A Pilot Study.

Capsular contracture (CC) is one of the most common postoperative complications associated with breast implant-associated infections. The mechanisms that lead to CC remain poorly understood. Plasma is an ideal biospecimen for early proteomics biomarker discovery. However, as high-abundance proteins mask signals from low-abundance proteins, identifying novel or specific proteins as biomarkers for a particular disease has been hampered. Here, we employed depletion of high-abundance plasma proteins followed by Tandem Mass Tag (TMT)-based quantitative proteomics to compare 10 healthy control patients against 10 breast implant CC patients. A total of 450 proteins were identified from these samples. Among them, 16 proteins were significantly differentially expressed in which 5 proteins were upregulated and 11 downregulated in breast implant CC patients compared to healthy controls. Gene Ontology enrichment analysis revealed that proteins related to cell, cellular processes and catalytic activity were highest in the cellular component, biological process, and molecular function categories, respectively. Further, pathway analysis revealed that inflammatory responses, focal adhesion, platelet activation, and complement and coagulation cascades were enriched pathways. The differentially abundant proteins from TMT-based quantitative proteomics have the potential to provide important information for future mechanistic studies and in the development of breast implant CC biomarkers.

Ultrasound-Activated Probiotics Vesicles Coating for Titanium Implant Infections Through Bacterial Cuproptosis-Like Death and Immunoregulation.

Implant-associated infections (IAIs) are the main cause of prosthetic implant failure. Bacterial biofilms prevent antibiotic penetration, and the unique metabolic conditions in hypoxic biofilm microenvironment may limit the efficacy of conventional antibiotic treatment. Escaping survival bacteria may not be continually eradicated, resulting in the recurrence of IAIs. Herein, a sonosensitive metal-organic framework of Cu-TCPP (tetrakis(4-carboxyphenyl) porphyrin) nanosheets and tinidazole doped probiotic-derived membrane vesicles (OMVs) with high-penetration sonodynamic therapy (SDT), bacterial metabolic state interference, and bacterial cuproptosis-like death to eradicate IAIs is proposed. The Cu-TCPP can convert O2 to toxic 1O2 through SDT in the normoxic conditions, enhancing the hypoxic microenvironment and activating the antibacterial activity of tinidazole. The released Cu(II) under ultrasound can be converted to Cu(I) by exogenous poly(tannic acid) (pTA) and endogenous glutathione. The disruption of the bacterial membrane by SDT can enhance the Cu(I) transporter activity. Transcriptomics indicate that the SDT-enhanced Cu(I) overload and hypoxia-activated therapy hinder the tricarboxylic acid cycle (TCA), leading to bacterial cuproptosis-like death. Moreover, the OMVs-activated therapy can polarize macrophages to a M2-like phenotype and facilitate bone repair. The sonodynamic biofilm microenvironment modulation strategy, whereby the hypoxia-enhanced microenvironment is potentiated to synergize SDT with OMVs-activated therapy, provides an effective strategy for antibacterial and osteogenesis performance.

Wireless Optogenetic Targeting Nociceptors Helps Host Cells Win the Competitive Colonization in Implant-Associated Infections.

The role of nociceptive nerves in modulating immune responses to harmful stimuli via pain or itch induction remains controversial. Compared to conventional surgery, various implant surgeries are more prone to infections even with low bacterial loads. In this study, an optogenetic technique is introduced for selectively activating peripheral nociceptive nerves using a fully implantable, wirelessly rechargeable optogenetic device. By targeting nociceptors in the limbs of awake, freely moving mice, it is found that activation induces anticipatory immunity in the innervated territory and enhances the adhesion of various host cells to the implant surface. This effect mediates acute immune cell-mediated killing of Staphylococcus aureus on implants and enables the host to win "implant surface competition" against Staphylococcus aureus. This finding provides new strategies for preventing and treating implant-associated infections.

Cutibacterium acnes invades submicron osteocyte lacuno-canalicular networks following implant-associated osteomyelitis.

Cutibacterium acnes, part of normal skin flora, is increasingly recognized as an opportunistic pathogen capable of causing chronic prosthetic joint infections (PJI) associated with total hip and knee arthroplasty. However, there is a paucity of literature examining the pathogenesis of C. acnes during PJI. To study this, we developed an implant-associated osteomyelitis murine model in which 8-10-week-old C57BL6 mice were subjected to transtibial implantation of titanium or stainless-steel L-shaped pins contaminated with C. acnes. Postsurgery, mice were killed on Days 14 and 28 for terminal assessments of (1) bacterial load in bone, implant, and internal organs (heart, spleen, kidney, and liver), (2) bone osteolysis (micro-CT), (3) abscess formation (histology), and (4) systematic electron microscopy (EM). In vitro scanning EM (SEM) confirmed that C. acnes can form biofilms on stainless-steel and titanium implants. In mice, C. acnes could persist for 28 days in the tibia. Also, we observed C. acnes dissemination to internal organs. C. acnes chronic osteomyelitis revealed markedly reduced bone osteolysis and abscess formation compared to Staphylococcus aureus infections. Importantly, transmission EM (TEM) investigation revealed the presence of C. acnes within canaliculi, demonstrating that C. acnes can invade the osteocyte lacuno-canalicular networks (OLCN) within bone. Our preliminary pilot study, for the first time, revealed that the OLCN in bone can be a reservoir for C. acnes and potentially provides a novel mechanism of why C. acnes chronic implant-associated bone infections are difficult to treat.

Microbiological profile of patients with orthopedic implant-associated infection in the post-COVID period

Background. The etiological structure of implant-associated infection and antibiotic resistance of pathogens are important when choosing empirical antibiotic therapy. COVID-19 pandemic and increased consumption of antibiotics by the population could provoke an increase in antibiotic resistance.The aim of the work. To compare the spectrum of leading pathogens of implantassociated infection in the pre- and post-Covid period and to assess antibiotic resistance.Materials and methods. A continuous retrospective study of biomaterial samples from traumatology and orthopedic patients with implant-associated infection was carried out for 2018–2019 and 2021–2022. The sample consisted of 548 microorganism strains (n = 237 and n = 317, respectively) in 442 cases of infectious complications. The antibiotic resistance of all isolated microorganisms, including those from microbial associations, was assessed.Results. The leading pathogen of monomicrobial implant-associated infection in both study periods was Staphylococcus epidermidis (33–37 %). In 2021–2022, the proportion of microbial associations increased (from 12.5 to 17.5 %; p = 0.147) with the appearance of fungi in the microbial landscape. In the post-Covid period, the increase in Staphylococcus aureus resistance to tetracycline and doxycycline was revealed; the isolation of methicillin-resistant strains among Staphylococcus aureus decreased from 4 cases (out of 187) to 3 (out of 232); 100 % sensitivity to rifampicin and co-trimoxazole was maintained. An increase in Staphylococcus epidermidis resistance to all tested antibiotics was detected (statistically significant increase in resistance to fluoroquinolones; p = 0.002–0.003) with the isolation of methicillin-resistant strains in 80.5% and 80.9% of cases, respectively. All staphylococcal isolates were susceptible to vancomycin and linezolid. Enterobacteriaceae representatives showed a decrease in resistance to carbapenems and an increase in resistance to co-trimoxazole; in Pseudomonas aeruginosa and Acinetobacter baumannii, there is an increase in resistance to carbapenems and fluoroquinolones. All gram-negative microorganisms were sensitive to colistin.Conclusion. The high frequency of isolation of methicillin-resistant staphylococci determines the choice of vancomycin for empirical therapy. Increasing resistance of staphylococci to fluoroquinolones may limit their use. Increasing resistance of gram-negative bacteria and a narrow spectrum of antibiotics acting on carbapenemase producers may reduce the effectiveness of therapy.

Plasmid-Mediated Spread of Carbapenem Resistance in Enterobacterales: A Three-Year Genome-Based Survey.

The worldwide emergence and dissemination of carbapenem-resistant Gram-negative bacteria (CRGNB) is a challenging problem of antimicrobial resistance today. Outbreaks with CRGNB have severe consequences for both the affected healthcare settings as well as the patients with infection. Thus, bloodstream infections caused by metallo-ß-lactamase-producing Enterobacterales can often have clinical implications, resulting in high mortality rates due to delays in administering effective treatment and the limited availability of treatment options. The overall threat of CRGNB is substantial because carbapenems are used to treat infections caused by ESBL-producing Enterobacterales which also exist with high frequency within the same geographical regions. A genome-based surveillance of 589 CRGNB from 61 hospitals across the federal state Hesse in Germany was implemented using next-generation sequencing (NGS) technology to obtain a high-resolution landscape of carbapenem-resistant isolates over a three-year period (2017-2019). The study examined all reportable CRGNB isolates submitted by participating hospitals. This included isolates carrying known carbapenemases (435) together with carbapenem-resistant non-carbapenemase producers (154). Predominant carbapenemase producers included Klebsiella pneumoniae, Escherichia coli, Citrobacter freundii and Acinetobacter baumannii. Over 80% of 375 carbapenem-resistant determinants including KPC-, NDM-, VIM- and OXA-48-like ones detected in 520 Enterobacterales were plasmid-encoded, and half of these were dominated by a few incompatibility (Inc) types, viz., IncN, IncL/M, IncFII and IncF(K). Our results revealed that plasmids play an extraordinary role in the dissemination of carbapenem resistance in the heterogeneous CRGNB population. The plasmids were also associated with several multispecies dissemination events and local outbreaks throughout the study period, indicating the substantial role of horizontal gene transfer in carbapenemase spread. Furthermore, due to vertical and horizontal plasmid transfer, this can have an impact on implant-associated infections and is therefore important for antibiotic-loaded bone cement and drug-containing devices in orthopedic surgery. Future genomic surveillance projects should increase their focus on plasmid characterization.

Bioinspired Hybrid Nanostructured PEEK Implant with Enhanced Antibacterial and Anti-inflammatory Synergy.

Implant-associated infections and excessive immune responses are two major postsurgical issues for successful implantation. However, conventional strategies including antibiotic treatment and inflammatory regulation are always compromised due to the comodification of various biochemical agents and instances of functional interference. It is imperative to provide implant surfaces with satisfactory antibacterial and anti-inflammatory properties. Here, a dual-effect nanostructured polyetheretherketone (PEEK) surface (NP@PDA/Zn) with bionic mechano-bactericidal nanopillars and immobilized immunomodulatory Zn2+ is designed. The constructed hybrid nanopillars display remarkable antibacterial performance against Gram-negative and Gram-positive strains through the synergy of physical and chemical bactericidal effects imposed by nanopillars and Zn2+. Meanwhile, the immunoregulatory property is evaluated through the investigation of macrophage polarization both in vitro and in vivo, and the results reveal that NP@PDA/Zn could downregulate the expression of M1-related cytokines and decrease the M1 macrophage recruitment to lower the inflammatory response. Notably, the surface exhibited exceptional biocompatibility with discerning biocidal activity between bacterial and mammalian cells and antioxidant performance that effectively scavenges ROS, minimizing potential cytotoxicity. Taken together, NP@PDA/Zn presents a convenient and promising strategy of combining synergistic bactericidal activity and inflammatory regulation without any mutual interference, which can support the development of multifunctional implant-associated materials.

Fishwaste Derived Hydroxyapatite Nanostructure Combined with Black Rice Wine for Potential Antioxidant and Antimicrobial Response.

Hospital-acquired infection remains a serious threat globally, due to development of resistance to conventional antibiotics, which necessitates the urge for alternative therapy. Green nanotechnology has emerged as a holistic approach to address antibiotic resistance by combining environmental sustainability with improved therapeutic outcome. Nanostructure hydroxyapatite (HAP) has received significant attention in therapeutic and regenerative purposes due to its porous scaffold structure and biocompatible nature. In the present study, hydroxyapatite (HAP) nanoparticle was fabricated from the fish scale waste of red snapper fish. Black rice wine (BRW) was extracted from black rice commonly termed as Karupu kavuni/forbidden rice known for its nutritious effects. The present study focused on encapsulation of BRW within HAP nanoparticles (HAP@BRW) and evaluated its potential against nosocomial infections. Spectral and microscopic characterization of HAP@BRW revealed uniform encapsulation of BRW in HAP nanoparticles, aggregated irregular-shaped morphology of size 117.6nm. Maximum release of BRW (72%) within 24h indicates HAP as suitable drug delivery system suitable for biomedical applications. Antimicrobial studies revealed that HAP@BRW exhibited potent bactericidal effect against MRSA, MSSA, and Pseudomonas aeruginosa. Furthermore, HAP@BRW significantly inhibited the biofilm forming ability of MSSA and P. aeruginosa. Rich antioxidant property of HAP@BRW might be due to the presence of rich source of total polyphenolic, flavonoid, and anthocyanin content in BRW. In vitro and in vivo toxicity studies revealed biocompatible nature of HAP@BRW. Antibiofilm, antimicrobial, antioxidant, and biocompatible nature of HAP@BRW makes it a promising candidate for coating medical implants to avoid implant-associated infections and nosocomial infections.

Factors affecting the course and prognosis of implant-associated infection caused by <i>Klebsiella</i> spp.

Background. The outcome of complex treatment of implant-associated infection (IAI) depends on various factors, but one of the most important is the etiology of the inflammatory process. Treatment of orthopedic infection caused by Gram-negative microorganisms in general and representatives of the family Enterobacteriaceae in particular causes many difficulties, one of which is the rapid growth of antibiotic resistance. Aim of the study — to evaluate the factors affecting the course and prognosis of implant-associated infection caused by Klebsiella spp. Methods. We performed a retrospective analysis of case histories of 85 patients who underwent treatment of IAI caused by Klebsiella spp. in the clinical departments of the center from January 1, 2017 to December 31, 2021. According to the results of the telephone survey, the patients were divided into 2 main groups depending on the outcome of the 2-year follow-up period determined in accordance with the Delphi criteria. Results. It was found that the prognosis was significantly worsened by the number of sanitizing surgical interventions in the anamnesis (p = 0.022), the need for sanitizing intervention in the early postoperative period (p0.001) and the presence of Klebsiella spp. growth in postoperative culture tests (p = 0.002), hypoalbuminemia on 7-14 days after the surgery (p = 0.008). The administration of trimethoprim-sulfamethoxazole for the outpatient treament stage significantly improved the outcome (p = 0.038), which is most likely due to a high proportion of polymicrobial associations — 69.5%. Conclusions. There is a statistically significant direct relationship between the probability of an unfavorable treatment outcome of patients with IAI caused by Klebsiella spp. and the number of sanitizing surgical interventions in the anamnesis, low serum albumin (g/l) on 7-14 days after the operation, revision intervention in the early postoperative period, positive growth of Klebsiella spp. in postoperative culture tests. The probability of a favorable outcome was increased by the prescription of trimethoprim-sulfamethoxazole for oral administration at the outpatient stage.

Tyrosol-gold nanoparticle functionalized acacia gum-PVA nanofibers for mitigation of Candida biofilm

Increasing incidences of fungal infections and prevailing antifungal resistance in healthcare settings has given rise to an antifungal crisis on a global scale. The members of the genus Candida, owing to their ability to acquire sessile growth, are primarily associated with superficial to invasive fungal infections, including the implant-associated infections. The present study introduces a novel approach to combat the sessile/biofilm growth of Candida by fabricating nanofibers using a nanoencapsulation approach. This technique involves the synthesis of tyrosol (TYS) functionalized chitosan gold nanocomposite, which is then encapsulated into PVA/AG polymeric matrix using electrospinning. The FESEM, FTIR analysis of prepared TYS-AuNP@PVA/AG NF suggested the successful encapsulation of TYS into the nanofibers. Further, the sustained and long-term stability of TYS in the medium was confirmed by drug release and storage stability studies. The prepared nanomats can absorb the fluid, as evidenced by the swelling index of the nanofibers. The growth and biofilm inhibition, as well as the disintegration studies against Candida, showed 60–70 % biofilm disintegration when 10 mg of TYS-AuNP@PVA/AG NF was used, hence confirming its biological effectiveness. Subsequently, the nanofibers considerably reduced the hydrophobicity index and ergosterol content of the treated cells. Considering the challenges associated with the inhibition/disruption of fungal biofilm, the fabricated nanofibers prove their effectiveness against Candida biofilm. Therefore, nanocomposite-loaded nanofibers have emerged as potential materials that can control fungal colonization and could also promote healing.

Increased biofilm formation in dual-strain compared to single-strain communities of Cutibacterium acnes

Cutibacterium acnes is a known opportunistic pathogen in orthopedic implant-associated infections (OIAIs). The species of C. acnes comprises distinct phylotypes. Previous studies suggested that C. acnes can cause single- as well as multi-typic infections, i.e. infections caused by multiple strains of different phylotypes. However, it is not known if different C. acnes phylotypes are organized in a complex biofilm community, which could constitute a multicellular strategy to increase biofilm strength and persistency. Here, the interactions of two C. acnes strains belonging to phylotypes IB and II were determined in co-culture experiments. No adverse interactions between the strains were observed in liquid culture or on agar plates; instead, biofilm formation in both microtiter plates and on titanium discs was significantly increased when combining both strains. Fluorescence in situ hybridization showed that both strains co-occurred throughout the biofilm. Transcriptome analyses revealed strain-specific alterations of gene expression in biofilm-embedded cells compared to planktonic growth, in particular affecting genes involved in carbon and amino acid metabolism. Overall, our results provide first insights into the nature of dual-type biofilms of C. acnes, suggesting that strains belonging to different phylotypes can form biofilms together with additive effects. The findings might influence the perception of C. acnes OIAIs in terms of diagnosis and treatment.

Multifunctional curcumin-based polymer coating: A promising platform against bacteria, inflammation and coagulation

The extensive use of polymers in the medical field has facilitated the development of various devices and implants, contributing to the restoration of organ function. However, despite their advantages such as biocompatibility and robustness, these materials often face challenges like bacterial contamination and subsequent inflammation, leading to implant-associated infections (IAI). Integrating implants effectively is crucial to prevent bacterial colonization and reduce inflammatory responses. To overcome these major issues, surface chemical modifications have been extensively explored. Indeed, click chemistry, and particularly, copper (I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction has emerged as a promising approach for surface functionalization without affecting material bulk properties. Curcumin, known for its diverse biological activities, suffers from low solubility and stability. To enhance its bioavailability, bioconjugation strategy has garnered attention in recent years. This study represents pioneering work in immobilizing curcumin derivative onto polyethylene terephthalate (PET) surfaces, aiming to combat bacterial adhesion, inflammation and coagulation. Before curcumin derivative bioconjugation, a fluorophore, dansyl derivative, was employed in order to monitor and determine the efficiency of the proposed methodology. Previous surface chemical modifications were required for the immobilization of both dansyl and curcumin derivatives. Ultraviolet-Visible (UV-Vis) demonstrated the amidation functionalization of PET surface. Other surface characterization techniques including X-ray Photoelectron Spectroscopy (XPS), Attenuated Total Reflectance Fourier Transformed Infrared (ATR-FTIR), Scanning Electron Microscopy (SEM) and contact angle, among others, confirmed also the conjugation of both dansyl and curcumin derivatives. On the other hand, different biological assays corroborated that curcumin derivative immobilized PET surfaces do not exhibit cytotoxicity effect. Additionally, corresponding inflammation test were performed, indicating that these polymeric surfaces do not produce inflammation and, when curcumin derivative is immobilized, they decrease the inflammation marker level (IL-6). Moreover, the bacterial growth of both Gram positive and Gram negative bacteria were measured, demonstrating that the immobilization of curcumin derivative on PET provided antibacterial properties to the material. Finally, hemolysis rate analysis and whole blood clotting assay demonstrated the antithrombogenic effect of PET-Cur surfaces as well as no hemolysis concern in the fabricated functional surfaces.

Investigating the translational value of Periprosthetic Joint Infection (PJI) models to determine the risk and severity of Staphylococcal biofilms.

With the advent of antibiotic-eluting polymeric materials for targeting recalcitrant infections, using preclinical models to study biofilm is crucial for improving the treatment efficacy in periprosthetic joint infections. The stratification of risk and severity of infections is needed to develop an effective clinical dosing framework with better outcomes. Here, using in-vivo and in-vitro implant-associated infection models, we demonstrate that methicillin-sensitive and resistant Staphylococcus aureus (MSSA and MRSA) have model-dependent distinct implant and peri-implant tissue colonization patterns. The maturity of biofilms and the location (implant vs tissue) were found to influence the antibiotic susceptibility evolution profiles of MSSA and MRSA and the models could capture the differing host-microbe interactions in vivo. Gene expression studies revealed the molecular heterogeneity of colonizing bacterial populations. The comparison and stratification of the risk and severity of infection across different preclinical models provided in this study can guide clinical dosing to effectively prevent or treat PJI.

Assessment of tissue response in vivo: PET-CT imaging of titanium and biodegradable magnesium implants

To study in vivo the bioactivity of biodegradable magnesium implants and other possible biomaterials, we are proposing a previously unexplored application of PET-CT imaging, using available tracers to follow soft tissue and bone remodelling and immune response in the presence of orthopaedic implants. Female Wistar rats received either implants (Ti6Al7Nb titanium or WE43 magnesium) or corresponding transcortical sham defects into the diaphyseal area of the femurs. Inflammatory response was followed with [18F]FDG and osteogenesis with [18F]NaF, over the period of 1.5 months after surgery. An additional pilot study with [68Ga]NODAGA-RGD tracer specific to αvβ3 integrin expression was performed to follow the angiogenesis for one month.[18F]FDG tracer uptake peaked on day 3 before declining in all groups, with Mg and Ti groups exhibiting overall higher uptake compared to sham. This suggests increased cellular activity and tissue response in the presence of Mg during the initial weeks, with Ti showing a subsequent increase in tracer uptake on day 45, indicating a foreign body reaction. [18F]NaF uptake demonstrated the superior osteogenic potential of Mg compared to Ti, with peak uptake on day 7 for all groups. [68Ga]NODAGA-RGD pilot study revealed differences in tracer uptake trends between groups, particularly the prolonged expression of αvβ3 integrin in the presence of implants.Based on the observed differences in the uptake trends of radiotracers depending on implant material, we suggest that PET-CT is a suitable modality for long-term in vivo assessment of orthopaedic biomaterial biocompatibility and underlying tissue reactions. Statement of significanceThe study explores the novel use of positron emission tomography for the assessment of the influence that biomaterials have on the surrounding tissues. Previous related studies have mostly focused on material-related effects such as implant-associated infections or to follow the osseointegration in prosthetics, but the use of PET to evaluate the materials has not been reported before. The approach tests the feasibility of using repeated PET-CT imaging to follow the tissue response over time, potentially improving the methodology for adopting new biomaterials for clinical use.

A novel antibacterial immune activator: Bi-MOF acts as H2S scavenger to suppress HIF-1α S-sulfhydration and alleviate implant-associated infection

Implant-associated infection (IAI) has significantly impeded the progress of surgery, and a properly functioning antibacterial immune response is critical for preventing persistent infection and reinfection. However, the efficacy of current infection immunotherapy remains considerably suboptimal, primarily because of the lack of validated therapeutic targets and interventions. Herein, we identify a bismuth-based metal organic frameworks (Bi-MOF) as an efficient intracellular hydrogen sulfide (H2S) scavenger that promotes the antibacterial response of macrophages through the inhibition of hypoxia inducible factor-1α (HIF-1α) S-sulfhydration and subsequent ubiquitin-dependent degradation. The reduction in H2S levels by Bi-MOF in vivo contributes to accelerated the clearance of bacteria, prevention of bone destruction, and augmentation of innate immunity in a mouse IAI model. Moreover, Bi-MOF also boost bacteria-specific adaptive immunity, thereby generating long-lasting protection against reinfection. Together, our results demonstrate that H2S-responsive Bi-MOF offer a promising immunotherapeutic approach as a potential alternative to antibiotics for managing stubborn IAIs.

SrTiO3 Nanotube-Based "Pneumatic Nanocannon" for On-Demand Delivery of Antibacterial and Sustained Osseointegration Enhancement.

Infection and aseptic loosening caused by bacteria and poor osseointegration remain serious challenges for orthopedic implants. The advanced surface modification of implants is an effective strategy for addressing these challenges. This study presents a "pneumatic nanocannon" coating for titanium orthopedic implants to achieve on-demand release of antibacterial and sustained release of osteogenic agents. SrTiO3 nanotubes (SrNT) were constructed on the surface of Ti implants as "cannon barrel," the "cannonball" (antibiotic) and "propellant" (NH4HCO3) were codeposited into SrNT with assistance of mussel-inspired copolymerization of dopamine and subsequently sealed by a layer of polydopamine. The encapsulated NH4HCO3 within the nanotubes could be thermally decomposed into gases under near-infrared irradiation, propelling the on-demand delivery of antibiotics. This coating demonstrated significant efficacy in eliminating typical pathogenic bacteria both in planktonic and biofilm forms. Additionally, this coating exhibited a continuous release of strontium ions, which significantly enhanced the osteogenic differentiation of preosteoblasts. In an implant-associated infection rat model, this coating demonstrated substantial antibacterial efficiency (>99%) and significant promotion of osseointegration, along with alleviated postoperative inflammation. This pneumatic nanocannon coating presents a promising approach to achieving on-demand infection inhibition and sustained osseointegration enhancement for titanium orthopedic implants.