Antibacterial properties of antimicrobial peptide HHC36 modified polyetheretherketone

Construction of pH-responsive hydrogel coatings on titanium surfaces for antibacterial and osteogenic properties

Infection is one of the leading causes of failure in titanium-based implant materials during clinical surgeries, often resulting in delayed or non-union of bone healing. Furthermore, the overuse of antibiotics can lead to bacterial resistance. Therefore, developing a novel titanium-based implant material with both antimicrobial and osteogenic properties is of great significance. In this study, chitosan (CS), polydopamine (PDA), and antimicrobial peptides (AMPs) HHC36 were applied to modify the surface of titanium, resulting in the successful preparation of the composite material Ti-PDA-CS/PDA@HHC36 (abbreviated as T-P-C/P@H). CS promotes osteogenesis and cell adhesion, providing an ideal microenvironment for bone repair. PDA enhances the material's biocompatibility and corrosion resistance, offering cell adhesion sites, while both components exhibit pH-responsive characteristics. The HHC36 effectively prevents infection, protecting the bone repair material from bacterial damage. Overall, the synergistic effects of these components in T-P-C/P@H not only confer excellent antimicrobial and osteogenic properties but also improve biocompatibility, offering a new strategy for applying titanium-based implants in clinical settings.

Antimicrobial activity of ceftibuten/polymyxin B combination against polymyxin/carbapenem-resistant Klebsiella pneumoniae

OBJECTIVES

To evaluate the synergistic effect of a ceftibuten and polymyxin B combination and to determine its capacity to overcome polymyxin B resistance in polymyxin/carbapenem-resistant (PC-R) Klebsiella pneumoniae.

METHODS

To investigate the combination's antibacterial efficacy, antimicrobial susceptibility tests using broth microdilution methods, chequerboard assays and time-kill testing were performed. Antibiofilm activity was also assessed. The treatment's effect on the bacterial cell membrane was examined by quantifying intracellular protein leakage and conducting scanning electron microscopy. Haemocompatibility tests were conducted to evaluate toxicity. Additionally, an infection model was established using Swiss mice to assess in vivo antimicrobial activity.

RESULTS

The ceftibuten/polymyxin B combination demonstrated synergistic effects against several PC-R strains of K. pneumoniae, as determined by the FIC index (FICI) values, which ranged from 0.15 to 0.37. This combination was efficacious, exhibiting bactericidal activity at twice the MIC. Ceftibuten/polymyxin B also demonstrated antibiofilm activity. Additionally, ceftibuten/polymyxin B neither damaged the bacterial membrane nor exhibited haemolytic activity. Based on these findings, the in vivo therapeutic potential was investigated and it was found that ceftibuten/polymyxin B significantly decreased the bacterial load in the peritoneal lavage fluid of mice, revealing its effectiveness in treating infections caused by PC-R K. pneumoniae.

CONCLUSIONS

The ceftibuten/polymyxin B combination exhibited synergistic effects in vitro and in vivo, and thus might be a promising therapeutic alternative for treating PC-R K. pneumoniae infections. As the combination was efficacious in preclinical models, researchers may further investigate its potential in clinical studies.

Efficacy of pH-Responsive Surface Functionalized Titanium Screws in Treating Implant-associated S. aureus Osteomyelitis with Biofilms Formation

Implant-associated Staphylococcus aureus (S. aureus) osteomyelitis (IASO) leads to high orthopedic implant failure rates due to the formation of Staphylococcal abscess community within the bone marrow and bacterial colonization in the osteocyte lacuno-canalicular network (OLCN). To address this, antimicrobial peptides (HHC36)-loaded titania nanotubes (NTs) are developed on titanium screws (Ti-NTs-P-A), which integrate pH-responsive polymethacrylic acid to control HHC36 release for eradicating bacteria in IASO. Colony-forming unit assay confirmed that Ti-NTs-P-A screws maintained sustainable antibacterial effectiveness, killing over 65% of S. aureus even after multiple bacterial solution replacements. Notably, Ti-NTs-P-A screws exhibit significant pH-responsive HHC36 release behavior and bactericidal activity, consistent with the phenotype of peptides-killed bacteria from scanning electron microscopy. Transcriptome sequencing results reveal that Ti-NTs-P-A screws interfered with ribosome formation and disrupted the arginine biosynthesis, which is crucial for bacterial survival in acidic environments. In the non-infected implant model, the bone-implant contact ratio of the Ti-NTs-P-A screw is 2.3 times that of the clinically used titanium screw. In an IASO model, Ti-NTs-P-A screws effectively eradicated bacteria within the OLCN, achieving an 80% infection control rate and desirable osteointegration. Collectively, Ti-NTs-P-A screws with pH-responsive antibacterial properties exhibit great potential for eradicating bacteria and achieving osseointegration in IASO.

Synergistic antimicrobial combination of third-generation cephalosporins and polymyxin B against carbapenem-polymyxin-resistant Klebsiella pneumoniae: an in vitro and in vivo analysis

Antibiotic combination therapy is a promising approach to address the urgent need for novel treatment options for infections caused by carbapenem-polymyxin-resistant Klebsiella pneumoniae (CPR-Kp). The present study aimed to investigate the synergistic potential of four cephalosporins in combination with polymyxin B (PMB). A checkerboard assay was performed to evaluate the synergistic effects of cephalexin (CLX), cefixime, cefotaxime (CTX), and cefmenoxime (CMX) in combination with PMB. Subsequently, experiments evaluating the use of CTX or CMX in combination with PMB (CTX-PMB or CMX-PMB, respectively), including growth curve and SynergyFinder analysis, antibiofilm activity assays, cell membrane integrity assays, and scanning electron microscopy, were performed. Safety assessments were also conducted, including hemolysis and toxicity evaluations, using Caenorhabditis elegans. Furthermore, an in vivo model in C. elegans was adopted to assess the treatment efficacy against CPR-Kp infections. CTX-PMB and CMX-PMB exhibited low fractional inhibitory concentration indexes ranging from 0.19 to 0.50 and from 0.25 to 1.5, respectively, and zero interaction potency scores of 37.484 and 15.076, respectively. The two combinations significantly reduced growth and biofilm formation in CPR-Kp. Neither CTX-PMB nor CMX-PMB compromised bacterial cell integrity. Safety assessments revealed a low hemolysis percentage and high survival rates in the C. elegans toxicity evaluations. The in vivo model revealed that the CTX-PMB and CMX-PMB treatments improved the survival rates of C. elegans. The synergistic effects of the CTX-PMB and CMX-PMB combinations, both in vitro and in vivo, indicate that these antibiotic pairings could represent effective therapeutic options for infections caused by CPR-Kp.

Strategies to improve the performance of polyetheretherketone (PEEK) as orthopedic implants: from surface modification to addition of bioactive materials

Polyetheretherketone (PEEK), as a high-performance polymer, is widely used for bone defect repair due to its homogeneous modulus of elasticity of human bone, good biocompatibility, excellent chemical stability and projectability. However, the highly hydrophobic surface of PEEK is biologically inert, which makes it difficult for cells and proteins to attach, and is accompanied by the development of infections that ultimately lead to failure of PEEK implants. In order to further enhance the potential of PEEK as an orthopedic implant, researchers have explored modification methods such as surface modification by physical and chemical means and the addition of bioactive substances to PEEK-based materials to enhance the mechanical properties, osteogenic activity and antimicrobial properties of PEEK. However, these current modification methods still have obvious shortcomings in terms of cost, maneuverability, stability and cytotoxicity, which still need to be explored by researchers. This paper reviews some of the modification methods that have been used to improve the performance of PEEK over the last three years in anticipation of the need for researchers to design PEEK orthopedic implants that better meet clinical needs.

Comparative Analysis of the Mechanical Properties and Biocompatibility between CAD/CAM and Conventional Polymers Applied in Prosthetic Dentistry

Modern media often portray CAD/CAM technology as widely utilized in the fabrication of dental prosthetics. This study presents a comparative analysis of the mechanical properties and biocompatibility of CAD/CAM (Computer-Aided Design/Computer-Aided Manufacturing) polymers and conventional polymers commonly utilized in prosthetic dentistry. With the increasing adoption of CAD/CAM technology in dental laboratories and practices, understanding the differences in material properties is crucial for informed decision-making in prosthodontic treatment planning. Through a narrative review of the literature and empirical data, this study evaluates the mechanical strength, durability, esthetics, and biocompatibility of CAD/CAM polymers in comparison to traditional polymers. Furthermore, it examines the implications of these findings on the clinical outcomes and long-term success of prosthetic restorations. The results provide valuable insights into the advantages and limitations of CAD/CAM polymers, informing clinicians and researchers about their suitability for various dental prosthetic applications. This study underscores the considerable advantages of CAD/CAM polymers over conventional ones in terms of mechanical properties, biocompatibility, and esthetics for prosthetic dentistry. CAD/CAM technology offers improved mechanical strength and durability, potentially enhancing the long-term performance of dental prosthetics, while the biocompatibility of these polymers makes them suitable for a broad patient demographic, reducing the risk of adverse reactions. The practical implications of these findings for dental technicians and dentists are significant, as understanding these material differences enables tailored treatment planning to meet individual patient needs and preferences. Integration of CAD/CAM technology into dental practices can lead to more predictable outcomes and heightened patient satisfaction with prosthetic restorations.

The Formation Process and Mechanism of the 3D Porous Network on the Sulfonated PEEK Surface

A three-dimensional (3D) porous network can be prepared on the PEEK surface by sulfonation with enhanced osseointegration and antibacterial properties. However, few studies have been conducted on the formation mechanism of a 3D porous network. In this work, the surface and cross-sectional morphologies, chemical compositions, functional groups, surface wettability, and crystalline states of sulfonated PEEK were investigated at different sulfonation times and coagulant concentrations. The results show that the number of nodular structures and broken fibers on the sulfonated PEEK surface as well as the size of macrovoids in the cross sections increase with increasing sulfonation times when water is used as a coagulant. In contrast, dilute sulfuric acid as a coagulant can inhibit the formation of surface porous structures and macrovoids in the cross sections. Moreover, all of the sulfonated PEEK samples have the same chemical compositions but exhibit better hydrophilicity as the number of microsized pores decreases. It is proposed that non-solvent-induced phase separation (NIPS) occurs during the sulfonation process, and the formation mechanism of surface and cross-sectional morphologies is discussed. Furthermore, it is assumed that the air is trapped in the microsized pores, leaving the surface of the 3D porous network in the Cassie-wetting state. All of these preliminary results throw light on the nature of the sulfonation process and may guide further modification of the structures of sulfonated PEEK.