Membrane perturbation, altered morphology and killing of Staphylococcus epidermidis upon contact with a cytocompatible peptide-based antibacterial surface

In vitro co-culture models for the assessment of orthopedic antibacterial biomaterials

The antibacterial biofunctionality of bone implants is essential for the prevention and treatment of implant-associated infections (IAI). In vitro co-culture models are utilized to assess this and study bacteria-host cell interactions at the implant interface, aiding our understanding of biomaterial and the immune response against IAI without impeding the peri-implant bone tissue regeneration. This paper reviews existing co-culture models together with their characteristics, results, and clinical relevance. A total of 36 studies were found involving in vitro co-culture models between bacteria and osteogenic or immune cells at the interface with orthopedic antibacterial biomaterials. Most studies (∼67%) involved co-culture models of osteogenic cells and bacteria (osteo-bac), while 33% were co-culture models of immune cells and bacterial cells (im-bac). All models involve direct co-culture of two different cell types. The cell seeding sequence (simultaneous, bacteria-first, and cell-first) was used to mimic clinically relevant conditions and showed the greatest effect on the outcome for both types of co-culture models. The im-bac models are considered more relevant for early peri-implant infections, whereas the osteo-bac models suit late infections. The limitations of the current models and future directions to develop more relevant co-culture models to address specific research questions are also discussed.

The Potential of Surface-Immobilized Antimicrobial Peptides for the Enhancement of Orthopaedic Medical Devices: A Review

Due to the well-known phenomenon of antibiotic resistance, there is a constant need for antibiotics with novel mechanisms and different targets respect to those currently in use. In this regard, the antimicrobial peptides (AMPs) seem very promising by virtue of their bactericidal action, based on membrane permeabilization of susceptible microbes. Thanks to this feature, AMPs have a broad activity spectrum, including antibiotic-resistant strains, and microbial biofilms. Additionally, several AMPs display properties that can help tissue regeneration. A possible interesting field of application for AMPs is the development of antimicrobial coatings for implantable medical devices (e.g., orthopaedic prostheses) to prevent device-related infection. In this review, we will take note of the state of the art of AMP-based coatings for orthopaedic prostheses. We will review the most recent studies by focusing on covalently linked AMPs to titanium, their antimicrobial efficacy and plausible mode of action, and cytocompatibility. We will try to extrapolate some general rules for structure-activity (orientation, density) relationships, in order to identify the most suitable physical and chemical features of peptide candidates, and to optimize the coupling strategies to obtain antimicrobial surfaces with improved biological performance.

Protein-Engineered Polymers Functionalized with Antimicrobial Peptides for the Development of Active Surfaces

Antibacterial resistance is a major worldwide threat due to the increasing number of infections caused by antibiotic-resistant bacteria with medical devices being a major source of these infections. This suggests the need for new antimicrobial biomaterial designs able to withstand the increasing pressure of antimicrobial resistance. Recombinant protein polymers (rPPs) are an emerging class of nature-inspired biopolymers with unique chemical, physical and biological properties. These polymers can be functionalized with antimicrobial molecules utilizing recombinant DNA technology and then produced in microbial cell factories. In this work, we report the functionalization of rPBPs based on elastin and silk-elastin with different antimicrobial peptides (AMPs). These polymers were produced in Escherichia coli, successfully purified by employing non-chromatographic processes, and used for the production of free-standing films. The antimicrobial activity of the materials was evaluated against Gram-positive and Gram-negative bacteria, and results showed that the polymers demonstrated antimicrobial activity, pointing out the potential of these biopolymers for the development of new advanced antimicrobial materials.