Background: Bone and joint infections pose significant clinical challenges, often leading to severe complications and substantial healthcare costs. Traditional antibiotic therapies are becoming increasingly ineffective due to rising antibiotic resistance and the biofilm-forming ability of bacteria such as Staphylococcus aureus (S. aureus). Antimicrobial coatings offer a promising approach for the prevention and treatment of implant-associated and bone infections. Following the demonstrated in vitro efficacy of nisin, a naturally occurring antimicrobial peptide, in preventing S. aureus biofilm formation, this study investigates the in vivo potential of a nisin-enriched coating to prevent biofilm-related infections using the Galleria mellonella larva haematogenous implant infection model. Methods: Methicillin-sensitive S. aureus (MSSA) EDCC 5055 was used to infect larvae implanted with nisin-coated titanium Kirschner wires (K-wires). Survival rates and bacterial loads on both the K-wires and in larval tissue were analysed. Biofilm formation on K-wires was further analysed using scanning electron microscopy. Results: The results showed that nisin-coated K-wires significantly improved larval survival and reduced bacterial burden compared to control groups. Scanning electron microscopy confirmed the absence of biofilm formation on nisin-coated K-wires. Conclusions: These findings suggest that nisin-enriched coatings could be a viable strategy for preventing bone and joint infections. Additionally, this study demonstrates the feasibility of testing implant coatings in a cost-effective and ethically sound alternative in vivo model. Further evaluation and testing of the nisin-enhanced coating in vertebrate animal implant infection models is warranted.

Implanted biomaterials can be regarded in a cornerstone in the domain of bone surgery. Their surfaces are expected to fulfil two particular requirements: preventing the settlement and the development of bacteria, and stimulating bone cells in view to foster osseointegration. Therefore, a modern approach consists in the design of dual functional coatings with both antibacterial and osteogenic features. To this end, we developed ultrathin Layer-by-Layer (LbL) coatings composed of biocompatible polyelectrolytes, namely chondroitin sulfate A (CSA) and poly-l-lysine (PLL). The coatings were crosslinked with genipin (GnP), a natural and biocompatible crosslinking agent, to increase their resistance against environmental changes, and to confer them adequate mechanical properties with regards to bone cell behaviors. Antibacterial activity was obtained with nisin Z, an antimicrobial peptide (AMP), which is active against gram-positive bacteria. The coatings had a significant bactericidal impact upon Staphylococcus aureus, with fully maintained bone cell adhesion, proliferation and osteogenic differentiation.

Some removable medical devices such as catheters and cardiovascular biomaterials require antiadhesive properties towards both prokaryotic and eukaryotic cells in order to prevent the tissues from infections upon implantation and, from alteration upon removal. In order to inhibit cell adhesion, we developed ultrathin hydrated Layer-by-Layer (LbL) coatings composed of biocompatible polyelectrolytes, namely chondroitin sulfate A (CSA) and poly-l-lysine (PLL). The coatings were crosslinked with genipin (GnP), a natural and biocompatible crosslinking agent, to increase their resistance against environmental changes. In order to confer antibacterial activity to the coatings, we proceeded to the electrostatically-driven immobilization of nisin Z, an antimicrobial peptide (AMP) active against gram-positive bacteria. The nisin-enriched coatings had a significantly increased anti-proliferative impact on fibroblasts, as well as a strong contact-killing activity against Staphylococcus aureus in the short and long term.