LAUSR

The widespread nature of bacterial infections and their increasing resistance to antibiotics has led to the development of antibacterial coatings in multiple medical settings, especially on bone implants.[1] The surface of implants is susceptible to numerous bacterial infections mainly because of the formation of a surface biofilm and the compromised immune response at the implant/tissue interface. Staphylococcus aureus and Staphylococcus epidermidis are among the most common strains that cause implant associated infections.[2] S. aureus is considered a major virulent pathogen that colonizes and infects both hospitalized patients with decreased immunity and healthy immunocompetent people. Although this bacterium is found naturally on the skin and in the nasopharynx of the human body, the environment within a hospital supports the acquisition of resistant S. aureus strains. Skin and mucous membranes are excellent barriers against local tissue invasion by S. aureus. However, if these barriers are breached due to trauma or surgery, S. aureus can enter the underlying tissue, creating local abscess lesion, and may further progress to the lymphatic channels or blood, where it can cause septicemia.[3,4] Once a biofilm is formed, it protects adherent bacteria from the host defense system and bactericidal agents via several mechanisms.[5–7] The biofilm becomes a source of pathogens and infections, being the cause of so called nosocomial infections, infections acquired in a hospital or healthcare unit.[8–10] Nosocomial infections are secondary to the main condition of the patient, and can have lethal consequences following operations such as bone replacement or open heart surgery.[11–13] Because biofilms can form on almost any material present in a surgery room, prevention of their formation can be fundamental for patient survival. Unfortunately, there are still no good means to eliminate the infection developed through an implant surgery. Currently, implant removal is the only strategy to eradicate the infections and the immune response of the host to the implant is consequently impaired. In the early phase after implantation, the local defense system is severely disturbed by the surgical trauma. Thus, prevention There is an urgent need for the development of effective antibacterial coatings to cope with more and more resistant bacterial strains in medical environments, and particularly to prevent nosocomial infections following bone implant surgery. Polyelectrolyte multilayers (PEMs) based on poly-llysine (PLL) and complexes of poly(acrylic acid) (PAA) and gentamicin have been fabricated here applying the layer-by-layer (LbL) technique. Complexes are prepared by mixing PAA and gentamicin solutions in 500 × 10−3 m NaCl at pH 4.5. The assembly of PLL and the complexes follows an exponential growth allowing a high loading of gentamicin in a four bilayer PEM. Although PEMs are stable and do not degrade at physiological pH, there is a continuous release of gentamicin at pH 7.4. PEMs show an initial burst release of gentamicin in the first 6 h, which liberates 58% of the total gentamicin released during the experiment, followed by a sustainable release lasting over weeks. This release profile makes the coating appealing for the surface modification of bone implants as a high concentration of antibiotics is necessary during implant surgery while a lower antibiotic concentration is needed until tissue is regenerated. PEMs are effective in preventing the proliferation of the Staphylococcus aureus strain.