## 3 Antibiofilm Coatings Based on Antimicrobial Peptides (AMPs)  
### AMPs Releasing Coatings  
AMPs are small evolutionally conserved peptides exhibiting bactericidal properties, with the permeabilization of the cellular membrane as the main mechanism of action [8]. Prevention of _S. aureus_ biomaterial-associated infections was achieved by [PERSON] et al. [9] through the incorporation of the antimicrobial peptide OP-145 into a polymer-lipid encapsulation matrix (PLEX)-coating. This type of formulation allowed the controlled release of the peptideand the maintenance of high peptide levels at the implant-tissue interphase for prolonged periods of time. The AMP OP-145 is a synthetic derivative of the human cathelcidin LL-37 with the following amino acid sequence: Ile-Gly-Lys-Glu-Phe-Lys-Arg-Ile-Val-Glu-Arg-Ile-Lys-Arg-Phe-Leu-Arg-Glu-Leu-Val-Arg-Pro-Leu-Arg acetylated at the \(N\) terminus and amidated at the \(C\) terminus. The lipid-and-polymer-based drug delivery coating (PLEX) consisted of the biocompatible polyester copolymer poly(lactic-\(co\)-glycolic acid) (PLGA) and the following lipids: Dipalmitoyl phosphatidylcholine (DPPC), distearoyl phosphatidylcholine (DSPC), and cholesterol. The PLEX-coating was prepared by mixing two solutions: One solution containing PLGA and cholesterol dissolved in ethyl acetate (EA) and another solution containing the two phospholipids dissolved in a mixture of methanol and EA [10]. The resulted solution was sprayed on solid medical-grade TAN (titanium 7%-aluminium6%-niobium; ISO 5832/11) intramedullary nails. Residual solvents were removed using evaporation under reduced pressure. To evaluate the antibiofilm activity of AMP OP-145-releasing coatings, the authors focused on some in vivo animal models (mice and rabbits). The intramedullary cavity of rabbits was inoculated with \(S\). _aureus_, and subsequently, the animals received an uncoated or a PLEX-OP-145-coated nail. After 28 days, the viable bacteria present on the implants, in the bone cavities, and in the surrounding soft tissues were counted. In rabbits that received implants covered with OP-145-releasing coatings, the contamination ratio of both nails and bones was only 33% as compared with 71% and 100%, respectively, in animals receiving the uncoated nails. Similarly, the ratio of infected soft tissues was only 20% in rabbits with PLEX-OP-145-coated nails, while 71% of the samples taken from rabbits with uncoated nails were culture-positive. [PERSON] et al. [11] immobilized an antifungal 14-helical \(\beta\)-peptide with high specificity for _Candida albicans_ into polymer-based multilayer coatings build-up using the LbL assembly method. Polyelectrolyte multilayer coatings have been constructed on the inner surfaces of flexible catheter tubes made of polyurethane, polyethylene, and silicone. The first deposited layer consisted of the cationic branched PEI. Next, multilayered films were fabricated by alternate deposition of a layer of an anionic polymer (poly-\(L\)-glutamate (PGA) or HA) and of a layer of a cationic polymer (poly-\(L\)-lysine (PLL) or chitosan (CHI)) using the deposition technique named \"fill-and-purge\" [12] so that the ultimate film terminated with an anionic polyelectrolyte. Briefly, the catheter was filled with a solution of the anionic polyelectrolyte PGA or HA and incubated for 3 min or 5 min, respectively. Next, the catheter was rinsed with 0.15 M NaCl aqueous solution to flush out the remaining polymer solution and remove loosely bound polymer. This iterative procedure was repeated identically for the next cationic polyelectrolyte layer (PLL or CHI) and so on. Then, a solution of the \(\beta\)-peptide in 0.15 M NaCl was infused into the catheters coated with (PGA/PLL)\({}_{\times}\)(PGA) or (HA/CHI)\({}_{\times}\)(HA) multilayers. After 24 h, the peptide solution was removed from the tubes, and the tubes were successively rinsed with phosphate-buffered saline (PBS) for 5 min, a solution of tris(hydroxymethyl)aminomethane-buffered saline Tween (TBST) for 1 h, and again with PBS for 5 min.