## 5 Coating Materials with Embedded Antibiotics and Other Antibofilm Agents  
### Antibiotic Based Antib Biofilm Coatings  
Both controlled drug release from coatings containing physically entrapped antibiotics and covalent immobilization of antibiotics onto solid surfaces have been taken into account as active antibiofilm strategies. [PERSON] et al. (2015) developed a novel antibiotic eluting material based on phosphatidylcholine that could be applied as an implant coating at point of care. The lipid matrix was loaded with 25% antibiotic (amikacin (A) or vancomycin (V) or a mixture of 12.5% of both antibiotics (AV)). In vivo biofilm inhibition was studied in a mouse model of implant-associated infections. Ten catheters have been modified to include a stainless-steel wire, which either has been subsequently covered by a thin film coating with and without embedded antibiotics or remained uncoated. The catheters were divided into five experimental sets, each set comprising two catheters. The two catheters in each set were implanted subcutaneously in dorsal flank regions of mice, bilaterally, one each on the right and left side of the spine. After implantation, the catheter segments were infected by the intraluminal inoculation of a polymicrobial mixture of 10\({}^{5}\) CFU of _S. aureus_ and 10\({}^{4}\) CFU of _P. aeruginosa_. The following modified catheters differing by the sort of the inserted stainless-steel wires were used:Control (uncoated wires, U), U wires, the antibiotics (A and V) being co-administered to the mice via injection, phosphatidylcholine-coated wires (P), AV-coated wires, A-coated wires, and V-coated wires. After 48 h from implantation, the catheters and wires were removed from the mice, rinsed, and SEM images were taken for visual analysis of attached bacterial colonies. The wires with antibiotic-loaded coatings showed 100% clearance rate from _S. aureus_ and a 90% clearance rate of _P. aeruginosa_. To prevent implant-associated osteomyelitisis caused by methicillin-resistant _S. aureus_ (MRSA), the group of [PERSON] [26] used the polymer-lipid encapsulation matrix (PLEX) as a nanoplatform for controlled release local delivery of doxycycline (DOX). The PLEX platform was prepared as previously described in Section 3.1. The doxycycline release profile was characterized by an initial burst effect, 25% of the antibiotic-loaded being released within the first 24 h, followed by zero-order release kinetics for the next 27 days. The efficacy of the biodegradable PLEX-doxycycline implants was evaluated in a rabbit intramedullary nail model. Sixteen rabbits were allocated into two groups of eight animals each. A volume of 100 \(\mu\)L (\(4.7\pm 1.2\times 10^{5}\) CFU) of MRSA strain LUH15101 resistant to penicillin, oxacillin, tetracycline, doxycycline, and cotrimoxazole was inoculated into the medullary cavity of the humerus. The animals in the control group received an uncoated intramedullary nail manufactured from medical grade TAN, while the other eight animals received a doxycycline-containing PLEX-coated nail. After four weeks, all the rabbits in the control group showed culture-positive implants and bone, whereas in the PLEX-doxycycline coated group, 57% of the animals were free from MRSA implant and bone infections. Hydrophilic coatings are known to prevent nonspecific protein adsorption and subsequent bacterial colonization [27]. If the antifouling properties could be combined with the controlled release of an antimicrobial agent, the antib biofilm efficacy of these coatings would be greatly increased. However, this approach is hampered by the fact that most water-soluble low molecular weight antimicrobial agents diffuse very fast out of these hydrophilic coatings. [PERSON] et al. [28] came up with an ingenious solution to the above problem making use of a different loading and release mechanism.