5. Layer-by-Layer Coatings as Infection-Resistant Biomaterials

We discuss the use of layer-by-layer (LbL) films as a powerful platform for engineering multifunctional antibacterial coatings for biomedical devices. These coatings can be designed to incorporate a variety of bioactive antimicrobial molecules, including antibiotics, cationic peptides, biofilm-disrupting and Q-sensing agents, and immunoregulatory cytokines. Here, we focus on active rather than passive delivery of antimicrobials from the coatings achieved through temperature or pH variations, as well as through the application of electric field. Of particular interest are “self-defensive” coatings which are activated in the presence of pathogens by pathogen-specific molecules or by acidification of the immediate environment by pathogenic bacteria. We describe several types of these coatings, which can carry high payloads of antimicrobials but do not release them at normal physiological conditions at pH 7.5 until the arrival of a bacterial trigger. Importantly, these coatings inhibit bacterial colonization while simultaneously promoting a healthy tissue response.