Polypeptide multilayer self-assembly and enzymatic degradation on tailored gold surfaces studied by QCM-D

Abstract

This study deals with the build up and enzymatic degradation of a nanofilm made by the layer-by-layer (LbL) self-assembly technique on a surface that mimics nonwoven, which is commonly used in wound dressings. The nanofilm is composed of alternating layers of the cationic polyelectrolyte poly-L-lysine (PLL) and the anionic polyelectrolyte poly-L-glutamic acid (PLGA) and is intended as a lid for bactericides inserted into a dressing for chronic wounds. Chronic wounds are often infected by bacteria such as Staphylococcus aureus and a mechanism to trigger release of bactericides into such wounds when they become infected is of interest. QCM-D (quartz crystal microbalance with dissipation monitoring) was used to monitor both build-up and degradation of the nanofilm on a surface tailored by the self-assembly monolayer technique to resemble the nonwoven surface. It was found that whereas a normal protease present in the body and wound, as well as a bovine protease that was used as reference, did not catalyze degradation of the polyelectrolyte multilayer, a protease from Staphylococcus aureus, V8 glutamyl endopeptidase, caused rapid break-down of the film. However, a prerequisite of the degradation was that the LbL assembly had been terminated by the anionic PLGA. The results open for products where the wound infection is the trigger for release of bioactive substances from a wound dressing.