Developing and characterising mucin films and evaluating them as a bacteria resistant coating.

Abstract

Mucin is a naturally occurring polymer that belongs to the glycoprotein family. It is an amphiphilic molecule made of two main parts: a hydrophobic protein backbone and hydrophilic carbohydrate side chains. As a result of this structure, it can adsorb on many types of surfaces to create a hydrophilic, lubricating layer. Mucin has been shown in recent studies to have the potential to suppress the adhesion of bacteria. The aim of this study is to develop a uniform mucin coating resistant to bacterial adhesion. In developing a coating technique, we created a multi-layer system consisting of a poly(acrylic acid) (PAA) copolymer as a base layer and a mucin layer on top, as this exploits the mucoadhesion interactions between PAA and mucin in bonding to the base. The mucin coatings created were then evaluated against the adhesion of microorganisms, including two species of bacteria (Staphylococcus epidermidis and Escherichia coli) and one species of yeast (Candida albicans) known to be problematic for patients inserted with urinary catheters. This study develops as the following: oExperimental work was conducted on the creation of the mucin coating using poly(aciylic acid)-b-poly(methyl methacrylate) as a base coating and poly(methyl methacrylate) and silicon as controls. The effect of pH was used as a means to control the mucin layer thickness, where a thicker mucin layer was adsorbed on the copolymer from acidic mucin solutions than neutral and basic mucin solutions. Roughness and surface energy measurements revealed smoother and more hydrophilic surfaces created from the thicker mucin layers. oInfrared spectroscopic ellipsometiy was used to study the interfacial bonding between the copolymer layer and the adsorbed mucin layer. This study showed that at pH 3 more hydrogen bonds were created between PAA-b-PMMA and mucin. It also showed conformational changes in the protein backbone of mucin at lower pH. oIn evaluating the adhesion of microorganisms on the mucin coating, through direct counting, we saw a decrease in bacterial adhesion after mucin coating compared to the bare surfaces but no effect on the adhesion of yeast cells. Increasing the mucin coating thickness further reduced the numbers of Staphylococcus epidermidis but not Escherichia coli