Antimicrobial Effects of GL13K Peptide Coatings on S. mutans and L. casei

Abstract

Background: Enamel breakdown around orthodontic brackets, so-called "white spot lesions"�, is the most common complication of orthodontic treatment. White spot lesions are caused by bacteria such as Streptococci and Lactobacilli, whose acidic byproducts cause demineralization of enamel crystals. Aims: The aim of this project was to develop an antimicrobial peptide coating for titanium alloy that is capable of killing acidogenic bacteria, specifically Streptococcus mutans and Lactobacillus casei. The long-term goal is to create an antimicrobial-coated orthodontic bracket with the ability to reduce or prevent the formation of white spot lesions in orthodontic patients thereby improving clinical outcomes. Methods: First, an alkaline etching method with NaOH was established to allow effective coating of titanium discs with GL13K, an antimicrobial peptide derived from human saliva. Coatings were verified by contact angle measures, and treated discs were characterized using scanning electron microscopy. Secondly, GL13K coatings were tested against hydrolytic, proteolytic and mechanical challenges to ensure robust coatings. Third, a series of qualitative and quantitative microbiology experiments were performed to determine the effects of GL13K-L and GL13K-D on S. mutans and L. casei, both in solution and coated on titanium. Results: GL13K-coated discs were stable after two weeks of challenges. GL13K-D was effective at killing S. mutans in vitro at low doses. GL13K-D also demonstrated a bactericidal effect on L. casei, however, in contrast to S. mutans, the effect on L. casei was not statistically significant. Conclusion: GL13K-D is a promising candidate for antimicrobial therapy with possible applications for prevention of white spot lesions in orthodontics.