Polyastaxanthin-based coatings reduce bacterial colonization in vivo

Polyastaxanthin p(ATX) is a family of polymers synthesized from the carotenoid astaxanthin and various dicarboxylic acids, resulting in moldable, high MW polymers, that can be made biodegradable. p(ATX) has previously shown to have antimicrobial properties in vitro, including inhibition of biofilm formation of S. epidermidis 1457, S. aureus MRSA252 and S. aureus MSSA476. In this work, we characterized the in vivo performance of p(ATX). Several in vivo evaluations were performed by implanting polyurethane catheter sections coated with pATXs in immunodeficient mice, followed by infection with S. aureus ATCC 6538. The polymer's capacity to inhibit bacterial biofilm formation on catheters was assessed. Two insights were generated. First, pATX has the capacity to significantly reduce the bacterial burden on coated catheters compared to uncoated catheters. Second, control over the biodegradation rate of the pATX, achieved via the use of hydrophilic diacid-comonomers, is required to maintain antimicrobial properties for at least 96 h. We found that slower degrading polymer is more beneficial in reducing bacterial load compared to rapidly degrading polymers, which begin to degrade immediately once hydrated. Thus, pATX, when appropriately designed, has the potential to perform as an antimicrobial coating for medical devices.