Invited: Polyastaxanthins – Astaxanthin Based Antimicrobial Polymers

Astaxanthin (ATX), a xanthophyll bearing a symmetric chemical structure with two hydroxyl groups, has been used a building block for the synthesis of a library of novel high molecular weight polyesters through copolymerization with various diacids. Polyastaxanthin (pATX) are therapeutic polyesters with varying chemico-physio-mechanico properties (e.g., storage moduli range: 125-1300 MPa and wetting angles of 40-110°). The potential of pATX as a therapeutic material for medical devices was demonstrated in vitro against clinically relevant bacteria (Staphylococcus aureus MRSA252 and MSSA476; S. epidermidis 1457) showing significant reduction of both bacterial growth and biofilm formation. Several in vivo evaluations of pATX’s capacity as an antimicrobial coating were performed. Polyurethane catheter sections coated with pATXs were implanted 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.