(132c) Fluorinated Silk-Based Hydrophobic Coatings for Platelet Preservation Applications

Platelet transfusions are lifesaving procedures conducted to minimize excessive bleeding and advances have been realized with biomaterials utilized in catheters, tissue grafts, drug delivery systems, heart valves, and stents, among other devices. However, mitigating risks associated with thromboinflammation associated with blood-contacting biomaterials remains a major challenge. Platelet activation and adhesion is a key trigger for thromboinflammatory responses and is a major challenge not only for the development of blood-contacting biomaterials, but also significantly limits the storage, transport and transfusion of platelets. Platelets are typically stored at ambient temperatures with constant agitiation in breathable blood-bags. However, these storage conditions significantly increases the propensity for bacterial contamination which limits the shelf-life of stored platelets to 4-5 days. Additionally, these conditions also pose serious challenges to the transport of platelets to remote locations where the supply of platelets may be limited.

Recently, surface modification strategies have been explored to minimize platelet adhesion to the surfaces of blood storage and transfusion consumables and prevent bacterial contamination, thereby improving the shelf-life of stored platelets. This includes manipulation of surface charge, chemistry, and hydrophilicity as well as covalent attachment of anti-coagulants such as heparin or sialic acid. However, the scalability and hemocompatibility of these surface modification strategies remains a challenge. Clinically, hydrophobic polymers, such as polytetrafluoroethylene (PTFE) and polyurethane are widely utilized in the fabrication of vascular grafts and catheters as they minimize platelet adhesion due to their hydrophobic properties. However, there is a higher risk of compliance mismatch between arterial blood vessels and these implants, limiting their use in arterial transfusions. Moreover, synthetic materials such as PTFE are not bioresorbable and do not aid in tissue regeneration and healing. On the other hand, while resorbable biopolymers with tunable mechanical properties, such as chitosan, gelatin, b-cyclodextrin, and cellulose exhibit better compliance matching, their hemocompatibility remains a significant challenge. There is therefore a growing need for hemocompatible biopolymers, that minimize platelet adhesion, exhibit good mechanical stability and tunability, and minimize the risk of bacterial contamination, to develop superior blood-contacting biomedical devices for platelet collection, storage and transfusion applications.

Silk fibroin, a structural protein, is a natural, biocompatible material utilized for the fabrication of robust biomaterials. Furthermore, there are several known chemical modification strategies that enable us to tune the chemical functionality of silk. We have developed a chemical modification strategy to generate hydrophobic silk fibroin by tethering perfluorocarbons onto the silk backbone. We hypothesized that fluorinated silk owing to its hydrophobic nature will prevent the adhesion of biological milieus, including bacteria and platelets onto the biomaterial surface, thereby preventing platelet activation and aggregation. Figure 1(a) shows the process for synthesizing fluorinated silk as well as the contact angles of the fluorinated silk coating, where C8 and C9 exhibit similar surface hydrophobicity to teflon. Moreover, these chemical modifications do not affect the cytocompatibility of native silk. As seen in Figure 1(b), FL silk films showed no significant cytotoxicity towards mammalian cells. We further demonstrated that fluorinated silk coated subtsrates successfully resisted biofilm formation when exposed to both Gram positive and Gram negative bacterial strains, while the controls were fully contaminated, as seen in Figure 1(c). Lastly, platelet adhesion was significantly lowered on FL silk-coated substrates (Figure 1(d)) and showed significantly lower basal activation over 24 h (Figure 1(e)) as compared to uncoated controls.

We believe that this approach will significantly improve the shelf-life of stored platelets and minimize the risks associated with platelet transfusions, thereby offering a viable biopolymer-based, hemocompatible material for the development of blood-contacting medical devices.