Poster O12 - Nanoencapsulation of Bacteriophages within an Antifouling Emulsion for Blood-Contacting Medical Devices

Introduction: Clinical use of medical devices plays a pivotal role in decreasing patient morbidity and mortality; however, medical device infection continues to plague the medical industry as a major contributing factor to the development of hospital-acquired infections (HAIs) (VanEpps, J. S. 2016). Bacteriophages (phages) are ubiquitous parasites capable of recognizing and infecting pathogenic bacteria parasitically. They have high antimicrobial properties and show little toxicity to beneficial bacteria due to their specificity; additionally, phages are sourced from waste and groundwater, meaning they are highly cost-effective (Kutateladze, M. 2010). Although used in food packaging and dairy conservation, there are no fully FDA-approved uses for bacteriophage therapy in biomedical applications.
In addition to HAI development, indwelling medical devices induce thrombus formation which can lead to device failure, or more severely, patient morbidity via stroke or arterial embolism. Researchers have continued exploring alternative methods for developing antifouling surface mechanisms to decrease the risk to patients. One that has gained in popularity involves a biomimetic liquid-infused slippery outer layer, often obtained using a lubricant, to generate an anti-fouling surface (Leslie, D.C. 2014). Therefore, including a lubricant layer can lead to an antibacterial and antifouling material. However, to increase the efficiency of bacterial killing, a combination therapy can be utilized. Success has been shown in encapsulating bacteriophages within micelles, or liposomes, to increase antibacterial efficiency (Leung, S. S. Y. 2018). To utilize a slippery component for antifouling purposes, these micelles can be made within a bulk oil solution to create a nanoemulsion (NE).

Materials and

Methods: To generate an antifouling material with enhanced antibacterial efficacy, an E. coli bacteriophage (ECΦ) aqueous solution was incorporated into a hexadecane oil to create a water-in-oil NE. The NE was then swelled into a polytetrafluoroethylene (PTFE) making an antifouling and antibacterial material to be used in blood-contacting medical device applications. The NE and phages were characterized separately via dynamic light scattering (DLS), stability, transmission electron microscopy (TEM), and titer enumeration, respectively, before being incorporated into the PTFE. The material analysis involved testing the slippery characteristics as well as the bacteriophage leaching. Finally, biocompatibility testing was completed to analyze the material’s antibacterial, antifouling, and cytocompatible potential for clinical use.

Results, Conclusions, and Discussions: Initial DLS and TEM data showed the size of the Podoviridae bacteriophages to be small enough to be completely encapsulated into two of the NE makeups based on the size of the nanodroplets created within the NE. With blood-contacting device materials as the goal for this material, the antifouling potential was tested once the NE was swelled into the PTFE. Figure 1A shows sliding angle analysis immediately after swelling and after 24 h of room temperature storage. Initial readings have sliding angles of less than 10 degrees, well below what is considered a “slippery” surface3. Although there is an increase in sliding angle after storage, the swelled PTFE is still well below the unswelled PTFE, showing it retains a portion of its antifouling potential. The leaching from the 10% PhageNE was found to be substantially higher for the first 48 h compared to the 5% PhageNE PTFE. This is most likely due to the 5% PhageNE having a slightly smaller nanodroplet size compared to the 10% PhageNE. The inability of the 5% PhageNE swelled PTFE to properly store the phages makes it unattractive for further exploration. Further antibacterial testing with the 10% PhageNE displayed a significant reduction in E. coli adhesion compared to both the non-swelled PTFE and ControlNE PTFE samples. For longer applications, the 10% PhageNE is preferable with zones sustaining for 4 days as well as an 89% reduction in E. coli adhesion after 24 h. Leaching and zone analyses give a visualization of the slow degradation of the NE within the PTFE material. The sustained breakdown gives this material potential as an antimicrobial material in the biomedical field.

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