Poster AA12 - Bioinspired Skin Phantoms to Investigate Dynamics of Catheter-Related Bloodstream Infections

Introduction: Catheter-related bloodstream infections (CRBSIs) remain a challenge in healthcare, significantly affecting patient morbidity and mortality while imposing substantial costs on healthcare systems. In the United States alone, CRBSIs are responsible for approximately 250,000 infections annually, with peripheral and central venous catheters [1]. These infections are associated with mortality rates ranging from 12% to 25% and can extend hospital stays, escalating healthcare costs by up to $29,000 per episode [2,3]. Innovative use of bioinspired materials like Ecoflex, which simulates human skin's textural properties, offers a promising avenue to investigate the dynamics of these infections by understanding bacterial adhesion—a principal factor in CRBSI development.
This study explores the effectiveness of Ecoflex in replicating human skin characteristics to examine the influence on bacterial colonization dynamics. Integrating bioinspired phantoms that simulate actual human skin surfaces can facilitate understanding the interaction between human skin and bacterial pathogens. Ecoflex's ability to emulate human skin not only aids in understanding bacterial adhesion mechanisms but also serves as a foundation for developing innovative medical devices less prone to fostering bacterial growth, aligning with the broader goal of enhancing patient care and safety in hospital settings.

Materials and

Methods: We utilized Ecoflex, a silicone-based material, to construct a bioinspired hand phantom that accurately emulates the surface roughness and wettability of human skin, which are critical for understanding bacterial adhesion mechanisms. The phantom creation involved precise molding techniques to ensure the replication of realistic human skin features essential for our studies. Surface roughness and wettability were assessed using advanced measurement techniques, and these properties were altered under conditions simulating the presence of natural skin oils. E. coli (ATCC 25922) was chosen as the model organism for bacterial adhesion studies, which were conducted using high-resolution fluorescence microscopy to analyze the interaction dynamics at the microbial level. This approach included dynamic IV therapy scenario simulations that closely mimicked clinical settings, enhancing the applicability of our results to real-world medical environments. Figure 1a depicts the major workflow in fabricating the skin-like materials used for the hand phantom.

Results, Conclusions, and Discussions:

Results: Surface roughness measurements of hand replicas showed good agreement (less than 10% error) with the standard roughness samples with their known values. Ecoflex showed static contact angles for deionized (DI) water between 95.31° ± 10.22° and 107.66° ± 3.43°, and for artificial sweat between 96.08° ± 13.16° and 110.77° ± 6.82°, closely aligning with the hydrophobic nature of human skin. After applying artificial sebum, contact angles decreased to between 50.60° ± 6.28° and 61.48° ± 10.44°, indicating an increased hydrophilicity that mirrors sebum-treated human skin [4]. Moreover, Figure 2 shows the interaction between bacterial colonies in Ecoflex, with images highlighting E. coli adhesion to textures representing skin areas like the elbow, hand, and forearm. The effectiveness of Ecoflex was further highlighted in a dynamic IV therapy scenario, simulating real-life catheter use. The provided bacterial growth curve from the 12-hour experiment clearly illustrates this effect (Figure 3). In this experiment, E. coli was inoculated on the replica's surface under conditions that mimic intravenous therapy. The bacterial growth pattern observed shows a lag phase of about 4 hours, after which the bacteria enter a log phase, characterized by rapid growth. This growth pattern highlights the potential as an effective platform for mimicking bacterial growth dynamics.

Conclusions: The study demonstrates that Ecoflex when molded into a hand phantom, can effectively replicate the natural properties of human skin that influence bacterial adhesion and growth. The modifications in hydrophobicity and hydrophilicity induced by treatments like artificial sebum significantly affect the material's surface, showcasing its potential to improve the safety and functionality of medical devices that contact human skin.

Discussions: These findings highlight the importance of using bioinspired materials like Ecoflex in medical device research. The hand phantom model is an effective platform for studying bacterial interactions under realistic conditions using wearable and implantable sensors and for many other biomedical research applications, such as soft robotics and testing many other biosensors.

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