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Howell, Caitlin

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Howell

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Caitlin

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Howell, Caitlin
Author's Publications: search.filters.isAuthorOfPublication.7717eb43-32b3-486c-ab54-4fc902d234bd

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    A bioinspired omniphobic surface coating on medical devices prevents thrombosis and biofouling
    (Nature Publishing Group, 2014) Leslie, Daniel; Waterhouse, Anna; Berthet, Julia B; Valentin, Thomas M; Watters, Alexander; Jain, Abhishek; Kim, Philseok; Hatton, Benjamin D; Nedder, Arthur; Donovan, Kathryn; Super, Elana H; Howell, Caitlin; Johnson, Christopher P; Vu, Thy L; Bolgen, Dana; Rifai, Sami; Hansen, Anne; Aizenberg, Michael; Super, Michael; Aizenberg, Joanna; Ingber, Donald
    Thrombosis and biofouling of extracorporeal circuits and indwelling medical devices cause significant morbidity and mortality worldwide. We describe a bioinspired coating that repels blood from virtually any material by covalently tethering a molecular layer of perfluorocarbon, which holds a thin liquid film of medical-grade perfluorocarbon on the substrate surface, mimicking the liquid layer certain plants use to prevent adhesion. This coating prevents fibrin attachment, reduces platelet adhesion and activation, suppresses biofilm formation, and is stable under blood flow in vitro. Surface-coated medical-grade tubing and catheters, assembled into arteriovenous shunts and implanted in living pigs, remain patent for at least 8 hours without anticoagulation. This coating technology offers the potential to significantly reduce anticoagulation in patients while preventing thrombotic occlusion and biofouling of medical devices.
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    Infused polymers for cell sheet release
    (Nature Publishing Group, 2016) Juthani, Nidhi; Howell, Caitlin; Ledoux, Haylea; Sotiri, Irini; Kelso, Susan; Kovalenko, Yevgen; Tajik, Amanda; Vu, Thy L.; Lin, Jennifer J.; Sutton, Amy; Aizenberg, Joanna
    Tissue engineering using whole, intact cell sheets has shown promise in many cell-based therapies. However, current systems for the growth and release of these sheets can be expensive to purchase or difficult to fabricate, hindering their widespread use. Here, we describe a new approach to cell sheet release surfaces based on silicone oil-infused polydimethylsiloxane. By coating the surfaces with a layer of fibronectin (FN), we were able to grow mesenchymal stem cells to densities comparable to those of tissue culture polystyrene controls (TCPS). Simple introduction of oil underneath an edge of the sheet caused it to separate from the substrate. Characterization of sheets post-transfer showed that they retain their FN layer and morphology, remain highly viable, and are able to grow and proliferate normally after transfer. We expect that this method of cell sheet growth and detachment may be useful for low-cost, flexible, and customizable production of cellular layers for tissue engineering.
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    Self-Replenishing Vascularized Fouling-Release Surfaces
    (American Chemical Society (ACS), 2014) Howell, Caitlin; Vu, Thy L.; Lin, Jennifer; Kolle, Stefan; Juthani, Nidhi; Watson, Emily; Weaver, James; Alvarenga, Jack; Aizenberg, Joanna
    Inspired by the long-term effectiveness of living antifouling materials, we have developed a method for the self-replenishment of synthetic biofouling-release surfaces. These surfaces are created by either molding or directly embedding 3D vascular systems into polydimethylsiloxane (PDMS) and filling them with a silicone oil to generate a nontoxic oil-infused material. When replenished with silicone oil from an outside source, these materials are capable of self-lubrication and continuous renewal of the interfacial fouling-release layer. Under accelerated lubricant loss conditions, fully infused vascularized samples retained significantly more lubricant than equivalent nonvascularized controls. Tests of lubricant-infused PDMS in static cultures of the infectious bacteria Staphylococcus aureus and Escherichia coli as well as the green microalgae Botryococcus braunii, Chlamydomonas reinhardtii, Dunaliella salina, and Nannochloropsis oculata showed a significant reduction in biofilm adhesion compared to PDMS and glass controls containing no lubricant. Further experiments on vascularized versus nonvascularized samples that had been subjected to accelerated lubricant evaporation conditions for up to 48 h showed significantly less biofilm adherence on the vascularized surfaces. These results demonstrate the ability of an embedded lubricant-filled vascular network to improve the longevity of fouling-release surfaces.
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    Stability of Surface-Immobilized Lubricant Interfaces under Flow
    (American Chemical Society (ACS), 2015) Howell, Caitlin; Vu, Thy L.; Johnson, Christopher; Hou, Xu; Ahanotu, Onyemaechi; Alvarenga, Jack; Leslie, Daniel; Uzun, Oktay; Waterhouse, Anna; Kim, Philseok; Super, Michael; Aizenberg, Michael; Ingber, Donald; Aizenberg, Joanna
    The stability and longevity of surface-stabilized lubricant layers is a critical question in their application as low- and nonfouling slippery surface treatments in both industry and medicine. Here, we investigate lubricant loss from surfaces under flow in water using both quantitative analysis and visualization, testing the effects of underlying surface type (nanostructured versus flat), as well as flow rate in the physiologically relevant range, lubricant type, and time. We find lubricant losses on the order of only ng/cm2 in a closed system, indicating that these interfaces are relatively stable under the flow conditions tested. No notable differences emerged between surface type, flow rate, lubricant type, or time. However, exposure of the lubricant layers to an air/water interface did significantly increase the amount of lubricant removed from the surface, leading to disruption of the layer. These results may help in the development and design of materials using surface-immobilized lubricant interfaces for repellency under flow conditions.