Porous Coatings by Vapor Sublimation and Deposition for Molecular Channeling and Filtration in an Interstitial Fluid Microfiltration Device

Implantable interstitial fluid (ISF) collection components have emerged as promising platforms for continuous health monitoring and diagnostic applications. Nonetheless, cellular contaminants and tissue ingrowth remain significant challenges for implantable ISF devices. Herein, a vapor-based porous coating technology is proposed, capable of producing a mechanically durable and homogeneous porous layer within the internal lumen of a nitinol tube. Biochemically, the coating prevents the ingrowth of cells or tissues into the porous structure while simultaneously ensuring the desired filtration performance of the ISF. The porous coating layers are thoroughly examined with respect to their ability to transport molecules. A variety of model probing molecules are loaded/encapsulated within the layered configuration to understand the molecular diffusion kinetics and transport phenomenon in the proposed porous coatings. Furthermore, in vitro and in vivo assessments of the interstitial fluids are used to validate the transport of biomolecules within the porous coatings. Moreover, when the perforated nitinol tube is incorporated, the filtration efficiency is > 80% for particles larger than 500 nm, and more than 98% of the particles larger than 1000 nm are retained during the filtration of these coatings.