Supercritical fluids (SCF) have variable liquid-like densities, gas-like viscosities, and the zero surface tension of gases. These three basic properties provide unique advantages in modifying the surfaces of medical devices to provide better therapies.
By applying the coating using a non-reactive gas in its supercritical (fluid) state, Micell can avoid exposing both the coating and the substrate to solvents or extreme temperatures that could alter the structure, chemistry, morphology, or most importantly the therapeutic effectiveness of the drug. And because the fluid is actually a gas, it does not affect materials already coated on the device. This allows for multiple layers containing one or more therapeutic agents to be coated onto the device while maintaining specific control over drug-elution profiles.
The variable density of supercritical fluid allows careful control over the solvation, diffusion, and flow of the drugs and polymers during the surface modification process. It also facilitates the generation of drug-eluting coatings with precise control over drug morphology and polymer composition. This ability has overcome significant challenges using current solvent-based methods because the solvents tend to dissolve or otherwise debilitate the previously coated layer.
The gas-like viscosity and surface tension of supercritical fluids allow the coating to access the most intricate areas of medical devices. The supercritical fluids are also unaffected by or indifferent to the surface characteristics of the pre-treated medical device, and allow application processes that are up to ten times faster than those requiring transport of materials in traditional solvents. These properties actually make it possible to deliver therapeutic chemistry into micro- and nanoporous openings in medical devices.