Visualizing a Nanoscale Lubricant Layer under Blood Flow

Tethered-liquid
perfluorocarbons (TLPs) are a class of liquid-infused
surfaces with the ability to reduce blood clot formation (thrombosis)
on blood-contacting medical devices. TLP comprises a tethered perfluorocarbon
(TP) infused with a liquid perfluorocarbon (LP); this LP must be retained
to maintain the antithrombotic properties of the layer. However, the
stability of the LP layer remains in question, particularly for medical
devices under blood flow. In this study, the lubricant thickness is
spatially mapped and quantified in situ through confocal dual-wavelength
reflection interference contrast microscopy. TLP coatings prepared
on glass substrates are exposed to the flow of 37% glycerol/water
mixtures (v/v) or whole blood at a shear strain rate of around 2900
s–1 to mimic physiological conditions (similar to
flow conditions found in coronary arteries). Excess lubricant (>2
μm film thickness) is removed upon commencement of flow. For
untreated glass, the lubricant is completely depleted after 1 min
of shear flow. However, on optimized TLP surfaces, nanoscale films
of lubricants (thickness between 100 nm and 2 μm) are retained
over many tens of minutes of flow. The nanoscale films conform to
the underlying structure of the TP layer and are sufficient to prevent
the adhesion of red blood cells and platelets.