How Crystallographic Orientation-Induced Fibrinogen Conformation Affects Platelet Adhesion and Activation on TiO2

Control of protein adsorption is essential for successful integration of healthcare materials into the body. Human plasma fibrinogen (HPF), especially its conformation is a key upstream regulator for platelet behavior and thus pathological clot formation at the blood-biomaterial interface. A previous study by the authors revealed that the conformation of adsorbed HPF can be controlled by rutile surface crystallographic orientation. Therefore, it is hypothesized that pre-adsorbed HPF on specific rutile orientation can regulate platelets adhesion and activation. Here, it is shown that platelets exposed to the four low index (110), (100), (101), (001) facets of TiO₂ (rutile) exhibit surface-specific behavior. Scanning electron microscopy (SEM) observations of platelets morphology and P-selectin expression measurement revealed that on (110) facets, platelets adhesion and activation are suppressed. In contrast, extensive surface coverage by fully activated platelets is observed on (001) facets. Platelets' behavior has been linked to the HPF conformation and thereby availability of platelet-binding sequences. Atomic force microscopy (AFM) imaging supported by immunochemical analysis shows that on (110) facets, HPF is adsorbed in trinodular conformation rendering the γ^400-411 platelet-binding sequence inaccessible. This research has potential implications on the bioactivity of different materials crystal facets, reducing the risk of pathological clot formation and thromboembolic complications.

Preliminary investigation of the dissolution behavior, cytocompatibility, effects of fibrinogen conformation and platelet adhesion for radiopaque embolic particles

Experimental embolic particles based on a novel zinc-silicate glass system have been biologically evaluated for potential consideration in transcatheter arterial embolization procedures. In addition to controlling the cytotoxicity and haemocompatibility for such embolic particles, its glass structure may mediate specific responses via dissolution in the physiological environment. In a 120 h in-vitro dissolution study, ion release levels for silicon (Si4+), sodium (Na+), calcium (Ca2+), zinc (Zn2+), titanium (Ti4+), lanthanum (La3+), strontium (Sr2+), and magnesium (Mg2+), were found to range from 0.04 to 5.41 ppm, 0.27-2.28 ppm, 2.32-8.47 ppm, 0.16-0.20 ppm, 0.12-2.15 ppm, 0.16-0.49 ppm and 0.01-0.12 ppm, respectively for the series of glass compositions evaluated. Initial release of Zn2+ (1.93-10.40 ppm) was only evident after 120 h. All compositions showed levels of cell viabilities ranging from 61.31 ± 4.33% to 153.7 ± 1.25% at 25%-100% serial extract dilutions. The conformational state of fibrinogen, known to induce thrombi, indicated that no changes were induced with respect of the materials dissolution by-products. Furthermore, the best-in-class experimental composition showed equivalency to contour PVA in terms of inducing platelet adhesion. The data generated here provides requisite evidence to continue to in-vivo pre-clinical evaluation using the best-in-class experimental composition evaluated.