An Ultrasound Contrast Agent Targeted to P-Selectin Detects Activated Platelets at Supra-Arterial Shear Flow Conditions

Abstract

Objectives To evaluate targeting of a microbubble contrast agent to platelets under high shear flow using the natural selectin ligand sialyl Lewisa. Materials and Methods Biotinylated polyacrylamide Sialyl Lewisa or biotinylated carbohydrate-free polymer (used as a control) were attached to biotinylated microbubbles via a streptavidin linker. Activated human platelets were isolated and attached to fibrinogen-coated culture dishes. Fibrinogen-coated dishes without platelets or platelet dishes blocked by an anti-P-selectin antibody served as negative control substrates. Dishes coated by recombinant P-selectin served as a positive control substrate. Microbubble adhesion was assessed by microscopy in an inverted parallel plate flow chamber, with wall shear stress values of 40, 30, 20, 10 and 5 dynes/cm2. The ratio of binding and passing microbubbles was defined as capture efficiency. Results There was no significant difference between the groups regarding the number of microbubbles in the fluid flow at each shear rate. Sialyl Lewisa-targeted microbubbles were binding and slowly rolling on the surface of activated platelets and P-selectin-coated dishes at all the flow conditions including 40 dynes/cm2. Capture efficiency of targeted microbubbles to activated platelets and recombinant P-selectin decreased with increasing shear flow: at 5 dynes/cm2, capture efficiency was 16.11% on activated platelets vs. 21.83 % on P-selectin, and, at 40 dynes/cm2, adhesion efficiency was still 3.4 % in both groups. There was neither significant adhesion of Sialyl Lewisa-targeted microbubbles to control substrates, nor adhesion of control microbubbles to activated platelets or to recombinant P-selectin. Conclusions Microbubble targeting using sialyl Lewisa, a fast-binding ligand to P-selectin, is a promising strategy for the design of ultrasound contrast binding to activated platelets under high shear stress conditions.

Contrast-enhanced molecular ultrasound differentiates endoglin genotypes in mouse embryos

“…We employed parallel plate flow chambers, which are used to investigate the fluid shear rates, particle size, concentration and ligand and target site density requirements for promoting microbubble adhesion [9,42,[57][58][59][60][61][62]. Flow experiments initially conducted with microbubbles suspended in cell media demonstrated that microbubble binding was almost completely inhibited under this condition, likely due to media blocking microbubble-conjugated antibodies.…”

Phase-transition Perfluorocarbon Nanoparticles for Ultrasound Molecular Imaging and Therapy

“…Drugloaded microbubbles would be attractive ultrasoundresponsive drug carriers. The approach that drugloaded microbubbles or phase-shift nanoparticles be beneficial for drug targeting to intravascular targets would be a dramatic ultrasound-responsive drug transportation [88,89,[91][92][93].…”

The Evolution of Ultrasound Technologies; from Anatomic to Physiologic,Histologic, and Molecular Imaging

“…αvβ3 integrin, cyclic arginine-glycineaspartic acid (RGD) peptide and knottin peptides have been targeted with microbubbles [28,29]. Clot imaging is important for myocardial infarction, deep venous thrombosis/pulmonary embolism and stroke assessment with Microbubble targeting to glycoprotein IIb-IIIa receptors and P-selectin ligand [30].…”