Development of polymer microcapsules functionalized with fucoidan to target P-selectin under arterial flow conditions

Introduction The lack of technology, which enables early detection and predicts rupture risk of aneurysms hampers their diagnosis and treatments. P-selectin expressed by activated platelets and endothelial cells is a marker of... [ view full abstract ]

Introduction
The lack of technology, which enables early detection and predicts rupture risk of aneurysms hampers their diagnosis and treatments. P-selectin expressed by activated platelets and endothelial cells is a marker of biologically active arterial thrombi. Our group previously demonstrated that fucoidan-based systems could target P-selectin to detect platelet and endothelial activation in vivo. Therein, microcapsules (MCs) made of polycyanoacrylate and polysaccharide and functionalized with fucoidan (Fuco-MCs) were designed as new carriers to target P-selectin. Flow channels were used to visualize and quantify the affinity of Fuco-MCs for P-selectin and for human activated platelet aggregates expressing P-selectin in arterial flow conditions.

Methods
Microcapsules (MCs) were synthesized by anionic emulsion polymerization in alkaline condition. Vena8 Fluoro+ chambers were coated with a solution either with recombinant P-, E- or L-selectin. Some channels had different doses of P-selectin to confirm that the affinity of Fuco-MCs for P-selectin was depended on the concentration of P-selectin. A suspension of MCs or Fuco-MCs was passed through the channels (shear stress 1,500 s-1). In the second experiment, whole human blood was firstly injected into collagen coated channels to induce platelets activation and aggregation, subsequently MCs or Fuco-MCs were injected in the channels, visualized and quantified under fluorescence microscopy.

Results
In this work we, developed microcapsules with a new alkaline solvent emulsion-evaporation polymerization process, confirmed their hydrodynamic diameter distribution, the microcapsule structure and the presence of the targeting agent, fucoidan, at the surface. Fuco-MCs bound significantly more to the P-selectin coating than MCs, and results indicated a dose-dependent effect while increasing the concentration of P-selectin. Furthermore, their adhesion to L- and E-selectins was significantly lower than to P-selectin. Moreover, only Fuco-MCs accumulated at the surface of platelet aggregates.

Conclusion
This work gave the first evidence that microcapsules can be obtained according to one-step polymerization process of isobutyl cyanoacrylate in alkaline conditions. Subsequently, the microcapsule surface is functionalized by fucoidan, which gives microcapsules the property of specificity to P-selectin under blood flow conditions. Meanwhile, organic core is considered as a potential loading space of probe and/or hydrophobic drug for the diagnosis and/or the treatment of vascular diseases overexpressing P-selectin.