Layer-by-layer self-assembly of two polysaccharides, hyaluronan (HA) and chitosan (CH), was employed to engineer bioactive coatings for endovascular stents. A polyethyleneimine (PEI) primer layer was adsorbed on the metallic surface to initiate the sequential adsorption of the weak polyelectrolytes. The multilayer growth was monitored using a radiolabeled HA and shown to be linear as a function of the number of layers. The chemical structure, interfacial properties, and morphology of the self-assembled multilayer were investigated by time-of-flight secondary ions mass spectrometry (ToF-SIMS), contact angle measurements, and atomic force microscopy (AFM), respectively. Multilayer-coated NiTi disks presented enhanced antifouling properties, compared to unmodified NiTi disks, as demonstrated by a decrease of platelet adhesion in an in vitro assay (38% reduction; p = 0.036). An ex vivo assay on a porcine model indicated that the coating did not prevent fouling by neutrophils. To assess whether the multilayers may be exploited as in situ drug delivery systems, the nitric-oxide-donor sodium nitroprusside (SNP) was incorporated within the multilayer. SNP-doped multilayers were shown to further reduce platelet adhesion, compared to standard multilayers (40% reduction). When NiTi wires coated with a multilayer containing a fluorescently labeled HA were placed in intimate contact with the vascular wall, the polysaccharide translocated on the porcine aortic samples, as shown by confocal microscopy observation of a treated artery. The enhanced thromboresistance of the self-assembled multilayer together with the antiinflammatory and wound healing properties of hyaluronan and chitosan are expected to reduce the neointimal hyperplasia associated with stent implantation.

Membrane-covered devices could help treat disease of the vasculature such as aneurysm, rupture, and fistulas. They are also investigated to reduce embolic complication associated with revascularization of saphenous vein graft. The aim of this study is to design a clinically applicable biodegradable membrane-covered stent based on the natural polysaccharide chitosan, which has been developed. The mechanical properties of the membrane is optimized through blending with polyethylene oxide (70:30% Wt CH:PEO). The membrane was able to sustain the mechanical deformation of the supporting self-expandable metallic stents during its deployment. The membrane was demonstrated to resist physiological transmural pressure (burst pressure resistance >500 mm Hg) and presented a high-water permeation resistance (1 mL/cm(2) min(-1) at 120 mmHg). The CH-PEO membrane showed a good hemocompatibility in an ex vivo assay. Heparin and hyaluronan surface complexation with the membrane further reduced platelet adhesion by 50.1 and 63% (p = 0.05). The ability of the membrane-covered devices to be used as a drug reservoir was investigated using the nitric oxide donor sodium nitroprusside (SNP). SNP-loaded membranes displayed significantly reduced platelet adhesion.

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