Protein-Loaded Bioresorbable Fibers and Expandable Stents: Mechanical Properties and Protein Release

There is an increasing interest in bioresorbable polymeric stents for coronary, urethral and tracheal applications. These stents can support body conduits during their healing process and release biologically active agents from an internal reservoir to the surrounding tissue. A removal operation is not needed. Bioresorbable poly(L-lactic acid) fibers were prepared through melt spinning accompanied by a postpreparation drawing process. Novel expandable bioresorbable stents were developed from these fibers. Bioresorbable microspheres containing albumin were prepared and attached to the stents, to serve as a protein reservoir coating. The controlled release of albumin from the microsphere-loaded stent was studied. The fibers combine high strength and modulus, together with good ductility and flexibility. An increase in draw ratio increases the tensile strength and modulus and decreases the ultimate strain. The stents demonstrated excellent initial radial compression strength and good in vitro degradation resistivity, which makes them applicable for supporting blood vessels for at least 20 weeks. Microspheres bound to these stents enable effective protein loading, without reducing the stent's mechanical properties. The protein release from the microsphere-loaded stent occurs by diffusion, is determined mainly by the initial molecular weight of the bioresorbable polymer and its erosion rate, and is strongly affected by the microsphere structure.