Surface modification of bioresorbable electrospun matrices with heparin and lysozyme for vascular tissue engineering

P.C. CARACCIOLO; I. RIAL-HERMIDA; F. MONTINI BALLARIN; G.A. ABRAHAM; A. CONCHEIRO-NINE; C. ÁLVAREZ-LORENZO

Santiago de Compostela

Congreso; IX Foro Internacional Cátedra Iberoamericana-Suiza de Desarrollo de Medicamentos (CISDEM 2015); 2015

Facultad de Farmacia, Universidad de Santiago de Compostela

The development of tissue-engineered vascular prostheses is still a challenge, and many approaches are currentlybeing investigated. Poly(L-lactic acid) (PLLA), a FDA approved bioresorbable polyester presenting mechanicalproperties close to collagen, such as high elastic modulus, and good electro-spinnability, and a bioresorbablesegmented polyurethane (SPU) elastomer mimicking elastin mechanical properties, such as tensile strength andcompliance, were processed by multilayer electrospinning to obtain a novel bilayered vascular graft. Thematerials were processed in two different compositions: PLLA/SPU 50/50 blend (inner layer) and PLLA/SPU90/10 blend (outer layer) [1], each of them mimicking the collagen-elastin ratio presented in the media andadventitia layers of natural arteries, respectively. One of the main drawbacks to the use of implantable devicesand matrices for tissue engineering is the high risk of infection and thrombosis. The immobilization of polymersor biomolecules on surfaces can avoid these difficulties. Heparin is a glycosaminoglycan, which has been widelyused in vascular therapy due to its high anticoagulant capacity, preventing thrombosis events on syntheticsurfaces [2]. Moreover, lysozyme is an antibacterial enzyme capable of hydrolyze the peptidoglycan layer ofGram-positive bacteria cell walls [3]. In this work, electrospun matrices of PLLA/SPU 50/50 blend (as the innerlayer of vascular grafts) were surface modified through the immobilization of heparin and lysozyme, asanticoagulant and antibacterial, respectively. The modification through ester and urethane functional groups wasexplored. In the ester route, an alkaline treatment was employed to increase the density of PLLA reactivecarboxylic groups. Then, diaminoPEG (DAPEG) was employed as spacer to avoid a reduction in heparin activitydue to limited mobility. In the urethane route, a NaClO treatment was employed to activate SPU urethanefunctional groups. Further modification with allyl glycidyl ether generated epoxy-capped oligomers. This stepwas followed by DAPEG modification. From then on, both routes followed with heparin modification.Moreover, a matrix prepared by each route was exposed to a lysozyme solution to form a heparin-lysozymecomplex, due to lysozyme has a relatively low stability in its free state. MSC proliferation on modified scaffoldsresulted in the order of the control, being higher for the lysozyme modified scaffolds. Cell proliferation reachedits maximum at day 7. After this, the values decreased for all scaffolds. It was previously reported that a highproliferation inhibits further cell growth. Moreover, live-dead staining showed cells were able to growth onto thescaffolds, displaying better cytocompatibility the matrices obtained through urethane route. Lysozyme activitywas evaluated through m. lysodeikticus suspensions. The immobilized lysozyme remained active for bothmodification routes, being more active the matrix obtained through urethane route. Thus, from the obtainedresults, it can be concluded that the urethane route seems to be the most promising for covalent modification ofPLLA/SPU 50/50 blends.