Bilayered Electrospun small-diameter vascular grafts with improved in vitro biological response

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

Otranto

Congreso; 4° International Conference on Electrospinning (Electrospin 2016); 2016

Universidad de Salento

The production of asmall-diameter vascular graft (SDVG, < 6 mm) with an appropriate biomechanicalresponse still presents a challenge. The development of an off-the-shelfconduit, without long in vitro culture periods, with proper biologicaland mechanical properties for coronary bypass surgery is the principalchallenge of vascular tissue engineering current studies. The ideal SDVG mustachieve numerous attributes: biocompatibility, no thrombogenicity, no toxicity,resistance to infection and neointimal hyperplasia, mechanical compliance, suturability,flexibility and elasticity without twisting collapse, capacity of locallytherapeutic agents release, and potential tissue regeneration. In previous works,we developed a bilayered nanofibrous bioresorbable electrospunconduit from poly(L-lacticacid) (PLLA) and segmented poly(ester urethane) (PHD) blends, by mimicking thenatural collagen-to-elastin ratio in the media and adventitia layers [1,2]. Thebiomimetic mechanical response was fully studied by uniaxialtension, suture, dynamical compliance, and burst pressure, displaying abehavior in the range of natural vessels. Invitro degradation studies suggested that degradation time would match therequired for regeneration process. Inthis work, modification of inner surface SDVG was studied. Heparin and lyzosime immobilization wasperformed to introduce antithrombogenic properties and to reduce the risk ofinfection after implantation, respectively. Two strategies were explored. Inthe first one, PLLA carboxylic groups? density was increased through analkaline treatment and then reaction with diaminoPEG (DAPEG) was performed. Inthe second one, PHD urethane groups were activated with sodium hypochlorite,and then reacted with allyl glycidyl ether. DAPEG modification was performedthrough the reaction of epoxy-capped oligomers with DAPEG amino terminalgroups. Both strategies followed with heparin immobilization. Furthermore,lysozyme loading to obtain heparin-lysozyme electrostatic complex was alsoperformed. Although the urethane route allowed higher heparin immobilization,both routes displayed good heparinization density. In vitro studies revealed a 90% reduction in platelet adhesion afterheparin modification. Moreover, mesenchymal stem (MSC) cells proliferation wasnot reduced after modification, which indicates that immobilization did notinduce cytotoxicity on MSC. Lysozyme activity was evaluated through m. lysodeikticus suspensions. Lysozyme remained active after immobilization and itsactivity showed a direct dependence with heparin content. Thus, the matrixobtained through urethane route displayed higher lysozyme activity. Finally,both strategies resulted adequate for heparin and lysozyme immobilization,being promising strategies for small diameter vascular graft modification.