One-year performance of biorestorative polymeric coronary bypass grafts in an ovine model: correlation between early biomechanics and late serial Quantitative Flow Ratio

OBJECTIVES: This study aimed to investigate the impact of mechanical factors at baseline on the patency of a restorative conduit for coronary bypass grafts in an ovine model at serial follow-up up to 1 year.METHODS: The analyses of 4 mechanical factors [i.e. bending angle, superficial wall strain and minimum and maximum endothelial shear stress (ESS)] were performed in 3D graft models reconstructed on baseline (1-month) angiograms frame by frame by a core laboratory blinded for the late follow-up. The late patency was documented by Quantitative Flow Ratio (QFR (R)) that reflects the physiological status of the graft. The correlation between 4 mechanical factors and segmental QFR (Delta QFR) were analysed on 10 equal-length segments of each graft.RESULTS: A total of 69 graft geometries of 7 animals were performed in the study. The highest Delta QFR at 12 months was colocalized in segments of the grafts with the largest bending angles at baseline. Higher Delta QFR at 3 months were both at the anastomotic ends and were colocalized with the highest superficial wall strain at baseline. High baseline ESS was topographically associated with higher Delta QFR at the latest follow-up. Correlations of minimum and maximum ESS with Delta QFR at 3 months were the strongest among these parameters (rho = 0.30, 95% CI [-0.05 to 0.56] and rho = 0.27, 95% CI [-0.05 to 0.54], respectively).CONCLUSIONS: Despite the limited number of grafts, this study suggests an association between early abnormal mechanical factors and late flow metrics of the grafts. The understanding of the mechanical characteristics could help to improve this novel conduit

Processing and characterization of alpha-elastin electrospun membranes

Elastin isolated from fresh bovine ligaments was dissolved in a mixture of 1,1,1,3,3,3-Hexafluoro-2-propanol and water were electrospun into fiber membranes under different processing conditions. Fiber mats of randomly and aligned fibers were obtained with fixed and rotating ground collectors and fibrils were composed by thin ribbons whose width depends on electrospinning conditions; fibrils with 721 nm up to 2.12 μm width were achieved. After cross-linking with glutaraldehyde, α-elastin can uptake as much as 1700 % of PBS solution and a slight increase on fiber thickness was observed. The glass transition temperature of electrospun fiber mats was found to occur at ˜80 °C. Moreover, α-Elastin showed to be a perfect elastomeric material, and no mechanical hysteresis was found in cycle mechanical measurements. The elastic modulus obtained for random and aligned fibers mats in a PBS solution was 330±10 kPa and 732±165 kPa, respectively. Finally, the electrospinning and cross-linking process does not inhibit MC-3T3-E1 cell adhesion. Cell culture results showed good cell adhesion and proliferation in the cross-linked elastin fiber mats.This work is funded by FEDER funds through the "Programa Operacional Factores de Competitividade-COMPETE" and by national funds arranged by FCT-Fundacao para a Ciencia e a Tecnologia, project references NANO/NMed-SD/0156/2007, PTDC/CTM-NAN/112574/2009, and PEST-C/FIS/UI607/2011. The authors also thank funding from "Matepro-Optimizing Materials and Processes", ref. "NORTE-07-0124-FEDER-000037", cofunded by the "Programa Operacional Regional do Norte" (ON.2-O Novo Norte), under the "Quadro de Referencia Estrategico Nacional" (QREN), through the "Fundo Europeu de Desenvolvimento Regional" (FEDER). The authors also thank support from the COST Action MP1003, 2010 'European Scientific Network for Artificial Muscles'. VS, JP, JS, and DMC thank the FCT for the SFRH/BD/48708/2008, SFRH/BD/64901/2009, SFRH/BPD/64958/2009 and SFRH/BPD/63148/2009, and SFRH/BD/82411/2011 grants, respectively. JLGR acknowledges the support of the Spanish Ministry of Science and Innovation through project No. MAT2010-21611-C03-01 (including the FEDER financial support). CIBER-BBN is an initiative funded by the VI National R&D&i Plan 2008-2011, Iniciativa Ingenio 2010, Consolider Program, CIBER Actions and financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund