Modulated growth, stability and interactions of liquid-like coacervate assemblies of elastin

Elastin self-assembles from monomers into polymer networks that display elasticity and resilience. The first major step in assembly is a liquid-liquid phase separation known as coacervation. This process represents a continuum of stages from initial phase separation to early growth of droplets by coalescence and later "maturation" leading to fiber formation. Assembly of tropoelastin-rich globules is on pathway for fiber formation in vivo. However, little is known about these intermediates beyond their size distribution. Here we investigate the contribution of sequence and structural motifs from full-length tropoelastin and a set of elastin-like polypeptides to the maturation of coacervate assemblies, observing their growth, stability and interaction behavior, and polypeptide alignment within matured globules. We conclude that maturation is driven by surface properties, leading to stabilization of the interface between the hydrophobic interior and aqueous solvent, potentially through structural motifs, and discuss implications for droplet interactions in fiber formation

Interstitial fibrin-fibronectin deposition with T cell infiltrates precedes fibrosis in murine viral myocarditis

This study was carried out to investigate interstitial fibrin and fibronectin deposition and subsequent myocardial connective tissue abnormalities in BALB/c-nu/ + (euthymic and normal T cell function) and BALB/c-nu/nu (athymic and T cell-deficient) mice. Both types of mice were inoculated with encephalomyocarditis virus and sacrificed periodically. Sections of the hearts were stained with haematoxylin-eosin, trichrome, lymphocyte subsets, silver impregnation, and fibrin or fibronectin. In addition, myocardial collagen concentration was measured. Interstitial fibrin and fibronectin appeared in parallel with inflammatory T lymphocytes and myocardial necrosis in the BALB/c-nu/ + mice. The changes increased until 14 days, subsequently decreasing with time. Interstitial fibrosis and abnormal reticulin fibres were absent until 7 days postinfection, and then increased with time until 60 days. In BALB/c-nu/nu mice, in contrast, although myocardial necrosis and fibrin-fibronectin deposition associated with immature T lymphocytes were evident on days 7 and 14, subsequent myocardial fibrosis and reticulin fibre abnormalities were minimal on days 30 and 60. In BALB/c-nu/ + mice, myocardial collagen concentration increased on day 30, but it did not in BALB/c-nu/nu mice. Thus, interstitial fibrin-fibronectin deposition resulting from virus-induced and T lymphocyte-mediated myocyte necrosis precedes the subsequent development of interstitial fibrosis and abnormal reticulin architectures in this model of murine myocarditis

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