



@article {3285,
	title = {Selective albumin-binding surfaces modified with a thrombin-inhibiting peptide},
	journal = {Acta Biomaterialia},
	volume = {10},
	year = {2014},
	note = {Export Date: 21 November 2014},
	month = {2014},
	pages = {1227 - 1237},
	abstract = {Blood-contacting medical devices have been associated with severe clinical complications, such as thrombus formation, triggered by the activation of the coagulation cascade due to the adsorption of certain plasma proteins on the surface of biomaterials. Hence, the coating of such surfaces with antithrombotic agents has been used to increase biomaterial haemocompatibility. Biomaterial-induced clotting may also be decreased by albumin adsorption from blood plasma in a selective and reversible way, since this protein is not involved in the coagulation cascade. In this context, this paper reports that the immobilization of the thrombin inhibitor D-Phe-Pro-D-Arg-D-Thr-CONH 2 (fPrt) onto nanostructured surfaces induces selective and reversible adsorption of albumin, delaying the clotting time when compared to peptide-free surfaces. fPrt, synthesized with two glycine residues attached to the N-terminus (GGfPrt), was covalently immobilized onto self-assembled monolayers (SAMs) having different ratios of carboxylate-hexa(ethylene glycol)- and tri(ethylene glycol)-terminated thiols (EG6-COOH/EG3) that were specifically designed to control GGfPrt orientation, exposure and density at the molecular level. In solution, GGfPrt was able to inactivate the enzymatic activity of thrombin and to delay plasma clotting time in a concentration-dependent way. After surface immobilization, and independently of its concentration, GGfPrt lost its selectivity to thrombin and its capacity to inhibit thrombin enzymatic activity against the chromogenic substrate n-p-tosyl-Gly-Pro-Arg-p-nitroanilide. Nevertheless, surfaces with low concentrations of GGfPrt could delay the capacity of adsorbed thrombin to cleave fibrinogen. In contrast, GGfPrt immobilized in high concentrations was found to induce the procoagulant activity of the adsorbed thrombin. However, all surfaces containing GGfPrt have a plasma clotting time similar to the negative control (empty polystyrene wells), showing resistance to coagulation, which is explained by its capacity to adsorb albumin in a selective and reversible way. This work opens new perspectives to the improvement of the haemocompatibility of blood-contacting medical devices. {\textcopyright} 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.},
	keywords = {Albumin, Blood compatibility, Clotting, Surface modification, Thrombin},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84895067841\&partnerID=40\&md5=8486186625f8f4f1cbc538bb3e34dd82},
	author = {Freitas, S.C. and Maia, S. and Figueiredo, A.C. and Gomes, P. and Pereira, P.J.B. and Barbosa, M.A. and Martins, M.C.L.}
}
@booklet {2190,
	title = {Bioengineered surfaces to improve the blood compatibility of biomaterials through direct thrombin inactivation},
	howpublished = {Acta BiomaterialiaActa Biomater.},
	year = {2012},
	note = {Export Date: 21 November 2012Source: ScopusArticle in Pressdoi: 10.1016/j.actbio.2012.07.020Language of Original Document: EnglishCorrespondence Address: Martins, M.C.L.; INEB - Instituto de Engenharia Biom{\'e}dica, Universidade do Porto, Rua do Campo Alegre 823, 415email: cmartins@ineb.up.pt},
	month = {2012///},
	abstract = {Thrombus formation, due to thrombin generation, is a major problem affecting blood-contacting medical devices. This work aimed to develop a new strategy to improve the hemocompatibility of such devices by the immobilization of a naturally occurring thrombin inhibitor into a nanostructured surface. Boophilin, a direct thrombin inhibitor from the cattle tick Rhipicephalus microplus, was produced as a recombinant protein in Pichia pastoris. Boophilin was biotinylated and immobilized on biotin-terminated self-assembled monolayers (SAM) via neutravidin. In order to maintain its proteinase inhibitory capacity after surface immobilization, boophilin was biotinylated after the formation of a boophilin-thrombin complex to minimize the biotinylation of the residues involved in thrombin-boophilin interaction. The extent of boophilin biotinylation was determined using matrix-assisted laser desorption/ionization-time of flight/time of flight mass spectrometry. Boophilin immobilization and thrombin adsorption were quantified using quartz crystal microbalance with dissipation. Thrombin competitive adsorption from human serum was assessed using                        125I-thrombin. Thrombin inhibition and plasma clotting time were determined using spectrophotometric techniques. Boophilin-coated SAM were able to promote thrombin adsorption in a selective way, inhibiting most of its activity and delaying plasma coagulation in comparison with boophilin-free surfaces, demonstrating boophilin{\textquoteright}s potential to improve the hemocompatibility of biomaterials used in the production of blood-contacting devices. {\textcopyright} 2012 Acta Materialia Inc.
},
	keywords = {Coagulation, Hemocompatibility, Protein adsorption, Surface functionalization, Thrombin},
	isbn = {17427061 (ISSN)},
	url = {http://www.scopus.com/inward/record.url?eid=2-s2.0-84865246462\&partnerID=40\&md5=278b2e7d1427a6032eba9ecbd01c3872},
	author = {Freitas, S.C. and Cereija, T.B. and Figueiredo, A.C. and Os{\'o}rio, H. and Pereira, P.J.B. and Barbosa, M.A. and Martins, M.C.L.}
}
