Collagenous Porous Structures for the Development of an Artificial Small Diameter Blood Vessel

s / 87 (2003) 199–308 295 Fig. 1. Effect of fetal calf serum (FCS) on transfection efficiency in COS-1 cells obtained with trimethylated chitosan oligomers /DNA complexes at different weight /weight ratios. Values are mean6S.D. (n53). References [1] A.B. Sieval, M. Thanou, A.F. Kotze, J.C. Verhoef, J. Brussee, H.E. Junginger, Preparation and NMR-characterization of highly substituted N-Trimethyl chitosan chloride. Carbohydr. Polym. 36 (1998) 157–165. [2] M. Thanou, B.I. Florea, M. Geldof, H.E. Junginger, G. Borchard, Quaternized chitosan oligomers as novel gene delivery vectors in epithelial cell lines. Biomaterials 23 (1) (2002) 153–159. VII. Tissue Engineering COLLAGENOUS POROUS STRUCTURES FOR THE DEVELOPMENT OF AN ARTIFICIAL SMALL DIAMETER BLOOD VESSEL L. Buttafoco, P.J. Dijkstra, A.A. Poot, I. Vermes, J. Feijen Institute for BioMedical Technology (BMTI), Polymer Chemistry and Biomaterial Group, Dept. of Chemical Technology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands Introduction Repairing blood vessels affected by atherosclerosis is still a partially unsolved issue, in particular when dealing with grafts having a diameter smaller than 6 mm [1]. Some of the problems encountered are limited donor availability and thrombosis, together with blood-material interactions, which start almost immediately when a foreign material is implanted in the body [2]. Since synthetic materials often stimulate the formation of thrombotic occlusion and intimal hyperplasia [3], natural materials such as collagen were introduced. Our aim is to build a three-layered tubular structure, eventually implantable in humans, where collagen, one of the most abundant proteins of the extracellular matrix, is chosen as the main constituent of the media layer. In the blood vessel wall fibre forming species of collagen, like type I collagen, are in fact particularly abundant. Besides this, collagen is a suitable scaffold for the proliferation and growth of smooth muscle cells (SMC) whose seeding is needed for the development of those extracellular matrix components which will form the new blood vessel. On the other hand, collagen has a certain degree of antigenicity, which must be taken into consideration when dealing with tissue engineering applications. In order to decrease this antigenicity, collagen is crosslinked. In this work, the porosity of collagenous tubes, prepared by freeze-drying, and the effect of different crosslinking methods on the morphological characteristics of the pores are analysed. Pores are in fact needed in order to achieve a homogeneous distribution of SMC in the tube itself. 296 Abstracts / 87 (2003) 199–308 Experimental methods Type I insoluble collagen (1 g) derived from Bovine Achilles Tendon (Sigma, St. Louis, MO) is swollen overnight in 0.05 M acetic acid solution (50 ml) at 4 8C. The mixture is dispersed with 50 g of crushed ice for 4 min in a Philips Blender and then homogenised for 15 min at 4 8C using an Ultra-Turrax T25 (IKA Labortechnik, Staufen, BRD). The resulting suspension is poured in a mandrel such as the one shown in Fig. 1, before being frozen. Freezing is performed at different temperatures (25 8C, 215 8C, 218 8C, 222 8C, 235 8C and 2196 8C). The samples are then freeze-dried overnight.