Modification of layered atelocollagen bv ultraviolet irradiation and chemical &oss-linking: structure stability and mechanical properties zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPON K. ViztiovB, D. BakoS, M. RehGkovB and V. Macho Faculty of Chemical Technology, Slovak Technical University, Department of Printing Technology and Applied Photochemistry, Radlinsk6ho 9, 812 37 Bratislava, Slovakia Physical and chemical modifications of atelocollagen materials have been carried out to improve their physical, chemical and biological properties. We have studied the influence of physical modification using ultraviolet irradiation and of chemical modification using hexamethylene diisocyanate on the physical properties of layered atelocollagen materials. The study evaluated the structural stability of cross-linked materials using swelling experiments. Influence on mechanical properties is also discussed. Biomaterials (1994) zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA 15, (13) 1062-1086 Keywords: Cross-linking, collagens, mechanical properties, swelling Received 29 September 1993; accepted 18 February 1994 Successes in the field of biomaterial engineering are usually connected with the replacement or reconstruc- tion of organs and tissues in modern surgery. Attention in this field is paid to two broad conceptual problems. The first concerns the difficulty of replacing tissues that are living, highly organized but dynamically responsive and structurally complex materials, with synthetic materials that are non-living and structurally native and unresponsive. The second includes interac- tions of replacement materials with tissues of the body and understanding the phenomena connected with the interface reaction’. One way of partially solving these problems is the formation of biomaterials which are based on biopoly- mers. Currently, collagen is seen as a useful and important biomaterial’. Collagen possesses characteris- tics as a biomaterial distinct from those of synthetic polymers. The most distinct is its mode of interaction with the body. The immunochemical properties of collagen are now well established3 and treatments to reduce its antigenicity have been commonly used4s5. It is also known that cross-linking minimizes the anti- genicity of the collagen biomateria16, 7. Collagen is absorbed in tissue through catabolic processes, includ- ing degradation with extracellular collagenolytic enzymes and phagocytosis. Resorption control of the collagen biomaterial is essential where it is used for tissue regeneration. Synchronization of collagen resorp- tion and tissue regeneration rates is important to obtain satisfactory regeneration’. Correspondence to Dr D. BakoS In order to gain a satisfactory result from collagen used as a biomaterial, it becomes necessary to improve its physical, chemical and biological properties for some applications in surgery. Physical modification with ultraviolet irradiation and chemical modification are useful for improving these properties. In this paper, we present the first part of the results evaluating modifications of two types of atelocollagen samples. We have used ultraviolet irradiation and chemical treatment with hexamethylene diisocyanate, both of which have cross-linking effects on collagen. Attention is paid to the structural stability of the materi- als and/ or the cohesion of the fibrous net of both the fibrous layer and parchment-like film (membrane). We have studied the swelling process and mechanical properties of these biomaterials. zyxwvutsrqponmlkjihgfedcbaZY EXPERIM ENTA L Atelocollagen prepared from bovine Achilles tendon (Hypro, Czech Republic) was disintegrated and types of base materials were prepared by different procedures. The first material (the fibrous layer) was intensively washed with ethanol to obtain a porous structure after formation from water dispersion and immediately dried under vacuum (Figure ~a). The second parchment-like material was prepared from mechanically treated dispersion of atelocollagen in distilled w ater. We obtained material with high cohesion of fibrous structure, lower porosity and Biomaterials 1994, Vol. 15 No. 13 0 1994 Butterworth-Heinemann Ltd 0275~5408/94/131082-05