NMR studies of advanced materials for cartilaginous prostheses

In recent years, the interest in materials applications in the biomedical area has increased considerably, with the aim of minimizing the immune response to a foreign body. The design and manufacture of biomaterials refers to different scientific aspects and must fulfill specific requests. In particular, a profound analysis of the chemical, physical and biological characteristics of the environment in which the material is supposed to act is of fundamental importance. The acquired knowledge can lead to a better understanding of the factors that determine the final action of the materials, thus allowing the optimization of their design. Polymers offer the advantage of being engineered and processed in different ways to meet specific requirements for end use unlike other types of materials such as metals and ceramics. Nowadays, one of the main fields in the application of polymeric biomaterials is tissue engineering that aims to repair, conserve or improve tissues and organs through synergistic interactions between living cells and synthetic materials. In the field of regenerative medicine, biopolymers are becoming increasingly important in particular in the degeneration of the intervertebral discs involving the Nucleus pulposus (NP), for which timely intervention is able to prevent further degradation of the fibrous ring. The composition of human NP is made up of a matrix of proteoglycans, collagen and other proteins with dispersed water as a mobile phase. [1] This water content decreases by 90% at birth up to 30% in old age. In the NP several glycosaminoglycans such as versican and hyaluronan have been identified [2], and the latter was initially tested for replacement, but it was shown to be rapidly degraded even when it is in the form of high viscosity solutions. Cross-linking decreases the degradation rate, but it is not sufficient to lower the speed of the enzymatic processes and therefore makes this polymer unusable in this application, in which a NP substitute obviously can not be degraded [3]. An ideal material should have characteristics similar to those of hyaluronan without however presenting the unfavorable feature of degradability. Starting from alginic acid (AA), an amide alginic acid (AAA) [4] was synthesized in order to obtain a material that possessed the chemical-physical properties similar to that of hyaluronate without losing the rigidity of the native alginate structure. In this study the structural characteristics and the motion properties of AA and AAA were examined, with particular focus on the chain organization and the three-dimensional arrangement by means of 1D, 2D NMR spectroscopy and longitudinal relaxation time measurements T1. References [1] J.C. Iatridis, M. Weidenbaum , L.A. Setton,V.C. Mow Spine 1996, 21, 1174-1184. [2] J.A. Buckwalter Spine 1995, 20, 1307-1314. [3] R. Barbucci, S. Lamponi, A. Borzacchiello, L. Ambrosio, M. Fini, P. Torricelli, R. Giardino Biomaterials 2002, 23, 4503-4513. [4] G. Leone, P. Torricelli, A. Chiumiento, A. Facchini, R. Barbucci J Biomed Mater Res 2008, 84A, 391-401.