Medical device a partire da materiale biologico

The development of medical devices presupposes the preliminary identification of the starting biological material, which in this PhD thesis was chosen as bovine pericardium. For its effective clinical application, the bovine pericardium must be decellularized to eliminate the native cells in order to obtain a three-dimensional structure given solely by the proteins constituting the extracellular matrix (ECM). The process designed and developed in Assut Europe S.p.A. consists of a 4-day chemical treatment alternating with washing phases in ultra-purified water to remove any processing residues. The success of the method is demonstrated with DAPI staining and with histological staining with hematoxylin/eosin on sections of native pericardium and on sections of decellularized pericardium, where it was possible to observe, in both cases, the complete absence of residual nuclei and the preservation of the structure of the ECM. The decellularized membranes are compatible with tissue regeneration, in fact they allow progressive cell growth in the first 7 days of culture (for cell viability the NIH3T3 murine fibroblast cell line was used). The decellularization treatment of the membranes also significantly influences the mechanical properties compared to the native tissue, however a significant increase in the value of Young's modulus was highlighted, which expresses the relationship between tension and deformation in the case of uniaxial loading conditions and in case of behavior of the “elastic” material. This value, expressed in MPa, is almost 3 times higher than that of the native membrane, indicating an increase in stiffness (p<0.00001). For its clinical application, bovine pericardial meshes are dehydrated, as the dry version is a highly requested variant on the market, reducing the amount of moisture between 8 and 18%. Starting from the freeze-drying process, we tried to design an “in house” dehydration process using the machinery present in the company to verify the reliability of the method in relation to the nature of the decellularized bovine pericardium. With the use of a blast chiller to freeze the previously decellularized bovine pericardium and an industrial oven connected to a high-performance vacuum pump, it was possible to obtain a dehydrated product with good consistency, which maintained the desired shape, showing a white appearance, with residual humidity between 11 and 15%, rehydratable and resistant to perforation (<1 daN and <5 daN), all parameters that distinguish an excellent quality medical device. The multi-phase processing of the bovine pericardium is characterized by the fact that it is not possible to interrupt production until the finished product is created, however it constitutes a limiting aspect for the company, as sometimes the need arises to create networks of particular shapes and sizes. To evaluate the preservation over time of the decellularized bovine pericardium, they were frozen at a temperature of -18°C in solution N° 5 – boric acid H3BO3 for 90 days. Boric acid is used in the last step of the chemical treatment during the decellularization process of bovine pericardial membranes. After freezing for 90 days, the production processi s resumed until the finished product is created, through the standard procedure that characterizes the medical device. At the same time, processing was carried out with the standard procedure, without interrupting the cycle, until the finished product was created, so as to be able to compare the results. The tests carried out demonstrate how freezing for 90 days in boric acid at a temperature of -18 °C did not alter the required characteristics and preserved collagen properties. Moreover, the samples were evaluated by analyzing the resistance to perforation (burst test >1daN), the thickness (>0.150 mm) and finally the resistance to perforation normalized to the thickness (>5daN) and compared with the pericardis that continued the production process until the creation of the finished product and subjected to the same tests. This experimental work represents part of a broader research and development activity aimed at identifying possible enhancement strategies for existing market products and/or, evaluating alternative processing procedures beyond current practices, with the goal of optimizing re source utilization and minimizing company expense. This work therefore offers insights into the biological/cellular and mechanical properties of a biomaterial obtained from bovine pericardium. This could be of significance for future developments, both for its use as a mesh, also with a view to wider use, especially in the field of biomedical engineering with the development of scaffolds for tissue regeneration.