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Following the deployment of a coronary stent and disruption of an atheromatous plaque, the deformation of the arterial wall and the presence of the stent struts create a new fluid dynamic field, which can cause an abnormal biological response. In this study 3D computational models were used to analyze the fluid dynamic disturbances induced by the placement of a stent inside a coronary artery. Stents models were first expanded against a simplified arterial plaque, with a solid mechanics analysis, and then subjected to a fluid flow simulation under pulsatile physiological conditions. Spatial and temporal distribution of arterial wall shear stress (WSS) was investigated after the expansion of stents of different designs and different strut thicknesses. Common oscillatory WSS behavior was detected in all stent models. Comparing stent and vessel wall surfaces, maximum WSS values (in the order of 1Pa) were located on the stent surface area. WSS spatial distribution on the vascular wall surface showed decreasing values from the center of the vessel wall portion delimited by the stent struts to the wall regions close to the struts. The hemodynamic effects induced by two different thickness values for the same stent design were investigated, too, and a reduced extension of low WSS region (<0.5Pa) was observed for the model with a thicker strut.

The main aim of this work is the synthesis and characterization of cross-linked chitosan systems. Chitosan hydrogels can be prepared by physical or chemical cross-linking of polymer chains. Chemical cross-linking, leading to the creation of hydrogel networks possessing improved mechanical properties and chemical stability, can be achieved using either synthetic agents or naturalbased agents. In this work, the cross-linker Genipin, a naturally derived compound, was selected because of the lower acute toxicity compared to many other commonly used synthetic cross-linking reagents. In particular, the chemical stabilization of chitosan through genipin cross-linking molecules was performed and characterized by calorimetric analyses (differential scanning calorimetry), swelling measurements in different pHs, and ionic strength. The reaction kinetics was carried out by means of rheological measurements, and both the activation energy (E a ) and the reaction order (m) were calculated. The hydrogel analyses were carried out at different concentrations of genipin (GN1 and GN2). The results were used to evaluate the possibility to use the chemical cross-linked chitosangenipin hydrogel for biomedical applications.

The current "gold standard" to treat bone lesions is allografts and autografts, both presenting important disadvantages such as risk of infection and morbidity. Synthetic grafts and scaffolds for bone regeneration represent a promising solution. Fused deposition modeling is a valid tool for developing synthetic bone grafts of complex shapes, which is a key issue. The possibility of building polylactic acid-nanohydroxyapatite (PLA/nanoHA) composites by 3D printing was systematically evaluated. PLA/nanoHA filaments for low-cost 3D printers were produced by a multistep solvent-free procedure and characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry, and rheometry. TGA analysis confirmed the presence of the nanoHA amounts used in the composites, equal to 5 and 15 wt %. The glasstransition temperature and degree of crystallinity of PLA are not influenced by presence of nanoHA, which remains substantially amorphous. The morphological analysis and compression testing on printed samples showed that nanoHA was uniformly dispersed within the PLA matrix and improved the PLA mechanical properties without changing the rheological performance. V C 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44656.