Silicones with different crosslinking patterns: Assessment from the perspective of their suitability for biomaterials

Silicones are one of the most important classes of synthetic biomaterials. In order to become stand-alone objects, they must be cross-linked. This can be achieved by chemical (radical, addition or condensation reactions) or physical (supramolecular interactions) processes, each requiring the presence of complementary functional groups and specific deployment conditions (organic, organo-metallic or metallic often non-removable catalyst, temperature, pressure, UV-irradiation, etc.), and leading to materials with particular characteristics in terms of bulk structure and surface. A number of such model networks have been prepared and evaluated from the perspective of their suitability as biomaterials. After the structural characterization by FT-IR spectroscopy aimed mainly at identifying residual functional groups that could affect their behavior, the samples were subjected to specific tests. Thus, the hydrolytic and enzymatic stability were studied in aqueous environments with different pH values. The surface analysis was done by atomic force microscopy (AFM), which allowed the highlighting of the topography and the estimation of the average roughness. The water, formamide, methylene iodide, and buffer solutions` contact angles, as well as blood interfacial tension were also determined. The biocidal activity against a series of fungi and bacteria was studied. The bio-and mucoadhesion of the films were evaluated by an appropriate technique, and the cell adhesion test was performed on Normal Human Dermal Fibroblasts (NHDF). The results indicate that, regardless of the crosslinking pattern, the films are hydrophobic, hydrolytically stable and biocompatible but bio-/mucoadhesivity are low, which recommends them as sutures and the series cross -linked by addition would be suitable for extrusion processes with "click " crosslinking.