Silk fibroin fibers from two different sources, i.e., Bombyx mori pure breed silkworms and polyhybrid crossbred silkworm cocoons, were treated with formic acid under planar stirring conditions to prepare non-woven nets. The treatment partially dissolved the fibers, which bound together and formed a non-woven micrometric net with fibers coated by a thin layer of low molecular weight fibroin matrix. The starting fibers, net materials and fibroin coating layer, were characterized in terms of amino acid composition, molecular weight and calorimetric properties. In vitro cell culture tests with rat fibroblasts were performed to investigate cell proliferation, morphology and spreading. Moreover, host-rat fibroblasts were pre-seeded on the aforementioned nets and implanted in the thorax of rats for histological analysis. In spite of the chemical differences between the two starting fibroins, the response of the said materials in vitro and in vivo were very similar. These results suggest that the outcome is likely correlated to the modification of the processing technique, that during the formation of the net a thin gel layer of similar amino acid composition was formed on the fibroin fibers.