GRAFTED SILK AND WOOL FABRICS WITH ENHANCED BIOACTIVITY

Silk fibres have been used for centuries as suture materials. They have been considered functional biomaterials in the last decades, mainly as scaffolds for tissue engineering[1]. In this framework, silk fabrics from two different origin silkworms (one from Bombyx mori of Bombycidae and another from Antheraea yamamai (Tussah) of Saturniidae) were grafted with two monomers having phosphoric groups, i.e. phosmer M (2-phosphonooxyethyl 2-methylprop-2-enoate) and phosmer CL ((3-chloro-2-phosphonooxypropyl) 2-methylprop-2-enoate) at different concentrations. Our study aimed to evaluate the bioactivity of the fabrics, i.e. the ability to enucleate a calcium phosphate phase after immersion in Simulated Body Fluid solution (SBF). The same grafting was also applied to wool fabrics. Both phosmers were successfully studied as flame retarding agents[2] for silk fabrics, and their chemical composition suggested a possible application in the biomedical field. IR and Raman spectroscopy were applied to study the degree of grafting and its influence on the structure and conformation of silk fibroins and wool keratins. The same techniques were used to characterize the fabrics after seven days of incubation in SBF at 37 °C to study possible structural variations and the enucleation of a calcium phosphate phase: interestingly, all samples showed to be bioactive. The most bioactive samples contained the highest phosmers amounts, and, generally, the samples grafted with phosmer M appeared more bioactive. The IR technique, which is more sensitive to surface modifications, allowed a semiquantitative evaluation of calcium phosphate deposition but showed a certain inhomogeneity of the inorganic phase. Although all samples enucleated a calcium phosphate phase, only some of them exhibited a mass increase (Bombyx mori: 0.4-8.5%; Tussah: 0.8-4%, wool: 0.4-3,5%), maybe because of the release of weakly bounded phosmers into the medium: therefore the mass of the newly formed calcium phosphate phase could be underestimated. Raman spectroscopy further confirmed these findings and evidenced that the inorganic deposit did not affect the structure of silk fibroins and wool keratins. Long-lasting bioactivity testing in vitro is still in progress, together with cell adhesion and proliferation essays that would eventually confirm the improvement of silk and wool surfaces for future biomedical applications.