Coating of silk sutures by Halloysite/wax Pickering emulsions for controlled delivery of eosin

Pickering emulsions based on wax and halloysite clay nanotubes have been proposed for the coating treatment of silk sutures with the aim to increase their loading capacity towards eosin, which is an antimicrobial molecule. Moreover, the presence of halloysite/wax microspheres onto the surface of silk sutures has been explored for the controlled release of the hydrophobic drug in aqueous medium at pH = 5.2. In addition, we have studied the influence of the coating on the thermal and mechanical properties of the sutures. As concerns the thermal characteristics, we have performed thermogravimetric experiments to investigate the decomposition of the coated silk as well as their water content, while Differential Scanning Calorimetry has been carried out to study the melting process of wax. Dynamic Mechanical Analysis (DMA) has been employed to determine both the tensile and viscoelastic properties of the sutures. In particular, the viscoelastic features have been investigated at variable temperatures (up to 250 °C) to determine the effects of the wax/Hal microparticles on the glass transition of silk fibroin. In conclusion, this paper demonstrates that the wax/halloysite Pickering emulsions can be successfully employed to generate hydrophobic microdomains onto the surface of silk sutures, which present enhanced flexibility and improved loading capacity towards eosin.