Rocco Malaspina

Silk fibroin (SF) derived from Bombyx mori cocoons was employed to fabricate gels using Ajisawa reagent (AJ) as the extraction medium. The resulting regenerated SF solution was subsequently directly dialyzed against an ethanol–water mixture, inducing a gradual and controllable solution–gel transition. Obtained SF gels exhibit a pronounced increase in compressive strength aligned with rising initial fibroin concentration, along with excellent water stability. FESEM, FTIR, and synchrotron X-ray diffraction analyses reveal a homogeneous network structure, likely governed by uniformly distributed physical silk II crosslinks. SF gels containing Ca²⁺ ions predominantly retain the silk I conformation, consistent with optical transparency and higher ionic conductivity. Mechanochromic SF-based gel was further developed through a one-step process involving pentacosadiynoic acid (PCDA) infiltration, followed by UV-induced polymerization into polydiacetylene (PDA), yielding a blue-colored gel. Upon compression, the PDA-infused gel exhibits a clear color transition from blue to red, demonstrating avid mechanochromic behavior. This system represents a promising platform for Structural Health Monitoring (SHM), owing to its intrinsic self-reporting capability and direct visual detectability, enabling the effective sensing of stress-induced damage and crack formation.

Silk proteins are versatile biopolymers well-suited to act as foundational components of a wide range of biomaterials. Rapidly gelling, self-assembling systems are especially valuable for drug delivery and biomedical applications. In this study, we present a way to induce the solid coaggregation of silk fibroin (SF) by adding the anionic surfactant sodium dodecylbenzene sulfonate (SDBS) into an SF solution prepared in formic acid (FA). SF films prepared by dissolving silk in CaCl₂–FA and subsequently rinsing in water to remove CaCl₂ were re-solubilized in FA with different content of SDBS. It was found that SF aggregation time is strongly modulated by the presence of SDBS. At increasing surfactant content, hydrophobic interactions between the SF chains and SDBS promote the formation of spherical coaggregates, whose size increases with surfactant concentration. FTIR analysis reveals that this process is accompanied by the formation of β-sheet structures, likely driven by hydrophobic interactions. This spontaneous liquid-to-solid phase transition promotes the formation of mechanically robust SF films with tunable electrical properties.

Water stable proteins may offer a new field of applications in smart materials for buildings and infrastructures where hydraulic reactions are involved. In this study, cement mortars modified through water-soluble silk fibroin (SF) are proposed. Water-soluble SF obtained by redissolving SF films in phosphate buffer solution (PBS) showed the formation of a gel with β-sheet features of silk II. Electrical measurements on SF indicate that calcium ions are primarily involved in the conductivity mechanism. By exploiting the water solubility properties of silk II and Ca2+ ion transport phenomena and its trapping effect over water molecules, SF provides piezoresistive and piezocapacitive properties to cement mortars, thus enabling self-sensing of mechanical strain which is quite attractive in structural health monitoring applications. SF/cement-based composite introduces the capacitive gauge factor that surpasses the traditional resistive gauge factor reported in the literature by threefold. Cyclic voltammetry measurements demonstrated SF cement mortars possess memcapacitive behavior for positive potentials around +5 V, attributed to an interfacial charge build-up modulated by the SF concentration and the working electrode. Electrical square-biphasic excitation combined with cyclic compressive loads revealed memristive behavior during the unloading stages. These findings along with the availability and the sustainability of SF pave the way for the design of novel multifunctional materials, particularly for applications in masonry and concrete structures.

In this study, we report the preparation and characterization of water-stable films with UV-shielding and good mechanical properties, exploiting the synergistic effect of regenerated silk fibroin and bamboo-derived cellulose. Silk fibroin (SF)/bamboo (B) hybrid films are achieved by solubilizing both silk and bamboo fibers in formic acid with added CaCl₂. Infrared spectroscopy indicates that SF, when combined with bamboo, undergoes a conformational transition, providing evidence of an increase in SF crystallinity. Exploiting the intrinsic absorption of SF in the ultraviolet region, UV–Vis spectroscopy was used to assess the glass transition temperature (T_g) of SF/B films, showing a decrease in T_g by increasing the SF content. The addition of 10 wt% SF to the B matrix improved the elastic modulus by about 10% while conserving the strain at break with respect to the neat B films, increasing the UV shielding properties, while water absorption suggested the material’s hydrophilic and swelling capacity even after one month. The hybrid films showed, under solar irradiation, a photoprotective behavior on keratinocyte human cells by increasing cellular viability. These findings may find potential applications in functional fabrics.