RESUMEN
3D printing of water stable proteins with elastic properties offers a broad range of applications including self-powered biomedical devices driven by piezoelectric biomaterials. Here, we present a study on water-soluble silk fibroin (SF) films. These films were prepared by mixing degummed silk fibers and calcium chloride (CaCl2) in formic acid, resulting in a silk I-like conformation, which was then converted into silk II by redissolving in phosphate buffer (PBS). Circular dichroism, Raman and infrared (IR) spectroscopies were used to investigate the transitions of secondary structure in silk I and silk II as the pH of the solvent and the sonication time were changed. We showed that a solvent with low pH (e.g. 4) maintains the silk I ß-turn structure; in contrast solvent with higher pH (e.g. 7.4) promotes ß-sheet features of silk II. Ultrasonic treatment facilitates the transition to water stable silk II only for the SF redissolved in PBS. SF from pH 7.4 solution has been printed using extrusion-based 3D printing. A self-powered memristor was realized, comprising an SF-based electric generator and an SF 3D-printed memristive unit connected in series. By exploiting the piezoelectric properties of silk II with higher ß-sheet content and Ca2+ ion transport phenomena, the application of an input voltage driven by a SF generator to SF 3D printed holey structures induces a variation from an initial low resistance state (LRS) to a high resistance state (HRS) that recovers in a few minutes, mimicking the transient memory, also known as short-term memory. Thanks to this holistic approach, these findings can contribute to the development of self-powered neuromorphic networks based on biomaterials with memory capabilities.
RESUMEN
Despite the technological importance of semiconductor black phosphorus (BP) in materials science, maintaining the stability of BP crystals in organic media and protecting them from environmental oxidation remains challenging. In this study, we present the synthesis of bulk BP and the exploitation of the viscoelastic properties of a regenerated silk fibroin (SF) film as a biocompatible substrate to transfer BP flakes, thereby preventing oxidation. A model based on the flow of polymers revealed that the applied flow-induced stresses exceed the yield stress of the BP aggregate. Raman spectroscopy was used to investigate the exfoliation efficiency as well as the environmental stability of BP transferred on the SF substrate. Notably, BP flakes transferred to the SF substrate demonstrated improved stability when SF was dissolved in a phosphate-buffered saline medium, and in vitro cancer cell viability experiments demonstrate the tumor ablation efficiency under visible to near-infrared (Vis-nIR) radiation. Moreover, the SF and BP-enriched SF (SF/BP) solution was shown to be processable via extrusion-based three-dimensional (3D) printing. Therefore, this work paves the way for a general method for the transferring of BP on natural biodegradable polymers and processing them via 3D printing toward novel functionalities and complex shapes for biomedical purposes.
RESUMEN
[This corrects the article DOI: 10.1021/acsomega.3c04563.].
RESUMEN
Trachea defects that required surgical interventions are increasing in number in the recent years, especially for pediatric patients. However, current gold standards, such as biological grafts and synthetic prothesis, do not represent an effective solution, due to the lack of mimicry and regeneration capability. Bioprinting is a cutting-edge approach for the fabrication of biomimetic scaffold to empower tissue engineering toward trachea replacement. In this study, we developed a self-folding gelatin-based bilayer scaffold for trachea engineering, exploiting the 4D bioprinting approach, namely the fabrication of dynamic scaffolds, able to shape morph in a predefined way after the application of an environmental stimulus. Indeed, starting form a 2D flat position, upon hydration, this scaffold forms a closed tubular structure. An analytical model, based on Timoshenko's beam thermostats, was developed, and validated to predict the radius of curvature of the scaffold according to the material properties and the scaffold geometry. The 4D bioprinted structure was tested with airway fibroblast, lung endothelial cells and ear chondral progenitor cells (eCPCs) toward the development of a tissue engineered trachea. Cells were seeded on the scaffold in its initial flat position, maintained their position after the scaffold actuation and proliferated over or inside it. The ability of eCPCs to differentiate towards mature cartialge was evaluated. Interestingly, real-time PCR revealed that differentiating eCPCs on the 4D bioprinted scaffold promote healthy cartilage formation, if compared with eCPCs cultured on 2D static scaffold. Thus, eCPCs can perceive scaffold folding and its final curvature and to react to it, towards the formation of mature cartilage for the airway.