Injectable Bombyx mori (B. mori) silk fibroin/MXene conductive hydrogel for electrically stimulating neural stem cells into neurons for treating brain damage

Brain damage is a common tissue damage caused by trauma or diseases, which can be life-threatening. Stem cell implantation is an emerging strategy treating brain damage. The stem cell is commonly embedded in a matrix material for implantation, which protects stem cell and induces cell differentiation. Cell differentiation induction by this material is decisive in the effectiveness of this treatment strategy. In this work, we present an injectable fibroin/MXene conductive hydrogel as stem cell carrier, which further enables in-vivo electrical stimulation upon stem cells implanted into damaged brain tissue. Cell differentiation characterization of stem cell showed high effectiveness of electrical stimulation in this system, which is comparable to pure conductive membrane. Axon growth density of the newly differentiated neurons increased by 290% and axon length by 320%. In addition, unfavored astrocyte differentiation is minimized. The therapeutic effect of this system is proved through traumatic brain injury model on rats. Combined with in vivo electrical stimulation, cavities formation is reduced after traumatic brain injury, and rat motor function recovery is significantly promoted.

Ultrafast Bi-Directional Bending Moisture-Responsive Soft Actuators through Superfine Silk Rod Modified Bio-Mimicking Hierarchical Layered Structure

Development of stimulus-responsive materials is crucial for novel soft actuators. Among these actuators, the moisture-responsive actuators are known for their accessibility, eco-friendliness, and robust regenerative attributes. A major challenge of moisture-responsive soft actuators (MRSAs) is achieving significant bending curvature within short response times. Many plants naturally perform large deformation through a layered hierarchical structure in response to moisture stimuli. Drawing inspiration from the bionic structure of Delosperma nakurense (D. nakurense) seed capsule, here the fabrication of an ultrafast bi-directional bending MRSAs is reported. Combining a superfine silk fibroin rod (SFR) modified graphene oxide (GO) moisture-responsive layer with a moisture-inert layer of reduced graphene oxide (RGO), this actuator demonstrated large bi-directional bending deformation (-4.06 ± 0.09 to 10.44 ± 0.00 cm-1 ) and ultrafast bending rates (7.06 cm-1  s-1 ). The high deformation rate is achieved by incorporating the SFR into the moisture-responsive layers, facilitating rapid water transmission within the interlayer structure. The complex yet predictable deformations of this actuator are demonstrated that can be utilized in smart switch, robotic arms, and walking device. The proposed SFR modification method is simple and versatile, enhancing the functionality of hierarchical layered actuators. It holds the potential to advance intelligent soft robots for application in confined environments.

Metal-Organic Frameworks Nucleated by Silk Fibroin and Modified with Tumor-Targeting Peptides for Targeted Multimodal Cancer Therapy

Multimodal therapy requires effective drug carriers that can deliver multiple drugs to specific locations in a controlled manner. Here, the study presents a novel nanoplatform constructed using zeolitic imidazolate framework-8 (ZIF-8), a nanoscale metal-organic framework nucleated under the mediation of silk fibroin (SF). The nanoplatform is modified with the newly discovered MCF-7 breast tumor-targeting peptide, AREYGTRFSLIGGYR (AR peptide). Indocyanine green (ICG) and doxorubicin (DOX) are loaded onto the nanoplatform with high drug encapsulation efficiency (>95%). ICG enables the resultant nanoparticles (NPs), called AR-ZS/ID-P, to release reactive oxygen species for photodynamic therapy (PDT) and heat for photothermal therapy (PTT) under near-infrared (NIR) irradiation, promoting NIR fluorescence and thermal imaging to guide DOX-induced chemotherapy. Additionally, the controlled release of both ICG and DOX at acidic tumor conditions due to the dissolution of ZIF-8 provides a drug-targeting mechanism in addition to the AR peptide. When intravenously injected, AR-ZS/ID-P NPs specifically target breast tumors and exhibit higher anticancer efficacy than other groups through ICG-enabled PDT and PTT and DOX-derived chemotherapy, without inducing side effects. The results demonstrate that AR-ZS/ID-P NPs are a promising multimodal theranostic nanoplatform with maximal therapeutic efficacy and minimal side effects for targeted and controllable drug delivery.