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.

Silk Protein-Mediated Biomineralization: From Bioinspired Strategies and Advanced Functions to Biomedical Applications.

Biomineralization refers to the process through which minerals nucleate in a structured manner to form specific crystal structures by the regulating of biomacromolecules. Biomineralization occurs in bones and teeth within the human body, where collagen acts as a template for the nucleation of hydroxyapatite (HA) crystals. Similar to collagen, silk proteins spun by silkworms can also serve as templates for the nucleation and growth of inorganic substances at interfaces. By enabling the binding of silk proteins to inorganic minerals, the process of biomineralization enhances the properties of silk-based materials and broadens their potential applications, rendering them highly promising for use in biomedical applications. In recent years, the development of biomineralized materials using silk proteins has garnered considerable attention in the biomedical field. This comprehensive review outlines the mechanism of biomineral formation mediated by silk proteins, as well as various biomineralization methods used to prepare silk-based biomineralized materials (SBBMs). Additionally, we discuss the physicochemical properties and biological functions of SBBMs, and their potential applications in various fields such as bioimaging, cancer therapy, antibacterial treatments, tissue engineering, and drug delivery. In conclusion, this review highlights the significant role that SBBMs can play in the biomedical field.

Graphene Oxide-Coated Patterned Silk Fibroin Films Promote Cell Adhesion and Induce Cardiomyogenic Differentiation of Human Mesenchymal Stem Cells.

Cardiac tissue engineering is a promising strategy for the treatment of myocardial damage. Mesenchymal stem cells (MSCs) are extensively used in tissue engineering. However, transformation of MSCs into cardiac myocytes is still a challenge. Furthermore, weak adhesion of MSCs to substrates often results in poor cell viability. Here, we designed a composite matrix based on silk fibroin (SF) and graphene oxide (GO) for improving the cell adhesion and directing the differentiation of MSCs into cardiac myocytes. Specifically, patterned SF films were first produced by soft lithographic. After being treated by air plasma, GO nanosheets could be successfully coated on the patterned SF films to construct the desired matrix (P-GSF). The resultant P-GSF films presented a nano-topographic surface characterized by linear grooves interlaced with GO ridges. The P-GSF films exhibited high protein absorption and suitable mechanical strength. Furthermore, the P-GSF films accelerated the early cell adhesion and directed the growth orientation of MSCs. RT-PCR results and immunofluorescence imaging demonstrated that the P-GSF films significantly improved the cardiomyogenic differentiation of MSCs. This work indicates that patterned SF films coated with GO are promising matrix in the field of myocardial repair tissue engineering.

Efficient Tumor Immunotherapy through a Single Injection of Injectable Antigen/Adjuvant-Loaded Macroporous Silk Fibroin Microspheres.

Synthetic or natural materials have been used as vaccines in cancer immunotherapy. However, using them as vaccines necessitates multiple injections or surgical implantations. To tackle such daunting challenges, we develop an injectable macroporous Bombyx mori (B. mori) silk fibroin (SF) microsphere loaded with antigens and immune adjuvants to suppress established tumors with only a single injection. SF microspheres can serve as a scaffold by injection and avoid surgical injury as seen in traditional scaffold vaccines. The macroporous structure of the vaccine facilitates the recruitment of immune cells and promotes the activation of dendritic cells (DCs), resulting in a favorable immune microenvironment that further induces strong humoral and cellular immunity. We have also modified the vaccine into a booster version by simply allowing the antigens to be adsorbed onto the SF microspheres. The booster vaccine highly efficiently suppresses tumor growth by improving the cytotoxic T lymphocyte (CTL) response. In general, these results demonstrate that the macroporous SF microspheres can serve as a facile platform for tumor vaccine therapy in the future. Since the SF microspheres are also potential scaffolds for tissue regeneration, their use as a vaccine platform will enable their applications in eradicating tumors while regenerating healthy tissue to heal the tumor-site cavity.

Arginine induces protein self-assembly into nanofibers for triggering osteogenic differentiation of stem cells.

Although silk proteins are considered promising in building a scaffold for tissue engineering, one of the silk proteins, Bombyx mori silk sericin (BS), has limited processability in producing nanofibrous scaffolds because its surface charge anisotropy promotes gelation instead. To overcome this daunting challenge, we developed a mild and simple procedure for assembling BS into nanofibers and nanofibrous scaffolds. Briefly, arginine was added to the aqueous BS solution to reduce the negative charge of BS, thereby inducing BS to self-assemble into nanofibers in the solution. Circular dichroism (CD) and Fourier transform infrared (FT-IR) spectra showed that arginine promoted the formation of ß-sheet conformation in BS and increased its thermal stability. Furthermore, the arginine-induced BS nanofiber solution could be casted into scaffolds made of abundant network-like nanofibrous structures. The BS scaffolds promoted cell adhesion and growth and stimulated osteogenic differentiation of the bone marrow mesenchymal stem cells (BMSCs) in the absence of differentiation inducers in culture media. Our study presents a new strategy for assembling proteins into osteogenic nanofibrous scaffolds for inducing stem cell differentiation in regenerative medicine.

Self-stabilized silk sericin-based nanoparticles: In vivo biocompatibility and reduced doxorubicin-induced toxicity.

A variety of colloid stabilizers and cryoprotectants confer improved nanoparticle (NP) colloidal stability and redisperability. However, discounted tumor targetability, delivery efficacy and possible side effects limit the application in vascular delivery of NPs. Here we present water-soluble silk sericin (SS) not only as a material for the preparation of NPs, but also both a dispersion stabilizer and a cryoprotectant. In the absence of any stabilizers, SS-based NPs (SSC@NPs) can resist the adsorption of serum proteins, preventing the formation of particle agglomerates. Following freeze-drying without addition of cryoprotectants, SSC@NPs powder can be easily resuspended into NP dispersion with a nearly monodispersed distribution. Additionally, SSC@NPs do not result in acute toxicity in mice at a dose of 400 mg/kg with a slow injection. Moreover, doxorubicin (DOX)-loaded SSC@NPs (DOX-SSC@NPs) diminish the biodistribution of DOX in the heart, mitigating DOX-induced cardiotoxicity of mice without compromising therapeutic efficacy. Our results suggest that the self-stabilized SSC@NPs could be a secure and effective drug carrier for intravenous administration when deprived of protective agents. STATEMENT OF SIGNIFICANCE: During manufacturing process such as freeze-drying, or interaction with complex fluids like blood, NPs for systemic drug delivery need to be highly dispersible and structurally intact. In this work, we have demonstrated the self-stability of SSC@NPs subjected to biological media and freeze-drying. This study represents the first work showing water-soluble SS could both act as a dispersion stabilizer and a cryoprotectant due to its hydrophilicity. Plus, good in vivo biocompatibility of SSC@NPs has been confirmed. Therefore, it may be promising that water-soluble SS can be generally used as a safe biomaterial against serum adsorption.