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Spider silks are remarkable materials characterized by superb mechanical properties such as strength, extensibility, and lightweightedness. Yet, to date, limited models are available to fully explore sequence‐property relationships for analysis and design. Here a custom generative large‐language model is proposed to enable the design of novel spider silk protein sequences to meet complex combinations of target mechanical properties. The model, pretrained on a large set of protein sequences, is fine‐tuned on ≈1,000 major ampullate spidroin (MaSp) sequences for which associated fiber‐level mechanical properties exist, to yield an end‐to‐end forward and inverse generative approach that is aplied in a multi‐agent strategy. Performance is assessed through: 1) a novelty analysis and protein type classification for generated spidroin sequences through Basic Local Alignment Search Tool (BLAST) searches, 2) property evaluation and comparison with similar sequences, 3) comparison of resulting molecular structures, and 4) a detailed sequence motif analyses. This work generates silk sequences with property combinations that do not exist in nature and develops a deeper understanding of the mechanistic roles of sequence patterns in achieving overarching key mechanical properties (elastic modulus (E), strength, toughness, failure strain). The model provides an efficient approach to expand the silkome dataset, facilitating further sequence‐structure analyses of silks, and establishes a foundation for synthetic silk design and optimization. [ABSTRACT FROM AUTHOR]

Porous grafts facilitate constructive remodeling of blood vessels. Incorporating multiple biomimetic cues to porous grafts can promote vascular regeneration. However, the fabrication of such medical devices remains challenging. Here, beta‐sheet rich silk nanofibers (BSN) are added to poly(vinyl alcohol) (PVA) solution and aggregated under a cylindric electric field to form circumferentially and axially oriented tubular structures, to simulate the endothelial and media layers of blood vessels. PVA in the aligned tubes is then crystallized through repeat freezing–thawing process to offer mechanical performances. Through tuning the ratio of BSN and PVA, the composite tubes with dual anisotropic microstructures exhibit better mechanical properties than pure PVA vascular grafts. Significantly improved cell adhesion, spreading, proliferation, and alignment are achieved. Both endothelial and smooth muscle cells show improved biological activity on the grafts due to the regulatory roles of the aligned structures. In vivo studies reveal the formation of endothelial layers within four weeks of implantation, ensuring long‐term patency. The endothelial and smooth muscle double layers are regenerated after eight months postimplantation, forming hierarchical microstructures and compositions similar to native vessels. The porous composite grafts with multiple aligned structures guide vascular remodeling to regenerate blood vessels, demonstrating potential for clinical translation. [ABSTRACT FROM AUTHOR]

Abstract: Biomineralization at the organic–inorganic interface is critical to many biology material functions in vitro and in vivo. Recombinant silk–silica fusion peptides are organic–inorganic hybrid material systems that can be effectively used to study and control biologically mediated mineralization due to the genetic basis of sequence control. However, to date, the mechanisms by which these functionalized silk–silica proteins trigger the differentiation of human mesenchymal stem cells (hMSCs) to osteoblasts remain unknown. To address this challenge, silk–silica surfaces are analyzed for silica–hMSC receptor binding and activation, and the intracellular pathways involved in the induction of osteogenesis on these bioengineered biomaterials. The induction of gene expression of αVβ3 integrin, all three mitogen‐activated protein kinsases, as well as c‐Jun, runt‐related transcription factor 2, and osteoblast marker genes is demonstrated upon growth of the hMSCs on the silk–silica materials. This induction of key markers of osteogenesis correlates with the content of silica on the materials. Moreover, computational simulations are performed for silk/silica‐integrin binding which show activation of αVβ3 integrin in contact with silica. This integrated computational and experimental approach provides insight into interactions that regulate osteogenesis toward more efficient biomaterial designs. [ABSTRACT FROM AUTHOR]

The production of structural and functional materials with enhanced mechanical properties through the integration of soft and hard components is a common approach to Nature's material design. However, directly mimicking these optimized design routes in the lab for practical applications remains challenging. For example, graphene and silk are two materials with complementary mechanical properties that feature ultrahigh stiffness and toughness, respectively. Yet, no simple and controllable approach is developed to homogeneously integrate these two components into functional composites, mainly due to the hydrophobicity and chemical inertness of graphene. In this study, well-dispersed and highly stable graphene/silk fibroin (SF) suspension systems are developed, which are suitable for processing to fabricate polymorphic materials, such as films, fibers, and coatings. The obtained graphene/SF nanocomposites maintain the electronic advantages of graphene, and they also allow tailorable mechanical performance to form including ultrahigh stretchable (with a strain to failure to 611 ± 85%), or high strength (339 MPa) and high stiffness (7.4 GPa) material systems. More remarkably, the electrical resistances of these graphene/SF materials are sensitive to material deformation, body movement, as well as humidity and chemical environmental changes. These unique features promise their utility as wearable sensors, smart textiles, intelligent skins, and human-machine interfaces. [ABSTRACT FROM AUTHOR]

Functional vascularization is critical for the clinical regeneration of complex tissues such as kidney, liver, or bone. The immobilization or delivery of growth factors has been explored to improve vascularization capacity of tissue-engineered constructs; however, the use of growth factors has inherent problems such as the loss of signaling capability and the risk of complications including immunological responses and cancer. Here, a new method of preparing water-insoluble silk protein scaffolds with vascularization capacity using an all-aqueous process is reported. Acid is added temporally to tune the self-assembly of silk in the lyophilization process, resulting in water-insoluble scaffold formation directly. These biomaterials are mainly noncrystalline, offering improved cell proliferation than previously reported silk materials. These systems also have an appropriate softer mechanical property that could provide physical cues to promote cell differentiation into endothelial cells, and enhance neovascularization and tissue ingrowth in vivo without the addition of growth factors. Therefore, silk-based degradable scaffolds represent an exciting biomaterial option, with vascularization capacity for soft tissue engineering and regenerative medicine. [ABSTRACT FROM AUTHOR]

Recent use of biopolymers as interface materials between planar, inorganic electronics and biological tissues has required the adaptation of micro- and nanofabrication techniques for use with these nontraditional materials. In this work, a method which builds on this principle for spatial control of adhesion in multilayer silk fibroin laminates is investigated. This is accomplished through the addition of a spatially patterned amorphous silk adhesive layer in between the films to be adhered, before thermally processing them with heat (120 °C) and pressure (80 Psi) according to established procedures. A one-step method for rapid, high-throughput fabrication is demonstrated, which establishes a strong (1100 kPa) bond between the layers independent of the initial processing conditions of the films. The adhesive layers can be patterned using existing silk fabrication techniques, allowing for the assembly of complex geometries including bilayers and microbubbles. Additionally, the utility of this method is demonstrated for potential applications in drug delivery and transient electronics. This approach provides a versatile method for construction of complex multilayer structures in silk, which with future work may ultimately improve the utility of this material as a bridge between high technology and the biomedical sciences. [ABSTRACT FROM AUTHOR]

There is great need for soft biomaterials that match the stiffness of human tissues for tissue engineering and regeneration. Hydrogels are frequently employed for extracellular matrix functionalization and to provide appropriate mechanical cues. It is challenging, however, to achieve structural integrity and retain bioactive molecules in hydrogels for complex tissue formation that may take months to develop. This work aims to investigate mechanical and biochemical characteristics of silk hydrogels for soft tissue engineering, specifically for the nervous system. The stiffness of 1 to 8% silk hydrogels, measured by atomic force microscopy, is 4 to 33 kPa. The structural integrity of silk gels is maintained throughout embryonic chick dorsal root ganglion (cDRG) explant culture over 4 days whereas fibrin and collagen gels decrease in mass over time. Neurite extension of cDRGs cultured on 2 and 4% silk hydrogels exhibit greater growth than softer or stiffer gels. Silk hydrogels release <5% of neurotrophin-3 (NT-3) over 2 weeks and 11-day old gels show maintenance of growth factor bioactivity. Finally, fibronectin- and NT-3-functionalized silk gels elicit increased axonal bundling suggesting their use in bridging nerve injuries. These results support silk hydrogels as soft and sustainable biomaterials for neural tissue engineering. [ABSTRACT FROM AUTHOR]

In the field of regenerative medicine there is a need for scaffolds that support large, critically-sized tissue formation. Major limitations in reaching this goal are the delivery of oxygen and nutrients throughout the bulk of the engineered tissue as well as host tissue integration and vascularization upon implantation. To address these limitations, the development of a porous scaffold platform made from biodegradable silk protein that contains an array of vascular-like structures that extend through the bulk of the scaffold was previously reported. Here, the hollow channels play a pivotal role in enhancing cell infiltration, delivering oxygen and nutrients to the scaffold bulk, and promoting in vivo host tissue integration and vascularization. The unique features of this protein biomaterial system, including the vascular structures and tunable material properties, render this scaffold a robust and versatile tool for implementation in a variety of tissue engineering, regenerative medicine, and disease modeling applications. [ABSTRACT FROM AUTHOR]

Neural engineering provides promise for cell therapy by integrating the host brain with brain-machine-interface technologies in order to externally modulate functions. Long-term interfaces with the host brain remain a critical challenge due to insufficient graft cell survivability and loss of brain electrode sensitivity over time. Here, integrated neuron-electrode interfaces are developed on thin flexible and transparent silk films as brain implants. Mechanical properties and surface topography of silk films are optimized to promote cell survival and alignment of primary rat cortical cells. Compartmentalized neural cultures and co-patterned electrode arrays are incorporated on the silk films with built-in wire connections. Electrical stimulation via electrodes embedded in the films activated surrounding neurons to produce evoked calcium responses. In mice brains, silk film implants show conformal contact capable of modulating host brain cells with minimal inflammatory response and stable indwelling for weeks. The approach of combining cell therapy and brain electrodes could provide sustained functional interfaces with ex vivo control with spatial precision. [ABSTRACT FROM AUTHOR]