Water-insoluble amorphous silk fibroin scaffolds from aqueous solutions

Silk-Based 3D Porous Scaffolds for Tissue Engineering

Silk fibroin, extracted from the silk of the Bombyx mori silkworm, stands out as a biomaterial due to its nontoxic nature, excellent biocompatibility, and adjustable biodegradability. Porous scaffolds, a type of biomaterial, are crucial for creating an optimal microenvironment that supports cell adhesion and proliferation, thereby playing an essential role in tissue remodeling and repair. Therefore, this review focuses on 3D porous silk fibroin-based scaffolds, first summarizing their preparation methods and then detailing their regenerative effects on bone, cartilage, tendon, vascular, neural, skin, hepatic, and tracheal epithelial tissue engineering in recent years.

Fabrication and investigation of a pentamerous composite based on calix[4]arene functionalized graphene oxide grafted with silk fibroin, cobalt ferrite, and alginate

This paper presents a new scaffold made from graphene oxide nanosheets, calix[4]arene supramolecules, silk fibroin proteins, cobalt ferrite nanoparticles, and alginate hydrogel (GO-CX[4]/SF/CoFe2O4/Alg). After preparing the composite, we conducted various analyses to examine its structure. These analyses included FTIR, XRD, SEM, EDS, VSM, DLS, and zeta potential tests. Additionally, we performed tests to evaluate the swelling ratio, rheological properties, and compressive mechanical strength of the material. The biological capability of the composite was tested through biocompatiblity, anticancer, hemolysis, antibacterial anti-biofilm assays. Besides, the rheological properties and swelling behaviour of the composite were studied. The results showed that the scaffold is biocompatible with Hu02 cells and the cell viability percentages of 85.23 %, 82.78 %, and 80.18 % for were acquired for 24, 48, and 72 h, respectively. In contrast, the cell viability percentage of BT549 cancer cells were obtained 65.79 %, 60.45 % and 58.16 % for same period which confirmed notable anticancer activity of the product composite. Moreover, a significant antibacterial growth inhibition against E. coli and S. aureus species highlights its potential as an effective antibacterial agent. Furthermore, the observed minimal hemolytic effect (6.56 %) and strong inhibition of P. aeruginosa biofilm formation with a low OD value (0.24) indicate notable hemocompatibility and antibacterial activity.

Recent advancement in vascularized tissue-engineered bone based on materials design and modification

Bone is one of the most vascular network-rich tissues in the body and the vascular system is essential for the development, homeostasis, and regeneration of bone. When segmental irreversible damage occurs to the bone, restoring its vascular system by means other than autogenous bone grafts with vascular pedicles is a therapeutic challenge. By pre-generating the vascular network of the scaffold in vivo or in vitro, the pre-vascularization technique enables an abundant blood supply in the scaffold after implantation. However, pre-vascularization techniques are time-consuming, and in vivo pre-vascularization techniques can be damaging to the body. Critical bone deficiencies may be filled quickly with immediate implantation of a supporting bone tissue engineered scaffold. However, bone tissue engineered scaffolds generally lack vascularization, which requires modification of the scaffold to aid in enhancing internal vascularization. In this review, we summarize the relationship between the vascular system and osteogenesis and use it as a basis to further discuss surgical and cytotechnology-based pre-vascularization strategies and to describe the preparation of vascularized bone tissue engineered scaffolds that can be implanted immediately. We anticipate that this study will serve as inspiration for future vascularized bone tissue engineered scaffold construction and will aid in the achievement of clinical vascularized bone.

Three-Dimensional Silk Fibroin/Chitosan Based Microscaffold for Anticancer Drug Screening

Traditional monolayer cell cultures often fail to accurately predict the anticancer activity of drug candidates, as they do not recapitulate the natural microenvironment. Recently, three-dimensional (3D) culture systems have been increasingly applied to cancer research and drug screening. Materials with good biocompatibility are crucial to create a 3D tumor microenvironment involved in such systems. In this study, natural silk fibroin (SF) and chitosan (CS) were selected as the raw materials to fabricate 3D microscaffolds; Besides, sodium tripolyphosphate (TPP), and 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) were used as cross-linking agents. The physicochemical properties of obtained scaffolds were characterized with kinds of testing methods, including emission scanning electron microscopy, x-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, water absorption, and swelling ratio analysis. Cancer cell lines (LoVo and MDA-MB-231) were then seeded on scaffolds for biocompatibility examination and drug sensitivity tests. SEM results showed that EDC cross-linked scaffolds had smaller and more uniform pores with great interconnection than the TPP cross-linked scaffolds, and the EDC cross-linked scaffold exhibited a water absorption ratio around 1000% and a swelling ratio of about 72%. These spatial structures and physical properties could provide more adhesion sites and sufficient nutrients for cell growth. Moreover, both LoVo and MDA-MB-231 cells cultured on the EDC cross-linked scaffold exhibited good adhesion and spreading. CCK8 results showed that increased chemotherapeutic drug sensitivity was observed in 3D culture compared with 2D culture, particularly in the condition of low drug dose (<1 μM). The proposed SF/CS microscaffold can provide a promising in vitro platform for the efficacy prediction and sensitivity screening of anticancer drugs.

Tunable microphase-regulated silk fibroin/poly (lactic acid) biocomposite materials generated from ionic liquids

One of the most effective and promising strategies to develop novel biomaterials with unique, tunable structure and physicochemical properties is by creating composite materials that combine synthetic polymers with natural proteins using ionic liquids. In this study, biodegradable poly(d,l-lactic acid) (PDLLA) was blended with silk fibroin (SF) to create biocompatible films using an ionic liquid-based binary solvent system (1-butyl-3-methylimidazolium chloride/N,N-dimethylformamide), which can maintain the molecular weights of the proteins/polymers and encourage intermolecular interactions between the molecules. The effects of varying the ratio of PLA to SF were studied using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), water contact angle testing, and cytotoxicity analysis as well as enzymatic degradation. Results showed that the composite films were homogeneously blended on the macroscopic scale and exhibited typical fully miscible polymer blend characteristics. By increasing the SF content in the composites, the amounts of β-sheets in the films were significantly increased, allowing for SF to act as a physical crosslinker to maintain the stability of the protein-polymer network. Additionally, SF significantly improved the hydrophilicity and biocompatibility of the material and promoted the self-assembly of micelle structures in the biocomposites. Different topologies in the films also provided beneficial surface morphology for cell adhesion, growth, and proliferation. Overall, this study demonstrated an effective fabrication method for a fine-tuned polymer blends combining synthetic polymer and protein for a wide variety of biomedical and green material applications.

Processing Strategies to Obtain Highly Porous Silk Fibroin Structures with Tailored Microstructure and Molecular Characteristics and Their Applicability in Water Remediation

The present work reports on the control of silk fibroin (SF) porous structures performance through various processing methods. The study includes the analysis of two dissolving techniques (CaCl₂/H₂O/EtOH ternary and LiBr/H₂O binary solutions), three regeneration methods (gelation, lyophilization and gas foaming) and one post-processing (EtOH). In all the cases, followed steps lead to SF structures with porosity values above 94% and large surface areas. Also, results about samples microstructure, secondary organization, crystallinity and water behavior, reveal a direct correlation between processing and SF properties. Thanks to the achieved progress, the SF varying porous structures were evaluated for metalloids (As⁵⁺ and As³⁺) and heavy metals (Cr⁶⁺ and Cr³⁺) adsorption, observing a direct relationship between samples processing and ionic species adsorption ability. Thus, it is shown that the control of the properties of SF based porous structures through processing, represents a suitable and ecofriendly approach for the development of bio-based materials for environmental applications.

Bioinspired Materials for Wound Healing Application: The Potential of Silk Fibroin

Nature is an incredible source of inspiration for scientific research due to the multiple examples of sophisticated structures and architectures which have evolved for billions of years in different environments. Numerous biomaterials have evolved toward high level functions and performances, which can be exploited for designing novel biomedical devices. Naturally derived biopolymers, in particular, offer a wide range of chances to design appropriate substrates for tissue regeneration and wound healing applications. Wound management still represents a challenging field which requires continuous efforts in scientific research for definition of novel approaches to facilitate and promote wound healing and tissue regeneration, particularly where the conventional therapies fail. Moreover, big concerns associated to the risk of wound infections and antibiotic resistance have stimulated the scientific research toward the definition of products with simultaneous regenerative and antimicrobial properties. Among the bioinspired materials for wound healing, this review focuses attention on a protein derived from the silkworm cocoon, namely silk fibroin, which is characterized by incredible biological features and wound healing capability. As demonstrated by the increasing number of publications, today fibroin has received great attention for providing valuable options for fabrication of biomedical devices and products for tissue engineering. In combination with antimicrobial agents, particularly with silver nanoparticles, fibroin also allows the development of products with improved wound healing and antibacterial properties. This review aims at providing the reader with a comprehensive analysis of the most recent findings on silk fibroin, presenting studies and results demonstrating its effective role in wound healing and its great potential for wound healing applications.