Fibroin Membrane Research Articles

Comparative Analysis of Silk Fibroin Membranes across Cross-Linking Methods: Processing and Characterization.

Silk fibroin (SF) extracted from silkworm silk can be transformed into transparent membranes with well-suited physical properties for ophthalmic applications. There is ample literature on the fabrication and characterization of SF-based membranes; however, the use of diverse SF extraction protocols and characterization methods or their settings makes it difficult to compare different silk membrane properties across studies. In this work, we fabricated 10 families of SF-based membranes by physical cross-linking and one non-cross-linked as a control. We evaluated transparency (ranging from 84.5 to 95.3% in the visible spectrum), enzyme stability (from 24 h to 200 days in protease XIV), decomposition temperature (280-290 °C), water uptake (40-60%), Young's modulus (8-30 MPa), roughness (1.6-22.7 nm), and FTIR spectra for the secondary structure. We found correlation between water uptake and the Young's modulus (the lower the water uptake, the higher the Young's modulus) and a relationship between membrane stability in protease XIV and the secondary structure of the proteins. Higher surface roughness and faster degradation were found in membranes cross-linked with polyethylene glycol, and conversely, lower roughness and lower degradation were found in methanol, ethanol, or isopropanol crossed-link membranes. This ample compilation of materials and their characterization will aid in the selection of a SF-based material according to the needs of the application.

Biodegradable Silk Fibroin Matrices for Wound Closure in a Human 3D Ex Vivo Approach.

In this study, the potential of silk fibroin biomaterials for enhancing wound healing is explored, focusing on their integration into a human 3D ex vivo wound model derived from abdominoplasties. For this purpose, cast silk fibroin membranes and electrospun nonwoven matrices from Bombyx mori silk cocoons were compared to untreated controls over 20 days. Keratinocyte behavior and wound healing were analyzed qualitatively and quantitatively by histomorphometric and immune histochemical methods (HE, Ki67, TUNEL). Findings reveal rapid keratinocyte proliferation on both silk fibroin membrane and nonwoven matrices, along with enhanced infiltration in the matrix, suggesting improved early wound closure. Silk fibroin membranes exhibited a significantly improved early regeneration, followed by nonwoven matrices (p < 0.05) compared to untreated wounds, resulting in the formation of multi-layered epidermal structures with complete regeneration. Overall, the materials demonstrated excellent biocompatibility, supporting cell activity with no signs of increased apoptosis or early degradation. These results underscore silk fibroin's potential in clinical wound care, particularly in tissue integration and re-epithelialization, offering valuable insights for advanced and-as a result of the electrospinning technique-individual wound care development. Furthermore, the use of an ex vivo wound model appears to be a viable option for pre-clinical testing.

Self-composite silk fibroin membranes for guided bone regeneration: 1 material 3 architectures with intrinsic integrity

Silk fibroin (SF) takes attention in tissue engineering due to unique features, e.g., excellent biocompatibility/biodegradability with superior mechanical/thermal properties despite its lightweight. Guided bone regeneration (GBR) seeks bilayered GBR membranes to govern bone regeneration, although constituent parts of such membranes may undergo delamination once different biomaterials are combined. Herein, 3-component bilayered SF membranes were prepared for the first time utilizing the same polymer in different forms by eliminating the delamination risk of layers for GBR applications. One side consisted of a non-porous SF film serving as a barrier against penetration of non-osteogenic tissue whereas the other side was porous/fibrous composed of SF sponge and SF fibers for bone regeneration. Proper integration between these layers was confirmed via scanning electron microscopy (SEM). Composites reinforced with high fiber percent (30%) had remarkably enhanced compressive strength and elastic moduli, which were further improved by increasing polymer concentration from 4% to 8%. Non-porous morphology of the barrier side was preserved during 28 days of degradation while pore sizes enlarged on the other surface, which would be beneficial for cell migration into the regenerative side. Saos-2 cells seeded on composites with high fiber percent proliferated more within 14 days; however, alkaline phosphatase (ALP) activity on low-fiber-percent counterparts was elevated more. Osteogenic marker gene expressions were significantly higher than control on day 14. All self-composites were eminent candidates to promote bone regeneration with tailor-made capacity for further improvements. Taken together, 1-material 3-architecture SF fabricated by a green and practical technique holds promise for GBR applications.

Harmonizing Thickness and Permeability in Bone Tissue Engineering: A Novel Silk Fibroin Membrane Inspired by Spider Silk Dynamics (Adv. Mater. 13/2024)

Harmonizing Thickness and Permeability in Bone Tissue Engineering: A Novel Silk Fibroin Membrane Inspired by Spider Silk Dynamics (Adv. Mater. 13/2024)

Doping of casted silk fibroin membranes with extracellular vesicles for regenerative therapy: a proof of concept

Bioactive material concepts for targeted therapy have been an important research focus in regenerative medicine for years. The aim of this study was to investigate a proof-of-concept composite structure in the form of a membrane made of natural silk fibroin (SF) and extracellular vesicles (EVs) from gingival fibroblasts. EVs have multiple abilities to act on their target cell and can thus play crucial roles in both physiology and regeneration. This study used pH neutral, degradable SF-based membranes, which have excellent cell- and tissue-specific properties, as the carrier material. The characterization of the vesicles showed a size range between 120 and 180 nm and a high expression of the usual EV markers (e.g. CD9, CD63 and CD81), measured by nanoparticle tracking analysis (NTA) and single-EV flow analysis (IFCM). An initial integration of the EVs into the membrane was analyzed using scanning and transmission electron microscopy (SEM and TEM) and vesicles were successfully detected, even if they were not homogeneously distributed in the membrane. Using direct and indirect tests, the cytocompatibility of the membranes with and without EVs could be proven and showed significant differences compared to the toxic control (p < 0.05). Additionally, proliferation of L929 cells was increased on membranes functionalized with EVs (p > 0.05).

Harmonizing Thickness and Permeability in Bone Tissue Engineering: A Novel Silk Fibroin Membrane Inspired by Spider Silk Dynamics.

Guided bone regeneration gathers significant interest in the realm of bone tissue engineering; however, the interplay between membrane thickness and permeability continues to pose a challenge that can be addressed by the water-collecting mechanism of spider silk, where water droplets efficiently move from smooth filaments to rough conical nodules. Inspired by the natural design of spider silk, an innovative silk fibroin membrane is developed featuring directional fluid transportation via harmoniously integrating a smooth, dense layer with a rough, loose layer; conical microchannels are engineered in the smooth and compact layer. Consequently, double-layered membranes with cone-shaped microporous passageways (CSMP-DSF membrane) are designed for in situ bone repair. Through extensive in vitro testing, it is noted that the CSMP-DSF membrane guides liquid flow from the compact layer's surface to the loose layer, enabling rapid diffusion. Remarkably, the CSMP-DSF membrane demonstrates superior mechanical properties and resistance to bacterial adhesion. When applied in vivo, the CSMP-DSF membrane achieves results on par with the commercial Bio-Gide collagen membranes. This innovative integration of a cross-thickness wetting gradient structure offers a novel solution, harmonizing the often-conflicting requirements of material transport, mechanical strength, and barrier effectiveness, while also addressing issues related to tissue engineering scaffold perfusion.

Biomedical Applications of Electro-Initiated Polymerisation on Ti6Al4 V Titanium Alloy using Silk Fibroin Coatings for Antibiotic Delivery and Improved Cell Metabolism.

Silk fibroin interactions with metallic surfaces can provide utility for medical materials and devices. Toward this goal, titanium alloy (Ti6Al4 V) was covalently grafted with polyacrylamide via electrochemically reducing 4-nitrobenzene diazonium salt in the presence of acrylamide. Analysis of the modified surfaces with FT-IR spectra, SEM and AFM were consistent with surface grafting. Functionalised titanium samples with a silk fibroin membrane, with and without impregnated therapeutics, were used to assess cytocompatibility and drug delivery. Initial cytocompatibility experiments using fibroblasts showed that the functionalised samples, both with and without silk fibroin coatings, supported significant increases between 72-136 % in cell metabolism, compared to the controls after 7 days. A 7-days release profiling showed consistent bacterial inhibition through gentamicin release with average inhibition zones of 239 mm2. Over a 5-week period, silk fibroin coated samples, both with and without growth factors, supported better human mesenchymal stem cell metabolism with increases reaching 1031 % and 388 %, respectively, compared to samples without the silk fibroin coating with.

Next-generation self-adhesive dressings: Highly stretchable, antibacterial, and UV-shielding properties enabled by tannic acid-coated cellulose nanocrystals

Hydrogels with excellent high-water uptake and flexibility have great potential for wound dressing. However, pure hydrogels without fiber skeleton faced poor water retention, weak fatigue resistance, and mechanical strength to hinder the development of the dressing as next-generation functional dressings. We prepared an ultrafast gelation (6 s) Fe3+/TA-CNC hydrogel (CTFG hydrogel) based on a self-catalytic system and bilayer self-assembled composites. The CTFG hydrogel has excellent flexibility (800% of strain), fatigue resistance (support 60% compression cycles), antibacterial, and self-adhesive properties (no residue or allergy after peeling off the skin). CTFG@S bilayer composites were formed after electrospun silk fibroin (SF) membranes were prepared and adhesive with CTFG hydrogels. The CTFG@S bilayer composites had significant UV-shielding (99.95%), tensile strain (210.9 KPa), and sensitive humidity-sensing properties. Moreover, the integrated structure improved the mechanical properties of electrospun SF membranes. This study would provide a promising strategy for rapidly preparing multifunctional hydrogels for wound dressing.

Polyphosphate-loaded silk fibroin membrane as hemostatic agent in oral surgery: a pilot study

PurposePost-interventional hemorrhage can result in serious complications, especially in patients with hemostatic disorders. Identification of safe and efficient local hemostatic agents is important, particularly in the context of an ageing society and the emergence of new oral anticoagulants. The aim of this in vitro study was to investigate the potential of silk fibroin membranes coated with the inorganic polymer polyphosphate (polyP) as a novel hemostatic device in oral surgery.MethodsCocoons of the silkworm Bombyx mori were degummed and dissolved. Varying amounts of long-chain polyP (2–2000 µg/mm2) were adsorbed to the surface of silk fibroin membranes. Analysis of the procoagulant effect of polyP-coated silk membranes was performed using real-time thrombin generation assays in human plasma. Increasing concentrations of polyP (0.15–500 µg/ml) served as a positive control, while uncoated silk fibroin membranes were used as negative control.ResultsPolyP-coated silk fibroin membranes triggered coagulation when compared to plasma samples and pure silk fibroin membranes. A polyP-dose-dependent effect of thrombin generation could be found with a maximum (ETP = 1525.7 nM⋅min, peak thrombin = 310.1 nM, time to peak = 9.8 min, lag time = 7.6 min.) at 200 µg/mm2 of polymer loading on the silk fibroin membrane surface.ConclusionsIn this study, it was demonstrated that silk fibroin membranes coated with polyP have the potential to act as a promising novel hemostatic device.Graphical

ZIF-8 nanoparticles combined with fibroin protein co-modified TiO2 nanotube arrays to construct a drug sustained-release platform

Anodized titanium dioxide nanotubes (TNTs) on titanium surface provide a drug delivery platform for local drug therapy at the implantation site. Here, we used TNTs as the drug carrier and modified it with zeolite imidazolium salt skeleton-8 (ZIF-8) combined with silk fibroin (SF) to obtain a new drug loading platform to prolong the drug release time. The morphology, modification effect, drug release in vitro, cell biological activity and osteogenesis of the drug-loaded platform were evaluated. ZIF-8 nanoparticles are mesoporous and filled in nanotubes, and silk fibroin was covered on the surface of nanotubes in the form of thin films. In vitro drug release experiments showed that the silk fibroin membrane combined with biological crosslinking agent genipin (GNP) effectively blocked the diffusion of drugs and prolonged the drug release to 60 days. The study of cell proliferation and osteogenic differentiation showed that the drug-loaded platform was biocompatible and could promote ALP secretion. Therefore, the studies imply that the drug loading platform co-modified by TNTs-based ZIF-8 nanoparticles and silk fibroin can be used as a potential and ideal orthopedic implant.

A sandwich-like silk fibroin/polysaccharide composite dressing with continual biofluid draining for wound exudate management

Optimal wound healing requires a wet microenvironment without over-hydration. Inspired by capillarity and transpiration, we have developed a sandwich-like fibers/sponge dressing with continuous exudate drainage to maintain appropriate wound moisture. This dressing is prepared by integrating a three-layer structure using the freeze-drying method. Layer I, as the side that contacts with the skin directly, consists of a hydrophobic silk fibroin membrane; Layer II, providing the pumping action, is made of superabsorbent chitosan-konjac glucomannan sponge; Layer III, accelerating evaporation sixfold compared to natural evaporation, is constructed with a graphene oxide soaked hydrophilic cellulose acetate membrane. Animal experiments showed that the composite dressing had superior wound-healing characteristics, with wounds decreasing to 24.8% of their original size compared to 28.5% for the commercial dressing and 43.2% for the control. The enhanced wound healing can be ascribed to the hierarchical porous structure serves as the fluid-driving factor in this effort; the hydrophilicity of a membrane composed of silk fibroin nanofibers is adjustable to regulate fluid-transporting capacity; and the photothermal effect of graphene oxide guarantees exudates that have migrated to the top layer to evaporate continuously. These findings indicate the unidirectional wicking dressing has the potential to become the next generation of clinical dressings.

Research on Silk Fibroin Biomaterials for Wound Dressing

With the development of the times, biology and textile technology industry has been greatly promoted. Domestic and foreign research focus on silk fibroin gradually shifted from the traditional textile field to the biomedical textiles field .the research on silk fibroin wound dressing is gradually developed, which has a great impact on accelerating wound repair. Studies have shown that the effect of wound repair is closely related to the physical and chemical properties of the raw materials. These characteristics also show that silk can be designed flexibly according to the requirements of dressing. Similarly, the production process of silk fibroin dressings and the association between adhesion and drug delivery also have a great impact. This article will elaborate the performance characteristics, advantages and problems in the research process of silk fibroin dressings, including silk fibroin membrane, silk fibroin hydrogel, silk fibroin scaffold, nanofiber membrane and other materials, as well as some new silk fibroin wound dressings currently under research, and clarify the development direction and outlook of silk fibroin in the future.

Construction and performance study of double-layer periosteal material for repairing bone tissue damage

Microscopic observation is necessary for the treatment of bone tissue microloss. To observe the process of bone tissue maturation is an essential research content in the field of orthopaedics. In many cases, people have to distinguish between new bone and mature bone, sometimes involving software calculation, and conventional HE staining obviously cannot fully meet the requirements. The quality of imaging directly affects the therapeutic effect of medical staff. In order to prove the effect of laser scanning confocal microscope (LSCM) on the observation of bone tissue micro damage, a piece of pig iliac bone and a piece of human femoral head were selected. The two kinds of bone tissue were divided into three small pieces respectively, and then stained with calcein green and alizarin red, or added with 5 ml of 1000 ml/L ethanol, and then placed under the LSCM and fluorescein Scanning under light microscope. This article uses silk fibroin as the raw material to prepare high-strength bilayer membranes using rotary evaporation method. Through relevant performance experiments, the results show that the mechanical properties of the double-layer silk fibroin film are about 12.48 MPa, and the tensile strength at break is about 13.66%. With the addition of hydroxyapatite, the mechanical properties of the silk fibroin film are improved. The addition of VEGF has little effect on the mechanical properties, and the addition of growth factor has little effect on the tensile strength of the material. The double-layer silk fibroin membrane was degraded in protease for 2 weeks, with a mass loss of about 19.3%. There was almost no degradation phenomenon in PBS solution; The release of VEGF from the double-layer silk fibroin membrane was about 17.3% after 2 weeks, with a relatively fast release rate in the early stage, and then the rate slowed down. The total release of VEGF decreased compared to the pure SF/VEGF membrane. Through the analysis of the scanning image, it is found that the image signal-to-noise ratio of alizarin red stained human femoral head is 6.956 higher than that of fluorescence microscope. In terms of image error rate, fluorescence microscope is 4.228 higher than laser scanning confocal microscope. The edge definition of laser scanning confocal microscope was 22.17 higher than that of fluorescence microscope, and the image clarity of stained bone tissue was higher than that of bone tissue only added ethanol. Therefore, the imaging effect of bone tissue staining is better, and the image generated by LSCM is higher than that generated by fluorescence microscope.

Influence of Fibroin Membrane Composition and Curing Parameters on the Performance of a Biodegradable Enzymatic Biosensor Manufactured from Silicon‐Free Carbon

Herein, fibroin, polylactide (PLA), and carbon are investigated for their suitability as biocompatible and biodegradable materials for amperometric biosensors. For this purpose, screen‐printed carbon electrodes on the biodegradable substrates fibroin and PLA are modified with a glucose oxidase membrane and then encapsulated with the biocompatible material Ecoflex. The influence of different curing parameters of the carbon electrodes on the resulting biosensor characteristics is studied. The morphology of the electrodes is investigated by scanning electron microscopy, and the biosensor performance is examined by amperometric measurements of glucose (0.5–10 mM) in phosphate buffer solution, pH 7.4, at an applied potential of 1.2 V versus a Ag/AgCl reference electrode. Instead of Ecoflex, fibroin, PLA, and wound adhesive are tested as alternative encapsulation compounds: a series of swelling tests with different fibroin compositions, PLA, and Ecoflex has been performed before characterizing the most promising candidates by chronoamperometry. Therefore, the carbon electrodes are completely covered with the particular encapsulation material. Chronoamperometric measurements with H2O2 concentrations between 0.5 and 10 mM enable studying the leakage current behavior.

Unidirectional Nanopore Dehydration Induces a Highly Stretchable and Mechanically Robust Silk Fibroin Membrane Dominated by Type II β-Turns.

Aqueous silk fibroin solution is dehydrated by evaporation into a water-soluble cast film (SFME) with poor mechanical properties but becomes by unidirectional nanopore dehydration (UND) into silk fibroin membrane (SFMU) with water-stable and good mechanical robustness. The thickness and tensile force of the SFMU are almost twice those of the MeOH-annealed SFME. The UND-based SFMU has a tensile strength of 15.82 MPa, an elongation of 665.23%, and a type II β-turn (Silk I) that accounts for 30.75% of the crystal structure. Mouse L-929 cells adhere, grow, and proliferate well on it. The UND temperature can be used to tune the secondary structure, mechanical properties, and biodegradability. UND induced the oriented arrangement of the silk molecules, which led to the formation of the SFMU dominated with Silk I structure. The silk metamaterial by controllable UND technology has great potential in medical biomaterials, biomimetic materials, sustained drug release, and flexible electronic substrates.

Novel Biomaterial-Binding/Osteogenic Bi-Functional Peptide Binds to Silk Fibroin Membranes to Effectively Induce Osteogenesis In Vitro and In Vivo.

Peptides can introduce new functions to biomaterials but their immobilization usually relies on inefficient physical adsorption or tedious chemical conjugation. Using the Bombyx mori silk fibroin (SF) membrane (SFm) as a model biomaterial, here, we demonstrate a universal strategy for discovering new peptides that can "stick" to a biomaterial to functionalize it. Specifically, two peptide motifs, one screened by phage display biopanning for binding to the biomaterial (i.e., SF) and another derived from an osteogenic growth factor (i.e., bone morphogenetic protein-2), are fused into a new chimeric peptide that can bind to SFm for more efficient osteogenesis. Theoretical simulations and experimental assays confirm that the chimeric peptide binds to SF with high affinity, facilely achieving its immobilization onto SFm. The peptide enables SFm to effectively induce osteogenic differentiation of human mesenchymal stem cells (MSCs) even without other osteogenic inducers and efficiently stimulate bone regeneration in a subcutaneous rat model in 8 weeks, even without MSC seeding, while not causing inflammatory responses. Since biomaterial-binding peptides can be readily screened using phage display and functional peptides can be generated from growth factors, our work suggests a universal strategy for combining them to seek new peptides for binding and functionalizing biomaterials.

Reconstruction of an orbital defect in rabbits using a silk fibroin-bone microparticle complex.

To construct a silk fibroin-bone microparticle composite based on a porous silk fibroin membrane and to study its feasibility as a material to reconstruct an orbital bone defect. A 3D porous silk fibroin membrane scaffold was constructed with a defined pore size and incorporated with bone microparticles from a New Zealand rabbit orbital bone defect. The silk fibroin-bone microparticle composite was then implanted into the orbital bone defect to promote osteogenesis along the surface of the porous silk fibroin membrane. The feasibility of constructing an ideal orbital defect repair material and the silk fibroin-bone micronucleus complex was evaluated by animal experiments, molecular biology, histomorphology, imaging, raw molecular mechanisms, and the biological behavior of the material in vivo. The silk fibroin-bone microparticle composite promotes angiogenesis and osteogenesis to repair bone defects in vivo. Moreover, SF (silk fibroin)/BD (bone dust) complex promotes osteogenesis and angiogenesis by activating FGF2 (Fibroblast Growth Factor 2) and SF scaffolds can bind and restore FGF2. Silk fibroin is biocompatible and the silk fibroin-bone microparticle complex successfully repaired orbital bone defects. Additionally, fibroblast growth factor expression around or within the remaining incompletely degraded silk fibroin materials was observed in vivo.

Combinatorial effect of pH and ionic strength in the release of charged dyes from silk fibroin membranes

Combinatorial effect of pH and ionic strength in the release of charged dyes from silk fibroin membranes

A Biomimetic Electrospun Membrane Supports the Differentiation and Maturation of Kidney Epithelium from Human Stem Cells.

Podocytes derived from human induced pluripotent stem (hiPS) cells are enabling studies of kidney development and disease. However, many of these studies are carried out in traditional tissue culture plates that do not accurately recapitulate the molecular and mechanical features necessary for modeling tissue- and organ-level functionalities. Overcoming these limitations requires the design and application of tunable biomaterial scaffolds. Silk fibroin is an attractive biomaterial due to its biocompatibility and versatility, which include its ability to form hydrogels, sponge-like scaffolds, and electrospun fibers and membranes appropriate for tissue engineering and biomedical applications. In this study, we show that hiPS cells can be differentiated into post-mitotic kidney glomerular podocytes on electrospun silk fibroin membranes functionalized with laminin. The resulting podocytes remain viable and express high levels of podocyte-specific markers consistent with the mature cellular phenotype. The resulting podocytes were propagated for at least two weeks, enabling secondary cell-based applications and analyses. This study demonstrates for the first time that electrospun silk fibroin membrane can serve as a supportive biocompatible platform for human podocyte differentiation and propagation. We anticipate that the results of this study will pave the way for the use of electrospun membranes and other biomimetic scaffolds for kidney tissue engineering, including the development of co-culture systems and organs-on-chips microphysiological devices.

Separation performance of alcohol-induced silk fibroin membranes with homogeneous and heterogeneous microstructures

Biological membranes were prepared from silk fibroin (SF) to investigate the mechanism SF microstructure that induced by different alcohols (C1–C4OH). SF membranes which were induced by less carbon of alcohols had a more hydrophilic surface (∼44.4°) than that induced by multi-carbon alcohol (∼80.5°). Positron annihilation spectrum showed that treating SF membrane using highly polar methanol/water generates heterogeneous structures. The internal hydrophobic segment had more β-sheets and smaller free volume than the internal hydrophilic segments because the latter flipped over to the surface. Consequently, the methanol/water-induced SF membrane showed excellent isopropyl alcohol separation efficiency. The low polar butanol/water-induced SF membranes formed homogeneous structures with a more hydrophobic surface and a larger total free volume than the methanol/water-induced SF membranes. Therefore, the crystallinity of the SF membranes could be controlled through different alcohols/water treatment, where the homogeneous phase could transform into the heterogeneous phase.