Fibroin Powder Research Articles

Preparation and study of properties of sorbents based on the fibrous waste of “Bombyx mori” natural silk

The work presents information on obtaining hydrolyzed fibroin powder with high sorption properties under the influence of ultra-high frequency rays from the fibrous waste of the silk industry in an acidic environment, as well as information on its composition, structure, and sorption properties. During the research, it was found that the formation of hydrolyzed fibroin powder is caused by the hydrolysis of alpha- and random chains of fibroin. In differential scanning calorimetry analysis, it was shown that hydrolyzed fibroin is thermally structurally stable up to 210 °C and capable of sorption of gold and silver ions in large quantities. Using the samples obtained by treating the hydrolyzed fibroin powders in different medium solutions, cottonseed oil was whitened, and the peroxide content of the oil was reduced from 12 mmol/kg to 2.2 mmol/kg. By lowering it to this point, it is possible to increase the oil's shelf life.

Dopamine-modified silk fibroin powder for adsorption of heavy metal ions in water

Dopamine-modified silk fibroin powder for adsorption of heavy metal ions in water

The production of soluble regenerated silk fibroin powder with high molecular weight and silk protein-based materials

The aqueous solution of regenerated silk fibroin (RSF) is considered as the raw material to produce various silk protein-based materials, including hydrogel, film, rod and fiber, etc. with significant mechanical properties. However, the aqueous solution of RSF is usually unstable within a few days or even hours in terms of its essential properties, because the conformation of the RSF chain would spontaneously transfer from random coil to β-sheet in water. In this work, we developed a way to harvest the RSF powder through an optimized spray drying method via rapid drying at a relatively low temperature. It was demonstrated that no severe degradation and conformational transition of the RSF chain occurred during powder preparation, and the RSF powder exhibited remarkable solubility in water and long stability at room temperature. Importantly, there are no obvious differences in the mechanical properties of the silk protein-based materials made from the aqueous solution from the spray-dried RSF powder (Sp-RSF) and from fresh RSF solution. Indeed, such amorphous Sp-RSF powder, in which the protein chain was dominated by random coil conformation, not only promised as the raw material for large-scale silk protein-based products in various applications but also provided the basis for fabricating bulk silk protein materials via the untraditional processing of silk fibroin, such as molding with the help of heat and moisture.

A Mechanoluminescent ZnS:Cu/PDMS and Biocompatible Piezoelectric Silk Fibroin/PDMS Hybrid Sensor for Self‐Powered Sensing and Artificial Intelligence Control

AbstractMechanoluminescence (ML) is luminescence induced due to mechanical stress, providing intuitive responses to strain‐related events. Piezoelectricity is the conversion of mechanical strain into electrical signals, offering a quantitative measurement of force/deformation. Combining ML and piezoelectricity within a single device provides a comprehensive understanding of mechanical events, providing qualitative and quantitative information about strain‐related phenomena. A ZnS:Cu/polydimethylsiloxane (PDMS) composite and a biocompatible silk fibroin/PDMS composite are prepared to generate ML and electrical signals, respectively. An innovative method for obtaining powder from silk fabrics is employed. The microstructure and composition of silk fibroin powder are also examined via X‐ray diffraction and Fourier Transform Infrared (FTIR) spectroscopy. Mechanical stimuli such as pressure, stretching, twisting, bending, vibration, and rubbing are applied to the device to demonstrate optical and electrical responses. Under pressure, a voltage of 3.82 V and an output current of 201.6 nA are generated at a force of 1 N. Furthermore, a handwritten test is conducted to qualitatively visualize letters based on ML effects and explore the feasibility of using artificial intelligence to classify voltage signals generated during writing into their corresponding letters. This biocompatible, dual‐modal self‐powered sensor demonstrates broad applicability in wearable technology, biomechanics, human–machine interaction, security, and energy harvesting.

FABRICATION OF SILK FIBROIN AND FLUORESCENT SILK FIBROIN FIBERS VIA ELECTROSPINNING

Fibroin, derived from cocoon, is a natural polymer used widely and increasingly in various fields. In recent years, the development of fluorescent fibroin has gained attention in the field of tissue engineering, because of its biocompatibility, oxygen and water vapor permeability, biodegradability, and ability to be tested non-invasively. In this work, silk fibroin and fluorescent silk fibroin fibers were fabricated via electrospinning, a simple process through which continuous submicron fibers can be produced. Degummed silk was extracted by dissolving in calcium chloride solution. The fibroin powder was dissolved in formic acid to form 10, 12, and 14 wt.% solutions. Fluorescent fibroin solutions were achieved with addition of fluoresceine sodium (FS) as fluorescent dye. The fluorescent solutions were prepared at 10 wt.% fibroin with varying FS concentration at 0.1, 0.3, and 0.5 wt.%, and at 0.5 wt.% FS with varying fibroin concentration at 10, 12, and 14 wt.%. The fibroin solutions were fabricated into fibers via electrospinning using an applied voltage of 20 kV. The surface morphology of silk fibroin fibers and fluorescent fibroin fibers, observed by scanning electron microscope (SEM), showed long continuous fibers. The average fiber diameter, in sub-micron range, was found to increase with fibroin concentration. The fluorescence intensity observed by fluorescence spectrophotometer was found to increase with decreasing fluorescent dye concentration. The functional groups and chemical structure of silk fibroin fibers analyzed by infrared spectroscopy (IR) were not affected by the addition of the fluorescent dye.

Surface modification of silk fibroin powder and its application in oil–water separation

The recent increase in maritime trade and transportation has increased the seriousness of environmental pollution caused by offshore oil leakage. In this study, silk fibroin (SF) powder is modified using chitosan and sodium stearate, and is used for oil–water separation. The structure of the modified SF powder is characterized through Fourier-transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction. The modified SF powder exhibits better selectivity for oil than the original SF powder, for oil–water separation. Its oil-absorption capacity for soybean oil is 5.5965 g·g−1, which is nearly twice that of the original SF powder. The oil absorption capacity for engine oil is 5.3823 g·g−1, which is more than twice that of the original SF powder. This work provides a new method and concept for the study of oil–water separation.

Porous Thermoplastic Molded Regenerated Silk Crosslinked by the Addition of Citric Acid.

Thermoplastic molded regenerated silk fibroin was proposed as a structural material in tissue engineering applications, mainly for application in bone. The protocol allows us to obtain a compact non-porous material with a compression modulus in the order of a Giga Pascal in dry conditions (and in the order of tens of MPa in wet conditions). This material is produced by compressing a lyophilized silk fibroin powder or sponge into a mold temperature higher than the glass transition temperature. The main purpose of the produced resin was the osteofixation and other structural applications in which the lack of porosity was not an issue. In this work, we introduced the use of citric acid in the thermoplastic molding protocol of silk fibroin to obtain porosity inside the structural material. The citric acid powder during the compression acted as a template for the pore formation. The mean pore diameter achieved by the addition of the higher amount of citric acid was around 5 μm. In addition, citric acid could effectively crosslink the silk fibroin chain, improving its mechanical strength. This effect was proved both by evaluating the compression modulus (the highest value recorded was 77 MPa in wet conditions) and by studying the spectra obtained by Fourier transform infrared spectroscopy. This protocol may be applied in the near future to the production of structural bone scaffolds.

The impact of medication on osseointegration and implant anchorage in bone determined using removal torque—A review

Permanently anchored metal implants are frequently used in dental, craniomaxillofacial, and orthopaedic rehabilitation. The success of such therapies is owed to the phenomenon of osseointegration—the direct connection between the living bone and the implant. The extent of biomechanical anchorage (i.e., physical interlocking between the implant and bone) can be assessed with removal torque (RTQ) measurement. Implant anchorage is strongly influenced by underlying bone quality, involving physicochemical and biological properties such as composition and structural organisation of extracellular matrix, extent of micro-damage, and bone turnover. In this review, we evaluated the impact of various pharmacological agents on osseointegration, from animal experiments conducting RTQ measurements. In addition to substances whose antiresorptive and/or anti-catabolic effects on bone are well-documented (e.g., alendronate, zoledronate, ibandronate, raloxifene, human parathyroid hormone, odanacatib, and the sclerostin monoclonal antibody), positive effects on RTQ have been reported for substances that do not primarily target bone (e.g., aminoguanidine, insulin, losartan, simvastatin, bone morphogenetic protein, alpha-tocopherol, and the combination of silk fibroin powder and platelet-rich fibrin). On the contrary, several substances (e.g., prednisolone, cyclosporin A, cisplatin, and enamel matrix derivative) tend to adversely impact RTQ. While morphometric parameters such as bone-implant contact appear to influence the biomechanical anchorage, increased or decreased RTQ is not always accompanied by corresponding fluctuations in bone-implant contact. This further confirms that factors such as bone quality underpin biomechanical anchorage of metal implants. Several fundamental questions on drug metabolism and bioavailability, drug dosage, animal-to-human translation, and the consequences of treatment interruption remain yet unanswered.

Tuning surface texture of thermoplastic polyurethane/silk fibroin composites by phase separation method

Silk fibroin powder made from waste silk has gained considerable attention because of its outstanding physicochemical properties. In this study, thermoplastic polyurethane/silk fibroin (TPU/SF) composites were successfully prepared by combining different phase separation methods. The transformation of porous to compact films prepared by vapor/nonsolvent-induced phase separation (V–NIPS) as well as solvent evaporation/nonsolvent-induced phase separation (E-NIPS) using binary solvents. The effect of the film-formation method on the morphology, structure, and performance of the composite films were investigated. Compared with the surface of E-NIPS composite films, that of V–NIPS composite films had many micron-sized craters. Furthermore, SEM and porosity analysis results further supported the proposed film-formation mechanism. Upon the addition of 30 wt% SF, V–NIPS5 showed good mechanical properties with a stress of 16.2 MPa, strain of 1241.2%, and toughness of 118.2 MJ/m3. E-NIPS25 also showed good mechanical properties with a stress of 25.5 MPa, strain of 1089.7%, and toughness of 144.7 MJ/m3. The strengthened interface interaction between SF and TPU was observed through the analysis of the fractured surfaces. Furthermore, the V–NIPS composite films showed good hydrophilicity and biocompatibility. This approach of constructing unique surface structures has potential applications in functional fields, such as development of bionic materials and biological cell adhesion materials.

A Genipin Crosslinked Silk Fibroin Bulk Material by Compression Moulding with Self-Recovering Mechanical Properties in Physiological Conditions

Compression molding of silk fibroin powder leads to a material that quickly degrades losing its mechanical stiffness and strength when exposed to physiological conditions. Considering the bone scaffold applications for which this material is intended the remarkable weakening after implantation strongly limits its usage to non-structural purposes. This work proposes a new approach that allows a recovery of mechanical properties in physiological conditions, due to a progressive fibroin crosslinking triggered by genipin and humidity. Crosslinking is accompanied by a darkening of the silk monoliths. An extensive characterization prove that the genipin-added fibroin, after a first loss in stiffness in physiological conditions, recovers the compressive modulus due to crosslinking and keeps its shape and structural integrity after 30 days of exposure to protease. The modulus have been maximized by optimizing the amount of genipin and the compression molding parameters by a statistical approach namely response surface methodology. Crosslinking does not hinder cell adhesion and proliferation, as suggested by a preliminary biological test, nor does it limit the versatility and the machinability of the material, as demonstrated by producing complex-shaped objects through laser cutting. Overall, genipin-crosslinked solid fibroin is a reliable material suitable for structural applications in physiological conditions.

Preparation, thermal properties and permeabilities of aluminum‐coated fabrics destined for thermal radiation protective clothing

SummaryIn this study, radiant reflective, flame retardant and water vapor permeable coatings were fabricated on aramid fabric (AF) for thermal radiation protective clothing by using a simple cost‐effective coating method, which included an aluminum paste, APP‐PER‐MEL and a silk fibroin powder in the TPU solution system. The permeability, flame retardancy, thermal stability, radiative spectral reflectance, as well as RPP of these prepared fabrics were characterized and compared with the pure AF and aluminum‐foiled AF (AF‐AF). Results show that the newly developed aluminized AF had rather high permeability, and the permeable capability would be further enhanced with the additive of silk fibroin powder. The flame retardancy (FR) of the coated fabric sample was also achieved by introducing an intumescent FR system. In contrast to the pure AF, the aluminum‐coated AF provided higher levels of radiation protection in RPP testing. This was further confirmed by the fact that aluminum‐coated AF exhibited comparative high average reflectivities (more than 0.7) in the radiant spectral range of 1547 nm to 2500 nm. Thus, the aluminum‐coated AF prepared by functional coating method exhibit great and competitive practicability in thermal protective clothing due to their excellent moisture comfort and radiant thermal protection.

Fabrication of a High-Toughness Polyurethane/Fibroin Composite without Interfacial Treatment and Its Toughening Mechanism.

Controlling the assembly modes of polymer chains and the interfacial interactions between the filler and polymer matrix is vital for improving the mechanical properties of the composites. Herein, we report an approach for significantly enhancing the toughness of unmodified silk fibroin (SF) powder from silk waste-incorporated polyurethane (PU) composite films via nonsolvent-induced phase separation (NIPS) using binary solvents. The incorporation of 50 wt % SF into the PU3 film (NIPS, binary solvents) resulted in a toughness value of 54.9 ± 0.4 MJ·m-3, exhibiting 1670.9 and 6000.0% increments compared to those of PU1-50% SF (NIPS, one solvent) and PU2-50% SF (solvent evaporation, one solvent), respectively. The toughness enhancement in the PU3-50% SF composite film benefits from the good interfacial interaction between SF and PU and the unique structure of the compacted "fishing net" with reinforced connections, which can transfer stress under loading effectively. Furthermore, the PU-SF composites with good mechanical properties may have potential applications in silklike fibers and biomimetic materials.

Aqueous Solution of a Basic Ionic Liquid: A Perspective Solvent for Extraction and Regeneration of Silk Powder from Bombyx mori Silk Cocoons

The rationale behind this study was to investigate the potential new low cost and biocompatible aqueous choline based ionic liquid for dissolution and regeneration of silk fibroin obtained from the mulberry silkworm. The silk due to its high biocompatibility and mechanical properties finds many applications in the field of biomedical science. Earlier, silk extraction methods have issues of either extraction efficiency or environmental concerns. The ionic liquid is a relatively green solvent was used to dissolve silk fibroin and optimized the process with respect to variables like temperature, time, stirring speed, type of ionic liquid and maximum dissolution ability. The dissolution process was observed through the naked eye as well as using optical microscopy. The optimized conditions at which maximum dissolution i.e. 25% was obtained, are heating the mixture at 50 °C for 2 h. Various analytical characterization such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), Zeta potential, nuclear magnetic resonance (1H NMR) and thermogravimetric analysis (TGA) was performed for cocoon, fiber and regenerated silk powder in order to understand the effect of ionic liquid treatment. FTIR, NMR and Raman spectra shows the characteristic peaks assigned to the silk. SEM analysis shows nanoparticles of silk fibroin powder. The crystallinity and thermal stabilities were decreased for regenerated silk as observed from XRD and TGA analysis. The nano-silk exhibited a zeta potential of − 24.6 ± 3 mV.

A novel highly stretchable, adhesive and self-healing silk fibroin powder-based hydrogel containing dual-network structure

We have demonstrated a novel strategy to enhance mechanical strength by designing dual-network (DN) structures. The novel self-healing hydrogel system composed of silk fibroin powder (SFP) and polyacrylamide (PAM) combines hydrogen bond supramolecular action. In addition, this system was prepared via a simple one-pot method of copolymerization. The SFP-PAM hydrogels could achieve high mechanical properties. The stress and strain at break were 0.65 MPa and 2250%, respectively. The hydrogels exhibited adhesive and self-healing properties. The fabricated multifunctional SFP-PAM hydrogel shows promise in potential applications in wound dressing and transparent artificial skins for body-adhered signal detection.

Biodegradable Composites Developed from PBAT/PLA Binary Blends and Silk Powder: Compatibilization and Performance Evaluation.

Silk fibroin powder and biodegradable polybutylene adipate terephthalate (PBAT)/poly lactide (PLA) blends were melt-mixed together to fabricate natural and synthetic polymers as possible new sources of biomaterials. Morphological observations conducted through scanning electron microscopy indicated poor dispersion of the silk powder agglomerates, which resulted from strong hydrogen interactions between silk powder chains in the PBAT/PLA matrix. Although the silk powder agglomerates decreased the mechanical properties, as silk powder fractions increased, the ternary blend with 10 wt % silk powder still displayed high impact strength of 108 J/m and tensile modulus of 1.2 GPa. On the basis of mechanical analysis, this blend offered potential applications in fields which required high impact strength. Blends which contained Joncryl experienced a decrease in storage modulus. Furthermore, rheological studies confirmed that the viscosity of the PBAT/PLA/Silk powder blends decreased, which indicated possible weakening of hydrogen bonds between the silk chains, caused by the reaction between the epoxy groups of Joncryl. This reaction provides a possible method to improve the processability of this natural polymer and to improve its distribution in polymer blends.

Silk fibroin powder prepared by nontoxic low-sodium salt system

Silk fibroin (SF) powder was prepared by a nontoxic low-sodium system to avoid introducing massive unwanted chemicals during the SF hydrolysis process. In this study, water-soluble and water-insoluble SF powder, were obtained through lyophilised SF solution by boiling degummed silk fiber in low-concentration Na2CO3 solution with a certain degree of pressure. Compared with traditional SF hydrolysis systems, this study provides a simple and potentially time-saving approach to produce SF powder at a low cost.

The effect of native silk fibroin powder on the physical properties and biocompatibility of biomedical polyurethane membrane.

Naturally derived fibers such as silk fibroin can potentially enhance the biocompatibility of currently used biomaterials. This study investigated the physical properties of native silk fibroin powder and its effect on the biocompatibility of biomedical polyurethane. Native silk fibroin powder with an average diameter of 3 µm was prepared on a purpose-built machine. A simple method of phase inversion was used to produce biomedical polyurethane/native silk fibroin powder hybrid membranes at different blend ratios by immersing a biomedical polyurethane/native silk fibroin powder solution in deionized water at room temperature. The physical properties of the membranes including morphology, hydrophilicity, roughness, porosity, and compressive modulus were characterized, and in vitro biocompatibility was evaluated by seeding the human umbilical vein endothelial cells on the top surface. Native silk fibroin powder had a concentration-dependent effect on the number and morphology of human umbilical vein endothelial cells growing on the membranes; cell number increased as native silk fibroin powder content in the biomedical polyurethane/native silk fibroin powder hybrid membrane was increased from 0% to 50%, and cell morphology changed from spindle-shaped to cobblestone-like as the native silk fibroin powder content was increased from 0% to 70%. The latter change was related to the physical characteristics of the membrane, including hydrophilicity, roughness, and mechanical properties. The in vivo biocompatibility of the native silk fibroin powder-modified biomedical polyurethane membrane was evaluated in a rat model; the histological analysis revealed no systemic toxicity. These results indicate that the biomedical polyurethane/native silk fibroin powder hybrid membrane has superior in vitro and in vivo biocompatibility relative to 100% biomedical polyurethane membranes and thus has potential applications in the fabrication of small-diameter vascular grafts and in tissue engineering.

High-concentration dispersions of exfoliated MoS2 sheets stabilized by freeze-dried silk fibroin powder

Liquid-phase exfoliation (LPE) is an attractive method for the scaling-up of exfoliated MoS2 sheets compared to chemical vapor deposition and mechanical cleavage. However, the MoS2 nanosheet yield from LPE is too small for practical applications. We report a facile method for the scaling-up of exfoliated MoS2 nanosheets using freeze-dried silk fibroin powders. Compared to MoS2 dispersion in the absence of silk fibroin powder, sonicated MoS2 dispersions with silk fibroin powder (MoS2/Silk dispersion) show noticeably higher exfoliated MoS2 nanosheet yields, with suspended MoS2 concentrations in MoS2/Silk dispersions sonicated for 2 and 5 h of 1.03 and 1.39 mg·mL–1, respectively. The MoS2 concentration in the MoS2/Silk dispersion after centrifugation above 10,000 rpm is more than four times that without the silk fibroin. The size of the dispersed silk fibroin is controlled by the change of centrifugation rate, showing the removal of silk fibroin above tens of micrometers in size after centrifugation at 2,000 rpm. Size-controlled silk fibroin biomolecules combined with MoS2 nanosheets are expected to increase the practical use of such materials in fields related to tissue engineering, biosensors and electrochemical electrodes. Atomic force microscopy and Raman spectroscopy provide the height of the MoS2 nanosheets spin-cast from MoS2 /Silk dispersions, showing thicknesses of 3–6 nm. X-ray photoelectron spectroscopy and X-ray diffraction indicate that the outermost surface layer of the hydrophobic MoS2 crystals interact with oxygen-containing functional groups that exist in the hydrophobic part of silk fibroins. The amphiphilic properties of silk fibroin combined with the MoS2 nanosheets stabilize dispersions by enhancing solvent-material interactions. The large quantities of exfoliated MoS2 nanosheets suspended in the as-synthesized dispersions can be utilized for the fabrication of vapor and electrochemical devices requiring high MoS2 nanosheets contents.

Synthesis and fluorescent pH sensing properties of nanoscale lanthanide metal-organic frameworks with silk fibroin powder as polymer ligands

A series of novel nanoscale lanthanide metal-organic frameworks with silk fibroin powder as polymer ligands were successfully obtained and studied. The silk fibroin powder was first modificated by pyromellitic acid, and then coordinated to lanthanide ions. The size of the metal-organic frameworks can be designed to the range 190–1000 nm through adding different quality of lanthanide ions. The nanoscale materials have excellent photoluminescent properties and exhibit rapid response in detection of pondus hydrogenii. Especially at acidic conditions, the characteristic emission peaks of lanthanide ions are in linear relation with pondus hydrogenii and meet linear equation. This work not only provides an effective strategy for preparation of luminescent nanoscale metal-organic frameworks using biopolymer as ligands on a molecular level but also offers a way to prepare ratiometric fluorescent pondus hydrogenii sensor for biomedical applications.

Study on improving antioxydant and antibacterial activities of silk fibroin by irradiation treatment

The silk fibroin solutions were prepared in solvent system of CaCl2. CH3CH2OH. H2O (mole ratio = 1:2:8) followed dialysis against deionized water. The 3% silk fibroin solutions were irradiated under gamma Co-60 source with dose ranging from 0 to 50 kGy at Hanoi Irradiation Centre and bio-activities of the irradiated silk fibroin solutions were investigated with different radiation doses. The results indicated that the antioxidant and antibacterial activities of fibroin were much improved by gamma irradiation. Maximum value of DPPH radical scavenging activity was 70.4% for the solution of silk fibroin irradiated at 10 kGy. Silk fibroin solutions irradiated at doses higher than 10 kGy also exhibited rather high antibacterial activity against E. coli and S. aureus. In order to estimate the applicability of our irradiated fibroin, the silk fibroin solutions were lyophilized to obtain a pure fibroin powder, then their bio-activities were compared with those of commercial silk fibroin (Proteines De Soie/ Zijdeproteine, Bioflore, Canada). Our fibroin powder revealed higher antioxidant and antibacterial activities. The amino acid compositions of our irradiated fibroin were also higher than that of the commercial product. Thus, the irradiated silk fibroin can be used for further application in cosmetic and other related fields.