Silk Fibroin Polymer Research Articles

Highly Efficient Color Conversion of 3D Photonic Crystal Phosphor Films for Micro‐Light‐Emitting Diode Applications

The color conversion efficiency of phosphor films can be significantly improved by producing them in the shape of photonic crystals (PhCs). When light with photonic band‐edge wavelengths is incident on a PhCs phosphor film, the excitation photons are resonantly absorbed, enhancing the emission intensity. This study develops three‐dimensional PhC phosphor films based on self‐assembled inverse opal structures. PhC phosphors are constructed using a silk fibroin polymer and red organic fluorescent dyes (λpeak ≈ 610 nm) doped into it. The photonic structures are designed using electromagnetic wave simulations and photonic band structure analyses. The fabricated PhC phosphor films are integrated with blue micro‐light‐emitting diode (micro‐LED) chips (λpeak ≈ 452 nm), resulting in a color conversion efficiency increase of more than 1.5 times that of bulk phosphor films. Additionally, experiments are performed using various micro‐LED chips with a size of less than 100 μm. Overall, the results of this study demonstrate the potential of PhC phosphor films in future micro‐LED‐based devices and applications, including displays and communication systems.

Bioresponsive Self‐Reinforcing Sericin/Silk Fibroin Hydrogel for Relieving the Immune‐Related Adverse Events in Tumor Immunotherapy

AbstractDespite the immense potential of immune checkpoint blockade (ICB) therapy in tumor treatment, its widespread clinical application is currently limited by unsatisfactory curative effect and off‐target adverse effect. Herein, an injectable sericin (SS)/silk fibroin (SF) recombinant hydrogel, termed SF‐SS‐SMC hydrogel, is developed to enable local delivery of anti‐CD47 antibody (α CD47). The hydrogel displays self‐reinforcement in high H2O2 concentration of tumor microenvironment (TME), as the SS/Fe2+ supramolecular nanocomplex (SS‐SMC) inside the hydrogel converts H2O2 to reactive oxygen species (ROS), further triggering additional crosslinking among the SF polymers. Therefore, the SF‐SS‐SMC hydrogel has an in vivo retention time longer than 21 days and acts as a reservoir for the long‐term sustained release of α CD47. More importantly, the SF‐SS‐SMC hydrogel itself efficiently regulates the remodeling of a protumor immunosuppressive TME to an antitumoral TME through switching of tumor‐associated macrophages from an anti‐inflammatory M2 phenotype to a proinflammatory M1 phenotype without additional drugs. Based on the combined effect of sustained α CD47 release and TME reprogramming, the SF‐SS‐SMC hydrogel has satisfactory immunotherapeutic effects in the treatment of local, abscopal, remitting, and metastatic tumors. Further advantages, including low cost of production, simple fabrication, and ease of use, make it promising for commercial mass production.

Synergistic effect of miR-9 overexpression and electrical induction on differentiation of conjunctiva mesenchymal stem cells into photoreceptor-like cells.

A variety of genes and materials can induce the differentiation of stem cells. The purpose of this work was to investigate the effect of microRNA-9 (miR-9) overexpression and electrical induction on the photoreceptor differentiation of Conjunctiva Mesenchymal Stem Cells (CJMSCs). In this study, an electroconductive scaffold (silk fibroin polymer (SF) and reduced graphene oxide (rGo) nanoparticles) was fabricated by electrospinning method, and its characteristics such as diameter, graphene distribution, compound, conductivity, and toxicity were evaluated by scanning and transmission electron microscopy (SEM and TEM), FTIR, electrochemical impedance spectroscopy, and MTT assay. The cells were transduced by a lentiviral vector carrying miR-9, then electrical induction was implied on mir-9-CJMSCs, cultivated on the fabricated scaffold, and the expressions of neural and photoreceptor marker genes were evaluated by RT-qPCR. A uniform, smooth appearance with lower diameter, uniform distribution of rGo nanoparticles across the fibers, and lower resistance were shown in SF-rGo fibrous scaffold. After electrical stimulation, lower and higher expression of neural marker genes and photoreceptor marker genes (Rhodopsin, PKC) were documented, respectively. Finally, we proposed that the combinational approach of miR-9 overexpression and electrical induction leads CJMSCs to photoreceptor-like cells.

PC12 cells proliferation and morphological aspects: Inquiry into raffinose-grafted graphene oxide in silk fibroin-based scaffold

Peripheral nerves injuries (PNIs) still associated with both clinical and social problems. Accordingly, tissue engineers’ and surgeons’ attentions have been drawn for finding efficient solutions. Herein, scaffolds based on silk fibroin (SF)/raffinose-grafted-GO (S.RafGO) nanocomposite were fabricated. Subsequently, PC12 cells growth in term of number and morphology were investigated on neat SF polymer, SF/GO (S.GO), and S.RafGO scaffolds. Characterization via scanning electron microscopy (SEM) exhibited more fibrous structures with few lamellar nanosheets for S.GO; although, S.RafGO showed extended lamellar with lower fibrous structure. Due to the incorporation of GO and raffinose-GO nanosheets into SF structure, electrical conductivity increased ~30 and 40%, respectively. Water contact angle data revealed that S.RafGO is more wettable than SF and S.GO. Real-time PCR technique detected higher expressions of the β-tubulin, MAP2 genes on S.RafGO scaffolds in comparison with S.GO and the control group. Immunocytochemistry staining studies confirmed the overexpression of neural-specific proteins including nestin, β-tubulin of S.GO, and S.RafGO nanocomposites in comparison with pure SF scaffolds.

Silk Fibroin Based Magnetic Nanocomposites for Actuator Applications

The need for technologies based environmentally friendlier materials, able to minimize the global dependence on fossil fuel derivatives, promotes the development of new hybrid materials based on natural polymers, such as silk derivatives. This work reports on a new generation of magnetically active materials based on silk fibroin (SF) from Bombyx mori silkworm. Magnetic cobalt ferrite (CFO) nanoparticles are introduced in an SF polymer matrix to develop CFO/SF nanocomposites with filler contents of up to 20 wt%. It is shown that the inclusion of CFO nanoparticles affects the β‐sheet conformation of SF polymer having relevant effect on mechanical and thermal properties. The incorporation of conductive nanoparticles into nonconductive matrix, induces an increase in electric conductivity and also in dielectric constant. The primitive magnetic behavior of CFO nanoparticles is successfully maintained after their incorporation into SF, which has made possible the processing of magnetic SF. These results enable the design and fabrication of a fully functional magnetic actuator based on SF, proving the suitable natural polymer‐based magnetic materials for a new generation of environmental‐friendlier smart and multifunctional materials.

Silk Fibroin Bending Actuators as an Approach Toward Natural Polymer Based Active Materials.

This work reports on the development of ionic liquid (IL)/silk fibroin (SF) composite films as electroactive polymers actuators. Different contents (20, 40, and 60% wt) of 1-butyl-3-methylimidazolium tricyanomethanide ([Bmim][C(CN3)]) and choline dihydrogen phosphate ([Ch][DHP]) ILs were incorporated into the SF polymer matrix. Due to IL-SF interactions, morphological changes such as globule-like nanostructures are induced in the samples. High concentrations of IL promote SF β-sheet formation above 65%. Further, an increase in the thermal stability of the SF was observed through the incorporation of [Bmim][C(CN3)]. IL type and content allow tuning of the electrical response as well as achieving bending actuation. [Bmim][C(CN3)]/SF samples allow bending responses up to 0.5 at an applied voltage of 3 V. In conclusion, this work demonstrates the ability of IL/SF composites to act as electroactive polymer actuators and opens new perspectives in the application of natural resources for smart materials.

Silk Fibroin-Coated Nanoagents for Acidic Lysosome Targeting by a Functional Preservation Strategy in Cancer Chemotherapy.

Background: Premature drug leakage and inefficient cellular uptake are stand out as considerable hurdles for low drug delivery efficiency in tumor chemotherapy. Thus, we established a novel drug delivery and transportation strategy mediated by biocompatible silk fibroin (SF)-coated nanoparticles to overcome these therapeutic hurdles.Methods: we first synthesised a TME-responsive biocompatible nanoplatform constructed of amorphous calcium carbonate (ACC) cores and SF shells for enhanced chemotherapy by concurrently inhibiting premature drug release, achieving lysosome-targeted explosion and locally sprayed DOX, and monitoring via PAI, which was verified both in vitro and in vivo.Results: The natural SF polymer first served as a “gatekeeper” to inhibit a drug from prematurely leaking into the circulation was demonstrated both in vitro and in vivo. Upon encountering TMEs and targeting to the acidic pH environments of lysosomes, the sensitive ACC nanoparticles were gradually degraded, eventually generating a large amount of Ca2+ and CO2, resulting in lysosomal collapse, thus preventing both the efflux of DOX from cancer cells and the protonation of DOX within the lysosome, releasing multiple hydrolytic enzyme to cytoplasm, exhibiting the optimal therapeutic dose and remarkable synergetic therapeutic performance. In particular, CO2 gas generated by the pH response of ACC nanocarriers demonstrated their imaging capability for PAI, providing the potential for quantifying and guiding drug release in targets.Conclusion: In this work, we constructed TME-responsive biocompatible NPs by coating DOX-preloaded ACC-DOX clusters with SF via a bioinspired mineralization method for efficient therapeutics. This functional lysosome-targeted preservation-strategy-based therapeutic system could provid novel insights into cancer chemotherapy.

Silk fibroin/nanohydroxyapatite hydrogels for promoted bioactivity and osteoblastic proliferation and differentiation of human bone marrow stromal cells

Silk fibroin (SF) is a natural, biocompatible, and biodegradable polymer having a great potential for the successful regeneration of damaged bone tissue. In the present work, nanohydroxyapatite (nanoHA) was incorporated into SF polymer to form a bioactive composite hydrogel for applications as bone implants. The degradation and bioactive properties of SF/nanoHA composite hydrogels were evaluated. Additionally, biological investigations of human bone marrow stromal cells (hBMSCs) viability, proliferation and differentiation to the osteoblastic phenotype were conducted. The incorporation of nanoHA in SF polymer matrices improved the bioactivity of the hydrogels. The biological results highlighted that the SF/nanoHA composite hydrogels are suitable for hBMSCs attachment and proliferation, while a test for alkaline phosphatase (ALP) and bone morphogenetic protein 2 (BMP-2) expression suggested osteoblast differentiation. Additionally, a cell staining method for ALP allowed to observe cell infiltration with active production of ALP by the infiltrated cells, paving the way to use the proposed composite hydrogel for bone tissue regeneration.

Estradiol-Loaded Poly(ε-caprolactone)/Silk Fibroin Electrospun Microfibers Decrease Osteoclast Activity and Retain Osteoblast Function

Estrogen, a steroid hormone, plays an important role in modulating osteoclast proliferation and development. Estrogen deficiency boosts osteoclast activity, leading to osteoporosis in elderly women. In this study, 17-ß estradiol (E2)-loaded poly(ε-caprolactone) (PCL)/silk fibroin (SF) electrospun microfibers were developed as a proposed localized E2 delivery system to treat osteoporotic fractures. PCL is a synthetic polymer known for its biocompatibility and excellent mechanical properties. The bioactivity of PCL was enhanced by mixing it with a natural SF polymer that has low immunogenicity and inherent bioactivity. Different ratios of PCL/SF blends were electrospun and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and water contact angle measurement. PCL and SF at a ratio of 50:50 (PCL50/SF50) augmented cell proliferation of murine preosteoblast MC3T3-E1 cells and murine preosteoclast RAW 264.7 cells. Hence, PCL50/SF50 was selected and mixed with three concentrations of E2 to produce electrospun fiber mesh (0.1% E2@PCL/SF, 1% E2@PCL/SF, and 5% E2@PCL/SF). Sustained release of E2 was obtained for about 3 weeks at higher E2 concentration 5% E2@PCL/SF. An E2-loaded PCL50/SF50 elecrospun microfiber (1% E2@PCL/SF and 5% E2@PCL/SF) reduced tartrate-resistant acid phosphate activity, total DNA, and multinucleated cell formation of osteoclasts. On the other hand, the alkaline phosphatase activity and collagen I expression of osteoblasts were retained on all E2-loaded electrospun microfibers. The E2@PCL/SF system shows potential to be used for localized E2 delivery for the treatment of osteoporotic fractures.

Moisture Sorption as a Potential Condition Marker for Historic Silks: Noninvasive Determination by Near-Infrared Spectroscopy

Given their ephemeral nature, the preservation of historic silks can be problematic. Rapid, on-site condition monitoring would offer significant benefits to conservators and museum curators concerned with continued access to collections. In this paper, near-infrared spectroscopy (NIR) is investigated as a noninvasive approach to the characterization of silk fabrics and particularly for determining the moisture content of silks as a potential age-related marker. Bands within the NIR spectrum of silk are assigned to contributions from water and the silk fibroin polymer. The water bands may be deconvolved to show separate contributions from bound and structural water. When silk is exposed to deuterium oxide, the water OH NIR bands are rapidly lost. The accompanying changes in the amide-related NIR absorptions reflect differential accessibility of regions within the semi-crystalline fibroin aggregate. NIR spectra were recorded while silk was maintained at a range of relative humidity; complementary gravimetry provided absolute reference data for moisture sorption. A single spectral parameter, the intensity of the water combination band, is sufficient to indicate the relative moisture content of silk and allows distinction of unaged and heat, light, and humidity aged silks. The results confirm that NIR has significant potential for on-site studies at collections in support of the preservation and access of our silk heritage.