Silk Fibroin Nanoparticles for Drug Delivery: Effect of Bovine Serum Albumin and Magnetic Nanoparticles Addition on Drug Encapsulation and Release

Mechanical and in vitro study of 3D printed silk fibroin and bone-based composites biomaterials for bone implant application

When treating orthopaedic damage or illness and accidental fracture, bone grafting remains the gold standard of treatment. In cases where this approach does not seem achievable, bone tissue engineering can offer scaffolding as a substitute. Defective and fractured bone tissue is extracted and substituted with porous scaffold structures to aid in the process of tissue regeneration. 3D bioprinting has demonstrated enormous promise in recent years for producing scaffold structures with the necessary capabilities. In order to create composite biomaterial inks for 3D bioprinting, three different materials were combined such as silk fibroin, bone particles, and synthetic biopolymer poly (ε-caprolactone) (PCL). These biomaterials were used to fabricate the two composites scaffolds such as: silk fibroin + bovine bone (SFB) and silk fibroin + bovine bone + Polycaprolactone (SFBP). The biomechanical, structural, and biological elements of the manufactured composite scaffolds were characterized in order to determine their suitability as a possible biomaterial for the production of bone tissue. The in vitro bioactivity of the two composite scaffolds was assessed in the simulated body fluids, and the swelling and degradation characteristics of the two developed scaffolds were analyzed separately over time. The results showed that the mechanical durability of the composite scaffolds was enhanced by the bovine bone particles, up to a specific concentration in the silk fibroin matrix. Furthermore, the incorporation of bone particles improved the bioactive composite scaffolds' capacity to generate hydroxyapatite in vitro. The combined findings show that the two 3D printed bio-composites scaffolds have the required mechanical strength and may be applied to regeneration of bone tissue and restoration, since they resemble the characteristics of native bone.

pH-Responsive Cellulose/Silk/Fe3O4 Hydrogel Microbeads Designed for Biomedical Applications

In this study, cellulose/Fe3O4 hydrogel microbeads were prepared through the sol-gel transition of a solvent-in-oil emulsion using various cellulose-dissolving solvents and soybean oil without surfactants. Particularly, 40% tetrabutylammonium hydroxide (TBAH) and 40% tetrabutylphosphonium hydroxide (TBPH) dissolved cellulose at room temperature and effectively dispersed Fe3O4, forming cellulose/Fe3O4 microbeads with an average diameter of ~15 µm. Additionally, these solvents co-dissolved cellulose and silk, allowing for the manufacture of cellulose/silk/Fe3O4 hydrogel microbeads with altered surface characteristics. Owing to the negatively charged surface characteristics, the adsorption capacity of the cellulose/silk/Fe3O4 microbeads for the cationic dye crystal violet was >10 times higher than that of the cellulose/Fe3O4 microbeads. When prepared with TBAH, the initial adsorption rate of bovine serum albumin (BSA) on the cellulose/silk/Fe3O4 microbeads was 18.1 times higher than that on the cellulose/Fe3O4 microbeads. When preparing TBPH, the equilibrium adsorption capacity of the cellulose/silk/Fe3O4 microbeads for BSA (1.6 g/g) was 8.5 times higher than that of the cellulose/Fe3O4 microbeads. The pH-dependent BSA release from the cellulose/silk/Fe3O4 microbeads prepared with TBPH revealed 6.1-fold slower initial desorption rates and 5.2-fold lower desorption amounts at pH 2.2 than those at pH 7.4. Cytotoxicity tests on the cellulose and cellulose/silk composites regenerated with TBAH and TBPH yielded nontoxic results. Therefore, cellulose/silk/Fe3O4 microbeads are considered suitable pH-responsive supports for orally administered protein pharmaceuticals.

Hydrodynamic Assembly of Astrocyte Cells in Conductive Hollow Microfibers

The manufacturing of 3D cell scaffoldings provides advantages for modeling diseases and injuries as it enables the creation of physiologically relevant platforms. A triple-flow microfluidic device is developed to rapidly fabricate alginate/graphene hollow microfibers based on the gelation of alginate induced with CaCl2 . This five-channel microdevice actualizes continuous mild fabrication of hollow fibers under an optimized flow rate ratio of 300:200:100 µL min-1 . The polymer solution is 2.5% alginate in 0.1% graphene and a 30% polyethylene glycol solution is used as the sheath and core solutions. The biocompatibility of these conductive microfibers by encapsulating mouse astrocyte cells (C8D1A) within the scaffolds is investigated. The cells can successfully survive both the manufacturing process and prolonged encapsulation for up to 8 days, where there is between 18-53% of live cells on both the alginate microfibers and alginate/graphene microfibers. These unique 3D hollow scaffolds can significantly enhance the available surface area for nutrient transport to the cells. In addition, these conductive hollow scaffolds illustrate unique advantages such as 0.728 cm3  gr-1 porosity and two times more electrical conductivity in comparison to alginate scaffolds. The results confirm the potential of these scaffolds as a microenvironment that supports cell growth.

3D-Printing of Silk Nanofibrils Reinforced Alginate for Soft Tissue Engineering

The main challenge of extrusion 3D bioprinting is the development of bioinks with the desired rheological and mechanical performance and biocompatibility to create complex and patient-specific scaffolds in a repeatable and accurate manner. This study aims to introduce non-synthetic bioinks based on alginate (Alg) incorporated with various concentrations of silk nanofibrils (SNF, 1, 2, and 3 wt.%) and optimize their properties for soft tissue engineering. Alg-SNF inks demonstrated a high degree of shear-thinning with reversible stress softening behavior contributing to extrusion in pre-designed shapes. In addition, our results confirmed the good interaction between SNFs and alginate matrix resulted in significantly improved mechanical and biological characteristics and controlled degradation rate. Noticeably, the addition of 2 wt.% SNF improved the compressive strength (2.2 times), tensile strength (5 times), and elastic modulus (3 times) of alginate. In addition, reinforcing 3D-printed alginate with 2 wt.% SNF resulted in increased cell viability (1.5 times) and proliferation (5.6 times) after 5 days of culturing. In summary, our study highlights the favorable rheological and mechanical performances, degradation rate, swelling, and biocompatibility of Alg-2SNF ink containing 2 wt.% SNF for extrusion-based bioprinting.

Wound dressing based on PVA nanofiber containing silk fibroin modified with GO/ZnO nanoparticles for superficial wound healing: In vitro and in vivo evaluations

Silk fibroin (SF), extracted from Bombyx mori, has unique physicochemical properties to achieve an efficient wound dressing. In this study, reduced graphene oxide (RGO)/ZnO NPs/silk fibroin nanocomposite was made, and an innovative nanofiber of SF/polyvinyl alcohol (PVA)/RGO/ZnO NPs was ready with the electrospinning technique and successfully characterized. The results of MIC and OD analyses were used to investigate the synthesized materials' antibacterial effects and displayed that the synthesized materials could inhibit growth against Staphylococcus aureus and Escherichia coli bacteria. However, both in vitro cytotoxicity (MTT) and scratch wound studies have shown that RGO/ZnO NPs and SF/PVA/RGO/ZnO NPs are not only non-toxic to NIH 3T3 fibroblasts, but also can cause cell viability, cell proliferation, and cell migration. Furthermore, improving the synthesized nanofiber's structural properties in the presence of RGO and ZnO NPs has been confirmed by performing tensile strength, contact angle, and biodegradation analyses. Also, in a cell attachment analysis, fibroblast cells had migrated and expanded well in the nanofibrous structures. Moreover, in vivo assay, SF/PVA/RGO/ZnO NPs nanofiber treated rats and has been shown significant healing activity and tissue regeneration compared with other treated groups. Therefore, this study suggests that SF/PVA/RGO/ZnO NPs nanofiber is a hopeful wound dressing for preventing bacteria growth and improving superficial wound repair.

Fabrication of a magnetic alginate-silk fibroin hydrogel, containing halloysite nanotubes as a novel nanocomposite for biological and hyperthermia applications

In this study, the main focus was on designing and synthesizing a novel magnetic nanobiocomposite and its application in hyperthermia cancer treatment. Regarding this aim, sodium alginate (SA) hydrogel with CaCl₂ cross-linker formed and modified by silk fibroin (SF) natural polymer and halloysite nanotubes (HNTs), followed by in situ Fe₃O₄ magnetic nanoparticles preparation. No important differences were detected in red blood cells (RBCs) hemolysis, confirming the high blood compatibility of the treated erythrocytes with this nanobiocomposite. Moreover, the synthesized SA hydrogel/SF/HNTs/Fe₃O₄ nanobiocomposite does not demonstrate toxicity toward HEK293T normal cell line after 48 and 72 h. The anticancer property of SA hydrogel/SF/HNTs/Fe₃O₄ nanobiocomposites against breast cancer cell lines was corroborated. The magnetic saturation of the mentioned magnetic nanobiocomposite was 15.96 emu g⁻¹. The specific absorption rate (SAR) was measured to be 22.3 W g⁻¹ by applying an alternating magnetic field (AMF). This novel nanobiocomposite could perform efficiently in the magnetic fluid hyperthermia process, according to the obtained results.

Optimizing the Surface Structural and Morphological Properties of Silk Thin Films via Ultra-Short Laser Texturing for Creation of Muscle Cell Matrix Model

Temporary scaffolds that mimic the extracellular matrix’s structure and provide a stable substratum for the natural growth of cells are an innovative trend in the field of tissue engineering. The aim of this study is to obtain and design porous 2D fibroin-based cell matrices by femtosecond laser-induced microstructuring for future applications in muscle tissue engineering. Ultra-fast laser treatment is a non-contact method, which generates controlled porosity—the creation of micro/nanostructures on the surface of the biopolymer that can strongly affect cell behavior, while the control over its surface characteristics has the potential of directing the growth of future muscle tissue in the desired direction. The laser structured 2D thin film matrices from silk were characterized by means of SEM, EDX, AFM, FTIR, Micro-Raman, XRD, and 3D-roughness analyses. A WCA evaluation and initial experiments with murine C2C12 myoblasts cells were also performed. The results show that by varying the laser parameters, a different structuring degree can be achieved through the initial lifting and ejection of the material around the area of laser interaction to generate porous channels with varying widths and depths. The proper optimization of the applied laser parameters can significantly improve the bioactive properties of the investigated 2D model of a muscle cell matrix.

Silk ProteinsEnriched Nanocomposite Hydrogels Based on Modified MMT Clay and Poly(2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropane Sulfonic Acid) Display Favorable Properties for Soft Tissue Engineering

Due to their remarkable structures and properties, three-dimensional hydrogels and nanostructured clay particles have been extensively studied and have shown a high potential for tissue engineering as solutions for tissue defects. In this study, four types of 2-hydroxyethyl methacrylate/2-acrylamido-2-methylpropane sulfonic acid/montmorillonite (HEMA/AMPSA/MMT) hydrogels enriched with sericin, and fibroin were prepared and studied in the context of regenerative medicine for soft tissue regenerative medicine. Our aim was to obtain crosslinked hydrogel structures using modified montmorillonite clay as a crosslinking agent. In order to improve the in vitro and in vivo biocompatibility, silk proteins were further incorporated within the hydrogel matrix. Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) were performed to prove the chemical structures of the modified MMT and nanocomposite hydrogels. Swelling and rheological measurements showed the good elastic behavior of the hydrogels due to this unique network structure in which modified MMT acts as a crosslinking agent. Hydrogel biocompatibility was assessed by MTT, LDH and LIVE/DEAD assays. The hydrogels were evaluated for their potential to support adipogenesis in vitro and human stem cells isolated from adipose tissue were seeded in them and induced to differentiate. The progress was assessed by evaluation of expression of adipogenic markers (ppar-γ2, perilipin) evaluated by qPCR. The potential of the materials to support tissue regeneration was further evaluated on animal models in vivo. All materials proved to be biocompatible, with better results on the 95% HEMA 5% AMPSA enriched with sericin and fibroin material. This composition promoted a better development of adipogenesis compared to the other compositions studied, due the addition of sericin and fibroin. The results were confirmed in vivo as well, with a better progress of soft tissue regeneration after implantation in mice. Therefore, hydrogel 95% HEMA 5% AMPSA enriched with sericin as well as fibroin showed the best results that recommend it for future soft tissue engineering application.

Activation of extracellular electron network in non-electroactive bacteria by Bombyx mori silk

Extracellular electron transfer material (EETM) has increasingly attracted attentions for the enhancing effect on multiple microbial reactions. Especially, EETM is known to be essential to activate the energy network in non-electroactive bacteria. It is motivated to find out an EETM which is natural-based, environmentally friendly, and easily produced at large-scale. In this study, Bombyx mori silk is found, for the first time, to function as an EETM by using an EETM-dependent pentachlorophenol (PCP) dechlorinating anaerobic microbial culture. Subsequently, by dividing fibroin fiber into different soluble/insoluble fractions and correlating their EET functions with their structural properties based on various spectroscopic analyses, the β-sheet configuration is suggested as an essential structure supporting the EET function of silk materials. The analyses also suggested the involvement of sulfur-containing amino acids in this function. The EET function is not degraded by boiling or acid/alkaline treatments and the material can be utilized multiple times, although it is susceptible to UV irradiation. Bombyx mori silk also enhance other microbial reactions, including Fe(III)OOH reduction, CO₂ reduction to acetate, and nitrogen fixation. This discovery provides a basis for developing biotechnology for environmental remediation, global warming reduction, and biofertilizer production using Bombyx mori silk and its wastes.

Facile design and development of nano-clustery graphene-based macromolecular protein hydrogel loaded with ciprofloxacin to antibacterial improvement for the treatment of burn wound injury

Nowadays, awareness about the burn wound is often considered difficult due to bacterial and other organism infections. The facile and eco-friendly preparations of antibiotic-loaded hydrogel-based bio-composites have great attention in the field of wound dressing for burn wound therapy and nursing care. In the present investigation, we have developed ciprofloxacin (CF)-encapsulated graphene-silk fibroin macromolecular hydrogel dressings material with unique chemical and physical properties to achieve the desirable antibacterial efficacy and healing activity. The antibacterial activity of prepared hydrogel was evaluated against bacterial pathogens treated with different concentrations of CF, which have been provided improved antibacterial activity on burn wound infection. In vitro, cytocompatibility evaluations were performed to imply the suitability of hydrogel on fibroblast cells, which has been dramatically related to in vivo wound healing. Furthermore, an in vivo wound healing analysis was carried out using a rat to observe the capability of the CF-incorporated GH/SF hydrogel matrix. Thus, this investigation widely demonstrates the healing ability of prepared hydrogel matrix and could be a significant landmark in the research on burn wound healing applications.

Polyvinylidene fluoride/silk fibroin-based bio-piezoelectric nanofibrous scaffolds for biomedical application

Since the discovery that applying electrical stimulation can promote cell growth, proliferation, and tissue regeneration, research on bio-piezoelectric materials is being actively conducted. In this study, a composite material was prepared by mixing polyvinylidene fluoride (PVDF), a conventional piezoelectric polymer, and silk fibroin (SF), a natural piezoelectric material that recently attracting attention. These two polymers were fabricated into a composite fiber mat using electrospinning technology. To find optimal conditions, SF was added in various ratios to prepare electrospun PVDF/SF mats. The characteristics of these PVDF/SF composite mats were then analyzed through various evaluations and in vitro studies. It was confirmed that PVDF and SF were successfully mixed through scanning electron microscope images and structural analysis such as x-ray diffractometer and Fourier transform infrared. The results revealed that adding an appropriate amount of SF could improve the tensile strength, enhance cell proliferation rate, and generate a voltage similar to that of a conventional PVDF-only electrospinning mat. Such fabricated electrospun PVDF/SF composite mats are expected to be useful in the bio-piezoelectric field because they can maintain piezoelectricity while compensating for the shortcomings, such as low physical properties, of a PVDF electrospun mat.

PVA based nanofiber containing CQDs modified with silica NPs and silk fibroin accelerates wound healing in a rat model

In recent years, applying various wound dressings with antibacterial activities to expedite tissue repair stages has gained remarkable attention. The intertwined three-dimensional structure of nanofibers provides unique spaces for carrying drugs and repair agents during the wound healing process. In this research, a carbon quantum dot (CQD)/silica nanoparticle (Si NP)/silk fibroin (SF) nanocomposite was synthesized, and two novel wound dressings, a BC-CQD/Si NP/SF nanocomposite and a PVA-CQD/Si NP/SF nanofiber, were prepared by Spray Printing and Electrospinning methods and successfully characterized. The water-uptake capacity of the BC-CQD/Si NP/SF nanocomposite has been optimized to evaluate its swelling behavior. To determine the antibacterial effects of the synthesized materials both MIC and Optical Density (OD) methods were performed, and the results imply that materials have high antibacterial activity and could successfully inhibit the growth of both S. aureus and E. coli bacteria. Cell toxicity, viability, and proliferation on NIH 3T3 fibroblast cells with the MTT assay have proved that the CQD/Si NP/SF nanocomposite not only has no toxicity but also can accelerate cell viability and proliferation. To assess the effect of the CQD/Si NP/SF nanocomposite on cell migration and in vitro wound healing scratch, a wound assay was performed, and the nanocomposite exhibits the ability to promote wound healing. The PVA-CQD/Si NP/SF nanofiber was used to investigate wound healing in an animal model. The results show that the PVA-CQD/Si NP/SF nanofiber effectively accelerates the skin and hair follicle regeneration. Therefore, the PVA-CQD/Si NP/SF nanofiber is a promising wound dressing for inhibiting bacterial growth and promoting skin wound repair and hair regeneration.

Silk Particles as Carriers of Therapeutic Molecules for Cancer Treatment

Although progress is observed in cancer treatment, this disease continues to be the second leading cause of death worldwide. The current understanding of cancer indicates that treating cancer should not be limited to killing cancer cells alone, but that the target is the complex tumor microenvironment (TME). The application of nanoparticle-based drug delivery systems (DDS) can not only target cancer cells and TME, but also simultaneously resolve the severe side effects of various cancer treatment approaches, leading to more effective, precise, and less invasive therapy. Nanoparticles based on proteins derived from silkworms' cocoons (like silk fibroin and sericins) and silk proteins from spiders (spidroins) are intensively explored not only in the oncology field. This natural-derived material offer biocompatibility, biodegradability, and simplicity of preparation methods. The protein-based material can be tailored for size, stability, drug loading/release kinetics, and functionalized with targeting ligands. This review summarizes the current status of drug delivery systems' development based on proteins derived from silk fibroin, sericins, and spidroins, which application is focused on systemic cancer treatment. The nanoparticles that deliver chemotherapeutics, nucleic acid-based therapeutics, natural-derived agents, therapeutic proteins or peptides, inorganic compounds, as well as photosensitive molecules, are introduced.

Novel Albumin Nanoparticle Enhanced the Anti-Insulin-Resistant-Hepatoma Activity of Metformin

Introduction

Metformin is an ideal candidate to treat the liver tumor with insulin resistance because of its good performance in the treatment of type 2 diabetes and the advantage in cancer therapy. We aim to develop a delivery system with higher efficiency than free drug.

Methods

Metformin-bovine serum albumin (met-BSA) nanoparticles (NPs) were prepared using the anti-solvent precipitation method with a stabilizer of BSA for particle growth. The therapeutic effect of the drug was tested by the insulin-resistant HepG2 cells and C57BL/6J mice at a glucose starvation condition. The interaction mechanism of the drug and the protein during the formation of the NPs was tested using a series of spectroscopy.

Results

Metformin and BSA formed nonporous and spherical particles of about 200 nm with proper lognormal distribution and thermostability. The cellular uptake, as well as the anti-liver cancer activities of met-BSA, was enhanced dramatically compared with the free drug. The thermodynamic studies suggested that the weak binding of metformin to BSA was governed by hydrogen bonds and van der Waals forces. Moreover, the results of synchronous, circular dichroism (CD) and three-dimensional fluorescence demonstrated that the BSA skeleton and chromophore microenvironments were changed in the presence of metformin.

Conclusion

Therefore, met-BSA has been proved as a simple yet effective therapeutic agent for cancer with insulin resistance, promising for future clinic translations in cancer treatment.

Hyaluronic Acid (HA)-Based Silk Fibroin/Zinc Oxide Core-Shell Electrospun Dressing for Burn Wound Management

Burn injuries represent a major life-threatening event that impacts the quality of life of patients, and places enormous demands on the global healthcare systems. This study introduces the fabrication and characterization of a novel wound dressing made of core-shell hyaluronic acid-silk fibroin/zinc oxide (ZO) nanofibers for treatment of burn injuries. The core-shell configuration enables loading ZO-an antibacterial agent-in the core of nanofibers, which in return improves the sustained release of the drug and maintains its bioactivity. Successful formation of core-shell nanofibers and loading of zinc oxide are confirmed by transmission electron microscopy, Fourier-transform infrared spectroscopy, and energy dispersive X-ray. The antibacterial activity of the dressings are examined against Escherichia coli and Staphylococcus aureus and it is shown that addition of ZO improves the antibacterial property of the dressing in a dose-dependent fashion. However, in vitro cytotoxicity studies show that high concentration of ZO (>3 wt%) is toxic to the cells. In vivo studies indicate that the wound dressings loaded with ZO (3 wt%) substantially improves the wound healing procedure and significantly reduces the inflammatory response at the wound site. Overall, the dressing introduced herein holds great promise for the management of burn injuries.

Silk fibroin hydrogels for potential applications in photodynamic therapy

In this study, we prepared translucid hydrogels with different concentrations of silk fibroin, extracted from raw silk fibers, and used them as a matrix to incorporate the photosensitizer 5-(4-aminophenyl)-10,15,20-tris-(4-sulphonatophenyl) porphyrin trisodium for application in photodynamic therapy (PDT). The hydrogels obtained were characterized by rheology, spectrophotometry, and scattering techniques to elucidate the factors involved in the formation of the hydrogel, and to characterize the behavior of silk fibroin (SF) after incorporating of the porphyrin to the matrix. The rheology results demonstrated that the SF hydrogels had a shear thinning behavior. In addition, we were able to verify that the structure of the material was able to be recovered over time after shear deformation. The encapsulation of porphyrins in hydrogels leads to the formation of self-assembled peptide nanostructures that prevent porphyrin aggregation, thereby greatly increasing the generation of singlet oxygen. Also, our findings suggest that porphyrin can diffuse out of the hydrogel and permeate the outer skin layers. This evidence suggests that SF hydrogels could be used as porphyrin encapsulation and as a drug carrier for the sustained release of photosensitizers for PDT.