Silk fibroin biomaterials for controlled release drug delivery

Polymeric functionalization of mesoporous silica nanoparticles: Biomedical insights

Mesoporous silica nanoparticles (MSNs) endowed with polymer coatings present a versatile platform, offering notable advantages such as targeted, pH-controlled, and stimuli-responsive drug delivery. Surface functionalization, particularly through amine and carboxyl modification, enhances their suitability for polymerization, thereby augmenting their versatility and applicability. This review delves into the diverse therapeutic realms benefiting from polymer-coated MSNs, including photodynamic therapy (PDT), photothermal therapy (PTT), chemotherapy, RNA delivery, wound healing, tissue engineering, food packaging, and neurodegenerative disorder treatment. The multifaceted potential of polymer-coated MSNs underscores their significance as a focal point for future research endeavors and clinical applications. A comprehensive analysis of various polymers and biopolymers, such as polydopamine, chitosan, polyethylene glycol, polycaprolactone, alginate, gelatin, albumin, and others, is conducted to elucidate their advantages, benefits, and utilization across biomedical disciplines. Furthermore, this review extends its scope beyond polymerization and biomedical applications to encompass topics such as surface functionalization, chemical modification of MSNs, recent patents in the MSN domain, and the toxicity associated with MSN polymerization. Additionally, a brief discourse on green polymers is also included in review, highlighting their potential for fostering a sustainable future.

Silk-gelatin hybrid hydrogel: a potential carrier for RNA therapeutics

RNA-based therapeutics have exhibited remarkable potential in targeting genetic factors for disease intervention, exemplified by recent mRNA vaccines for COVID-19. Nevertheless, the intrinsic instability of RNA and challenges related to its translational efficiency remain significant obstacles to the development of RNA as therapeutics. This study introduces an innovative RNA delivery approach using a silk fibroin (SF) and positively charged gelatin (Gel) hydrogel matrix to enhance RNA stability for controlled release. As a proof of concept, whole-cell RNA was incorporated into the hydrogel to enhance interactions with RNA molecules. Additionally, molecular modeling studies were conducted to explore the interactions between SF, collagen, chitosan (Chi), and the various RNA species including ribosomal RNAs (28S, 18S, 8.5S, and 5S rRNAs), transfer RNAs (tRNA-ALA, tRNA-GLN, and tRNA-Leu), as well as messenger RNAs (mRNA-GAPDH, mRNA-β actin, and mRNA-Nanog), shedding light on the RNA-polymer interaction and RNA stability; SF exhibits a more robust interaction with RNA compared to collagen/gel and chitosan. We confirmed the molecular interactions of SF and RNA by FTIR and Raman spectroscopy, which were further supported by AFM and contact angle measurement. This research introduces a novel RNA delivery platform and insights into biopolymer-RNA interactions, paving the way for tailored RNA delivery systems in therapeutics and biomedical applications.

Tunable thermal diffusivity of silk protein assemblies based on their structural control and photo-induced chemical cross-linking

Silk, which has excellent mechanical properties and is lightweight, serves as a structural material in natural systems. However, the structural and functional applications of silk in artificial systems have been limited due to the difficulty in controlling its properties. In this study, we demonstrate the tunable thermal diffusivity of silk-based assemblies (films) based on secondary structural control and subsequent cross-linking. We found that the thermal diffusivity of the silk film is increased by the formation of β-sheet structures and dityrosine between Tyr residues adjacent to the β-sheet structures. Our results demonstrate the applicability of silk proteins as material components for thermally conductive biopolymer-based materials.

Collagen/functionalized cellulose nanofibril composite aerogels with pH-responsive characteristics for drug delivery system

In this work, carboxylated and amination modified cellulose nanofibrils (CNFs) were fabricated via the TEMPO catalytic oxidation system and diethylenetriamine, and collagen composite aerogels were fabricated through a simple self-assembly pretreatment and directional freeze-drying technology. Morphology analysis showed that the collagen composite aerogels had distinct layered-oriented double network structures after the self-assembly pretreatment. The intermolecular interactions between the collagen fibrils and functionalized CNFs (fCNFs) on the structures and properties of the composite aerogels were also examined through various characterization techniques. Water contact angle tests demonstrated the pH-responsive characteristics of the collagen/fCNF composite aerogels. Using 5-fluorouracil as the model drug, the pH-response mechanism was revealed. These results indicated that the collagen/fCNF composite aerogels exhibited excellent pH-responsive drug release capacities. Therefore, these pH-responsive collagen composite aerogels might have potential applications in industrial production in the biomedical, drug delivery, and tissue engineering fields.

PEI-based functional materials: Fabrication techniques, properties, and biomedical applications

Cationic polymers have recently attracted considerable interest as research breakthroughs for various industrial and biomedical applications. They are particularly interesting due to their highly positive charges, acceptable physicochemical properties, and ability to undergo further modifications, making them attractive candidates for biomedical applications. Polyethyleneimines (PEIs), as the most extensively utilized polymers, are one of the valuable and prominent classes of polycations. Owing to their flexible polymeric chains, broad molecular weight (MW) distribution, and repetitive structural units, their customization for functional composites is more feasible. The specific beneficial attributes of PEIs could be introduced by purposeful functionalization or modification, long service life, biocompatibility, and distinct geometry. Therefore, PEIs have significant potential in biotechnology, medicine, and bioscience. In this review, we present the advances in PEI-based nanomaterials, their transfection efficiency, and their toxicity over the past few years. Furthermore, the potential and suitability of PEIs for various applications are highlighted and discussed in detail. This review aims to inspire readers to investigate innovative approaches for the design and development of next-generation PEI-based nanomaterials possessing cutting-edge functionalities and appealing characteristics.

Optimizing protein delivery rate from silk fibroin hydrogel using silk fibroin-mimetic peptides conjugation

Controlled release of proteins, such as growth factors, from biocompatible silk fibroin (SF) hydrogel is valuable for its use in tissue engineering, drug delivery, and other biological systems. To achieve this, we introduced silk fibroin-mimetic peptides (SFMPs) with the repeating unit (GAGAGS)n. Using green fluorescent protein (GFP) as a model protein, our results showed that SFMPs did not affect the GFP function when conjugated to it. The SFMP-GFP conjugates incorporated into SF hydrogel did not change the gelation time and allowed for controlled release of the GFP. By varying the length of SFMPs, we were able to modulate the release rate, with longer SFMPs resulting in a slower release, both in water at room temperature and PBS at 37 °C. Furthermore, the SF hydrogel with the SFMPs showed greater strength and stiffness. The increased β-sheet fraction of the SF hydrogel, as revealed by FTIR analysis, explained the gel properties and protein release behavior. Our results suggest that the SFMPs effectively control protein release from SF hydrogel, with the potential to enhance its mechanical stability. The ability to modulate release rates by varying the SFMP length will benefit personalized and controlled protein delivery in various systems.

Piezoelectric dressings for advanced wound healing

The treatment of chronic refractory wounds poses significant challenges and threats to both human society and the economy. Existing research studies demonstrate that electrical stimulation fosters cell proliferation and migration and promotes the production of cytokines that expedites the wound healing process. Presently, clinical settings utilize electrical stimulation devices for wound treatment, but these devices often present issues such as limited portability and the necessity for frequent recharging. A cutting-edge wound dressing employing the piezoelectric effect could transform mechanical energy into electrical energy, thereby providing continuous electrical stimulation and accelerating wound healing, effectively addressing these concerns. This review primarily reviews the selection of piezoelectric materials and their application in wound dressing design, offering a succinct overview of these materials and their underlying mechanisms. This study also provides a perspective on the current limitations of piezoelectric wound dressings and the future development of multifunctional dressings harnessing the piezoelectric effect.

Advanced Applications of Silk-Based Hydrogels for Tissue Engineering: A Short Review

Silk has been consistently popular throughout human history due to its enigmatic properties. Today, it continues to be widely utilized as a polymer, having first been introduced to the textile industry. Furthermore, the health sector has also integrated silk. The Bombyx mori silk fibroin (SF) holds the record for being the most sustainable, functional, biocompatible, and easily produced type among all available SF sources. SF is a biopolymer approved by the FDA due to its high biocompatibility. It is versatile and can be used in various fields, as it is non-toxic and has no allergenic effects. Additionally, it enhances cell adhesion, adaptation, and proliferation. The use of SF has increased due to the rapid advancement in tissue engineering. This review comprises an introduction to SF and an assessment of the relevant literature using various methods and techniques to enhance the tissue engineering of SF-based hydrogels. Consequently, the function of SF in skin tissue engineering, wound repair, bone tissue engineering, cartilage tissue engineering, and drug delivery systems is therefore analysed. The potential future applications of this functional biopolymer for biomedical engineering are also explored.

Design and fabrication of a magnetic nanobiocomposite based on flaxseed mucilage hydrogel and silk fibroin for biomedical and in-vitro hyperthermia applications

In this research work, a magnetic nanobiocomposite is designed and presented based on the extraction of flaxseed mucilage hydrogel, silk fibroin (SF), and Fe3O4 magnetic nanoparticles (Fe3O4 MNPs). The physiochemical features of magnetic flaxseed mucilage hydrogel/SF nanobiocomposite are evaluated by FT-IR, EDX, FE-SEM, TEM, XRD, VSM, and TG technical analyses. In addition to chemical characterization, given its natural-based composition, the in-vitro cytotoxicity and hemolysis assays are studied and the results are considerable. Following the use of highest concentration of magnetic flaxseed mucilage hydrogel/SF nanobiocomposite (1.75 mg/mL) and the cell viability percentage of two different cell lines including normal HEK293T cells (95.73%, 96.19%) and breast cancer BT549 cells (87.32%, 86.9%) in 2 and 3 days, it can be inferred that this magnetic nanobiocomposite is biocompatible with HEK293T cells and can inhibit the growth of BT549 cell lines. Besides, observing less than 5% of hemolytic effect can confirm its hemocompatibility. Furthermore, the high specific absorption rate value (107.8 W/g) at 200 kHz is generated by a determined concentration of this nanobiocomposite (1 mg/mL). According to these biological assays, this magnetic responsive cytocompatible composite can be contemplated as a high-potent substrate for further biomedical applications like magnetic hyperthermia treatment and tissue engineering.

Wearable patches for transdermal drug delivery

Transdermal drug delivery systems (TDDs) avoid gastrointestinal degradation and hepatic first-pass metabolism, providing good drug bioavailability and patient compliance. One emerging type of TDDs is the wearable patch worn on the skin surface to deliver medication through the skin. They can generally be grouped into passive and active types, depending on the properties of materials, design principles and integrated devices. This review describes the latest advancement in the development of wearable patches, focusing on the integration of stimulus-responsive materials and electronics. This development is deemed to provide a dosage, temporal, and spatial control of therapeutics delivery.

Electro-responsive silk fibroin microneedles for controlled release of insulin

To date, very limited work has been done on convenient and active control of insulin release. Herein, we report an electro-responsive insulin delivery system based on thiolated silk fibroin. The disulfide cross-linking points in TSF were reduced and broken to form sulfhydryl groups under electrification, which led to the increase of microneedle swelling degree and promoted insulin release. After power failure, the sulfhydryl group is oxidised to form disulfide bond crosslinking point again, resulting in the reduction of microneedle swelling degree and thus the reduction of release rate. The insulin loaded in the electro-responsive insulin delivery system showed good reversible electroresponsive release performance. The addition of graphene reduced the microneedle resistance and increased the drug release rate under current conditions. In vivo studies on type 1 diabetic mice show that electro-responsive insulin delivery system effectively controls the blood glucose before and after feeding by switching on and off the power supply, and this blood glucose control can be maintained within the safe range (100-200 mg/dL) for a long time (11h). Such electrically responsive delivery microneedles show potential for integration with glucose signal monitoring and are expected to build closed-loop insulin delivery systems.

Well-aligned three-dimensional silk fibroin protein scaffold for orientation regulation of cells

The similar characteristics of biomaterials to the extracellular matrix are essential for efficient tissue repair through dictating cell behaviors. But the scaffold fabrication with complex shapes and controlled alignment have proven to be a difficult task. Herein, a well-designed three-dimensional silk fibroin scaffold is fabricated through ice template technology. The effect of the silk fibroin protein concentration and the freezing temperature on the microstructure and mechanical properties of scaffolds are investigated systematically. Cells behavior mediated by the obtained silk fibroin scaffolds is detected. The results show that the protein concentration plays a vital role in microstructure and scaffold strength. A well-aligned scaffold can be obtained when silk fibroin solution is kept at 12 wt%, which holds the highest mechanical properties. The pore size can be further adjusted in the range of 5-80 µm by changing the freezing temperature from -60 to -196 °C. The well-oriented scaffold with the appropriate pore size of 10-20 µm has the best ability to guide cell alignment. The resulting scaffolds provide an excellent matrix to guide cells behaviors and have a potential application in tissue engineering.

Injectable anti-cancer drug loaded silk-based hydrogel for the prevention of cancer recurrence and post-lumpectomy tissue regeneration aiding triple-negative breast cancer therapy

A single system capable of delivering anticancer drugs and growth factors by a minimally invasive approach is in demand for effective treatment of triple-negative breast cancer (TNBC) after lumpectomy. Here, we showcase one such holistic system for TNBC therapy and its assessment via 3D in vitro lumpectomy model, a first of its kind. Firstly, Bombyx mori silk fibroin (BMSF) and Antheraea assamensis silk fibroin (AASF) blended hydrogels were prepared and biophysically characterized. Secondly, a 3D in vitro lumpectomy model was developed using MDA-MB-231 cell line to assess the efficacy of localized delivery of doxorubicin (dox) using injectable hydrogel system in terminating remaining breast cancer after lumpectomy. Additionally, we have also evaluated the adipose tissue regeneration in the lumpectomy region by delivering dexamethasone (dex) using injectable hydrogels. Rheological studies showed that the BMSF/AASF blended hydrogels exhibit viscoelasticity and injectability conducive for minimally invasive application. The developed hydrogels by virtue of its slow and sustained release of dox exerted cytotoxicity towards MDA-MB-231 cells assessed through in vitro studies. Further, dex loaded hydrogel supported adipogenic differentiation of adipose tissue derived stem cells (ADSCs), while the secreted factors were found to aid in vascularization and macrophage polarization. This was confirmed through in vitro angiogenic tube formation assay and macrophage polarization study respectively. The corroborated results vouch for potential application of this injectable hydrogels for localized anticancer drug delivery and aiding in breast reconstruction, post lumpectomy.

Silk fibroin-based biomaterials for disc tissue engineering

Low back pain is the major cause of disability worldwide, and intervertebral disc degeneration (IVDD) is one of the most important causes of low back pain. Currently, there is no method to treat IVDD that can reverse or regenerate intervertebral disc (IVD) tissue, but the recent development of disc tissue engineering (DTE) offers a new means of addressing these disadvantages. Among numerous biomaterials for tissue engineering, silk fibroin (SF) is widely used due to its easy availability and excellent physical/chemical properties. SF is usually used in combination with other materials to construct biological scaffolds or bioactive substance delivery systems, or it can be used alone. The present article first briefly outlines the anatomical and physiological features of IVD, the associated etiology and current treatment modalities of IVDD, and the current status of DTE. Then, it highlights the characteristics of SF biomaterials and their latest research advances in DTE and discusses the prospects and challenges in the application of SF in DTE, with a view to facilitating the clinical process of developing interventions related to IVD-derived low back pain caused by IVDD.

Natural Biopolymers as Smart Coating Materials of Mesoporous Silica Nanoparticles for Drug Delivery

In recent years, the functionalization of mesoporous silica nanoparticles (MSNs) with different types of responsive pore gatekeepers have shown great potential for the formulation of drug delivery systems (DDS) with minimal premature leakage and site-specific controlled release. New nanotechnological approaches have been developed with the objective of utilizing natural biopolymers as smart materials in drug delivery applications. Natural biopolymers are sensitive to various physicochemical and biological stimuli and are endowed with intrinsic biodegradability, biocompatibility, and low immunogenicity. Their use as biocompatible smart coatings has extensively been investigated in the last few years. This review summarizes the MSNs coating procedures with natural polysaccharides and protein-based biopolymers, focusing on their application as responsive materials to endogenous stimuli. Biopolymer-coated MSNs, which conjugate the nanocarrier features of mesoporous silica with the biocompatibility and controlled delivery provided by natural coatings, have shown promising therapeutic outcomes and the potential to emerge as valuable candidates for the selective treatment of various diseases.

Silk Fibroin Microneedles for Transdermal Drug Delivery: Where Do We Stand and How Far Can We Proceed?

Microneedles are a patient-friendly technique for delivering drugs to the site of action in place of traditional oral and injectable administration. Silk fibroin represents an interesting polymeric biomaterial because of its mechanical properties, thermal stability, biocompatibility and possibility of control via genetic engineering. This review focuses on the critical research progress of silk fibroin microneedles since their inception, analyzes in detail the structure and properties of silk fibroin, the types of silk fibroin microneedles, drug delivery applications and clinical trials, and summarizes the future development trend in this field. It also proposes the future research direction of silk fibroin microneedles, including increasing drug loading doses and enriching drug loading types as well as exploring silk fibroin microneedles with stimulation-responsive drug release functions. The safety and effectiveness of silk fibroin microneedles should be further verified in clinical trials at different stages.

Recent advancements in single dose slow-release devices for prophylactic vaccines

Single dose slow-release vaccines herald a new era in vaccine administration. An ideal device for slow-release vaccine delivery would be minimally invasive and self-administered, making these approaches an attractive alternative for mass vaccination programs, particularly during the time of a pandemic. In this review article, we discuss the latest advances in this field, specifically for prophylactic vaccines able to prevent infectious diseases. Recent studies have found that slow-release vaccines elicit better immune responses and often do not require cold chain transportation and storage, thus drastically reducing the cost, streamlining distribution, and improving efficacy. This promise has attracted significant attention, especially when poor patient compliance of the standard multidose vaccine regimes is considered. Single dose slow-release vaccines are the next generation of vaccine tools that could overcome most of the shortcomings of present vaccination programs and be the next platform technology to combat future pandemics. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Implantable Materials and Surgical Technologies > Nanomaterials and Implants Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

A hydrogel-fiber-hydrogel composite scaffold based on silk fibroin with the dual-delivery of oxygen and quercetin

Supplying sufficient oxygen within the scaffolds is one of the essential hindrances in tissue engineering that can be resolved by oxygen-generating biomaterials (OGBs). Two main issues related to OGBs are controlling oxygenation and reactive oxygen species (ROS). To address these concerns, we developed a composite scaffold entailing three layers (hydrogel-electrospun fibers-hydrogel) with antioxidant and antibacterial properties. The fibers, the middle layer, reinforced the composite structure, enhancing the mechanical strength from 4.27 ± 0.15 to 8.27 ± 0.25 kPa; also, this layer is made of calcium peroxide and silk fibroin (SF) through electrospinning, which enables oxygen delivery. The first and third layers are physical SF hydrogels to control oxygen release, containing quercetin (Q), a nonenzymatic antioxidant. This composite scaffold resulted in almost more than 40 mmHg of oxygen release for at least 13 days, and compared with similar studies is in a high range. Here, Q was used for the first time for an OGB to scavenge the possible ROS. Q delivery not only led to antioxidant activity but also stabilized oxygen release and enhanced cell viability. Based on the given results, this composite scaffold can be introduced as a safe and controllable oxygen supplier, which is promising for tissue engineering applications, particularly for bone.

Silk fibroin microgels as a platform for cell microencapsulation

Cell microencapsulation has been utilized for years as a means of cell shielding from the external environment while facilitating the transport of gases, general metabolites, and secretory bioactive molecules at once. In this light, hydrogels may support the structural integrity and functionality of encapsulated biologics whereas ensuring cell viability and function and releasing potential therapeutic factors once in situ. In this work, we describe a straightforward strategy to fabricate silk fibroin (SF) microgels (µgels) and encapsulate cells into them. SF µgels (size ≈ 200 µm) were obtained through ultrasonication-induced gelation of SF in a water-oil emulsion phase. A thorough physicochemical (SEM analysis, and FT-IR) and mechanical (microindentation tests) characterization of SF µgels were carried out to assess their nanostructure, porosity, and stiffness. SF µgels were used to encapsulate and culture L929 and primary myoblasts. Interestingly, SF µgels showed a selective release of relatively small proteins (e.g., VEGF, molecular weight, M_W = 40 kDa) by the encapsulated primary myoblasts, while bigger (macro)molecules (M_W = 160 kDa) were hampered to diffusing through the µgels. This article provided the groundwork to expand the use of SF hydrogels into a versatile platform for encapsulating relevant cells able to release paracrine factors potentially regulating tissue and/or organ functions, thus promoting their regeneration.

Loading and Release of Quercetin from Contact-Drawn Polyvinyl Alcohol Fiber Scaffolds

Polymeric drug releasing systems have numerous applications for the treatment of chronic diseases and traumatic injuries. In this study, a simple, cost-effective, and scalable method for dry spinning of crosslinked polyvinyl alcohol (PVA) fibers is presented. This method utilizes an entangled solution of PVA to form liquid bridges that are drawn into rapidly drying fibers through extensional flow. The fibers are crosslinked by a one-pot reaction in which glyoxal is introduced to the PVA solution prior to contact drawing. Failure analysis of fiber formation is used to understand the interplay of polymer concentration, glyoxal concentration, and crosslinking time to identify appropriate formulations for the production of glyoxal-crosslinked PVA fibers. The small molecule quercetin (an anti-inflammatory plant flavonoid) can be added to the one-pot reaction and is shown to be incorporated into the fibers in a concentration-dependent manner. Upon rehydration in an aqueous medium, the glyoxal-crosslinked PVA fiber scaffolds retain their morphology and slowly degrade, as measured over the course of 10 days. As the scaffolds degrade, they release the loaded quercetin, reaching a cumulative release of 56 ± 6% of the loaded drug after 10 days. The bioactivity of the released quercetin is verified by combining quercetin-loaded fibers with contact-drawn polyethylene oxide-type I collagen (PEO-Col) fibers and monitoring the growth of PC12 cells on the fibers. PC12 cells readily attach to the PEO-Col fibers and display increased nerve growth factor-induced elongation and neurite formation in the presence of quercetin-loaded PVA fibers relative to substrates formed from only PEO-Col fibers or PEO-Col and PVA fibers without quercetin.

Silk Fibroin as an Efficient Biomaterial for Drug Delivery, Gene Therapy, and Wound Healing

Silk fibroin (SF), an organic material obtained from the cocoons of a silkworm Bombyx mori, is used in several applications and has a proven track record in biomedicine owing to its superior compatibility with the human body, superb mechanical characteristics, and its controllable propensity to decay. Due to its robust biocompatibility, less immunogenic, non-toxic, non-carcinogenic, and biodegradable properties, it has been widely used in biological and biomedical fields, including wound healing. The key strategies for building diverse SF-based drug delivery systems are discussed in this review, as well as the most recent ways for developing functionalized SF for controlled or redirected medicines, gene therapy, and wound healing. Understanding the features of SF and the various ways to manipulate its physicochemical and mechanical properties enables the development of more effective drug delivery devices. Drugs are encapsulated in SF-based drug delivery systems to extend their shelf life and control their release, allowing them to travel further across the bloodstream and thus extend their range of operation. Furthermore, due to their tunable properties, SF-based drug delivery systems open up new possibilities for drug delivery, gene therapy, and wound healing.

Mussel-Inspired Hydrogels for Fluoride Delivery and Caries Prevention

Fluoride agents hold promise for the repair and prevention of caries lesions, but their interaction with enamel is often hampered and diminished because of the dynamic wet environment in the oral cavity, which affects the efficacy of fluoride delivery and limits treatment success. We herein developed a mussel-inspired wet adhesive fluoride system (denoted TS@NaF) fabricated by the self-assembly of tannic acid (TA), silk fibroin (SF), and sodium fluoride (NaF). TS@NaF demonstrated remarkable biological stability and biocompatibility, showed reliable wet adhesion, released fluoride ions (F−) topically, and induced significant deposition of calcium fluoride (CaF2) onto enamel in vitro. Furthermore, TS@NaF provided an anticaries effect in vitro and induced a detectable increase in enamel mineral density. Advanced fluoride-releasing bioadhesives are therefore promising candidates for caries prevention and highlight the great potential of mussel-inspired dental materials in clinical applications.

Antibiotic-Loaded Hyperbranched Polyester Embedded into Peptide-Enriched Silk Fibroin for the Treatment of Orthopedic or Dental Infections

The development of innovative osteoconductive matrices, which are enriched with antibiotic delivery nanosystems, has the invaluable potential to achieve both local contaminant eradication and the osseointegration of implanted devices. With the aim of producing safe, bioactive materials that have osteoconductive and antibacterial properties, novel, antibiotic-loaded, functionalized nanoparticles (AFN)-based on carboxylic acid functionalized hyperbranched aliphatic polyester (CHAP) that can be integrated into peptide-enriched silk fibroin (PSF) matrices with osteoconductive properties-were successfully synthesized. The obtained AFNPSF sponges were first physico-chemically characterized and then tested in vitro against eukaryotic cells and bacteria involved in orthopedic or oral infections. The biocompatibility and microbiological tests confirmed the promising characteristics of the AFN-PSF products for both orthopedic and dental applications. These preliminary results encourage the establishment of AFN-PSF-based preventative strategies in the fight against implant-related infections.

Use of Bombyx mori silk fibroin in tissue engineering: From cocoons to medical devices, challenges, and future perspectives

Silk fibroin has become a prominent material in tissue engineering (TE) over the last 20 years with almost 10,000 published works spanning in all the TE applications, from skeleton to neuronal regeneration. Fibroin is an extremely versatile biopolymer that, due to its ease of processing, has enabled the development of an entire plethora of materials whose properties and architectures can be tailored to suit target applications. Although the research and development of fibroin TE materials and devices is mature, apart from sutures, only a few medical products made of fibroin are used in the clinical routines. <40 clinical trials of Bombyx mori silk-related products have been reported by the FDA and few of them resulted in a commercialized device. In this review, after explaining the structure and properties of silk fibroin, we provide an overview of both fibroin constructs existing in the literature and fibroin devices used in clinic. Through the comparison of these two categories, we identified the burning issues faced by fibroin products during their translation to the market. Two main aspects will be considered. The first is the standardization of production processes, which leads both to the standardization of the characteristics of the issued device and the correct assessment of its failure. The second is the FDA regulations, which allow new devices to be marketed through the 510(k) clearance by demonstrating their equivalence to a commercialized medical product. The history of some fibroin medical devices will be taken as a case study. Finally, we will outline a roadmap outlining what actions we believe are needed to bring fibroin products to the market.

Silk Fibroin Hydrogel Reinforced With Magnetic Nanoparticles as an Intelligent Drug Delivery System for Sustained Drug Release

Due to the well-known biocompatibility, tunable biodegradability, and mechanical properties, silk fibroin hydrogel is an exciting material for localized drug delivery systems to decrease the therapy cost, decrease the negative side effects, and increase the efficiency of chemotherapy. However, the lack of remote stimuli response and active drug release behavior has yet to be analyzed comparatively. In this study, we developed magnetic silk fibroin (SF) hydrogel samples through the facile blending method, loaded with doxorubicin hydrochloride (DOX) and incorporated with different concentrations of iron oxide nanoparticles (IONPs), to investigate the presumable ability of controlled and sustained drug release under the various external magnetic field (EMF). The morphology and rheological properties of SF hydrogel and magnetic SF hydrogel were compared through FESEM images and rheometer analysis. Here, we demonstrated that adding magnetic nanoparticles (MNPs) into SFH decreased the complex viscosity and provided a denser porosity with a bigger pore size matrix structure, which allowed the drug to be released faster in the absence of an EMF. Release kinetic studies show that magnetic SF hydrogel could achieve controlled release of DOX in the presence of an EMF. Furthermore, the drug release from magnetic SF hydrogel decreased in the presence of a static magnetic field (SMF) and an alternating magnetic field (AMF), and the release rate decreased even more with the higher MNPs concentration and magnetic field strength. Subsequently, Wilms’ tumor and human fibroblast cells were cultured with almost the same concentration of DOX released in different periods, and cell viability was investigated using MTT assay. MTT results indicated that the Wilms’ tumor cells were more resistant to DOX than the human fibroblasts, and the IC50 values were calculated at 1.82 ± 0.001 and 2.73 ± 0.004 (μg/ml) for human fibroblasts and Wilms’ tumor cells, respectively. Wilms’ tumor cells showed drug resistance in a higher DOX concentration, indicating the importance of controlled drug delivery. These findings suggest that the developed magnetic SFH loaded with DOX holds excellent potential for intelligent drug delivery systems with noninvasive injection and remotely controlled abilities.

Tissue Adhesives in Reconstructive and Aesthetic Surgery—Application of Silk Fibroin-Based Biomaterials

Tissue adhesives have been successfully used in various kind of surgeries such as oral and maxillofacial surgery for some time. They serve as a substitute for suturing of tissues and shorten treatment time. Besides synthetic-based adhesives, a number of biological-based formulations are finding their way into research and clinical application. In natural adhesives, proteins play a crucial role, mediating adhesion and cohesion at the same time. Silk fibroin, as a natural biomaterial, represents an interesting alternative to conventional medical adhesives. Here, the most commonly used bioadhesives as well as the potential of silk fibroin as natural adhesives will be discussed.

Self-Assembling Imageable Silk Hydrogels for the Focal Treatment of Osteosarcoma

Background: The standard treatment for osteosarcoma comprises complete surgical resection and neoadjuvant chemotherapy, which may cause serious side effects and partial or total limb loss. Therefore, to avoid the disadvantages of traditional treatment, we developed self-assembling imageable silk hydrogels for osteosarcoma.

Methods: We analysed whether iodine induced apoptosis in MG-63 and Saos-2 cells by using CCK-8 and flow cytometry assays and transmission electron microscopy. Western blotting was used to analyse the pathway of iodine-induced apoptosis in osteosarcoma cells. PEG400, silk fibroin solution, polyvinylpyrrolidone iodine (PVP-I), and meglumine diatrizoate (MD) were mixed to produce an imageable hydrogel. A nude mouse model of osteosarcoma was established, and the hydrogel was injected locally into the interior of the osteosarcoma with X-ray guidance. The therapeutic effect and biosafety of the hydrogel were evaluated.

Results: Iodine treatment at 18 and 20 µM for 12 h resulted in cell survival rate reduced to 50 ± 2.1% and 50.5 ± 2.7% for MG-63 and Sao-2 cells, respectively (p < 0.01). The proportion of apoptotic cells was significantly higher in the iodine-treatment group than in the control group (p < 0.05), and apoptotic bodies were observed by transmission electron microscopy. Iodine could regulate the death receptor pathway and induce MG-63 and Saos-2 cell apoptosis. The hydrogels were simple to assemble, and gels could be formed within 38 min. A force of less than 50 N was required to inject the gels with a syringe. The hydrogels were readily loaded and led to sustained iodine release over 1 week. The osteosarcoma volume in the PEG-iodine-silk/MD hydrogel group was significantly smaller than that in the other three groups (p < 0.001). Caspase-3 and poly (ADP-ribose) polymerase (PARP) expression levels were significantly higher in the PEG-iodine-silk/MD hydrogel group than in the other three groups (p < 0.001). Haematoxylin and eosin (H&E) staining showed no abnormalities in the heart, liver, spleen, lung, kidney, pancreas or thyroid in any group.

Conclusions: Self-assembling imageable silk hydrogels could be injected locally into osteosarcoma tissues with X-ray assistance. With the advantages of good biosafety, low systemic toxicity and minimal invasiveness, self-assembling imageable silk hydrogels provide a promising approach for improving the locoregional control of osteosarcoma.

Photothermal effect of indocyanine green modified scaffold inhibits oral squamous cell carcinoma and promotes wound healing

As the most prevalent malignant tumor of the oral and maxillofacial regions, squamous cell carcinoma (SCC) has relatively high recurrence and low survival rates. Currently, the most common treatment strategies are surgery and chemoradiotherapy. However, incomplete removal of the tumor can allow residual tumor cells to regrow and metastasis, resulting in treatment failure. Although postoperative adjuvant radiotherapy or chemotherapy can reduce recurrence, serious adverse reactions significantly compromise patients' quality of life. Large soft tissue defects after surgery are also difficult to heal. Therefore, therapies that eliminate residual tumor cells and promote tissue regeneration post-surgery are urgently needed. Indocyanine green (ICG) can convert absorbed light into heat to ablate tumor cells. Three-dimensional (3D) scaffolds are efficient drug carriers and support cell migration and proliferation. Here, we fabricated collagen/silk fibroin encapsulated ICG (I-CS) scaffolds by combining 3D printing with freeze-drying methods. The I-CS scaffolds delayed ICG decomposition and clearance, allowing the scaffolds to be used repeatedly for photothermal therapy (PTT). With the laser positioned at 4 cm from the 1.0 I-CS scaffold and irradiation for 10 min (1.0 W/cm²), temperatures above 50 °C were achieved, which effectively killed SCC-25 cells in vitro and suppressed tumor growth in vivo. Moreover, the I-CS scaffolds supported attachment and proliferation of rat buccal mucosa fibroblasts (RBMFs) and promoted the repair of buccal mucosal wounds in rats. These results suggested that I-CS scaffolds may be useful in preventing local recurrence and support regeneration of large soft tissue defects after oral SCC surgery.

Updates in immunocompatibility of biomaterials: applications for regenerative medicine

INTRODUCTION

Biomaterials, either metallic, ceramic, or polymeric, can be used in medicine as a part of the implants, dialysis membranes, bone scaffolds, or components of artificial organs. Polymeric biomaterials cover a vast range of biomedical applications. The biocompatibility and immunocompatibility of polymeric materials are of fundamental importance for their possible therapeutic uses, as the immune system can intervene in the materials' performance. Therefore, based on application, different routes can be utilized for immunoregulation.

AREAS COVERED

As different biomaterials can be modulated by different strategies, this study aims to summarize and evaluate the available methods for the immunocompatibility enhancement of more common polymeric biomaterials based on their nature. Different strategies such as surface modification, physical characterization, and drug incorporation are investigated for the immunomodulation of nanoparticles, hydrogels, sponges, and nanofibers.

EXPERT OPINION

Recently, strategies for triggering appropriate immune responses by functional biomaterials have been highlighted. As most strategies correspond to the physical and surface properties of biomaterials, specific modulation can be conducted for each biomaterial system. Besides, different applications require different modulations of the immune system. In the future, the selection of novel materials and immune regulators can play a role in tuning the immune system for regenerative medicine.

Challenges in delivering therapeutic peptides and proteins: A silk-based solution

Peptide- and protein-based therapeutics have drawn significant attention over the past few decades for the treatment of infectious diseases, genetic disorders, oncology, and many other clinical needs. Yet, protecting peptide- and protein-based drugs from degradation and denaturation during processing, storage and delivery remain significant challenges. In this review, we introduce the properties of peptide- and protein-based drugs and the challenges associated with their stability and delivery. Then, we discuss delivery strategies using synthetic polymers and their advantages and limitations. This is followed by a focus on silk protein-based materials for peptide/protein drug processing, storage, and delivery, as a path to overcome stability and delivery challenges with current systems.

Animal protein-plant protein composite nanospheres for dual-drug loading and synergistic cancer therapy

The co-delivery of multiple drugs using one drug carrier is a viable strategy to optimize drug dosage and reduce the side effects in chemotherapy. Herein, a hydrophilic animal protein (silk fibroin) and a hydrophobic plant protein (zein) were selected for preparing a composite drug carrier. Adapting our previously developed method for the preparation of regenerated silk fibroin (RSF) nanospheres, we prepared RSF/zein nanospheres that displayed an interesting structure including a single central hole. The particle size of the RSF/zein nanospheres was regulated from 150 to 460 nm by varying the preparation conditions, implying that such a drug carrier is suitable for both intravenous administration and lymphatic chemotherapy. Two anti-cancer drugs with different target sites, paclitaxel (PTX) and curcumin (CUR), were selected for the preparation of dual-drug-loaded CUR/PTX@RSF/zein nanospheres. Both drugs achieved a high loading capacity in the RSF/zein nanospheres, i.e., 8.2% for PTX and 12.1% for CUR. Subsequently, the encapsulated PTX and CUR were released from the RSF/zein nanospheres in a sustained manner for at least 7 days. Importantly, these dual-drug-loaded RSF/zein nanospheres exhibited a considerable synergistic therapeutic effect, showing more efficient suppression of in vitro cancer cell growth than free PTX or CUR, a combination of free PTX and CUR, or single-drug-loaded nanospheres. Therefore, the CUR/PTX@RSF/zein nanospheres developed in this study hold great potential for combination chemotherapy in future clinical applications.

Feeding Alginate-Coated Liquid Metal Nanodroplets to Silkworms for Highly Stretchable Silk Fibers

In this study, we fed the larval of Bombyx mori silkworms with nanodroplets of liquid metal (LM) coated with microgels of marine polysaccharides to obtain stretchable silk. Alginate-coated liquid metal nanodroplets (LM@NaAlg) were prepared with significant chemical stability and biocompatibility. This study demonstrates how the fed LM@NaAlg acts on the as-spun silk fiber. We also conducted a series of characterizations and steered molecular dynamics simulations, which showed that the LM@NaAlg additions impede the conformation transition of silk fibroins from the random coil and α-helix to the β-sheet by the formation of hydrogen bonds between LM@NaAlg and the silk fibroins, thus enhancing the elongation at the breakpoints in addition to the tensile properties. The intrinsically highly stretchable silk showed outstanding mechanical properties compared with regular silk due to its 814 MPa breaking strength and a breaking elongation of up to 70%—the highest reported performance so far. We expect that the proposed method can expand the fabrication of multi-functional silks.

Silk Fibroin-Based Therapeutics for Impaired Wound Healing

Impaired wound healing can lead to local hypoxia or tissue necrosis and ultimately result in amputation or even death. Various factors can influence the wound healing environment, including bacterial or fungal infections, different disease states, desiccation, edema, and even systemic viral infections such as COVID-19. Silk fibroin, the fibrous structural-protein component in silk, has emerged as a promising treatment for these impaired processes by promoting functional tissue regeneration. Silk fibroin’s dynamic properties allow for customizable nanoarchitectures, which can be tailored for effectively treating several wound healing impairments. Different forms of silk fibroin include nanoparticles, biosensors, tissue scaffolds, wound dressings, and novel drug-delivery systems. Silk fibroin can be combined with other biomaterials, such as chitosan or microRNA-bound cerium oxide nanoparticles (CNP), to have a synergistic effect on improving impaired wound healing. This review focuses on the different applications of silk-fibroin-based nanotechnology in improving the wound healing process; here we discuss silk fibroin as a tissue scaffold, topical solution, biosensor, and nanoparticle.

Photoacoustic Carbon Nanotubes Embedded Silk Scaffolds for Neural Stimulation and Regeneration

Neural interfaces using biocompatible scaffolds provide crucial properties, such as cell adhesion, structural support, and mass transport, for the functional repair of nerve injuries and neurodegenerative diseases. Neural stimulation has also been found to be effective in promoting neural regeneration. This work provides a generalized strategy to integrate photoacoustic (PA) neural stimulation into hydrogel scaffolds using a nanocomposite hydrogel approach. Specifically, polyethylene glycol (PEG)-functionalized carbon nanotubes (CNT), highly efficient photoacoustic agents, are embedded into silk fibroin to form biocompatible and soft photoacoustic materials. We show that these photoacoustic functional scaffolds enable nongenetic activation of neurons with a spatial precision defined by the area of light illumination, promoting neuron regeneration. These CNT/silk scaffolds offered reliable and repeatable photoacoustic neural stimulation, and 94% of photoacoustic-stimulated neurons exhibit a fluorescence change larger than 10% in calcium imaging in the light-illuminated area. The on-demand photoacoustic stimulation increased neurite outgrowth by 1.74-fold in a rat dorsal root ganglion model, when compared to the unstimulated group. We also confirmed that promoted neurite outgrowth by photoacoustic stimulation is associated with an increased concentration of neurotrophic factor (BDNF). As a multifunctional neural scaffold, CNT/silk scaffolds demonstrated nongenetic PA neural stimulation functions and promoted neurite outgrowth, providing an additional method for nonpharmacological neural regeneration.

Nanofiber Systems as Herbal Bioactive Compounds Carriers: Current Applications in Healthcare

Nanofibers have emerged as a potential novel platform due to their physicochemical properties for healthcare applications. Nanofibers’ advantages rely on their high specific surface-area-to-volume and highly porous mesh. Their peculiar assembly allows cell accommodation, nutrient infiltration, gas exchange, waste excretion, high drug release rate, and stable structure. This review provided comprehensive information on the design and development of natural-based polymer nanofibers with the incorporation of herbal medicines for the treatment of common diseases and their in vivo studies. Natural and synthetic polymers have been widely used for the fabrication of nanofibers capable of mimicking extracellular matrix structure. Among them, natural polymers are preferred because of their biocompatibility, biodegradability, and similarity with extracellular matrix proteins. Herbal bioactive compounds from natural extracts have raised special interest due to their prominent beneficial properties in healthcare. Nanofiber properties allow these systems to serve as bioactive compound carriers to generate functional matrices with antimicrobial, anti-inflammatory, antioxidant, antiseptic, anti-viral, and other properties which have been studied in vitro and in vivo, mostly to prove their wound healing capacity and anti-inflammation properties.

Silk Embolic Material for Catheter-Directed Endovascular Drug Delivery

Embolization is a catheter-based minimally invasive procedure that deliberately occludes diseased blood vessels for treatment purposes. A novel silk-based embolic material (SEM) that is developed and optimized to provide tandem integration of both embolization and the delivery of therapeutics is reported. Natural silk is processed into fibroin proteins of varying lengths and is combined with charged nanoclay particles to allow visibility and injectability using clinical catheters as small as 600 μm in diameter at lengths >100 cm. SEMs loaded with fluorochrome labeled bovine albumin and Nivolumab, which is among the most used immunotherapy drugs worldwide, demonstrate a sustained release profile in vitro over 28 days. In a porcine renal survival model, SEMs with labeled albumin and Nivolumab successfully embolize porcine arteries without recanalization and lead to the delivery of both albumin and Nivolumab into the interstitial space of the renal cortex. Mechanistically, it is shown that tissue delivery is most optimal when the internal elastic membrane of the embolized artery is disrupted. SEM is a potential next-generation multifunctional embolic agent that can achieve embolization and deliver a wide range of therapeutics to treat vascular diseases including tumors.

Fiber-Based Biopolymer Processing as a Route toward Sustainability

Some of the most abundant biomass on earth is sequestered in fibrous biopolymers like cellulose, chitin, and silk. These types of natural materials offer unique and striking mechanical and functional features that have driven strong interest in their utility for a range of applications, while also matching environmental sustainability needs. However, these material systems are challenging to process in cost-competitive ways to compete with synthetic plastics due to the limited options for thermal processing. This results in the dominance of solution-based processing for fibrous biopolymers, which presents challenges for scaling, cost, and consistency in outcomes. However, new opportunities to utilize thermal processing with these types of biopolymers, as well as fibrillation approaches, can drive renewed opportunities to bridge this gap between synthetic plastic processing and fibrous biopolymers, while also holding sustainability goals as critical to long-term successful outcomes.

Silk fibroin double-layer microneedles for the encapsulation and controlled release of triptorelin

A double-layer silk fibroin microneedles (SF-MNs) was proposed for the transdermal delivery of triptorelin. Two-step pouring and centrifugation were employed to prepare SF-MNs. Triptorelin was wrapped in MNs in the form of microcrystals with a size of ∼1 μm. β-sheet nanocrystals (the secondary structure of silk fibroin) were adjusted in content by methanol-vapor treatment to manipulate the characteristics of SF-MNs prepared with two concentrations of silk fibroin. The mechanical strength of MNs was measured and analyzed in proportion to the β-sheet content. The triptorelin in MNs could be released sustainedly in phosphate-buffered saline for 168 h, and the release amount decreased with increasing β-sheet content. The Ritger-Peppas equation was employed to fit the release data. A linear decreasing relationship was observed between the diffusion coefficient and increased β-sheet content. After administration to rats, SF-MNs exhibited long-term testosterone inhibition and maintained castration levels for ≥7 d. Manipulable mechanical properties and release behavior combined with biocompatibility and biodegradability render SF-MNs as viable long-term transdermal delivery devices for triptorelin.

Pectin-cellulose hydrogel, silk fibroin and magnesium hydroxide nanoparticles hybrid nanocomposites for biomedical applications

Natural polymers are at the center of materials development for biomedical and biotechnological applications based on their biocompatibility, low-toxicity and biodegradability. In this study, a novel nanobiocomposite based on cross-linked pectin-cellulose hydrogel, silk fibroin, and Mg(OH)₂ nanoparticles was designed and synthesized. After extensive physical-chemical characterization, the biological response of pectin-cellulose/silk fibroin/Mg(OH)₂ nanobiocomposite scaffolds was evaluated by cell viability, red blood cells hemolytic and anti-biofilm assays. After 3 days and 7 days, the cell viability of this nanobiocomposite scaffold was 65.5% and 60.5% respectively. The hemolytic effect was below 20%. Furthermore, the presence of silk fibroin and Mg(OH)₂ nanoparticles allowed to enhance the anti-biofilm activity, inhibiting the P. aeruginosa biofilm formation.

Biomimetic Inorganic Nanoparticle-Loaded Silk Fibroin-Based Coating with Enhanced Antibacterial and Osteogenic Abilities

Poor osseointegration and infection are the main reasons leading to the failure of hard tissue implants; especially, in recent years, the failure rate has been increasing every year owing to the continuously increasing conditions such as injury, trauma, diseases, or infections. Therefore, the development of a biomimetic surface coating of bone tissues with antibacterial function is an effective means to improve bone healing and inhibit bacterial infection. Mimicking the natural bone, in this study, we have designed a silk fibroin (collagen-like structure)-based coating inlaid with nanohydroxyapatite (nHA) and silver nanoparticles (AgNPs) for promoting antibacterial ability and osteogenesis, especially focusing on the bone mimetic structure for enhancing bone health. Observing the morphology and size of the composite nanoparticles by transmission electron microscope (TEM), nHA provided nucleation sites for the formation of AgNPs, forming an nHA/AgNP complex with a size of about 100-200 nm. Characterization of the nHA/Ag-loaded silk fibroin biomimetic coating showed an increased surface roughness with good density and compact performances. The silk fibroin-based coating loaded with uniformly distributed AgNPs and nHA could effectively inhibit the adhesion of Staphylococcus aureus on the surface and, at the same time, quickly kill planktonic bacteria, indicating their good antibacterial ability. In vitro cell experiments revealed that the biomimetic silk fibroin-based coating was beneficial to the adhesion, spreading, and proliferation of osteoblasts (MC3T3-E1). In addition, by characterizing LDH and ROS, it was found that the nHA/Ag complex could significantly reduce the cytotoxicity of AgNPs, and the osteoblasts on the coating surface maintained the structure intact.

Human Umbilical Cord Mesenchymal Stem Cell Derived Exosomes Delivered Using Silk Fibroin and Sericin Composite Hydrogel Promote Wound Healing

Recent studies have shown that the hydrogels formed by composite biomaterials are better choice than hydrogels formed by single biomaterial for tissue repair. We explored the feasibility of the composite hydrogel formed by silk fibroin (SF) and silk sericin (SS) in tissue repair for the excellent mechanical properties of SF, and cell adhesion and biocompatible properties of SS. In our study, the SF SS hydrogel was formed by SF and SS protein with separate extraction method (LiBr dissolution for SF and hot alkaline water dissolution for SS), while SF-SS hydrogel was formed by SF and SS protein using simultaneous extraction method (LiBr dissolution for SF and SS protein). The effects of the two composite hydrogels on the release of inflammatory cytokines from macrophages and the wound were analyzed. Moreover, two hydrogels were used to encapsulate and deliver human umbilical cord mesenchymal stem cell derived exosomes (UMSC-Exo). Both SF SS and SF-SS hydrogels promoted wound healing, angiogenesis, and reduced inflammation and TNF-α secretion by macrophages. These beneficial effects were more significant in the experimental group treated by UMSC-Exo encapsulated in SF-SS hydrogel. Our study found that SF-SS hydrogel could be used as an excellent alternative to deliver exosomes for tissue repair.

CD4+ CD8αα+ T cells in the gastric epithelium mediate chronic inflammation induced by Helicobacter felis

CD4⁺ CD8αα⁺ double-positive intraepithelial T lymphocytes (DP T cells), a newly characterized subset of intraepithelial T cells, are reported to contribute to local immunosuppression. However, the presence of DP T cells in Helicobacter. pylori -induced gastritis and their relationship with disease prognosis has yet to be elucidated. In this study, a chronic gastritis model was established by infecting mice with Helicobacter felis. Gastric-infiltrating lymphocytes were isolated from these mice and analyzed by flow cytometry. The frequency of DP T cells in H. felis-induced gastritis mice was higher than that in uninfected mice. The gastric DP T cells were derived from lamina propria cells but were predominantly distributed in the gastric epithelial layer. These gastric DP T cells also exhibited anti-inflammatory functions, and they inhibited the maturation of dendritic cells and proliferation of CD4⁺ T lymphocytes in vitro. Elimination of DP T cells simultaneously resulted in severe gastritis and a reduction of H. felis load in vivo. Finally, vaccine mixed with different adjuvants was used to explore the relationship between vaccine efficacy and DP cells. Silk fibroin as the vaccine delivery system enhanced vaccine efficacy by reducing the number of DP T cells. This study demonstrated that DP T cells perform an immunosuppressive role in Helicobacter felis-induced gastritis, and consequently, DP T cells may affect disease prognosis and vaccine efficacy.

Bioinspired silk fibroin nano-delivery systems protect against 5-FU induced gastrointestinal mucositis in a mouse model and display antitumor effects on HT-29 colorectal cancer cells in vitro

Colorectal cancer (CRC), is the second cause of cancer-related deaths worldwide is one of the most prevalent types of cancers. Conventional treatment continues to rely on surgery, chemotherapy, and radiotherapy, but for advanced cases, adjuvant chemotherapy remains the main approach for improving surgical outcomes and lower the disease recurrence probability. Chemotherapy-induced gastrointestinal (GI) toxicity is the main dose-limiting factor for many chemotherapeutic regimens, including 5-FU, and one of the biggest oncological challenges. Up to 40% of the patients receiving 5-FU get mucositis, 10-15% of which develop severe symptoms. In this context, our study aimed to develop a bioinspired nanosized drug delivery system as a strategy to reduce 5-FU associated side effects, such as GI mucositis. To this end, SF-based nanoparticles were prepared and characterized in terms of size and morphology, as well as in terms of in vitro antitumoral activity on a biomimetic colorectal cancer model by investigation of apoptosis, DNA fragmentation, and release of reactive oxygen species. Additionally, the capacity of the SF-based nanocarriers to offer intestinal protection against 5-FU-induced GI mucositis was evaluated in vivo using a mouse model that mimics the chemotherapy-associated gut mucositis occurring in colorectal cancer. Our studies show that silk fibroin nanoparticles efficiently deliver 5-FU to tumor cells in vitro while protecting against drug-induced GI mucositis in a mouse model.

Sugar Functionalization of Silks with Pathway-Controlled Substitution and Properties

Silk biomaterials are important for applications in biomedical fields due to their outstanding mechanical properties, biocompatibility, and tunable biodegradation. Chemical functionalization of silk by various chemistries can be leveraged to enhance and tune these features and enable the expansion of silk-based biomaterials into additional fields. Sugars are particularly relevant for intracellular communication, signal transduction events, as well as in hydrated extracellular matrices such as in cartilage, vitreous, and brain tissues. Multiple reaction pathways are demonstrated (carboxylation of serines followed by carbodiimide coupling with glucosamine, carboxylation of tyrosines followed by carbodiimide coupling with glucosamine; direct carbodiimide coupling of the inherent carboxylic acids of silk (aspartic and glutamic acid) with glucosamine) for the covalent conjugation of glucosamine onto silk with characterization by proton nuclear magnetic resonance (1 H-NMR), liquid chromatography tandem mass spectroscopy (LC-MS), water contact angle (WCA), and Fourier transform infrared (FTIR) spectroscopy. The results indicate that different pathways substitute different amounts of glucosamine onto silk chains, with control over resulting material properties, including hydrophobicity/hydrophilicity and biological responses. The aqueous processability of these conjugates into functional material formats (films, sponges) is assessed. These new classes of bio-inspired materials can lead to multifunctional biomaterials for potential applications in different fields of biomedical engineering.

Programmable design of seed coating function induces water-stress tolerance in semi-arid regions

In semi-arid regions, water stress during seed germination and early seedling growth is the highest cause of crop loss. In nature, some seeds (for example, chia and basil) produce a mucilage-based hydrogel that creates a germination-promoting microenvironment by retaining water, regulating nutrient entry and facilitating interactions with beneficial microorganisms. Inspired by this strategy, a two-layered biopolymer-based seed coating has been developed to increase germination and water-stress tolerance in semi-arid, sandy soils. Seeds are coated with a silk/trehalose inner layer containing rhizobacteria and a pectin/carboxymethylcellulose outer layer that reswells upon sowing and acts as a water jacket. Using Phaseolus vulgaris (common bean) cultured under water-stress conditions in an experimental farm in Ben Guerir, Morocco, the proposed seed coating effectively delivered rhizobacteria to form root nodules, resulted in plants with better health and mitigated water stress in drought-prone marginal lands. A programmable seed coating technology has the potential to increase seed germination and water-stress tolerance in semi-arid, sandy soils.

Oxygen Permeability of Silk Fibroin Hydrogels and Their Use as Materials for Contact Lenses: A Purposeful Analysis

Fibroin is a fibrous protein that can be conveniently isolated from the silk cocoons produced by the larvae of Bombyx mori silk moth. In its form as a hydrogel, Bombyx mori silk fibroin (BMSF) has been employed in a variety of biomedical applications. When used as substrates for biomaterial-cells constructs in tissue engineering, the oxygen transport characteristics of the BMSF membranes have proved so far to be adequate. However, over the past three decades the BMSF hydrogels have been proposed episodically as materials for the manufacture of contact lenses, an application that depends on substantially elevated oxygen permeability. This review will show that the literature published on the oxygen permeability of BMSF is both limited and controversial. Additionally, there is no evidence that contact lenses made from BMSF have ever reached commercialization. The existing literature is discussed critically, leading to the conclusion that BMSF hydrogels are unsuitable as materials for contact lenses, while also attempting to explain the scarcity of data regarding the oxygen permeability of BMSF. To the author’s knowledge, this review covers all publications related to the topic.

Quadruple-responsive nanoparticle-mediated targeted combination chemotherapy for metastatic breast cancer

The synergism of combination chemotherapy can only be achieved under specific drug ratios. Herein, hyaluronic acid (HA)-functionalized regenerated silk fibroin-based nanoparticles (NPs) were used to concurrently deliver curcumin (CUR) and 5-fluorouracil (5-FU) at various weight ratios (3.3 : 1, 1.6 : 1, 1.1 : 1, 1 : 1, and 1 : 1.2) to breast tumor cells. The generated HA-CUR/5-FU-NPs were found to have desirable particle sizes (around 200 nm), narrow size distributions, and negative zeta potentials (about -26.0 mV). Interestingly, these NPs showed accelerated drug release rates when they were exposed to buffers that mimicked the multi-hallmarks in the tumor microenvironment (pH/hydrogen peroxide/glutathione/hyaluronidase). The surface functionalization of NPs with HA endowed them with in vitro and in vivo breast tumor-targeting properties. Furthermore, we found that the co-loading of CUR and 5-FU in HA-functionalized NPs exhibited obvious synergistic anti-cancer, pro-apoptotic, and anti-migration effects, and the strongest synergism was found at the CUR/5-FU weight ratio of 1 : 1.2. Most importantly, mice experiments revealed that HA-CUR/5-FU-NPs (1 : 1.2) showed a superior anti-cancer activity against metastatic breast cancer compared to the single drug-loaded NPs and non-functionalized CUR/5-FU-NPs (1 : 1.2). Collectively, these results demonstrate that HA-CUR/5-FU-NPs (1 : 1.2) can be exploited as a robust nanococktail for the treatment of breast cancer and its lung metastasis.