Auranofin loaded silk fibroin nanoparticles for colorectal cancer treatment

Colorectal cancer (CRC) is the second most common cause of cancer related deaths worldwide and the prevalence in young people especially is increasing annually. In the search for innovative approaches to treat the disease, drug delivery systems (DDS) are promising owing to their unique properties, which allow improved therapeutic results with lower drug concentrations, overcoming drug resistance and at the same time potentially reducing side effects. Silk fibroin is a biopolymer that can be processed to obtain biocompatible and biodegradable nanoparticles that can be efficiently loaded by surface adsorption with small-molecule therapeutics and allow their transport and sustained release by modulating their pharmacokinetics. Auranofin (AF) has recently been repurposed for its strong anticancer activity and is currently in clinical trials. Its mechanism of action is through the inhibition of thioredoxin reductase enzymes, which play an essential role in several intracellular processes and are overexpressed in some tumours. Taking into account that AF has a low solubility in water, we propose silk fibroin nanoparticles (SFN) as AF carrier in order to improve its bioavailability, increasing cellular absorption and preventing its degradation or avoiding some resistance mechanisms. Here we report the preparation and characterization of a new formulation of AF-loaded silk fibroin nanoparticles (SFN-AF), its functionalization with FITC for the analysis of cellular uptake, as well as its cytotoxic activity against cell lines of human colorectal cancer (HT29 and HCT116) in both 2D and 3D cell cultures. 3D spheroid models provide a 3D environment which mimics the 3D aspects of CRC observed in vivo and represents an effective 3D environment to screen therapeutics for the treatment of CRC. The loaded nanoparticles showed a spherical morphology with a hydrodynamic diameter of ~ 160 nm and good stability in aqueous solution due to their negative surface charges. FESEM-EDX analysis revealed a homogeneous distribution of Au clusters with high electron density on the surface of the nanoparticles. SFN-AF incubated in phosphate buffer at 37 °C released 77% of the loaded AF over 10 days, showing an initial burst and then sustained release. Flow cytometry analysis showed that FITC-SFN-AF was efficiently internalized by both cell lines, which was confirmed by confocal microscopy imaging. SFN enhanced the cytotoxicity of AF in 2D cultures in both CRC lines. Promising results were also obtained in 3D culture paving the way for future application of this strategy as a therapy for CRC.

Investigation of Chip Morphology in Elliptical Vibration Micro-Turning of Silk Fibroin

Silk fibroin, known for its biocompatibility and biodegradability, holds significant promise for biomedical applications, particularly in drug delivery systems. The precise fabrication of silk fibroin particles, specifically those ranging from tens of nanometres to hundreds of microns, is critical for these uses. This study introduces elliptical vibration micro-turning as a method for producing silk fibroin particles in the form of cutting chips to serve as carriers for drug delivery systems. A hybrid finite element and smoothed particle hydrodynamics (FE-SPH) model was used to investigate how vibration parameters, such as frequency and amplitude, influence chip formation and morphology. This research is essential for determining the size and shape of silk fibroin particles, which are crucial for their effectiveness in drug delivery systems. The results demonstrate the superior capability of elliptical vibration micro-turning for producing shorter, spiral-shaped chips in the size range of tens of microns, in contrast to the long, continuous chips with zig-zag folds and segmented edges generated by conventional micro-turning. The unique zig-zag shapes result from the interplay between the high flexibility and hierarchical structure of silk fibroin and the controlled cutting environment provided by the diamond tool. Additionally, higher vibration frequencies and lower vertical amplitudes promote chip curling, facilitate breakage, and improve chip control, while reducing cutting forces. Experimental trials further validate the accuracy of the hybrid model. This study represents a significant advancement in the processing of silk fibroin film, offering a complementary approach to fabricating short, spiral-shaped silk fibroin particles with a high surface-area-to-volume ratio compared to traditional spheroids, which holds great potential for enhancing drug-loading efficiency in high-precision drug delivery systems.

The Biologically Active Biopolymer Silk: The Antibacterial Effects of Solubilized Bombyx mori Silk Fibroin with Common Wound Pathogens

Antibacterial properties are desirable in wound dressings. Silks, among many material formats, have been investigated for use in wound care. However, the antibacterial properties of liquid silk are poorly understood. The aim of this study is to investigate the inherent antibacterial properties of a Bombyx mori silk fibroin solution. Silk fibroin solutions containing ≥ 4% w/v silk fibroin do not support the growth of two common wound pathogens, Staphylococcus aureus and Pseudomonas aeruginosa. When liquid silk is added to a wound pad and placed on inoculated culture plates mimicking wound fluid, silk is bacteriostatic. Viability tests of the bacterial cells in the presence of liquid silk show that cells remain intact within the silk but could not be cultured. Liquid silk appears to provide a hostile environment for S. aureus and P. aeruginosa and inhibits growth without disrupting the cell membrane. This effect can be beneficial for wound healing and supports future healthcare applications for silk. This observation also indicates that liquid silk stored prior to processing is unlikely to experience microbial spoilage.

Revisiting edible insects as sources of therapeutics and drug delivery systems for cancer therapy

Cancer has been medicine's most formidable foe for long, and the rising incidence of the disease globally has made effective cancer therapy a significant challenge. Drug discovery is targeted at identifying efficacious compounds with minimal side effects and developments in nanotechnology and immunotherapy have shown promise in the fight against this complicated illness. Since ancient times, insects and insect-derived products have played a significant role in traditional medicine across several communities worldwide. The aim of this study was to inspect the traditional use of edible insects in various cultures and to explore their modern use in cancer therapy. Edible insects are sources of nutrients and a variety of beneficial substances with anticancer and immunomodulatory potential. Recently, insect derived bioactive-components have also been used as nanoparticles either in combination with chemotherapeutics or as a nano-cargo for the enhanced delivery of chemotherapeutic drugs due to their high biocompatibility, low bio-toxicity, and their antioxidant and anticancer effects. The crude extracts of different edible insects and their active components such as sericin, cecropin, solenopsin, melittin, antimicrobial peptides and fibroin produce anti-cancer and immunomodulatory effects by various mechanisms which have been discussed in this review.

Silk Bioconjugates: From Chemistry and Concept to Application

Medical silks have captured global interest. While silk sutures have a long track record in humans, silk bioconjugates are still in preclinical development. This perspective examines key advances in silk bioconjugation, including the fabrication of silk-protein conjugates, bioconjugated silk particles, and bioconjugated substrates to enhance cell-material interactions in two and three dimensions. Many of these systems rely on chemical modification of the silk biopolymer, often using carbodiimide and reactive ester chemistries. However, recent progress in enzyme-mediated and click chemistries has expanded the molecular toolbox to enable biorthogonal, site-specific conjugation in a single step when combined with recombinant silk fibroin tagged with noncanonical amino acids. This perspective outlines key strategies available for chemical modification, compares the resulting silk conjugates to clinical benchmarks, and outlines open questions and areas that require more work. Overall, this assessment highlights a domain of new sunrise capabilities and development opportunities for silk bioconjugates that may ultimately offer new ways of delivering improved healthcare.

An Up-to-date Review on Protein-based Nanocarriers in the Management of Cancer

BACKGROUND

A big health issue facing the world's population is cancer. An alarming increase in cancer patients was anticipated by worldwide demographic statistics, which showed that the number of patients with different malignancies was rapidly increasing. By 2025, probably 420 million cases were projected to be achieved. The most common cancers diagnosed are breast, colorectal, prostate, and lung. Conventional treatments, such as surgery, chemotherapy, and radiation therapy, have been practiced.

OBJECTIVE

In recent years, the area of cancer therapy has changed dramatically with expanded studies on the molecular-level detection and treatment of cancer. Recent advances in cancer research have seen significant advances in therapies such as chemotherapy and immunotherapy, although both have limitations in effectiveness and toxicity.

METHODS

The development of nanotechnology for anticancer drug delivery has developed several potentials as nanocarriers, which may boost the pharmacokinetic and pharmacodynamic effects of the drug product and substantially reduce the side effects.

RESULTS

The advancement in non-viral to viral-based protein-based nanocarriers for treating cancer has earned further recognition in this respect. Many scientific breakthroughs have relied on protein-based nanocarriers, and proteins are essential organic macromolecules for life. It allows targeted delivery of passive or active tumors using non-viral-based protein-based nanocarriers to viral-based protein nanocarriers. When targeting cancer cells, both animal and plant proteins may be used in a formulation process to create self-assembled viruses and platforms that can successfully eradicate metastatic cancer cells.

CONCLUSION

This review, therefore, explores in depth the applications of non-viral to viral proteinbased noncarriers with a specific focus on intracellular drug delivery and anti-cancer drug targeting ability.

Biopolymeric Prodrug Systems as Potential Antineoplastic Therapy

Nowadays, cancer represents a major public health issue, a substantial economic issue, and a burden for society. Limited by numerous disadvantages, conventional chemotherapy is being replaced by new strategies targeting tumor cells. In this context, therapies based on biopolymer prodrug systems represent a promising alternative for improving the pharmacokinetic and pharmacologic properties of drugs and reducing their toxicity. The polymer-directed enzyme prodrug therapy is based on tumor cell targeting and release of the drug using polymer–drug and polymer–enzyme conjugates. In addition, current trends are oriented towards natural sources. They are biocompatible, biodegradable, and represent a valuable and renewable source. Therefore, numerous antitumor molecules have been conjugated with natural polymers. The present manuscript highlights the latest research focused on polymer–drug conjugates containing natural polymers such as chitosan, hyaluronic acid, dextran, pullulan, silk fibroin, heparin, and polysaccharides from Auricularia auricula.

Volumetric Scalability of Microfluidic and Semi-Batch Silk Nanoprecipitation Methods

Silk fibroin nanoprecipitation by organic desolvation in semi-batch and microfluidic formats provides promising bottom-up routes for manufacturing narrow polydispersity, spherical silk nanoparticles. The translation of silk nanoparticle production to pilot, clinical, and industrial scales can be aided through insight into the property drifts incited by nanoprecipitation scale-up and the identification of critical process parameters to maintain throughout scaling. Here, we report the reproducibility of silk nanoprecipitation on volumetric scale-up in low-shear, semi-batch systems and estimate the reproducibility of chip parallelization for volumetric scale-up in a high shear, staggered herringbone micromixer. We showed that silk precursor feeds processed in an unstirred semi-batch system (mixing time > 120 s) displayed significant changes in the nanoparticle physicochemical and crystalline properties following a 12-fold increase in volumetric scale between 1.8 and 21.9 mL while the physicochemical properties stayed constant following a further 6-fold increase in scale to 138 mL. The nanoparticle physicochemical properties showed greater reproducibility after a 6-fold volumetric scale-up when using lower mixing times of greater similarity (8.4 s and 29.4 s) with active stirring at 400 rpm, indicating that the bulk mixing time and average shear rate should be maintained during volumetric scale-up. Conversely, microfluidic manufacture showed high between-batch repeatability and between-chip reproducibility across four participants and microfluidic chips, thereby strengthening chip parallelization as a production strategy for silk nanoparticles at pilot, clinical, and industrial scales.

The Effect of Sterilization on the Characteristics of Silk Fibroin Nanoparticles

In recent years, silk fibroin nanoparticles (SFNs) have been consolidated as drug delivery systems (DDSs) with multiple applications in personalized medicine. The design of a simple, inexpensive, and scalable preparation method is an objective pursued by many research groups. When the objective is to produce nanoparticles suitable for biomedical uses, their sterility is essential. To achieve sufficient control of all the crucial stages in the process and knowledge of their implications for the final characteristics of the nanoparticles, the present work focused on the final stage of sterilization. In this work, the sterilization of SFNs was studied by comparing the effect of different available treatments on the characteristics of the nanoparticles. Two different sterilization methods, gamma irradiation and autoclaving, were tested, and optimal conditions were identified to achieve the sterilization of SFNs by gamma irradiation. The minimum irradiation dose to achieve sterilization of the nanoparticle suspension without changes in the nanoparticle size, polydispersity, or Z-potential was determined to be 5 kiloGrays (kGy). These simple and safe methods were successfully implemented for the sterilization of SFNs in aqueous suspension and facilitate the application of these nanoparticles in medicine.

Silk Fibroin/Poly(vinyl Alcohol) Microneedles as Carriers for the Delivery of Singlet Oxygen Photosensitizers

Photodynamic therapy (PDT) is a medical treatment in which a combination of a photosensitizing drug and visible light produces highly cytotoxic reactive oxygen species (ROS) that leads to cell death. One of the main drawbacks of PDT for topical treatments is the limited skin penetration of some photosensitizers commonly used in this therapy. In this study, we propose the use of polymeric microneedles (MNs) prepared from silk fibroin and poly(vinyl alcohol) (PVA) to increase the penetration efficiency of porphyrin as possible applications in photodynamic therapy. The microneedle arrays were fabricated from mixtures in different proportions (1:0, 7:3, 1:1, 3:7, and 0:1) of silk fibroin and PVA solutions (7%); the polymer solutions were cast in polydimethylsiloxane (PDMS) molds and dried overnight. Patches containing grids of 10 × 10 microneedles with a square-based pyramidal shape were successfully produced through this approach. The polymer microneedle arrays showed good mechanical strength under compression force and sufficient insertion depth in both Parafilm M and excised porcine skin at different application forces (5, 20, 30, and 40 N) using a commercial applicator. We observe an increase in the cumulative permeation of 5-[4-(2-carboxyethanoyl) aminophenyl]-10,15,20-tris-(4-sulphonatophenyl) porphyrin trisodium through porcine skin treated with the polymer microneedles after 24 h. MNs may be a promising carrier for the transdermal delivery of photosensitizers for PDT, improving the permeation of photosensitizer molecules through the skin, thus improving the efficiency of this therapy for topical applications.

Micro- and Nanosized Substances Cause Different Autophagy-Related Responses

With rapid industrialization, humans produce an increasing number of products. The composition of these products is usually decomposed. However, some substances are not easily broken down and gradually become environmental pollutants. In addition, these substances may cause bioaccumulation, since the substances can be fragmented into micro- and nanoparticles. These particles or their interactions with other toxic matter circulate in humans via the food chain or air. Whether these micro- and nanoparticles interfere with extracellular vesicles (EVs) due to their similar sizes is unclear. Micro- and nanoparticles (MSs and NSs) induce several cell responses and are engulfed by cells depending on their size, for example, particulate matter with a diameter ≤2.5 μm (PM2.5). Autophagy is a mechanism by which pathogens are destroyed in cells. Some artificial materials are not easily decomposed in organisms. How do these cells or tissues respond? In addition, autophagy operates through two pathways (increasing cell death or cell survival) in tumorigenesis. Many MSs and NSs have been found that induce autophagy in various cells and tissues. As a result, this review focuses on how these particles interfere with cells and tissues. Here, we review MSs, NSs, and PM2.5, which result in different autophagy-related responses in various tissues or cells.

Emerging Silk Material Trends: Repurposing, Phase Separation and Solution-Based Designs

Silk continues to amaze. This review unravels the most recent progress in silk science, spanning from fundamental insights to medical silks. Key advances in silk flow are examined, with specific reference to the role of metal ions in switching silk from a storage to a spinning state. Orthogonal thermoplastic silk molding is described, as is the transfer of silk flow principles for the triggering of flow-induced crystallization in other non-silk polymers. Other exciting new developments include silk-inspired liquid-liquid phase separation for non-canonical fiber formation and the creation of "silk organelles" in live cells. This review closes by examining the role of silk fabrics in fashioning facemasks in response to the SARS-CoV-2 pandemic.

Optimizing interactions between soluble silk fibroin and capryl glucoside for design of a natural and high-performance co-surfactant system

OBJECTIVES

Because of the strong consumer driver towards more natural or higher sustainability cosmetic products, silk fibroin was evaluated to help develop a formulation with natural and effective ingredients for personal care. In order to exploit the physical properties of silk fibroin, it was evaluated to maximize the surfactant properties of other commercial ingredients to lower surface tension and build up viscosity. A synergistic effect was seen between silk fibroin and capryl glucoside, a sugar surfactant which exhibited a natural and effective co-surfactant system. This system demonstrated better surface tension properties than sodium laureth sulphate (SLES), cocamidopropyl betaine (CAPB), rhamnolipids and sophorolipids, which led to greater foamability and cleansing properties. This system proved to also be compatible with polysaccharide viscosity modifiers to enhance the viscosity of the system. The present study comprises a systematic exploration of natural formulation development of silk proteins and other natural ingredients, which result in high performance such as enhanced foam quality, foam stability and enhanced sebum removal. All of these properties are desirable and may utilized when formulating cleaners and shampoos.

METHODS

A force tensiometer, Attension Sigma 701, was used to measure the surface tension of the silk protein and its various combinations with biosurfactants and biopolymers. To measure bulk rheology, a traditional mechanical rheometer TA DHR-3 was utilized. Foaming tests and sebum removal assays were also carried out to evaluate the performance of the samples.

RESULTS

Silk fibroin was evaluated to maximize the surfactant properties of other commercial systems to develop a formulation containing natural and effective ingredients for personal care. The surface activity of silk proteins was seen to be synergistically enhanced in the presence of sugar surfactants such as capryl glucoside, resulting in a surface tension at the air-water interface which is lower than either that of pure silk fibroin or pure capryl glucoside. This surface tension value is additionally lower than that obtained from currently utilized synthetic surfactants like sodium laureth sulphate (SLES) and cocamidopropyl betaine (CAPB). This reduction in surface tension demonstrated greater foamability and cleansing properties than that of the commercial systems. The very low surface tension values obtained through combinations of silk proteins and glucoside resulted in a natural and effective co-surfactant system by forming high-quality stable foams and enhancing sebum removal. The rheological performance of the silk proteins was impacted through microstructure modifications as a result of interactions with biopolymers like carrageenan. This shows that this system is compatible with polysaccharide viscosity modifiers. It was observed that both the flow curve and the absolute viscosity values were significantly impacted in the presence of carrageenan, with higher viscosity generation and significant non-Newtonian/shear thinning behaviour evolution. These results indicate that the silk fibroin can be utilized to build a high-performance natural product and significantly enhance the performance of other natural/sustainable cosmetic formulations through building synergistic interactions with other natural ingredients such as sugar surfactants and biopolymers. These properties exhibited by this system are all desirable for cleansers and shampoos within the cosmetic industry.

CONCLUSION

Silk fibroin in combination with capryl glucoside outperforms other commercial surfactants that are commonly used in the industry because of its surface-active behaviour and synergy. This system is then enhanced further with polysaccharide rheological modifiers, carrageen and xanthan gum to help build up viscosity. The complex mixture of silk fibroin, sugar surfactant and biopolymer results in a formulation that is all natural, while still having high performance by achieving great foamability and enhanced sebum removal. The mixture can further be used to formulate a fully natural product such as a cleanser or shampoo while still having the same or greater effectiveness as synthetic surfactants and ingredients typically used in cosmetic formulations.

Silk Nanoparticle Manufacture in Semi-Batch Format

Silk nanoparticles have demonstrated utility across a range of biomedical applications, especially as drug delivery vehicles. Their fabrication by bottom-up methods such as nanoprecipitation, rather than top-down manufacture, can improve critical nanoparticle quality attributes. Here, we establish a simple semi-batch method using drop-by-drop nanoprecipitation at the lab scale that reduces special-cause variation and improves mixing efficiency. The stirring rate was an important parameter affecting nanoparticle size and yield (400 < 200 < 0 rpm), while the initial dropping height (5.5 vs 7.5 cm) directly affected nanoparticle yield. Varying the nanoparticle standing time in the mother liquor between 0 and 24 h did not significantly affect nanoparticle physicochemical properties, indicating that steric and charge stabilizations result in high-energy barriers for nanoparticle growth. Manufacture across all tested formulations achieved nanoparticles between 104 and 134 nm in size with high β-sheet content, spherical morphology, and stability in aqueous media for over 1 month at 4 °C. This semi-automated drop-by-drop, semi-batch silk desolvation offers an accessible, higher-throughput platform for standardization of parameters that are difficult to control using manual methodologies.

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.

Manual Versus Microfluidic-Assisted Nanoparticle Manufacture: Impact of Silk Fibroin Stock on Nanoparticle Characteristics

Silk has a long track record of clinical use in the human body, and new formulations, including silk nanoparticles, continue to reveal the promise of this natural biopolymer for healthcare applications. Native silk fibroin can be isolated directly from the silk gland, but generating sufficient material for routine studies is difficult. Consequently, silk fibroin, typically extracted from cocoons, serves as the source for nanoparticle formation. This silk requires extensive processing (e.g., degumming, dissolution, etc.) to yield a hypoallergenic aqueous silk stock, but the impact of processing on nanoparticle production and characteristics is largely unknown. Here, manual and microfluidic-assisted silk nanoparticle manufacturing from 60- and 90-min degummed silk yielded consistent particle sizes (100.9-114.1 nm) with low polydispersity. However, the zeta potential was significantly lower (P < 0.05) for microfluidic-manufactured nanoparticles (-28 to -29 mV) than for manually produced nanoparticles (-39 to -43 mV). Molecular weight analysis showed a nanoparticle composition similar to that of the silk fibroin starting stock. Reducing the molecular weight of silk fibroin reduced the particle size for degumming times ≤30 min, whereas increasing the molecular weight polydispersity improved the nanoparticle homogeneity. Prolonged degumming (>30 min) had no significant effect on particle attributes. Overall, the results showed that silk fibroin processing directly impacts nanoparticle characteristics.

Emergence in protein derived nanomedicine as anticancer therapeutics: More than a tour de force

Cancer has thwarted as a major health problem affecting the global population. With an alarming increase in the patient population suffering from diverse varieties of cancers, the global demographic data predicts sharp escalation in the number of cancer patients. This can be expected to reach 420 million cases by 2025. Among the diverse types of cancers, the most frequently diagnosed cancers are the breast, colorectal, prostate and lung cancer. From years, conventional treatment approaches like surgery, chemotherapy and radiation therapy have been practiced. In the past few years, increasing research on molecular level diagnosis and treatment of cancers have significantly changed the realm of cancer treatment. Lately, uses of advanced chemotherapy and immunotherapy like treatments have gained significant progress in the cancer therapy, but these approaches have several limitations on their safety and toxicity. This has generated lot of momentum for the evolution of new drug delivery approaches for the effective delivery of anticancer therapeutics, which may improve the pharmacokinetic and pharmacodynamic effect of the drugs along with significant reduction in the side effects. In this regard, the protein-based nano-medicines have gained wider attention in the management of cancer. Proteins are organic macromolecules essential, for life and have quite well explored in developing the nano-carriers. Furthermore, it provides passive or active tumour cell targeted delivery, by using protein based nanovesicles or virus like structures, antibody drug conjugates, viral particles, etc. Moreover, by utilizing various formulation strategies, both the animal and plant derived proteins can be converted to produce self-assembled virus like nano-metric structures with high efficiency in targeting the metastatic cancer cells. Therefore, the present review extensively discusses the applications of protein-based nano-medicine with special emphasis on intracellular delivery/drug targeting ability for anticancer drugs.

Revealing the Influence of the Degumming Process in the Properties of Silk Fibroin Nanoparticles

Several studies have stated that the process used for sericin removal, or degumming, from silk cocoons has a strong impact in the silk fibroin integrity and consequently in their mechanical or biochemical properties after processing it into several biomaterials (e.g. fibers, films or scaffolds) but still, there is a lack of information of the impact on the features of silk nanoparticles. In this work, silk cocoons were degummed following four standard methods: autoclaving, short alkaline (Na2CO3) boiling, long alkaline (Na2CO3) boiling and ultrasounds. The resultant silk fibroin fibers were dissolved in the ionic liquid 1-ethyl-3-methylimidazolium acetate and used for nanoparticle synthesis by rapid desolvation in polar organic solvents. The relative efficiencies of the degumming processes and the integrity of the resulting fibroin fibers obtained were analyzed by mass loss, optical microscopy, thermogravimetric analysis, infrared spectroscopy and SDS-PAGE. Particle sizes and morphology were analyzed by Dynamic Light Scattering and Field Emission Scanning Electronic Microscopy. The results showed that the different treatments had a remarkable impact on the integrity of the silk fibroin chains, as confirmed by gel electrophoresis, which can be correlated with particle mean size and size distribution changes. The smallest nanoparticles (156 ± 3 nm) and the most negative Z potential (-30.2 ± 1.8 mV) were obtained with the combination of long treatment (2 h) of boiling in alkaline solution (Na2CO3 0.02 eq/L). The study confirms that parameters of the process, such as composition of the solution and time of the degumming step, must be controlled in order to reach an optimum reproducibility of the nanoparticle production.

Silk fibroin-based nanotherapeutics: application in the treatment of colonic diseases

The incidence of colonic diseases (e.g., inflammatory bowel diseases and colon cancer) is rapidly rising. Nanotherapeutic has been considered as a promising strategy in the treatment of colonic diseases. Silk fibroin (SF) has been widely used as a drug-carrier matrix. Interestingly, SF-based nanoparticles (SFNPs) have intrinsic anti-inflammatory activity, wound healing capacity and lysosomal environment-responsive drug-release property. With further investigations, the sequences of SF molecules could be precisely modified through chemical reactions or transgenic techniques to greatly improve the properties of SFNPs. Here, we review recent advances in the application of SFNPs toward the treatment of colonic diseases. We also discuss future developments that might improve the anti-inflammatory and anti-colon cancer activities of SF-based nanotherapeutics.

A Review for the Synthesis of Silk Fibroin Nanoparticles with Different Techniques and Their Ability to be Used for Drug Delivery

Background:

Silk fibroin is the main protein of silk, and it has recently been evaluated for drug delivery applications due to its excellent properties. Specifically, silk fibroin exhibits good biocompatibility, biodegradability and low immunogenicity. Fibroin nanoparticles have attracted attention due to their high binding ability to different drugs as well as their ability for controlled drug release. The improvement of the therapeutic efficiency of drug encapsulation is important and depends on the particle size, the chemical structure and the properties of the silk fibroin nanoparticles.

Methods:

There is a variety of methods for the preparation of fibroin nanoparticles such as (i) electrospraying and desolvation method, (ii) supercritical fluid technologies, (iii) capillary-microdot technique, (iv) salting out etc. Furthermore, various techniques have been used for the characterization of nanoparticles such as SEM (scanning electron microscopy), TEM (transmission electron microscopy), DLS (dynamic light scattering), Zeta-potential and FTIR (Fourier transform infrared spectroscopy). Different drugs (paclitaxel, curcumin, 5-fluorouracil etc) have been encapsulated in fibroin nanoparticles.

Results:

Each separated synthesis method has different advantages such as (i) high yield, (ii) avoid use of toxic solvents, (iii) low cost, (iv) controllable particle size, (v) no organic solvent residue, (vi) simplicity of operation, (vii) small particles size, (viii) homeliness of operation, (ix) restrainable particle size, (x) easy and safe to operate, (xi) no use of organic solvent. Moreover, some major drugs studied are Floxuridine, Fluorouracil, Curcumin, Doxorubicin, Metotrexate, Paclitaxel and Doxorubicin, Horseradish peroxidase. All the above combinations (preparation method-drug) are studied in detail.

Conclusion:

Various drugs have been encapsulated successfully in silk fibroin and all of them exhibit a significant release rate. Finally, the encapsulation efficiency and release rate depend on the molecular weight of the drugs and it can be adjusted by controlling the crystallinity and concentration of silk fibroin.

PEGylation-Dependent Metabolic Rewiring of Macrophages with Silk Fibroin Nanoparticles

Silk fibroin nanoparticles are emerging as promising nanomedicines, but their full therapeutic potential is yet to be realized. These nanoparticles can be readily PEGylated to improve colloidal stability and to tune degradation and drug release profiles; however, the relationship between silk fibroin nanoparticle PEGylation and macrophage activation still requires elucidation. Here, we used in vitro assays and nuclear magnetic resonance based metabolomics to examine the inflammatory phenotype and metabolic profiles of macrophages following their exposure to unmodified or PEGylated silk fibroin nanoparticles. The macrophages internalized both types of nanoparticles, but they showed different phenotypic and metabolic responses to each nanoparticle type. Unmodified silk fibroin nanoparticles induced the upregulation of several processes, including production of proinflammatory mediators (e.g., cytokines), release of nitric oxide, and promotion of antioxidant activity. These responses were accompanied by changes in the macrophage metabolomic profiles that were consistent with a proinflammatory state and that indicated an increase in glycolysis and reprogramming of the tricarboxylic acid cycle and the creatine kinase/phosphocreatine pathway. By contrast, PEGylated silk fibroin nanoparticles induced milder changes to both inflammatory and metabolic profiles, suggesting that immunomodulation of macrophages with silk fibroin nanoparticles is PEGylation-dependent. Overall, PEGylation of silk fibroin nanoparticles reduced the inflammatory and metabolic responses initiated by macrophages, and this observation could be used to guide the therapeutic applications of these nanoparticles.

Reverse-engineered silk hydrogels for cell and drug delivery

Silk is an important biopolymer for (bio)medical applications because of its unique and highly versatile structure and its robust clinical track record in human medicine. Silk can be processed into many material formats, including physically and chemically cross-linked hydrogels that have almost limitless applications ranging from tissue engineering to biomedical imaging and sensing. This concise review provides a detailed background of silk hydrogels, including silk structure-function relationships, biocompatibility and biodegradation, and it explores recent developments in silk hydrogel utilization, with specific reference to drug and cell delivery. We address common pitfalls and misconceptions while identifying emerging opportunities, including 3D printing.

Microfluidic-assisted silk nanoparticle tuning

Silk is now making inroads into advanced pharmaceutical and biomedical applications. Both bottom-up and top-down approaches can be applied to silk and the resulting aqueous silk solution can be processed into a range of material formats, including nanoparticles. Here, we demonstrate the potential of microfluidics for the continuous production of silk nanoparticles with tuned particle characteristics. Our microfluidic-based design ensured efficient mixing of different solvent phases at the nanoliter scale, in addition to controlling the solvent ratio and flow rates. The total flow rate and aqueous : solvent ratios were important parameters affecting yield (1 mL min-1 > 12 mL min-1). The ratios also affected size and stability; a solvent : aqueous total flow ratio of 5 : 1 efficiently generated spherical nanoparticles 110 and 215 nm in size that were stable in water and had a high beta-sheet content. These 110 and 215 nm silk nanoparticles were not cytotoxic (IC50 > 100 μg mL-1) but showed size-dependent cellular trafficking. Overall, microfluidic-assisted silk nanoparticle manufacture is a promising platform that allows control of the silk nanoparticle properties by manipulation of the processing variables.

The Biomedical Use of Silk: Past, Present, Future

Humans have long appreciated silk for its lustrous appeal and remarkable physical properties, yet as the mysteries of silk are unraveled, it becomes clear that this outstanding biopolymer is more than a high-tech fiber. This progress report provides a critical but detailed insight into the biomedical use of silk. This journey begins with a historical perspective of silk and its uses, including the long-standing desire to reverse engineer silk. Selected silk structure-function relationships are then examined to appreciate past and current silk challenges. From this, biocompatibility and biodegradation are reviewed with a specific focus of silk performance in humans. The current clinical uses of silk (e.g., sutures, surgical meshes, and fabrics) are discussed, as well as clinical trials (e.g., wound healing, tissue engineering) and emerging biomedical applications of silk across selected formats, such as silk solution, films, scaffolds, electrospun materials, hydrogels, and particles. The journey finishes with a look at the roadmap of next-generation recombinant silks, especially the development pipeline of this new industry for clinical use.

Degradation Behavior of Silk Nanoparticles-Enzyme Responsiveness

Silk nanoparticles are viewed as promising vectors for intracellular drug delivery as they can be taken up into cells by endocytosis and trafficked to lysosomes, where lysosomal enzymes and the low pH trigger payload release. However, the subsequent degradation of the silk nanoparticles themselves still requires study. Here, we report the responsiveness of native and PEGylated silk nanoparticles to degradation following exposure to proteolytic enzymes (protease XIV and α-chymotrypsin) and papain, a cysteine protease. Both native and PEGylated silk nanoparticles showed similar degradation behavior over a 20 day exposure period (degradation rate: protease XIV > papain ≫ α-chymotrypsin). Within 1 day, the silk nanoparticles were rapidly degraded by protease XIV, resulting in a ∼50% mass loss, an increase in particle size, and a reduction in the amorphous content of the silk secondary structure. By contrast, 10 days of papain treatment was necessary to observe any significant change in nanoparticle properties, and α-chymotrypsin treatment had no effect on silk nanoparticle characteristics over the 20-day study period. Silk nanoparticles were also exposed ex vivo to mammalian lysosomal enzyme preparations to mimic the complex lysosomal microenvironment. Preliminary results indicated a 45% reduction in the silk nanoparticle size over a 5-day exposure. Overall, the results demonstrate that silk nanoparticles undergo enzymatic degradation, but the extent and kinetics are enzyme-specific.

Silk nanoparticles: proof of lysosomotropic anticancer drug delivery at single-cell resolution

Silk nanoparticles are expected to improve chemotherapeutic drug targeting to solid tumours by exploiting tumour pathophysiology, modifying the cellular pharmacokinetics of the payload and ultimately resulting in trafficking to lysosomes and triggering drug release. However, experimental proof for lysosomotropic drug delivery by silk nanoparticles in live cells is lacking and the importance of lysosomal pH and enzymes controlling drug release is currently unknown. Here, we demonstrate, in live single human breast cancer cells, the role of the lysosomal environment in determining silk nanoparticle-mediated drug release. MCF-7 human breast cancer cells endocytosed and trafficked drug-loaded native and PEGylated silk nanoparticles (∼100 nm in diameter) to lysosomes, with subsequent drug release from the respective carriers and nuclear translocation within 5 h of dosing. A combination of low pH and enzymatic degradation facilitated drug release from the silk nanoparticles; perturbation of the acidic lysosomal pH and inhibition of serine, cysteine and threonine proteases resulted in a 42% ± 2.2% and 33% ± 3% reduction in nuclear-associated drug accumulation for native and PEGylated silk nanoparticles, respectively. Overall, this study demonstrates the importance of lysosomal activity for anticancer drug release from silk nanoparticles, thereby providing direct evidence for lysosomotropic drug delivery in live cells.