Potential applications of silk sericin, a natural protein from textile industry by-products

Expanding the boundaries of silk sericin biomaterials in biomedical applications

Silk sericin (SS) has a long history as a by-product of the textile industry. SS has emerged as a sustainable material for biomedical engineering due to its material properties including water solubility, diverse impact on biological activities including antibacterial and antioxidant properties, and ability to promote cell adhesion and proliferation. This review addresses the origin, structure, properties, extraction, and underlying functions of this protein. An overview of the growing research studies and market evolution is presented, along with highlights of the most common fabrication matrices (hydrogels, bioinks, porous and fibrous scaffolds) and tissue engineering applications. Finally, the future trends with this protein as a multifaceted toolbox for bioengineering are explored, along with the challenges with SS. Overall, the present review can serve as a foundation for the creation of innovative biomaterials utilizing SS as a fundamental building block that hold market potential.

Mutation in the Bombyx mori BmGMC2 gene impacts silk production and silk protein synthesis

Silk is a natural protein fiber that is predominantly comprised of fibroin and sericin. In addition, it contains seroins, protease inhibitors, enzymes, and other proteins. We found an ecdysone oxidase BmGMC2, notably, which is specifically and highly expressed only in the silk glands of silkworms (Bombyx mori L.). It is also one of the main components of non-cocoon silk, however, its precise function remains unclear. In this study, we examined the spatiotemporal expression pattern of this protein and obtained a homozygous mutant strain (K-GMC2) using the CRISPR-Cas9 system. Compared to the wild-type strain (WT), the silk production and main silk proteins significantly decreased in the larval stage, and the adhesive strength of native silk proteins decreased in the final instar. Proteomic data indicated the abundance of ribosomal proteins decreased significantly in K-GMC2, differentially expressed proteins (DEPs) were enriched in pathways related to neurodegenerative diseases and genetic information processing, indicating that knockout may lead to a certain degree of cell stress, affecting the synthesis of silk proteins. This study investigated the expression pattern and gene function of ecdysone oxidase BmGMC2 in silk and silk glands, laying the groundwork for understanding the role of enzymes in the production of silk fibers.

Silk-derived sericin/fibroin mixture drink fermented with plant-derived Lactococcus lactis BM32-1 improves constipation and related microbiota: a randomized, double-blind, and placebo-controlled clinical trial

We previously showed through clinical trials that one plant-derived lactic acid bacteria (LAB) can improve constipation. We preliminarily found that the plant-derived LAB Lactococcus lactis BM32-1 can grow in a mixture of sericin and fibroin, which are extracted from silk and have been reported to help promote health. Thus, in the present study, we evaluated the favorable effect of a sericin/fibroin mixture (S/F-M), which was extracted from silk prepared from cocoons reared in an aseptic rearing system using an artificial diet, fermented with the BM32-1 strain through a clinical trial. The trial was conducted at Hiroshima University from June to October 2022 as a double-blind, placebo-controlled, randomized parallel-group comparative study with 50 eligible subjects (aged 23-71) who had an average defecation frequency of less than 5 times per week. The subjects were instructed to drink 100 mL of fermented S/F-M or placebo every day. After the 12 weeks of the clinical trial period, the average defecation frequency increased significantly-1.4 times higher than that at baseline in the test group-as compared with the placebo group. Furthermore, the fecal microbiota was also compared before and after treatment, revealing that intake of the fermented S/F-M significantly multiplied the relative abundance of the genera Enterococcus and Clostridium, which have been reported to contribute to the amelioration of constipation by improving the gut microbiota and producing butyric acid, respectively. In conclusion, the S/F-M fermented using the BM32-1 strain improves defecation frequency through alteration of the gut microbiota.

Silk Industry Waste Protein-Derived Sericin Hybrid Nanoflowers for Antibiotics Remediation via Circular Economy

Hybrid protein-copper nanoflowers have emerged as promising materials with diverse applications in biocatalysis, biosensing, and bioremediation. Sericin, a waste biopolymer from the textile industry, has shown potential for fabricating such nanoflowers. However, the influence of the molecular weight of sericin on nanoflower morphology and peroxidase-like activity remains unexplored. This work focused on the self-assembly of nanoflowers using high- and low-molecular-weight (HMW and LMW) silk sericin combined with copper(II) as an inorganic moiety. The peroxidase-like activity of the resulting nanoflowers was evaluated using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and hydrogen peroxide (H2O2). The findings revealed that high-molecular-weight sericin hybrid nanoflowers (HMW-ShNFs) exhibited significantly higher peroxidase-like activity than low-molecular-weight sericin hybrid nanoflowers (LMW-ShNFs). Furthermore, HMW-ShNFs demonstrated superior reusability and storage stability, thereby enhancing their potential for practical use. This study also explored the application of HMW-ShNF for ciprofloxacin degradation to address the environmental and health hazards posed by this antibiotic in water. The results indicated that HMW-ShNFs facilitated the degradation of ciprofloxacin, achieving a maximum degradation of 33.2 ± 1% at pH 8 and 35 °C after 72 h. Overall, the enhanced peroxidase-like activity and successful application in ciprofloxacin degradation underscore the potential of HMW-ShNFs for a sustainable and ecofriendly remediation process. These findings open avenues for the further exploration and utilization of hybrid nanoflowers in various environmental applications.

Anti-Inflammatory Peptide-Conjugated Silk Fibroin/Cryogel Hybrid Dual Fiber Scaffold with Hierarchical Structure Promotes Healing of Chronic Wounds

Chronic wounds resulting from diabetes, pressure, radiation therapy, and other factors continue to pose significant challenges in wound healing. To address this, this study introduces a novel hybrid fibroin fibrous scaffold (FFS) comprising randomly arranged fibroin fibers and vertically aligned cryogel fibers (CFs). The fibroin scaffold is efficiently degummed at room temperature and simultaneously formed a porous structure. The aligned CFs are produced via directional freeze-drying, achieved by controlling solution concentration and freezing polymerization temperature. The incorporation of aligned CFs into the expanded fibroin fiber scaffold leads to enhanced cell infiltration both in vitro and in vivo, further elevating the hybrid scaffold's tissue compatibility. The anti-inflammatory peptide 1 (AP-1) is also conjugated to the hybrid fibrous scaffold, effectively transforming the inflammatory status of chronic wounds from pro-inflammatory to pro-reparative. Consequently, the FFS-AP1+CF group demonstrates superior granulation tissue formation, angiogenesis, collagen deposition, and re-epithelialization during the proliferative phase compared to the commercial product PELNAC. Moreover, the FFS-AP1+CF group displays epidermis thickness, number of regenerated hair follicles, and collagen density closer to normal skin tissue. These findings highlight the potential of random fibroin fibers/aligned CFs hybrid fibrous scaffold as a promising approach for skin tissue filling and tissue regeneration.

Sericin Improves Memory Impairment Via Activation of the PKA-CREB-BDNF Signaling Pathway and Suppression of Oxidative Stress in Ovariectomized Mice

Menopause results in estrogen hormone deficiency which causes changes in brain morphology and cognitive impairments. The risk of breast and ovarian cancer increases with estrogen therapy. Thus, finding a substitute treatment option for women in menopause is necessary. In the current study, the impact of chronic sericin treatment (200 mg/kg/day for 6 weeks, gavage) on memory process, oxidative stress markers, synaptic neurotransmission, and acetylcholinesterase (AChE) activity in the hippocampus (HIP) of ovariectomized (OVX) mice was examined and compared to the effects of 17β-estradiol (Es; 20 µg/kg, s.c.). The results demonstrated that sericin and Es administration improved spatial and recognition memory of the OVX animals in the both Lashley III maze and novel object recognition tests. Moreover, sericin-treated OVX mice showed decreased ROS levels, increased endogenous antioxidant defense capacity, and decreased AChE activity in the HIP. Additionally, sericin and Es therapy up-regulated pre-and-post-synaptic protein markers and increased BDNF, CREB, and protein kinase A (PKA) protein expressions in the HIP of OVX mice. Overall, the activation of the PKA-CREB-BDNF signaling pathway by sericin can provide protection against OVX-induced cognitive dysfunction, making it a potential alternative for managing cognitive deficits in postmenopausal women.

Modeling the 3-dimensional structure of the silkworm's spinning apparatus in silk production

The silk-spinning process of the silkworms transforms the liquid silk solution to a solid state under mild conditions, making it an attractive model for bioinspiration However, the precise mechanism behind silk expulsion remains largely unknown. Here we selected the silkworms as representative models to investigate the silk-spinning mechanism. We used serial block-face scanning electron microscopy (SBF-SEM) to reconstruct the three-dimensional structures of the spinnerets in silkworms at various stages and with different gene backgrounds. By comparing the musculature and duct deformation of these spinneret models during the spinning process, we were able to simulate the morphological changes of the spinneret. Based on the results, we proposed three essential factors for silkworm spinning: the pressure generated by the silk gland, the opening duct, and the pulling force generated by head movement. Understanding the silkworm spinning process provides insights into clarify the fluid-ejecting mechanism of a group of animals. Moreover, these findings are helpful to the development of biomimetic spinning device that mimics the push-and-pull dual-force system in silkworms. STATEMENT OF SIGNIFICANCE: The silkworms' spinning system produces fibers under mild conditions, making it an ideal candidate for bioinspiration. However, the mechanism of silk expulsion is unknown, and the three-dimensional structure of the spinneret is still uncertain. In this study, we reconstructed a detailed 3-dimensional model of the spinneret at near-nanometer resolution, and for the first time, we observed the changes that occur before and during the silk-spinning process. Our reconstructed models suggested that silkworms have the ability to control the spinning process by opening or closing the spinning duct. During the continuously spinning period, both the pressure generated by the silk gland and the pulling force resulting from head movement work in tandem to expel the silk solution. We believe that gaining a full understanding of the spinning process steps can advance our ability to spin synthetic fibers with properties comparable to those of native fibers by mimicking the natural spinning process.

Spidroins under the Influence of Alcohol: Effect of Ethanol on Secondary Structure and Molecular Level Solvation of Silk-Like Proteins

Future sustainable materials based on designer biomolecules require control of the solution assembly, but also interfacial interactions. Alcohol treatments of protein materials are an accessible means to this, making understanding of the process at the molecular level of seminal importance. We focus here on the influence of ethanol on spidroins, the main proteins of silk. By large-scale atomistically detailed molecular dynamics (MD) simulations and interconnected experiments, we characterize the protein aggregation, secondary structure changes, molecular level origins of them, and solvation environment changes for the proteins, as induced by ethanol as a solvation additive. The MD and circular dichoroism (CD) findings jointly show that ethanol promotes ordered structure in the protein molecules, leading to an increase of helix content and turns but also increased aggregation, as revealed by dynamic light scattering (DLS) and light microscopy. The structural changes correlate at the molecular level with increased intramolecular hydrogen bonding. The simulations reveal that polar amino acids, such as glutamine and serine, are most influenced by ethanol, whereas glycine residues are most prone to be involved in the ethanol-induced secondary structure changes. Furthermore, ethanol engages in interactions with the hydrophobic alanine-rich regions of the spidroin, significantly decreasing the hydrophobic interactions of the protein with itself and its surroundings. The protein solutes also change the microstructure of water/ethanol mixtures, essentially decreasing the level of larger local clustering. Overall, the work presents a systematic characterization of ethanol effects on a widely used, common protein type, spidroins, and generalizes the findings to other intrinsically disordered proteins by pinpointing the general features of the response. The results can aid in designing effective alcohol treatments for proteins, but also enable design and tuning of protein material properties by a relatively controllable solvation handle, the addition of ethanol.

Sericin enhances ammonia detoxification by promotes urea cycle enzyme genes and activates hepatic autophagy in relation to CARD-9/MAPK pathway

Urea cycle is an important metabolic process that initiates in liver mitochondria and converts ammonia to urea. The impairment of ammonia detoxification, both primary and secondary causes, lead to hyperammonemia, a life-threatening condition affecting to the brain. Current treatments are not enough effective. In addition, our recent proteomics study in hypercholesterolemic rat model demonstrated that sericin enhances hepatic nitrogenous waste removal through carbamoyl-phosphate synthase 1 (CPS-1), aldehyde dehydrogenase-2 (ALDH-2), and uricase proteins. However, the underlining mechanisms regard to this property is not clarified yet. Therefore, the present study aims to examine the effect of sericin on urea cycle enzyme genes (CPS-1 and ornithine transcarbamylase; OTC) and proteins (mitogen-activated protein kinase; MAPK, caspase recruitment domain-containing protein 9; CARD-9, Microtubule-associated protein light chain 3; LC-3), which relate to urea production and liver homeostasis in hepatic cell line (HepG2) and hypercholesterolemic rat treated with or without sericin. qRT-PCR, immunohistochemistry, and electron microscopy techniques were performed. In vitro study determined that high dose of sericin at 1 mg/ml increased liver detoxification enzyme (Cytochrome P450 1A2; CYP1A2 and ALDH-2) and urea cycle enzyme (CPS-1 and OTC) genes. Both in HepG2 cell and rat liver mitochondria, sericin significantly downregulated CARD-9 (apoptotic protein) expression while upregulated MAPK (hepatic homeostasis protein) and LC-3 (autophagic protein) expressions. Hence, it might be concluded that sericin promotes ammonia detoxification by both increases urea cycle enzyme genes and enhances hepatic autophagy in associated with CARD-9/MAPK pathway (as shown by their own negative relationship). This study presents another beneficial property of sericin to develop an upcoming candidate for ammonia toxicity alleviation and liver function improvement.

A comprehensive review of recent advances in silk sericin: Extraction approaches, structure, biochemical characterization, and biomedical applications

Silks are natural polymers that have been widely used for centuries. Silk consists of a filament core protein, termed fibroin, and a glue-like coating substance formed of sericin (SER) proteins. This protein is extracted from the silkworm cocoons (particularly Bombyx mori) and is mainly composed of amino acids like glycine, serine, aspartic acid, and threonine. Silk SER can be obtained using numerous methods, including enzymatic extraction, high-temperature, autoclaving, ethanol precipitation, cross-linking, and utilizing acidic, alkali, or neutral aqueous solutions. Given the versatility and outstanding properties of SER, it is widely fabricated to produce sponges, films, and hydrogels for further use in diverse biomedical applications. Hence, many authors reported that SER benefits cell proliferation, tissue engineering, and skin tissue restoration thanks to its moisturizing features, antioxidant and anti-inflammatory properties, and mitogenic effect on mammalian cells. Remarkably, SER is used in drug delivery depending on its chemical reactivity and pH-responsiveness. These unique features of SER enhance the bioactivity of drugs, facilitating the fabrication of biomedical materials at nano- and microscales, hydrogels, and conjugated molecules. This review thoroughly outlines the extraction techniques, biological properties, and respective biomedical applications of SER.

Fabrication, Structural Characteristics, and Properties of Sericin-Coated Wool Nonwoven Fabrics

Recently, nonwoven fabrics from natural silk have attracted considerable attention for biomedical and cosmetic applications because of their good mechanical properties and cytocompatibility. Although these fabrics can be easily fabricated using the binding character of sericin, the high cost of silk material may restrict its industrial use in certain areas. In this study, sericin was added as a binder to a cheaper material (wool) to prepare wool-based nonwoven fabrics and investigate the effect of the amount of sericin added on the structural characteristics and properties of the wool nonwoven fabric. It was found using SEM that sericin coated the surface of wool fibers and filled the space between them. With an increase in sericin addition, the porosity, moisture regain, and the contact angle of the sericin-coated wool nonwoven fabric decreased. The maximum stress and initial Young's modulus of the nonwoven fabric increased with the increase in sericin amount up to 32.5%, and decreased with a further increase in the amount of sericin. Elongation at the end steadily decreased with the increase in sericin addition. All of the nonwoven fabrics showed good cytocompatibility, which increased with the amount of sericin added. These results indicate that sericin-coated wool-based nonwoven fabrics may be successfully prepared by adding sericin to wool fibers, and that the properties of these fabrics may be diversely controlled by altering the amount of sericin added, making them promising candidates for biomedical and cosmetic applications.

Structural Characteristics and Properties of Redissolved Silk Sericin

Silk sericin has garnered the attention of researchers as a promising biomaterial because of its good biocompatibility and high water retention. However, despite its useful properties, the poor storage stability of sericin has restricted its extensive use in biorelated applications. This study extracted sericin from silkworm cocoon, dried and stored it as a solid, and then dissolved it in hot water conditions to improve the storage stability of sericin for its use. The dissolution behavior of the extracted sericin solids was examined in conjunction with the structural characteristics and properties of dissolved sericin. Consequently, the results of solution viscosity, gel strength, crystallinity index, and thermal decomposition temperature indicated that the molecular weight (MW) of the dissolved sericin remained constant until a dissolution time of 5 min, following which deterioration was observed. The optimum condition of dissolution of the extracted sericin solid was 5 min at 90 °C. Conclusively, the extracted sericin could be stored in a dry state and dissolved to prepare redissolved sericin aqueous solution with the same MW as extracted sericin, thereby improving the storage stability of the sericin aqueous solution.

Silk Fibroin and Sericin Differentially Potentiate the Paracrine and Regenerative Functions of Stem Cells Through Multiomics Analysis

Silk fibroin (SF) and sericin (SS), the two major proteins of silk, are attractive biomaterials with great potential in tissue engineering and regenerative medicine. However, their biochemical interactions with stem cells remain unclear. In this study, multiomics are employed to obtain a global view of the cellular processes and pathways of mesenchymal stem cells (MSCs) triggered by SF and SS to discern cell-biomaterial interactions at an in-depth, high-throughput molecular level. Integrated RNA sequencing and proteomic analysis confirm that SF and SS initiate widespread but distinct cellular responses and potentiate the paracrine functions of MSCs that regulate extracellular matrix deposition, angiogenesis, and immunomodulation through differentially activating the integrin/PI3K/Akt and glycolysis signaling pathways. These paracrine signals of MSCs stimulated by SF and SS effectively improve skin regeneration by regulating the behavior of multiple resident cells (fibroblasts, endothelial cells, and macrophages) in the skin wound microenvironment. Compared to SS, SF exhibits better immunomodulatory effects in vitro and in vivo, indicating its greater potential as a carrier material of MSCs for skin regeneration. This study provides comprehensive and reliable insights into the cellular interactions with SF and SS, enabling the future development of silk-based therapeutics for tissue engineering and stem cell therapy.

Sericin mediated gold/silver bimetallic nanoparticles and exploration of its multi-therapeutic efficiency and photocatalytic degradation potential

The current investigation aimed at bimetallic gold-silver nanoparticles (Au/Ag NPs), here called BM-GS NPs, synthesis using sericin protein as the reducing agent in an easy, cost-effective, and sustainable way. The obtained BM-GS NPs were characterized by UV-Visible spectroscopy, Transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDS), atomic force microscopy (AFM), Dynamic light scattering (DLS) and Zeta potential, X-ray Powder Diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and Thermogravimetric analysis followed by evaluation of its multitherapeutic and photocatalytic degradation potentials. The TEM analysis revealed its spherical nature and the EDS result displayed the presence of both Ag and Au elements, confirming the synthesis of BM-GS NPs. The XRD pattern verified the crystalline nature of the nanoparticles (NPs). The DLS analysis showed an average size of 86.08 d nm and the zeta potential showed a highly negative value (-26.3 mV) which specifies that the generated bimetallic NPs are stable. The BM-GS NPs exhibited positive wound healing potential (with 63.38% of wound closure rate at 25 μg/ml, as compared to 54.42% by the untreated control) with very negligible toxicity effect on the cell viability of the normal keratinocyte cells. It also demonstrated promising antioxidant properties with 65.00%, 69.23%, and 63.03% activity at 100 μg/ml concentration for ABTS (2, 2-azinobis) (3-ethylbenzothiazoline-6-sulfonic acid)), DPPH (1, 1 diphenyl-2-picrylhydrazyl) and SOD (superoxide dismutase enzyme) assays respectively, antidiabetic potential (with a significantly high α-glucosidase inhibition potential of 99.69% at 10μg/ml concentration and 62.11% of α-amylase enzyme inhibition at 100 μg/ml concentration) and moderate tyrosinase inhibitory potential (with 17.09% at 100 μg/ml concentration). Besides, it displayed reasonable antibacterial potential with the diameter of zone of inhibition ranging between 10.89 and 12.39 mm. Further, its antibacterial mode of action reveals that its effects could be due to being very smaller, the NPs could have penetrated inside the cellular membrane thereby causing rupture and damage to the interior materials leading to cellular lysis. The photocatalytic evaluation showed that synthesized BM-GS NPs have the efficiency of degrading methylene blue dye by 34.70% within 3 h of treatment. The above findings revealed the multi-therapeutic efficacy of the sericin globular protein-mediated BM-GS NPs and its potential future applications in the cosmetics and food sector and environmental contamination management industries.

Biological Materials Processing: Time-Tested Tricks for Sustainable Fiber Fabrication

There is an urgent need to improve the sustainability of the materials we produce and use. Here, we explore what humans can learn from nature about how to sustainably fabricate polymeric fibers with excellent material properties by reviewing the physical and chemical aspects of materials processing distilled from diverse model systems, including spider silk, mussel byssus, velvet worm slime, hagfish slime, and mistletoe viscin. We identify common and divergent strategies, highlighting the potential for bioinspired design and technology transfer. Despite the diversity of the biopolymeric fibers surveyed, we identify several common strategies across multiple systems, including: (1) use of stimuli-responsive biomolecular building blocks, (2) use of concentrated fluid precursor phases (e.g., coacervates and liquid crystals) stored under controlled chemical conditions, and (3) use of chemical (pH, salt concentration, redox chemistry) and physical (mechanical shear, extensional flow) stimuli to trigger the transition from fluid precursor to solid material. Importantly, because these materials largely form and function outside of the body of the organisms, these principles can more easily be transferred for bioinspired design in synthetic systems. We end the review by discussing ongoing efforts and challenges to mimic biological model systems, with a particular focus on artificial spider silks and mussel-inspired materials.

Silk Sericin Protein Materials: Characteristics and Applications in Food-Sector Industries

There is growing concern about the use of plastic in packaging for food materials, as this results in increased plastic waste materials in the environment. To counter this, alternative sources of packaging materials that are natural and based on eco-friendly materials and proteins have been widely investigated for their potential application in food packaging and other industries of the food sector. Sericin, a silk protein that is usually discarded in large quantities by the sericulture and textile industries during the degumming process of manufacturing silk from silk cocoons, can be explored for its application in food packaging and in other food sectors as a functional food and component of food items. Hence, its repurposing can result in reduced economic costs and environmental waste. Sericin extracted from silk cocoon possesses several useful amino acids, such as aspartic acid, glycine, and serine. Likewise, sericin is strongly hydrophilic, a property that confers effective biological and biocompatible characteristics, including antibacterial, antioxidant, anticancer, and anti-tyrosinase properties. When used in combination with other biomaterials, sericin has proved to be effective in the manufacture of films or coating or packaging materials. In this review, the characteristics of sericin materials and their potential application in food-sector industries are discussed in detail.

Regulatory effect of sericin protein in inflammatory pathways; A comprehensive review

Sericin protein is a type of protein derived from silk cocoons. Sericin hydrogen bonds cause adhesion to the silk cocoon. This substance contains a large amount of serine amino acids in its structure. At first, the medicinal properties of this substance were unknown, but today many properties have been discovered for this substance. The unique properties of this substance have made it widely used in the pharmaceutical and cosmetic industries. The applications of Sericin in pharmacy are as follows. Sericin is used to repair wounds by producing collagen. Other uses for the drug include anti-diabetic, anti-cholesterol, metabolic modulator, anti-tumor, heart protection, antioxidant, antibacterial, wound healing, cell proliferation, UV protection, freezing, and skin moisturizing. The physicochemical properties of Sericin have attracted the attention of pharmacists and their widespread use in the production of drugs and treatment of diseases. One of the critical and unique properties of Sericin is its anti-inflammatory property. In this article, this property of Sericin is discussed in detail, and according to the experiments performed by pharmacists, this substance has shown a significant effect in eliminating inflammation. This study aimed to evaluate the impact of Sericin protein in relieving inflammation.

Turmeric Herb Extract-Incorporated Biopolymer Dressings with Beneficial Antibacterial, Antioxidant and Anti-Inflammatory Properties for Wound Healing

Bacterial infection and inflammation caused by excess oxidative stress are serious challenges in chronic wound healing. The aim of this work is to investigate a wound dressing based on natural- and biowaste-derived biopolymers loaded with an herb extract that demonstrates antibacterial, antioxidant, and anti-inflammatory activities without using additional synthetic drugs. Turmeric extract-loaded carboxymethyl cellulose/silk sericin dressings were produced by esterification crosslinking with citric acid followed by freeze-drying to achieve an interconnected porous structure, sufficient mechanical properties, and hydrogel formation in situ in contact with an aqueous solution. The dressings exhibited inhibitory effects on the growth of bacterial strains that were related to the controlled release of the turmeric extract. The dressings provided antioxidant activity as a result of the radical scavenging effect on DPPH, ABTS, and FRAP radicals. To confirm their anti-inflammatory effects, the inhibition of nitric oxide production in activated RAW 264.7 macrophages was investigated. The findings suggested that the dressings could be a potential candidate for wound healing.

Sericin/Human Placenta-Derived Extracellular Matrix Scaffolds for Cutaneous Wound Treatment-Preparation, Characterization, In Vitro and In Vivo Analyses

Human placenta is loaded with an enormous amount of endogenous growth factors, thereby making it a superior biomaterial for tissue regeneration. Sericin is a naturally occurring silk protein that is extensively used for biomedical applications. In the present work, sericin and human placenta-derived extracellular matrix were blended and fabricated in the form of scaffolds using the freeze-drying method for cutaneous wound treatment. The prepared sericin/placenta-derived extracellular matrix (SPEM) scaffolds were characterized to determine their morphology, functional groups, mechanical strength, and antibacterial activity. Scanning electron microscopic analysis of the scaffolds showed smooth surfaces with interconnected pores. In vitro MTT and scratch wound assays performed using HaCaT cells proved the non-toxic and wound-healing efficacy of SPEM scaffolds. In vivo CAM assay using fertilized chick embryos proved the angiogenic potency of the scaffolds. Animal experiments using Wistar albino rats proved that the open excision wounds treated with SPEM scaffolds significantly reduced wound size with collagen deposition. These results confirm that SPEM scaffolds can serve as a promising biomaterial for tissue regeneration.

Molecular weight and molecular weight distribution of sericin protein extracted from cocoon waste of <i>Bombyx mori</i>

Silk sericin comprises a globular water-soluble protein that surrounds silk fibres, sticking them together and providing cocoon adhesion. Sericin was isolated from the extract solution in two ways: the first sample was obtained by concentrating the filtered extract at low pressure (SLP); the second sample was obtained by ultrafiltration (SUF) using a membrane. In this work, the size exclusion-high-performance liquid chromatography involving viscometry and refractive index detectors was used to determine the molecular weight and conformation of sericin polypeptides obtained from cocoons of the Bombyx mori silkworm. The aggregation processes of silk sericin protein under various isolation conditions from the solution were considered. It was shown that sericin macromolecules are present as a monodisperse polypeptide at low concentrations, which aggregates at concentrations greater than 1–2 mg/ml. The obtained data indicate that, along with the parameters of the extraction process, the conditions for its isolation from the solution, including temperature, pressure and degree of concentration, affect the molecular weight and aggregative behaviour of the protein. The results confirm and complement previously obtained data on the influence of various factors on the association of protein macromolecules in solution. The resulting sericin fractions can find many applications, including materials for tissue engineering, coatings for surface modification, cell culture media, cosmetics, as well as food additives and medical biomaterials.

Dietary administration with hydrolyzed silk sericin improves the intestinal health of diabetic rats

Type II diabetes (T2D) is a global epidemic disease with an increased incidence and prevalence. Gut microbiota plays an important role in controlling T2D development. Dietary administration of prebiotics, probiotics, and drugs, including metformin, showed the regulatory impact on the change of gut microbiota, which is associated with the improvement of glucose tolerance. In this study, silk sericin was manufactured into hydrolyzed sericin peptide (HSP) powders as a dietary additive to investigate the effect on the gut microbiota of T2D model rats. The results indicated that the HSP-augmented dietary administration lowers the fast glucose level of diabetic rats, and HSP augmentation induces a change in the gut microbiota composition of T2D model rats toward the normal rats. Some key taxa, including Lactobacillus gasseri, were suggested to be involved in controlling T2D development. This finding provides new insight into developing sericin as functional food or therapeutic prebiotics against T2D in clinical practice.

Advancement in "Garbage In Biomaterials Out (GIBO)" concept to develop biomaterials from agricultural waste for tissue engineering and biomedical applications

Presently on a global scale, one of the major concerns is to find effective strategies to manage the agricultural waste to protect the environment. One strategy that has been drawing attention among the researchers is the development of biocompatible materials from agricultural waste. This strategy implies successful conversion of agricultural waste products (e.g.: cellulose, eggshell etc.) into building blocks for biomaterial development. Some of these wastes contain even bioactive compounds having biomedical applications. The replacement and augmentation of human tissue with biomaterials as alternative to traditional method not only bypasses immune-rejection, donor scarcity, and maintenance; but also provides long term solution to damaged or malfunctioning organs. Biomaterials development as one of the key challenges in tissue engineering approach, resourced from natural origin imparts better biocompatibility due to closely mimicking composition with cellular microenvironment. The "Garbage In, Biomaterials Out (GIBO)" concept, not only recycles the agricultural wastes, but also adds to biomaterial raw products for further product development in tissue regeneration. This paper reviews the conversion of garbage agricultural by-products to the biocompatible materials for various biomedical applications.

GRAPHICAL ABSTRACT

The agro-waste biomass processed, purified, modified, and further utilized for the fabrication of biomaterials-based support system for tissue engineering applications to grow living body parts in vitro or in vivo.

Silk sericin alleviates aberrant photoperiod-induced alterations in testicular and adrenal steroidogenesis in adult mice

BACKGROUND

Steroidogenesis is a complex process of sequential enzymatic reactions affected by climate change. Animals respond to altered day length, the so-called photoperiod, with changes in physiology. The study aimed to an evaluation of sericin effect in alleviating steroidogenesis disorders induced by disturbed photoperiod in mice.

METHODS

The animals were randomly divided into three groups according to the lighting cycle: a control group with a standard 12_Light:12_Dark cycle, a short-term photoperiod group with a 6_Light:18_Dark cycle, and a long-term photoperiod group with an 18_Light:6_Dark cycle. Both short and long-term groups were subdivided into two equal subgroups: The placebo and the sericin-treated subgroups received, for five weeks from prepubertal throughout adulthood, one intraperitoneal injection per week of the solvent and 1 g sericin/kg body weight, respectively.

RESULTS

Selected oxidative stress parameters and testicular and adrenal steroidogenic capacities of adult mice were measured. After five weeks, the placebo group with impaired photoperiod showed a decrease in the quality and quantity of sperm and a reduction in testosterone, corticosterone, aldosterone, total antioxidant capacity, xanthine oxidase, and melatonin. At the same time, in these groups, there was an increase in the level of aromatase, malondialdehyde, cholesterol, and steroidogenic factor-1 (SF-1) expression in the adrenal cortex and an enhancement in histological lesions. Mice receiving sericin had parameters similar to the control group.

CONCLUSION

Our findings reveal that silk sericin can reduce the stress caused by photoperiod disorders regarding testicular function, sex hormone levels, and sperm quantity and quality. Thus, sericin is a biocompatible protein with a promising potential for its use in the case of organisms living under an abnormal photoperiod.

Silk Sericin: A Promising Sustainable Biomaterial for Biomedical and Pharmaceutical Applications

Silk is a natural composite fiber composed mainly of hydrophobic fibroin and hydrophilic sericin, produced by the silkworm Bombyx mori. In the textile industry, the cocoons of B. mori are processed into silk fabric, where the sericin is substantially removed and usually discarded in wastewater. This wastewater pollutes the environment and water sources. However, sericin has been recognized as a potential biomaterial due to its biocompatibility, immunocompatibility, biodegradability, anti-inflammatory, antibacterial, antioxidant and photoprotective properties. Moreover, sericin can produce hydrogels, films, sponges, foams, dressings, particles, fibers, etc., for various biomedical and pharmaceutical applications (e.g., tissue engineering, wound healing, drug delivery, cosmetics). Given the severe environmental pollution caused by the disposal of sericin and its beneficial properties, there has been growing interest in upcycling this biomaterial, which could have a strong and positive economic, social and environmental impact.

Biosorption of rare-earth and toxic metals from aqueous medium using different alternative biosorbents: evaluation of metallic affinity

Currently, the world faces difficulties related to the quantity and quality of water because of industrial expansion, population growth, and urbanization intensification. Biosorption is considered a promising technology that can be applied to remove toxic metals (TMs) and rare-earth metals (REMs) in wastewater at low concentrations, due to its efficiency and low cost. In this work, we investigated different non-conventional biosorbents to remove metallic ions (TMs and REMs) in biosorptive affinity tests. Metallic affinity assays among lanthanum and different biosorbents showed that greater affinities were found for sericin-alginate beads crosslinked with polyvinyl alcohol (SAPVA) (0.280 mmol/g) and polyethylene glycol diglycidyl ether (SAPEG) (0.277 mmol/g), expanded vermiculite (0.281 mmol/g), Sargassum filipendula seaweed (0.287 mmol/g), and seaweed biomass waste (0.289 mmol/g). Among the biosorbents evaluated, SAPVA and SAPEG beads, besides to sericin-alginate beads crosslinked with proanthocyanidins (SAPAs) were selected for affinity assays with other REMs and TMs. Compared to other particles, SAPVA beads showed higher potential for biosorption by REMs with the following order of affinity: Yb³⁺ > Dy³⁺ > Nd³⁺ > Ce³⁺ > La³⁺. Additionally, the biosorptive affinity of TMs by SAPVA beads followed the order: Al³⁺ > Cr³⁺ > Pb²⁺ > Cu²⁺ > Cd²⁺ > Zn²⁺ > Ni²⁺.

Biomedical applications of silk and its role for intervertebral disc repair

Intervertebral disc (IVD) degeneration (IDD) is the main contributor to chronic low back pain. To date, the present therapies mainly focus on treating the symptoms caused by IDD rather than addressing the problem itself. For this reason, researchers have searched for a suitable biomaterial to repair and/or regenerate the IVD. A promising candidate to fill this gap is silk, which has already been used as a biomaterial for many years. Therefore, this review aims first to elaborate on the different origins from which silk is harvested, the individual composition, and the characteristics of each silk type. Another goal is to enlighten why silk is so suitable as a biomaterial, discuss its functionalization, and how it could be used for tissue engineering purposes. The second part of this review aims to provide an overview of preclinical studies using silk-based biomaterials to repair the inner region of the IVD, the nucleus pulposus (NP), and the IVD's outer area, the annulus fibrosus (AF). Since the NP and the AF differ fundamentally in their structure, different therapeutic approaches are required. Consequently, silk-containing hydrogels have been used mainly to repair the NP, and silk-based scaffolds have been used for the AF. Although most preclinical studies have shown promising results in IVD-related repair and regeneration, their clinical transition is yet to come.

Factors affecting sericin hydrolysis and application of sericin hydrolysate in sericin films

Sericin is a natural protein and a by-product obtained from silk processing. To enhance the antioxidant properties of sericin, sericin hydrolysis was studied. The solvent effects (distilled water, citric acid and hydrochloric acid) and hydrolysis methods (heat treatment (water bath) and mild ultrasonic treatment at 20%, 40% or 60% amplitude) were investigated on the properties of sericin hydrolysate (SH). Furthermore, solvent effects (distilled water and 15% ethanol) were examined for the properties of the sericin films incorporated with selected SH. The SH samples from acid hydrolysis and the ultrasonic method had a darkened visual appearance. However, the degree of hydrolysis and antioxidant activity of SH increased with ultrasonic-assisted acid hydrolysis. The molecular weight (MW) of sericin was notably reduced. As expected, hydrochloric acid hydrolysis resulted in a lower MW for the SH than from citric acid. Thus, SH from hydrochloric acid and 20% amplitude in the ultrasonic method were selected to produce a sericin film. As revealed, using distilled water as a general solvent provided films with lower solubility and water vapor permeability but higher tensile strength. Furthermore, the addition of SH enhanced the antioxidant properties of its hydrolysate as a novel protein packaging film material for various applications.

Bombyx mori cocoon as a promising pharmacological agent: A review of ethnopharmacology, chemistry, and biological activities

Silk cocoon, naturally produced by silkworms scientifically named Bombyx mori L. (Lepidoptera, Bombycidae), is one of the well-known medicinal agents with several therapeutic activities. The present study aims to review the various aspects of the silk cocoon, including chemical composition, traditional uses, biological and biotechnological activities, and toxicological issues, to provide a scientific source for scholars. For this purpose, Electronic databases including PubMed, Scopus, Google Scholar, Web of Science, and traditional literature, were searched up to December 2021. According to the historical data, silk farming is acknowledged as one of the most ancient agricultural findings. The silk is generally composed of 75–83% fibroin, 17–25% sericin, and 1–5% non-sericin components, including secondary metabolites, wax, pigments, carbohydrates, and other impurities. Flavonoids, especially quercetin and kaempferol, alkaloids, coumarin derivatives, and phenolic acids, are among the secondary metabolites isolated from the silk cocoon. In recent years the biological properties of the silk cocoon, especially its major proteins, namely fibroin and sericin, have drawn special attention. Scientific literature has investigated several pharmacological effects of the silk cocoon and its ingredients, including cardioprotective, antioxidant, anticancer, antidiabetic, antihyperlipidemia, gastroprotective, as well as ameliorated skin health activities. In addition, it has been extensively taken into consideration in drug delivery and tissue engineering study fields. Furthermore, its toxicity is in acceptable range.

Silk sericin-based materials for biomedical applications

Silk sericin, a natural protein extracted from silkworm cocoons, has been extensively studied and utilized in the biomedical field because of its superior biological activities and controllable chemical-physical properties. Sericin is biocompatible and naturally cell adhesive, enabling cell attachment, proliferation, and differentiation in sericin-based materials. Moreover, its abundant functional groups from variable amino acids composition allow sericin to be chemically modified and cross-linked to form versatile constructs serving as alternative matrixes for biomedical applications. Recently, sericin has been constructed into various types of biomaterials for tissue engineering and regenerative medicine, including various bulk constructions (films, hydrogels, scaffolds, conduits, and devices) and micro-nano formulations. In this review, we systemically summarize the properties of silk sericin, introduce its different forms, and demonstrate their newly-developed as well as potential biomedical applications.

Efficient and recyclable sericin-derived carbon aerogel for oils and organic solvents adsorption

Sericin, an industrial waste of the silk industry, is a promising precursor for adsorbent preparation. In this work, an efficient and novel sericin-derived carbon aerogel (SCA) was used to improve the adsorption efficiency of oils and organic solvents. The SCA demonstrated a high-efficiency sorption capacity of not only soybean oil (adsorption capacity reached up to 167.69 times its weight) but also chloroform and methylene chloride (adsorption capacity of 193.67 g/g and 173.25 g/g respectively). It is observed that SCA could be regenerated multiple times through combustion and after five cycles, its adsorbability to ethanol, dimethyl sulfoxide, and soybean oil remained high at 59.08 g/g, 59.34 g/g, and 137.36 g/g, respectively. The physical and chemical characteristics of sericin and SCA were analyzed using Scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Raman spectra and Fourier transform infrared spectroscopy (FTIR) analysis. The results suggest that SCA is an adsorbent with excellent properties and can significantly increase the adsorption capacity of oils and organic solvents. The overall results indicate that SCA is effectively used as an adsorbent for the adsorption of oils and organic solvents, which will contribute to reduce the discharge of sericin-containing wastewater and alleviate pollution caused by oil and organic solvent leakage.

Biocompatible fluorescent silk fibroin bioink for digital light processing 3D printing

Chemically modified silk fibroin (SF) bioink has been used for three-dimensional (3D) bioprinting in tissue engineering because of its biocompatibility and printability. Also, fluorescent silk fibroin (FSF) from transgenic silkworms has been recently applied in biomedicine because of its fluorescence property. However, the fabrication of fluorescent hydrogel from FSF has not been elucidated. In this study, we showed the fabrication of a digital light processing (DLP) printable bioink from a chemically modified FSF. This bioink was fabricated by covalent conjugation of FSF and glycidyl methacrylate (GMA) and can be printed into various structures, such as the brain, ear, hand, lung, and internal organs. The physical properties of glycidyl methacrylated fluorescent silk fibroin (FSGMA) hydrogel was like the glycidyl methacrylated non-fluorescent silk fibroin (SGMA) hydrogel. The FSGMA hydrogel significantly retains its fluorescence property and has excellent biocompatibility. All these properties make FSGMA hydrogel a potent tool in encapsulated cell tracking and observing the scaffolds' degradation in vivo. This study suggested that our 3D DLP printable FSF bioink could play a promising role in the biomedical field.

Study of the Antioxidative Effects of Bombyx mori Silk Sericin in Cultures of Murine Retinal Photoreceptor Cells

The availability of natural substances able to fulfill the role of antioxidants in a physiologic environment is important for the development of therapies against diseases associated with excessive production of reactive oxygen species and ensuing oxidative stress. Antioxidant properties have been reported episodically for sericin, a proteinaceous constituent of the silk thread in the cocoons generated by the larvae of the Lepidoptera order. We investigated the sericin fractions isolated from the cocoons spun by the domesticated (Bombyx mori) silkworm. Three fractions were isolated and evaluated, including two peptidoid fractions, the crude sericin and the purified (dialyzed) sericin, and the non-peptidoid methanolic extract of the crude fraction. When subjected to Trolox equivalent antioxidant capacity (TEAC) assay, the extract showed much higher antioxidant capacity as compared to the crude or purified sericin fractions. The three fractions were also evaluated in cultures of murine retinal photoreceptor cells (661 W), a cell line that is highly susceptible to oxidants and is crucially involved in the retinopathies primarily caused by oxidative stress. The extract displayed a significant dose-dependent protective effect on the cultured cells exposed to hydrogen peroxide. In identical conditions, the crude sericin showed a certain level of antioxidative activity at a higher concentration, while the purified sericin did not show any activity. We concluded that the non-peptidoid components accompanying sericin were chiefly responsible for the previously reported antioxidant capacity associated with sericin fractions, a conclusion supported by the qualitative detection of flavonoids in the extract but not in the purified sericin fraction.

Progress in recycling and valorization of waste silk

Due to the improvements in living standards and the "throw away" culture of mankind, large amount of waste textiles is constantly generated. In particular, silk is an abundant high-grade textile material with characteristics of wear comfort, high profit, and low supply with high demand, but it transforms into waste when discarded. This paper reviews the current progress of recycling and reuse of waste silk from the aspects of energy, yarn and fabric, reinforcement of composites, silk fibroin, biological tissue engineering, filtration of air and water, and electrode. The modification, optimization and application of regenerated silk fibroin extracted from waste silk are promising to industrialization and sustainable development. Making waste silk functional and intelligently wearable are two ways of recycling waste silk with low cost and high return value in the near future. The recovery and utilization of waste silk provide a paradigm for valorization of other fiber-based waste such as wool, cotton, bast and synthetic fibers.

Bibliometric Analysis of Trends in Mulberry and Silkworm Research on the Production of Silk and Its By-Products

Simple Summary

Over the past two decades scientific research on sericulture, the agricultural activity of silk production, generated a great number of outputs in the form of articles reported and classified by one of the most well-known and used database dealing with scientific literature. This occurrence demonstrates an increasing interest in this sector especially starting from 2000s; results presented in relevant papers showed their applicability even in fields apparently not related to silk production as commonly meant, like medicine, cosmetics, and engineering. To understand how sericulture has been transcending its usual boundaries, which are its current “hotspots”, and links with other fields of study, the authors propose a text-mining based analysis of the outputs of scientific research on sericulture and silk; the final goal is to establish “quantitative” indicators for researchers, entrepreneurs, and scholars.

Abstract

Traditionally, sericulture is meant as the agricultural activity of silk production, from mulberry (Morus sp.pl.) cultivation to silkworm (Bombyx mori L.) rearing. The aim of the present work is to analyze the trends and outputs of scientific research on sericulture-related topics during the last two decades, from 2000 to 2020. In this work the authors propose a text-mining analysis of the titles, abstracts and keywords of scientific articles focused on sericulture and available in the SCOPUS database considering the above-mentioned period of time; from this article collection, the 100 most recurrent terms were extracted and studied in detail. The number of publications per year in sericulture-related topics increased from 87 in 2000 to 363 in 2020 (+317%). The 100 most recurrent terms were then aggregated in clusters. The analysis shows how in the last period scientific research, besides the traditional themes of sericulture, also focused on alternative products obtainable from the sericultural practice, as fruits of mulberry trees (increment of +134% of the occurrences in the last five years) and chemical compounds as antioxidants (+233% of occurrences), phenolics (+330% of occurrences) and flavonoids (+274% of occurrences). From these considerations, the authors can state how sericulture is an active and multidisciplinary research field.

Wound dressing adherence: a review

Wound dressing adherence is an important problem that is frequently encountered in wound care, and is associated with both clinical and economic burdens. However, only a few review articles have focused on this issue. The objective of this review was to present a comprehensive discussion of wound dressing adherence, including the mechanism of dressing adherence, adverse consequences (clinical burdens and economic burdens), factors affecting adherence (dressing-, patient- and wound-related factors, and factors related to the wound care procedure), tests to assess dressing adherence (in vitro assay, in vivo assay and clinical trials), and reduction of wound adherence (modification of dressing adherence and special care in particular patients). Accordingly, this review article emphasises an awareness of dressing adherence, and is intended to be an informative source for the development of new dressings and for wound management.

Screen-Printed Carbon Black/Recycled Sericin@Fabrics for Wearable Sensors to Monitor Sweat Loss

Wearable sensors to monitor human sweat loss are important for real-time health monitoring, requiring electrically conductive, mechanically flexible fabrics as working electrodes. Here, a textile-based sweat monitor was fabricated by screen printing of carbon black and recycled sericin on cotton fabrics. The obtained fabric with excellent flexibility, good hydrophilicity (86°), and proper resistivity (61.7 Ω/cm²) can be used as a working electrode for a wearable sweat monitor. A wearable sweat monitor is highly sensitive (42.7% in acidic sweat), flexible, and can be washed (99.1% retention after 30 washes). This work offers a promising approach for the fabrication of wearable sensors and promotes the widespread applications of personalized health-monitoring devices.

Genetically engineered FGF1-sericin hydrogel material treats intrauterine adhesion and restores fertility in rat

Endometrial injury can cause intrauterine adhesions (IUA) and induce the formation of endometrial fibrosis, leading to infertility and miscarriage. At present, there is no effective treatment method for severe IUA and uterine basal injury with adhesion area larger than 1/3 of the uterus. In this study, we prepared FGF1 silk sericin hydrogel material (FGF1-SS hydrogel) to treat endometrial injury and prevent endometrial fibrosis. Compared with the silk sericin hydrogel material (WT-SS hydrogel), FGF1-SS hydrogel significantly promotes the cell migration and infiltration ability of endometrial stromal cells (ESCs). More importantly, FGF1-SS hydrogel can release FGF1 stably for a long time and inhibit The ESCs injury model forms fibrosis through the TGF-β/Smad pathway. In the IUA rat model, FGF1-SS hydrogel treatment effectively restored the number of uterine glands and uterine wall thickness in rats, with a fertility rate of 65.1 ± 6.4%. The results show that FGF1-SS hydrogel is expected to be a candidate to prevent IUA.

Dual-functional bioactive silk sericin for osteoblast responses and osteomyelitis treatment

Sericin, a natural protein from silk cocoon, has been reported for various biological properties in the biomaterials field. Modified forms of sericin have been studied for bone tissue engineering, while its unmodified form has been scarcely reported. Therefore, the purpose of this study was to evaluate physical and biological properties of unmodified sericin for potential use in bone surgery. Sericin was extracted from silk cocoons using a chemical-free boiling method. Sericin extract showed distinct bands with molecular weight ranging from 25 to 42 kDa including smear bands. Fourier transform infrared spectra presented characteristic peaks of amide I, II, and III, confirming the chemical composition of sericin. Based on biological activity, sericin extract at a concentration of 40 μg/mL increased the proliferation of osteoblast cells up to 135%, compared with the untreated control. Moreover, increase in antibacterial activity against Staphylococcus aureus, both clinical isolates and the reference strain ATCC 29213, was demonstrated for sericin extract with normal saline, while no antibacterial activity was observed for sericin with broth. It was found that sericin with normal saline showed higher zeta potential than sericin without normal saline, indicating higher system stability. This was confirmed by the average particle size of sericin extract with NaCl (3,249.3±226.1 nm) showing approximately 10 times smaller than sericin solution (29,015.9 ± 8,085.6 nm). Furthermore, sericin extract at the minimal inhibitory concentration significantly reduced the biofilm formation of S. aureus up to 95%. The study indicates biological activities of sericin, which could be applied as a dual-functional bioactive material to support bone regeneration and treat bone infections.

Silk Sericin Enrichment through Electrodeposition and Carbonous Materials for the Removal of Methylene Blue from Aqueous Solution

The recycling and reuse of biomass waste for the preparation of carbon-based adsorbents is a sustainable development strategy that has a positive environmental impact. It is well known that a large amount of silk sericin (SS) is dissolved in the wastewater from the silk industry. Utilizing the SS instead of discharging it into the environment without further treatment would reduce environmental and ecological problems. However, effective enrichment of the SS from the aqueous solution is a challenge. Here, with the help of carboxymethyl chitosan (CMCS), which can form a gel structure under low voltage, an SS/CMCS hydrogel with SS as the major component was prepared via electrodeposition at a 3 V direct-current (DC) voltage for five minutes. Following a carbonization process, an SS-based adsorbent with good performance for the removal of methylene blue (MB) from an aqueous solution was prepared. Our results reveal that the SS/CMCS hydrogel maintains a porous architecture before and after carbonization. Such structure provides abundant adsorption sites facilitating the adsorption of MB molecules, with a maximum adsorptive capacity of 231.79 mg/g. In addition, it suggests that the adsorption is an exothermic process, has a good fit with the Langmuir model, and follows the intra-particle diffusion model. The presented work provides an economical and feasible path for the treatment of wastewater from dyeing and printing.

A Targeted In-Fusion Expression System for Recombinant Protein Production in Bombyx mori

The domesticated silkworm, Bombyx mori, is an economically important insect that synthesizes large amounts of silk proteins in its silk gland to make cocoons. In recent years, germline transformation strategies advanced the bioengineering of the silk gland as an ideal bioreactor for mass production of recombinant proteins. However, the yield of exogenous proteins varied largely due to the random insertion and gene drift caused by canonical transposon-based transformation, calling for site-specific and stable expression systems. In the current study, we established a targeted in-fusion expression system by using the transcription activator-like effector nuclease (TALEN)-mediated targeted insertion to target genomic locus of sericin, one of the major silk proteins. We successfully generated chimeric Sericin1-EGFP (Ser-2A-EGFP) transformant, producing up to 3.1% (w/w) of EGFP protein in the cocoon shell. With this strategy, we further expressed the medically important human epidermal growth factor (hEGF) and the protein yield in both middle silk glands, and cocoon shells reached to more than 15-fold higher than the canonical piggyBac-based transgenesis. This natural Sericin1 expression system provides a new strategy for producing recombinant proteins by using the silkworm silk gland as the bioreactor.

Bio-derived and biocompatible poly(lactic acid)/silk sericin nanogels and their incorporation within poly(lactide-co-glycolide) electrospun nanofibers

Bio-derived and biocompatible nanogels based on poly(lactic acid) (PLA) and silk sericin (SS) have been synthesized for the first time.

Nano-Bio-engineered Silk Matrix based Devices for Molecular Bioanalysis

Silk is a fibrous protein, has been a part of human lives for centuries and was used as suture and textile material. Silk is mainly produced by members of certain arthropods such as spiders, butterflies, mites, and moths. However, recent technological advances have revolutionized silk as a biomaterial for various applications ranging from heat sensors to robust fibers. The biocompatibility, mechanical resilience, and biodegradability of the material make it a suitable candidate for biomaterials. Silk can also be easily converted into several morphological forms, including fibers, films, sponges, and hydrogels. Provided these abilities, silk have received excellent traction from scientists worldwide for various developments, one of them being its use as a bio-sensor. The diversity of silk materials offers various options, giving scientists the freedom to choose from and personalize them as per their needs. In this review, we foremost look upon the composition, production, properties, and various morphologies of silk. The numerous applications of silk and its derivatives for fabricating biosensors to detect small molecules, macromolecules, and cells have been explored comprehensively. Also, the data from various globally developed sensors using silk have been described into organized tables for each category of molecules, along with their important analytical details. This article is protected by copyright. All rights reserved.

Silk fibroin and sericin polymer blends for sustainable battery separators

Natural polymers are a promising alternative for reducing the environmental impact of batteries. For this reason, it is still necessary to study their behavior and implement its use in these devices, especially in separator membranes. This work reports on new separator membranes based on silk fibroin (SF) and silk sericin (SS) prepared by salt leaching method. The effect of the different SS relative content on the physiochemical properties of the membranes and on the electrochemical performance of the corresponding batteries with lithium iron phosphate (LFP) as cathodes has been reported. It is observed that the increasing of SS content leads to a decrease of the overall crystallinity of the membranes. All SF/SS membranes presented a well-defined porosity above 75% with a uniform distribution of interconnected micropores. The electrolyte uptake and the ionic conductivity are dependent on the relative SS content. The addition of 10 wt% of SS into SF membranes, induce a high ionic conductivity of 4.09 mS.cm^-1 and high lithium transference number (0.52), due to the improvement of the Li⁺ ions conduction paths within the blended structure. Charge/discharge tests performed in Lithium/C-LFP half-cells reveal a discharge capacity of 85 mAh.g^-1 at 2C after 100 cycles for batteries with a SF/SS separator, containing a 10 wt% of SS, which suggests a stabilizing effect of Sericin on discharge capacity. Further, a 50% and 35% of capacity of retention and capacity fade, respectively, is observed. The presented SF/SS membrane show high electrochemical stability, being suitable for implementation in a next generation of sustainable battery systems. This could allow the SS valorization considering that 150,000 tons of SS are abandoned each year, reducing the contamination of environmental effluents.

Biomedical applications of silkworm (Bombyx Mori) proteins in regenerative medicine (a narrative review)

Silk worm (Bombyx Mori) protein, have been considered as potential materials for a variety of advanced engineering and biomedical applications for decades. Recently, silkworm silk has gained significant importance in research attention mainly because of its remarkable and exceptional mechanical properties. Silk has already been shown to have unique interactions with cells in tissues through bio-recognition units. The natural silk contains fibroin and sericin and has been used in various tissues of the human body (skin, bone, nerve, and so on). Besides, silk also still has anti-cancer, anti-tyrosinase, anti-coagulant, anti-oxidant, anti-bacterial, and anti-diabetic properties. This article is supposed to describe the diverse biomedical capabilities of B. Mori silk as the appropriate biomaterial among the assorted natural and artificial polymers that are presently accessible, and ideal for usage in regenerative medicine fields.