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Two types of sericin peptides with high molecular weight (HS) and low molecular weight (LS) were obtained by the green water boiling ultrasonic method and the Ca(OH)2 ultrasonic method, respectively. In this experiment, a high-glucose medium was used to simulate a high-glucose environment in the body, and appropriate concentrations of normal alpha mouse liver 12 (AML12) hepatocytes were exposed to a series of concentrations of HS and LS. The effects of the two sericin peptides on AML12 cells in a high-glucose environment were investigated in detail in terms of oxidative stress and inflammatory factor expression in cells. HS and LS-groups reduced the levels of oxidative stress, inflammation, and tumor necrosis factor (TNF), and the latter significantly reduced the levels of TNF-α, interleukin (IL)-6, and nuclear factor (NF)-κB in AML12 cells. Additionally, it significantly reduced the oxidative stress damage caused by the high-glucose environment compared with normal AML12 cells. These results indicate that sericin may be an antioxidant recovered from industrial waste, and has potential and for use in the reduction of environmental pollution and the development of functional foods with antioxidation and antihyperglycemic effect. [ABSTRACT FROM AUTHOR]

In the sericulture and silk production industry, sericin is discharged in the degumming wastewater, resulting in a large amount of wasted natural protein and environmental pollution. This study investigated the effect of degraded sericin recovered by the Ca(OH)2–ultrasound degumming method (a green process) on liver injury in T2D rats. After 4 weeks of dietary sericin supplementation, the liver masses and organ coefficients of the T2D rats improved compared with those of the model rats that were not fed sericin. Oral sericin activated the damaged PI3K/AKT/AMPK pathway to enhance glycogen synthesis, accelerate glycolysis, and inhibit gluconeogenesis. The protein expression levels of the inflammatory factors NF-κB, IL-6, and TNF-α in the T2D model group were up to two times higher than in the normal group. However, all three T2D groups that received oral sericin showed significant decreases in these factors to the level found in the normal group, indicating that inflammation in the body was significantly reduced. These results show that the sericin protein might improve glycogen synthesis, accelerate glycolysis, and inhibit gluconeogenesis by enhancing the anti-oxidation capability and reducing inflammatory reactions. Therefore, sericin recovered by Ca(OH)2 degradation has potential use in the development of functional health foods that can lower blood sugar. [ABSTRACT FROM AUTHOR]

A sodium N-lauryl amino acids (shortly silk sericin surfactant, SSS) is synthesized with lauryl chloride and sericin amino acids recovered from silk industrial waste. The purpose of this study is to explore whether the sericin surfactant can be used as a potential drug delivery carrier. By controlling the proportion of cationic drugs, cytarabine hydrochloride (CH) and anionic SSS, the aggregation behavior, slow release capability and toxicological effects of catanionic aggregates or vesicles, formed through CH and SSS, have been investigated in detail. Dynamic light scattering (DLS), transmission electron microscopy (TEM), and zeta potential analysis showed that the aggregate solution could form a stable vesicle structure when the mass fraction of CH is less than or equal to 0.3. The drug release results showed that the cumulative release rate of the catanionic aggregation solution with CH mass fraction of 0.2 reached a maximum at 18 h, being approximately 9 times greater than that of pure cytarabine. The CH/SSS aggregates had a significant sustained release effect compared with the control group. At the same time, vesicles formed by SSS and CH have better anti-tumor effects compared with the pure drug group. In summary, sericin surfactant from silk industrial waste has a potential use as a drug delivery carrier. [ABSTRACT FROM AUTHOR]

Silk sericin (SS) with various biological activities has limited solubility in water and unpleasant pupal odor, which hinder its wide application in functional foods. Here, a high-yield Maillard reaction (MR) product, glycated sericin, was obtained at a concentration of 60–10 mg/mL with 18–30 mg/mL reducing sugar in a pH 10.0 aqueous solution at 90 °C for 6 h. Xylose had the highest reaction efficiency and the most obvious browning among the seven reducing sugars, followed by arabinose sugar and glucose. No matter what kind of sericin and what kind of reducing sugar, the solubility of the glycated sericin in water increased 2–3 times, and the antioxidant capacity increased 3.5–5.5 times. In particular, glycation of the sericin eliminated the pupal odor of SS and replaced it with a slightly sweet mellow fragrance. Therefore, sericin glycation opens up broad application as a health food, functional food, or food additive. • Silk sericin has various biological activities and pharmacological effects. • Limited water solubility and unpleasant odor hinder its application to health foods. • Glycated sericin improves water solubility and has a mellow and sweet fragrance. • Sericin glycation will open broad its application in health and functional foods. [ABSTRACT FROM AUTHOR]

Bombyx mori silk is composed of 60–80% fibroin, 15–35% sericin and 1–5% non-sericin component including wax, pigments, sugars and other impurities. For two decades, the protein-based silk fibroin was extensively used in the research and development of medical biomaterials and biomedicines. Sericin is frequently ignored and abandoned as a byproduct or waste in the processing of traditional silk fabrics, silk floss or modern silk biomaterials. However, similar to fibroin, sericin is not only a highly useful biological material, but also a lot of biological activity. Moreover, the non-sericin component present with sericin in the cocoon shell also has a strong biological activity. In this review, the extraction and recovery methods of sericin and the non-sericin component from the cocoon layer are reported, and their composition, properties and biological activity are described to produce a comprehensive report on biomedical materials and biological drugs. In addition, related problems or concerns present in the research and development of sericin are discussed, and a potential application of sericin in sustainable development is also presented. [ABSTRACT FROM AUTHOR]

Strongly alkaline electrolyzed water (SAEW) was used as a sericin swelling agent for silk reeling from cocoons of the silkworm Bombyx mori. Tap water was electrolyzed with a laboratory-made combined water electrolyzer to generate SAEW with pH 11.50. The hardness of SAEW was 30% less than that of the tap water, whereas the concentrations of Na+ in SAEW were 18% higher than those in the tap water. The pH of the SAEW was stable for at least a month in an airtight container. Cocoons were immersed in pH 11.50 SAEW for 15 min with shaking, which replaces one step of the complex cocoon cooking process in the traditional reeling method (TRM) where penetration is achieved by repeatedly alternating high and low temperatures. The swollen cocoons were transferred into fresh pH 11.50 SAEW for reeling at the same, or slightly lower, temperature. The sericin loss from the whole cocoon in pH 11.50 SAEW is about 3.5% and the tensile property of the single silk fibroin filament is similar to or better than that of TRM. Silk reeling in SAEW involves only one step of cocoon swelling in pH 11.50 SAEW (70°C), which replaces a series of complex processes including water penetration, water absorption, swelling, and then silk reeling in the TRM. A novel low-temperature and simple reeling technology suitable for development by the silk industry is described. [ABSTRACT FROM AUTHOR]

Two sericins of high and low molecular weight (HS and LS) were prepared from commercial silkworm cocoon silk with a boiling water and Ca(OH)2 solution with ultrasonic treatments, respectively. This study first investigated the release concentration of the two abovementioned sericins in simulated saliva, gastric juice, and intestinal juice (pH 6.8, 2.0, and 7.4, respectively) within 10 h. The results showed that the order of sericin release rate and its amount in the simulated environment was gastric juice > saliva > intestinal juice. Second, the molecular weights of both sericin metabolites formed by in vitro enzymatic degradation were lower than 15 kDa. The α-glucosidase inhibitory activities of both sericins and their analog metabolites were positively correlated with their concentrations. The IC50 values of the HS- and LS-derived metabolites were 1.02 ± 0.12 mg/mL and 0.91 ± 0.15 mg/mL, respectively, which were five to seven times lower than those of both original sericins. The total antioxidant capacities and hydroxyl radical scavenging capacities of both metabolites were enhanced by one- to three-fold compared with HS and LS. These results indicate that both sericins, regardless of molecular size, have significantly enhanced antioxidant, superoxide free radical scavenging, and glycosidase inhibitory activities after simulated metabolism, and that LS is better than HS regardless of simulated digestion. These results confirm that sericin is important in the sustainable development and utilization of silk resources, especially the reduction in environmental pollution, and provides new ideas for the development of adjuvant treatments for diabetes and the development of foods with anti-hyperglycemic functions. [ABSTRACT FROM AUTHOR]

This paper describes the use of silk protein, including fibroin and sericin, from an alkaline solution of Ca(OH)2 for the clean degumming of silk, which is neutralized by sulfuric acid to create calcium salt precipitation. The whole sericin (WS) can not only be recycled, but completely degummed silk fibroin (SF) is also obtained in this process. The inner layers of sericin (ILS) were also prepared from the degummed silk in boiling water by 120 °C water treatment. When the three silk proteins (SPs) were individually grafted with glycidyl methacrylate (GMA), three grafted silk proteins (G-SF, G-WS, G-ILS) were obtained. After adding I2959 (a photoinitiator), the SP bioinks were prepared with phosphate buffer (PBS) and subsequently bioprinted into various SP scaffolds with a 3D network structure. The compressive strength of the SF/ILS (20%) scaffold added to G-ILS was 45% higher than that of the SF scaffold alone. The thermal decomposition temperatures of the SF/WS (10%) and SF/ILS (20%) scaffolds, mainly composed of a β-sheet structures, were 3 °C and 2 °C higher than that of the SF scaffold alone, respectively. The swelling properties and resistance to protease hydrolysis of the SP scaffolds containing sericin were improved. The bovine insulin release rates reached 61% and 56% after 5 days. The L929 cells adhered, stretched, and proliferated well on the SP composite scaffold. Thus, the SP bioinks obtained could be used to print different types of SP composite scaffolds adapted to a variety of applications, including cells, drugs, tissues, etc. The techniques described here provide potential new applications for the recycling and utilization of sericin, which is a waste product of silk processing. [ABSTRACT FROM AUTHOR]

Silk sericin is a natural macromolecular protein derived from silkworm Bombyx mori. During the various stages of producing raw silk and textile, sericin can be recovered for other uses. Also, sericin recovery reduces the environmental impact of silk manufacture. Sericin protein is useful because of its properties. The protein resists oxidation, is antibacterial, UV resistant, and absorbs and releases moisture easily. Sericin protein can be cross-linked, copolymerized, and blended with other macromolecular materials, especially artificial polymers, to produce materials with improved properties. The protein is also used as an improving reagent or a coating material for natural and artificial fibers, fabrics, and articles. The materials modified with sericin and sericin composites are useful as degradable biomaterials, biomedical materials, polymers for forming articles, functional membranes, fibers, and fabrics. [Copyright &y& Elsevier]

Sericin could be degraded well into low-molecular-weight sericin (SS) through a novel and environmentally friendly recycling process using an ultrasonically degumming method in Ca(OH)2 aqueous solution. The oral administration of the SS has an evidently hypoglycemic effect on STZ-induced T2D rats. At oral doses of 2.5 and 5% SS for four weeks, the fasting blood glucose decreased by over 60% compared with that in the untreated model group. Oral glucose tolerance and insulin tolerance were ameliorated by the peptide treatment. The serum insulin level was reduced by approximately 35%, the insulin resistance index was reduced by more than 66%. The 8-hydroxy-2 deoxyguanosine level showed a large reduction of 20%, and the total antioxidant activities significantly increased. Hematoxylin-eosin staining and fluorescent immunostaining sections showed that liver and pancreas damage was partly recovered in T2D rats. In summary, oral SS demonstrated evidently hypoglycemic effects mainly related to reducing oxidative stress in the damaged liver and pancreas of T2D rats. Therefore, these results have suggested that the degraded sericin has a potential use in SS-based healthy functional food or hypoglycemic drugs as a waste recovered from sericulture resources. [ABSTRACT FROM AUTHOR]

The greener degumming method not only affects evidently the mechanical properties and uses of silk fibroin fiber, but also involves in some interesting issues including the recovery and utilization of sericin in a large number of alkaline degumming waste solutions. To this day, it remains one of the key issues deeply trouble us for the silk processing industry. Here, we systematically reported that three kinds of greener degumming methods could extract the outer-layered (OLS), inner-layered (ILS) and whole (WS) sericin peptides, respectively. Among them, the degumming method by using calcium hydroxide (CH) had an obvious advantage that the whole sericin (WS) could be fully recycled by neutralizing with sulfuric or phosphoric acid. The results show that the degumming ratios of OLS, ILS and WS were 11.4%, 16.65% and 28.61%, respectively. Three sericin peptides had evident differences from physicochemical properties and bioactivities in vitro. OLS obtained from boiling water had the highest in molecular weight (≥30 kDa), and both its antioxidation and antibacterial activities were higher than those of ILS extracted under 120 °C water for 2 h. ILS contains more β-sheet structures and its thermal decomposition temperature is approximately 14 °C higher than that of OLS. Almost the same as or higher than glycerin, the hygroscopic capacity of OLS in 160 h and the moisturizing properties of WS in 100 h reach about 32% and 50%, respectively. Furthermore, the WS had the lowest in molecular weight and stronger tyrosinase inhibitory activity and all samples had α-glucosidase inhibitory activity. Therefore, these cleaner production methods for silk degumming can result in three sericin peptides, of which OLS and ILS have potential applications and developmental value in the fields of medical biomaterials, and WS is preferable to biopharmaceuticals, cosmetics, and advanced health foods. • Greener degumming methods could extract outer-layered (OLS), inner-layered (ILS) and whole (WS) sericin from silk. • When Ca(OH) 2 as silk degumming agent, the purified WS and calcium could be recycled by neutralizing with sulfuric acid. • The three sericin peptides exhibited significant differences from physicochemical properties and bioactivities in vitro. • OLS and ILS have potential uses in biomaterials and covering materials, WS is preferable to functional food and biodrugs. [ABSTRACT FROM AUTHOR]

The silk sericin hydrolysate (SSH) from the waste of silk processing as a substitute of fetal bovine serum (FBS) was used for the culture of Chinese hamster ovary (CHO) cells and Henrietta Lacks (Hela) strain of human cervical cancer cells. The survival ratio of these cells cultured in SSH media were similar to or higher than those in FBS media. Especially after the serum was replaced by low concentration of SSH at 15.0 μg/ml for 5 d, the proliferation of both cells was also similar to or higher than that of FBS group; the percentages of CHO and Hela cells in S-phase were 28.9 and 28.0%, respectively. The former is nearly two times that of FBS group, the latter is also higher than the control group. Reverse transcription-polymerase chain reaction (RT-PCR) revealed that among the differentially expressed genes, the relative expression of CXCL12 gene of CHO cells in SSH group increased, was three times that of serum group, and the relative expression of LCN2 gene of Hela cells increased 2.8 times, indicating that these related genes were activated to promote cell growth and proliferation. These results fully illustrated the hydrolysated sericin has a potential use as serum substitutes in cell culture. [ABSTRACT FROM AUTHOR]

The high molecular weight sericin recovered by using degumming method of high-temperature and high-pressure water was subjected to a Maillard reaction (MR) with xylose, and the resulting xylosylated sericin (XS) has good water solubility. A mechanically robust, soft, and transparent PVA hydrogel composite membrane (PVA-XS) was obtained by mixing XS (20 w%) into an aqueous PVA solution based on unidirectional nanopore dehydration (UND). The mechanical strength, elongation, and elastic modulus of PVA-XS reached 1.68 MPa, 519.83%, and 0.27 MPa, respectively. UND at 85 °C yielded a hydrogel composite membrane with stronger mechanical properties; these values were 9.94 MPa, 627.20%, and 1.49 MPa. These composite hydrogels have 3D porous structures with pore sizes ranging from 2 to 20 μm, and there was no phase separation. Murine L-929 cells adhered, grew, and proliferated normally on the scaffold. The digestion rates of PVA-XS in both trypsin and alkaline protease were faster than that of high temperature-annealed cast PVA-XS (acPVA-XS). Implantation in vivo did not induce an obvious tissue immune response. The mechanical properties and enzymatic degradation rate of PVA-XS were controlled by UND temperature and XS incorporation. Therefore, the UND-based composite hydrogel has potential applications in the implantation, repair, and regeneration of biological tissues. • The glycation of the high molecular weight sericin peptides with xylose can enhance its water-soluble. • A mechanically robust, soft, and transparent PVA-glycated sericin membrane (PVA-XS) was obtained based on UND. • The UND temperature and XS incorporation could control the mechanical properties and enzymatic degradation rate of PVA-XS. • The UND-based composite hydrogel has potential applications in biological tissue engineering. [ABSTRACT FROM AUTHOR]

Abstract: This study was designed to improve the traditional scouring procedure using a solution of sodium silicate, sodium carbonate, H2O2, surfactant etc. as a refining agent for degumming machine-drawn raw silk sheet (RSS) and raw silk from the cocoon shell of the silkworm Bombyx mori. The RSS was scoured firstly in strongly alkaline electrolyzed water (SAEW, pH ≥ 11.5) consisting mainly of hydroxyl ions by boiling for 30 min and then treated by the traditional scouring procedure (without alkaline compounds), resulting in refined silk floss. The recycled SAEW containing sericin was separated by ultrafiltration into a retentate with a range of high molecular mass values accounting for 10% (w/w) of the cocoon shell and the filtrate was separated by nanofiltration into a purified H2O filtrate and a retentate containing oligopeptides and free amino acids, which can be used directly as food additives or in biological growth media. The ultrafiltration retentate was hydrolyzed by papain under three different conditions into three groups of sericin peptides with high, middle or low molecular mass. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and gel permeation high-performance liquid chromatography (GP-HPLC) showed the molecular mass of these sericin peptides was in the range 0.2–60, 0.2–30 and 0.2–15 kDa. These clean products have a variety of applications, including coating materials for surface modification, cell culture media and food additives. The procedure described here could be applied to the manufacture of silk floss quilts and the process of refining raw silk, which results in three clean products of the silk protein fibroin (i.e. stripped of sericin) and reduces environmental pollution from scouring waste containing sericin. [Copyright &y& Elsevier]

• Silk sericin, a biomacromolecule, is recovered from silk processing-waste. • Silk sericin is used as an additive in cell culture, cosmetic and health food. • Oral sericin evidently enhanced antioxidation and anti-inflammation. • Sericin improves blood glucose levels & insulin resistance via PI3K/P-AKT/AMPK pathways. • Sericin protein is a potentially functional additive for hypoglycaemic food. The sericin protein from silk-processing waste added to the normal diet at 0.8% (g%) level was administered orally to type 2 diabetic (T2D) mice to investigate its hypoglycaemic effects and mechanism. The oral protein is in the form of silk sericin hydrolysate, obtained from a boiling treatment of 0.025% calcium hydroxide solution. The protein significantly decreased fasting blood glucose, fasting plasma insulin, and glycosylated serum protein levels; improved oral glucose tolerance and insulin tolerance, and enhanced antioxidative activities. The protein could ameliorate the pathological damage in pancreatic β-cells and the liver tissue. It enhanced the expression of key proteins and enzymes, including insulin receptor, insulin receptor substrate, PI3K, phosphorylated-AKT, hepatic kinase, GLUT4, glycogen synthase, GSK3β, GLK, PFK1, PKM2, and AMPKα, which are related to insulin metabolism and glycolysis. The protein also reduced the expression of G6Pase, PCK, and ACC, which are related to gluconeogenesis and lipid metabolism in the liver, and decreased the expression of TNF-α, IL-6, P65, and IKKβ related to inflammation. In general, sericin could maintain normal glucose levels and regulate insulin secretion, insulin and lipid metabolism, and inhibition of inflammation. Therefore, sericin protein could be developed into a novel functional health food with significantly hypoglycaemic effect. [ABSTRACT FROM AUTHOR]

The aqueous solution of hydrated lime (calcium hydroxide) was first used as a silk-degumming/refining agent. The sericin outside silk fibroin filaments was completely removed after boiling (20 min × 2) in a 0.025% calcium hydroxide solution. The calcium hydroxide degumming did not induce an evident breakage of the silk fibroin peptide chains. The tensile, thermal and surface properties of the fibroin fibre all showed that it is a degumming agent slightly low to neutral soap and far superior to Na 2 CO 3 solution. The alkaline degumming wastewater containing sericin was neutralized by sulphuric acid or phosphoric acid and generated insoluble calcium salt precipitation, which can be used as plant fertilizer. After the residual solution was concentrated and filtered, the sericin powder was obtained using a spray dryer or lyophilizer. The sericin with a lower molecular mass (≤20 kDa) can be widely used in such applications as cosmetics, medical biomaterials, food or medium additives. The hydrated lime water as a novel silk degumming agent can be used widely in the silk industry. The degumming technology not only avoids serious environmental pollution from degumming waste liquid, but also can recover a large number of biological resources-sericin protein. [ABSTRACT FROM AUTHOR]

• The ethanolic extract (EE) from new green cocoon consisted of abundant flavonoids. • EE shows strong antioxidant, anti-fibrosis and anti-inflammation activities. • The results suggested that EE might be useful for Diabetic nephropathy. Diabetic nephropathy (DN) is one of the major complications of diabetes. Sericin and flavonoids are two bioactive substances which have been demonstrated to have some therapeutical effect on diabetic nephropathy. The aim of this paper is to investigate the effect of ethanolic extract (EE) rich in quercetin and kaempferol and their glucosides from the green cocoon of silkworm Bombyx mori on DN in type 2 diabetic (T2D) mice induced by high-fat and streptozotocin (STZ). Ethanolic extract from the green cocoon shell of silkworm Bombyx mori was used as material. Diabetic mice were orally treated with three doses (150, 250 and 350 mg/kg) of the extract for 7 weeks, then the levels of oxidases and related inflammatory factors were measured in kidneys. Compared with the negative control, EE administration resulted in an evident reduction in blood glucose levels and an improvement of the body weight in diabetic mice. Oral EE could inhibit the expressions of renal tumour necrosis factor TNF-α, monocyte chemoattractant protein-1 (MCP-1), fibronectin (FN) and P38 mitogen-activated protein kinase (p38 MAPK) in T2D mice. Moreover, the levels of superoxide dismutase (SOD) and glutathione peroxidase (GSH-px) were significantly elevated in T2D mice treated with EE. The activities of anti-fibrosis and anti-inflammation contributed to the renal protective effects by reducing oxidative stress, which might be mediated by the inhibition of the TNF-α-p38 MAP kinase signalling pathway. It is suggested that the ethanolic extract from silkworm green cocoon might be potential as an herbal medicine for DN. [ABSTRACT FROM AUTHOR]