Toxicological effects of dimethlybenzeneanthracene in Balb C mice and pharmacological intervention by silk sericin-conjugated silver nanoparticles.

Polycyclic aromatic hydrocarbons (PAHs) such as 7, 12-dimethylbenzneanthracene (DMBA), due to long-term bioaccumulation cause serious physiological processes and behavioral dysfunctions such as cancer, ageing, and hypertension. Silk sericin (SS) is instrumental in cancer applications due to presence of flavonoids and carotenoids which are natural pigments, present in the layer of sericin that has antioxidant and antityrosinase activity. It reduces oxidative stress and suppresses cancer cytokines while interacting with reactive oxygen species (ROS) to stand against lipid peroxidation. Recent research was focused to calculate the pharmacological intervention of sericin-conjugated silver nanoparticles (S-AgNO3 NPs) against DMBA-induced toxicity. For this purpose, SS protein was extracted from silkworm cocoons by degumming process and the prepared S-AgNO3 NPs via a green synthesis. In female albino mice, a total of 50 mg/kg oral administration of DMBA was used for the induction of toxicity which required almost 8 to 10 weeks approximately. After 60 days of experimentation, mice were dissected, blood samples were collected for further hematological and biochemical analysis and were euthanized via cervical dislocation. There was a significant rise in the level of red blood cells, platelets, lymphocytes, and hemoglobin at the highest applied concentration of sericin and its nanoparticles. Similarly, a reasonable decline was observed in the level of white blood cells, neutrophils, eosinophils, and monocytes as compared to the cancer-inducing group. The level of glutathione, lactate dehydrogenase, and alkaline phosphatase as well as immunoglobulins such as immunoglobulin A (IgA), immunoglobulin G (IgG), and immunoglobulin M (IgM) were significantly reduced in all treatment groups as compared to the DMBA-induced group. Substantial effects were demonstrated in response to S-AgNO3 NPs II (T) at the highest concentrations (200 mg/kg, BW) as follows: glutathione (2.42 ± 0.26 µmol/L), lactate dehydrogenase (493.6 ± 5.78 U/L), alkaline phosphatase (158.4 ± 6.35 U/L), IgA (4.22 ± 0.19 g/L), IgG (70 ± 1.70 g/L), and IgM (4.76 ± 0.12). The histopathological study of the liver, kidneys, and brain revealed that the DMBA-induced group showed cytotoxic effects against all selected organs of mice that were recovered by treatment of selective compounds but highly effective recovery was seen in S-AgNO3 NPs II (T). These results concluded that silk S-AgNO3 NPs showed significant pharmacological potential against cancer-inducing toxicity.

Fabrication of a Silk Sericin Hydrogel System Delivering Human Lactoferrin Using Genetically Engineered Silk with Improved Bioavailability to Alleviate Chemotherapy-Induced Immunosuppression.

Chemotherapy is one of the main treatments for cancer; however, it usually causes severe atrophy of immune organs and self-immunity damage to patients. Human lactoferrin (hLF) is a multiple biofunctional protein in regulating the immune response and thus holds great promise to alleviate chemotherapy-caused immunosuppression. However, a sufficient hLF resource and efficient delivery of hLF remain a challenge. Here, we provide a useful strategy to simultaneously solve these two problems. A silk sericin hydrogel system delivering recombinant hLF (SSH-rhLF) was fabricated to alleviate the chemotherapeutic drug-caused side effects by rhLF-carrying silk cocoons, which were cost-effectively produced by a transgenic silkworm strain as the resource. SSH-rhLF with a uniform porous microstructural morphology, a dominant ß-sheet internal structure, adjustable concentration and sustainable release of the rhLF, and non-cytotoxicity properties was demonstrated. Interestingly, the sericin hydrogel showed effective protection of the rhLF from degradation in the stomach and small intestine, thus prolonging the bioactivity and bioavailability of rhLF. As a result, the oral administration of SSH-rhLF with a low rhLF dose showed significant therapeutic effects on enhancing the immune organs of cyclophosphamide (CTX)-treated mice by protecting the splenic follicles, promoting the expression of immunoregulatory factors, and recovering the intestinal flora family from CTX-induced imbalance, which were similar to those achieved by oral administration of a high dose of free hLF in the solution form. The results suggest that the strategy of producing rhLF silk cocoons via feeding transgenic silkworms overcomes well the shortage of rhLF resources, improves the bioavailability of oral rhLF, and alleviates the side effects of chemotherapeutic drugs on immune organs. The oral SSH-rhLF will be promising for applications in cancer chemotherapy and immunity enhancement of patients.

Safety Assessment of Water-Extract Sericin from Silkworm (Bombyx mori) Cocoons Using Different Model Approaches.

Sericin is a natural protein component of silks of silkworm and has potential utility in multiple areas such as pharmacological, cosmetics, and biotechnological industries. However, the understanding of its toxicological safety is still limited. This study evaluated the safety of water-extract sericin from silkworm (Bombyx mori) cocoons using different model approaches, including three genotoxicity studies (the bacterial reverse mutation test, the mammalian erythrocyte micronucleus test, and the mouse spermatogonia chromosomal aberration test) and a 90-day subchronic toxicity study in Sprague-Dawley (SD) rats. The results of this study showed that water-extract sericin was nonmutagenic and nongenotoxic both in vitro and in vivo. Sericin did not induce significant changes in the body and organ weight, food intake, blood hematology and serum biochemistry, urine index, and histopathology in rats. The NOAEL of sericin was determined to be 1 g/kg/day for male and female rats. These results indicated that water-extract sericin was of low toxicity in the experimental conditions of the current study and had the potential for application in food-related products.

Construction of a composite hydrogel of silk sericin via horseradish peroxidase-catalyzed graft polymerization of poly-PEGDMA.

Silk sericin (SS), which is one of the main components of Bombyx mori silk fibers, has attracted increasing attentions as functional biomaterials due to its diverse biological activities as well as excellent biocompatibility. However, the poor formability and weak mechanical properties of SS materials severely limit their practical applications in biomedical field. To address this issue, in this study poly(ethylene glycol)dimethacrylate (PEGDMA) modified sericin were prepared by graft polymerization of poly-PEGDMA (pPEGDMA) onto sericin chains in the presence of horseradish peroxidase and hydrogen peroxide under mild condition. The composite hydrogels obtained from the modified SS not only exhibit much improved formability and excellent mechanical properties, but also high possess porosity and swelling ratios up to 63 and 1,250%, respectively, at the optimized formulation. Moreover, the composite hydrogels also reveal sustained drug release behavior and acceptable cytotoxicity, which endow them with vast application as biomaterials. It is envisioned that the method presented in this study would expand the application of SS in biomedical filed.

Does Sericin, as a Novel Pleurodesis Agent, Have Higher Effectiveness Compared to Talcum Powder, Doxycycline, and Silver Nitrate Pleurodesis?

INTRODUCTION: The usefulness of sericin as pleurodesis agent has previously been described. Present study aims to compare sericin pleurodesis regarding success, effectiveness, tolerability, and side-effects. METHODS: Adult, 12-week-old Wistar-albino rats (n=60), divided to five groups as sericin, talcum-powder, doxycycline, silver-nitrate and control. Agents were administrated through left thoracotomy, rats sacrificed twelve-days after. RESULTS: Highest ratio of collagen fibers was observed in sericin group, and the intensity was higher than talcum-powder group (p<0.05). Compared to silver nitrate, sericin group displayed better mesothelial reaction, and multi-layer mesothelium was also better (p<0.05). Foreign body reaction and emphysema were less frequent in sericin group (p<0.05). The presence of biological tissue in parenchyma was less prominent in sericin group (p<0.05). Foreign body reaction on thoracic wall was less common in sericin group (p<0.05). Presence of biological tissue glue in thoracic wall was less prominent in sericin group (p<0.05). Glomerular degeneration was lower in sericin group compared to the silver nitrate group (p<0.05), and tubular degeneration was less common in sericin group than talcum group (p<0.05). Pericarditis was less common in sericin group compared to the other groups (p<0.05). CONCLUSION: As an intrinsic, natural glue protein, sericin protects the lung parenchyma and tissues, and its glue-like characteristics enable pleurodesis. The success of sericin in pleurodesis was demonstrated in the present study based on investigations of the pleurae. Being cost-effective and better tolerated agent associated with a low potential of side effects, sericin is more effective, less expensive and provides more lung parenchyma protection.

Can Sericin Prove Useful as a Pleurodesis Agent or Tissue Glue?

Background Sericin is a natural, gum-like, macromolecule protein, synthesized from silkworms for the formation of cocoon shells. The aim of the present study is to describe the effects of sericin when used for pleurodesis and/or as tissue glue. Methods Adult, male, 12-week-old Wistar albino rats, weighing 257 to 395 g were used in the present study (n = 12). The animals were randomly divided into two equal groups as the sericin and the control group. After intramuscular administration of the anesthetic agent, the rats were intubated and mechanically ventilated. A left thoracotomy was performed and 30 mg sericin powder was instilled into the thoraxes of the sericin group. The remaining rats were allocated to a sham thoracotomy group. The animals were housed in individual cages, fed ad-libitum, and sacrificed 8 days after. After sacrifice, the left hemithoraxes were removed en bloc and underwent histopathologic examination. Results Masson trichrome staining was applied on the visceral pleura sections of all the animals. Each animal specimen (n = 6, 100%) in the control group showed minimal collagen deposition, while only one rat (16.67%) in the sericin group had minimal collagen deposition. However, in the sericin group, five animals (83.33%) showed dense collagen deposition, fibroblastic activity, and fibrosis. According to the test method, independent t-test, developing fibroblastic activity and fibrosis are statistically significant between the two groups (p < 0.01). There were no foreign-body reactions and no evidence of biological glue on the specimens in the sericin group. The rats in the sericin group had lower inflammatory reactions compared with those in the control group. Emphysema was observed in two rats (33.33%) in the sericin group and in four rats (66.67%) in the control group. Therefore, sericin was found to be associated with an increase in fibroblastic activity and fibrosis in visceral pleura without exerting any adverse effect on the lung parenchyma. Conclusion Sericin is a new and researchable protein for chest diseases and thoracic surgery. To develop an effect of dense collagen deposition, fibroblastic activity, and fibrosis in the visceral pleura, without significant adverse effects, is remarkable. Therefore, sericin may be useful as a pleurodesis agent or natural biological glue in the future. Sericin treatment can add value to the disciplines of pulmonology and thoracic surgery.

The development of non-toxic ionic-crosslinked chitosan-based microspheres as carriers for the controlled release of silk sericin.

Silk sericin is recently shown to possess various biological activities for biomedical applications. While various sericin carriers were developed for drug delivery system, very few researches considered sericin as a bioactive molecule itself. In this study, sericin incorporated in the chitosan-based microspheres was introduced as a bioactive molecule and bioactive carrier at the same time. The chitosan/sericin (CH/SS) microspheres at different composition (80/20, 70/30, 60/40, and 50/50) were successfully fabricated using anhydroustri-polyphosphate (TPP) as a polyanionic crosslinker. The microspheres with an average size of 1-4 µm and narrow size distribution were obtained. From FT-IR spectra, the presence of both chitosan and sericin in the microspheres confirmed the occurrence of ionic interaction that crosslink them within the microspheres. We also found that the CH/SS microspheres prepared at 50/50 could encapsulate sericin at the highest percentage (37.28%) and release sericin in the most sustained behavior, possibly due to the strong ionic interaction of the positively charged chitosan and the negatively charged sericin. On the other hand, the composition of CH/SS had no effect on the degradation rate of microspheres. All microspheres continuously degraded and remained around 20% after 14 days of enzymatic degradation. This explained that the ionic crosslinkings between chitosan and sericin could be demolished by the enzyme and hydrolysis. Furthermore, we have verified that all CH/SS microspheres at any concentrations showed non-toxicity to L929 mouse fibroblast cells. Therefore, we suggested that the non-toxic ionic-crosslinked CH/SS microspheres could be incorporated in wound dressing material to achieve the sustained release of sericin for accelerated wound healing.

Modulation of cell growth on exposure to silkworm and spider silk fibers.

Recent years have seen an increased interest in the use of natural and modified silks for tissue engineering. Despite longstanding concerns regarding the biocompatibility of silk sutures, only a few studies have been carried out to investigate the biocompatibility of natural silk fibers. Here, we report an in vitro assessment of the effect of nonmodified, degummed silks on cells. We describe the effects of degummed silk fibers as well as extracted sericin on cell metabolism and proliferation. Endothelial cells directly exposed to native degummed Bombyx mori and Antheraea pernyi silks showed lower rates of proliferation and metabolism than nonexposed cells. A similar but milder effect was observed for cells in direct contact with Nephila edulis egg sack fibers. Sericin and silk-conditioned medium had no negative effect on cell proliferation except in medium supplemented with 5% bovine serum prior to conditioning with A. pernyi silk. The toxicity of A. pernyi was negligible after thorough enzymatic treatment of the fibers with trypsin. It is, therefore, proposed that A. pernyi silk contain one or more cytotoxic components, which need to be removed prior to medical use.

The effect of sericin with variable amino-acid content from different silk strains on the production of collagen and nitric oxide.

Although silk sericin (SS) enhances the growth and attachment of fibroblast cells, its toxicity remains questionable. We investigated the effect of SS extracted by heat with variable amino-acid content on in vitro collagen promotion and nitric oxide synthesis. After 24 h of incubation, SS, especially from the Chul 1/1 strain which has the most methionine and cysteine content, enhanced fibroblast growth. The molecular mass of heat-extracted SS from these three strains showed a slightly different range, but within 20-200 kDa, which were all identified as sericin. SS from all strains promoted type-I collagen production in a concentration-dependent manner, while SS from Chul 1/1 strain could induce the highest amount of collagen synthesis when compared to SS from other strains. Nitric oxide was found in the culture medium after activation by SS from the Chul 1/1 strain but reached a level that was not toxic to the cells. We conclude that SS is not toxic to fibroblast cells. Moreover, methionine and cysteine content in SS are important factors to promote cell growth and collagen synthesis.