PREPARATION AND CHARACTERIZATION OF CHITOSAN/REGENERATED SILK FIBROIN (CS/RSF) FILMS AS A BIOMATERIAL FOR CONTACT LENSES-BASED OPHTHALMIC DRUG DELIVERY SYSTEM

Objective: The aim of this study was to develop chitosan/regenerated silk fibroin (CS/RSF) films as a biomaterial for contact lenses-based ophthalmic drug delivery system. Methods: CS/RSF films were prepared with polyethylene glycol 400 as a plasticizer by using a film casting technique. Their physicochemical properties were investigated by measuring various properties such as thickness, morphology, chemical interaction, light transparency, mechanical properties, water content, oxygen permeability, thermal properties and enzyme degradation. In addition, cytotoxicity was also studied. Results: At optimal preparation conditions, CS/RSF films showed smooth surfaces with highly visible light transparency of >90%, which meet the visual requirement. CS/RSF films showed high water content, 59-65% by weight, and their Young’s modulus and elongation at break was in the range of 3.8-6 N/mm2 and 113-135%, respectively. The CS/RSF films also could be sterilized by autoclave method as they possessed high thermal decomposition temperature of >260 °C which can be confirmed by both differential scanning calorimetry and thermogravimetric analysis. In addition, CS/RSF films showed no degradation in stimulated tear fluid containing lysozyme for 7 d and showed no cytotoxicity by MTT assay. Conclusion: CS/RSF films showed excellent physicochemical properties and non-cytotoxicity indicating their promising potential use as a biomaterial for contact lenses-based ophthalmic drug delivery system

Immune enhancement activities of silk lutein extract from Bombyx mori cocoons

BACKGROUND: Declining immune function poses an important clinical challenge worldwide and supplementation with natural products that possessing immune enhancing properties is a promising approach for preventing or delaying immune function decline. Cocoons from yellow silkworms are a significant source of lutein, and this unexplored silk extract could be a viable alternative source for dietary lutein. This study assessed immunomodulatory activities of the silk lutein extract. Female BALB/c mice orally received lutein, either as silk or marigold extracts (10 or 20 mg/kg daily), or vehicle only (1% tween 80 in PBS pH 7.4) for 4 weeks. Natural killer (NK) cell activity, specific antibody production, lymphocyte subpopulations, mitogen-induced lymphocyte proliferation, and cytokine production were examined. RESULTS: Silk lutein extract increased NK cell activity, and the effect was dose-related whereas marigold lutein extract was ineffective. Silk lutein extract dose-dependently enhanced antibody production in pre-immunized mice but marigold lutein extract had no effect. Feeding with silk lutein extract increased the populations of CD3+ and CD4 + CD3 + cells. Silk lutein extract also stimulated concanavalin A- and lipopolysaccharide-induced proliferations of T and B lymphocytes, respectively. Moreover, silk lutein extract increased IL-2 and IFN-γ production while the effect of marigold lutein extract was undetectable. CONCLUSIONS: Together, silk lutein extract enhanced both innate and adaptive immune functions. This preparation may prove to be an effective supplement for strengthened immunity

Hypoglycemic Ability of Sericin-Derived Oligopeptides (SDOs) from <i>Bombyx mori</i> Yellow Silk Cocoons and Their Physiological Effects on Streptozotocin (STZ)-Induced Diabetic Rats

Patients with diabetes require daily medication to maintain blood sugar levels. Nevertheless, the long-term use of antidiabetics can lose efficacy and cause degeneration in some patients. For long-term diabetes care, integrating natural dietary foods and medicine is being considered. This study investigated the impact of SDOs on blood sugar levels and their physiological effects on diabetic rats. We induced diabetes in male Wistar rats with STZ (50 mg/kg) and then administered an oral glucose tolerance test to determine the SDO dosage comparable to glibenclamide. The rats were divided into nine groups: normal, diabetic, and diabetic with insulin (10 U/kg), glibenclamide (0.6 mg/kg), bovine serum albumin (BSA; 200 mg/kg), soy protein isolate (200 mg/kg), or SDOs (50, 100, and 200 mg/kg). Diabetic rats administered SDOs had a higher body weight and serum insulin but a lower blood sugar than diabetic control rats. Biochemical assays indicated lower AST/SGOT, ALT/SGPT, BUN, and triglycerides but higher HDL in the SDO groups. Immunohistochemistry showed that SDOs reduced damaged islet cells, increased beta-cell size, and improved insulin levels while decreasing alpha cell size and glucagon. The vascular effects of SDOs were like those of normal control treatment and insulin treatment in diabetic rats. SDOs, a yellow silk protein, show potential for long-term diabetes care

Kinetic Models for Glucosamine Production by Acid Hydrolysis of Chitin in Five Mushrooms

In this paper, glucosamine was produced by acid hydrolysis of five mushrooms. The glucosamine yields were investigated, and the optimum conditions were obtained as follows: acid type, sulfuric acid; acid concentration, 6 M; ratio of raw material to acid volume, 1 : 10; hydrolysis temperature, 100°C; and time, 6 h. Under these conditions, the glucosamine conversion from chitin content reached up to 92%. The results of hydrolysis kinetics indicated that hydrolysis of five mushrooms to glucosamine followed zero-order kinetics. Moreover, the relatively low activation energy for hydrolysis of straw mushroom (18.31 kJ/mol) and the highest glucosamine yield (56.8132 ± 3.5748 mg/g DM, 0.9824 g/g chitin) indicated that hydrolysis of straw mushroom was energy-saving. Thus, sulfuric acid hydrolysis of straw mushroom for glucosamine production should be considered as an efficient process for the future industrial application. However, further study is needed for glucosamine purification

Novel daily disposable therapeutic contact lenses based on chitosan and regenerated silk fibroin for the ophthalmic delivery of diclofenac sodium

The aim of this study was to investigate the possibility of chitosan and regenerated silk fibroin (CS/RSF) blended films as novel biomaterials for daily disposable therapeutic contact lenses based ophthalmic drug delivery system. Diclofenac sodium (DS), a hydrophilic anti-inflammatory agent, was loaded into CS/RSF films by a soaking method. The best conditions of DS loading manifested the loading time of 2 h and pH 6.5 of drug solution. The drug loading capacity and the drug release profile could be controlled by varying the film RSF content. With increasing the film RSF content from 0 to 30%, the amount of loaded DS increased from 12 to 23 µg. Furthermore, the prolong drug released within therapeutic level was obtained with increasing the film RSF content. Consequently, a fast released characteristic within a therapeutic level up to 3 h was observed with the 100CS/0RSF film. On the other hand, the 70CS/30RSF film demonstrated a significant prolonged drug release within therapeutic level up to 11 h. In conclusion, the CS/RSF films are promising as novel biomaterials for daily disposable therapeutic contact lenses-based ophthalmic delivery

Protective effect of silk lutein on ultraviolet B-irradiated human keratinocytes

Carotenoids are efficient antioxidants that are of great importance for human health. Lutein and zeaxanthin are carotinoids present in high concentrations in the human retina which are involved in the photoprotection of the human eye. Lutein may also protect the skin from ultraviolet (UV)-induced damage. The present study investigated the protective effect of lutein extracted from yellow silk cocoons of Bombyx mori on human keratinocytes against UVB irradiation. A human keratinocyte cell line and primary human keratinocytes were used to investigate the UVB protection effects of silk lutein and plant lutein. Silk lutein showed no cytotoxicity to keratinocytes. Treatment with silk lutein prior to UVB irradiation enhanced cell viability and cell proliferation, and reduced cell apoptosis. The protective effects of silk lutein may be superior to those of plant lutein. Silk lutein may have a benefit for protection of keratinocytes against UVB-irradiation

The effect of dietary sericin on rats

ABSTRACT: Dietary proteins have been reported to be beneficial for lipid metabolism, tissue growth, development, and repair, as well as immune response. The interactions of dietary proteins and their digested products may regulate the physiology and metabolism of the gastrointestinal tract. However, proteins are largely digested before reaching the large intestine. The present study investigated the use of the non-dietary protein, silk sericin, in rats. Rats were fed either with casein or sericin proteins. Their body weight, food consumption, and complete blood count were measured. The results showed that during the experimental periods, rats fed with casein and sericin diets had no significant changes on body weight, food consumption, or complete blood count. Sericin-fed rats had a significantly decreased CD8a and CD80 positive cells when compared with standard casein protein. In conclusion, dietary proteins may have a differential impact on the leukocyte profile. The mechanisms underlying these changes are not clear but they might be due to the different amino acid compositions of the proteins studied

Effects of silk sericin on the proliferation and apoptosis of colon cancer cells

Sericin is a silk protein woven from silkworm cocoons (Bombyx mori). In animal model, sericin has been reported to have anti-tumoral action against colon cancer. The mechanisms underlying the activity of sericin against cancer cells are not fully understood. The present study investigated the effects of sericin on human colorectal cancer SW480 cells compared to normal colonic mucosal FHC cells. Since the size of the sericin protein may be important for its activity, two ranges of molecular weight were tested. Sericin was found to decrease SW480 and FHC cell viability. The small sericin had higher anti-proliferative effects than that of the large sericin in both cell types. Increased apoptosis of SW480 cells is associated with increased caspase-3 activity and decreased Bcl-2 expression. The anti-proliferative effect of sericin was accompanied by cell cycle arrest at the S phase. Thus, sericin reduced SW480 cell viability by inducing cell apoptosis via caspase-3 activation and down-regulation of Bcl-2 expression. The present study provides scientific data that support the protective effect of silk sericin against cancer cells of the colon and suggests that this protein may have significant health benefits and could potentially be developed as a dietary supplement for colon cancer prevention