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 scientifi c data that support the protective effect of silk sericin against cancer cells of the colon and suggests that this protein may have signifi cant health benefi ts and could potentially be developed as a dietary supplement for colon cancer prevention.

A cholesterol lowering effect of sericin was investigated both in vivo and in vitro. Rats were dosed with cholesterol with and without sericin for 14 days. Non-high-density lipoprotein (HDL) and total serum cholesterols were reduced in rats fed high-cholesterol diet with all three tested doses of sericin (10, 100, and 1000 mg kg(-1) day(-1)). The potential mechanism of actions was determined by measuring the uptake of radiolabeled cholesterol into differentiated Caco-2 cells and cholesterol solubility in mixed lipid micelles. Concentration of sericin as low as 25 and 50 μg/mL inhibited 30% of cholesterol uptake into Caco-2 cells whereas no effect was found at higher concentration. Cholesterol micellar solubility was reduced in the presence of sericin. This study suggests the cholesterol lowering effect of sericin results from its inhibition of cholesterol absorption in intestinal cells and its reduction of cholesterol solubility in lipid micelles.

Meltability of process Cheddar cheese made with disodium phosphate (DSP) and trisodium citrate (TSC) at various moisture contents was determined with a Rheometrics dynamic stress rheometer using 25 mm parallel plate geometry. Slippage was controlled either by bonding ethyl‐2‐cyanoacrylate adhesive directly to the plates or using serrated plates. Results from serrated plates were more consistent and repeatable than the technique with adhesive. Transition temperature was defined as the lowest temperature at which tan δ= 1 and reflects a change in cheese properties such that elastic and viscous properties are equivalent. Moisture contents between 38.60 to 39.80% did not significantly influence the transition temperature of disodium phosphate and trisodium citrate process cheese. Transition temperature of process cheese containing TSC was lower than cheese containing DSP. Arrhenius plot of complex viscosity (ɛ*) versus temperature indicated that the rate of change in viscosity of TSC process cheese was higher than that of DSP cheese.

BackgroundIn our previous study, we successfully developed 3-D scaffolds prepared from silk fibroin (SF), silk fibroin/collagen (SF/C) and silk fibroin/gelatin (SF/G) using a freeze drying technique. The blended construct showed superior mechanical properties to silk fibroin construct. In addition, collagen and gelatin, contain RGD sequences that could facilitate cell attachment and proliferation. Therefore, in this study, the ability of silk fibroin and blended constructs to promote cell adhesion, proliferation and production of extracellular matrix (EMC) were compared.MethodsArticular chondrocytes were isolated from rat and cultured on the prepared constructs. Then, the cell viability in SF, SF/C and SF/G scaffolds was determined by MTT assay. Cell morphology and distribution were investigated by scanning electron microscopy (SEM) and histological analysis. Moreover, the secretion of extracellular matrix (ECM) by the chondrocytes in 3-D scaffolds was assessed by immunohistochemistry.ResultsResults from MTT assay indicated that the blended SF/C and SF/G scaffolds provided a more favorable environment for chondrocytes attachment and proliferation than that of SF scaffold. In addition, scanning electron micrographs and histological images illustrated higher cell density and distribution in the SF/C and SF/G scaffolds than that in the SF scaffold. Importantly, immunohistochemistry strongly confirmed a greater production of type II collagen and aggrecan, important markers of chondrocytic phenotype, in SF blended scaffolds than that in the SF scaffold.ConclusionAddition of collagen and gelatin to SF solution not only improved the mechanical properties of the scaffolds but also provided an effective biomaterial constructs for chondrocyte growth and chondrocytic phenotype maintenance. Therefore, SF/C and SF/G showed a great potential as a desirable biomaterial for cartilage tissue engineering.

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