Dry-Spinning of Artificial Spider Silk Ribbons From Regenerated Natural Spidroin in an Organic Medium.

Natural spider silks with striking performances achieve extensive investigations. Nonetheless, a lack of consensus over the mechanism of the natural spinning hinders the development of artificial spinning methods where the regenerated spider silks generally show poor performances compared with the natural fibers. As is known, the Plateau-Rayleigh instability tends to break solution column into droplets and is considered a main challenge during fiber-spinning. Here in this study, by harnessing the viscoelastic properties of the regenerated spidroin dope solution via organic salt-zinc acetate (ZA), this outcome can be avoided, and dry-spinning of long and mechanically robust regenerated spider silk ribbons can be successfully realized. The as-obtained dry-spun spider silk ribbons show an enhanced modulus up to 14 ± 4 GPa and a toughness of ≈51 ± 9 MJ m-3 after the post-stretching treatment, which is even better than that of the pristine spider silk fibers. This facile and flexible strategy enriches the spinning methodologies which bypass the bottleneck of precisely mimicking the complex natural environment of the glands in spiders, shining a light to the spider-silk-based textile industrial applications.

[Effect of lemon essential oil on caries factors of Streptococcus sobrinus].

OBJECTIVE: To investigate the mechanism of lemon peel essential oil (LPE) on the cariogenicity of Streptococcus sobrinus (Ss). METHODS: LPE was extracted by the authors, and the minimum inhibition concentration (MIC) was measured by disc diffusion method. The LPE was used as the experimental group with concentrations ranging from 2.250 g/L to 0.281 g/L prepared with trypticase peptone yeast (TPY) culture medium, and TPY culture medium was used as the control group. Ss at the concentration of 10(8) CFU/ml was added to each group, and cultured for 6, 18, 24, 48 hours. Neson-Somogyi method was used to measure the content of reducing sugar, and glucosyltransferase (GTF) activity. The activity of lactate dehydrogenase (LDH) was measured by lactic acid and pyruvic acid continuous monitoring method. The content of water insoluble glucan (WIG) was measured by anthrone method, and the pH value of the culture solution was detected. The value of pH before the experiment and the time difference was alculated as ΔpH. RESULTS: At the same time point, the activity of GTF and LDH and the concentration of WIG and the value ΔpH decreased gradually with the increase of concentration of LPE. There were significant differences between each experimental group and control group (P < 0.01). The control group had the maximum value, GTF: (6.71 ± 0.61) mIU, LDH: (135.8 ± 1.7) U/L, WIG: (47.15 ± 5.12) mg/L, ΔpH: (2.67 ± 0.01). The highest drug concentration group had the minimum value: GTF: (0.39 ± 0.07) mIU, LDH: (95.0 ± 5.4) U/L, WIG: (2.44 ± 0.38) mg/L, ΔpH: (0.61 ± 0.01). CONCLUSIONS: The LPE below the MIC could still inhibit the GTF, LDH activity and lead to the decrease of WIG and the acid production.