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.

Synergistic enhancement on flexible solid-state supercapacitor based on redox-active Fe3+ions/natural spidroin modified vertically aligned carbon nanotube arrays.

The conductive skeleton and aligned carbon nanotube array (CNTA) structure can greatly shorten the ion transfer path and promote the charge transfer speed, which makes the CNTA an ideal electrode material for energy storage application. However, poor mechanical stability and low specific capacitance greatly impede its practical utilization. Here, we introduce a promising flexible electrode material based on the natural spider silk protein (SSP) modified CNTA(SSP/CNTA) with improved hydrophilicity and mechanical flexibility. The redox-active Fe3+doped SSP/CNTA flexible solid-state supercapacitor (FSSC) device with superior energy storage performance was assembled in a symmetric 'sandwich-type' structure. The synergetic interaction between Fe3+ions and the SSP are proved to greatly enhance the electrochemical performance especially the long-term cyclic stability. The Fe3+doped SSP/CNTA FSSCs device achieves an ultra-high volumetric capacitance of 4.92 F cm-3at a sweep speed of 1 mV s-1. Meanwhile it exhibited an excellent cycling stability with an increased capacitance by 10% after 10 000 charge-discharge cycles. As a control, a Fe3+doped CNTA composite device without SSP will lose over 74% of the capacitance after 10 000 cycles. The energy storage mechanism analysis confirms the dominated capacitive behavior of the device, which explained a considerable power density and rate performance. Our method thus provides a promising strategy to build up highly-efficient redox-enhanced FSSCs for next generation of wearable and implantable electronics.

Effect of citrus lemon oil on growth and adherence of Streptococcus mutans.

In order to exploit novel anticaries agents, we investigated the effects of citrus lemon oil (CLO), a type of natural product, on growth and adherence of the primary oral cariogenic bacteria Streptococcus mutans (S. mutans). The growth inhibitory effect was explored with a micro-dilution assay. Adherence was analyzed by colony counts on the respective surfaces and the adherence inhibition rate (AIR). Real time-PCR was used to investigate the effects of CLO on transcription of glucosyltransferase (Gtf) encoding genes, gtfB, C and D. Neson-Somogyi method was used to measure the effects of CLO on Gtf activity. The minimum inhibitory concentration of CLO against S. mutans was 4.5 mg/ml. The CLO effectively reduced the adherence of S. mutans on glass surface (the AIR were from 98.3 to 100 %, P > 0.05) and saliva-coated enamel surface (the AIR were from 54.8 to 79.2 %, P < 0.05). CLO effectively reduced the activity of Gtf and the transcription of gtfs in a dose dependent manner (P < 0.05). In conclusion, CLO can effectively inhibit the growth and the adherence to glass and saliva-coated enamel surfaces of S. mutans. It can also inhibit the transcription of gtfs, as well as the Gtf enzyme activity.

[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.