ABSTRACT
To investigate the influences of zwitterionic polymer chain length on mucus permeability and cellular uptake, the nanoparticles (NPs) were coated with poly(sulfobetaine methacrylate) (pSBMA) with different chain lengths. The di-block polymer poly(ε-caprolactone)-block-poly(sulfobetaine methacrylate) (PCL-pSBMA) with different chain lengths were synthesized via atom transfer radical polymerization (ATRP) combining with ring-opening polymerization of ε-caprolactone, and corresponding nanoparticles (pSBMAn NPs) were prepared by nanoprecipitation method. The sizes of different pSBMAn NPs were around 100 nm, and zeta potential were about -7 mV. Mucin interaction or mucus penetration study based on transwell systems were employed to evaluate mucus permeability of NPs. Caco-2 cells and mucus-producing HT-MTX-E12 cells were employed to illustrate the endocytosis efficiency of pSBMAn NPs. The results showed that the permeability coefficient of NPs coated with shorter chain length of pSBMA (pSBMA10 NPs) was only 42.83% of that coated with longer pSBMA (pSBMA80 NPs). On the contrary, the cellular uptake of pSBMA10 NPs was 2.44 fold higher compared to pSBMA80 NPs. Although the cellular uptake of pSBMAn NPs was reduced in the presence of mucus, pSBMA10 NPs still presented the highest cellular uptake. However, the in vivo results indicated that the oral bioavailability of pSBMA20 NPs was higher than that of pSBMA10 NPs. All animal procedures were performed in accordance with the Guidelines of the Sichuan University Animal Care and Use Committee and were approved by the Animal Ethics Committee of Sichuan University. This study provides a reference for oral delivery of zwitterionic nanoparticles.
ABSTRACT
ABSTRACT Studies of trophic networks and the evaluation of processes that occur along altitudinal gradients in river systems are of great importance because they allow an understanding of energy flow dynamics and provide scientific tools for the planning and management of river ecosystems. This research describes the trophic network of aquatic macroinvertebrates along an altitudinal gradient of the Gaira River, a mountain Neotropical watercourse located in the Sierra Nevada de Santa Marta in northern Colombia. The organisms were collected in the upper, middle and lower reaches of the river during the rainy and dry seasons (between 2010 and 2013). Trophic relationships were evaluated through gut content analysis. The contents were determined and quantified using photographs and expert review, and a binary consumption matrix was used to determine the characteristics of the trophic network. We characterized the diet composition at each site for each season using discriminant analysis. Trophic networks during the dry seasons showed higher trophic species richness and linkage density, and the predominance of coarse particulate organic matter (CPOM) and fine particulate organic matter (FPOM) in the high and medium sections of the river. During the dry seasons the diets had a lower number of basal species, but in the low river section there was a high percentage of fungi and microalgae. During the rainy seasons, no patterns were observed for the percentage of resources. Results indicated a direct relation between periods of hydrologic stability and an increase of CPOM during dry seasons and an increase of resource diversity consumed by macroinvertebrates at all sites during the rainy season, showing that changes in trophic networks of the Gaira River were more important during seasonal periods than along the altitudinal gradient.
ABSTRACT
The chemical structure of fatty acid has a great influence on the relaxation characteristic of lipid.In this work,the low-field nuclear magnetic resonance(LF-NMR) relaxation characteristics of fatty acids with different chain lengths or degree of saturation were investigated firstly,and then the relaxation characteristics of binary or ternary fatty acid mixtures were studied.The result showed that except acetic acid,the T2 relaxation time and T2Wdecreased as the carbon chain length increased; but as the unsaturated degree increased,these measures all increased.For the binary fatty acid system,the T2relaxation time and T2Wof palmitic acid-oleic acid and stearic acid-oleic acid all increased as oleic acid ratio increased.While for the linoleic acid-oleic acid system,only when the oleic acid ratio was above 40%,the relaxation response changed significantly.For the ternary fatty acid system,the T2relaxation time of each linoleic acid/oleic acid/stearic acid system increased with the increase of linoleic acid ratio,while the area ratio S21decreased,and S22increased.The higher ratio of oleic acid and the change of the peak area ratio were relatively reduced,and the relative increases of T2Wchanged more slowly.
ABSTRACT
Background: The paper reports on the utilization of palm kernel oil (PKO) as a low cost renewable substrate for medium-chain-length poly-3-hydroxyalkanoates (mcl-PHA) production by Pseudomonas putida BET001. Investigation on the effects of selected key variables on growth, mixed free fatty acids consumption and mcl-PHA production by the bacterial culture in the shaken flask system were carried out along with its kinetic modeling. Results: The biomass production, fatty acids consumption and mcl-PHA production were found favorable when the strain was cultured in mineral medium at pH 6-7,28°C, aeration surface-to-volume ratio of 0.4 x 10(6) m-1, 250 rpm agitation rate for 48 h. Mcl-PHA production by this strain showed mixed growth and non-growth associated components as described by Luedeking-Piret kinetic model. Conclusion: The findings of this study provided add to the literature on key variables in for achieving good microbial growth and mcl-PHA production in shake flasks culture. In addition, suitable kinetic model to describe cultivation in this system was also presented.