Phosphorus fractionation and bio-availability in Taihu Lake(China) sediments

Typical sediments from Taihu Lake, a meso-to-hypereutrophic lake, were collected and examined on the basis of P-fractionation by sequential extraction scheme. Sedimentary inorganic phosphorus were fractioned into four forms and the rank order according to the mean concentration of P-fractions in Taihu Lake was NaOH-P>BD-P>HCl-P>NH_4Cl-P. The concentrations of BD-P were linearly correlated with the content of active Fe(R2=0.96). Also, the linear relationship between the sum of BD-P and NaOH-P and the sum of active Fe and active Al content was observed within the six sediments investigated(R2=0.96). Moreover, the bio-available phosphorus(BAP) content was estimated by the sum of NH_4Cl-P, BD-P, and NaOH-P, viz. BAP=NH_4Cl-P+NaOH-P+BD-P. In Taihu Lake, the BAP contents are ranging from 0.10 mg/g dw to 1.25 mg/g dw, and average 0.40 mg/g dw for all sediment samples. The relative contributions of BAP to total sedimentary phosphorus(TP) and inorganic sedimentary phosphorus(IP) range from 18.67% to 50.79%(33.61% on average) and from 52.82% to 82.09%(67.81% on average), respectively.

Extraction of Natural Nanostructured Hydroxyapatite from Pacific Cod(Gadus macrocephalus)Bone with a Thermostable Collagenolytic Protease and Its ex vivo Intestinal Bioavailability

Natural nano-hydroxyapatite(HA)was extracted from Pacific cod(Gadus macrocephalus)bone with a thermostable col-lagenolytic protease in the present study.Conditions for the enzymatic reaction were optimized to be 60℃and pH 7.0,and a desir-able extraction efficiency was achieved by using the crude collagenolytic protease.Dynamic light scattering,transmission electron microscopy and energy-dispersive X-ray analysis revealed that nano-HA are anionic spherical(about 110nm)particles mainly com-prised of calcium and phosphorus at an approximate ratio of 5:3.As evaluated with the mouse ex vivo intestinal segments,the extracted nano-HA displayed comparable level of intestinal bioavailability to the positive control CaCl_(2).By treating with inhibitors(NaN3,ami-loride)and low temperature(4℃),clathrin-mediated endocytosis was assumed to involve the intestinal absorption of nano-HA.Over-all,the application of thermostable collagenolytic protease is proved to be a promising alternative method for nano-HA extraction from natural resource with improved ecological and biological value.

Inclusion complex of tamibarotene with hydroxypropyl-β-cyclodextrin: Preparation,characterization, in-vitro and in-vivo evaluation

The goal of this study was to improve the solubility and oral bioavailability of tamibarotene by complexing it with hydroxypropyl-β-cyclodextrin(HP-β-CD).The inclusion complex of tamibarotene with hydroxypropyl-β-cyclodextrin(Am80-HP-β-CD)was prepared through a freeze-drying method at the mole ratio of 1:1(Am80:HP-β-CD).Fourier transform infrared spectroscopy(FT-IR)and differential scanning calorimetry(DSC)indicated the formation of Am80-HP-β-CD.In vitro dissolution studies showed that the solubility and dissolution percentage of Am80-HP-β-CD was improved substantially compared to Am80.An improved dissolution with approximately 97%drug release in 3 min was observed,in comparison with Am80 with approximately 60% release in 45 min.In vivo studies indicated that the AUC0-∞ has increased 2.79 times and the Cmax 4.37 times after the formation of inclusion complex.The decrease of tmaxindicated the Am80-HP-β-CD inclusion complex can be absorbed into blood faster.In short,the solubility and bio-availability of Am80 has notably increased with the complexation of HP-β-CD.Therefore,using the inclusion technique is a promising method to improve the solubility of insoluble drugs.

Enhancement of Cd Solubility and Bioavailability Induced by Straw Incorporation in Cd-Polluted Rice Soil

Of the factors affecting migration and bioavailability of toxic metals in heavy metal contaminated soil, DOC （dissolved organic carbon） provides binding sites for metal cations and reduces the fixation and adsorption of heavy metals by soil solid phase. Elevation of DOC level due to the direct incorporation of crop residues may lead to enhanced accumulation of toxic metals in crop body grown in polluted farmland. In this study, an incubation experiment and a pot experiment were conducted respectively to investigate the effects of wheat straw incorporation on DOC level, cadmium availability, and Cd accumulation in rice plant, and to establish the relation between Cd solubility and DOC level. A Cd-contaminated rice soil was used and incorporated with different rates （0%, 0.5% and 1%） of wheat straw in both experiments. Results showed that the change pattern of Cd in soil solution was very similar to that of DOC level. Wheat straw addition significantly elevated Cd and DOC level in soil solution while NH4NO3-extrated Cd was not affected. There existed a close linear correlation between soluble Cd and DOC level. Enhanced Cd accumulation in rice plant, grown in a Cd contaminated soil, induced by wheat straw incorporation was observed in this study.