A resonance Rayleigh scattering method for sensitive detection of chitosan based on supramolecular complex and mechanism study.

A convenient and sensitive resonance Rayleigh scattering (RRS) method for the detection of chitosan (CTS) has been developed via forming Cu-Zn supramolecular complex by complexation reaction, hydrophobic force and electrostatic attraction. The microstructure of the complex was characterized by FT-IR, zeta potential, scanning electron microscope (SEM), UV-vis and RRS. Furthermore, the interaction mechanism among Cu(II), Zn(II), CTS and sodium dodecyl benzene sulfonate (SDBS) was studied. The results revealed that CTS and Cu(II) or Zn(II) formed a supramolecular complex with RRS enhancement in weak acid condition. In the presence of SDBS, the RRS intensity of CTS-Cu(II)-SDBS or CTS-Zn(II)-SDBS was significantly higher than that of the binary system without SDBS at the same CTS concentration. The RRS intensity of CTS-Cu(II)-Zn(II)-SDBS was higher than that of CTS-Cu(II)-SDBS and CTS-Zn(II)-SDBS. The RRS intensity increased linearly with the increase of CTS concentration made it possible to determine CTS quantitatively. In the range extending from 0.10 to 5.00 µg/mL, the equation of linear regression was ΔI=1848.8c-138.3 with a correlation coefficient 0.9996, and the detection limit was estimated to be 37.96 ng/mL. The study was successfully applied for the determination of CTS in health food samples, suggesting its great potential toward CTS analysis.

A resonance Rayleigh scattering and fluorescence quenching dual-channel sensor for sensitive detection of chitosan based on Eosin Y.

The sensitive chitosan (CTS) detection methods based on the resonance Rayleigh scattering (RRS) quenching method and fluorescence quenching of Eosin Y were put forward. In the HAC-NaAC buffer solution, Eosin Y interacted with Triton X-100 to generate the binary complex which served as the RRS spectral probe. When CTS was interacted with the binary complex, the RRS intensity decreased with the increase of CTS. At the same time, the fluorescence intensity of Eosin Y decreased in the presence of Triton X-100, and the fluorescence intensity of "Eosin Y+Triton X-100" system further decreased when CTS was added. So it was further proved that there was a forming complex in "Eosin Y+Triton X100+CTS" system. The interaction was characterized by zeta potential, RRS, fluorescence spectrum, and UV-Vis spectroscopy. Under optimal conditions, there was a good linear relationship between the RRS decreased intensity (ΔI) and the concentration of CTS in the range of 0.05-1.30 µg/mL, with a regression equation of ΔI = 1325c + 73.66 and correlation coefficient (R2) of 0.9907. The detection limit was 0.0777 µg/mL. Likewise, the linear range of the fluorescence quenching was 0.03-1.30 µg/mL; the regression equation was ΔF = 1926c + 294.0 with R2 = 0.9800 under fluorescence quenching. The detection limit was 0.0601 µg/mL. Therefore, the dual-channel sensor for the determination of CTS was applied to the health products, and the results were satisfactory. The t test result showed that there was no statistical difference between the two methods.

Application of Gelatin Decorated with Allura Red as Resonance Rayleigh Scattering Sensor to Detect Chito-Oligosaccharides.

A convenient and sensitive triple-wavelength overlapping resonance Rayleigh scattering (TWO-RRS) method for the detection of chito-oligosaccharides (COS) was proposed based on enhancing the rigid surface of porous reticular spatial structure of gelatin and COS by introducing allura red AC (AR). The interaction and resultant porous reticular spatial structure were characterized with transmission electron microscopy (TEM), RRS, and UV-Vis spectroscopy. The results indicated that gelatin and COS formed porous reticular spatial structure with an average diameter of 1.5-2.0 µm, and the RRS value of COS-AR-gelatin ternary system with gelatin participation was significantly higher than that of COS-AR binary system. Under the optimal conditions, the enhanced TWO-RRS intensity of the system was linearly proportional to COS concentration in the range of 0.30-2.50 µg/mL, and the regression equation was ΔI = 4933.2c-446.21 with R2 = 0.9980. The limit of detection was 0.0478 µg/mL. So, a new method for the detection of COS was established and verified in the health products with satisfactory results.

The triple-wavelength overlapping resonance Rayleigh scattering method and the fluorescence quenching method for the determination of chitooligosaccharides using trisodium-8-hydroxypyrene-1,3,6-trisulfonate as a probe.

In this assay, the triple-wavelength overlapping resonance Rayleigh scattering (TWO-RRS) method and the fluorescence quenching method for the quantitative detection of chitooligosaccharides (COS) were developed. In the weakly Britton-Robinson buffer solution, COS interacted with Trisodium-8-hydroxypyrene-1,3,6-trisulfonate (HPTS) to form an ion-association complex of HPTS-COS, which increased the RRS intensities at 321 nm, 430 nm and 511 nm and decreased the fluorescence intensities of the system at 512 nm. And the changes in the intensities of both methods were related to the changes in the concentration of COS. Moreover, for the TWO-RRS method, OP-10 made the RRS intensities increased stronger, finally, the three peaks' total was linear to the concentration of COS in the range of 1.00-8.00 µg/mL and the limit of detection (LOD) was 0.247 µg/mL, and for the fluorescence quenching method, the linear range was 0.50-3.50 µg/mL with the LOD of 0.108 µg/mL. Based on these, two new and fast spectral methods with high sensitivity and simplicity for the determination of trace COS had been established. The generation mechanism of the TWO-RRS and the fluorescence quenching was studied. At the same time, the two methods were applied to the determination of COS in health products with satisfactory results.

Chitinophaga varians sp. nov., isolated from forest soil.

A Gram-stain-negative, aerobic, non-motile bacterium, designated strain 10-7W-9003T, was isolated from the forest soil of Limushan National Forest Park, south-east China (19° 10' 42″ N, 109° 44' 45″ E). Strain 10-7W-9003T showed a shape change during the course of culture from long filamentous cells (5-10×0.4-0.5 µm) at 5-36 h, to rod shaped (1.0-1.5×0.5-0.7 µm) with inoculation after 2 days. It grew optimally at 28-30 °C and pH 6.5-7.5. On the basis of 16S rRNA gene sequence analysis, it belongs to the genus Chitinophaga and is most closely related to Chitinophaga eiseniae KACC 13774T and Chitinophaga qingshengii JCM 30026T, with 16S rRNA gene sequences similarities of 98.8 and 98.3 %, respectively. However, the DNA-DNA hybridization study showed that strain 10-7W-9003T shared relatively low relatedness values with KACC 13774T (21.8 %) and JCM 30026T (20.4 %), respectively. The major fatty acids (>10 %) were iso-C15 : 0, C16 : 1ω5c and iso-C17 : 0 3-OH. The genomic DNA G+C content was 50.7 mol%. It contained MK-7 as the major quinone. The phenotypic, chemotaxonomic and phylogenetic data clearly showed that strain 10-7W-9003T represents a novel species of the genus Chitinophaga, for which the name Chitinophaga varians sp. nov. is proposed. The type strain is 10-7W-9003T (=GDMCC 1.1252T=KACC 19415T=KCTC 52926T).