Surface-enhanced Raman scattering-based detection of molecules in an aqueous solution via lipid-modified gold nanorods.

Transport of molecules and ions across cellular membranes is a fundamental process in biology. Visualization of such transport is an essential element toward a better understanding of how incoming molecules or ions interact with cellular membranes and diffuse into cytoplasm. However, detection techniques for this purpose have not been explored yet. Here we propose an innovative label-free detection technique that, in principle, permits real-time visualization of molecules across a cellular membrane. Lipid-modified gold nanorods (GNRs) in aqueous solution are exploited as nanoprobes for surface-enhanced Raman scattering (SERS)-based detection of neighboring molecules. For this purpose, the surfaces of as-synthesized GNRs were modified with a variety of phospholipids (DOPC, POPC, and DPPC, respectively) by extraction-based ligand exchange. The lipid-modified GNRs were characterized by transmission electron microscopy (TEM), UV-vis spectroscopy, and zeta potential measurement. As a proof-of-concept, SERS measurement of R6G with the lipid-modified GNRs was carried out. The limit of detection was found to be around 100 nM.

HPLC-electrospray ionization-MS-MS analysis of Cephalotaxus harringtonia leaves and enhancement of the extraction efficiency of alkaloids therein by SFE.

A high-performance liquid chromatographic method is developed for use in the electrospray mass spectrometric (MS)-MS analysis of alkaloids contained in Cephalotaxus harringtonia leaves. Nine alkaloids having ester groups can be separated and detected with good sensitivity. The MS and MS-MS spectra obtained provides information on their chemical structures. Supercritical fluid extraction is also applied in order to improve the extraction efficiency of Cephalotaxus alkaloids such as cephalotaxine, harringtonine, homoharringtonine, and isoharringtonine. When carbon dioxide-methanol-water (80:18:2, v/v) is used the extraction yield is found to be higher than that using the other supercritical solvents evaluated and conventional organic solvent extraction.

Positive and negative electrorheological response of alginate salts dispersed suspensions under electric field.

Electrorheological (ER) effects of alginic acid and alginate salts (Na(+) alginate, NH(4)(+) alginate, and Ca(2+) alginate) dispersed suspensions were investigated under DC electric fields. A noteworthy result is that the Ca(2+) alginate dispersed suspension showed negative electrorheological effects under electric fields while the other suspensions exhibited positive electrorheological effects. It is the first time that the negative ER effect is obtained with the biomacromolecule. Interestingly, at the DC electric fields, the electromigration of particles to two electrodes was observed in the negative ER fluid, while the particles-bridges formed between two electrodes in the case of the positive ER fluid. In conclusion, the specific salt type of biomacromolecules could be suitable ER particles for negative ER suspension. We believe that our study can present a new way for the development of the biocompatible and eco-friendly negative ER fluids.

Supercritical fluid extraction and liquid chromatography-electrospray mass analysis of vinblastine from Catharanthus roseus.

Supercritical fluid extraction using carbon dioxide modified with methanol, methanol-diethylamine, or methanol-triethylamine was used to extract vinblastine from the aerial portions of Catharanthus roseus. An HPLC-electrospray ionization (ESI)/MS analysis method was also developed to quantify the alkaloids in these extracts. Of the supercritical solvents evaluated, carbon dioxide-methanol-triethylamine (80 : 18 : 2) at 80 degrees C and 34.0 MPa greatly improved the supercritical fluid extraction (SFE) yield of vinblastine by as much as 76.4% over methanol extraction, while the other solvent conditions extracted the compound at yields less than 25% that of a methanol extraction. These results were confirmed by the robust HPLC-ESI/MS analytical method developed in this study.