Surfactant Sodium Deoxycholate Research Articles

Transfer of energy from thiacyanine to acridine orange and formation of exciplex between the two dyes bound to surfactants

Energy transfer from donor thiacyanine and to the acceptor acridine orange and formation of exciplex between the dyes have been probed fluorimatrically in the presence of different concentrations of the surfactants sodium deoxycholate (NaDC), sodium cholate (NaC) and sodium salt of N-lauroyl sarcosine (NLS). All the three surfactants enhance the fluorescence of thiacyanine with efficiency of the order NaDC>NaC≅NLS. Results show that NLS facilitates both energy transfer and exciplex formation, whereas premicellar and micellar concentrations of NaDC favour only exciplex formation, but NaC facilitates neither phenomenon. The difference in behaviour of the surfactants has been thought to be due to difference in size and rigidity of the respective micelles. Premicellar concentrations of NLS favours exciplex formation and micellar and post micellar conditions favour energy transfer.

Freeze-drying of itraconazole-loaded nanosphere suspensions: a feasibility study

The present study concerns the stabilization of the association of the new hydrophobic triazole derivative itraconazole within poly-ϵ-caprolactone-nanospheres by means of freeze-drying. We have investigated the freeze-drying of nanospheres, and especially the cryopreservation conditions, with the help of differential scanning calorimetry and zeta potential measurements. Five commonly used cryoprotective agents were evaluated (glucose, sucrose, trehalose, dextran, mannitol at 0, 5, 10, 20, and 30% [w/v]) after freeze-thawing and freeze-drying. The addition of carbohydrates led to a partial protection of the colloidal suspension, with leakage of 30% of itraconazole under the best cryopreservation conditions (10% of glucose or sucrose). Zeta potential measurements revealed that the main destabilization mechanism during freeze-drying was surface modifications of the nanospheres, and particularly drug desorption. Therefore, the hydrophilic surfactant adsorbed at the surface of the nanospheres played an important role in the cryopreservation. Replacing the commonly used non ionic surfactant PLURONIC®PE F68 by the anionic surfactant sodium deoxycholate resulted in a complete stabilization of itraconazole-loaded nanospheres after freeze-drying, with no drug desorption, in the presence of 10% sucrose, but not in the presence of glucose. As shown by thermal analysis, PLURONIC®PE F68 may crystallize during freezing, which could lead to surface modifications and drug desorption, whereas sodium deoxycholate may not. Moreover, the Tg′ of glucose-containing suspensions is 10°C lower than Tg′ of sucrose-containing suspensions, which may explain the shrinkage of the cake observed in the case of glucose and the homogeneous appearance of the dried product in the case of sucrose. © 1996 Wiley-Liss, Inc.

Determination of phosphatidylcitoline in serum with use of a choline-sensitive membrane electrode

A choline-sensitive membrane electrode made with potassium tetrakis( p-chlorophenyl) borate as the exchanger and o-nitrophenyl phenyl ether as membrane solvent in poly (vinyl chloride) was almost insensitive to the surfactant sodium deoxycholate. By using this electrode, choline ( 10 −5 M) formed by the enzymatic hydrolysis of phosphatidylcholine with phospholipase D in the presence of sodium deoxycholate as activator was successfully measured. The method was applied to the determination of phosphatidylcholine in serum.