Hans Evertsson

On the water content of the solvent/monoolein/water sponge (L3) phase

Abstract The water content of the solvent/monoolein/water sponge phase depends on the lipophilicity of the solvent used. The relatively lipophilic solvent 2-methyl-2,4-pentanediol (MPD) gives a sponge phase at about 60 wt.% water compared with 30 wt.% for the sponge phase formed with polyethylene glycol (M w ≈400, PEG 400). A reasonably good correlation is found between the water content of the sponge phase and the octanol/water partition coefficient for the solvent. The water content of the PEG 400 sponge phase increases considerably (to about 50 wt.%) by adding up to 3 wt.% of ionic compounds such as SDS, CTAB and salts of amphiphilic drugs. Nonionic detergents show less effect on increasing the water content, whereas membrane lipids such as lecithins and cholesterol show unchanged or even decreasing effect on the water content of the sponge phase.

Microstructures formed in aqueous solutions of a hydrophobically modified nonionic cellulose derivative and sodium dodecyl sulfate: a fluorescence probe investigation

Microstructures formed in aqueous solutions of a hydrophobically modified nonionic cellulose derivative and sodium dodecyl sulfate: a fluorescence probe investigation

Interaction Between Lactate Dehydrogenase and Tween 80 in Aqueous Solution

AbstractPurpose. The weak aqueous interaction between the protein lactate dehydrogenase (LDH) and the nonionic surfactant Tween 80 has been investigated, because weak protein-amphiphile interactions are of significant importance in pharmaceutical formulations, but are experimentally hard to determine. The system LDH/sodium dodecyl sulphate (SDS) was used as reference because SDS, by its strong protein binding, denatures LDH completely. Methods. Fluorescence spectroscopy with pyrene and 1,3-bis(1-phenyl)propane (P3P) as probes, intrinsic protein fluorescence and NMR spectroscopy have been used. Results. The fluorescence probe pyrene monitors a weak Tween-LDH interaction, detectable below the critical micelle concentration of ordinary Tween micelles. The microviscosity probe P3P shows a surfactant-induced denaturation in the case of LDH/SDS but not in the case of LDH/Tween 80. Intrinsic LDH fluorescence verifies this behavior. Pulsed-gradient spin-echo NMR was also used to verify the weak LDH-Tween 80 interaction. Conclusions. A weak interaction between LDH and Tween 80 occurs at hydrophobic zones of the protein, but it is not strong enough to denature LDH. The experimental outline used here provides a useful approach for mapping the very weak protein-amphiphile interactions often present in pharmaceutical formulations.

Microviscosity in dilute aqueous solutions of SDS and non-ionic cellulose derivatives of different hydrophobicity: fluorescence probe investigations

Microviscosity in dilute aqueous solutions of SDS and non-ionic cellulose derivatives of different hydrophobicity: fluorescence probe investigations