Structural effects of the dispersing agent polysorbate 80 on liquid crystalline nanoparticles of soy phosphatidylcholine and glycerol dioleate

Abstract

Well-defined, stable and highly structured I2 (Fd3̅m) liquid crystalline nanoparticles (LCNP) of 50/50 (wt/wt) soy phosphatidylcholine (SPC)/glycerol dioleate (GDO), can be formed by using a low fraction (5-10 wt%) of the dispersing polymeric surfactant polyoxyethylene (20) sorbitan monooleate (polysorbate 80 or P80). In the present study we used small angle neutron scattering (SANS) and deuterated P80 (d-P80) to determine the location and concentration of P80 within the LCNP and small angle X-ray scattering (SAXS) to reveal the internal structure. SANS data suggests that some d-P80 already penetrates the particle core at 5%. However, the content of d-P80 is still low enough not to significantly change the internal Fd3̅m structure of the LCNP. At higher fractions of P80 a phase separation occurs, in which a SPC and P80 rich phase is formed at the particle surface. The surface layer becomes gradually richer in both solvent and d-P80 when the surfactant concentration is increased from 5 to 15%, while the core of the particle is enriched by GDO, resulting in loss of internal structure and reduced hydration. We have used neutron reflectometry to reveal the location of the stabiliser within the adsorbed layer on an anionic silica and cationic (aminopropyltriethoxysilane (APTES) silanized) surface. d-P80 is enriched closest to the supporting surface and slightly more so for the cationic APTES surface. The results are relevant not only for the capability of LCNPs as drug delivery vehicles but also as means of preparing functional surface coatings.

Interfacial properties of lipid sponge-like nanoparticles and the role of stabilizer on particle structure and surface interactions

“…This effect is rather pronounced at high P80 concentrations, where even the loss of internal particle structure can occur. 22,25 In our earlier work 13 with the same DGMO/GMO-50/P80/water system as studied here, we were also able to form nanoparticles with highly swollen sponge phase structures over a wider range than in the pure lipid-aqueous system. Cryo-TEM imaging showed that such phases could be dispersed into sponge-like nanoparticles (L 3 -NPs) that featured a dense sponge phase core with swollen bilayer structures at the interface.…”

“…Soy phosphatidylcholine (SPC)/glycerol dioletate (GDO)/polysorbate 80 (P80) LCNP were found to form lipid multilayers on anionic silica that increase in thickness with P80 concentration. 22,24 However on cationic silica, intact LCNP were found to deposit without being dependent on the P80 concentration.…”

“…[15][16][17] The interfacial properties of cubosomes and hexosomes have been examined to understand the nature of the interactions between these LCNP and different interfaces that mimic storage or administration vessels, such as glass vials, catheters or syringes. [18][19][20][21][22] The adsorption behaviour was observed to depend on the environmental conditions (pH, ionic strength), the surface properties (such as hydrophilicity/phobicity or charge) and the lipid system used to form the LCNP. Vandoolaeghe et al 19,23 studied the adsorption of glycerol monolein (GMO)/ pluronic F127 cubosomes on hydrophilic and hydrophobic silica at different conditions.…”

Challenges, Issues and Warnings from CLSI and EUCAST Working Group on Polymyxin Susceptibility Testing

“…The addition of Polysorbate-80 (P-80), a surfactant, prevents to some extent the binding of polymyxin to microtiter plate [4]. However, CLSI or EUCAST guidelines never approved the use of P-80 for colistin or polymyxin B ST.…”

“…In vitro ST of colistin is challenging and is influenced by: i) multicomponent composition of colistin; ii) cationic property of colistin attributes for adherence to the microtiter plate; iii) heteroresistance to colistin [1] Adherence of colistin or polymyxin B to microtiter plates is reported as the major technical issues by many investigators across the world [3]. The addition of Polysorbate-80 (P-80), a surfactant, prevents to some extent the binding of polymyxin to microtiter plate [4]. However, CLSI or EUCAST guidelines never approved the use of P-80 for colistin or polymyxin B ST.…”