A comparison of emulsifiers for the formation of oil-in-water emulsions: stability of the emulsions within 9 h after production and MR signal properties

Abstract

Objective To provide a basis for the selection of suitable emulsifiers in oil-in-water emulsions used as tissue analogs for MRI experiments. Three different emulsifiers were investigated with regard to their ability to stabilize tissue-like oil-in-water emulsions. Furthermore, MR signal properties of the emulsifiers themselves and influences on relaxation times and ADC values of the aqueous phase were investigated. Materials and methods Polysorbate 60, sodium dodecyl sulfate (SDS) and soy lecithin were used as emulsifiers. MR characteristics of emulsifiers were assessed in aqueous solutions and their function as a stabilizer was examined in oil-in-water emulsions of varying fat content (10, 20, 30, 40, 50%). Stability and homogeneity of the oil-in-water emulsions were evaluated with a delay of 3 h and 9 h after preparation using T1 mapping and visual control. Signal properties of the emulsifiers were investigated by 1H-MRS in aqueous emulsifier solutions. Relaxometry and diffusion weighted MRI (DWI) were performed to investigate the effect of various emulsifier concentrations on relaxation times (T1 and T2) and ADC values of aqueous solutions. Results Emulsions stabilized by polysorbate 60 or soy lecithin were stable and homogeneous across all tested fat fractions. In contrast, emulsions with SDS showed a significantly lower stability and homogeneity. Recorded T1 maps revealed marked creaming of oil droplets in almost all of the emulsions with SDS. The spectral analysis showed several additional signals for polysorbate and SDS. However, lecithin remained invisible in 1H-MRS. Relaxometry and DWI revealed different influences of the emulsifiers on water: Polysorbate and SDS showed only minor effects on relaxation times and ADC values of aqueous solutions, whereas lecithin showed a strong decrease in both relaxation times (r1,lecithin = 0.11 wt.%−1 s−1, r2,lecithin = 0.57 wt.%−1 s−1) and ADC value (Δ(ADC)lecithin = − 0.18 × 10–3 mm2/s⋅wt.%) with increasing concentration. Conclusion Lecithin is suggested as the preferred emulsifier of oil-in-water emulsions in MRI as it shows a high stabilizing ability and remains invisible in MRI experiments. In addition, lecithin is suitable as an alternative means of adjusting relaxation times and ADC values of water.

Evaluating the Stability of Cellulose Nanofiber Pickering Emulsions Using MRI and Relaxometry

“…Importantly, they report on different lengths and timescales and so report on different aspects of the molecular dynamics involved in stabilizing the Pickering emulsions. Unlike the surfactants in molecular-based oil-inwater emulsions, which altered the T 1 , T 2 , and ADC of water depending on the concentrations, 20 those relaxation and diffusion properties of the serum layer were consistent with each bulk sample regardless of the CNF concentration and storage time. The T 1 distribution in the d-CNF emulsion layer changed over one month of storage, indicating microstructural changes such as flocculation and coalescence.…”

“…Several recent studies demonstrated that the distributions of water or fat with varying T 1 and/or T 2 relaxation times as visualized in MRI maps allowed evaluation of creaming and gravitational separation. , MRI and NMR are also useful for analyzing industrial emulsions such as for measuring droplet size distributions . Fritz et al investigated ADC values of water in oil-in-water emulsions emulsified with three different molecular surfactants. They suggested that the surfactant limits the water mobility and the degree of limitation depends on the surfactants and their concentrations.…”

“…20,21 MRI and NMR are also useful for analyzing industrial emulsions such as for measuring droplet size distributions. 22 Fritz et al 20 investigated ADC values of water in oil-in-water emulsions emulsified with three different molecular surfactants. They suggested that the surfactant limits the water mobility and the degree of limitation depends on the surfactants and their concentrations.…”

Short‐Term Variability of Proton Density Fat Fraction in Pancreas and Liver Assessed by Multiecho Chemical‐Shift Encoding‐Based MRI at 3 T

“…Soy lecithin was used as an emulsifier to obtain stable and homogenous emulsions. 23 The tubes were placed in horizontal direction in a water bath. Sequence parameters were identical to the in vivo measurements except TR, which was set to 20 msec to avoid T1-bias.…”

“…Emulsions were prepared in CELLSTAR polypropylene tubes (Greiner Bio‐One, Frickenhausen, Germany) with a volume of 50 mL, filled with distilled water and peanut oil. Soy lecithin was used as an emulsifier to obtain stable and homogenous emulsions 23 . The tubes were placed in horizontal direction in a water bath.…”