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The adsorption of charged particles to hydrogel surfaces is important in a number of natural and industrial processes. In this study, the adsorption of cationic lipid droplets to the surfaces of anionic hydrogels was examined. An oil-in-water emulsion containing cationic -lactoglobulin-coated lipid droplets was prepared (d320.24 m, 74 mV, pH 3.0). An anionic hydrogel containing 0.1 wt % beet pectin and 1.5 wt % agar (pH 3.0) was prepared. Emulsions containing different lipid droplet concentrations (0.3−5 wt %) were brought into contact with the hydrogel surfaces for different times (0−24 h). The adsorption of lipid droplets to the hydrogel surfaces could not be explained by a typical adsorption isotherm. We found that the electrical charge on the nonadsorbed lipid droplets became less positive or even became negative in the presence of the hydrogel and that extensive droplet aggregation occurred, which was attributed to the ability of pectin molecules to diffuse through the hydrogels and interact with the lipid droplets. These results may have important consequences for understanding certain industrial and biological processes, as well as for the design of controlled or triggered release systems. [ABSTRACT FROM AUTHOR]

We examined the effect of lipid phase composition on the crystallization, polymorphic transition and stability of solid lipid nanoparticle (SLN) suspensions. A series of fine-disperse oil-in-water emulsions was prepared at an elevated temperature (75 °C) from a lipid phase containing different amounts of a high melting lipid (tripalmitin) and a low melting lipid (fish oil). These emulsions were cooled to induce crystallization and form SLN suspensions. In the absence of fish oil, the SLN suspensions formed a gel after the emulsified tripalmitin crystallized, which was attributed to particle shape changes leading to aggregation and network formation. Light scattering and rheology measurements indicated that incorporation of fish oil into the lipid phase (≥10 wt %) increased the stability of SLN to aggregation. DSC measurements suggested that crystallization, melting, and polymorphic transitions of SLN were influenced by the amount of fish oil incorporated. The rate of α- to β-polymorphic transitions of tripalmitin increased with increasing fish oil content, and tripalmitin crystals formed appeared to be less ordered as evidence by a lower melting temperature. Results suggest that the phase behavior and morphology of tripalmitin crystals can be altered by mixing them with low melting lipids such as fish oil thereby improving the stability of SLN suspensions to particle aggregation and gelation. Moreover, results show that fish oil, rich in ω-3 polyunsaturated fatty acids, can be successfully incorporated into SLN suspensions. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine whether temperature scanning ultrasonic velocity measurements could be used to monitor the complex thermal transitions that occur during the crystallization and melting of triglyceride solid lipid nanoparticles (SLNs). Ultrasonic velocity ( u) measurements were compared with differential scanning calorimetry (DSC) measurements on tripalmitin emulsions that were cooled (from 75 to 5 °C) and then heated (from 5 to 75 °C) at 0.3 °C min −1. There was an excellent correspondence between the thermal transitions observed in δΔ u/δ Tversus temperature curves determined by ultrasound and heat flow versus temperature curves determined by DSC. In particular, both techniques were sensitive to the complex melting behavior of the solidified tripalmitin, which was attributed to the dependence of the melting point of the SLNs on particle size. These studies suggest that temperature scanning ultrasonic velocity measurements may prove to be a useful alternative to conventional DSC techniques for monitoring phase transitions in colloidal systems. [ABSTRACT FROM AUTHOR]