Influence of Polymorphic Transformations on Gelation of Tripalmitin Solid Lipid Nanoparticle Suspensions |
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Authors: | T Helgason T S Awad K Kristbergsson D J McClements J Weiss |
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Affiliation: | (1) Department of Food Science, University of Iceland, Hjardarhagi 2-6, 107 Reykjavik, Iceland;(2) Department of Food Science, University of Massachusetts, 100 Holdsworth Way, Amherst, MA 01003, USA |
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Abstract: | Solid lipid nanoparticle (SLN) suspensions, which consist of submicron-sized crystalline lipid particles dispersed within
an aqueous medium, can be used to encapsulate, protect and deliver lipophilic functional components. Nevertheless, SLN suspensions
are susceptible to particle aggregation and gelation during their preparation and storage, which potentially limits their
industrial utilization. In this study, we examined the aggregation and gelation behavior of SLN suspensions composed of 10 wt%
tripalmitin particles (r < 150 nm) stabilized by 1.5% Tween 20. The tripalmitin and aqueous surfactant solution were homogenized above the lipid melting
temperature and cooled under controlled conditions to initiate SLN formation. The aggregation and gelation of SLN suspensions
during storage was then examined by shear rheometry, differential scanning calorimetry (DSC), light scattering and microscopy.
Rheology measurements indicated that gelation times decreased with increasing storage temperature, e.g., samples formed weak
gels after 62, 23, and 10 min at 1, 5, and 10 °C, respectively. DSC revealed increasingly rapid α- to β-polymorphic transformations
in SLN dispersions stored at 1, 5, and 10 °C, respectively. We propose that the observed aggregation and gelation of SLN suspensions
are associated with a change in the shape of the nanoparticles from spherical (α-form) to non-spherical (β-form) when they
undergo the polymorphic transition. When they change shape there is no longer sufficient surfactant present to completely
cover the lipid phase, which promotes particle aggregation through hydrophobic attraction. Our results have important implications
for the design and fabrication of stable SLN suspensions. |
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Keywords: | Solid lipid nanoparticles Encapsulation Polymorphic transformations |
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