Structure Analysis of Solid Lipid Nanoparticles for Drug Delivery: A Combined USANS/SANS Study

Abstract

Suspensions of solid lipid nanoparticles (SLNs) stabilized with emulsifiers have been extensively investigated (since the 1990s) as drug carriers, although details of their ultrastructure are poorly defined. Previously, a novel microwave‐assisted microemulsion‐based technique to prepare SLNs was reported. To understand the detailed internal structure of these SLNs, ultra‐small angle neutron scattering (USANS) and small angle neutron scattering (SANS) experiments are conducted on suspensions of hydrogenated stearic acid SLNs stabilized with hydrogenated Tween 20 surfactant in D2O. Together, SANS and USANS gives a combined Q range of 0.000047 to 0.6 Å−1 (corresponding to a size range of ≈1 nm–15 µm). This extended Q range allows a comprehensive understanding of the hierarchical structure of SLNs. The data are consistent with the multi‐length scale structure of SLNs having polydispersed large particles with roughened surfaces at the microscale level. At the nanoscale level, the results are consistent with the SLNs having an ellipsoidal shape intermediate between spheres and rods, with a crossover from mass fractals to surface fractals. The elucidation of this structure is particularly important given that the structure influences the stability and drug release properties of the nanoparticles. These results assist in the development of systems with desired shape and properties.

On the Structure of Solid Lipid Nanoparticles

“…Figure shows the variation in the total measured scattering with the scattering vector ( Q ) for the SLNs diluted to a final concentration of 0.8 wt% TPN and 2 wt% C 18:1 E 10 in D 2 O. Analysis of the SANS data showed that the SLNs were not spherical, but instead were oblate, as the major and minor axis are different lengths (see the Supporting Information), as has been previously reported from SANS data of steric acid and Tween20 SLNs . In the context of the present study, spherical SLN are generally associated with the α‐form polymorph while the β‐form typically corresponds to platelet shaped SLN.…”

Solid Lipid Nanoparticles for Drug Delivery: Pharmacological and Biopharmaceutical Aspects

“…When firstly developed, SLN were presented as tiny and spherical particles, made of solid lipids at room temperature, that may be thought as perfect crystal lipid matrices, able to accommodate a drug or other molecules between fatty acid chains (Puri et al, 2009). Nowadays, however, it is known that this is not necessarily true in all cases, since disc-like shape or flat ellipsoidal geometry have also been described (Mazuryk et al, 2016;Shah et al, 2019). Moreover, the loaded drug may be attached mostly to the carrier matrix surface instead of being embedded into the solid core (Pink et al, 2019;Shah et al, 2019).…”

“…Nowadays, however, it is known that this is not necessarily true in all cases, since disc-like shape or flat ellipsoidal geometry have also been described (Mazuryk et al, 2016;Shah et al, 2019). Moreover, the loaded drug may be attached mostly to the carrier matrix surface instead of being embedded into the solid core (Pink et al, 2019;Shah et al, 2019).…”

Impairing Proliferation of Glioblastoma Multiforme with CD44+ Selective Conjugated Polymer Nanoparticles

“…1b-d). 29,30 This analysis gives insight to the shape and size of particles based on the Porod exponent (d), dimensionality (s), and radius of gyration (Rg). Fits to HA-CPNs yielded d = 4.2 ± 0.02 and s = 0.02 ± 0.06, which strongly correlates to a hard sphere with a smooth surface (d = 4 and s = 0).…”