TY - JOUR

T1 - Effects of High Pressure on Internally Self-Assembled Lipid Nanoparticles

T2 - A Synchrotron Small-Angle X-ray Scattering (SAXS) Study

AU - Kulkarni, Chandrashekhar V

AU - Yaghmur, Anan

AU - Steinhart, Milos

AU - Kriechbaum, Manfred

AU - Rappolt, Michael

PY - 2016/11/2

Y1 - 2016/11/2

N2 - We present the first report on the effects of hydrostatic pressure on colloidally stabilized lipid nanoparticles enveloping inverse nonlamellar self-assemblies in their interiors. These internal self-assemblies were systematically tuned into bicontinuous cubic (Pn3m and Im3m), micellar cubic (Fd3m), hexagonal (H2), and inverse micellar (L2) phases by regulating the lipid/oil ratio as the hydrostatic pressure was varied from atmospheric pressure to 1200 bar and back to atmospheric pressure. The effects of pressure on these lipid nanoparticles were compared with those on their equilibrium bulk, nondispersed counterparts, namely, inverse nonlamellar liquid-crystalline phases and micellar solutions under excess-water conditions, using the synchrotron small-angle X-ray scattering (SAXS) technique. In the applied pressure range, induced phase transitions were observed solely in fully hydrated bulk samples, whereas the internal self-assemblies of the corresponding lipid nanoparticles displayed only pressure-modulated single phases. Interestingly, both the lattice parameters and the linear pressure expansion coefficients were larger for the self-assemblies enveloped inside the lipid nanoparticles as compared to the bulk states. This behavior can, in part, be attributed to enhanced lipid layer undulations in the lipid particles in addition to induced swelling effects in the presence of the triblock copolymer F127. The bicontinuous cubic phases both in the bulk state and inside lipid cubosome nanoparticles swell on compression, even as both keep swelling further upon decompression at relatively high pressures before shrinking again at ambient pressures. The pressure dependence of the phases is also modulated by the concentration of the solubilized oil (tetradecane). These studies demonstrate the tolerance of lipid nanoparticles [cubosomes, hexosomes, micellar cubosomes, and emulsified microemulsions (EMEs)] for high pressures, confirming their robustness for various technological applications.

AB - We present the first report on the effects of hydrostatic pressure on colloidally stabilized lipid nanoparticles enveloping inverse nonlamellar self-assemblies in their interiors. These internal self-assemblies were systematically tuned into bicontinuous cubic (Pn3m and Im3m), micellar cubic (Fd3m), hexagonal (H2), and inverse micellar (L2) phases by regulating the lipid/oil ratio as the hydrostatic pressure was varied from atmospheric pressure to 1200 bar and back to atmospheric pressure. The effects of pressure on these lipid nanoparticles were compared with those on their equilibrium bulk, nondispersed counterparts, namely, inverse nonlamellar liquid-crystalline phases and micellar solutions under excess-water conditions, using the synchrotron small-angle X-ray scattering (SAXS) technique. In the applied pressure range, induced phase transitions were observed solely in fully hydrated bulk samples, whereas the internal self-assemblies of the corresponding lipid nanoparticles displayed only pressure-modulated single phases. Interestingly, both the lattice parameters and the linear pressure expansion coefficients were larger for the self-assemblies enveloped inside the lipid nanoparticles as compared to the bulk states. This behavior can, in part, be attributed to enhanced lipid layer undulations in the lipid particles in addition to induced swelling effects in the presence of the triblock copolymer F127. The bicontinuous cubic phases both in the bulk state and inside lipid cubosome nanoparticles swell on compression, even as both keep swelling further upon decompression at relatively high pressures before shrinking again at ambient pressures. The pressure dependence of the phases is also modulated by the concentration of the solubilized oil (tetradecane). These studies demonstrate the tolerance of lipid nanoparticles [cubosomes, hexosomes, micellar cubosomes, and emulsified microemulsions (EMEs)] for high pressures, confirming their robustness for various technological applications.

U2 - 10.1021/acs.langmuir.6b03300

DO - 10.1021/acs.langmuir.6b03300

M3 - Journal article

C2 - 27782407

VL - 32

SP - 11907

EP - 11917

JO - Langmuir

JF - Langmuir

SN - 0743-7463

IS - 45

ER -