Nanomaterials fusing with the skin: Alpha-tocopherol phosphate delivery into the viable epidermis to protect against ultraviolet radiation damage

Mais M. Saleh, Arcadia Woods, Richard D. Harvey, Antony R. Young, Stuart A. Jones*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

Vitamin E (alpha tocopherol, α-T) is an important skin antioxidant, but its penetration into the viable epidermis, where it acts, is very limited. This study investigated if phosphorylating α-tocopherol (α-TP) to form a provitamin, improved its interactions with skin, its passage into the tissue, and thus its ability to protect the skin from ultraviolet radiation (UVR) damage. At pH 7.4, when the α-TPO4−1 microspecies predominated in solution, dynamic light scattering measurements showed that α-TP formed nanoaggregates with a median hydrodynamic diameter of 9 nm (Critical aggregation constant, CAC, – 4.2 mM). At 9.0 when the α-TPO4−2 microspecies predominated there was no aggregation. The passage of α-TP nanoaggregates through regenerated cellulose membranes was significantly slower than the α-TP monomers (at pH 9) suggesting that aggregation slowed diffusion. However, a lotion formulation containing the nanoaggregates delivered more α-TP into the skin compared to the formulation containing the monomers. In addition, the nanosized α-TP aggregates delivered 8-fold more active into the stratum corneum (SC) (252.2 μg/cm2 vs 29.5 μg/cm2) and 4 fold more active into the epidermis (85.1 μg/cm2 vs 19 μg/cm2, respectively, p < 0.05) compared to α-T. Langmuir subphase injection studies at pH 7.4 (surface pressure 10 mN m−1) showed that the α-TP nanoaggregates more readily fused with the SC compared to the monomers and the membrane compression studies demonstrated that α-TP fluidised the SC lipids. Together the fusion with the SC and its fluidisation were proposed as the causes of the better α-TP penetration into the skin, which enhanced potential of α-TP to protect from UVR-induced skin damage compared to α-T.

Original languageEnglish
Article number120000
JournalINTERNATIONAL JOURNAL OF PHARMACEUTICS
Volume594
DOIs
Publication statusPublished - 1 Feb 2021

Keywords

  • Delivery
  • Liposomes
  • Nanomaterials
  • Skin
  • Skin interactions
  • Stratum corneum
  • α-Tocopherol phosphate

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