Squarticles as a lipid nanocarrier for delivering diphencyprone and minoxidil to hair follicles and human dermal papilla cells

Abstract

Delivery of diphencyprone (DPCP) and minoxidil to hair follicles and related cells is important in the treatment of alopecia. Here we report the development of "squarticles," nanoparticles formed from sebum-derived lipids such as squalene and fatty esters, for use in achieving targeted drug delivery to the follicles. Two different nanosystems, nanostructured lipid carriers (NLC) and nanoemulsions (NE), were prepared. The physicochemical properties of squarticles, including size, zeta potential, drug encapsulation efficiency, and drug release, were examined. Squarticles were compared to a free control solution with respect to skin absorption, follicular accumulation, and dermal papilla cell targeting. The particle size of the NLC type was 177 nm; that of the NE type was 194 nm. Approximately 80% of DPCP and 60% of minoxidil were entrapped into squarticles. An improved drug deposition in the skin was observed in the in vitro absorption test. Compared to the free control, the squarticles reduced minoxidil penetration through the skin. This may indicate a minimized absorption into systemic circulation. Follicular uptake by squarticles was 2- and 7-fold higher for DPCP and minoxidil respectively compared to the free control. Fluorescence and confocal images of the skin confirmed a great accumulation of squarticles in the follicles and the deeper skin strata. Vascular endothelial growth factor expression in dermal papilla cells was significantly upregulated after the loading of minoxidil into the squarticles. In vitro papilla cell viability and in vivo skin irritancy tests in nude mice suggested a good tolerability of squarticles to skin. Squarticles provide a promising nanocarrier for topical delivery of DPCP and minoxidil.

Fig. 1

Comparison of the skin deposition (μg/g) of DPCP and minoxidil in intact skin and sebum-removal skin after in vitro application by aqueous control and squarticles. *p < 0.05 compared to intact skin. All data represent the mean ± SD of four experiments

Fig. 2

Released amount versus time profiles of DPCP (a) and minoxidil (b) across cellulose membrane (Cellu-Sep® T1 with a molecular weight cutoff of 3,500) after in vitro application by aqueous control and squarticles. All data represent the mean ± SD of four experiments

Fig. 3

VEGF expression in supernatant and extract of human dermal papilla cells after incubation with minoxidil (0.01 M) in aqueous control and squarticles. All data represent the mean ± SD of six experiments

Fig. 4

Fluorescence microscopic images of nude mouse skin with in vivo topical administration of aqueous control (a), squarticles in NLC type (b), and squarticles in NE type (c) containing Nile red (0.1%) as a dye for 6 h. The upper panel is the fluorescence image detected at 546 and 590 nm for excitation and emission; the lower panel is the bright-field view of H&E-stained images

Fig. 5

Confocal micrographs of nude mouse skin at an original magnification of ×630 with non-treatment (blank) (a), in vivo topical administration of aqueous control (b), squarticles in NLC type (c), and squarticles in NE type (d) containing Nile red (0.1%) as a dye for 6 h. The image is a summary of 15 fragments at various skin depths

Fig. 6

Viability of human dermal papilla cells after incubation with aqueous control and squarticles at different concentrations. All data represent the mean ± SD of six experiments

Fig. 7

In vivo skin irritation examination determined by ∆transepidermal water loss (∆TEWL; a), ∆erythema (∆a*; b), and ∆skin pH (c) after a 7-day application of aqueous control and squarticles. All data represent the mean ± SD of six experiments