Original Article
Anti-PDGF receptor β antibody-conjugated squarticles loaded with minoxidil for alopecia treatment by targeting hair follicles and dermal papilla cells

https://doi.org/10.1016/j.nano.2015.04.009Get rights and content

Abstract

This study developed lipid nanocarriers, called squarticles, conjugated with anti-platelet-derived growth factor (PDGF)-receptor β antibody to determine whether targeted Minoxidil (MXD) delivery to the follicles and dermal papilla cells (DPCs) could be achieved. Squalene and hexadecyl palmitate (HP) were used as the matrix of the squarticles. The PDGF-squarticles showed a mean diameter and zeta potential of 195 nm and − 46 mV, respectively. Nanoparticle encapsulation enhanced MXD porcine skin deposition from 0.11 to 0.23 μg/mg. The antibody-conjugated nanoparticles ameliorated follicular uptake of MXD by 3-fold compared to that of the control solution in the in vivo mouse model. Both vertical and horizontal skin sections exhibited a wide distribution of nanoparticles in the follicles, epidermis, and deeper skin strata. The encapsulated MXD moderately elicited proliferation of DPCs and vascular endothelial growth factor (VEGF) expression. The active targeting of PDGF-squarticles may be advantageous to improving the limited success of alopecia therapy.

From the Clinical Editor

Topical use of minoxidil is only one of the very few treatment options for alopecia. Nonetheless, the current delivery method is far from ideal. In this article, the authors developed lipid nanocarriers with anti-platelet-derived growth factor receptor ? antibody to target dermal papilla cells, and showed enhanced uptake of minoxidil.

Graphical Abstract

Selective delivery of minoxidil (MXD) to the hair follicles is important for treating alopecia with reduced adverse effect and systemic absorption. The final target of MXD delivery should reach the lower infundibulum where the dermal papilla cells (DPCs) reside. In this work, we chose the PDGF receptor as a target for MXD-loaded nanoparticles as it was capable of specifically delivering MXD to the DPCs in the hair follicles. The experimental results demonstrated that PDGF-squarticles are an active targeting nanocarrier that could largely deposit in the follicles and penetrate into the DPCs to induce proliferation and VEGF release.

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Introduction

Androgenetic alopecia (AGA) is one of the most common chronic problems in dermatology caused by the progressive loss and thinning of the scalp hair. Despite the high prevalence of alopecia, there are limited options for approved drug treatment.1 Topical application of 5% minoxidil (MXD) is currently the first-line therapy for AGA.2 This drug directly induces proliferation of the dermal papilla cells (DPCs) and exerts a vasodilator effect on the hair follicles.3 However, a recommended twice-daily administration may produce adverse reactions such as scalp dryness, burning, redness, and contact dermatitis. Alcohol and propylene glycol (PG) commonly employed in the commercial products of MXD also cause skin irritation.4 A long-term application (6-8 weeks) is needed to see improvement in hair loss.5 It is therefore essential to find an efficient way to enhance drug delivery into targeted lesions and minimize distribution in normal tissues.

Nanocarriers provide a strategy for delivering the drugs to the hair follicles. Recently we introduced “squarticles,” nanostructured lipid carriers (NLCs) containing squalene and Precirol® as the lipid cores, for promoting drug uptake in the follicles.6 Squarticles largely accumulate in the follicles due to the interaction with sebum, which is rich in squalene. Although the employment of nanoparticles can increase drug delivery into the follicles, triggering pharmacological activity is of no use if the drug cannot reach the targeted cells. To achieve active targeting to the selected cells, antibody–nanoparticle conjugates are designed to bind the cells via overexpressed antigens on the membrane. The main targets of MXD are DPCs, which are regional stem cells regulating hair development and growth.7 Previous studies8, 9 have found that DPCs express platelet-derived growth factor (PDGF) receptor β. This receptor can be a promising therapeutic target for MXD-loaded nanoparticles.

We aimed to design squarticles with a targeting moiety of anti-PDGF receptor β antibody toward DPCs. To this end, in vitro and in vivo experiments for improving the targeted capability of PDGF-squarticles to the hair follicles and DPCs were performed. Sebum consists of wax esters with a percentage of ~ 25%.10 In this study, hexadecyl palmitate (HP) was used as the solid lipid of squarticles to replace Precirol® employed in our previous work.6 It is hypothesized that HP, a waxlike substance, further increases the interaction of squarticles with the sebum in the follicles. Both porcine and nude mouse skins were utilized as the permeation barriers in this report. Porcine skin is a good permeation model due to its close resemblance to human skin.11 The scalp skin appears to be more permeable than the other anatomic sites, especially in alopecia patients.12 Nude mouse skin offered a skin model with less barrier function.

Section snippets

Preparation of squarticles

The aqueous phase of the squarticles consisted of water (85.4% of the final product), Pluronic F68 (3.5%), and deoxycholic acid (1.0%). The lipid phase consisted of squalene (2.0%), HP (6.0%), SPC (1.5%), and MXD (0.6%). The two phases were separately heated to 85 °C for 15 min. The aqueous phase was added into the lipid phase and homogenized at 12,000 rpm for 20 min. A probe-type sonicator set at a power of 35 W was used to further mix the dispersions for 15 min.

Preparation of PDGF-squarticles

Squarticles (1 ml) were incubated with

Physicochemical characterization of the nanoparticles

The electrophoresis profiles in Figure 1, A show a band for the anti-PDGF receptor antibody with a molecular weight (MW) of ~ 130 kDa. This value approximated the MW described in the manufacturer’s guide (124 kDa). The band of PDGF-squarticles became less mobile in the electric field than the unbound antibody, suggesting the successful covalent binding between the antibody and the nanoparticles. The attachment of the antibody to the nanoparticulate surface was also checked by fluorescence

Discussion

In this work, we chose the PDGF receptor as a target for MXD-loaded nanoparticles as it was capable of specifically delivering MXD to the DPCs in the hair follicles. The experimental results demonstrated that PDGF-squarticles are an active targeting nanocarrier that could largely deposit in the follicles and penetrate into the DPCs, thus a moderate proliferation and VEGF release can be expected. Antibody-conjugated nanoparticle interaction or immunization with skin cells, including epidermal

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