In vitro anti-melanoma activity of imiquimod in ultradeformable nanovesicles

Abstract

Background

The wide spectrum of antitumoral mechanisms of imiquimod (IMQ), made it a good candidate for topical therapy of melanoma. However, physicochemical properties make IMQ formulation a difficult task. Solubility and skin penetration of IMQ are increased when loaded into ultradeformable nanovesicles.

Objective

Survey the in vitro anti-melanoma activity of IMQ loaded into two types of ultradeformable nanovesicles: archaeosomes (UDA-IMQ) (containing sn-2,3 ether-linked phytanyl saturated archaeolipids extracted from Halorubrum tebenquichense) and liposomes lacking archaeolipids (UDL-IMQ).

Methods

We prepared and structurally characterized UDA-IMQ and UDL-IMQ. Cytotoxicity was determined on human melanoma cells (SK-Mel-28) and keratinocytes (HaCaT cells) by MTT assay and LDH release. The cellular uptake was determined by flow cytometry. Apoptosis/necrosis induction was determined by fluorescence microscopy after double staining with YO-PRO-1® and propidium iodide.

Results

Neither IMQ nor IMQ-nanovesicles reduced the viability of HaCaT cells; but UDL-IMQ (371 nm, −24 mV ζ potential, 31 µg IMQ/mg lipids) and UDA-IMQ (216 nm, −32 mV ζ potential, 61 µg IMQ/mg lipids) showed time and concentration-dependent cytotoxicity on SK-Mel-28 that resulted between 4 and 33 folds higher than free IMQ, respectively. While both UDA-IMQ and UDL-IMQ retained 60% of IMQ against dilution, UDA-IMQ uptaken by SK-Mel-28 cells was nine-fold higher than UDL-IMQ. UDL-IMQ induced early apoptosis, but UDA-IMQ induced both apoptosis and necrosis on SK-Mel-28 cells.

Conclusions

UDA-IMQ was innocuous to keratinocytes but was highly uptaken and induced apoptosis and necrosis on melanoma cells, being a candidate for future investigations as adjuvant topical anti-melanoma therapy.

Keywords:

• Intracellular delivery
• SK-Mel-28 cells
• apoptosis
• archaeolipids
• topical

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by Secretaria de Investigaciones, Universidad Nacional de Quilmes under Grant Nanomedicinas-2. ATC has fellowships from National Council for Scientific and Technological Research (CONICET). APP, ELR, and MJM are members of the Research Career Program from CONICET.