Abstract
Photodynamic therapy (PDT) is a non-invasive treatment strategy that includes the combination of three components—a photosensitizer, a light source, and tissue oxygen. PDT can be used for the treatment of skin diseases such as squamous cell carcinoma. The photosensitizer used in this study is the naturally derived chlorophyll derivative chlorin e6 (Ce6), which was encapsulated in ultradeformable ethosomes. Singlet oxygen production by Ce6 upon laser light irradiation was not significantly affected by encapsulation into ethosomes. PDT of squamous cell carcinoma cells treated with Ce6 ethosomes triggered increased mitochondrial superoxide levels and increased caspase 3/7 activity, resulting in concentration- and light-dose-dependent cytotoxicity. Ce6 ethosomes showed good penetration into 3D squamous cell carcinoma spheroids, which upon laser light irradiation exhibited reduced size, proliferation, and viability. The PDT effect of Ce6 ethosomes was specific and showed higher cytotoxicity against squamous cell carcinoma spheroids compared to normal skin fibroblast spheroids. In addition, PDT treatment of squamous cell carcinoma xenografts grown on chorioallantoic membranes of chick eggs (CAM) exhibited reduced expression of Ki-67 proliferation marker and increased terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) staining, indicating reduced proliferation and activation of apoptosis, respectively. The results demonstrate that Ce6-loaded ethosomes represent a convenient formulation for photodynamic treatment of squamous cell carcinoma.
Highlights
Non-melanoma skin cancers are the most common types of skin malignancies in Caucasians
The chlorin e6 (Ce6) ethosomes are spheric particles measuring about 500 nm with a negative surface charge, which is due to the exposure of negatively charged groups of phospholipids
An amount of 0.0186 mg of Ce6 was encapsulated per mg of ethosomes
Summary
Non-melanoma skin cancers are the most common types of skin malignancies in Caucasians. They include squamous cell carcinoma, the second most common type of skin cancer after basal cell carcinoma [1,2]. Photodynamic therapy (PDT) is a non-invasive therapy based on the activation of a light-sensitive drug—a photosensitizer—by light of a specific wavelength. Since PDT is a light-triggered process, the photodynamic reaction can be restricted to the light-exposed area; it is safer than chemotherapy [4]. PDT is used in a wide range of therapeutic fields, especially in cancer, where selective production of 1O2 in target tissue and preferential accumulation of photosensitizer ( when incorporated into larger carrier particles) in tumors through enhanced permeation and retention effect (EPR) add to its specificity [4,5,6,7]
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