Skin penetration and tumor specific cellular uptake of tecto-dendrimer nanoparticles as a new strategy for targeted delivery by topical application

A. BOREHAM; C. ZOSCHKE; P. SCHILRREFF; R. BRODWOLF; E.L. ROMERO; U. ALEXIEV; M. SCHÄFER-KORTING

Encuentro; 13th Meeting of the European Epidermal Barrier Research Network.; 2015

Dendritic nanoparticles possess many characteristics,such as high loading capacity for guest molecules and tunable end groups facilitating surface functionalizing, that have brought them into the focus as a new treatment option for therapy-resistant diseases. High recurrence rates of cutaneous squamous cell carcinoma (cSCC) indicate limited efficacy of currently available treatment. cSCC poses a deadly risk for immunocompromised patients, since the initial carcinoma in-situ (actinic keratosis, Morbus Bowen) often progresses into invasive and metastatic tumour(cSCC) [1]. Nanoparticles can enhance poor skin penetration of topically applied agents [2], andtecto-dendrimer nanoparticles even induced selective toxicity to a melanoma cell line [3]. However the skin penetration and toxicity of the dendritic nanoparticle itself remains unknown.Here, we report on an investigation of skin penetration and cellular uptake of fluorescently labelled (FITC)tecto-dendrimer(G5.G2.5) nanoparticles [3] into reconstructed human skin and an organotypic cSCC model. For visualization of the local distribution of tecto-dendrimers in the skin a new Fluorescence Lifetime Imaging Microscopy (FLIM) technique [4,5] was applied. This technique combines information from excited-state fluorescence decay curves of the fluorescing molecules with a sophisticated analysis method that uses multivariate analysis algorithm identifying unique fluorescence lifetime species.Analysis of sections from reconstructed human skin showed no penetration of tecto-dendrimer nanoparticles into the skin. In sections from the organotypic model for cSCC, however, a penetration of the tecto-dendrimer nanoparticles into the viable epidermis of the skin was observed. The regions of concentrated uptake appeared to correlate with the occurrence of ?tumor nest? within the organotypic cSCC model. Therefore, monolayer cell experiments were performed to confirm the selective uptake of tecto-dendrimer nanoparticlesintotumor cells.While the tecto-dendrimer nanoparticles remain in the membrane of normal keratinocytes, squamous cell carcinoma (SCC) cells take up the particles into the cytoplasm via an active process. As both the SCC cell line and the organotypic model for cSCC show specific uptake of the tecto-dendrimer nanoparticles into tumor cells, there is a huge potential for these tecto-dendrimer nanoparticles in targeted delivery by topical application.