Photochemical internalization of tamoxifens transported by a "Trojan-horse" nanoconjugate into breast-cancer cell lines.

Photochemical internalization (PCI) has shown great promise as a therapeutic alternative for targeted drug delivery by light-harnessed activation. However, it has only been applicable to therapeutic macromolecules or medium-sized molecules. Herein we describe the use of an amphiphilic, water-soluble porphyrin-β-cyclodextrin conjugate (mTHPP-βCD) as a "Trojan horse" to facilitate the endocytosis of CD-guest tamoxifens into breast-cancer cells. Upon irradiation, the porphyrin core of mTHPP-βCD expedited endosomal membrane rupture and tamoxifen release into the cytosol, as documented by confocal microscopy. The sustained complexation of mTHPP-βCD with tamoxifen was corroborated by 2D NMR spectroscopy and FRET studies. Following the application of PCI protocols with 4-hydroxytamoxifen (4-OHT), estrogen-receptor β-positive (Erβ+, but not ERβ-) cell groups exhibited extensive cytotoxicity and/or growth suspension even at 72 h after irradiation.