Covalently-linked Multifunctional Upconversion Nanoconjugates for Photodynamic Therapy and Imaging of Cancer Cells

By covalently binding NaYF4:Yb,Er nanoparticles (UCNPs) with the photosensitizer rose bengal (RB) and folic acid (FA), an upconversion nanoparticle platform for detection and treatment of tumors has been created. Compared to the more popular approach of electrostatic interaction, the present covalent approach makes the platform more rigid and resistant to the biological environment. Upon 980 nm CW irradiation, multicolor upconverted emission is generated by the UCNPs. The 650 nm emission is used for imaging the location of the particles while 540 nm upconverted emission serves to excite RB and generate singlet oxygen for photodynamic therapy. From the confocal images of JAR choriocarcinoma cells we have confirmed the target transfection of UCNPs mediated by the FA receptor. The present system thus has the potential to serve as a new platform for integrated photodynamic diagnosis and therapy, and for real-time reporting of therapeutic efficacy during treatment.