Upconversion (UC) nanoparticles characterized by red upconversion emission, particularly interesting for biological applications, have been prepared and subsequently modified by the covalent anchoring of Verteporfin (Ver), an FDA approved photosensitizer (PS) which usually exerts its photodynamic activity upon excitation with red light. ZrO2 was chosen as the platform where Yb3+ and Er3+ were inserted as the sensitizer and activator ions, respectively. Careful control of the doping ratio, along with a detailed physico-chemical characterization, was carried out. Upon functionalization with a silica shell to covalently anchor the photosensitizer, a theranostic nanoparticle was obtained whose architecture, thanks to a favorable energy level match and a uniform distribution of the PS, allowed us to trigger the photodynamic activity of Ver by upconversion, thus paving the way to the use of Photodynamic Therapy (PDT) in deep tissues, thanks to the higher penetrating power of NIR light.
Keywords: core–shell nanoparticles; lanthanide doped nanoparticles; optical imaging; photodynamic therapy; red upconverter nanoparticles; theranostic; upconversion.