Optimized Rhodamine B labeled mesoporous silica nanoparticles as fluorescent scaffolds for the immobilization of photosensitizers: a theranostic platform for optical imaging and photodynamic therapy.

A highly efficient bifunctional mesoporous silica nanodevice coupling optical imaging with photodynamic therapy (PDT) was successfully prepared by using Rhodamine B as a contrast agent and verteporfin as a photosensitizer. The precise localization and high dispersion of the contrast agent in the nanoparticles is the key point to get higher fluorescence quantum yields with respect to the fluorophore in solution. To obtain this information photoluminescence spectroscopy coupled with fluorescence lifetime measurements was used, due to its high sensitivity. The bifunctional nanodevice showed good performances both in terms of quantum yield of the anchored Rhodamine B (Φ(RhB) = 0.55) and the singlet oxygen delivery efficiency for PDT applications.