Identifying high performance photosensitizer with simultaneous enhancement in fluorescence and singlet oxygen generation, from ‘(Ag/Au)-aggregation-induced emission-active fluorogen’ theranostic nanoparticles

Photodynamic therapy (PDT) is a non-invasive medical technique that combines photosensitizer (PS) molecules and light for cancer treatment. Driven by the need for more personalized medicine, shortened irradiation time and treatment efficiency of PDT are required. Herein, a library of novel theranostic nanoparticle systems for personalized medicine in PDT of cancer is reported. Ag and Au nanoparticles in a size range of 40–50 nm are prepared and used subsequently to synthesize core-shell plasmonic nanoparticles with various thicknesses, either with silica or polymer spacer. Metal-enhanced fluorescence and singlet oxygen generation (SOG) studies are performed for a naphthalene-linked pyridine-based neutral triarylethene as AIE-active PS molecule, by adsorbing on the Ag and Au core-shell nanoparticles. The factors that are varied during the study are the composition of the spacer, and the spacer length. Notably, the enhancement in fluorescence and SOG of the adsorbed AIEgen are observed at the same distance from the metallic surface, resulting from short-range near field plasmonic effect for all the theranostic PS prepared with Ag/Au. The best result, 7.9 fold enhancement in fluorescence and 10.4-fold enhancement in SOG, is observed on loading AIEgen on ∼42 nm Au nanoparticles with polymer spacer, showing promising advancement for image-guided PDT. The probable reasons behind the observed outcomes, are analyzed and discussed in detail, with the help of the Jablonski diagram of the PS molecule. The obtained results from the study has the potential to replace or support the conventional radiation therapy and chemotherapy with serious adverse effects.