Abstract :
[en] Among the emerging treatments for cancer, Photodynamic Therapy (PDT) is thought to be one of the most promising. PDT uses light sensitive molecules, or photosensitizer, to produce, under specific irradiation, toxic reactive oxygen species (ROS) to kill cancer cells. However, the amount of ROS generated is limited by both the fluorescence lifetime of the photosensitizer and its concentration around the cancer cells. Metal Enhanced Fluorescence (MEF), a phenomenon arising when a fluorophore is in closed proximity to a metallic structure such as metallic films or nanostructures, is seen as a way to solve these problems by reducing the fluorescence lifetime and increasing the fluorescence emission of the fluorophore. Protoporphyrin IX (PpIX) is a commonly used photosensitizer to treat skin cancers, which presents an intense absorption band around 400 nm while emitting around 630 nm. Because silver nanoparticles (Ag NPs) exhibit a strong Localized Surface Plasmon Resonance (LSPR) around 400 nm, MEF of the PpIX is expected when immobilized onto Ag NPs.
Here, we investigate the relevant parameters influencing the coupling effects between the LSPR in Ag NPs and PpIX attached onto the Ag NPs surface when the Ag NPs are dispersed in solution or electrostatically bound to a glass slide. In particular, we study the distance-dependent of MEF by applying multiple layers of polyelectrolyte to progressively increase the distance between Ag NPs and PpIX, covalently bond to the last polyelectrolyte layer as well as exploring the use of Ag NPs of different sizes ranging from 40 to 100 nm.
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