Synthesis of Pluronic-based silver nanoparticles/methylene blue nanohybrids: Influence of the metal shape on photophysical properties.

Nanotechnology development provides new strategies to improve different treatment modalities by integration of multiple molecules in a single multifunctional nanoparticle. In this scenario, we highlight silver nanoparticles (AgNPs) favorable optical properties such as absorption and emission of light in the visible region of the spectrum. This allows its synergic combination with the photosensitizer molecule methylene blue (MB) in order to improve outcomes in photodynamic-based therapies. Therefore, we engineered here a new multifunctional nanostructured system based in the synthesis of pluronic-based AgNP/MB nanohybrids inspired by the concept of supramolecular chemistry. Silver reduction in water and Pluronic F127 aqueous solutions in the presence of hydrogen peroxide as etching agent at several concentrations induced the formation of anisotropic forms of AgNPs. Electronic absorption and TEM studies demonstrated a greater kinetic and morphological control for Pluronic synthetized NPs. The smart design of the proposed nanohybrids favored the enhancement of MB photophysical properties such as fluorescence emission and singlet oxygen production due a synergic action from resonant coupling between AgNP magnetic field and MB molecules. Results also demonstrated that AgNP-MB distance modulation in Pluronic matrix is a relevant parameter in MB photophysical improvement. Finally, since AgNP absorbance spectrum is dependent on AgNP shape, it plays a critical role in the improvement of MB photophysical properties. These results show that the rational design in engineering new multifunctional nanoparticles is essential and point out that Pluronic AgNP/MB nanohybrids as a smart material for further developments aiming photodynamic-based therapies.