Silica-Based Hybrid Nano Assemblies Prepared by the LbL Technique with Combined Functionalities for Photothermal and Photodynamic Therapies

Photodynamic therapy (PDT) and photothermal therapy (PTT) rely on light to generate reactive oxygen species and heat. Both can be applied for cancer treatment and can be combined for an enhanced outcome. Here, we develop multifunctional colloidal composites based on the self-assembly of indocyanine green (ICG) and gold nanostars (AuNS) on top of silica (SiO₂) nanoparticles through the layer by layer (LbL) technique bringing combined photodynamic and photothermal properties to single particles. The ICG dye is a photosensitizer extensively used in PDT. AuNS with sizes of 30–60 nm show a tunable plasmon in the NIR, effective for PTT. Alternating layers of polyallylamine (PAH) and polystyrene sulfonate (PSS) have been first assembled on the surface of the SiO₂ nanoparticles. The ICG dye is loaded to the particles between the polyelectrolyte layers. AuNS are assembled electrostatically on top of the multilayers. The assembly of the polyelectrolyte layers on the SiO₂ surface and the coating with AuNS is traced by ζ-potential measurements and transmission electron microscopy (TEM) images. Singlet oxygen (¹O₂), hydrogen peroxide upon NIR irradiation and the efficiency of photothermal conversion are assessed for the hybrid colloids. Cell viability is measured to evaluate the cytotoxicity and phototoxicity of the nanoparticles.