Bipyramidal gold nanoparticles-assisted plasmonic photothermal therapy for ocular applications

Gold nanoparticles (AuNPs) play a key role in the field of nanomedicine due to their fascinating plasmonic properties as well as their great biocompatibility. An intriguing application is the use of plasmonic photothermal therapy (PPTT) mediated by anisotropic AuNPs irradiated with a near-infrared (NIR) laser for treating ocular diseases in ophthalmology. For this purpose, bipyramidal-shaped AuNPs (BipyAu), which were surface-functionalized with three different organic ligands (citrate, polystyrene sulphonate (PSS), and cetyltrimethylammonium bromide (CTAB)), were synthesized. The long-term storage stability was assured, in terms of minimal variation in aspect ratio and localized surface plasmon resonance. Better performance was achieved with BipyAu@citrate and BipyAu@PSS NPs. PPTT experiments mediated with the synthesized BipyAu NPs demonstrated that BipyAu@citrate provided the highest value of temperature increase (40 °C at 2.0 W cm^-2) after 15 min of 808 nm NIR laser irradiation. The potential future clinical application in ophthalmology was assessed by in vitro cytotoxicity analysis, confirming that BipyAu@citrate NPs were biocompatible for the three major corneal cell types. Furthermore, ex vivo analysis was performed by treating pig corneas with BipyAu@citrate NPs (0.18 μg Au) and subsequent NIR laser irradiation at 808 nm for 15 min, showing distortions in the collagen type I fibrils at the ultrastructural level and promoting the flattening of the corneal surface after treatment, without inducing cell cytotoxicity. This work suggests that a precise control of the fibril distortions can be provoked by PPTT mediated with BipyAu@citrate in the NIR region, paving the way for nanomedicine to correct common deficiencies in corneal diseases.