Visualization and analysis of superparamagnetic iron oxide nanoparticles in the inner ear by light microscopy and energy filtered TEM

Nanoparticles as potential carriers for local drug transfer are an alternative to systemic drug delivery into the inner ear. We report on the first in vitro tests of a new ferrogel consisting of superparamagnetic iron oxide nanoparticles (SPIONs) and a Pluronic® F127 (PF127) copolymer. Pluronic copolymers possess a unique viscosity-adjustable property that makes PF127 gels easy to handle compared to conventional cross-linked hydrogels. This ferrogel was successfully tested in cadaver human temporal bones as well as in organotypic explant cultures of mouse inner ears. SPIONs were identified by light microscopy and localized with different imaging modes in energy-filtered transmission electron microscopy. Our approach shows a promising possibility to use iron oxide nanoparticles, which are suitable for visualization and characterization at both the light- and electron-microscopic levels.From the Clinical EditorThe authors report the first in vitro tests of a new ferrogel consisting of superparamagnetic iron oxide nanoparticles (SPIONs) and a Pluronic® F127 (PF127) copolymer for drug delivery in the inner ear, demonstrasting a promising possibility to use iron oxide nanoparticles, which are suitable for visualization and characterization at both the light- and electron-microscopic levels.

Graphical AbstractFigure optionsDownload high-quality image (209 K)Download as PowerPoint slideThe image represents the introduction of SPIONs at the round window membrane of the human temporal bone and to the mouse organotypic explant culture. The SPIONs are incorporated with pluronic PF 127, which could be used to carry drugs to deliver at the cells of the inner ear for future applications. The image also explains the uptake and the distribution of SPIONs in the inner ear. The iron oxide nanoparticles are detected by Berlin blue and EFTEM methods. Our strategy represents a potential possibility to use newly developed SPIONs for light and electron microscopical visualization and characterization.