Figure 1.

Photoacoustic and magnetic resonance (MR) imaging of hybrid manganese dioxide-coated ultra-small NaGdF4 nanoparticles for spatiotemporal modulation of hypoxia in head and neck cancer. (A) usNP-MnO₂ composed of NaYF₄:Nd³⁺/NaGdF₄ nanocrystals coated with manganese dioxide were designed and synthesized for evaluation. (B) The hybrid nanoparticles have the potential to modulate tumor oxygenation by generating oxygen in the presence of reactive oxygen species (H₂O₂) within the tumor microenvironment. Areas of hypoxia (blue regions) within the tumor microenvironment are known to have lower pH and accumulation of reductive species such as H₂O₂. Under these conditions, usNP-MnO₂ will accumulate and undergo a redox reaction to release O₂ and free usNP, increasing pO₂ detectable by PAI and allowing for MRI detection of usNP. (C) Photoacoustic and MR imaging was performed to assess the imaging properties and the ability of usNP-MnO₂ to modulate hypoxia in vitro, using vascular channel phantoms, and in vivo, using patient derived xenograft models of head and neck squamous cell carcinoma (HNSCC).