In biomedical imaging, nanoparticles combined with radionuclides that generate Cerenkov luminescence are used in diagnostic imaging, photon-induced therapies and as activatable probes. In these applications, the nanoparticle is often viewed as a carrier inert to ionizing radiation from the radionuclide. However, certain phenomena such as enhanced nanoparticle luminescence and generation of reactive oxygen species cannot be completely explained by Cerenkov luminescence interactions with nanoparticles. Herein, we report methods to examine the mechanisms of nanoparticle excitation by radionuclides, including interactions with Cerenkov luminescence, β particles and γ radiation. We demonstrate that β-scintillation contributes appreciably to excitation and reactivity in certain nanoparticle systems, and that excitation by radionuclides of nanoparticles composed of large atomic number atoms generates X-rays, enabling multiplexed imaging through single photon emission computed tomography. These findings demonstrate practical optical imaging and therapy using radionuclides with emission energies below the Cerenkov threshold, thereby expanding the list of applicable radionuclides.

在生物医学成像中，纳米粒子与产生切伦科夫发光的放射性核素结合在一起被用于诊断成像，光子诱导疗法和可激活探针。在这些应用中，纳米粒子通常被视为对放射性核素电离辐射呈惰性的载体。但是，某些现象，例如增强的纳米粒子发光和活性氧物种的产生，不能通过与纳米粒子的切伦科夫发光相互作用来完全解释。本文中，我们报告了一些方法来检查放射性核素激发纳米粒子的机理，包括与切伦科夫发光，β粒子和γ辐射的相互作用。我们证明了β-闪烁法在某些纳米粒子系统中显着地促进了激发和反应性，并且由大原子序数原子组成的纳米粒子的放射性核素激发产生X射线，从而能够通过单光子发射计算机断层摄影进行多重成像。这些发现证明了使用发射能量低于切伦科夫阈值的放射性核素进行的实用光学成像和治疗，从而扩大了适用的放射性核素的范围。