Centro Singular de Investigación en Química Biolóxica e Materiais Moleculares (CiQUS), Universidade de Santiago de Compostela, 15782, Santiago, Spain.
Grupo de Física de Coloides y Polímeros, Departamento de Física de Partículas, Universidade de Santiago de Compostela, 15782, Santiago, Spain.
J Nanobiotechnology. 2020 Jun 5;18(1):85. doi: 10.1186/s12951-020-00640-3.
The unique upconversion properties of rare-earth-doped nanoparticles offers exciting opportunities for biomedical applications, in which near-IR remote activation of biological processes is desired, including in vivo bioimaging, optogenetics, and light-based therapies. Tuning of upconversion in purposely designed core-shell nanoparticles gives access to biological windows in biological tissue. In recent years there have been several reports on NIR-excitable upconverting nanoparticles capable of working in biological mixtures and cellular settings. Unfortunately, most of these nanosystems are based on ytterbium's upconversion at 980 nm, concurrent with water's absorption within the first biological window. Thus, methods to produce robust upconverting nanoplatforms that can be efficiently excited with other than 980 nm NIR sources, such as 808 nm and 1064 nm, are required for biomedical applications.
Herein, we report a synthetic method to produce aqueous stable upconverting nanoparticles that can be activated with 808 nm excitation sources, thus avoiding unwanted heating processes due to water absorbance at 980 nm. Importantly, these nanoparticles, once transferred to an aqueous environment using an amphiphilic polymer, remain colloidally stable for long periods of time in relevant biological media, while keeping their photoluminescence properties. The selected polymer was covalently modified by click chemistry with two FDA-approved photosensitizers (Rose Bengal and Chlorin e6), which can be efficiently and simultaneously excited by the light emission of our upconverting nanoparticles. Thus, our polymer-functionalization strategy allows producing an 808 nm-activable photodynamic nanoplatform. These upconverting nanocomposites are preferentially stored in acidic lysosomal compartments, which does not negatively affect their performance as photodynamic agents. Upon 808 nm excitation, the production of reactive oxidative species (ROS) and their effect in mitochondrial integrity were demonstrated.
In summary, we have demonstrated the feasibility of using photosensitizer-polymer-modified upconverting nanoplatforms that can be activated by 808 nm light excitation sources for application in photodynamic therapy. Our nanoplatforms remain photoactive after internalization by living cells, allowing for 808 nm-activated ROS generation. The versatility of our polymer-stabilization strategy promises a straightforward access to other derivatizations (for instance, by integrating other photosensitizers or homing ligands), which could synergistically operate as multifunctional photodynamic platforms nanoreactors for in vivo applications.
稀土掺杂纳米粒子具有独特的上转换特性，为生物医学应用带来了令人兴奋的机会，其中包括希望在体内进行生物过程的近红外远程激活，包括体内生物成像、光遗传学和基于光的治疗。在特意设计的核壳纳米粒子中对上转换进行调谐，可以访问生物组织中的生物窗口。近年来，已经有几篇关于能够在生物混合物和细胞环境中工作的近红外激发上转换纳米粒子的报告。不幸的是，这些纳米系统中的大多数都是基于镱在 980nm 处的上转换，同时伴随着水在第一个生物窗口内的吸收。因此，需要开发能够用除 980nm 近红外光源（例如 808nm 和 1064nm）以外的光源高效激发的稳健上转换纳米平台的方法，以便在生物医学应用中使用。
本文报道了一种生产可被 808nm 激发源激活的上转换纳米粒子的合成方法，从而避免了由于水在 980nm 处的吸收而导致的不必要的加热过程。重要的是，这些纳米粒子使用两亲聚合物转移到水相环境中后，在相关的生物介质中长时间保持胶体稳定，同时保持其光致发光性能。选择的聚合物通过点击化学被两种 FDA 批准的光敏剂（孟加拉玫瑰红和氯乙酮 6）共价修饰，这两种光敏剂可以被我们的上转换纳米粒子的光发射高效且同时激发。因此，我们的聚合物功能化策略允许生产可被 808nm 激活的光动力纳米平台。这些上转换纳米复合材料优先储存在酸性溶酶体隔室中，这不会对其作为光动力剂的性能产生负面影响。在 808nm 激发下，证明了活性氧化物质（ROS）的产生及其对线粒体完整性的影响。
总之，我们已经证明了可以使用光敏剂-聚合物修饰的上转换纳米平台的可行性，该纳米平台可以被 808nm 光激发源激活，用于光动力治疗。我们的纳米平台在被活细胞内化后仍然具有光活性，允许生成 808nm 激活的 ROS。我们的聚合物稳定化策略的多功能性有望为其他衍生化（例如，通过整合其他光敏剂或归巢配体）提供直接途径，这些衍生化可以作为多功能光动力平台纳米反应器协同用于体内应用。
