Lay Alice, Sheppard Olivia H, Siefe Chris, McLellan Claire A, Mehlenbacher Randy D, Fischer Stefan, Goodman Miriam B, Dionne Jennifer A
Department of Applied Physics, Stanford University, Stanford, California 94305, United States.
Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, United States.
ACS Cent Sci. 2019 Jul 24;5(7):1211-1222. doi: 10.1021/acscentsci.9b00300. Epub 2019 Jul 9.
Upconverting nanoparticles (UCNPs) are promising tools for background-free imaging and sensing. However, their usefulness for applications depends on their biocompatibility, which we define by their optical performance in biological environments and their toxicity in living organisms. For UCNPs with a ratiometric color response to mechanical stress, consistent emission intensity and color are desired for the particles under nonmechanical stimuli. Here, we test the biocompatibility and mechanosensitivity of α-NaYF:Yb,Er@NaLuF nanoparticles. First, we ligand-strip these particles to render them dispersible in aqueous media. Then, we characterize their mechanosensitivity (∼30% in the red-to-green spectral ratio per GPa), which is nearly 3-fold greater than those coated in oleic acid. We next design a suite of and tests to investigate their structural and optical properties under several biorelevant conditions: over time in various buffers types, as a function of pH, and along the digestive tract of worms. Finally, to ensure that the particles do not perturb biological function in , we assess the chronic toxicity of nanoparticle ingestion using a reproductive brood assay. In these ways, we determine that mechanosensitive UCNPs are biocompatible, i.e., optically robust and nontoxic, for use as sensors to study animal digestion.
上转换纳米粒子（UCNPs）是用于无背景成像和传感的有前景的工具。然而，它们在应用中的实用性取决于其生物相容性，我们通过其在生物环境中的光学性能和在活生物体中的毒性来定义生物相容性。对于对机械应力具有比率颜色响应的UCNPs，在非机械刺激下，粒子需要一致的发射强度和颜色。在这里，我们测试了α-NaYF:Yb,Er@NaLuF纳米粒子的生物相容性和机械敏感性。首先，我们对这些粒子进行配体剥离，使其可分散在水性介质中。然后，我们表征了它们的机械敏感性（每吉帕红到绿光谱比率约为30%），这比涂有油酸的粒子的机械敏感性高出近3倍。接下来，我们设计了一系列测试，以研究它们在几种生物相关条件下的结构和光学性质：在不同缓冲液类型中随时间变化、作为pH的函数以及在蠕虫消化道中的情况。最后，为确保粒子不会干扰线虫的生物学功能，我们使用繁殖亲代测定法评估纳米粒子摄入的慢性毒性。通过这些方式，我们确定机械敏感的UCNPs作为研究动物消化的传感器是生物相容的，即光学稳定且无毒。
