READ ME Experimental Dataset from Stabilizing gold nanoparticles for use in X-ray computed tomography imaging of soil systems

This investigation establishes a system of gold nanoparticles that show good colloidal stability as an X-ray computed tomography (XCT) contrast agent under soil conditions. Gold nanoparticles offer numerous beneficial traits for experiments in biology including: comparatively minimal phytotoxicity, X-ray attenuation of the material and the capacity for functionalization. However, soil salinity, acidity and surface charges can induce aggregation and destabilize gold nanoparticles, hence in biomedical applications polymer coatings are commonly applied to gold nanoparticles to enhance stability in the in vivo environment. Here we first demonstrate non-coated nanoparticles aggregate in soil-water solutions. We then show coating with a polyethylene glycol (PEG) layer prevents this aggregation. To demonstrate this, PEG-coated nanoparticles were drawn through flow columns containing soil and were shown to be stable; this is in contrast with control experiments using silica and alumina-packed columns. We further determined that a suspension of coated gold nanoparticles which fully saturated soil maintained stability over at least 5 days. Finally, we used time resolved XCT imaging and image based models to approximate nanoparticle diffusion as similar to that of other typical plant nutrients diffusing in water. Together, these results establish the PEGylated gold nanoparticles as potential contrast agents for XCT imaging in soil.本研究构建了一种金纳米颗粒体系，该体系在土壤环境下可作为X射线计算机断层扫描（X-ray computed tomography，XCT）造影剂，且具备优异的胶体稳定性。金纳米颗粒在生物学实验中具备诸多优势特性，包括相对较低的植物毒性、优异的X射线衰减能力以及可功能化修饰的特点。然而，土壤中的盐度、酸度以及表面电荷会诱导金纳米颗粒聚集并使其失稳，因此在生物医学应用中，通常会通过聚合物涂层对金纳米颗粒进行修饰，以提升其在活体环境中的稳定性。本研究首先证实，未涂层的金纳米颗粒会在土壤水溶液中发生聚集；随后证明，聚乙二醇（polyethylene glycol，PEG）涂层可有效阻止此类聚集行为。为验证这一点，研究团队将PEG修饰后的金纳米颗粒通过装填有土壤的流动柱，结果显示其仍保持稳定；而以二氧化硅和氧化铝装填的流动柱对照实验则呈现出相反结果。此外，研究团队还证实，完全浸润土壤的PEG修饰金纳米颗粒悬浮液至少可在5天内保持稳定。最后，本研究借助时间分辨XCT成像技术以及基于图像的模型，估算出金纳米颗粒的扩散行为与其他典型植物养分在水中的扩散行为相近。综上，上述实验结果证实，PEG化金纳米颗粒有望成为土壤环境中XCT成像的潜在造影剂。