Monitoring reactive oxygen species (ROS) on the nanoscale - Combination of DNA origami and ceria nanoparticles

二氧化铈（CeO2）纳米颗粒因其催化和清除自由基的特性而引起了人们的特别关注。铈在两种氧化态（Ce3+和Ce4+离子）之间切换的能力促进了纳米颗粒表面的氧化还原反应或清除活性氧（ROS）并产生相对无害、反应性较低的产物。在铈中掺杂镧系离子，例如Eu3+离子，由于氧空位的增加，提高了其催化性能，为整体氧化还原活性的提高提供了更多的活性位点。该项目旨在确定/表征镧系掺杂的二氧化铈纳米颗粒对活性氧的保护潜力。研究中使用羟基自由基作为模型ROS和ssDNA附着在DNA折纸模板上，形成氧化铈纳米颗粒的锚点，氧化铈纳米颗粒被互补的ssDNA表面功能化。Eu3+掺杂的二氧化铈纳米颗粒将通过非水解溶胶-凝胶法合成，并将确定颗粒的表面性质，光谱性质和形态以及其他结构特征。为了实现生物相容性（以及对抗未来在体内使用的蛋白质冠的形成），纳米颗粒将被ssDNA功能化。羟基自由基将通过芬顿机制产生。将制作三角形DNA折纸模板，并用AFM对其进行结构表征。ssDNA功能化镧掺杂的二氧化铈将通过ssDNA连接体放置在DNA-origamis上。ssDNA链的长度将被用来改变氧化铈纳米粒子到DNA折纸的距离，随后在纳米尺度上定义羟基自由基的反应性可以被监测。我们将在纳米尺度上评估二氧化铈的活性氧清除性能，以建立距离活性关系，从而确定二氧化铈对ssDNA免受羟基自由基损伤的保护程度。这将根据放置在与氧化铈纳米颗粒不同距离上的ssDNA链（如果有的话）所观察到的损伤程度来评估。荧光测量将在活性氧材料生产前后进行，并将用于活性评估。羟基自由基产生后的AFM图像将被用来确定DNA连接器和DNA折纸上可能的“损伤”。

Ceria (CeO2) nanoparticles have attracted special interest because of their catalytic and free radical scavenging attributes. The ability of cerium to switch between two oxidation states (Ce3+ and Ce4+ ions) facilitates redox reactions at the nanoparticle surface or scavenging of reactive oxygen species (ROS) and producing relatively harmless, less reactive products. Doping lanthanide ions into ceria, e.g. Eu3+ ions, enhances its catalytic properties due to the increment of oxygen vacancies, providing more active sites for an overall increased redox activity. The project is aimed at determining/characterizing the protective potential of lanthanide doped ceria nanoparticles against ROS. Hydroxyl radicals as model ROS and ssDNA attached onto DNA origami templates to form an anchor for the ceria nanoparticles, which are surface-functionalized with complementary ssDNA, are used in the investigations. Eu3+-doped ceria nanoparticles will be synthesized by a non-hydrolytic sol-gel method and particle surface properties, spectroscopic properties and morphology, among other structural characteristics, will be determined. To achieve biocompatibility (and to combat the formation of protein corona for future use in body), the nanoparticles will be functionalized by ssDNA. Hydroxyl radicals will be generated by a Fenton mechanism. Triangular DNA origami templates will be fabricated and structurally characterized by AFM. ssDNA functionalized lanthanide-doped ceria will be placed onto the DNA-origamis via ssDNA linkers. The length of ssDNA strands will be used to modify the distance of the ceria nanoparticles to the DNA origami and subsequently a nm-scale is defined on which the reactivity of the hydroxyl radicals can be monitored. The ROS scavenging property of ceria will be evaluated on the nanoscale to develop a distance activity relationship, thereby determining the extent in which ceria can protect the ssDNA from hydroxyl radical damage. This will be assessed based on the level of damage observed on the ssDNA strands placed at various distances from the ceria nanoparticles, if any. Fluorescence measurements will be performed before and after the production of the ROS material and will be used in the assessment of the activity. AFM images after production of the hydroxyl radicals will be taken to determine the possible 'damage' on the DNA linkers and the DNA origami.