Tracking the motion of single nanoparticles inside living cells: New insights into intracellular crowdedness

生物分子如何在空间和时间上在活细胞内运动，不仅是一个基本的研究问题，而且是理解许多生物过程的关键。随着先进的单粒子跟踪技术的发展，细胞内的生物分子表现出复杂的运动类型，不能简单地描述为热扩散的随机运动或分子马达的定向运动。这是因为细胞含有一个充满大分子和细胞器的细胞质，以及一个由细胞骨架蛋白细丝组成的异质网络。深入了解活细胞内生物分子运动的关键是开发能够以高定位精度和速度在3D中跟踪单个粒子的新技术，以及可以根据物理定律描述实验的数学模型，并最终揭示对高度复杂的活细胞内部的新见解。在这个项目中，您将应用一种先进的激光微光谱学技术，称为共振四波混合，由监督团队首创，以纳米级的3D精度对细胞内的单个小金纳米颗粒进行成像和跟踪。纳米粒子将被微注射到卵子（卵母细胞）中。这些是监督小组积极研究的大细胞（来自哺乳动物和无脊椎动物）。它们的ATP水平和代谢率与它们的成熟、受精和进一步发育成优质胚胎的能力密切相关。值得注意的是，由atp驱动的分子马达可以影响粒子的运动。因此，对这些细胞内运动的研究将为监测胚胎代谢和预测生存能力的新技术提供一个平台。实验单粒子轨迹将在不同代谢条件下的鸡蛋中测量，并将与扩散的数学模型进行比较，这反映了监督团队在数学和计算方法方面的专业知识。测量的时间轨迹将揭示与拥挤环境相关的随机、定向、瞬时停滞和受限运动的组合。其目的将是发展环境的纳米结构和粒子运动之间的因果关系。反过来，这将刺激假设得到实验验证，并将提供一个前所未有的洞察细胞的内部。

How biomolecules move inside living cells, in space and time, is not only a fundamental research question but is key to the understanding of many biological processes. With the development of advanced single-particle tracking techniques, it has become apparent that biomolecules inside cells exhibit complicated types of motion, which cannot be simply described as random from thermal diffusion or directed motion via molecular motors. This is because the cell contains a cytoplasm crowded with large biomolecules and organelles, and a heterogeneous network of cytoskeletal protein filaments.Key to the in depth understanding of biomolecular motion inside living cells is the development of new techniques capable to track single particles in 3D with high localisation precision and speed, alongside mathematical models that can describe the experiments according to physics' law, and eventually reveal new insights into the highly complex living cell's interior.In this project, you will apply an advanced laser micro-spectroscopy technique called resonant Four-Wave Mixing, pioneered by the supervisory team, to image and track single small gold nanoparticles background free inside cells with precision at the nanoscale in 3D. Nanoparticles will be micro-injected into eggs (oocytes). These are large cells actively studied by the supervisory team (from mammals and invertebrates). They have ATP levels and metabolic rates closely linked to their ability to mature, be fertilised, and further develop into good quality embryos. Notably, movement of particles can be influenced by molecular motors that are ATP-driven. Hence, studies of intracellular motion in these cells will be a platform for new technologies to monitor embryo metabolism and predict viability.Experimental single particle trajectories will be measured in eggs under different metabolic conditions, and will be compared with mathematical models of diffusion, reflecting expertise in mathematical and computational methods by the supervisory team. Measured time trajectories will reveal combinations of random, directed, transiently stalled and constrained motions related to crowded environments. The aim will be to develop a causal link between the nanostructure of the environment and particle motion. This in turn will stimulate hypothesis to be verified experimentally, and will provide an unprecedented insight on the cell's interior.