Advances in label-free dynamic imaging of live cells using fourier ptychographic microscopy

High-resolution and long-term dynamic imaging are essential for visualizing the spatial distribution and interaction networks of organelles within living cells. Although traditional super-resolution fluorescence microscopy achieves impressive resolutions of 20-100 nm, it faces significant challenges, including phototoxicity, photobleaching, and limited suitability for prolonged live-cell observation. These issues have driven the development of label-free imaging technologies that aim to minimize disruption to cellular physiology while providing high-resolution, non-destructive imaging. Among label-free approaches, Quantitative Phase Imaging (QPI) has emerged as a promising alternative for live-cell research by reconstructing cellular structures based on phase changes in transmitted light. In particular, Fourier ptychographic microscopy (FPM) achieves resolutions as fine as 150 nm while maintaining a large field of view, making it highly suitable for high-resolution, label-free imaging. Since its introduction in 2013, FPM has rapidly advanced, offering computational imaging capabilities that surpass conventional resolution limits. However, current systems are constrained by slow imaging speeds due to the sequential illumination of hundreds of LEDs. Here, we review the collective advancements in FPM that have transformed its capabilities over recent years. While numerous research groups have contributed to this progress, key innovations include the development of two-dimensional super-resolution FPM techniques that overcome the diffraction limit through iterative pattern optimization. Building upon these efforts, our group has introduced three-dimensional fast high-resolution Fourier microscopy, achieving 3D dynamic imaging at sub-micron resolution through computational refocusing algorithms. Collectively, these advancements establish FPM as a groundbreaking tool for real-time, high-resolution imaging of living cells, facilitating comprehensive analysis of organelle interactions and providing valuable insights into cellular functions and disease mechanisms.