Fast TIRF-SIM imaging of dynamic, low-fluorescent biological samples

Area of Science:

• Biophysics
• Cell Biology
• Optical Microscopy

Background:

• Fluorescence microscopy is crucial for studying live cells but faces trade-offs between spatial and temporal resolution.
• Limitations include photobleaching and imaging artifacts, particularly in structured illumination microscopy (SIM), hindering high-speed super-resolution imaging of low-fluorescent samples.

Purpose of the Study:

• To develop and characterize a Total Internal Reflection Fluorescence-Structured Illumination Microscopy (TIRF-SIM) system.
• To achieve high spatial (110 nm) and temporal (8 Hz) resolution for live-cell imaging.
• To provide a framework for optimizing SIM parameters and understanding image artifacts.

Main Methods:

• Implementation of a TIRF-SIM system using scan-mirrors and a Michelson interferometer.
• Optimization of illumination interference contrast for low-fluorescent, moving samples.
• Analysis of modulation contrast dependencies (laser coherence, polarization, beam displacement, sample movement).
• Characterization of signal-to-noise ratio and Wiener filtering effects on SIM image reconstruction.

Main Results:

• The developed TIRF-SIM system achieves 110 nm spatial resolution and up to 8 Hz temporal resolution.
• High resolution is maintained even for low-fluorescent and moving biological samples.
• A framework is provided to map and understand modulation contrast across the field of view.
• The influence of SNR and Wiener filtering on image quality and artifacts is characterized.

Conclusions:

• The TIRF-SIM system overcomes limitations of conventional SIM for live-cell super-resolution imaging.
• The provided guidelines and theoretical understanding aid microscopists in optimizing optical parameters.
• This facilitates more reliable measurements and analyses of dynamic biological processes using super-resolution microscopy.