Fluorescence lifetime imaging by time-correlated single-photon counting.

Area of Science:

• Biophotonics and Imaging
• Fluorescence Spectroscopy
• Microscopy Techniques

Background:

• Time-resolved fluorescence imaging provides crucial information about molecular dynamics and environments.
• Existing methods often face limitations in efficiency, spectral resolution, or compatibility with standard microscopy setups.
• Accurate characterization of fluorescence decay and spectral properties is essential for applications like Förster Resonance Energy Transfer (FRET).

Purpose of the Study:

• To introduce a novel time-correlated single photon counting (TCPSC) technique for time-resolved multi-wavelength imaging.
• To enable efficient and high-resolution fluorescence decay and spectral data acquisition using laser scanning microscopes.
• To demonstrate the applicability of the technique for various biological and chemical samples.

Main Methods:

• Development of a four-dimensional histogramming process to record photon density across fluorescence decay time, x-y spatial coordinates, and wavelength.
• Integration with a laser scanning microscope and a pulsed excitation source.
• The method avoids time gating and wavelength scanning, maximizing photon counting efficiency.

Main Results:

• Achieved near-perfect photon counting efficiency, limited only by detector transit time spread.
• Demonstrated compatibility with various laser scanning microscopes (confocal and two-photon) and scanning rates.
• Successfully applied the technique to image samples stained with multiple dyes and to analyze CFP-YFP FRET.

Conclusions:

• The presented TCPSC technique offers a powerful and versatile tool for advanced time-resolved multi-wavelength fluorescence imaging.
• It significantly enhances data acquisition efficiency and spectral resolution compared to conventional methods.
• The technique is readily adaptable for diverse applications in biophysics, chemistry, and materials science.