Advantages and risks of multiphoton microscopy in physiology

Area of Science:

• Biophysics
• Live Cell Imaging
• Optical Microscopy

Background:

• Multiphoton microscopy (MPM) utilizes simultaneous absorption of two photons from a pulsed infrared laser.
• MPM offers inherent optical sectioning without a confocal aperture, enabling deep tissue penetration and reduced out-of-focus bleaching compared to confocal microscopy.
• Initially introduced as a superior alternative for live cell imaging, MPM aimed to minimize photodamage and enhance penetration depth.

Purpose of the Study:

• To evaluate the efficacy and limitations of multiphoton microscopy in live cell imaging.
• To compare MPM with single-photon and confocal microscopy regarding photodamage and photobleaching.
• To explore the potential of MPM for functional biological imaging applications.

Main Methods:

• Simultaneous absorption of two photons from a pulsed infrared laser source for excitation.
• Optical sectioning achieved through a highly confined focal volume.
• Comparative analysis of photodamage and photobleaching in focal and out-of-focus planes.
• Application in functional imaging, including the release of caged compounds.

Main Results:

• MPM provides deep penetration depth and reduces out-of-focus bleaching.
• Photodamage and photobleaching in the focal plane can be severe, potentially exceeding single-photon microscopy.
• Low excitation intensity and specific technical adaptations can effectively minimize photodamage.
• MPM is suitable for functional imaging, enabling precise compound release within a diffraction-limited volume.

Conclusions:

• Multiphoton microscopy is a powerful tool for deep tissue and live cell imaging, offering advantages in penetration and reduced out-of-focus effects.
• Careful optimization of excitation intensity and technical implementation is crucial to mitigate focal plane photodamage.
• MPM, when properly applied, serves as an excellent platform for advanced functional biological imaging techniques.