New insights into the interaction of femtosecond lasers with living tissue

Nonlinear light microscopy has revolutionized our ability to observe and understand complex biological processes. However, light can also damage living matter. However, the mechanism behind the irreversible perturbation of cellular processes by intense light remains poorly understood.

To address this gap, the research groups of Hanieh Fattahi and Daniel Wehner at the Max Planck Institute for the Science of Light (MPL) and the Max-Planck-Zentrum für Physik und Medizin have joined forces to identify the conditions under which intense pulsed lasers can to be used in vivo without harming the organism.

The international team based in Erlangen used the vertebrate species zebrafish to delve into the mechanisms of deep tissue photodamage at a cellular level caused by femtosecond excitation pulses. The results are published in Physics of communications.

Soyeon Jun, first author of the publication and PhD student in the Femtosecond Fieldoscopy group at MPL led by Fattahi explains, “We demonstrated that damage to the central nervous system (CNS) of zebrafish, when irradiated by femtosecond pulses at 10³⁰ nm, suddenly occurs at the extreme maximum intensities required for low-density plasma formation.”

This allows a noninvasive increase of the image dwell time and photon flux during irradiation to 10³⁰ nm, as long as the peak intensity is below the low plasma density threshold. This is essential for label-free nonlinear microscopy.

“These findings contribute significantly to advances in deep tissue imaging techniques and innovative microscopy techniques, such as femtosecond fedoscopy, which is currently being developed in my group. This technique allows capturing images with high spatial resolution , without tags with attosecond time resolution,” says Fattahi.

“Our results not only highlight the value of collaborations between the fields of physics and biology, but also pave the way for in vivo applications to achieve precise light-based manipulations of the central nervous system,” adds Wehner, head of the research group. Neuroregeneration.