Label-free multiphoton microscopy promises real-time optical molecular imaging of live tissues

Nonlinear optical microscopy is a powerful biological imaging tool in the life sciences and for biomedical applications thanks to its unique capability to molecularly probe cellular and extracellular components in untreated unlabeled biological specimens, even in live animals and humans. A perspective paper by Boppart et al. presented a comprehensive discussion about several label-free nonlinear optical microscopy techniques and advocated a newly developed nonlinear imaging strategy called simultaneous label-free autofluorescence-multiharmonic (SLAM) microscopy, which can concurrently visualize a comprehensive set of bulk biomolecules in live cells and tissues in real time.

Novel ultrafast laser source engineering enables SLAM microscopy to realize label-free biological imaging with molecular specificity and provide comprehensive structural, functional/molecular and metabolic information for both cells and their tissues, expanding the application of molecular biological microscopy to real-world situations such as the intraoperative assessment of a tumor microenvironment.

According to the researchers, SLAM microscopy is a new implementation of multimodal multiphoton microscopy based on dual-fluorophore biosensing, emphasizing simultaneous label-free imaging of multiple biomolecules. The key technical part of the strategy is the combination of a novel laser source and an optimized excitation-detection condition for a broad variety of tissue types.

To image different types of bulk biomolecules at the same time and with lower risk of photodamage, authors Tu, Boppart and Chen advocated the transition of laser source engineering from the multi-shot strategy to the single-shot strategy. Thanks to the optimized excitation-detection condition, SLAM microscopy also seamlessly integrates live-tissue imaging and live-cell imaging. The open-top design of the imaging technique avoids plausible restriction to imaging geometry.

Due to its high compatibility with miniature biomedical imaging probes, SLAM microscopy will potentially enable fast, point-of-procedure and point-of-care diagnosis of diseases.

Source: “Simultaneous label-free autofluorescence-multiharmonic microscopy and beyond,” by Stephen A. Boppart, Sixian You, Lianhuang Li, Jianxin Chen, and Haohua Tu, APL Photonics (2019). The article can be accessed at https://doi.org/10.1063/1.5098349 .