New Microscope Reveals Tiny Cell Changes with Bidirectional Light

By combining two advanced imaging methods, Tokyo researchers have created a single microscope that captures more data with less disruption to living cells.

Study: Bidirectional quantitative scattering microscopy. Image Credit: Sadhin Costa/Shutterstock.com

Researchers at the University of Tokyo were able to detect signals across an intensity range that is 14x broader than that of conventional microscopes using their new device. The study was published in the journal Nature Communications.

They combined two traditional techniques that have previously been used only for either micro- or nanoscale observations.

Microscopes have been instrumental in advancing science since the 16th century. Their development has resulted not only in the development of more sensitive and precise equipment and analyses, but also in the creation of more specialized tools.

As a result, contemporary, state-of-the-art techniques have had to navigate a series of tradeoffs.

Quantitative phase microscopy (QPM) uses forward-scattered light and is capable of detecting structures at the microscale (over 100 nm) but not at smaller scales. This method has mainly been employed to capture static images of relatively intricate cellular structures.

Interferometric scattering (iSCAT) microscopy, however, uses back-scattered light to identify structures as small as individual proteins. 

iSCAT can be used to “track” single particles, providing insights into dynamic changes occurring within the cell, although it lacks the comprehensive perspective that QPM offers.

The observations were conducted without the use of any additional dyes in a label-free manner. Gentle on cells, the approach is suitable for long-term observations, presenting significant potential for testing and quality control applications within the pharmaceutical and biotechnology sectors.

I would like to understand dynamic processes inside living cells using non-invasive methods.

Kohki Horie, Study First Author, University of Tokyo

The research team embarked on an investigation to determine if the simultaneous measurement of light in both directions could mitigate the tradeoff and uncover a diverse array of sizes and motions from a single image.

To validate this concept and ensure that their newly constructed microscope was functioning as intended, the researchers aimed to observe the events occurring during cell death. The team captured one image that encoded information from both forward and backward-traveling light.

Our biggest challenge was cleanly separating two kinds of signals from a single image while keeping noise low and avoiding mixing between them.

Keiichiro Toda, Study First Author, University of Tokyo

The team was able to successfully quantify the movement of cellular structures at the microscale, and also that of nanoscale particles. 

By analyzing the light that was both forward and back-scattered, they were able to assess the size and refractive index of each particle, which is a characteristic that indicates the extent to which light is bent or scattered as it traverses through particles.

We plan to study even smaller particles, already thinking about future research, such as exosomes and viruses, and to estimate their size and refractive index in different samples. We also want to reveal how living cells move toward death by controlling their state and double-checking our results with other techniques.

Keiichiro Toda, Study First Author, University of Tokyo

Journal Reference:

Horie, K., et al. (2025) Bidirectional quantitative scattering microscopy. Nature Communications. DOI: 10.1038/s41467-025-65570-w.