Mid-infrared photothermal single-live-cell imaging beyond video rate

TL;DR

This paper introduces a high-speed, high-resolution mid-infrared photothermal imaging system capable of live-cell imaging beyond video rate, significantly advancing biomedical applications in aqueous environments.

Contribution

The authors develop a novel wide-field MIP microscope with enhanced signal-to-noise ratio and measurement speed, enabling real-time live-cell imaging in water-based samples.

Findings

Achieved imaging beyond video rate for live cells

Enhanced signal-to-noise ratio by two orders of magnitude

Demonstrated potential for single-live-cell analysis

Abstract

Advancement in mid-infrared (MIR) technology has led to promising biomedical applications of MIR spectroscopy, such as liquid biopsy or breath diagnosis. On the contrary, MIR microscopy has been rarely used for live biological samples in an aqueous environment due to the lack of spatial resolution and the large water absorption background. Recently, mid-infrared photothermal (MIP) imaging has proven to be applicable to 2D and 3D single-cell imaging with high spatial resolution inherited from visible light. However, the maximum measurement rate has been limited to several frames/s, limiting its range of use. Here, we develop a significantly-improved wide-field MIP quantitative phase microscope with two orders-of-magnitude higher signal-to-noise ratio than previous MIP imaging techniques and demonstrate single-live-cell imaging beyond video rate. We first derive optimal system design by numerically simulating thermal conduction following the photothermal effect. Then, we develop the designed system with a homemade nanosecond MIR optical parametric oscillator and a high full-well-capacity image sensor. Our high-speed and high-spatial-resolution MIR microscope has great potential to become a new tool for life science, in particular for single-live-cell analysis.