Detecting nitrile-containing small molecules by infrared photothermal microscopy.

Area of Science:

• Chemical Imaging
• Microscopy Techniques
• Biomedical Optics

Background:

• Infrared photothermal microscopy (IR-PTM) is an emerging technique for chemical substance imaging.
• Label-free imaging of specific molecules in biological samples remains a challenge.

Purpose of the Study:

• To demonstrate the utility of a nitrile group as a vibrational tag for IR-PTM.
• To evaluate the performance of IR-PTM for imaging target molecules in a low water-background environment within cells.

Main Methods:

• Utilized a nitrile group as a vibrational tag for IR-PTM.
• Performed IR photothermal imaging of trifluoromethoxy carbonyl cyanide phenylhydrazone (FCCP) in HeLa cells.
• Employed visible light as a probe beam for high spatial resolution photothermal detection.
• Compared IR-PTM with stimulated Raman scattering (SRS) microscopy for nitrile imaging.

Main Results:

• Successfully imaged FCCP within lipid droplets in HeLa cells using IR-PTM.
• Confirmed that the photothermal signal originated from the nitrile vibrational tag.
• Achieved high spatial resolution in photothermal imaging.
• IR-PTM demonstrated a signal-to-noise ratio (SNR) several tens of times better than SRS microscopy at equivalent power input.

Conclusions:

• Nitrile groups serve as effective vibrational tags for IR-PTM in biological samples.
• IR-PTM offers significant advantages in SNR over SRS microscopy for specific molecular imaging.
• This technique holds promise for advanced chemical imaging in cellular environments.