Label-free superior contrast with c-band ultra-violet extinction microscopy.

Area of Science:

• Biophysics
• Optical Microscopy
• Cell Biology

Background:

• Biological cells are often transparent at visible wavelengths, limiting contrast in traditional microscopy.
• The refractive index of cells influences light phase and intensity, but absorption (extinction coefficient k) is minimal in visible light.
• Label-free imaging methods aim to visualize cellular structures without exogenous labels.

Purpose of the Study:

• To explore the use of c-band ultraviolet (UVC) light for high-contrast, high-resolution, label-free microscopy.
• To demonstrate the advantages of UVC light over visible wavelengths for imaging cellular details.
• To utilize autofluorescence as an additional imaging modality in the same setup.

Main Methods:

• Utilized differential phase contrast illumination with UVC light.
• Applied associated image processing techniques for contrast enhancement.
• Quantified extinction coefficient distribution in liver sinusoidal endothelial cells.
• Achieved nanoscale resolution for imaging subcellular structures.

Main Results:

• Achieved a 7- to 300-fold improvement in contrast compared to visible-wavelength and UVA microscopy techniques.
• Obtained a resolution down to 215 nm, enabling imaging of individual fenestrations in sieve plates.
• Successfully quantified the extinction coefficient distribution within liver sinusoidal endothelial cells.
• Demonstrated the capability to use intrinsic autofluorescence as an independent imaging modality.

Conclusions:

• UVC light microscopy offers a powerful label-free approach for high-contrast and high-resolution imaging of biological samples.
• This method allows visualization of fine cellular structures, such as fenestrations, without the need for electron or super-resolution fluorescence microscopy.
• The combined capability of UVC phase contrast and autofluorescence imaging provides a versatile tool for cell biology research.