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Updated: Jan 8, 2026
09:09
A Label-free Technique for the Spatio-temporal Imaging of Single Cell Secretions
Published on: November 23, 2015
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Ultrasensitive bright-field microscope enables label-free single-protein detection.
Optics Letters
|December 15, 2025
Summary
Coherent brightfield (COBRI) microscopy enables label-free visualization of single proteins. This advanced technique achieves exceptional sensitivity for detecting molecular binding events without any labels.
Area of Science:
- Biophysics
- Optical Microscopy
- Molecular Imaging
Background:
- Label-free imaging is crucial for studying biomolecular interactions.
- Traditional bright-field microscopy lacks the sensitivity for single-molecule detection.
- Advancements in optical configurations are needed to enhance microscopy sensitivity.
Purpose of the Study:
- To develop a highly sensitive bright-field microscopy technique for label-free single-molecule detection.
- To demonstrate the capability of coherent bright-field (COBRI) microscopy for visualizing individual proteins.
- To establish quantitative detection of single proteins using optical contrast.
Main Methods:
- Implementation of coherent bright-field (COBRI) microscopy.
- Tailored control of illumination coherence, intensity, and interference contrast.
- Direct visualization of single protein binding events on coverslips.
Main Results:
- COBRI microscopy achieved sensitivity for direct visualization of single proteins without labels.
- Individual protein binding events were resolved for molecular masses from 150 to 915 kDa.
- Optical contrast of single proteins scaled linearly with molecular polarizability and mass, enabling quantitative detection.
Conclusions:
- COBRI microscopy is a powerful and accessible platform for label-free single-molecule imaging.
- The study affirms the interferometric potential of bright-field optics for biomolecular detection.
- This technique extends the utility of bright-field microscopy to the detection of individual biomolecules.
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