Three-dimensional molecular imaging with photothermal optical coherence tomography.

Area of Science:

• Biomedical Optics
• Molecular Imaging
• Nanotechnology

Background:

• Optical Coherence Tomography (OCT) is a 3D imaging technique for high-resolution visualization of biological tissues.
• Current OCT methods can be enhanced with contrast agents for molecular-specific imaging.
• Photothermal OCT offers a promising avenue for sensitive molecular contrast in biological samples.

Purpose of the Study:

• To develop and validate a photothermal OCT method for sensitive molecular imaging.
• To demonstrate the capability of differentiating cells based on molecular targets.
• To assess the depth penetration and sensitivity of the photothermal OCT technique.

Main Methods:

• Utilized antibody-conjugated gold nanoparticles as contrast agents.
• Employed a pump laser at the nanoparticle resonance wavelength to induce heating.
• Detected refractive index changes using phase-sensitive OCT with lock-in detection.
• Applied the technique to three-dimensional cell constructs for molecular differentiation.

Main Results:

• Achieved high sensitivity of 14 parts per million (weight/weight) for nanoparticles.
• Successfully differentiated epidermal growth factor receptor (EGFR)-overexpressing cells from minimally expressing cells.
• Demonstrated potential for nondestructive 3D molecular imaging up to 2 mm deep in biological samples.

Conclusions:

• Photothermal OCT provides a sensitive, label-free method for molecular imaging in biological tissues.
• The technique enables differentiation of specific cell populations based on molecular markers.
• This approach holds significant potential for biomedical research and diagnostics.