Unlocking Multimodal Nonlinear Microscopy for Deep-Tissue Imaging under Continuous-Wave Excitation with Tunable...

Area of Science:

• Biomedical Optics
• Materials Science
• Nanotechnology

Background:

• Nonlinear microscopy offers superior 3D imaging but is hindered by costly ultrafast pulsed lasers.
• Upconverting nanoparticles (UCNPs) present an alternative, exhibiting nonlinear optical properties under simpler excitation.
• Rare-earth doped nanocrystals, like Yb³⁺/Tm³⁺ co-doped NaYF₄, are promising for multimodal nonlinear imaging.

Purpose of the Study:

• To demonstrate the use of UCNPs for multimodal nonlinear microscopy with continuous-wave (CW) excitation.
• To achieve high-resolution, in vivo 3D imaging of deep cerebrovascular networks.
• To explore UCNP applications beyond imaging, such as targeted photomodulation.

Main Methods:

• Utilized Yb³⁺/Tm³⁺ co-doped NaYF₄ nanocrystals as UCNPs for nonlinear optical responses.
• Employed a simple optical setup with CW laser excitation.
• Performed in vivo 3D imaging of mouse cerebrovascular networks and visualization of blood flow dynamics.

Main Results:

• Achieved high-resolution in vivo 3D imaging of mouse cerebrovascular networks up to 800 µm depth.
• Demonstrated multimodal nonlinear emissions (UV, blue, NIR) from UCNPs under CW excitation.
• Visualized in vivo cerebrovascular flow dynamics with video-rate imaging and achieved depth-selective photomodulation.

Conclusions:

• UCNPs provide a cost-effective alternative to pulsed lasers for advanced nonlinear microscopy.
• This approach significantly enhances deep brain imaging capabilities and overcomes current limitations.
• Opens new avenues for bio-imaging, optogenetics, and photodynamic therapy using CW lasers.