Correlative cellular ptychography with functionalized nanoparticles at the Fe L-edge

Area of Science:

• Cell biology
• Nanotechnology
• Microscopy

Background:

• Precise nanoparticle localization is vital for understanding cell-particle interactions.
• Applications in nanomedicine require detailed knowledge of nanoparticle behavior within cells.

Purpose of the Study:

• To demonstrate a proof-of-principle for imaging individual functionalized nanoparticles within mammalian cells.
• To establish a correlative microscopy approach for high-resolution 3D localization.

Main Methods:

• Utilized a graphene-oxide substrate to minimize background scattering.
• Employed fluorescence microscopy for initial identification of cellular features.
• Applied scanning transmission X-ray tomography for 3D particle localization.
• Used ptychographic coherent diffractive imaging for high-resolution analysis of fine features.

Main Results:

• Achieved sensitive detection of fluorescent core-shell nanoparticles (22nm Fe3O4 core, 25nm SiO2 shell) using Fe L-edge X-ray energy tuning.
• Confirmed internalization of a subset of nanoparticles within HeLa cells.
• Obtained high-contrast ptychographic images revealing two oxidation states of individual nanoparticles.
• Demonstrated a resolution of approximately 16.5 nm.

Conclusions:

• The developed correlative microscopy technique enables precise localization of individual fluorescent nanoparticles within mammalian cells.
• This capability will enhance understanding of structure/function relationships for functionalized nanoparticles in nanomedicine.