Point-Spread Function Deformations Unlock 3D Localization Microscopy on Spherical Nanoparticles

Area of Science:

• Nanotechnology
• Biophysics
• Microscopy

Background:

• Nanoparticles (NPs) are vital in biosensing, drug delivery, and photothermal therapy.
• Surface functionalization critically impacts NP performance.
• Conventional super-resolution microscopy struggles with NP-induced artifacts in fluorophore localization.

Purpose of the Study:

• To develop an accurate analytical point-spread function (PSF) model for fluorophores near spherical NPs.
• To overcome systematic mislocalizations caused by NPs in super-resolution imaging.
• To enable precise 3D localization of surface functional groups on NPs.

Main Methods:

• Derived an analytical PSF model for a fluorophore near a spherical NP.
• Achieved a four-orders-of-magnitude speedup compared to numerical methods.
• Applied the model to DNA-PAINT super-resolution microscopy data of DNA-coated gold NPs.

Main Results:

• Demonstrated <5 nm precision in extracting 3D positions of surface functional groups.
• Revealed inhomogeneous surface coverage on NPs.
• Validated the model's accuracy and speed for real-world applications.

Conclusions:

• The developed analytical PSF model accurately corrects for NP-induced artifacts in super-resolution microscopy.
• The method provides fast, precise, and accessible analysis of NP surface functionalization.
• This approach is poised to become a standard for imaging NPs in nanomedicine and biosensing.