Optical resolution photoacoustic microscopy (OR-PAM) is a hybrid imaging method for visualizing organelles due to the high spatial resolution and abundant optical contrast. Usually, OR-PAM employs high numerical aperture (NA) objectives and high-frequency ultrasonic detectors to resolve three-dimensional (3D) microstructures of cells. Expansion microscopy (ExM) provides a nanoscale resolution by isotropically enlarging cells instead of utilizing ultrahigh NA objectives. In this Letter, we report the development of photoacoustic expansion microscopy (PA-ExM) that combines the advantages of OR-PAM and ExM for 3D organelle imaging using near-infrared light. We evaluate the performance of PA-ExM using label-free melanoma cells, where the image quality of melanosome distributions in expanded cells using a 40× objective is comparable to that of unexpanded cells using an oil-immersed 100× objective. The results suggest that PA-ExM possesses the great potential to study organelles.
Keyphrases
- high resolution
- induced apoptosis
- single molecule
- label free
- cell cycle arrest
- high frequency
- high speed
- high throughput
- endoplasmic reticulum stress
- image quality
- computed tomography
- signaling pathway
- magnetic resonance
- magnetic resonance imaging
- oxidative stress
- cell proliferation
- atomic force microscopy
- single cell
- pi k akt
- photodynamic therapy
- monte carlo