Superresolution Microscopy of the Volume Phase Transition of pNIPAM Microgels

TL;DR

This paper demonstrates the use of superresolution microscopy, specifically dSTORM, to visualize the internal microstructure of pNIPAM microgels during their volume phase transition with nanometer resolution.

Contribution

It provides the first in-situ superresolution imaging of individual microgel particles, revealing their internal structure during swelling and collapse.

Findings

Achieved 30nm lateral and 60nm axial resolution with dSTORM.

Visualized internal microstructure changes during phase transition.

Enabled nanoscopic observation of microgel behavior in situ.

Abstract

Hierarchical polymer structures such as pNIPAM microgels have been extensively studied for their ability to undergo significant structural and physical transformations that can be controlled by external stimuli such as temperature, pH or solvent composition. However, direct three-dimensional visualization of individual particles in situ have so far been hindered by insufficient resolution, with optical microscopy, or contrast, with electron microscopy. In recent years superresolution microscopy techniques have emerged that in principle can provide nanoscopic optical resolution. Here we report on the in-situ superresolution microscopy of dye-labeled submicron sized pNIPAM microgels revealing the internal microstructure during swelling and collapse of individual particles. Using direct STochastic Optical Reconstruction Microscopy (dSTORM) we demonstrate a lateral optical resolution of 30nm and an axial resolution of 60nm.