Diffusion of guest molecules within sensitive core-shell microgel carriers.

The diffusion of payloads within core-shell carrier particles is of major relevance for drug-delivery applications. We use spatially resolved two-focus fluorescence correlation spectroscopy to quantify the diffusivity of different dextran molecules and colloids within carrier particles composed of a temperature-responsive poly(N-isopropylacrylamide) (PNIPAM) shell that surrounds a temperature-insensitive polyacrylamide core. The deswelling of the shell that occurs upon heating above the lower critical solution temperature of PNIPAM slightly slows down the diffusion of these tracer oligomers near the core-shell interface.

Spatially resolved tracer diffusion in complex responsive hydrogels.

Thermosensitive composite hydrogels that consist of a poly(acrylamide) hydrogel matrix with embedded micrometer-sized poly(N-isopropylacrylamide) microgel beads are promising models for complex, heterogeneous gels. We investigate the coupling of the microgel beads with the gel matrix and the formation of interpenetrating networks inside the microgels by confocal two-focus fluorescence correlation spectroscopy (2fFCS). This technique serves to study the effects of the heterogeneous structure of the composite hydrogels on the diffusive mobility of nanoscopic dextran tracers within the gels.

The role of the N-terminal domain in dimerization and nucleocytoplasmic shuttling of latent STAT3.

STAT3 is an important transcription factor involved in immunity and cancer. In response to cytokine stimulation, STAT3 becomes phosphorylated on a single tyrosine residue. Tyrosine-phosphorylated STAT3 accumulates in the nucleus, binds to specific DNA response elements and induces gene expression.