Polymeric expansile nanoparticles (eNPs) that respond to a mildly acidic environment by swelling with water and expanding 2–10× in diameter represent a new responsive drug delivery system. Here, we use a variety of techniques to characterize the pH- and time-dependence of eNP swelling as this is a key property responsible for the observed in vitro and in vivo performance of eNPs. Results demonstrate a significant change in eNP volume (>350×) at pH 5.0 as seen using: scanning electron microscopy (SEM), conventional transmission electron microscopy (TEM), freeze-fracture transmission electron microscopy (ff-TEM), fluorescence microscopy, and a new nanopore based characterization technology, the qNano, which measures both individual particle size as well as overall particle concentration in situ using tunable resistive pulse sensing. eNP swelling occurs in a continuous and yet heterogeneous manner over several days and is pH dependent.
Colby, Aaron H., Yolonda L. Colson, and Mark W. Grinstaff. "Microscopy and tunable resistive pulse sensing characterization of the swelling of pH-responsive, polymeric expansile nanoparticles." Nanoscale 5, no. 8 (2013): 3496-3504.
View full article