In vitro release of FITC-dextran from responsive microcapsules in different pH buffers.

P2VP pH-responsive microcapsules in a pH 6 (n = 4) environment showed no release of encapsulated FITC-dextran over 24 h as the pH was above the pKa of the microcapsules. At the lower pH of 3.8 (n = 4) around 80% of the encapsulated FITC-dextran was released within the first 5 mins, no further release was observed after this time. It is assumed that the unaccounted 20% is lost during the production of the microcapsules.