Preparation and unique pH-responsive properties of novel biodegradable nanocapsules composed of poly(gamma-glutamic acid) and chitosan as weak polyelectrolytes.

Novel biodegradable hollow nanocapsules composed of two kinds of weak polyelectrolytes, CT and gamma-PGA, were successfully prepared by the deposition of their LbL-assembled films onto silica particles and the subsequent removal of the silica. These CT-gamma-PGA hollow nanocapsules showed unique size increases at pH = 1.0, due to the swelling of capsule membranes induced by electrostatic repulsions between ammonium groups of CT components. On the other hand, no significant changes in the capsule size were observed at pH = 4.0, 7.0, and 10. By using the CT-gamma-PGA nanocapsules, the release of encapsulated substances in response to acidic pH values was accomplished.