Complete dissociation and reassembly behavior as studied by using poly(ethylene glycol)-block-poly(glutamate sodium) and kanamycin A.

Abstract

Kanamycin A, an amino modified sugar, can interact with poly(ethylene glycol)-block-poly(glutamate sodium) (PEG114-PGlu64) via electrostatic interactions (with PGlu) and hydrogen bonding (with PEG). The interplay of these two forces determines the assembly process and the resulting structure. In deionized water, kanamycin A and PEG114-PGlu64 form a spherical structure at [+]/[-] = 3.5. This structure dissociates instantly and completely in the presence of 30 mM NaCl. However, a new structure is reassembled in about 2 hours. A similar phenomenon is observed when the buffer pH is increased from 7.8 to 8.3. We attribute the distinct dissociation/reassembly process to the reestablishment of the balance between electrostatic interactions and hydrogen bonding. The dissociation/reassembly process in response to environmental changes offers a novel approach to release the loaded cargo in a controlled manner.