pH-responsive polymeric micelle based on PEG-poly(β-amino ester)/(amido amine) as intelligent vehicle for magnetic resonance imaging in detection of cerebral ischemic area

A series of pH-responsive polymeric micelles is developed to act as intelligent carriers to deliver iron oxide (Fe3O4) nanoparticles and respond rapidly to an acidic stimuli environment for magnetic resonance imaging (MRI). The polymeric micelle can be self-assembled at physiological pH by a block copolymer, consisting of a hydrophilic methoxy poly(ethylene glycol) (PEG) and a pH-responsive poly(β-amino ester)/(amido amine) block. Consequently, the Fe3O4 nanoparticles can be well encapsulated into polymeric micelles due to the hydrophobic interaction, shielded by a PEG coronal shell. In an acidic environment, however, the pH-responsive component, which has ionizable tert-amino groups on its backbone, can become protonated to be soluble and release the hydrophobic Fe3O4 nanoparticles. The Fe3O4-loaded polymeric micelle was measured by dynamic light scattering (DLS), superconducting quantum interference device (SQUID) and a 3.0 T MRI scanner. To assess the ability of this MRI probe as a pH-triggered agent, we utilize a disease rat model of cerebral ischemia that produces acidic tissue due to its pathologic condition. We found gradual accumulation of Fe3O4 nanoparticles in the brain ischemic area, indicating that the pH-triggered MRI probe may be effective for targeting the acidic environment and diagnostic imaging of pathologic tissue.

Graphical AbstractA Fe3O4-encapsulated pH-responsive polymeric micelle methoxy poly(ethylene glycol)-poly(β-amino ester)/(amido amine) was acted as an acid-triggered MRI contrast agent. This MRI probe remains a micellar state at pH 7.4 whereas it can be dissolved, releasing Fe3O4 in acidic cerebral ischemic area.Figure optionsDownload full-size imageDownload as PowerPoint slide