Engineering of an Enzyme-Activatable Ratiometric DNA Nanosensor for Spatially Resolved pH Imaging in Ischemic Stroke

Area of Science:

• Biomedical Engineering
• Molecular Imaging
• Nanotechnology

Background:

• Accurate imaging of intracellular pH is crucial for understanding ischemic stroke (IS) progression and identifying treatable tissue.
• Current methods for IS-specific pH sensing are limited, posing a challenge for effective stroke management.

Purpose of the Study:

• To engineer a novel apurinic/apyrimidinic endonuclease 1 (APE1)-activatable ratiometric DNA nanosensor (LPF) for IS-specific pH imaging.
• To enable spatially resolved monitoring of intracellular pH changes during ischemic stroke.

Main Methods:

• Developed a liposome-encapsulated dual-strand DNA probe (PF) with a pH-dependent i-motif and an APE1-cleavable site.
• Utilized Förster Resonance Energy Transfer (FRET) between Cy3 and Cy5 for ratiometric pH sensing.
• Validated nanosensor specificity and activation in oxygen-glucose-deprived (OGD) cells and in MCAO mouse models.

Main Results:

• The LPF nanosensor demonstrated pH-dependent activation triggered by APE1, which is upregulated in IS lesions.
• In vitro and in vivo studies confirmed the nanosensor's ability to specifically monitor pH changes in IS conditions.
• LPF successfully tracked dynamic pH gradients in MCAO mice, showing enzyme-mediated, IS-specific activation.

Conclusions:

• Established the first APE1-activated ratiometric nanosensor for precise pH imaging in ischemic stroke.
• The LPF nanosensor offers a promising platform for stroke diagnosis and the development of personalized interventions.