Methylene Blue: An FDA-Approved NIR-II Fluorogenic Probe with Extremely Low pH Responsibility for Hyperchlorhydria...

Area of Science:

• Biomedical Imaging
• Materials Science
• Chemical Engineering

Background:

• Methylene blue (MB) is an FDA-approved contrast agent.
• MB possesses a donor-acceptor (D-A) structure with nitrogen-heterocycles.
• Protonation of MB yields MBH, altering its optical properties.

Purpose of the Study:

• To investigate the photophysical properties of protonated Methylene blue (MBH).
• To explore the potential of MBH as a near-infrared (NIR) fluorescent probe.
• To demonstrate MBH's utility in imaging acidic environments.

Main Methods:

• Protonation of Methylene blue to form MBH.
• Spectroscopic analysis to determine fluorescence emission shifts.
• Evaluation of aggregation-induced emission (AIE) properties.
• In vitro or in vivo imaging of hyperacidemia models.

Main Results:

• Protonation red-shifted MB fluorescence from NIR-I to NIR-II (1000-1700 nm).
• MBH exhibited a conversion from Aggregation-Caused Quenching (ACQ) to Aggregation-Induced Emission (AIE).
• Successful demonstration of hyperacidemia imaging at pH < 1.

Conclusions:

• Protonated Methylene blue (MBH) is a promising NIR-II fluorescent probe.
• MBH's AIE characteristics enhance its imaging capabilities in acidic conditions.
• MBH offers a novel tool for diagnosing conditions associated with extreme acidity.