pH-Sensitive Visible or Shortwave Infrared Quantum Dot Nanoprobes Using Conformation-Switchable Copolymeric Ligands

Area of Science:

• Biomedical Engineering
• Nanotechnology
• Optical Imaging

Background:

• Extracellular pH is crucial in physiological processes and diseases like cancer.
• Tumor micro-environments are typically more acidic than healthy tissues.
• In vivo mapping of tumor extracellular pH can advance our understanding of tumor physiology.

Purpose of the Study:

• To develop novel pH-sensitive quantum dot (QD) nanoprobes for in vivo imaging.
• To enable ratiometric detection of extracellular pH in the biological range.
• To create probes suitable for in vivo applications, including encapsulation in erythrocyte membranes.

Main Methods:

• Synthesized QD nanoprobes with conformation-switchable copolymer ligands and gold nanoparticle quenchers.
• Utilized pH-dependent changes in copolymer size to modulate QD fluorescence via energy transfer.
• Demonstrated ratiometric signal output for pH sensing in the visible and shortwave infrared (SWIR) ranges.
• Encapsulated functional probes within ghost erythrocyte membranes for enhanced in vivo applicability.

Main Results:

• Developed pH-sensitive nanoprobes exhibiting modulated fluorescence signals in response to decreasing pH (7.5 to 5.5-6).
• Achieved reversible shrinking of the copolymer ligand with pH changes, altering QD-gold nanoparticle energy transfer.
• Demonstrated the capability for ratiometric pH sensing using QD probes.
• Confirmed functionality of encapsulated probes within erythrocyte membranes for potential in vivo use.

Conclusions:

• The developed QD nanoprobes offer a novel approach for sensitive and ratiometric extracellular pH mapping.
• These probes are promising tools for in vivo imaging and understanding tumor micro-environment.
• Encapsulation in erythrocyte membranes enhances the in vivo applicability of these nanoprobes.