Easy route to functionalize iron oxide nanoparticles via long-term stable thiol groups

Area of Science:

• Nanotechnology
• Materials Science
• Bioconjugation Chemistry

Background:

• Superparamagnetic iron oxide nanoparticles (SPIOs) are crucial for biomedical applications.
• Direct functionalization of SPIOs with meso-2,3-dimercaptosuccinic acid (DMSA) is challenging due to thiol group instability.
• Stringent storage or chemical regeneration is typically required for DMSA-functionalized SPIOs.

Purpose of the Study:

• To develop a robust protocol for SPIO functionalization with DMSA.
• To enhance the stability of thiol groups on SPIOs under ambient conditions.
• To enable efficient conjugation of thiol-reactive molecules to SPIOs.

Main Methods:

• Poly(ethylene glycol) (PEG) grafting onto SPIOs.
• Anchoring of DMSA to PEG-grafted SPIOs.
• Assessment of thiol group stability using Ellman's assay.
• Conjugation of tetramethylrhodamine-5-maleimide (TMRM) to functionalized SPIOs.

Main Results:

• PEG grafting significantly increased the stability of DMSA thiol groups under ambient conditions.
• Thiol-functionalized SPIOs demonstrated stability at physiological pH and ionic strength.
• Successful grafting of the thiol-reactive fluorescent dye TMRM was achieved.

Conclusions:

• A novel PEG-based protocol overcomes the instability issues of DMSA functionalization on SPIOs.
• This method provides stable, functionalized SPIOs suitable for bioconjugation under standard laboratory conditions.
• The developed SPIOs are promising for various bioimaging and diagnostic applications.