A Facile Cyclization Method Improves Peptide Serum Stability and Confers Intrinsic Fluorescence

Area of Science:

• Pharmaceutical sciences
• Bioconjugation chemistry
• Macromolecular drug development

Background:

• Peptides are increasingly used in pharmaceutics, requiring optimization for clinical application.
• Peptide cyclization enhances stability and affinity, while tagging is needed for trafficking studies.
• Fluorophore conjugation can negatively affect peptide properties like binding and permeability.

Purpose of the Study:

• To develop a single-step method for simultaneous peptide cyclization and intrinsic fluorescence.
• To evaluate the impact of this method on peptide stability, affinity, and utility in biodistribution studies.

Main Methods:

• Cysteine arylation of peptides using tetrafluoroterephthalonitrile (4F-2CN).
• Cyclization and fluorescence tagging in a single reaction step.
• Application to an M2 macrophage-targeting peptide.

Main Results:

• Achieved simultaneous cyclization and intrinsic fluorescence in one step.
• The resulting peptide exhibited improved serum stability and increased binding affinity.
• Demonstrated successful monitoring of biodistribution and cell internalization in a murine breast cancer model using intrinsic fluorescence.

Conclusions:

• Cysteine arylation with 4F-2CN offers a versatile strategy for peptide modification.
• This method provides stable, fluorescent peptides suitable for in vivo imaging and cellular studies.
• Eliminates the need for external fluorophore conjugation, preserving peptide functionality.