Intrinsic Green Fluorescent Cross-Linked Poly(ester amide)s by Spontaneous Zwitterionic Copolymerization

Area of Science:

• Polymer Chemistry
• Materials Science
• Biomaterials

Background:

• Spontaneous zwitterionic copolymerization (SZWIP) of 2-oxazolines and acrylic acid yields biocompatible but low molecular weight linear N-acylated poly(amino ester)s (NPAEs).
• Existing methods limit the molecular weight and cross-linking capabilities of NPAEs.

Purpose of the Study:

• To develop a facile one-step approach for preparing higher molar mass, cross-linked NPAEs.
• To investigate the potential for fluorescence in these novel cross-linked polymers.
• To explore their application as fluorescent bioimaging agents.

Main Methods:

• Utilized 2,2'-bis(2-oxazoline)s (BOx) with varying n-alkyl bridging units for cross-linking.
• Investigated solvent-free, solution phase, and oil-in-oil emulsion polymerization techniques.
• Characterized the resulting polymers for fluorescence, pH-responsiveness, photostability, and cytocompatibility.

Main Results:

• Achieved higher molar mass, cross-linked NPAEs via a one-step process.
• Discovered inherent green fluorescence in butylene-bridged BOx-derived polymers, termed polymerization-induced emission.
• Developed solution-processable and water-dispersible fluorescent NPAEs.
• Demonstrated pH-responsive emission intensity and excellent photostability.
• Confirmed cytocompatibility and utility as in vitro fluorescent bioimaging agents.

Conclusions:

• A novel, facile method for synthesizing fluorescent, cross-linked NPAEs was established.
• The discovered polymerization-induced emission offers a new class of intrinsically luminescent polymers.
• These biocompatible, fluorescent polymers show significant promise for advanced bioimaging applications.