Microstructural analysis of PLGA-PEG-PLGA copolymer based on NMR spectroscopy using model compounds

Area of Science:

• Polymer Chemistry
• Materials Science
• Biomaterials Engineering

Background:

• Poly(lactic-co-glycolic)-poly(ethylene glycol)-poly(lactic-co-glycolic) (PLGA-PEG-PLGA) triblock copolymers are crucial in drug delivery.
• Understanding their microstructure is essential for optimizing therapeutic efficacy.
• Current characterization methods may not fully capture complex copolymer structures.

Purpose of the Study:

• To introduce a novel strategy for detailed microstructure analysis of PLGA-PEG-PLGA triblock copolymers.
• To investigate the influence of organic catalysts on copolymer synthesis and structure.
• To establish a comprehensive characterization method for designing advanced drug delivery systems.

Main Methods:

• Synthesis of PLGA-PEG-PLGA triblock copolymers via Ring-Opening Polymerization (ROP) using organic catalysts.
• Utilized multidimensional Nuclear Magnetic Resonance (NMR) spectroscopy, including HSQC, HMBC, and Diffusion Ordered Spectroscopy (DOSY).
• Employed model copolymers (PLG-PEG-PLG, PLA-PEG-PLA) for enhanced structural elucidation and verified molecular weights against Gel Permeation Chromatography (GPC).

Main Results:

• NMR analysis revealed a strong correlation between catalyst type, monomer sequence arrangement, and average molecular weights.
• Identified Zn(acac)₂ and Fe(acac)₃ as effective catalysts with activity comparable to Sn(Oct)₂.
• Demonstrated the capability of the proposed NMR methodology to provide detailed insights into copolymer microstructure.

Conclusions:

• The novel NMR strategy offers a comprehensive approach to characterizing PLGA-PEG-PLGA triblock copolymers.
• Catalyst selection significantly impacts copolymer microstructure, influencing molecular weight and sequence.
• This methodology enables precise copolymer design, crucial for advancing drug delivery applications.