Microphase separation in bioerodible copolymers for drug delivery

Area of Science:

• Polymer Science
• Materials Science
• Biomedical Engineering

Background:

• Bioerodible polyanhydrides are crucial for controlled drug delivery.
• Understanding copolymer microstructure is key to designing effective drug delivery devices.
• Poly(1,6-bis-p-carboxyphenoxyhexane-co-sebacic anhydride) (CPH : SA) is a promising material for these applications.

Purpose of the Study:

• To investigate the relationship between copolymer composition and microstructure in CPH : SA.
• To determine if micro-phase separation occurs in CPH : SA copolymers.
• To understand how micro-phase separation and drug properties affect drug partitioning and delivery.

Main Methods:

• Differential scanning calorimetry (DSC) to analyze thermal properties.
• Wide-angle X-ray diffraction (WAXD) to assess the degree of crystallinity.
• Atomic force microscopy (AFM) for surface microstructure and phase imaging.

Main Results:

• CPH : SA copolymers exhibit composition-dependent micro-phase separation.
• Micro-domains were observed in 20:80 and 80:20 CPH : SA, but not in poly(SA) or 50:50 CPH : SA.
• Crystallinity decreased and lamellar thickness increased with higher CPH content.
• Hydrophobic drug loading into hydrophobic polymers reduced melting point, an effect amplified by increased drug loading.

Conclusions:

• Micro-phase separation in CPH : SA copolymers is influenced by co-monomer hydrophobicity.
• This phase separation impacts thermodynamic partitioning of incorporated drugs.
• Findings provide insights for precise design of polyanhydride-based drug delivery systems.