Effect of encapsulating a pseudo-decapeptide containing arginine on PLGA: a solid-state NMR study

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomedical Engineering

Background:

• Understanding host-guest interactions in amorphous systems is crucial for reproducible drug delivery formulations.
• Molecular-level insights into drug-polymer interactions are often lacking in traditional bulk property assessments.
• Stabilization mechanisms of drugs within polymeric networks are key for consistent composite performance.

Purpose of the Study:

• To investigate the molecular-level effects of an amorphous decapeptide on poly(lactic-co-glycolic acid) (PLGA) chain dynamics.
• To characterize the nature and extent of drug-polymer interactions within composite materials.
• To correlate dynamic changes with bulk properties for improved understanding of drug stabilization.

Main Methods:

• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy was employed to study molecular dynamics.
• Techniques included relaxation time estimation and 2D wideline separation (2DSWD).
• Glass transition temperature (T(g)) measurements were used to assess bulk properties.

Main Results:

• Evidence for the formation of a drug-polymer solid solution was observed.
• Significant alterations in local dynamics of both the decapeptide guest and PLGA polymer were detected, dependent on loading levels.
• Changes in cooperative polymer chain motions were attributed to guest-polymer interactions.

Conclusions:

• The study successfully combined solid-state NMR and bulk property measurements to elucidate amorphous host-guest interactions.
• Guest-polymer interactions significantly modify local and cooperative dynamics in PLGA composites.
• Differential affinities of glycolide and lactide units for interaction were apparent, offering insights for formulation design.