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Terahertz Spectroscopy: An investigation of the Structural Dynamics of Freeze-Dried PLGA Microspheres

preprint
revised on 09.01.2019 and posted on 09.01.2019 by Talia Shmool, Philippa J. Hooper, Gabi Kaminski, Christopher F. van der Walle, J. Axel Zeitler
Biodegradable poly lactic-co-glycolic acid (PLGA) microspheres can be used to encapsulate peptide and offer a promising drug delivery vehicle. In this work we investigate the dynamics of PLGA microspheres prepared by freeze-drying and the molecular mobility at lower temperatures leading to the glass transition temperature, using temperature-variable terahertz time-domain spectroscopy (THz-TDS) experiments. The microspheres were prepared using a water-in-oil-in-water (w/o/w) double emulsion technique and subsequent freeze-drying of the samples. Physical characterisation was performed by morphology measurements, scanning electron microscopy (SEM), and helium pycnometry. The THz-TDS data show two distinct transition processes, Tg,β in the range of 167-219 K, associated with local motions, and Tg,α in the range of 313-330 K associated with large-scale motions, for the microspheres examined. Using FTIR measurements in the mid-infrared we were able to characterise the interactions between a model polypeptide, exendin-4, and the PLGA copolymer. We observe a relationship between the experimentally determined Tg,β and Tg,α and free volume and microsphere dynamics.

Funding

EPSRC EP/N022769/1

Medimmune

Kenneth Lindsay Trust

History

Email Address of Submitting Author

jaz22@cam.ac.uk

Institution

University of Cambridge

Country

United Kingdom

ORCID For Submitting Author

0000-0002-4958-0582

Declaration of Conflict of Interest

We declare no conflict of interest.

Licence

Exports