Understanding microstructural evolutions of drug delivery devices during drug release process
is essential for revealing the drug release mechanisms and controlling the drug release profiles.
In this study, monodisperse poly (lactic-co-glycolic acid) microspheres in different diameters were
fabricated by microfluidics in order to find out the relationships between the microstructural evolutions and the drug release
profiles. It was found that poly (lactic-co-glycolic acid) microspheres underwent significant size expansion which
took place from the periphery to the center, resulting in the formation of interfacial fast release layers. At the same time,
inner pores were created and the diffusion rate was increased so that the early stage drug release was accelerated. Due to
the different expansion rates, small poly (lactic-co-glycolic acid) microspheres tendered to follow homogeneous drug release
while large poly (lactic-co-glycolic acid) microspheres tendered to follow heterogeneous drug release. This study
suggests that the size expansion and the occurrence of interfacial fast release layer were important mechanisms for early
stage drug release of poly (lactic-co-glycolic acid) microspheres.
Keywords: Controlled drug delivery, drug release mechanism, interfacial fast release layer, microfluidics, microstructural evolution,
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