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A Novel Treatment Tool for PLA-Based Encapsulation Systems †

Konstantina Chronaki
Angeliki Mytara
Constantine D. Papaspyrides
Konstantinos Beltsios
2 and
Stamatina Vouyiouka
Laboratory of Polymer Technology, School of Chemical Engineering, National Technical University of Athens, Zographou Campus, 157 80 Athens, Greece
School of Chemical Engineering, National Technical University of Athens, Zographou Campus, 157 80 Athens, Greece
Author to whom correspondence should be addressed.
Presented at the 2nd International Online Conference on Polymer Science-Polymers and Nanotechnology for Industry 4.0, 1–15 November 2021; Available online:
Mater. Proc. 2021, 7(1), 21;
Published: 1 November 2021


Active-compound encapsulation in polymeric carriers is a widely used technology as it protects and improves the physical characteristics of the active compound and controls its delivery. The effectiveness of polymeric microcapsules (MCs) depends on the barrier properties of the polymeric shell; for a given polymer, the latter properties are affected by its molecular weight (MW) and crystallinity (xc). The aim of this study was to modify the MW and xc of the MCs shell via solid state polymerization (SSP). SSP may take place in the amorphous regions of the polymer upon heating at temperatures higher than the glass transition point (Tg) but lower than the onset of melting (Tm). Poly(lactic acid) (PLA) was chosen as the polymeric carrier and coumarin 6 as the encapsulated compound. PLA is a biobased and biodegradable polymer that is widely used in drug delivery systems, and coumarin 6 is a fluorescent hydrophobic drug that can be used as model compound. The effectiveness of SSP as a post-encapsulation tool was proven for blank PLA MCs of two molecular weights (MW = 50,000 g mol−1 and 20,000 g mol−1). SSP led to a 40–50% enhancement of the weight-average molecular weight of the polymeric shell and to an enhancement, from 40% to up to 70%, of the mass fraction crystallinity in the case of the low-MW MCs. In an attempt to transfer the gained knowledge to the encapsulation systems, coumarin-6-loaded MCs were prepared. The average size of the MCs was measured at 502 nm with a polydispersity index of 1.6 while the encapsulation efficiency was found to be 15% for a drug loading of 10%. UV–Vis measurements showed that the compound was fully released after 10 days. Coumarin 6 was found to be thermally stable at temperatures used for SSP, while the study of SSP application in the case of loaded MCs is in progress.

Supplementary Materials

The following supporting information can be downloaded at:


This research was co-financed by Greece and the European Union (European Social Fund- ESF) through the Operational Programme «Human Resources Development, Education and Lifelong Learning 2014–2020» in the context of the project “Encapsulation of active compounds in polymeric microcapsules: Modifying properties via Solid State Polymerization” (MIS 5049531).
Materproc 07 00021 i001
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MDPI and ACS Style

Chronaki, K.; Mytara, A.; Papaspyrides, C.D.; Beltsios, K.; Vouyiouka, S. A Novel Treatment Tool for PLA-Based Encapsulation Systems. Mater. Proc. 2021, 7, 21.

AMA Style

Chronaki K, Mytara A, Papaspyrides CD, Beltsios K, Vouyiouka S. A Novel Treatment Tool for PLA-Based Encapsulation Systems. Materials Proceedings. 2021; 7(1):21.

Chicago/Turabian Style

Chronaki, Konstantina, Angeliki Mytara, Constantine D. Papaspyrides, Konstantinos Beltsios, and Stamatina Vouyiouka. 2021. "A Novel Treatment Tool for PLA-Based Encapsulation Systems" Materials Proceedings 7, no. 1: 21.

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