ARTICLE
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particle mean diameter and polydispersity index given by
dynamic light scattering remained quasi the same. However,
pronounced hydrolysis of the activated esters was shown to
proceed with time (as also pointed out earlier18). The
amount of hydrolyzed esters could be obtained by measuring
the OD by adding the ethanolamine in the supernatant of the
particle dispersions after centrifugation. After 3 months, the
fraction of hydrolyzed esters on the total available was
determined to be more than 75%. This was confirmed by
the poor colloidal stability of the dispersion with a floccula-
tion observed at less than 0.5M NaCl, showing that the esters
were hydrolyzed to carboxyl ionic groups thus reducing the
steric contribution to stabilization. This underlines that the
reactive groups of these promising novel functionalized PLA
nanoparticles should be used within a limited time after
preparation, if not freeze-dried.
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CONCLUSIONS
10 Knop, K.; Hoogenboom, R.; Fischer, D.; Schubert, U. S.
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In this work, MAMA-SG1 alkoxyamine-initiated NMP was suc-
cessfully applied to synthesis of well-defined PNAS and
P(NAS-co-NVP) polymers. The homopolymerization of NAS
was controlled in the presence of SG1. A strong alternating
tendency was observed for the copolymerization of NAS with
NVP and the obtained copolymers exhibited acceptable poly-
dispersities and adjustable molecular weights, consistent
with a controlled process. The NMP of NAS/NVP was then
initiated with a PLA-SG1 macro-alkoxyamine previously pre-
pared, leading to PLA-b-P(NAS-co-NVP) block copolymer. The
latter was involved as a particle surface modifier in the PLA
nanopreciptation and diafiltration processes, to achieve
nanoparticles of targeted size with a hydrophilic and highly
functionalized interface. The presence of the NS reactive
groups was clearly evidenced by zeta potential, colloidal sta-
bility measurements and UV-based determination of the
releasing NHS anion upon ethanolamine derivatization. We
are currently focusing on the freeze-drying process of these
particles to limit NS ester hydrolysis and investigating the
coupling on these novel particles of ligands such as mannos-
amine or immunostimulating molecules for further vaccine
delivery applications.
11 Dove, A. P. Chem Commun 2008, 6446–6470.
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The authors are grateful to Arkema, Universite´ de Provence and
CNRS for financial support and Marilyne Malbouyres (IBCP)
and Be´atrice Burdin from the Centre Technologique des Micro-
structures (Lyon, France) for SEM experiments. Part of this
work has been funded through two grants from European
Union (Europrise and Cuthivac) to E. Luciani and B. Verrier.
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