Herein,
we describe the production of poly(hydroxybutyrate-
co
-hydroxyvalerate) [P(HB-HV)]-based microspheres containing
coumarin-6 (C6) or pyrene (Py) fluorophores as additives and models
for hydrophobic and hydrophilic drug encapsulation. Their photophysical
and morphological properties, as well as encapsulation efficiencies,
are studied as this work aims to describe the influence of additive
hydrophobicity/hydrophilicity on microparticle formation. These properties
were studied by scanning electron microscopy, fluorescence confocal
laser scanning microscopy (FCLSM), and steady-state fluorescence spectroscopy.
The results show that the surfactant concentration, polymer molar
mass, emulsification stirring rate, and the presence of the fluorophore
and its nature are determinants of the P(HB-HV) microsphere properties.
Also, encapsulation efficiency is shown to be governed by synergic
effects of these parameters on the formation of microspheres. Moreover,
size distribution is proved to be strongly influenced by the surfactant
poly(vinyl alcohol) content. FCLSM showed that the fluorophores were
efficiently encapsulated in P(HB-HV) microspheres at distinct distributions
within the copolymer matrix. Surprisingly, nanospheres were observed
in the microsphere surface, suggesting that microspheres are formed
from nanosphere coalescence.