Protein C is a plasmatic inhibitor which regulates the blood coagulation me
chanism by modulating the anticoagulant response. The improvement of its bi
oavailability would be beneficial for the treatment of the disorders caused
by its homozygous deficiency or by an other plasmatic inhibitor deficiency
. In this context, the protein C encapsulation into biodegradable nanoparti
cles could be used to approach the problem. However, the method used to pre
pare the nanoparticles requires the use of ultrasonication and of an organi
c solvent such as methylene chloride which interferes with protein activity
. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that nei
ther ultrasonication nor methylene chloride, singly or in combination, led
to protein C aggregation or cleavage. Thus, a binding study using an ELISA
assay with four characterized monoclonal antibodies was carried out to iden
tify the epitopes damaged by these experimental constraints. The correlatio
n between the immunological assay and a functional one i.e. by the means of
the assay of its anticoagulant activity (activated partial thromboplastin
time) made it possible to show that protein C amino acids 166-169 of the ac
tivation peptide were probably altered after ultrasonication and methylene
chloride treatment. Indeed, it is likely that these residues were no longer
surface-exposed but had moved inside the protein core.