posted on 2013-03-04, 00:00authored byPatrizia Andreozzi, Chiara Martinelli, Randy P. Carney, Tamara M. Carney, Francesco Stellacci
The field of nanotheranostics encompasses the integration
of nanosized
carriers in cancer imaging, diagnosis, and therapy. The use of nanomedicines
for theranostic application typically depends on direct visualization
of the nanocarriers. Normally fluorescent probes are attached to nanocarriers
for biodistribution measurement through fluorescence imaging. However
continued, noninvasive assurance that the fluorescent probe remains
bound to the carrier has proven elusive. Mature erythrocytes, also
known as red blood cells, are incapable of endocytosis. As a consequence,
when incubated with fluorescently labeled particles, they do not show
any signal coming from the membrane or the cytoplasm. Yet, these cells
readily take up free BODIPY fluorescent dyes into their membranes.
Here we show that incubation of nanoparticles with erythrocytes is
a rapid and reliable method for the detection of unbound dye present
within a nanoparticle sample, as the detection of a fluorescent signal
coming from the cells can only be due to unbound dye present in the
sample. We test the method on both sulfonate and PEG terminated gold
nanoparticles, and we determine the minimum concentration of detectable
dye for a specific gold nanoparticle sample.