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By using fluorescent polysorbate 80 coated poly(n-butylcyanoacrylate) (PBCA) nanoparticles in an in vivo study, direct evidence was found for the presence of nanoparticles entering the brain and retina of rats. The nanoparticles, prepared with a miniemulsion process, were labeled in situ with a fluorescent dye and coated with polysorbate 80. After preparation the particle size, zeta potential, and the molecular weight distribution were determined. BMEC cells were used as an in vitro model for the BBB. The cells showed significant uptake of the particles, but no transcytosis could be observed in vitro. After applying the particles to the animals at two concentrations, cryosections of the brains and retinas were prepared. Regarding the sections of the rats that received the lower dose, co-localization of the applied fluorescent particles and the stained endothelial cells could be detected in the brain and retina, indicating particle internalization in the endothelial cells. Applied at higher doses, the particles could be detected within the brain and retina with few co-localized signals, suggesting passage through the blood-brain and blood-retina barriers.

Fluorescent dye labeled unfunctionalized and functionalized poly(n-butylcyanoacrylate) nanoparticles were prepared using a miniemulsion technique. Amino acid and methoxyPEG functionalization could be introduced by using aqueous solutions as an initiator for the anionic polymerization in the heterophase. All the particles prepared had sizes smaller than 250 nm and negative zeta-potentials. The molar mass distribution of the polymer was dependent on the acid used as the continuous phase and the initiator solution applied. Cells of three lines (HeLa, Jurkat and mesenchymal stem cells) were incubated with the particles. The molar mass of the polymer determined the onset and extent of apoptosis, and the total uptake was determined by the size and functionalization of the particles. Different uptake kinetics were obtained with HeLa and Jurkat cells after incubation with the same particle batch. The intracellular particle distribution, visualized by confocal laser scanning microscopy, did not show significant differences for either of the cell lines or particle batches.