The delivery of drugs or genes to the inner ear in a controlled and biocompatible manner could lead to new treatments<br/>for conditions such as Ménière’s disease, tinnitus, schwannomas of the ear, and for improving hearing.<br/>The concept of multifunctional nanoparticles, which are targetable, biodegradable, and traceable, has led to new<br/>approaches to controlled drug release and localized delivery to specific cell populations. Tissue-specific delivery<br/>can be achieved by functionally “addressed” nanostructures loaded with a therapeutic molecule. In the present<br/>study, we investigated the incorporation, distribution, and toxicology of amphiphilic block copolymer nanoparticles<br/>(NPs) in spiral ganglion (SG) cell cultures. Adult human and guinea pig SG neurons and glia/Schwann<br/>dissociated cell cultures were expanded, grown for several weeks, and then studied live using time-lapse video<br/>microscopy and high-resolution light microscopy. The cells were further characterized using immunocytochemistry<br/>for the neural marker TuJ1 and the glia cell markers S-100 and GFAP, and their morphology was studied<br/>in more detail using scanning electron microscopy (SEM). These cell cultures were exposed to fluorescently<br/>(Dil)-loaded NPs for different time periods and at different concentrations, and the uptake was studied using<br/>fluorescence microscopy. The study demonstrates that DiI-loaded NPs can be internalized into guinea pig SG<br/>neurons as well as into human and guinea pig SG glia/Schwann cells without indication of toxicity or reduced<br/>viability. After 4 hours, almost 100% of both the neurons and the glia cells had incorporated the NPs into the<br/>cytoplasm. No uptake could be detected in the nucleus and no evidence of internalization could be seen in<br/>axons or in the growth cone area of the neuron. Especially in the glia cells, the NPs were detected in small<br/>vesicles surrounding the nucleus and occasionally in the periphery of the cytoplasm. This information could lead<br/>to the development of more specialized NPs, targeting only SG neurons or Schwann cells
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