I see a few issues with this approach.
First, the magnetic NPs, even though they claim they are biodegradable, may be toxic. I have worked with nanoparticles (and even magnetic NPs), and you don't want them inside you most of the time. I wonder how they made the magnetic ones biodegradable, if they likely contain iron oxide.
Second, this will require an intratympanic injection anyway. So I would like to see a comparison with a slow release gel (Otonomy and Frequency Therapeutics approaches).