PVO was synthesized by polymerization of an acid-cleavable vanillin derivative and oxalyl chloride, as previously reported.20 (link) Briefly, the acid-cleavable vanillin derivative was added to a flask containing 25 mL dry dichloromethane and pyridine (9.8 mmol). The flask was placed in an ice bath, followed by the addition of oxalyl chloride (3.941 mmol); the mixture was maintained at room temperature for 6 h. PVO was obtained by extraction with dichloromethane/water and precipitation in cold hexane. The chemical structure of the PVO was analyzed using nuclear magnetic resonance spectroscopy (JNM-ECZ500R, JEOL, Akishima, Japan) and Fourier transform infrared (FT-IR) spectrometer (Spectrum 3, Perkin Elmer, Shelton, USA) after purification. PVO nanoparticles were prepared using a previously reported single-emulsion method.20 (link) PVO nanoparticles suspended in water or lysates from neurite tissue 24 h after induction were characterized using a scanning electron microscope (SUPRA40VP, Carl Zeiss, Jena, Germany) and nanoparticle size analyzer (Brookhaven Instruments Corporation, Holtsville, NY, USA) using dynamic light scattering.