Fig 2: Phototriggered release of brain-derived neurotrophic factor (BDNF) from photocleavable nanoparticles (PCNs) and its effects on the growth and maturation of human neural progenitor cells (hNPCs). (a) Amounts (%) of BDNF released in hNPCs at different energy densities (0, 30, 60, and 90 J/cm2) after laser irradiation. Irradiation at 60 J/cm2 (89.15%) showed BDNF release that was higher relative to 30 J/cm2 (69.01%) but not significantly higher than 90 J/cm2 (90.76%). (b) hNPCs were grown in culture for 3 days prior to PCN or laser treatment, and the medium was changed to neuronal differentiation medium (NDM) containing no BDNF. Maturation effects were determined after 7 days in NDM (D10). (c) The neural progenitor cell marker Nestin had significantly higher mean fluorescence intensity relative to PCN only and PCN + 90 J/cm2, as assessed by immunohistochemical staining (d). (e) The corresponding immunofluorescence images also observed a higher mean fluorescence intensity with PCN + 60 J/cm2 for the mature neuronal cell marker NeuN (f). Groups were compared using one-way ANOVA with Tukey’s multiple comparisons test (**** P < 0.0001)

Fig 3: Effects of laser and photocleavable nanoparticles (PCNs) loaded with brain-derived neurotrophic factor (BDNF) on ouabain-induced neuronal damage in vestibular ganglion neuron (VGN) organoids. (a) Confocal images of VGN organoids cultured in a differentiation medium for 21 days showed a decrease in Nestin expression with neurotrophic factor NT-3 without BDNF. (b) The mature neuronal cell marker NeuN also decreased without BDNF in the medium, as shown in the mean fluorescence intensity graph. (c) VGN organoids ouabain treatment concentration and cytotoxicity evaluation schedule. (d) Immunofluorescence staining revealed a decrease in NeuN expression with increasing ouabain concentration, with a significant decrease in cell viability. (e) Ouabain induced damage in VGN organoids in a dose-dependent manner, with a 0–5% decrease in cell viability observed with 1 mM after 24 h. (f) An experimental schedule of PCNs and laser treatment of VGN organoids damaged by ouabain were used. (g) Immunofluorescence images after ouabain, PCN, and laser treatments with a corresponding assessment of (h) the length and number of Nestin-positive cells. Few Nestin-expressed cells were observed in the control or ouabain group, while the PCN- and the number and length of Nestin-positive cells were markedly increased in the laser-treated groups, except at the energy level of 90 J/cm2. Groups were compared using one-way ANOVA with Tukey’s multiple comparisons test (**** P < 0.0001)