Survival rates of spiral ganglion neurons after a cultivation of two days.

<p>Cells were cultivated in presence of the supernatants from the release experiments of BDNF-loaded amino-modified NPSNPs (NPSNP-NH₂-BDNF) or of amino-modified NPSNPs (NPSNP-NH₂) as control experiment. Values are given as mean ± standard error of the mean (<i>N</i> = 3, <i>n</i> = 3). Statistical assessment was performed using one-way ANOVA with Bonferroni´s multiple comparison test (n.s. = not significant, *p<0.05; **p<0.01; ***p<0.001). Asterisks over the bars indicate the significance of the survival rates of different conditions compared to the medium control (serum-free SGC medium). Asterisks between two bars indicate the significance between the different conditions.</p

Comparison of the survival rates of spiral ganglion neurons after 48 h hof cultivation.

<p>Cells were cultivated in the presence of amino-modified nanoparticles (NPSNP-NH₂; light grey), BDNF-loaded amino-modified nanoparticles (dark grey) and amino-modified nanoparticles with an exogenous addition of 50 ng mL^-1 BDNF (light grey, striped). Values are given as mean ± standard error of the mean (<i>N</i> = 2, <i>n</i> = 3). Statistical assessment was performed using one-way ANOVA with Bonferroni´s multiple comparison test (n.s. = not significant, *p<0.05; **p<0.01; ***p<0.001). Asterisks over the bars indicate the significance of the survival rates of different conditions compared to the negative control (serum-free SGC medium). Asterisks between two bars indicate the significance between the respective conditions.</p

Scheme of the possible interactions between BDNF with (left) unmodified NPSNPs and (right) amino-modified NPSNPs.

<p>With unmodified NPSNPs, BDNF can interact via hydrogen bonds and electrostatic interactions, and with amino-modified NPSNPs via hydrogen bonding, electrostatic interactions and via hydrophobic effects. This schematic view does not show the nanoparticles, atoms and the protein with their real sizes.</p

Microscopic images of spiral ganglion cells (SGCs) after two days of cultivation in different media composition.

<p>The cells were cultivated in presence of the supernatants from the release experiments of BDNF-loaded amino-modified NPSNPs (NPSNP-NH₂-BDNF) or of BDNF-free amino-modified NPSNPs (NPSNP-NH₂). For comparison, SGCs were also cultivated in serum-free SGC medium (medium) and in serum-free medium supplemented with BDNF (50 ng mL^-1 BDNF) as well as in a 1:1 serum-free medium/PBS (0.1% BSA) solution.</p

Neurite length of SGNs cultivated with BDNF-loaded (dark grey) and BDNF-free NPSNPs with (light grey, striped) or without (light grey) an additional exogenous BDNF supply.

<p>Values are given as mean ± standard error of the mean (<i>N</i> = 2, <i>n</i> = 3). Statistical assessment was performed using one-way ANOVA with Bonferroni´s multiple comparison test (n.s. = not significant, *p<0.05; **p<0.01; ***p<0.001). Asterisks over the bars indicate the significance of the survival rates of the different conditions compared to the medium control (serum-free SGC medium).</p

Relative cell viabilities of NIH3T3 fibroblasts in the presence of unmodified and amino-modified nanoparticles in different concentrations determined by the NRU assay after an incubation for four days.

<p>Values are given as mean ± standard error of the mean (<i>n</i> = 3).</p

BDNF release profile of unmodified NPSNPs in PBS (0.1% BSA) over 60 days at 37°C.

<p>The left axis represents the cumulative BDNF release with regard to 1 mg of nanoparticles and the right axis shows the cumulative release of BDNF referred to 1 mL release medium.</p

Representative microscopic images of spiral ganglion cell cultures cultivated for 48 h.

<p>The cells were cultivated in the presence of amino-modified nanoparticles (w/o BDNF), BDNF-loaded amino-modified nanoparticles (immobilized BDNF) and amino-modified nanoparticles with an exogenous addition of 50 ng mL^-1 BDNF (exogenous BDNF) in two different concentrations. For comparison, SGCs were also cultivated in serum-free SGC medium (medium) and in serum-free medium supplemented with BDNF (50 ng mL^-1 BDNF) as well as in a serum-free medium/PBS solution (1:1) (PBS (0.1% BSA)).</p

Zeta potential titration curves for the unmodified NPSNPs in comparison to the amino-modified NPSNPs.

<p>Zeta potential titration curves for the unmodified NPSNPs in comparison to the amino-modified NPSNPs.</p

BDNF release profile of amino-modified NPSNPs in PBS (0.1% BSA) over 80 days at 37°C.

<p>The left axis represents the cumulative BDNF release with regard to 1 mg of nanoparticles and the right axis shows the cumulative release of BDNF referred to 1 mL release medium.</p