Figure 6.

XPS analysis was used to assess the stability of NGF-immobilized PPy-NSE₅₀ films. (a) High-resolution C_1s spectra of the PPy-NSE₅₀ samples (i) freshly prepared and (ii) incubated, and of the NGF-immobilized PPy-NSE₅₀ samples (iii) freshly prepared and (iv) incubated. Incubation was carried out for 5 days in PBS buffer at 37°C in a cell culture incubator. (b) C_1s and N_1s ratios of NGF-immobilized PPy-NSE₅₀ films (NGF) and non-treated PPy-NSE₅₀ films (no NGF). After the incubation, the ratios of both incubated films (black bars) were compared with those of freshly prepared films (grey bars). NGF on the film surfaces affects the ratios of C_1s and N_1s.