**2. Results**

## *2.1. Cell Culture*

Diclofenac (DCF) and enalapril were tested regarding their effects on freshly isolated SGN in comparison to the known effects of dexamethasone (DMS). At concentrations of 2 × 10−<sup>4</sup> mol/L, surviving SGN were barely found with all three substances (Figure 1a). Survival increased to about 100% at a concentration of 8 × 10−<sup>6</sup> mol/L for DMS and DCF and remained stable for lower substance concentrations. After addition of enalapril, the highest survival of SGN with about 76.8% was achieved at a concentration of 8 × 10−<sup>6</sup> mol/L. In contrast, neurite length was not affected for all three substances (Figure 1b). Here, only some reduction and fluctuations were observed at concentrations of 2 × 10−<sup>4</sup> mol/L and 4 × 10−<sup>5</sup> mol/L, where cell numbers were reduced. Based on the results it was decided to concentrate on DCF and DMS in further experiments.

**Figure 1.** Survival (**a**) and neurite length (**b**) of freshly isolated SGN after addition of different concentrations of DCF, DMS or enalapril. \* *p* < 0.05; \*\*\* *p* < 0.001 against controls. No differences between drugs were detected.

## *2.2. PLLA Coating*

In order to achieve a stable PLLA coating on silicone, the silicone surface (Sil) (Figure 2, left) was activated with O2 plasma and an intermediate layer of Silicone- (3-glycidyloxypropyl)trimethoxysilane (Sil-GOPS, Figure 2, left) was generated using the crosslinker GOPS and functionalized via PLLA-NH2. A stable PLLA coating resulting in Silicone- PLLA (Sil-PLLA, Figure 2, left) could be deposited on this intermediate layer.

In order to illustrate the surface morphology of the different layers, SEM images were taken. The Sil surface (Figure 2a) morphology only slightly changed with addition of GOPS (Figure 2b). However, with addition of the PLLA systems the modified Sil surface became more structured (Figure 2c).

**Figure 2. Left**: General reaction scheme for the coating of silicone surfaces (Sil) with PLLA via the cross linker GOPS (Sil-GOPS) and the PLLA functionalized with amino groups (Sil-PLLA); **Right**: representative SEM micrographs of Sil (**a**); Sil-GOPS (**b**) and Sil-PLLA (**c**) surfaces.

## *2.3. Contact Angle Measurements*

The hydrophilicity of the silicone surface changed with each reaction step as shown by the contact angles (Figure S2, Supplementary Materials). After addition of GOPS the contact angle decreased significantly, by about 50◦. Due to the rather thin interlayer with PLLA-NH2, the measured contact angle changed only slightly. Afterwards, the surface was coated with high molecular weight PLLA and the contact angle again did not change significantly.
