*2.5. Drug Release*

As shown in Figure 4a, the DMS release is influenced by the addition of the PLLA coating. For the uncoated silicone samples, the released amounts of DMS are significantly higher compared to the coated samples. Around 24 μg DMS was released after 92 days, in contrast to the coated samples where 7 to 10 μg DMS was released in the same amount of time. Furthermore, the additionally incorporated DCF in the PLLA coating (Sil-DCF/PLLA) increases the DMS release significantly from day 1 compared to the other coated samples.

**Figure 3.** FTIR spectra of investigated Sil based samples Sil, Sil-GOPS, Sil-PLLA-NH2, Sil-PLLA in the range of 4000–500 cm<sup>−</sup>1. The prominent band between 1764–1712 cm<sup>−</sup><sup>1</sup> corresponds to PLLA signals.

**Figure 4.** Cumulative in vitro release of incorporated substances from the samples with and without PLLA coating; (**a**): DMS release from uncoated and coated samples (Ø = 6 mm; DCF: PLLA 5: 95 wt%, *N* = 3) Release was with *p* < 0.05 significantly different between all investigated systems after 1 day. (**b**): DCF release from PLLA coated samples (DCF: PLLA 10: 90 wt% and 20: 80 wt%, *N* = 3). Release was with *p* < 0.05 significantly different between days 0 to 71.

Besides the influence of the PLLA coating on the DMS release, also the release of DCF from the PLLA coating was characterized. In vitro release studies with 10 and 20% DCF in the coating were performed. As shown in Figure 4b, a significantly higher burst release was detected for the samples with 20% DCF content compared to the 10% samples. After only one day of release, more than 50% of DCF was already released from the 20% DCFcontaining samples in contrast to the 10% DCF-containing samples with only 4% released DCF. With 10% DCF in the coating, it took about 20 days to release 50% of the DCF.
