Curcumin

The stock solution (100 mM) of curcumin (Carl Roth, Karlsruhe, >90.6%) was prepared by dissolving in DMSO (Fluka Analytical, Buchs, Switzerland). SACUR-12a [42 ] was kindly provided by Dr. Andreas Spaeth (Institute of Organic Chemistry, University of Regensburg, Regensburg, Germany). A stock solution (5 mM) of SACUR-12a was prepared in ddH₂O. Both stock solutions were stored at −20 °C in the dark until use. The chemical structures of curcumin and SA-CUR 12a [42 ] are shown in Figure 10.

Aqueous acidic solutions (pH ~ 2, HCl) of type I atelocollagen (AteCol) and poly(ε-caprolactone) diisocyanate (PCL-DI, Mn ~2.5 kDa) were prepared according to the protocols outlined in the literature [25 ,26 ]. Dimethylsilanediol hyaluronate (DMSHA) (aqueous solution of pH ~ 5.5, 0.6% with 0.3% hyaluronan of nonanimal origin with Mw of 1.8–2.2 MDa) was kindly donated by EXSYMOL S.A.M. (Monaco). Suprasorb C collagen wound dressings (Lohmann & Rauscher, Rengsdorf, Germany) were used as reference samples (Col LR). Curcumin (CU), ≥90% (reagent from Carl Roth, Karlsruhe, Germany) was used as received. Methylene blue (MB), phosphate buffered saline tablets (PBS, pH 7.4) and solvents (acetone p.a., dimethylsulfoxide puriss p.a.-DMSO, absolute ethanol for HPLC, glycerol ≥99.5%), purchased from Sigma–Aldrich (Darmstadt, Germany), were used without further purification. Triton X-100, poly(vinyl pyrrolidone) K15 were supplied by Sigma-Aldrich (Darmstadt, Germany). Bidistilled water or Milli Q ultrapure water was used in all experiments. The antibacterial activity of the investigated collagen-based materials loaded with Curcumin was evaluated on the Gram-positive strain of Staphylococcus aureus ATTC 25923.