Curcumin

Bombyx mori silk cocoons were reared in the sericulture facilities of IMIDA (Murcia, Spain) and raised on a diet of natural fresh leaves of Morus alba L. To extract the SF, the raw silk cocoons were shredded in a mill to a particle size of 1 mm, and then boiled in a 0.1 M Na₂CO₃ aqueous solution for 120 min to remove sericin, waxes, and impurities. The remaining water-insoluble SF was rinsed thoroughly with ultrapure water and air-dried in a fume hood until constant weight (approximately 24 h). Hyaluronic acid sodium was purchased from Monteloeder Digital Nutracetics (MW 8 × 10⁵ Da, >90% purity). Curcumin (99% purity) was purchased from ChromaDex (Irvine, CA, USA). Purified water (18.2 MΩ·cm at 25 °C; from a Millipore Direct-Q1 ultrapure water system, Billerica, MA, USA) was used throughout. All other chemicals and solvents were of analytical grade and were used without further purification.

B. mori silk cocoons were reared in the sericulture facilities of the IMIDA (Murcia, Spain) and raised on a diet of natural Morus alba L. fresh leaves. To obtain SF, raw silk cocoons were boiled twice in a 0.05 M Na₂CO₃ aqueous solution for 45 min. The remaining SF was rinsed thoroughly with ultrapure water and dried prior to use. SF was dissolved in the ionic liquid 1-ethyl-3-methylimidazolium acetate, [emim⁺][CH₃COO⁻], by high-power ultrasound, as previously reported [66 (link)]. The ionic liquid (95% purity) was purchased from IoliTec GmbH (Frankfurt, Germany) and was used without further purification. Curcumin (99% purity) was purchased from ChromaDex (Irvine, CA, USA). Purified water (18.2 MΩ·cm at 25 °C; from a Millipore Direct-Q1 ultrapure water system, Billerica, MA, USA) was used throughout. All other chemicals and solvents were of analytical grade and were used without further purification.

Chitosan—low molecular weight, phosphate-buffered saline tablets, select yeast extract, tryptone, agar, Tween 80, and l-histidine dihydrochloride were purchased from Sigma-Aldrich; acetic acid, sodium chloride p.a., and n-hexane 99% p.a. from Penta Chemicals; sodium tripolyphosphate (TPP) from Acros Organics; ethanol 99.8% for UV/VIS spectroscopy, and glycerol anhydrous g. r. from Lach-Ner; curcumin 99.9% from Chromadex; Brain–Heart-Infusion broth (BHI, Hirn-Herz-Glucose-Bouillon für die Mikrobiologie) from Carl Roth; sunflower lecithin from Fichema s.r.o. Materials for finger replica preparation—FIMO^® soft oven-bake modelling clay and liquid silicon paste with a hardener were purchased from Staedtler.
Antimicrobial foam soap was purchased from Tork. Chlorhexidine digluconate (CHG) 25% w/w aqueous solution was provided by Zentiva, k.s. Two commercially available sanitisers used as a positive control for bacterial testing were purchased in a local store, i.e., ethanol-based gel (72% w/w) from Sanytol and 2% CHG alcoholic solution (IPA 70% v/v) from B. Braun Medical AG.