Low molecular weight chitosan powder

Polycaprolactone powder (MW 50000 Daltons; Tm = 58°C; PCL) was supplied by Polysciences Inc. The low molecular weight chitosan powder (deacetylation degree ≥ 75%; Tm = 102.5°C; CS) and the 5-Fluorouracil (MW 130.08 g/mol; sparingly soluble in water <1 mg/ml; ≥ 99% HPLC; Tm = 282°C; 5-FU) were purchased from Sigma-Aldrich.

For the dyeing process, two grades of chitosan were selected: low-molecular-weight chitosan powder from Sigma Aldrich (CAS number 9012-76-4, Darmstadt, Germany) and cosmetic-grade chitosan powder from Calaya (Złotów, Poland) natural cosmetic raw materials. In addition, liquid nettle extract containing water, Urtica dioica L. folium, and citric acid with a concentration of 30 g/L (EkaMedica) were used. Food-grade caffeine powder was purchased from Ting Trading Ltd. (Alfreton, United Kingdom) and food-grade rectified spirit (95%) was purchased from Polmos SA (Warsaw, Poland). Citric acid monohydrate pure P.A. was bought from Avantor Performance Materials Poland SA (CAS number 5949-29-1, Gliwice, Poland). Shellac flakes (blonde and dewaxed) were purchased in a local art restoration and conservation shop.

All of the chemicals were at least analytical grade. Low-molecular-weight chitosan powder was purchased from Sigma-Aldrich (Product No. 448869, Darmstadt, Germany), with a deacetylation degree of 91.7% and MW 359 kDa; Arabic gum (Ph Eur, BP) was purchased from Merck (Darmstadt, Germany); glacial acetic acid (ACS 99.7%) was purchased from PanReac (Barcelona, Spain); sunflower oil was purchased from Mercadona S.A (València, Spain); and oregano essential oil (OEO) was acquired from Essenciales (Barcelona, Spain). All of the chemicals were used as received. Ultra-pure water with a resistivity of 18 MΩ cm⁻¹, obtained from a Milli-Q analytical reagent-grade water purification system (Millipore, Burlington, MA, USA), was utilized for all the experimental procedures.