Fabrication and characterization of aerogels from cysteine-S-sulfonated keratin for drug delivery applications

A purified-keratin solution obtained from wool fibers by sulfitolysis extraction was employed to produce hydrogels with and without crosslinking. Both hydrogels were used to successfully obtain aerogels by supercritical CO₂ drying. Freeze-dried keratin was also produced from purified keratin solutions as reference materials. The stability of the aerogels in aqueous solution was demonstrated for the aerogels with crosslinking. Negative zeta potential values and FT-IR spectrums confirmed the presence of sodium dodecyl sulfate (used for protein extraction) on the keratin structure. This surfactant can be removed during solvent exchange in aerogel fabrication, making the hydrophobic cavities of proteins accessible to other molecules. Curcumin was loaded as model hydrophobic compound on the alcogels before supercritical drying. The drug release from aerogels loaded with curcumin was studied over time, showing self-degradation in phosphate buffer solution when released from the aerogel without crosslinking due to the complete solubilization of the protein. In the aerogel with crosslinking, cumulative curcumin release was more sustained over time. Aerogels produced in this work can be successfully used as a drug delivery system, since they can protect hydrophobic cargoes inside the hydrophobic protein cavities.