Construction of fish scale (Cyprinus carpio L.) gelatin-fatty acid conjugate for loading curcumin: Effect of alkyl chain length on the interaction and stability

A fish scale (FS) gelatin-fatty acid conjugate (GFC) with alkyl chain lengths of 8-18 was constructed to increase the aqueous solubility of curcumin. The effect of alkyl chain length on the interaction between GFC and curcumin was characterized by dynamic light scattering (DLS), X-ray photoelectron spectroscopy (XPS), fluorescence spectroscopy (FS), and isothermal titration calorimetry (ITC). The surface hydrophobicity (from 4987 ± 223.79 to 9982 ± 262.78) and curcumin loading capacity (from 8.20 ± 0.54 to 31.18 ± 1.41 μg/mg) of the GFC exhibited significant enhancements through increasing alkyl chain lengths from 8 to 18. This was accompanied by a reduction in particle size (from 661.5 ± 28.9 to 329.7 ± 6.6 nm) and ζ-potential (from -2.7 ± 0.92 to -26.8 ± 0.27). FS and ITC confirmed that GOC shared an optimal binding constant (K_a, 2.40 × 10⁸ L·mol^-1 and 3.47 × 10⁵ M^-1) and binding site (n, 1.45 and 2.276) with curcumin among GFCs. Increasing GFC's alkyl chain length also boosted the stability of entrapped curcumin against the thermal environment and ultraviolet radiation. These results could be beneficial for gelatin-based nanocarrier development and application.