Figure 2 . Water contact angles of cellulose acetate nanofiber (CA) (a) and cellulose acetate nanofiber impregnated with annatto extract (CA@A) (b).
As Figure 2 shows, both nanofiber types were hydrophilic, with contact angles below 90°. The contact angle for the CA nanofiber was approximately 77±3°, while adding annatto to the CA decreased the contact angle to 50±3. This effect can be attributed to the hydrophilic nature of annatto molecules such as norbixin. A more hydrophilic nanofiber surface is ideal for supporting cell attachment. According to Menzies et al. [37], the hydrophilicity of a material directly corresponds to its capacity for cell adhesion. Improved wettability (evidenced by low contact angle values in water tests) results in improved biocompatibility for the analyzed material.