Antioxidant and antibacterial activity of silk fibers using curcuminoids bioinks

Natural plant dyes offer functional properties and have been widely used in various applications. Curcumin, a compound derived from plant rhizomes, holds promise beyond its medicinal and food uses, with potential applications in biomedical auxiliary materials. However, its limited water solubility and low extraction efficiency hinder its practical use. This study aimed to enhance the water solubility of curcumin by formulating a bioactive ink and utilizing inkjet printing to deposit it onto silk fabric, thereby imparting antioxidant and antibacterial properties. We employed ultrahigh-performance liquid chromatography (UPLC) to analyze the composition of extracted curcumin derivatives and investigated the effects of cationic surfactants (CTAB) and nonionic polymers (P407) on the physical properties of curcumin solutions. The antioxidant and antibacterial activities of both homemade curcumin bioactive inks (Bio-CP inks) and curcumin derivative standards (curcumin, CUR; demethoxycurcumin, DMC; bismethoxycurcumin, BDMC) were compared. The surface structure, water binding properties, and crystalline structure of Bio-CP ink-treated silk fibers (Bio-CP@Silk) were characterized using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). Our findings revealed that curcumin is a mixture of CUR, DMC, and BDMC. By pretreating silk fibers with sodium alginate (SA) and sodium carboxymethylcellulose (CMC) (SA-CMC@Silk), the fabric’s surface hydrophilicity was reduced from 60.90° to 115.2°, improving the pattern clarity during inkjet printing of Bio-CP ink. The resulting functional silk fabric (Bio-CP@Silk) demonstrated excellent antioxidant and antibacterial properties. For example, Bio-CP@Silk showed DPPH (2,2-diphenyl-1-picrylhydrazyl) scavenging rate of 69.38%, whereas in untreated silk it was only 4.82%. While the crystalline structure of Bio-CP@Silk fibers remained unchanged, the interaction between curcumin and silk fibers was strengthened, leading to improved water retention capabilities. This approach offers a novel avenue for the functional application of curcumin in silk fiber-based materials.