Bridging phycocyanin onto silk by genipin towards durable colouristic, antioxidant and UV protective properties: A sustainable strategy for fully bio-based textile

[Display omitted] •Bluish natural colorant and bio-based crosslinker are integrated to silk.•The PC quantity on silk enhances from 23.5 to 74.4 mg/g by GNP.•All treated silk display high levels of washing and rubbing fastness.•GNP enhances the thermal stability of PC that benefits processing control.•Almost no strength loss occurs on silk owing to the milder processing condition. Integrating bio-extracts with natural fabric towards fully bio-based textiles is broadly advocated that benefits customers’ health and the environment. However, promoting the durability aside from using synthetic fixer or metal mordant, and exploring new source for blue bio-colorant are two challenging issues at this stage. To address this issue, a blue bio-colorant phycocyanin (PC) and a bio-crosslinker genipin (GNP) are combined to silk for durable blue appearance and UV protective/antioxidant functions. In the presence of GNP, the PC quantity on silk dramatically increases from 23.5 to 74.4 mg/g which enhances the colour depth and functionalities of silk. Moreover, the PC/GNP treated silk achieves high ratings in the washing and rubbing tests. Those two results demonstrate the dual roles of GNP for promoting the affinity/durability of PC to/on silk. The condition, i.e., 10 % owf of PC, 1 g/L GNP, 70 °C and 3 h is recommended considering the colour strength and fastness of silk, thermal stability of PC, reactivity of GNP and effective crosslinking between PC and silk. PC (10 % owf) imparts silk with high UPF value up to 39 and scavenges over 70 % of free radicals within 60 min. Almost no strength loss occurs on silk thanks to this milder processing condition. The designed PC, GNP and silk crosslinking system expands the applicable area of silk which represents the next-generation fully bio-based silk product.