Natural Dyed Watch Strap: Chemical Mordant Free Dyeing with Mordanted Homoisoflavonoids and Anthocyanins for Biocompatible and Wound-Healing Wearables

Abstract

Natural dyes with chemical mordant are often toxic and nonbiodegradable, posing serious environmental and health risks due to their harmful residues and lack of sustainability. This study presents the development of an eco-friendly, multifunctional (antimicrobial, anti-oxidant, biocompatible, UV protective, and hydrophobic) watch strap made from leather dyed with natural resources, offering a sustainable alternative to synthetic dyes. The natural dye brazilein, extracted from Biancaea sappan wood (SW), initially produced a lighter colored leather. To enhance the hue, a natural mordant derived from banana flower bracts (FB) was used as a cost-effective alternative to chemical mordants. The magnesium ions and anthocyanins in the FB extract complexed with the SW dye, significantly improving the color intensity and uniformity. The optimized 30% SW and 10% FB combination delivered vibrant leather with superior mechanical strength, lightfastness, and rub fastness comparable to synthetic dyes. The SW-FB-dyed leather also exhibited antimicrobial, antifungal, antioxidant, and biocompatible properties, showing no adverse effects on fibroblast cells. The dyed leather was fashioned into a watch strap and demonstrated excellent durability, strength, and rub resistance, suitable for daily use. Over time, the shelf life of the dyed leather was compromised by bacterial growth on the surface due to the loss of anthocyanins. Hence, a protective coating of zinc-polyphenols@ silica Janus nanoparticles was applied. This coating provided UV-blocking and hydrophobic properties, preventing bacterial growth and enhancing the leather’s longevity. This process achieved an Eco-scale score of 96.65, outperforming leather dyed with chemical mordants (88.86). This innovative approach of utilizing waste-derived materials for dyeing and mordant applications offers a sustainable, high-performance solution for fabric goods, promoting environmental benefits and new commercial opportunities in eco-friendly products.