Design of hydrophobic zein/dye-LDHs biohybrid pigments for cosmetic applications

Pigments with color diversity, hydrophobicity, biocompatibility and photostability are significantly attractive in cosmetic, but it is still a challenge to invent them. To achieve this promising goal, this study demonstrates an unprecedented concept of pigments from assembling zein protein to dye-modified layered double hydroxides (zein/dye-LDHs) by a simple two-step method. Elaborate characterizations including X-ray powder diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, Ultraviolet-visible absorption spectra and thermogravimetric analysis confirm the successful exploration of zein/dye-LDHs biohybrid with the sandwich structure that dye is intercalated into the interlayer space of LDHs by the host-guest interaction between host sheets and guest dye anions, while zein is grafted on dye-LDHs surface via electrostatic interactions and hydrogen bonds. The intercalation into the interlayer region of LDHs and zein grafting remarkably improved the hydrophobicity and photostability of organic dyes and obviously decreased their irritation potential. Further, the diversified color could be easily achieved via adjusting the dosage of pigment and the lipstick formulated with zein/dye-LDHs demonstrated good water resistance, low color migration, natural appearance and high sustainability. These results open a new direction for fabricating pigment with adjustable color hue, good hydrophobicity, high photostability and outstanding biocompatibility, which would inspire more exploration of other biohybrid pigments and applications.