Jinhua Li

Heat damage is a common phenomenon that often occurs when drying and straightening hair. After heat damage, the hydrophobic barrier on the hair’s surface becomes disrupted, thereby altering the hair’s hydrophilicity. Meanwhile, during the process of heat damage, the rupture of the hair’s cuticles causes the hair to become dry and rough, with a decrease in gloss and a decline in mechanical properties. This study utilized epoxy silane and hydrolyzed wool keratin to synthesize a thermally responsive organic silicon-modified keratin (OSK) to prevent hair from heat damage. OSK was synthesized from epoxy silane and hydrolyzed keratin, with yield determined by quantifying free amino groups. Its hair-care performance was evaluated through assessments of hair surface morphology, mechanical properties, and optical gloss, and by combing test and contact angle measurements. Mechanisms underlying surface hydrophobicity and hair scale protection were investigated using FTIR, XPS, and DSC. Specific performance parameters were evaluated using a single-fiber strength tester and a multifunctional hair-testing instrument. FTIR confirmed successful covalent grafting, with synthesis optimized to a 90.67% yield. OSK forms a protective film on hair surfaces, verified by SEM, XPS, and TEM, restoring damaged hair hydrophobicity to a 117° contact angle and enhancing thermal protection to 136° upon heating. Beyond hydrophobic-barrier restoration, OSK improved hair gloss by 30.26% and reduced frizz by 39.33%, while restoring the key performance of virgin hair. It also provides exceptional water-repellency protection and sensory enhancement. Under thermal stress, the protective film mechanically increased tensile strength by 6.58% and yield zone tensile force by 4.65%. This article demonstrates that OSK is an effective heat-sensitive agent. When damaged by heat sources such as hair dryers, it will form a protective film on the surface of the hair, thereby protecting the surface properties of the hair.

Conventional perming relies on oxidative agents that significantly damage hair. The thiol–Michael click perming strategy derived from linear aliphatic diols and diamines has been developed to avoid oxidative damage, but lacks repeatable perming capabilities. In this study, a novel thiol–Michael click perming molecule was proposed for repeatable perming while avoiding oxidative damage. N,N′-bis(maleoyl)-l-cystine (MA2-CySS) was synthesized and characterized through Raman spectroscopy and ¹H NMR with MTT assay demonstrated no cytotoxicity up to 1000 μg/mL. Click reactivity analysis revealed that the reaction reached a plateau after 30 min, with alkaline pH and elevated temperatures significantly enhancing reactivity. MA2-CySS perming achieved efficiency comparable to oxidative perming, exceeding 1300% across three perming cycles. MA2-CySS perming significantly reduced both color change and cuticle damage, as demonstrated by color difference measurements and SEM, while maintaining superior mechanical properties as revealed by tensile property tests. Raman spectroscopy demonstrated that MA2-CySS perming better preserves hair keratin’s secondary structure, maintaining superior α-helix content at 27.50% versus 24.35%, exhibiting higher disulfide bond retention at 85% versus 72%, and showing gauche–gauche–gauche to trans–gauche–trans conformational conversion at 9% versus 6%. This study demonstrates that repeatable perming via thiol–Michael click reaction represents a significant advancement in perming methodology.

Platycladus orientalis exhibits significant potential as an antioxidant, anti-inflammatory, and hair growth-promoting ingredient, while the low bioavailability of raw Platycladus orientalis leaves extracts limits their further application. In this study, yeast fermentation was employed to prepare Platycladus orientalis Leaves Yeast Fermented Solution (PYFS). Its performance on human dermal papilla cells (HDPCs) was systematically investigated. The optimal fermentation strain was screened using the methyl thiazolyl tetrazolium (MTT) assay, and Saccharomycopsis fibuligera CICC33226 (SF) was identified as the most suitable strain for fermentation. The effects of PYFS on the cell cycle distribution, growth factors, inflammatory factors of HDPCs, as well as its hair growth-promoting mechanism, were investigated. Experiments revealed that after fermentation, the proportion of cells in the G0/G1 phase decreased by 11.09%, while the proportion of cells in the S phase increased by 35.44%. Additionally, the level of the growth factor VEGF increased by 42.34%, while the level of the inflammatory factor TGF-β1 decreased by 23.81%. Moreover, the fermentation process correlates with altered mRNA expression of Wnt/β-catenin pathway-related genes by upregulating the mRNA expression levels of β-catenin, DVL1, and LEF1, and downregulating the mRNA expression level of DKK-1. Finally, non-targeted metabolomics technology was used to analyze the metabolite changes after fermentation. The most significant differential metabolites mainly include flavonoids, amino acids and their derivatives, and organic acids and their derivatives. This study utilized microbial fermentation technology to prepare the yeast fermentation solution, selected the optimal fermentation strain, and demonstrated that its fermentation product significantly promotes HDPC metabolic activity, supports hair follicle health by regulating the balance of growth factors, alters expression patterns of Wnt/β-catenin pathway-related genes, and substantially alters the metabolite composition of Platycladus orientalis leaves extract through fermentation.