Abstract<\/h3>\n\n\n\n
Hair cosmetics are undergoing a transition from conventional formulations based on passive surface deposition toward biotechnology-driven systems designed to interact with hair and scalp at the molecular level. Recent advances in proteins, peptides, biobased polymers, and responsive delivery platforms are enabling targeted repair of keratin damage, controlled reshaping, durable protection, and modulation of follicular activity. These technologies exploit biological specificity, renewable feedstocks, and programmable material properties to address limitations associated with traditional petrochemical ingredients. In this review, we examine how biotechnology is emerging as a unifying platform for hair cosmetic science, integrating biomolecular engineering, smart materials, computational design, and artificial intelligence to create more effective, sustainable, and biologically inspired hair-care solutions.<\/p>\n\n\n
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<\/a>Driving from traditional formulations to molecular engineering<\/h3>\n\n\n\n
The importance of adopting biotechnology as a platform for hair science lies in its ability to move beyond generic surface coatings toward precision molecular engineering<\/strong> (see Glossary<\/a>) [1,2]<\/a>. By viewing hair fibers as complex biological materials (Box 1<\/a>), researchers are developing hair-care ingredients that can stabilize and repair specific areas of damage at the molecular level of the fiber. These \u2018smart\u2019 systems respond to environmental stimuli and utilize sustainable feedstocks, including lignin and recombinant proteins<\/strong> such as collagen, to outperform synthetic alternatives [5\u20137]<\/a>. This review defines the scope of this platform across two targets: the nonliving fiber and the living follicle. We evaluate how biobased actives revolutionize fiber mechanical properties and protection (Figure 1<\/a>, Key figure), while exploring how follicular modulation creates a critical link between cosmetic appearance and regenerative hair health.<\/p>\n\n\n Hair cosmetics have historically been formulated around macroscopic outcomes such as softness, combability, shine, curl retention, and frizz control, delivered mainly through surfactant cleansing and deposition of active agents. Biotechnology reframes this paradigm by treating the hair fiber as a hierarchically organized keratin<\/strong>-based composite whose performance can be improved by controlling interactions at multiple length scales: molecular binding to keratin, nanoscale organization of deposited layers, and macromolecular film formation that resists wash-off and mechanical wear [3,4]<\/a>. A prerequisite for this shift is a physicochemical view of hair damage and degradation caused by different cosmetic procedures and environmental exposure (Box 2<\/a>) that covers oxidative and alkaline chemistry, heat\/UV exposure, mechanical fatigue, and how these stressors remodel the cuticle\/cortex system and its reactive sites [4]<\/a>. Within this framework, fiber functionalization becomes less about generic coating and more about engineering interfacial chemistry: what binds, where it binds, how it assembles, and how long it remains functional. The studies highlighted below collectively illustrate how peptides, proteins, biobased polymer<\/strong> systems, and polysaccharides can be used as instruments to move from passive deposition to rationally designed performance.<\/p>\n\n\n A central challenge in hair cosmetic science is the restoration of keratin organization following chemical, thermal, and environmental damage. Traditional conditioning approaches primarily mask damage through surface deposition, whereas biotechnology-based solutions enable the development of macromolecular protein platforms that interact directly with the keratin matrix, offering opportunities for structural reinforcement and functional repair [8,9]<\/a>. These systems exploit the inherent compatibility between protein-based materials and the protein-rich architecture of hair, enabling more targeted and durable interventions.<\/p>\n\n\n\n An early example of this strategy was provided by Basit and colleagues [9]<\/a>, who employed recombinant human keratin K31 to improve hair health and reshaping performance. Because keratin is the primary structural component of the hair fiber, recombinant K31 offers intrinsic molecular compatibility with the hair fiber chemical structure, enabling direct interaction with the damaged keratin matrix. The topical application of intact, refolded recombinant K31 targets the ultra-structural deficits in the hair fiber caused by aggressive cosmetic procedures, establishing a cohesive protective film that fills the resulting gaps. This protein also integrates directly into the intermediate filaments of the hair cortex by forming new disulfide linkages with damaged native keratins, successfully rebuilding the hair\u2019s protein matrix and improving hair tensile strength, reducing fiber breakage, and enhancing overall mechanical integrity. Notably, recombinant K31 was also effective in supporting hair reshaping, allowing hair straightening, while studies also demonstrate the protective value of integral silk proteins (fibroin and sericin) during bleaching and coloring protocols. When incorporated into these chemical processes, the silk-protein treatment increased fiber resistance to breakage, indicating improved mechanical robustness under oxidative stress. Beyond mechanical properties, treated, colored swatches showed higher luster during early wash cycles, consistent with improved surface optical performance. Fibroin, a biocompatible, semicrystalline protein, utilizes its highly organized \u03b2-sheet molecular conformation to provide mechanical reinforcement to the hair cortex. By contrast, sericin shows a high affinity for hair keratin and has strong inherent adhesive properties, assembling into a cohesive, transparent protective film over the fiber surface. This biopolymeric film seals open scales, smooths out irregular morphology, and drastically reduces the size and quantity of loose cuticular fragments. The more regular morphology of the fibers\u2019 cuticle surfaces was demonstrated by scanning electron microscopy. These results position silk proteins as macromolecular ingredients that can simultaneously support structural protection and surface quality in chemically stressed hair [8]<\/a>.<\/p>\n\n\n\n To broaden the landscape of available protein feedstocks, Elkady and colleagues [10]<\/a> characterized and formulated Spirulina platensis<\/em> proteins as functional hair-care ingredients, evaluating their effects on natural hair fibers. S. platensis<\/em> proteins improved the fibers\u2019 cuticle integrity and surface morphology, yielding a smoother hair surface with reduced roughness. Analysis of the treated hair samples revealed shifts in keratin-related vibrational bands and enriched \u03b2-sheet structural signatures as determined by spectroscopic readouts, while thermal analyses supported improved moisture retention and enhanced keratin stability. These data position proteins derived from S. platensis<\/em> as promising, renewable ingredients to be included in hair fiber repair and protection formulations [10]<\/a>.<\/p>\n\n\n\n At the molecular level, protein-based hair treatments are also governed by the fiber\u2019s redox state, which can influence polypeptides’ performance. Carvalho and colleagues [11]<\/a> demonstrated that reducing environments, typically found in perming or straightening procedures, alter adsorption and interaction patterns within the keratin network based on protein molecular weight and cysteine content. Higher molecular weight and cysteine-rich proteins, such as hydrolyzed keratin and the recombinant \u03b2-keratin from Gallus gallus<\/em> (BSK), preferentially reinforce the mechanical properties of hair under reducing conditions. Conversely, smaller, low-cysteine molecules do not necessarily benefit from such environments, suggesting that biotechnological design must align protein architecture with specific chemical environments to optimize the structural repair of fibers [11]<\/a>.<\/p>\n\n\n\n Collectively, these studies illustrate a shift from passive deposition toward modular protein platforms designed to interact with, stabilize, and reinforce the keratin matrix. By combining molecular compatibility, renewable sourcing, and tunable functionality, protein-based systems are emerging as key biotechnology tools for next-generation hair repair and protection.<\/p>\n\n\n\n …<\/p>\n\n\n\n<\/a>Advanced biomaterials for fiber engineering: proteins, peptides, and biobased polymers<\/h3>\n\n\n\n
<\/a>Macromolecular protein platforms: modular repair of the keratin matrix<\/h3>\n\n\n\n