Beneath the Skin: Protein- and Peptide-Based Actives in Skincare and Aesthetic Medicine
Beneath the Skin: Protein- and Peptide-Based Actives in Skincare and Aesthetic Medicine
Skin covers the vast majority of the human body surface and performs essential functions including barrier defense, immune surveillance, regulation of temperature and fluid homeostasis, and sensory perception. The mechanical properties and visible phenotype of skin are determined by a multilayer architecture in which protein networks constitute a central material basis: stratum corneum structural proteins, together with the intercellular lipid lamellae, form a low-permeability barrier; dermal extracellular matrix (ECM) proteins (dominated by collagens) and the elastic system provide a load-bearing and recoil-capable mechanical scaffold; and signaling proteins and functional peptides regulate the behavior of keratinocytes, fibroblasts, immune cells, and vascular endothelial cells via receptor-mediated signal transduction, thereby influencing inflammation resolution, collagen production, and tissue remodeling. This content is intended solely for scientific research and formulation/materials technical exchange. The proteins, peptides, and related materials mentioned herein are presented for research purposes only and are not intended to serve as a basis for use as drugs, medical devices, or for any clinical/aesthetic medical applications; no clinical claims are made regarding any injection, treatment, or efficacy.
Keywords: skin barrier; collagen; extracellular matrix; photoaging; growth factors; functional peptides; botulinum toxin type A; collagen fillers; tissue remodeling; protein purification
I. Structural Basis Linking Cutaneous Protein Systems to Visible Phenotypes
1.1 Epidermal Barrier Proteins and Stratum Corneum Homeostasis
The stratum corneum is formed through terminal differentiation of keratinocytes and is the principal structure controlling transepidermal water loss and resisting external stressors. Barrier homeostasis depends on ordered expression and crosslinking of stratum corneum–associated structural proteins, as well as the continuity and lamellar organization of intercellular lipids. Dysregulation of barrier proteins and related enzymatic systems can increase transepidermal water loss, intensify surface roughness and tightness, and lower thresholds for irritant and sensitivity responses. Such disturbances may also initiate or amplify a pro-inflammatory microenvironment, which can further impair dermal remodeling efficiency and slow recovery of visible appearance.
1.2 Dermal Extracellular Matrix Proteins: Collagen and Elastic Networks
Dermal mechanics are primarily determined by the combined contribution of collagen fibers and elastic fibers. Collagen proteins form triple-helical structures that assemble into fibrillar bundles and serve as the main source of tensile strength; elastin and the microfibrillar system provide resilience and recovery from deformation. Clinically observable firmness, elasticity, and wrinkle depth generally correlate with collagen fiber abundance, degree of alignment, crosslinking state, and the integrity of the elastic system.
1.3 Collagen Homeostasis: Coupled Synthesis–Degradation–Remodeling
Collagen homeostasis is governed by the coupling of three process classes:
(1) Synthesis
Fibroblasts produce collagen precursors and complete secretion, assembly, and maturation; these processes are regulated by multiple signaling pathways and may be upregulated during repair.
(2) Degradation
Matrix metalloproteinases and related protease systems participate in degradation of collagen and other ECM components. Inflammatory mediators and oxidative stress can upregulate protease expression and alter the ECM microenvironment.
(3) Remodeling
Fiber organization, crosslink density, and interactions with proteoglycans and other matrix components determine ECM structural quality and mechanical performance. The direction and rate of remodeling directly shape the stability of the long-term aesthetic outcome.
Table 1. Key Cutaneous Protein Categories and Functional Relevance
Protein Category | Representative Components | Core Functions | Typical Visible Phenotypes |
Barrier structural proteins | Stratum corneum–associated structural proteins | Barrier formation and homeostasis; control of transepidermal water loss | Dryness, roughness, reduced tolerance, heightened sensitivity |
Extracellular matrix proteins | Collagen, elastin | Tensile strength, elasticity, structural scaffold | Loss of firmness, reduced recoil, fine lines and laxity |
Signaling proteins | Growth factors, cytokines | Repair, proliferation/migration, inflammation resolution | Delayed recovery, inflammatory erythema, uneven skin quality |
Peptide-based actives | Functional peptides, signal peptides | Pathway modulation and matrix support | Changes in fine-line appearance, texture refinement, tone uniformity |
II. How Exogenous Factors Drive “Visible Aging” Through Protein Networks
2.1 Photoaging: Canonical Pathway of Collagen Breakdown and Elastic System Damage
Ultraviolet radiation promotes reactive oxygen species generation and activates inflammation-associated signaling, thereby upregulating multiple matrix-degrading enzymes. The result is collagen fiber fragmentation, disorganization, and loosening of dermal architecture; the elastic system may also exhibit abnormal accumulation or structural rupture. With chronic cumulative exposure, typical manifestations include deeper wrinkles, increased laxity, and coarser texture.
2.2 Oxidative Stress and Chronic Inflammation: Persistent Perturbation of the Remodeling Microenvironment
Oxidative stress can alter membrane structure and receptor signaling efficiency through lipid peroxidation and protein oxidation, while amplifying inflammatory mediator release. This sustains activation of an “inflammation–protease axis,” biasing the ECM toward degradation and reducing the quality of remodeling.
2.3 Glycation and Abnormal Crosslinking: Mechanical Deterioration and Accentuated Skin Topography
Non-enzymatic glycation forms advanced glycation end products on proteins, promoting abnormal collagen crosslinking and increased fibril stiffness. Phenotypically, this is associated with reduced elasticity, more prominent skin lines, and a rougher tactile profile. The process is cumulative and relates to age and metabolic status.
III. Protein Actives in Cosmetic Systems: Growth Factors and Pathway Positioning
3.1 Core Mechanisms of Growth Factors and Receptor Signaling
Growth factors are proteins that bind cell-surface receptors and trigger intracellular signaling cascades, thereby regulating proliferation, migration, differentiation, and matrix production. Major target cell types in skin include keratinocytes (epidermal renewal and barrier repair), fibroblasts (collagen/ECM synthesis and remodeling), endothelial cells (perfusion and repair microenvironment formation), and immune cells (initiation and resolution of inflammation). In skincare-oriented scientific narratives, growth factors are typically positioned as “repair and remodeling support” actives that modulate cellular behavior and tissue homeostasis.
3.2 Common Growth Factors: Target Processes and Aesthetic Directionality
(1) Epidermal growth factor (EGF)
By binding the epidermal growth factor receptor, EGF can support epidermal proliferation and migration processes, aligning mechanistically with epidermal repair and barrier recovery pathways.
(2) Fibroblast growth factors (FGFs; commonly FGF2)
FGFs play important roles in tissue repair, fibroblast activation, and matrix production, supporting dermal structural integrity and optimization of the remodeling milieu.
(3) Transforming growth factor-β (TGF-β; commonly TGF-β1)
TGF-β signaling is central to collagen synthesis and matrix remodeling regulation and participates in structural reconstruction during repair. Scientific positioning emphasizes homeostatic regulation and management of remodeling quality.
(4) Platelet-derived growth factor (PDGF)
PDGF is closely associated with cell migration and tissue reconstruction during repair, informing interpretations related to repair efficiency and reconstruction quality.
(5) Vascular endothelial growth factor (VEGF)
VEGF regulates angiogenesis and perfusion, influencing oxygen supply and metabolic support within repair microenvironments, thereby affecting repair and remodeling dynamics.
(6) Insulin-like growth factor-1 (IGF-1)
IGF-1 is linked to cell growth and tissue renewal signals, influencing keratinocyte and fibroblast behavior and often used to rationalize renewal and recovery pathways.
Table 2. Common Growth Factors and Target Processes
Growth Factor | Primary Processes | Primary Target Cells |
EGF | Epidermal renewal and barrier repair | Keratinocytes |
FGF (e.g., FGF2) | Matrix-supportive production and repair-phase remodeling | Fibroblasts and related cells |
TGF-β (e.g., TGF-β1) | Regulation of collagen synthesis and matrix remodeling | Fibroblasts and related cells |
PDGF | Tissue reconstruction and cell migration | Repair-associated cell populations |
VEGF | Angiogenesis and perfusion regulation | Endothelial cells |
IGF-1 | Tissue renewal and metabolic signaling | Keratinocytes, fibroblasts |
3.3 Engineering Determinants for Topical Protein Actives: Stability and Local Bioavailability
Protein performance is constrained by both the formulation environment and the skin barrier. Engineering control typically focuses on the following critical quality attributes:
(1) Conformational stability and aggregation control
Conformational changes, aggregation, and degradation directly affect receptor binding and functional retention.
(2) Formulation compatibility
pH, ionic strength, metal ions, surfactants, and preservative systems can markedly influence protein stability and availability.
(3) Local bioavailability management
Protease background activity and adsorption losses at the skin surface and within the stratum corneum can reduce effective exposure; actives must remain in a functionally relevant form within the target time window.
(4) Manufacturing consistency
Recombinant expression systems and purification strategies shape impurity profiles and batch-to-batch consistency, which directly influence stability and tolerability.
Table 3. Major Factors Affecting Stability of Topical Proteins/Peptides and Control Strategies
Influencing Factor | Common Risks | Control Direction |
pH and ionic strength | Conformational change, aggregation, precipitation | Define stability window; optimize buffering system |
Metal ions | Catalyzed oxidation, promoted aggregation | Chelation control; set metal-ion limits for inputs |
Surfactants/solvents | Unfolding, interfacial adsorption | System screening; interfacial protection and encapsulation |
Preservative systems | Protein interactions leading to activity loss | Compatibility assessment and substitution strategies |
Temperature and light | Oxidation, deamidation, cleavage | Light protection, low-temperature processing, packaging design |
IV. Peptide Actives in Cosmetic Systems: Classification, Mechanisms, and Representative Molecules
4.1 Major Classes of Functional Peptides
Peptides are short amino-acid sequences with high design flexibility and broad formulation compatibility. In skincare systems, commonly used functional peptides can be categorized by mechanistic route:
(1) Neuro-signaling modulator peptides
Designed to influence neurotransmitter release–associated processes or downstream events, thereby reducing conditions that promote expression-line formation driven by facial muscle activity.
(2) Matrix-support peptides
Intended to induce or support fibroblast upregulation of matrix-related pathways, promoting collagen/ECM production, assembly, and remodeling.
(3) Anti-inflammatory and repair-support peptides
Aimed at reducing inflammatory burden and stabilizing repair microenvironments, mitigating disruption of ECM homeostasis driven by the inflammation–protease axis.
(4) Carrier and structurally modified peptides
Employ modifications (e.g., fatty acylation) to increase lipophilicity and formulation compatibility, or use coordination/complexation to modulate local stability and availability.
4.2 Representative Peptides and Pathway Positioning
(1) Acetyl hexapeptide
Commonly positioned within neuro-signaling modulation, with application narratives focusing on neurotransmitter release and muscle contraction–associated pathways to support management of dynamic line appearance.
(2) Copper tripeptide
Typically present as a peptide–copper complex and positioned within repair support and inflammation-modulation frameworks, with mechanistic linkage to repair microenvironments and ECM homeostasis support.
(3) Palmitoyl pentapeptide
A fatty-acylated peptide; palmitoylation increases lipophilicity and formulation compatibility, and it is frequently incorporated into matrix-support and texture-improvement design frameworks.
Table 4. Functional Peptide Classes and Representative Molecules
Functional Class | Pathway Orientation | Representative Molecules |
Neuro-signaling modulation | Neurotransmitter release–associated processes | Acetyl hexapeptide |
Anti-inflammatory and repair support | Repair microenvironment and inflammation resolution | Copper tripeptide |
Matrix support and compatibility optimization | Matrix-support pathways and formulation compatibility | Palmitoyl pentapeptide |
4.3 Scientific Logic and Evaluation Framework for Peptide Combinations
Peptide combinations are designed to cover multiple nodes, including barrier homeostasis, inflammation resolution, matrix remodeling, and neuro-modulatory signaling, thereby improving adaptability across skin states. Scientific evaluation typically requires alignment across:
(1) Stability evidence
Demonstration of chemical stability and impurity-profile evolution of peptides within the formulation.
(2) Mechanistic evidence
Biological responses consistent with target pathways observed in cellular or tissue models.
(3) Human endpoint evidence
Quantitative assessment of fine lines, roughness, elasticity, and tone uniformity, with consistent interpretation of statistical significance and clinical relevance.
V. Protein Applications in Aesthetic Medicine: Neural Pathway Intervention and Structural Compensation
5.1 Botulinum Toxin Type A: Molecular Basis for Dynamic Wrinkle Management
Botulinum toxin type A is a bacterial protein neurotoxin. When locally injected under stringent dose control, it can block acetylcholine release and reduce contraction intensity of target muscle groups, thereby attenuating the appearance of dynamic rhytides. Key scientific considerations include:
(1) Activity standardization
Dose is managed in activity units to ensure controllability.
(2) Quality control
Sterility assurance, control of impurities and endotoxin, and management of batch consistency.
(3) Clinical risk management
Injection site, depth/plane, dose, and diffusion control define safety boundaries and require standardized technique and procedural governance.
(4) Application spectrum
Beyond aesthetic indications, this protein is used clinically for multiple conditions involving muscle spasticity or glandular secretion.
5.2 Collagen Fillers: Volume Restoration and Tissue Support
Collagen fillers deliver collagen materials into dermal or subcutaneous layers via injection to provide localized volume compensation and tissue support for depressions and folds. Key scientific points include:
(1) Material source and purification
Collagen is commonly extracted from animal skin tissues and purified through multistage processes to reduce contaminating proteins and process residues; purification quality strongly influences tolerability and consistency.
(2) Immunogenicity management
Animal-derived collagen carries a risk of hypersensitivity reactions, requiring appropriate clinical risk assessment and management.
(3) Duration and biodegradation
Exogenous collagen can be gradually degraded by proteases in vivo; persistence depends on material form and inter-individual variability.
(4) Scaffold effects in composite systems
When combined with inert microspheres, the microspheres can provide a relatively stable scaffold after collagen degradation and may promote local collagen deposition and structural filling for longer duration. Long-term risks, including nodules and inflammatory responses, require standardized monitoring and management.
Table 5. Key Differences Between Topical Protein/Peptide Actives and Injectable Proteins/Fillers
Dimension | Topical Proteins/Peptides (Cosmetics) | Injectable Proteins/Fillers (Aesthetic Medicine) |
Delivery depth | Limited by the stratum corneum barrier | Can reach targeted dermal/subcutaneous planes |
Effect magnitude | Cumulative conditioning and homeostatic support | More direct mechanisms and clearer effect profiles |
QC priorities | Stability, compatibility, batch consistency | Activity standardization; sterility and impurity control; higher consistency requirements |
Risk management focus | Irritation and tolerability | Site- and dose-related risk; complication management |
Evaluation system | Mechanistic evidence combined with human endpoints | Higher requirements for clinical evidence and standardized practice |
VI. Preparation and Quality Control Considerations for Protein- and Peptide-Based Actives
6.1 Recombinant Protein Production Routes and Critical Quality Attributes
Skincare-related protein actives are frequently obtained as recombinant proteins. Functional performance is tightly linked to critical quality attributes, including:
(1) Conformational integrity and structural stability
Maintenance of secondary/tertiary structure determines receptor binding and signaling efficiency.
(2) Aggregate fraction and soluble state
Aggregates can reduce activity and negatively affect tolerability.
(3) Degradation fragments and impurity profiles
Degradation and impurities change the effective content and may introduce irritation risk.
(4) Endotoxin and microbiological control
These directly influence tolerability and safety, especially for sensitive applications.
6.2 Purification/Separation and Analytical Characterization Frameworks
Protein purification commonly leverages differences in molecular size, solubility, and charge to achieve separation, using multistage processes to reduce host proteins, endotoxin, and process residues. Analytical characterization is conducted to systematically evaluate purity, structural stability, aggregation state, and activity retention. For peptide raw materials, emphasis is placed on sequence purity, isomer content, salt form, and residual solvents to ensure stability and batch consistency.
VII. Aladdin-Related Products
Category | Name | CAS No. | Mechanistic Key Point | Intended Use Direction |
Structural protein | Collagen | Core dermal ECM scaffold; provides tensile strength and structural support | Firmness; fine lines/wrinkles; support/“plumpness” appearance | |
Structural protein | Elastin | Key component of the elastic fiber system; supports recoil and shape recovery | Elasticity; laxity; texture roughness | |
Structural protein (derivative) | Gelatin | Collagen-derived; film-forming and moisturization/sensory support | Smoothness; refined skin feel; dryness/roughness | |
Signaling protein | Epidermal Growth Factor (EGF) | EGFR-mediated signaling supports epidermal proliferation/migration and barrier repair | Recovery support; barrier restoration; sensitive-skin care narrative | |
Signaling protein | Insulin-like Growth Factor 1 (IGF-1) | Growth/metabolic signaling influencing renewal and repair-associated processes | Renewal support; recovery support; texture improvement | |
Peptide (neuromodulatory) | Acetyl Hexapeptide-8 | Cosmetic narrative: modulation of neurotransmitter-release–related pathways | Dynamic/expression line appearance support | |
Peptide (neuromodulatory) | Acetyl Octapeptide-3 | Cosmetic narrative: enhanced neurosignal modulation | Expression lines; dynamic line appearance support | |
Peptide (ECM support) | Palmitoyl Pentapeptide-4 | ECM-production support narrative; upregulates collagen-related pathways | Fine lines; firmness; refined texture | |
Peptide (ECM support) | Palmitoyl Tripeptide-1 | ECM-support narrative; strengthens dermal-support framework | Fine lines; texture; elasticity appearance | |
Peptide (repair/anti-inflammatory) | Palmitoyl Tetrapeptide-7 | Anti-inflammatory and repair-support narrative; reduces inflammation burden | Redness; roughness; tolerance/comfort support | |
Peptide (ECM support) | Palmitoyl Tripeptide-5 | Narrative linked to TGF-β–related “collagen-support” positioning | Firmness; fine lines; texture refinement | |
Injectable material (protein-based) | Collagen (injectable grade, conceptually same) | Volume replacement and structural support via injection delivery | Depressions/folds; support and contour improvement |
The structural basis of skin function and appearance resides in protein networks, particularly the mechanical scaffold and remodeling capacity provided by dermal collagen and the elastic system. Growth factors regulate epidermal repair, fibroblast behavior, and ECM homeostasis through receptor-level signaling; functional peptides, with greater design flexibility and formulation compatibility, serve as pathway modulators and repair-support elements; and in aesthetic medicine, botulinum toxin type A and collagen fillers achieve dynamic wrinkle management and volume support through deeper delivery and more direct mechanistic routes. For protein- and peptide-based systems, manufacturing processes, purification quality, and formulation engineering jointly determine stability, tolerability, and functional reproducibility. Distinct delivery modalities correspond to distinct safety boundaries and evidence requirements, and R&D and application should be conducted within a rigorous scientific framework.
References
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