What Are Silk Fibroin and Sericin?
Silk fibroin is the primary structural component of natural silk, accounting for approximately 65–85% of the total silk weight. It is a fibrous protein with a semi-crystalline structure, composed of a heavy chain, a light chain, and a glycoprotein component. Its repetitive amino acid sequences form stable beta-sheet structures, which provide silk with high mechanical strength, rigidity, and thermal stability. Silk fibroin is chemically stable and insoluble in common solvents, making it the key contributor to silk's durability.
Sericin is a globular glycoprotein that surrounds silk fibroin fibers and represents about 15–35% of silk. It is rich in hydrophilic functional groups, offering excellent water solubility and adhesion properties. Sericin mainly acts as a natural binder, holding fibroin fibers together and maintaining the integrity of the cocoon structure.
Core Differences Between Silk Fibroin and Sericin
The fundamental differences between silk fibroin and sericin are reflected in three key aspects.
First, structural characteristics differ significantly. Silk fibroin exhibits a fibrous, semi-crystalline structure dominated by beta-sheet crystalline regions, while sericin shows a non-crystalline, globular structure with predominantly random coil conformations.
Second, their physicochemical properties are distinct. Silk fibroin demonstrates excellent mechanical strength, high tensile resistance, and strong chemical stability. In contrast, sericin is highly hydrophilic, readily soluble in water, and exhibits lower mechanical strength.
Third, there is a clear difference in composition proportion and purity. Silk fibroin constitutes the majority of silk and determines its mechanical performance, whereas sericin is present in smaller amounts and contains most of the impurities and soluble components in raw silk.
Differences in Application Fields
Due to its outstanding biocompatibility, biodegradability, and mechanical performance, silk fibroin is widely used in biomedical materials, including artificial skin, hernia repair meshes, and tissue regeneration scaffolds. It is also applied in high-end textiles and functional skincare formulations.
Sericin, benefiting from its strong hydrophilicity, film-forming ability, and mild antibacterial activity, is mainly used in personal care and cosmetic products, such as creams and serums, as well as in food processing and wound care materials. Its properties related to cholesterol reduction and wound healing support also highlight its potential value as a pharmaceutical raw material.