Sericin

Other Names

Bombyx mori SericinHydrolyzed SericinNative SericinSeracinSericin ASericin HydrolysateSericin ProteinSericin USP/EP/BPSilk Degumming ProteinSilk GlueSilk GumSilk ProteinSilk SericinSilkworm Sericin

Synopsis

Sericin: A Comprehensive Encyclopedic Reference

1. Identity

1.1 Nomenclature and Chemical Classification

Sericin is a protein created by Bombyx mori (silkworms) in the production of silk. Silk sericin is a class of protein biopolymers produced by silkworms. The word "sericin" is derived from the Latin sericum, meaning silk. Sericin is characterized chemically as a globular protein, distinct from the fibrous structure of fibroin, and is composed of 18 different amino acids. It belongs to the broader family of silk proteins (sericoproteins) and is sometimes referred to in scientific literature as "silk sericin," "silk glue protein," or, when enzymatically broken down, as "sericin hydrolysate" or "sericin-derived oligopeptides" (SDOs).

1.2 Natural Source and Biological Origin

Silk is a fibre produced by the silkworm in production of its cocoon. It consists mainly of two proteins, fibroin and sericin. Silk consists of 70–80% fibroin and 20–30% sericin; fibroin being the structural center of the silk, and sericin being the gum coating the fibres and allowing them to stick to each other. Fibroin is secreted in the posterior part of the silk gland while sericin is from the middle part.

Although Bombyx mori is the predominant commercial source, sericin is also produced by other silkworm species. Silk from species such as Antheraea assamensis, Philosamia ricini, and other wild silk moths also contains sericin, and studies have documented bioactivity differences across species. According to historical data, silk farming is acknowledged as one of the most ancient agricultural findings. The silk is generally composed of 75–83% fibroin, 17–25% sericin, and 1–5% non-sericin components, including secondary metabolites, wax, pigments, carbohydrates, and other impurities.

It is estimated that out of approximately 1 million tons of globally produced fresh cocoons, roughly 400,000 tons of dry cocoons are achieved, yielding 50,000 tons of sericin. Since 2010, the annual output of silkworm cocoons in China alone has exceeded 600,000 tons, accounting for about 70% of the total global output. During the production of cocoon silk, about 40,000 to 50,000 tons of sericin globally are discharged in alkaline liquid waste every year.

1.3 Structural Layers of Sericin

Sericin A, which is insoluble in water, is the outermost layer, and contains approximately 17% nitrogen, along with amino acids such as serine, threonine, aspartic acid, and glycine. Sericin B, composing the middle layer, is nearly the same as sericin A, but also contains tryptophan. Five different fractions of sericin have been isolated, with glycoproteins having a range of molecular weights (65–400 kilodalton) and other smaller fractions.

1.4 Common Forms and Preparations

Sericin is available in several commercial and research-grade forms:

Aqueous solution: Sericin dissolved in water following hot-water or autoclave extraction, used directly in cosmetic and cell-culture applications.
Lyophilized (freeze-dried) powder: The sericin extract is filtered and desalted, then concentrated and lyophilized to obtain powdery sericin hydrolysate at a purity of greater than 90%.
Sericin hydrolysate: Produced by enzymatic, acid, alkaline, or thermal degradation of intact sericin, yielding peptides of lower molecular weight with altered bioactivity profiles.
Sericin-derived oligopeptides (SDOs): Beginning with sericin from yellow silk cocoons, the procedure can be expanded to pilot scale while preserving quality. Through ultrafiltration and size exclusion chromatography, the most potent peptide fractions with molecular weights <3 kDa can be isolated, showing optimal DPP-IV and ACE inhibitory activities.
Hydrogels, films, and scaffolds: Given the versatility and outstanding properties of sericin, it is widely fabricated to produce sponges, films, and hydrogels for further use in diverse biomedical applications.
Topical creams and wound dressings: Sericin has been incorporated into silver sulfadiazine creams, polyvinyl alcohol scaffolds, and hydrogel formulations for wound care.

2. Traditional and Historical Use

2.1 History of Sericulture

Regarding historical data gleaned from North China, since 5,000 years dating back, commercial silk farming has been put forth as one of humanity's most ancient agricultural findings. Besides, silk has been abundantly used traditionally in diverse cultures as a natural therapy or yarn-related trade. Traditional Asian medicine has inspired many studies, being a rich source of ideas in exploring new bioactive compounds.

In the context of traditional sericulture, sericin itself was not historically isolated and administered as a purified supplement. Rather, the whole silk cocoon — fibroin, sericin, and associated secondary metabolites — was used medicinally. Silk cocoon, naturally produced by silkworms scientifically named Bombyx mori L. (Lepidoptera, Bombycidae), is one of the well-known medicinal agents with several therapeutic activities.

2.2 Ethnopharmacological Uses

Silk peptides, worms, or even pupae are commonly employed in traditional Asian medicine with a wide variety of purposes, and some scientific work has been focused on their antidiabetic properties.

The silkworm A. assamensis and Bombyx mori have been used for the treatment of sore throat and the P. ricinii silkworms have been applied for the treatment of infections of the mouth and tongue in young children by different ethnic peoples in the northeast region of India.

In China, sericulture products are exploited considerably. Historical Chinese pharmacopeias documented the use of silkworm cocoons for conditions including fever, bleeding, and metabolic complaints, though these references pertain to whole-cocoon preparations rather than isolated sericin. Sericin was neglected for years; to prepare smooth, soft, and lustrous silk filaments from silkworms' cocoons for the textile industry, sericin is removed from fibroin in the so-called "degumming" or "refining" process. As a consequence of this industrial discarding of sericin, its targeted therapeutic use as an isolated compound is largely a modern development.

2.3 Industrial History and the Shift to Purposeful Use

Historically, this protein was regarded as a waste byproduct, dissolved and discarded during the textile preparation process known as degumming. Modern scientific investigation has revealed the molecule's unique chemical structure and biological properties, leading to a resurgence of interest in its potential for high-value applications. Sericulture represents a significant role in human health by providing functional food supplements.

3. Key Constituents and Chemical Composition

3.1 Amino Acid Profile

Sericin is composed of 18 different amino acids, of which 32% is serine. Sericin is characterized chemically as a globular protein composed of 18 different amino acids. Its defining feature is an extremely high concentration of polar amino acids, accounting for up to 75% of its side chains.

The dominant amino acids, as determined by HPLC analysis, include:

Serine: The most abundant residue. Serine is the most abundant, often comprising over 30% of the total amino acid content, which is the source of the name "sericin."
Glycine: Sericin contains a large amount of glycine (23.20%), serine (21.56%), aspartic acid (14.00%), and arginine (11.95%).
Aspartic acid, threonine, and tyrosine are also consistently prominent. Sericin comprises a variable amino acid composition such as serine, glycine, glutamic acid, aspartic acid, threonine, and tyrosine.

This unique composition, particularly the numerous hydroxyl and carboxyl groups, imparts a strongly hydrophilic nature to sericin. The secondary structure is usually a random coil, but it can also be easily converted into a β-sheet conformation, via repeated moisture absorption and mechanical stretching. The serine hydrogen bonds give its glue-like quality.

A large part of this protein is very stable, thanks to the presence of beta-sheets formed by hydrogen bonds between polar amino acids. 35% of its structure is characterized by beta-sheets. For the remainder, 63% of the structure consists of random spirals, while a small percentage of the structure is alpha-helices.

3.2 Molecular Weight Variability

Studies have shown that the extracted sericin has a molecular weight between 10 and 400 kDa. During the extraction process, sericin is hydrolyzed to different degrees; different extraction methods involve different degrees of hydrolysis, and its stability, molecular weight, sericin conformation, and biological activities also vary. This variability has direct consequences for bioactivity: the resulting sericins have large differences in molecular weight distribution, resulting in large differences in biological activities, especially antioxidant activities.

3.3 Associated Secondary Metabolites

Flavonoids, especially quercetin and kaempferol, alkaloids, coumarin derivatives, and phenolic acids, are among the secondary metabolites isolated from the silk cocoon. These compounds co-occur with sericin in whole-cocoon preparations and may contribute to the observed bioactivities of crude extracts, a factor not always distinguished in research.

4. Extraction Methods

Silk sericin can be obtained using numerous methods, including enzymatic extraction, high-temperature, autoclaving, ethanol precipitation, cross-linking, and utilizing acidic, alkali, or neutral aqueous solutions.

Hot water / autoclaving: Traditionally, this is achieved by boiling the cocoons in hot water or by using alkaline agents such as sodium carbonate or acids. While effective, these harsh methods can degrade the sericin protein, resulting in lower molecular weight and variable properties.
Alkaline extraction: Treatment with dilute sodium carbonate is widely used industrially. The degree of alkalinity and temperature determine the extent of hydrolysis.
Urea extraction: Sericin extracted by urea solution, with molecular weight ranging from 10 to 225 kDa, has had the highest retention of certain biological activities in comparative studies.
Enzymatic hydrolysis: Use of proteases (e.g., Neutrase, trypsin, Alcalase) yields oligopeptide fractions with enhanced bioactivity and defined molecular weight.
Temperature optimization: Higher temperatures (125°C) produced the maximum sericin yield, while moderate conditions (115°C for 45 min) ensured better preservation of antioxidant and antidiabetic activities.

The recovery and reuse of sericin usually discarded by the textile industry not only minimizes environmental issues but also has high scientific and commercial value. The physicochemical properties of the molecule are responsible for numerous applications in biomedicine and are influenced by the extraction method and silkworm lineage, which can lead to variations in molecular weight and amino acid concentration of sericin.

5. Mechanisms of Action

5.1 Antioxidant Activity

The antioxidant activity of silk sericin is considered a fundamental property, which could account for partial biological activities, despite the exact mechanisms of silk sericin's effect remaining unknown. The large number of polar groups in sericin and their special structure result in it having several different biological properties. The high serine content, with its hydroxyl side chains, is believed to confer strong free-radical scavenging capacity. Studies using trypsin hydrolysates have shown: at the concentration of 3.2 mg/mL for each type of hydrolysate, more than 65% of DPPH free radicals and 90% of ABTS free radicals were cleaned.

Results indicate that both sericins, regardless of molecular size, have significantly enhanced antioxidant, superoxide free radical scavenging, and glycosidase inhibitory activities after simulated metabolism, and that lower molecular weight sericin is better than higher molecular weight sericin regardless of simulated digestion.

5.2 Tyrosinase Inhibition

A study in Japan demonstrated that sericin inhibits tyrosinase activity in silk. The anti-tyrosinase activity of sericin hydrolysate is thought to be linked to copper chelating properties and high serine content. The relationship between copper chelating activity and tyrosinase inhibition is well established. Tyrosinase is the rate-limiting enzyme in melanin biosynthesis; its inhibition by sericin constitutes the primary mechanism behind sericin's depigmenting and anti-hyperpigmentation properties.

5.3 Insulin-Signaling Pathway Modulation

Sericin may enhance the signaling transduction effect of insulin by upregulating the expression levels of key factors (IR, IRS-1, PI3K and AKT) in the liver insulin-PI3K/AKT signaling pathway, thus promoting glucose transport and liver glycogen synthesis, and further reducing blood glucose.

The protein significantly decreased fasting blood glucose, fasting plasma insulin, and glycosylated serum protein levels; improved oral glucose tolerance and insulin tolerance, and enhanced antioxidative activities. It enhanced the expression of key proteins and enzymes, including insulin receptor, insulin receptor substrate, PI3K, phosphorylated-AKT, hepatic kinase, GLUT4, glycogen synthase, GSK3β, GLK, PFK1, PKM2, and AMPKα, which are related to insulin metabolism and glycolysis.

5.4 Cholesterol and Lipid Metabolism

Sericin-derived oligopeptides (SDO) dose-dependently reduced cholesterol solubility in lipid micelles and inhibited cholesterol uptake in monolayer Caco-2 cells. SDO also effectively bound to all three types of bile salts including taurocholate, deoxytaurocholate, and glycodeoxycholate. Direct interaction with bile acids of SDO may disrupt micellar cholesterol solubility, and subsequently reduce the absorption of dietary cholesterol in intestines.

5.5 α-Glucosidase Inhibition

The α-glucosidase inhibition rates of 10 mg/mL outer sericin and whole sericin reached 65.62% and 51.3%, respectively. α-Glucosidase inhibition delays the breakdown and absorption of dietary carbohydrates, a mechanism shared with anti-diabetic drugs such as acarbose.

5.6 Resistance to Gastrointestinal Proteolysis

Sericin is protease-resistant and thus relatively resistant to proteolysis in the gastrointestinal tract, and this explains why it is capable of protecting against 1,2-dimethylhydrazine induced colon tumorigenesis in animals. This partial resistance allows intact or minimally degraded sericin to reach the colon, where it may exert local antioxidant effects.

5.7 Cell Proliferation and Mitogenic Activity

Sericin is biocompatible and naturally cell adhesive, enabling cell attachment, proliferation, and differentiation in sericin-based materials. It has the ability to improve cell proliferation when used as a supplement in cell culture media of human epithelial cells, human embryonic kidney transformed cells, human hepatoblastoma cells, and murine hybridoma cells.

6. Scientific Evidence by Area of Use

6.1 Antioxidant and Oxidative Stress Reduction

Preclinical evidence: The antioxidant properties of sericin have been documented across numerous animal and in vitro models. Oxidative stress markers and antioxidant enzyme levels were determined in wound-healing rat studies. MDA (malonyldialdehyde), an oxidative stress marker, was significantly lower in the sericin group than in placebo and sham-operated groups (p<0.001). GPx (Glutathione Peroxidase), SOD (Superoxide Dismutase), and catalase, which are important antioxidant defense enzymes, were significantly higher in the sericin group than in the sham operated group and the placebo group (p<0.001).

Experiments were conducted in 30 rats divided into five groups: normal control, high cholesterol fed (HCF), HCF + fenofibrate, HCF + sericin 0.25 gm/kg b.w./day, and HCF + sericin 0.5 gm/kg b.w./day. Administration of low and high dose sericin exhibited good antioxidant activity by reducing the TBARS level and increasing endogenous antioxidant in peripheral tissue. In addition, a histological examination revealed loss of normal liver and kidney architecture in cholesterol-fed rats which were retained in sericin-treated groups.

Evidence strength: Antioxidant activity is well-documented in cell cultures and animal models. No controlled human clinical trials specifically examining sericin's systemic antioxidant effects have been reported in the peer-reviewed literature.

6.2 Wound Healing

Preclinical evidence: Sericin is a potent antioxidant that aids in wound healing by promoting keratinocyte and fibroblast proliferation and collagen production. It can be used as a wound dressing or cream to control infection, treat burns, reduce scarring, and prevent infection. Sericin-containing substances can prevent prolonged inflammation in chronic wounds and accelerate healing by turning the healing process into a proliferative phase.

Sericin is presently studied for biomedical applications, especially for promoting collagen production, which is important in wound healing in the skin and accelerating osteogenesis in the bone healing process.

Human/clinical evidence: One notable prospective clinical study has been published. The aim of this study was to evaluate the effect of silk sericin, a protein from silkworm cocoon, on scratch wound healing in vitro. For applicable result in clinical use, researchers also studied the efficacy of sericin added to a standard antimicrobial cream, silver zinc sulfadiazine, for open wound care in the treatment of second-degree burn wounds. In vitro scratch assays showed that sericin at a concentration of 100 μg/mL can promote the migration of fibroblast L929 cells similar to epidermal growth factor (positive control) at 100 μg/mL. After 1 day of treatment, the length of scratch in wounds treated with sericin was significantly shorter than the length of negative control wounds. For the clinical study, a total of 29 patients with 65 burn wounds were randomly assigned to either control or treatment. The results showed that the average time to reach 70% re-epithelialization of the burned surface and complete healing in the treatment group was significantly shorter, approximately 5–7 days, than in the control group. Control wounds took approximately 29.28 ± 9.27 days, while wounds treated with silver zinc sulfadiazine with added sericin cream took approximately 22.42 ± 6.33 days (p = 0.001). No infection or severe reaction was found in any wounds. This is the first clinical study to show that silk sericin is safe and beneficial for burn wound treatment when it is added to silver sulfadiazine cream.

A clinical evaluation of a sericin/polyvinyl alcohol wound dressing scaffold was also conducted. Siritientong et al. tested the clinical potential of an ethyl alcohol-precipitated silk sericin/polyvinyl alcohol scaffold as a wound dressing, in comparison with Bactigras®, a commercially available wound dressing. The sericin biomaterial possesses appropriate properties and can be applied with safety and high efficacy compared to Bactigras. The clinical evaluation revealed no evidence of skin irritation, demonstrated accelerated healing, and reduced pain compared with wounds treated with Bactigras.

Evidence strength: Moderate for topical wound healing — supported by limited but positive human clinical data (small RCT of 29 patients) and strong preclinical data. These positive effects of sericin in wound healing must be evaluated in further human clinical studies.

6.3 Glycemic Control and Antidiabetic Activity

Preclinical evidence: Glycemic effects of sericin have been investigated extensively in animal models, primarily streptozotocin-induced type 2 diabetic rodents. After oral sericin administration for four weeks, fasting blood glucose was significantly reduced, especially in medium- and high-dose sericin groups, for which the blood glucose reduction rates were 62.3 and 67.1%, respectively. The observed decrease in glycosylated serum protein levels was also dose-dependent. Serum insulin levels were significantly reduced, insulin resistance decreased, and insulin sensitivity increased, indicating that sericin could enhance the effects of insulin on glucose absorption and utilization.

Okazaki et al. reported that sericin added to the diet at 4% (g%) level could decrease serum lipids, improve glucose tolerance, and enhance serum adiponectin in rats fed a high-fat diet.

Sericin samples with different molecular weights were tested on rats with nutritional hyperglycemia. When sericin containing free amino acids with a molecular weight of (5–6) × 10³, was administered at a dose of 65 mg/kg twice a day, a decrease of 159.5% in blood sugar levels in the rats was registered after 30 days compared to the control group.

The postprandial antihyperglycemic activity of fibroin, sericin, and powder made from pupae of silkworms is confirmed in silkworm-model studies designed to mirror glucose metabolism.

The protein also reduced the expression of G6Pase, PCK, and ACC, which are related to gluconeogenesis and lipid metabolism in the liver, and decreased the expression of TNF-α, IL-6, P65, and IKKβ related to inflammation. In general, sericin could maintain normal glucose levels and regulate insulin secretion, insulin and lipid metabolism, and inhibition of inflammation.

Evidence strength: Promising but limited to animal studies and in vitro models. No randomized controlled human trials have been published specifically examining oral sericin as an antidiabetic intervention. The preclinical mechanistic data are consistent and multi-pathway, supporting further human investigation.

6.4 Cholesterol and Lipid Lowering

Preclinical evidence: It was reported that dietary sericin lowered the levels of triglycerides (TG) and total cholesterol (TC) in mice fed a high-fat diet. Sericin reduced blood cholesterol without hypoglycemic effect in a high-cholesterol/streptozotocin rat model. Sericin alleviated dysmorphic mitochondria in heart and liver. Sericin has been implicated in lower cholesterolemic effect due to its properties with several mechanisms.

Sericin-derived oligopeptides (SDO) or sericin peptides exhibit a beneficial effect on blood cholesterol levels and could be potentially used as a health-promoting dietary supplement or nutraceutical product.

Increased dosages of sericin supplementation resulted in a significant reduction in triglyceride and plasma glucose levels. All chromium picolinate and chromium picolinate–sericin treatments reduced LDL and total cholesterol while increasing HDL.

Evidence strength: Preclinical only (animal models and Caco-2 cell assays). Human data are absent. The bile-acid binding mechanism described in in vitro models provides a plausible physiological rationale, but clinical translation has not been demonstrated.

6.5 Anticarcinogenic Activity

Preclinical evidence: The most consistently studied anticancer application involves colon cancer prevention. This study was conducted to examine the mechanisms of the anti-colon tumor effect of dietary sericin. Dietary supplementation of 3% sericin reduced colon mucosal lipid peroxide and aberrant crypt foci in 1,2-dimethylhydrazine-treated rats. The colon content from sericin-fed rats had much stronger antioxidant activity compared to that from control rats not receiving sericin. The amino acid composition of undigested proteins in the colon contents from sericin-fed rats was similar to that of sericin ingested. The results suggest that the strong antioxidant activity of undigested sericin in the colon content causes lower oxidative stress and tumorigenesis in the colon.

Sericin peptide has a protective effect against 1,2-dimethylhydrazine and UVB-induced acute damage and tumor promotion in mice by reducing oxidative stress.

In animal model, sericin has been reported to have anti-tumoral action against colon cancer. The mechanisms underlying the activity of sericin against cancer cells are not fully understood. In vitro cell studies have added to the body of evidence: the data support the protective effect of silk sericin against cancer cells of the colon and suggest that this protein may have significant health benefits and could potentially be developed as a dietary supplement for colon cancer prevention.

Sericin showed antiproliferative activity in contact with human tumor cell lines at a minimum concentration of 0.52 mg/mL.

Evidence strength: Preliminary — based on rodent carcinogen-challenge studies and in vitro antiproliferative assays. No human interventional or epidemiological data exist. The evidence is suggestive but far from conclusive for cancer prevention or treatment in humans.

6.6 Skin Depigmentation and Anti-hyperpigmentation

In vitro and preclinical evidence: The anti-tyrosinase and immunomodulatory effects of sericin have been known for decades. The results revealed that urea-extracted sericin has strong anti-tyrosinase properties as shown by a reduction of tyrosinase activity in melanin pigments both 48 h and 10 days after allergic induction.

Urea-extracted sericin reduced the melanin content and cellular tyrosinase activity more effectively than other extraction methods. Interestingly, the potential anti-melanogenic activity was more effective than kojic acid, a depigmenting agent used to treat hyperpigmentation.

Sericin has wound healing properties, protects against ultraviolet (UV) radiation, and exhibits anti-inflammatory, anti-oxidation, and anti-tyrosinase activities. Sericin reduced UVB-induced oxidative damage and hyperpigmentation via the melanogenesis pathway in the B16F10 mouse melanoma cell line.

Evidence strength: Mechanistically coherent in vitro evidence exists. The therapeutic effects of sericin on hyperpigmentation disorders have not been well documented in clinical settings. No published human RCTs on sericin's depigmenting effect in hyperpigmentation conditions have been identified.

6.7 Antimicrobial Activity

Regarding antimicrobial activity, sericin had the capacity to inhibit the growth of bacteria and fungi tested at concentrations between 5 and 10 mg/mL. For its antibacterial activity, sericin from Samia ricini has been reported to affect Escherichia coli and Staphylococcus aureus. Moreover, the potential of biofilm inhibition and disruption activities against Streptococcus mutans has been demonstrated for sericin extracted using urea and autoclaving.

Evidence strength: Preclinical (in vitro) only. The concentrations required for antimicrobial activity (5–10 mg/mL) are substantially higher than those encountered in most topical formulations, and clinical significance has not been established.

6.8 Neuroprotection

Sericin is a natural neuroactive macromolecule with diverse pharmacological properties, and previous findings have shown its neuroprotective potentials. One study aimed to investigate the therapeutic potential of sericin on cognitive dysfunction induced by transient global cerebral ischemia/reperfusion. Mice were treated with normal saline or different doses of sericin (100, 200, and 300 mg/kg) for 10 days after ischemia. Cognitive performances were assessed using the Barnes maze and social interaction tasks.

Previous studies have shown that sericin extracted from silk cocoon significantly reduces blood glucose levels and protects the nervous system against diabetes mellitus. After treatment, the blood glucose levels of the diabetic rats decreased significantly, the growth hormone level in serum and its expression in the hippocampus decreased significantly, while the insulin-like growth factor-1 level in serum and insulin-like growth factor-1 and growth hormone receptor expression in the hippocampus increased significantly.

Sericin has also been shown to enhance cognition in Alzheimer's disease patients according to limited reference data in animal models (the primary literature on this point originates from rodent-model studies). No human RCT data are available for sericin in neurodegenerative conditions.

Evidence strength: Early and preclinical. No human clinical trials examining sericin's neuroprotective effects have been published.

6.9 Liver Protection

High and low molecular weight sericin groups reduced the levels of oxidative stress, inflammation, and tumor necrosis factor, and the latter significantly reduced the levels of TNF-α, interleukin-6, and nuclear factor-κB in AML12 hepatocytes. Additionally, sericin significantly reduced the oxidative stress damage caused by the high-glucose environment.

Oral sericin administration could improve glucose metabolism by reducing blood glucose levels, regulating insulin secretion, and relieving insulin resistance in T2D rats. Lipid metabolism disorder is a clinical symptom of diabetes. The protein could ameliorate the pathological damage in pancreatic β-cells and the liver tissue.

Evidence strength: Hepatoprotective effects demonstrated only in animal models and cell cultures. No human data.

6.10 Anticoagulant / Antithrombotic Activity

Sericin demonstrated its capacity to prolong the coagulation time in pooled human plasma in in vitro studies. This anticoagulant property has been noted in biochemical assays but has not been characterized in human subjects. Due to the unique biological functions including antioxidation, tyrosinase inhibition, anticoagulation, and anticancer activities, sericin peptide and its hydrolysate have been used extensively in many commercial products such as food, pharmacological, and cosmetic goods.

7. Body Systems and Health Areas of Association

Integumentary system (skin): Wound healing, UV protection, anti-hyperpigmentation, antioxidant, moisturization.
Metabolic / endocrine system: Blood glucose regulation, insulin sensitivity, lipid metabolism, cholesterol reduction, adiponectin elevation.
Gastrointestinal system: Colon antioxidant protection, anti-tumorigenesis in carcinogen-challenge animal models, partial resistance to digestion enabling colonic effects.
Cardiovascular system: Lipid lowering, anti-hypercholesterolemia, anticoagulant potential (preclinical).
Nervous system: Neuroprotection in ischemia and diabetic neuropathy models (preclinical).
Hepatic system: Liver protection, reduction of hepatic steatosis, modulation of liver enzymes (preclinical).
Musculoskeletal system: Sericin is studied for promoting collagen production and accelerating osteogenesis in the bone healing process.
Immune / pigmentation system: Immunomodulatory effects in melanocytes and dendritic cells, anti-melanogenic properties.

8. Dosage Forms and Dosages Reported in Studies

Sericin is not regulated as a pharmaceutical drug in most jurisdictions, and no standard therapeutic dosage has been established. The following dosages appear in the peer-reviewed scientific literature and are presented only as reported in those sources:

Dietary supplementation in rat models (antidiabetic): Sericin added to the diet at 4% (g%) level could decrease serum lipids, improve glucose tolerance, and enhance serum adiponectin in rats fed a high-fat diet.
Oral gavage in T2D rats (antidiabetic): Sericin containing free amino acids with a molecular weight of (5–6) × 10³ was administered at a dose of 65 mg/kg twice a day.
Rat models (antioxidant / cholesterol): Sericin was administered at doses of 0.25 gm/kg b.w./day (low dose) and 0.5 gm/kg b.w./day (high dose) in hypercholesterolemic rat groups.
Animal models (neuroprotection / ischemia): Mice were treated with different doses of sericin (100, 200, and 300 mg/kg) for 10 days.
Colon antioxidant study (rat): Dietary supplementation of 3% sericin reduced colon mucosal lipid peroxide and aberrant crypt foci in 1,2-dimethylhydrazine-treated rats.
Sericin combined with chromium picolinate (rat): Rats were administered different doses of sericin (0, 1, 10, and 100 mg/kg body weight) in conjunction with chromium picolinate (300 µg/kg BW) for 8 weeks through oral gavage.
Topical/wound dressing (clinical burn study): Sericin at a concentration of 100 μg/mL was used in in vitro scratch assays. The clinical study used sericin incorporated into silver zinc sulfadiazine cream applied to burn wounds, with the exact sericin concentration in the topical formulation not specified in the abstract.
Patent-cited range for oral use: Sericin or its hydrolysate may be orally administered as medicines. A dose is not particularly critical and it may be administered at a dose of about 10 mg to about 100 g/day.
Antiproliferative (in vitro): Antiproliferative activity was observed in contact with human tumor cell lines at a minimum concentration of 0.52 mg/mL.
Cell proliferation enhancement (in vitro): At a concentration of 0.33 mg/mL, cell viability surpassed 100% compared to the negative control.

The concentration of sericin significantly influences its biological activity, with lower concentrations enhancing cell proliferation, although the precise mechanism behind this remains unclear.

9. Safety Considerations

9.1 General Biocompatibility

Studies have confirmed that sericin has good biocompatibility from the three standpoints of inflammation, allergy, and immunogenicity. Sericin presents characteristics of good biocompatibility, low immunogenicity, inhibition of inflammatory responses, and good immune regulatory function.

Immunogenicity is hardly exhibited in water-soluble silk sericin.

9.2 Allergenicity

Sericin in raw silk acts as a silk allergen and causes contact dermatitis. This observation pertains to raw, non-purified silk preparations. The picture with purified sericin is more nuanced: previously, sericin was associated with childhood asthma, allergenicity, immunogenicity and cytotoxicity, while other research claimed that sericin exhibits mild inflammatory responses, negligible allergenicity, and low immunogenicity in vivo.

Some studies have reported potential allergenic properties of silk proteins, including sericin. A study involving 871 children in China found an association between sensitization to silk and asthma incidence. The Cosmetic Ingredient Review (CIR) panel noted that the reported results are not sufficient to demonstrate a cause-and-effect relationship between silk exposure and asthma. Alternative explanations for the association are plausible.

Moreover, purified sericin has shown low immunogenicity in multiple studies.

9.3 Immunogenicity in Biomedical Applications

Although sericin is generally considered biocompatible, its glycoprotein composition raises potential concerns about immunogenicity, particularly in systemic applications. While reported immune responses are typically mild and not clinically severe, they underscore the need for standardized processing to eliminate residual contaminants and minimize immune activation.

Approaches such as enzymatic deglycosylation, advanced purification methods, and surface modifications (e.g., PEGylation) can further reduce immunogenic risk and improve systemic tolerance. To establish sericin's clinical safety profile, comprehensive in vivo immunogenicity evaluations remain essential.

9.4 Developmental / Reproductive Toxicity (Animal Data)

Previous studies showed that water-extract sericin was of low genotoxicity and subchronic toxicity. A comprehensive toxicological assessment study was aimed to evaluate the potential toxicity of sericin to pregnant rats and their fetus when administered daily by gavage, to provide experimental evidence for safety assessment of sericin-related products in vivo. The treatment groups were administered water-extract sericin solutions at doses of 1,000, 500, and 250 mg/kg. Systemic toxicity and safety assessment of sericin is still rare, and data in pregnant humans are absent.

9.5 Concentration-Dependent Effects

Excessive sericin concentrations can lead to cytotoxicity, protein aggregation, osmotic imbalance, and increased viscosity, all of which may induce oxidative stress. This concentration-dependence is particularly relevant to cell-culture and cryopreservation applications, but the thresholds in human systemic exposure are undefined.

9.6 Quality and Standardization Issues

The quality and the features of sericin are strongly dependent on the extraction and purification methods, which can employ mild conditions to preserve the molecular integrity of the protein or recovery techniques from waste streams produced. Several challenges hinder the widespread commercial application of sericin, such as variability in composition and scalability, which remain key limitations. The lack of standardized production methods means that commercial sericin products may differ substantially in molecular weight, purity, and amino acid composition, with corresponding differences in biological activity and potentially in safety profile.

9.7 Potential Interactions

The existing literature does not document specific drug-drug or supplement-drug interactions for sericin in human studies. However, mechanistic considerations relevant to preclinical findings include:

Antidiabetic medications: Given sericin's documented capacity to lower blood glucose and enhance insulin signaling in animal models, concurrent use with insulin or oral hypoglycemic agents could theoretically potentiate effects. No human interaction data exist.
Anticoagulants: In vitro evidence of anticoagulant activity suggests a theoretical basis for interaction with anticoagulant drugs, though no human data confirm clinical relevance.
Cholesterol-lowering agents: Sericin's proposed bile-acid binding mechanism overlaps with the mechanism of bile-acid sequestrant drugs (e.g., cholestyramine), suggesting potential additive effects. This is speculative in human terms.

10. Current Status, Limitations, and Research Gaps

Increasing attention has been paid to silk sericin for biomedical applications in the last decade, not only because of its excellent biocompatibility and biodegradability but also due to the pharmacological activities stemming from its unique amino acid compositions.

While preclinical studies underscore sericin's safety, regulatory and clinical translations remain bottlenecks. Regulatory frameworks demand rigorous characterization, including immunogenicity, long-term biodegradability, and pharmacokinetics.

The overwhelming majority of published evidence for sericin's health effects derives from in vitro cell models and animal studies, predominantly in rodents. The single human clinical study of note (burn wound healing, n=29) is small and context-specific. No large-scale randomized controlled trials have investigated sericin for any indication in healthy or patient populations. The field lacks standardization in extraction methods, molecular weight specification, dosing regimens, and outcome reporting. These gaps substantially limit the translation of mechanistic findings into evidence-based clinical recommendations. Further research is needed to better understand the biological and physicochemical properties of sericin, as they hold significant potential in biomedicine, particularly regenerative medicine.

References

Health Conditions

Health conditions that Sericin may help support.

No conditions available.

Body Systems

Body systems that Sericin may help support.

No body systems available.