Extraction of collagen from freshwater fish scales

The project "Research and production of biomaterials based on natural collagen fibers from modified fish scales, active ingredients ginsenoside Rb1, yellow tea polyphenols applied as hemostatic materials and wound treatment", No. DLTE00.04/20-21, headed by Dr. Nguyen Thuy Chinh, the Institute of Tropical Technology under the Vietnam Academy of Science and Technology (VAST) has successfully researched the extraction of collagen from freshwater fish scales.

Fish scales turnted into collagen in the laboratory

Collagen has long been widely used in biomedical applications. However, most of the popular products on the market are derived from mammals such as pigs, cows and sheep. The clinical application of these materials has long been somewhat limited due to religious and cultural influences related to materials of mammalian origin. In addition, concerns about the risk of transmission of infectious diseases from mammals also complicate the handling and inspection process.

“Fish scales are a relatively abundant source of collagen and solve most of the problems that mammalian collagen has,” Dr. Nguyen Thuy Chinh said. In the preliminary processing process, fish scales are considered waste products of residential markets or processing factories. With the annual production of tilapia in Vietnam about 50,000 tons (accounting for 2.2% of the total aquaculture production) and hundreds of thousands of tons of carp species, this study has both utilized waste products and limited environmental pollution, while obtaining a source of good quality collagen for the biomedical field.

The difference of this research topic is that the scientists used the scales of freshwater carp species originating from Vietnam, not saltwater or brackish water fish as the studies have had. Not only will the biodiversity in each location affect the maturation of freshwater fish in different ways, but at different temperatures, the composition and texture of fish scales also vary.

In addition, the research team set out to use the obtained collagen as an application carrier material for tissue regeneration and wound healing. From the mixture of fish scales obtained from local markets in Hanoi, Vinh Phuc, etc., the research team carried out washing and drying. The scales collected from the above process are soaked in the base mixture solution for 8 hours using a mechanical stirrer combined with high-speed ultrasonic stirring to remove protein and impurities. To separate minerals from fish scales, the team continued to soak the resulting mixture in acid at a ratio of fish scales to solution of 1:20 and then mechanically stirred for 20 minutes. The fish scales were then filtered and washed with distilled water.

The researchers continued to immerse fish scales in acetic acid solution for 24 hours, combining mechanical stirring and high-speed ultrasonic stirring. Filtration yielded a collagen solution in acetic acid. They added solid NaCl to the above solution and left the solution for 24 hours for the collagen to precipitate. The crude collagen was then dissolved in acetic acid for the second crystallization. Finally, the crude collagen was permeabilized by membrane dialysis for 48 hours to obtain gel-like fine collagen. If they wanted to get dried collagen, collagen gel can be freeze-dried at -20 degrees Celsius to obtain dry, spongy, ivory-white collagen.

One of the new discoveries in the extraction process is that the extraction of collagen from fish scales is completely affected by temperature. Therefore, the processing of fish scales to collect collagen is conducted in a thermostatic tank, maintained at 4 degrees Celsius. The obtained collagen has a fibrous structure, with a fiber diameter of 0.5-1 micrometers, collagen fibers are concentrated into fiber bundles, 2.5-4 micrometers in size. The representative of the research team said that this is characteristic of type 1 collagen, a common type of collagen in the human body and very important for healing wounds, creating elasticity and keeping the connection between tissues.

Effective tests

In the market, besides collagen used in beauty products, many other applications are also quite popular such as use as a wound dressing material. However, the prices of imported products are relatively high compared to domestic consumption. “With domestic technology and materials, we believe that natural collagen fibers from fish scales can be combined with ginsenoside Rb1 active ingredients, yellow tea polyphenols, to be used as hemostatic and wound healing materials,” Dr. Nguyen Thuy Chinh shared.

The process of 3D printing of collagen film from fish scales as hemostatic material. Source: Author

From the gel collagen obtained, the team mixed it with the active ingredient ginsenoside Rb1 - a chemical compound of the ginsenoside family found in the plant genus Panax, which has anti-inflammatory, anti-allergenic and tea polyphenols effects, and then put into the cylinder of the 3D printing device to print into a product film that can be applied to the wound.

Experimenting with large buttock muscle injuries in rats was conducted at the Military Medical Academy, and the results obtained made the research team realize a clear effect of collagen obtained from fish scales. The average hemostasis time of the biofilm was 104 ± 16.7 seconds, lower than that of using conventional gauze to stop bleeding (p<0.05).

The above are the initial results for Dr. Nguyen Thuy Chinh and colleagues continue to think about future studies. One of the research directions that she is interested in is if this product is not only effective for skin wounds but also effective for internal wounds.

Method of extracting collagen from Vietnamese freshwater fish scales by Dr. Nguyen Thuy Chinh and colleagues at the Institute of Tropical Technology has been granted a utility solution patent by the Intellectual Property Office of Vietnam No. 2775 published on January 25, 2022.

Translated by Phuong Huyen
Link to Vietnamese version

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