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Turning Aquaculture Trash to Treasure for Tissue Repair

Scientists from Nanyang Technological University (NTU), Singapore have developed a new biomaterial, which was created entirely out of bullfrog skin and fish scales, to aid tissue repair and bone regeneration.

For many of us, fish are food, not friends, as most of our encounters are limited to seeing chunks of seafood in sushi, soup or curry. In Singapore alone, 100 million kilograms of frog flesh and fish are consumed each year, making frog skin and fish scales two of Singapore’s largest aquaculture waste.

However, like all resources, consumption and waste go hand-in-hand. An estimated 20 million fishery by-products like fins, scales, and skins are disposed of annually. Fortunately, gourmet is not all fish are good for, and scientists have found a novel solution to turn aquaculture trash to treasure.

A group of researchers from Nanyang Technological University (NTU) in Singapore has constructed a novel biomaterial made completely out of bullfrog skin and fish scales to assist in bone repair. Comprised primarily of collagen and hydroxyapatite (HA), which are also found in human bones, the biomaterial has been proven to effectively support bone growth by functioning as a scaffold for bone-producing cells to attach and proliferate.

To create this biomaterial, researchers gathered fish waste from the Khai Seng Fish Farm and Jurong Frog Farm. They extracted Type 1 tropocollagen from the discarded skins of American bullfrogs, and HA from the scales of a snakehead fish, otherwise known as the Toman fish.

Both collagen and HA are critical components of bone formation as tropocollagen is essential to form collagen fibres, and HA is a calcium-phosphate compound similar to the hard tissues of humans. As such, they are suitable components to encourage cell adherence to human bones.

After removing all the impurities from the bullfrog skin, the team blended the skin and diluted it with water to form a thick collagenous paste, from which collagen was extracted. HA was simultaneously harvested from fish scales through calcination, a heat purification process that removes organic matter and produces powdered HA. Both collagen and HA were then combined and cast into a mould to produce a 3D porous scaffold.

“Using this approach, we were able to obtain the highest ever reported yield of collagen of approximately 70 per cent from frog skin, thus making this approach commercially viable,” said Asst Prof Tay from the NTU School of Biological Sciences (SBS). The whole process required less than two weeks and can be accelerated to meet future demands in the future.

To assess the performance of the biomaterial as a scaffold for bone repair, the team sowed bone-forming cells onto the scaffold and observed that the number of cells increased significantly and was uniformly distributed across the scaffold, suggesting that the scaffold can initiate proper cellular activities, which will lead to the formation of new tissues.

Then to test for inflammatory responses, the scientists used real-time polymerase chain reaction. They discovered that pro-inflammatory genes in human immune cells that were exposed to the biomaterial were only moderately expressed, thus establishing its low inflammatory effects.

The team’s experimental findings have validated their technology’s powerful benefits to stimulate regeneration of bone tissues, potentially applicable for restoring tissues lost to wounds or diseases, and post-surgical implants. The use of this biomaterial can also replace current practices of using patients’ tissues for tissue grafting, thus overcoming the need for additional surgeries. As such, this has appeared to be particularly attractive for dentistry applications to regenerate lost gum tissues, jawbones, and other dental bones during post-disease recovery as it can reduce risks, time, and cost spent in bone harvesting surgeries.

Going forward, more tests will be done to evaluate its long-term safety and efficacy as a dental product under a grant from the China-Singapore International Joint Research Institute. Further investigation will also be conducted to determine the material’s long-term effects and other applications such as repairing dermal wounds.

Besides medical benefits, the development of these biomaterials is also expected to aid the recycling of wastes into green chemicals, support sustainable environmental remediation and prevent wastewater contamination. [APBN]

Source: Wang et al. (2021). Sustainable aquaculture side-streams derived hybrid biocomposite for bone tissue engineering. Materials Science and Engineering: C, 126, 112104.