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Ice crystals help Deakin tissue engineers create healing scaffolds

Ice crystals can be used to help create artificial scaffolds to repair damaged human tissues, thanks to a breakthrough from researchers at Deakin's Institute for Frontier Materials (IFM).

The team of fibre materials engineers has so far successfully developed a strategy for growing and harvesting the unique scaffolds, which they believe could form an excellent model platform for in vitro cell culture and study, potentially leading to material that can be used to heal and regenerate human tissues.

The scaffold could one day be used to promote cell growth and healing at the site of chronic wounds, which are currently estimated to affect more than 433,000 Australians per year at a cost of $2.6 billion to the Australian healthcare system.

According to data from the Wound Healing Institute, chronic wounds are most commonly found in the elderly, with approximately 25 per cent of residents in aged care facilities suffering from a wound.

The full results of the Deakin IFM project were published in the ACS Nano scientific journal, with co-authors Dr Linpeng Fan, Associate Professor Jingliang Li, Dr Zengxiao Cai and Professor Xungai Wang.

Ice crystals formed the template for the scaffolds, consisting of aligned nanofibers and interconnecting channels.

When the team dunked a solution of silk strands into a beaker of liquid nitrogen, it triggered the rapid formation of fine ice crystals. Silk strand nanofibers then grew along the crystals, forming a network of nanofibers.

Larger ice crystals slowly grew between the nanofibers, creating a network of pores that remained when the scaffold was thawed.

Like guiding plant growth using a garden trellis, the resulting scaffold can be used to support and guide cells in the regeneration of tissues. The scaffold is made of silk fibroin, a protein regenerated from silkworm silk fibres. It can be degraded and absorbed by the human body during the tissue regeneration process.

Dr Fan said it was important to create an artificial scaffold capable of mimicking the structure and function of a naturally-occurring extracellular substance in which cells are embedded.

"Scaffolds formed by natural polymers such as proteins play crucial roles in tissue engineering, helping to induce tissue repair by undamaged cells at the site of an injury," he said.

"An ideal scaffold should not only provide a three-dimensional environment and support, but also direct cell behaviours and functions by interacting with cells."

Dr Fan said the scaffold being developed and perfected by the IFM team was uniquely suited for use in healing chronic wounds.

"What we've managed to do with this breakthrough is develop a scaffold no other technique such as electrospinning or 3D printing has ever been able to achieve," he said.

"The unique structure of the scaffold mimics that of the natural extracellular matrix of tissues such as nerve tissues, with interconnected channels that can provide space for the growth of cells or tissues - especially the blood and nerve tissues - and facilitate the exchange and transport of oxygen, nutrients, and waste."

Associate Professor Li said the interconnected channels and porous walls of the scaffold promoted significant 3D growth, similar to the growth of natural nerve tissues.

"The channels with porous nanofibrous walls in the scaffold are very important for cell and tissue infiltration as well as their growth, because they provide space and help to transport oxygen, nutrients, and waste," he said.

"The aligned nanofibers on the channel walls can also play an important role in promoting cell capture and proliferation, as well as directing cell migration.

"Furthermore, the nanofibers and nanoparticles can be good carriers for the delivery of growth factors or drugs.

"Thanks to the strategy we've developed with this work, various kinds of active scaffolds can be developed that imitate naturally-occurring shapes and direct healthy cells to grow towards the target site, which is very important to accelerate the regeneration of damaged tissues."