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Researchers used marine mussels to improve the mechanical properties of gelatin methacryloyl (GelMA) hydrogels. The strong threads excreted by the mussels made the stretchiness, strength, and adhesion of hydrogels at least three to six times better than the original design. The research aims to improve hydrogels for their most common use -- wound healing.

Hydrogels are unique materials that have been around for over 50 years but continue to fascinate material scientists and biomedical researchers. According to an article in the Journal of Biomedical Sciences, the earliest records of hydrogels are those of crosslinked hydroxyethyl methacrylate (HEMA) hydrogels.

With their growing demand in the medical field, scientists have been looking for ways to improve their design. This includes improving their adhesion, stretchiness, and strength for better performance.

 New Hydrogels Use Marine Mussels to Improve Adhesion, Stretchiness, Strength by Three to Six-Fold
(Photo: Wikimedia Commons)
Experimental hydrogel scaffolds prepared at NIST for culturing bone cells clearly show the dependence of bone mineralization on the stiffness of the gel. Deposited minerals are denser at the bottoms of the gradient gels, which are progressively stiffer from top to bottom. Strips are approx. 1 X 6 cm.

Modifications Improved Hydrogels but Not Overall Mechanical Properties

Hydrogels are extremely useful for their high biocompatibility and their ability to eventually integrate themselves into the body. According to Phys.org, they are ideal for simulating living tissues for replacement or regeneration and can even be used in disposable diapers, some foods, and agriculture.

However, their most notable use is for wound healing as they hydrate and form a moist and supportive environment on the affected area. This helps in blood vessel formation, breakdown of dead tissue, and activation of immune cells and prevents death in living cells.

Natural hydrogels are favored for wound healing, especially gelatin methacryloyl (GelMA) hydrogels. However, they have poor stretchiness, strength, and adhesion.

Scientists have tried adding a solution of gelatin that resulted in a dispersion of gelation polymer chains in the water. Then, they added the chemical photo-initiator to make polymer chains sticky. It was then exposed to UV light to activate the chemical and for polymer chains to crosslink to form a network.

When water enters this network, it stretches the chains and gets locked in them, showcasing the characteristics of the absorptive powers of the gelatin as it solidifies.

Scientists modified this gel by adding chemicals to the bind before exposing it to UV light or by varying parameters of UV based on the properties of the gel. This improved the physical properties of GelMA, but they also introduced another approach that improves its adhesion.

Aside from that, another approach also improved the strength of GelMA by reinforcing the additional chemical that was first introduced. However, none of these modifications improved all mechanical properties of the hydrogel.

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Marine Mussels Improved Mechanical Properties of Hydrogels

Science Daily reported that a team of researchers from the Terasaki Institute for Biomedical Innovation (TIBI) developed a new way of improving GelMA's mechanical properties by turning to nature.

They used marine mussels that secrete strong threads that are used as attachments on irregular surfaces. Marine mussels produce adhesion proteins in an acidic environment which undergoes a chemical change when exposed to the alkaline ocean and turns into threads.

Researchers from TIBI also added dopamine to increase the strength, stretchiness, and adhesive properties of GelMA hydrogels. To further increase their mechanical properties, they subjected the mixture to alkaline conditions like in oceans.

They were able to produce GelMA hydrogels with six times better stretchiness and more than three-fold strength. More so, its adhesive properties increased by four times and resistance to shear forces by seven-fold when the solution is subjected to alkaline conditions before the crosslinking step.

The team published their study titled "Stretchable and Bioadhesive Gelatin Methacryloyl-Based Hydrogels Enabled by in Situ Dopamine Polymerization," in ACS Applied Materials & Interfaces.

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