Sealing wounds with hydrogel

Scientists at the University of Delawarehave invented a biomaterial with anti-bacterial properties that could help repair damaged tissue when it is injected into a wound.

The low-viscosity gel solidifies almost on contact with a wound, and could help to regenerate healthy tissue in a cancerous liver, heal a biopsy site or provide an anti-bacterial pain-killing solution to wounded soldiers in the field.

Hydrogels are formed from networks of super-absorbent, chain-like polymers. Although not water soluble, they are able to soak up large amounts of water, and their porous structure allows nutrients and cell wastes to pass through them.

The researchers, Joel Schneider and Darrin Pochan, have developed a peptide-based hydrogel that, once implanted in the human body, become scaffolds for cells to hold onto and grow. Such cells include fibroblasts, which form connective tissue, and osteoblasts, which form bones.

‘They’re like rebar when you’re building something with concrete,’ Schneider said. ‘They give the cement something to hang onto.’

The hydrogel is based on a self-assembling peptide called MAX1, a short chain of amino acids that the scientists designed six years ago. The amino acids, which make up proteins, bond together to form chains that fold up into more compact shapes with specific functions.

The peptide used in the hydrogel was designed to automatically fold into a specific shape in response to a particular trigger, such as exposure to light. After folding, it self-assembles, to create the hydrogel.

Using MAX8, a new generation of the original peptide, Lisa Haines-Butterick, a doctoral student working on the project, developed the technique of encapsulating living cells in the hydrogel and then injecting the gel into secondary sites without harming the cells.

‘Although we have currently only demonstrated this capacity of our gels using simple models, we envision that when injected into the body, the cells encapsulated in the gel can go about their business in restructuring the tissue,’ said Schneider.

A feature of the hydrogel is that it is cytocompatible, which means that is not toxic to the cell it is being delivered to. The researchers are also exploring the antimicrobial qualities of the gel, which kills certain gram-negative and gram-positive bacteria.

The hydrogel can be delivered in different forms: it can be freeze-dried into a powder and mixed with a powder for use, or injected from a syringe.

The scientists have also envisaged use of the hydrogel in repairing damaged livers.

‘The liver is an amazing organ,’ said Schneider. ‘It has the ability to regenerate itself quite easily. If almost 70 percent of it is lost to disease and removed, that remaining 30 percent can grow back, affording a functional liver. We want to use the hydrogels to deliver hepatocytes to the liver.

‘These could be used to beef up the liver’s function prior to surgery if, for example, someone had hepatitis, or drank a lot, factors that would normally limit the amount of cancerous liver that can be removed.’