Shape memory foam composite fills deep wounds

Novel hemostatic treatment based on a shape memory polymer (SMP) foam combined with an antibacterial hydrogel suitable for deep wounds

Original source: Materials Today

Controlling severe blood loss can make the difference between life and death in a trauma situation. Most often, blood loss control or hemostatic treatments rely on compression – like a tourniquet – and gauze to absorb the liquid. But these treatments are less effective for deep or irregularly shaped injuries from bullets or shrapnel.

Now researchers from Texas A&M University, led by researchers Elizabeth Cosgriff-Hernandez and Duncan J. Maitland, have come up with a novel alternative based on a shape memory polymer (SMP) foam combined with an antibacterial hydrogel [Landsman et al., Acta Biomaterialia 47 (2016), 91].

The composite material combines the volume-filling and rapid-clotting attributes of SMP foams with the swelling capacity of hydrogels. A polyurethane SMP foam is coated with n-vinylpyrrolidone (NVP) and polyethylene glycol diacrylate (PEGDA) hydrogel that, in a novel addition, contains iodine in the form of a complex (PVP-I2 or povidone-iodine), which is widely used as a surgical antiseptic. The iodine-containing hydrogel gives the composite an antibacterial effect (reducing viability of common bacteria by 80%) while increasing fluid uptake 19-fold over uncoated SMP foams.

In a trauma situation, a single, small device – about the size of pencil lead – would be inserted into the wound. When the composite encounters blood, the device expands to 10-times its usual volume, filling the void and absorbing excess liquid.

“The device [can] be easily inserted into small, irregularly shaped wounds and subsequently expands to completely fill the entire wound to stop bleeding rapidly,” explains first author on the study Todd L. Landsman.

However, although it is crucial that the dressing fills the wound, it is equally important that it does not cause any further tissue damage. According to the researchers’ tests, the expansion forces exerted by the device do not exceed 0.6 N, making tissue damage to the wound site as a result of the composite unlikely.

The researchers’ initial findings indicate that the SMP foam/antibacterial hydrogel composite could be extremely useful in treating hemorrhaging patients on battlefields or in civilian emergencies.

“There have been a number of dressings designed to prevent infection or provide rapid hemostasis (halting blood loss) by filling the wound bed with multiple devices, but [our] dressing combines rapid expansion to fill the wound to stop bleeding and bactericidal activity in a single device,” says Landsman.

Balancing the rate of expansion with the swelling capacity – by altering the relative proportions of SMP foam and hydrogel – will be needed before actual devices can be formulated, say the researchers.

“For the next generation of this technology, our collaborators are investigating means of achieving antibacterial properties with little to no impact on expansion rates of the device,” he says.