Foams with Enhanced Rheology for Stopping Bleeding

Abstract

Bleeding from injuries to the torso region is a leading cause of fatalities in the military and in young adults. Such bleeding cannot be stopped by applying direct pressure (compression) of a bandage. An alternative is to introduce a foam at the injury site, with the expansion of the foam counteracting the bleeding. Foams with an active hemostatic agent have been tested for this purpose, but the barrier created by these foams is generally not strong enough to resist blood flow. In this paper, we introduce a new class of foams with enhanced rheological properties that enable them to form a more effective barrier to blood loss. These aqueous foams are delivered out of a double-barrelled syringe by combining precursors that produce bubbles of gas (CO2) in situ. In addition, one barrel contains a cationic polymer (hydrophobically modified chitosan, hmC) and the other an anionic polymer (hydrophobically modified alginate, hmA). Both these polymers function as hemostatic agents due to their ability to connect blood cells into networks. The amphiphilic nature of these polymers also enables them to stabilize gas bubbles without the need for additional surfactants. hmC–hmA foams have a mousse-like texture and exhibit a high modulus and yield stress. Their properties are attributed to the binding of hmC and hmA chains (via electrostatic and hydrophobic interactions) to form a coacervate around the gas bubbles. Rheological studies are used to contrast the improved rheology of hmC–hmA foams (where a coacervate arises) with those formed by hmC alone (where there is no such coacervate). Studies with animal wound models also confirm that the hmC–hmA foams are more effective at curtailing bleeding than the hmC foams due to their greater mechanical integrity.

Bio-inspired, bio-degradable adenosine 5′-diphosphate-modified hyaluronic acid coordinated hydrophobic undecanal-modified chitosan for hemostasis and wound healing

“…The peak at 1150 cm −1 indicates the stretching vibration of the C–O single bond, and the peaks at 1070 cm −1 and 890 cm −1 correspond to C–O–C symmetric stretching vibrations [ 35 ]. After CS was conjugated with undecanal, the peak of UCS at 2900 cm −1 (–CH 2 –) was enhanced and the appearance of the spectra at 1275 cm −1 corresponded to the stretching vibration peak of the C–N bond [ 2 , 36 ], indicating that CS and undecanal were chemically conjugated. Also, the 1 H NMR spectrum of CS and UCS was compared ( Fig.…”

“…All of these changes could be attributed to the following aspects: the enhancement of G′ and G″ for HA/UCS and HA-ADP/UCS could be associated with the substitution of the amine group of CS and the carboxylic acid of HA, which could enhance the hydrophobic interaction between UDA groups of UCS ( Fig. 1 H) [ 36 ] and alter the density of electronic interactions between the amine group of CS and the carboxylic acid and diphosphate groups [ 14 , 38 ]. In addition, there were displayed clear potential changes before and after the modification of CS and HA ( Fig.…”

Superfast-Expanding Porous Hydrogels: Pushing New Frontiers in Converting Chemical Potential into Useful Mechanical Work

“…There are several key differences compared to previous approaches reported in the literature, and these differences will be important in analyzing the microstructure and performance of our gels. First of all, we use a DBS and the acid–base reaction to generate the foam in situ , whereas most researchers have simply added NaHCO 3 (base) to an acidic monomer solution containing a surfactant and agitated the sample to produce a foam. − The DBS gives rise to smaller bubbles and a more homogeneous foam compared to simple agitation . Second, we use a polymeric stabilizer (hmC) rather than a small-molecule surfactant to stabilize the foam .…”

“…Here, we present a new approach that yields porous gels with an unprecedented combination of rapid swelling/expansion rates and high swelling extents. Our approach involves foaming of a monomer solution by injecting it out of a double-barreled syringe (DBS) . As shown in Figure , the foam is generated in situ via the reaction of an acid and a base in the two barrels of the DBS, which combine to produce CO 2 gas in the form of bubbles.…”

Positionspapier der Initiative Chronische Wunde (ICW) e. V. zur Nomenklatur des Débridements chronischer Wunden

“…Hierbei kommt es meist zu Gewebe- und Gefäßverletzungen mit Blutungen. Eine Blutstillung kann beispielsweise durch manuelle Kompression oder die Verwendung hämostyptischer Wundauflagen wie beispielsweise Alginat- oder Chitosan-Verbände erfolgen [ 5 ]. Eine kurzfristige klinische Überprüfung der Blutungskontrolle wird empfohlen.…”