Toxicity of aluminum silicates used in hemostatic dressings toward human umbilical veins endothelial cells, HeLa cells, and RAW267.4 mouse macrophages.

Background: Aluminum silicates have been used to control bleeding after severe traumatic injury. QuikClot (QC) was the first such product, and WoundStat (WS) is the most recent. We recently observed that WS caused vascular thrombosis when applied to stop bleeding. This study investigated the cellular toxicity of WS in different cell types that may be exposed to this mineral and compared the results with other minerals such as bentonite, kaolin, and QuikClot ACS+ (QC+).

Methods: Human umbilical vein endothelial cells (HUVEC), HeLa cells, and RAW267.4 mouse macrophage-like cells (RAW) were incubated directly with different concentrations of each mineral for 24 hours. Cell viability was determined metabolically using the AlamarBlue fluorescent technique. In another experiment, minerals were exposed to HUVEC via Transwell inserts with a polycarbonate filter (0.4-μm pore size) to prevent direct contact between cells and minerals for determining whether direct exposure or leaching compounds from minerals cause cytotoxicity.

Results: Incubation of HUVEC and RAW cells with 1 to 100 μg/mL of the minerals for 24 hours resulted in differential toxicities. The cytotoxicity of WS was equal to that of bentonite and higher than kaolin and QC+. Neither cell type survived for 24 hours in the presence of 100 μg/mL WS or bentonite. These minerals, however, had little effect on the viability of HeLa cells. In the second HUVEC experiment, a 10 times higher concentration of these compounds placed in Transwell inserts yielded no decrease in cell viability. This result indicates that leaching toxicants or binding of nutrients by the ion-exchange properties of minerals did not cause the toxicity.

Conclusions: Although aluminum silicates seem relatively innocuous to epithelial cells, all produced some toxicity toward endothelial cells and macrophages. WS and bentonite were significantly more toxic than kaolin and zeolite present in QC+, respectively, at equivalent doses. The cytotoxic effect seemed to be caused by the direct contact of the minerals with the cells present in wounds. These data suggest that the future clearance of mineral-based hemostatic agents should require more extensive cytotoxicity testing than the current Food and Drug Administration requirements.