Expanding Hydrophobically Modified Chitosan Foam for Internal Surgical Hemostasis: Safety Evaluation in a Murine Model

Abstract Background A novel injectable expanding foam based on hydrophobically modified chitosan (HM-CS) was developed to improve hemostasis during surgeries. HM-CS is an amphiphilic derivative of the natural biopolymer chitosan (CS); HM-CS has been shown to improve the natural hemostatic characteristics of CS, but its internal safety has not been systematically evaluated. The goal of this study was to compare the long-term in vivo safety of HM-CS relative to a commonly used fibrin sealant (FS), TISSEEL (Baxter). Methods Sixty-four Sprague–Dawley rats (275-325 g obtained from Charles River Laboratories) were randomly assigned to control ( n  = 16) or experimental ( n  = 48) groups. Samples of the test materials (HM-CS [ n  = 16], CS [ n  = 16], and FS [ n  = 16]) applied to a nonlethal liver excision (0.4 ± 0.3 g of the medial lobe) in rats were left inside the abdomen to degrade. Animals were observed daily for signs of morbidity and mortality. Surviving animals were sacrificed at 1 and 6 wk; the explanted injury sites were microscopically assessed. Results All animals (64/64) survived both the 1- and 6-wk time points without signs of morbidity. Histological examination showed a comparable pattern of degradation for the various test materials. FS remnants and significant adhesions to neighboring tissues were observed at 6 wk. Residual CS and HM-CS were observed at the 6 wk with fatty deposits at the site of injury. Minimal adhesions were observed for CS and HM-CS. Conclusions The internal safety observed in the HM-CS test group after abdominal implantation indicates that injectable HM-CS expanding foam may be an appropriate internal use hemostatic candidate.