Absorbable hemostatic hydrogels comprising composites of sacrificial templates and honeycomb-like nanofibrous mats of chitosan

Abstract

The development of hemostatic technologies that suit a diverse range of emergency scenarios is a critical initiative, and there is an increasing interest in the development of absorbable dressings that can be left in the injury site and degrade to reduce the duration of interventional procedures. In the current study, β-cyclodextrin polyester (CDPE) hydrogels serve as sacrificial macroporous carriers, capable of degradation under physiological conditions. The CDPE template enables the assembly of imprinted chitosan honeycomb-like monolithic mats, containing highly entangled nanofibers with diameters of 9.2 ± 3.7 nm, thereby achieving an increase in the surface area of chitosan to improve hemostatic efficiency. In vivo, chitosan-loaded cyclodextrin (CDPE-Cs) hydrogels yield significantly lower amounts of blood loss and shorter times to hemostasis compared with commercially available absorbable hemostatic dressings, and are highly biocompatible. The designed hydrogels demonstrate promising hemostatic efficiency, as a physiologically-benign approach to mitigating blood loss in tissue-injury scenarios.

Fig. 1

CDPE hydrogels are capable of loading chitosan, and degrade in alkaline conditions. a Image of CDPE gel, upon initial immersion in a 1 wt% chitosan solution. b Image of CDPE gel, after 7 days immersion in a 1 wt% chitosan solution, showing a slight increase in opacity of the gel. c Image of templated chitosan monolith, after lyophilization of composite gel and rinsing with alkaline solution to remove the CDPE template. d Simplified representation of the chemical structure of CDPE, indicating the possibility of diverse linkage regiochemistry. e FTIR spectra of materials at each stage of the templating process. f ¹H NMR (500 MHz, in PBS D₂O solution) spectra of the CDPE template at 24 h time points, showing degradation over 7 days

Fig. 2

Prepared materials exhibit amorphous, macroporous morphology. a Simplified illustration of the chitosan templating process, administration of CDPE-Cs to wound site, and template removal for imaging. b SEM image of CDPE after drying by lyophilization, showing complex, porous morphology (scale bar is 2 µm). c SEM image of chitosan-loaded composite CDPE-Cs gel after lyophilization (scale bar is 2 µm). d SEM image of templated chitosan material, displaying a honeycomb-like structure (scale bar is 2 µm). e–f Magnified SEM images of nanofibrillar domains in the templated chitosan, with a web-like morphology within the network cavities (scale bars are 500 nm and 300 nm, respectively). g Histogram plot showing the distribution of fiber diameters measured by SEM

Fig. 3

In vivo examination of CDPE-Cs hydrogels against several controls. a Conventional gauze dressings, Curaspon®, Surgicel®, and CDPE and CDPE-Cs hydrogels were applied immediately after induction of the liver injury and absorption of the initial bleeding from the injury sites, to determine the total time to hemostasis in rats (n = 6 animals per group). For gauze dressings, bleeding did not stop until the end of experiments (600 s). b The total amount of blood loss, measured over 10 min, in rats (n = 6 animals per group). c Time to hemostasis for rabbits (n = 6 animals per group). d Blood loss in rabbits (n = 6 animals per group). e Time to hemostasis for pigs (n = 6 animals per group). f Blood loss in pigs (n = 6 animals per group). g The mean arterial pressure of the rabbits were monitored over 90 min, where the measurements over the first 30 min represent the mean arterial pressure of animals before induction of the liver injury (n = 3 animals per group). Box plots correspond to means (center line) ± SD (boundaries). Source data are provided as a Source Data file