Hydrophobic aerogel-modified hemostatic gauze with thermal management performance

Abstract

Current hemostatic agents or dressings are not efficient under extremely hot and cold environments due to deterioration of active ingredients, water evaporation and ice crystal growth. To address these challenges, we engineered a biocompatible hemostatic system with thermoregulatory properties for harsh conditions by combining the asymmetric wetting nano-silica aerogel coated-gauze (AWNSA@G) with a layer-by-layer (LBL) structure. Our AWNSA@G was a dressing with a tunable wettability prepared by spraying the hydrophobic nano-silica aerogel onto the gauze from different distances. The hemostatic time and blood loss of the AWNSA@G were 5.1 and 6.9 times lower than normal gauze in rat's injured femoral artery model. Moreover, the modified gauze was torn off after hemostasis without rebleeding, approximately 23.8 times of peak peeling force lower than normal gauze. For the LBL structure, consisting of the nano-silica aerogel layer and a n-octadecane phase change material layer, in both hot (70 °C) and cold (-27 °C) environments, exhibited dual-functional thermal management and maintained a stable internal temperature. We further verified our composite presented superior blood coagulation effect in extreme environments due to the LBL structure, the pro-coagulant properties of nano-silica aerogel and unidirectional fluid pumping of AWNSA@G. Our work, therefore, shows great hemostasis potential under normal and extreme temperature environments.

Keywords: Harsh environments; Hydrophobic hemostasis; Hydrophobic methyl modified nano-silica aerogel; Thermal management; Unidirectional fluid pumping.

Graphical abstract

Fig. 1

(a) Condensation mechanism of silica particles; (b) surface modification reactions of silica particles; (c) EDS analysis (I was SEM image, II- IV were elemental maps, and V was spectrum) of nano-silica aerogel; (d) FT-IR spectrum and image of water contact angles test (inset) for nano-silica aerogel; (e) particle size analysis for the nano-silica aerogel; (f) SEM image of the nano-silica aerogel; (g) TEM image of the nano-silica aerogel; (h) nitrogen adsorption−desorption curve of the nano-silica aerogel; (i) pore size distribution (PSD) of the nano-silica aerogel.

Fig. 2

(a) The amount per unit area (APUA) of nano-silica aerogel on gauze (n = 3); (b) FT-IR spectrums of hydrophobic nano-silica aerogel-coated gauzes with varied spray distance; (c) SEM image of hydrophobic nano-silica aerogel-coated-gauzes; (d) EDS analysis (I was SEM image, and II- IV were elemental maps) of hydrophobic nano-silica aerogel-coated gauze; (e) quantitative analysis on the elemental composition of aerogel coated-gauze (n = 3).

Fig. 3

(a) SBF wettability of gauzes; (b) blood wettability of gauzes; (c) water uptake of gauzes (n = 3); (d) water vapor permeation rate of gauzes (n = 3).

Fig. 4

(a) The transmission process of the SBF droplet (tagged with 1% sodium fluorescein) contacting with gauzes under UV light; (b) graphic illustration of the unidirectional liquid pumping mechanism.

Fig. 5

(a) Macroscopical view of centrifugally obtained supernatants; (b) hemolysis rate of nano-silica aerogel-coated gauze (n = 3); (c) cell viability measured by CCK8 assay (n = 3); (d) images of live/dead cell staining; (e) illustration of the prepared sample for skin compatibility testing; (f) four samples were applied to the skin of the rat's back; (g) skin aera after 12 h of contact with the prepared sample.

Fig. 6

(a) Schematic illustration of whole blood clotting test of gauzes; (b) blood coagulation index of gauzes (n = 5); (c) illustration of plasma clotting test; (d) image of liquid plasma transformed into coagulation formation; (e) the time of plasma clotting (n = 5).

Fig. 7

(a) Schematic illustration of hemostasis process of nano-silica aerogel coated-gauze in rat femoral artery injury; (b) images of hemostasis in process; (c) laminated layers of gauze were unfolded; (d) statistical graph of hemostatic time in rats treated with normal gauze versus nano-silica aerogel coated-gauze (n = 4); (e) statistical graph of total blood loss in rats treated with normal gauze versus nano-silica aerogel coated-gauze (n = 4).

Fig. 8

Erythrocytes on: (a) normal gauze; (b) nano-silica aerogel-coated gauze with a spray distance of 10 cm; (c) nano-silica aerogel-coated gauze with a spray distance of 2 cm; (d) asymmetric wetting nano-silica aerogel-coated gauze (AWNSA@G).

Fig. 9

(a) Illustration of the gauze applied onto the wound of the rat back; (b) schematic method for measuring peeling force; (c) the experimental procedure for peeling the gauze from the wound site, (d) the peak peeling force of different gauzes (n = 3).

Fig. 10

(a) Schematic diagram of LBL structure assembling with nano-silica aerogel layer and PCM layer under extreme environments; (b) schematic illustration of the LBL structure tested on a heating/cooling plate; (c) infrared thermography image of summer ground surface; (d) infrared thermography image of the sample on a heating plate at indicated time points; (e) time-temperature curve of heating plate and LBL structure; (f) time-temperature difference curve of heating plate and LBL structure; (g) infrared thermography image of the sample on a cooling plate at indicated time points; (h) time-temperature curve of cooling plate and LBL structure; (i) time-temperature difference curve of cooling plate and LBL structure.

Fig. 11

(a) Blood coagulation of composites in vitro under harsh hot environment (70 °C) (n = 3); (b) blood coagulation of composites in vitro under harsh cold environment (−27 °C) (n = 3); (c) platelets (indicated by red arrows) on normal gauze and asymmetric wetting nano-silica aerogel-coated gauze (AWNSA@G) observed by SEM; (d) platelets adhesion determined by LDH assay (n = 3); (e) the effect of nano-silica aerogel on activation of coagulation factor XII (FXIIa) (n = 3); (f) in vitro coagulation of normal gauze and AWNSA@G observed by SEM; (g) schematic diagram of the hemostasis mechanism for AWNSA@G; (h) thrombin activity in extreme hot and cold environments (n = 3).