Preparation And Performance Research Of Shape Memory Hemostatic Cryogel For Controlling Noncompressible Hemorrhage

Noncompressible trauma hemorrhage(e.g.,penetrating and perforating wounds)caused by gunshots,sharp objects,or car accidents results in an extremely high mortality rate.Since these wounds usually have narrow entrances and deep bleeding sites,making it difficult for traditional hemostatic materials to stop bleeding by applying direct pressure or penetrating deeply into the bleeding site to tamponade,there is an urgent need to develop new hemostatic techniques.To this end,researchers have developed hemostatic materials with shape memory function,which can expand in volume by absorbing blood to form a physical barrier for hemostasis.However,the traditional preparation methods of shape memory hemostatic materials have numerous limitations(e.g.,residual foaming agents,cumbersome preparation steps,poor mechanical properties of hemostatic materials,insufficient pore connectivity,etc.).In contrast,the cryogelation method can obtain hydrogels-cryogels with highly interconnected macroporous structures and excellent shape memory ability through a simple "freeze-thaw" step.In this work,the CS/HLC/ODex(CHO)cryogel with shape memory property was prepared by cryogelation method using aldehyde-modified dextran(ODex)as a cross-linking agent,combined with the excellent hemostatic activity of chitosan(CS)and recombinant collagen(HLC).In order to improve the shape memory property of CHO cryogel,a series of PDA-NPs-doped CS/HLC/ODex/PDA-NPs(CHOP)cryogels were prepared by incorporating polydopamine nanoparticles(PDA-NPs)into the CHO precursor solution.Then,a series of evaluations were carried out on the physicochemical properties,hemostatic properties,biocompatibility and wound healing-promoting ability of CHO and CHOP cryogels.The specific experimental results were as follows:(1)The optimal preparation process of CHO cryogel was optimized by orthogonal and singlefactor experiments,and the optimal preparation conditions were determined as follows: the concentration of CS was 1%(w/v),the concentration of HLC was 0.5%(w/v),the concentration of ODex was 0.5%(w/v),the reaction temperature was-18 ℃,and the reaction time was 36 h.After optimization,the resulting CHO cryogel exhibited excellent procoagulant ability with a coagulation index of 15.8% and exhibited good shape memory behavior in phosphate buffer solution(PBS solution)with a shape recovery speed of 15.3 s,but showed poor shape recovery behavior in blood with a shape recovery speed of 48.1 s.(2)Based on the optimization of the CHO preparation process,CHOP cryogels were prepared by doping PDA-NPs,and their shape recovery speed was accelerated with the increase of the concentration of PDA-NPs,in which CHOP4(0.2% of PDA-NPs)showed a shape recovery speed of 4.4 s in PBS solution,and that in blood was 16.2 s,which was about 66% shorter than that of CHO.(3)PDA-NPs could significantly enhance the mechanical properties of the cryogels.The CHOP cryogels exhibited highly interconnected pore structures with an average pore size of about 100 μm and porosity of about 93%,and had excellent liquid uptake rates of about 5500%for PBS solution and 4000% for blood.There was no significant loss in strength of CHOP cryogels after 10 cycles of compression at 80% compressive strain.(4)In vitro coagulation and in vivo hemostasis experiments showed that the CHOP cryogels exhibited better pro-coagulation abilities and hemostatic effects compared to commercial gelatin sponge and gauze,and could effectively control bleeding from surface trauma and internal noncompressible trauma.Hemostatic mechanism experiments showed that the CHOP cryogels could accelerate hemostasis by effectively aggregating and activating blood cells,adsorbing fibrinogen,activating intrinsic coagulation pathway,and promoting thrombin generation.(5)The results of hemolysis experiments,cytotoxicity experiments,subcutaneous implantation experiments,and in vitro and in vivo degradation experiments showed that the CHOP cryogels had good blood compatibility,cytocompatibility,histocompatibility and biodegradability.Wound healing experiments showed that the CHOP cryogels could accelerate the reconstruction of skin structure and function.