Chitosan thermogelation and cascade mineralization via sequential CaCO3 incorporations for wound care.

Physically crosslinked hydrogels have shown great potential as excellent and eco-friendly matrices for wound management. Herein, we demonstrate the development of a thermosensitive chitosan hydrogel system using CaCO3 as a gelling agent, followed by CaCO3 mineralization to fine-tune its properties. The chitosan hydrogel effectively gelled at 37 °C and above after an incubation period of at least 2 h, facilitated by the CaCO3-mediated slow deprotonation of primary amine groups on chitosan polymers. Through synthesizing and characterizing various chitosan hydrogel compositions, we found that mineralization played a key role in enhancing the hydrogels' mechanical strength, viscosity, and thermal inertia. Moreover, thorough in vitro and in vivo assessments of the chitosan-based hydrogels, whether modified with mineralization or not, demonstrated their outstanding hemostatic activity (reducing coagulation time by >41 %), biocompatibility with minimal inflammation, and biodegradability. Importantly, in vivo evaluations using a rat burn wound model unveiled a clear wound healing promotion property of the chitosan hydrogels, and the mineralized form outperformed its precursor, with a reduction of >7 days in wound closure time. This study presents the first-time utilization of chitosan/CaCO3 as a thermogelation formulation, offering a promising prototype for a new family of thermosensitive hydrogels highly suited for wound care applications.

Development of alginate macroporous hydrogels using sacrificial CaCO3 particles for enhanced hemostasis.

Polymeric hydrogels have increasingly garnered attention in the field of hemostasis. However, there remains a lack of targeted development and evaluation of non-dense polymeric hydrogels with physically incorporated pores to enhance hemostasis. Here, we present a facile route to macroporous alginate hydrogels using acid-induced CaCO3 dissolution to provide Ca2+ for alginate gelation and CO2 bubbles for subsequent macropore formation. The as-prepared pore structure in the hydrogels and its formation mechanisms were characterized through microscopic imaging and nitrogen adsorption/desorption tests. Functional analyses revealed that the macroporous hydrogels exhibited improved rheology, blood absorption, coagulation factor delivery, and platelet aggregation. Ultimately, the introduction of pores significantly enhanced the hemostatic effectiveness of alginate hydrogels in vivo, as demonstrated in rat tail amputation and liver injury models, leading to a reduction in blood loss of up to 77 % or a decrease in bleeding time of up to 88 %. Notably, hydrogels with higher porosity achieved with a CaCO3 to alginate ratio of 40 % outperformed those with lower porosity in the aforementioned properties. Furthermore, these improvements were found to be biocompatible and elicited minimal inflammation. Our findings underscore the potential of a simple porous hydrogel design to enhance hemostasis efficacy by physically incorporating macropores.

Carbonic anhydrase encapsulation using bamboo cellulose scaffolds for efficient CO2 capture and conversion.

Utilizing carbonic anhydrase (CA) to catalyze CO2 hydration offers a sustainable and potent approach for carbon capture and utilization. To enhance CA's reusability and stability for successful industrial applications, enzyme immobilization is essential. In this study, delignified bamboo cellulose served as a renewable porous scaffold for immobilizing CA through oxidation-induced cellulose aldehydation followed by Schiff base linkage. The catalytic performance of the resulting immobilized CA was evaluated using both p-NPA hydrolysis and CO2 hydration models. Compared to free CA, immobilization onto the bamboo scaffold increased CA's optimal temperature and pH to approximately 45 °C and 9.0, respectively. Post-immobilization, CA activity demonstrated effective retention (>60 %), with larger scaffold sizes (i.e., 8 mm diameter and 5 mm height) positively impacting this aspect, even surpassing the activity of free CA. Furthermore, immobilized CA exhibited sustained reusability and high stability under thermal treatment and pH fluctuation, retaining >80 % activity even after 5 catalytic cycles. When introduced to microalgae culture, the immobilized CA improved biomass production by ∼16 %, accompanied by enhanced synthesis of essential biomolecules in microalgae. Collectively, the facile and green construction of immobilized CA onto bamboo cellulose block demonstrates great potential for the development of various CA-catalyzed CO2 conversion and utilization technologies.

A thermal cross-linking approach to developing a reinforced elastic chitosan cryogel for hemostatic management of heavy bleeding.

Uncontrolled hemorrhage stands as the primary cause of potentially preventable deaths following traumatic injuries in both civilian and military populations. Addressing this critical medical need requires the development of a hemostatic material with rapid hemostatic performance and biosafety. This work describes the engineering of a chitosan-based cryogel construct using thermo-assisted cross-linking with α-ketoglutaric acid after freeze-drying. The resulting cryogel exhibited a highly interconnected macro-porous structure with low thermal conductivity, exceptional mechanical properties, and great fluid absorption capacity. Notably, assessments using rabbit whole blood in vitro, as well as rat liver volume defect and femoral artery injury models simulating severe bleeding, showed the remarkable hemostatic performance of the chitosan cryogel. Among the cryogel variants with different chitosan molecular weights, the 150 kDa one demonstrated superior hemostatic efficacy, reducing blood loss and hemostasis time by approximately 73 % and 63 % in the hepatic model, and by around 60 % and 68 %, in the femoral artery model. Additionally, comprehensive in vitro and in vivo evaluations underscored the good biocompatibility of the chitosan cryogel. Taken together, these results strongly indicate that the designed chitosan cryogel configuration holds significant potential as a safe and rapid hemostatic material for managing severe hemorrhage.

Thermo-assisted fabrication of a novel shape-memory hyaluronic acid sponge for non-compressible hemorrhage control.

Hyaluronic acid (HA), a major component of skin extracellular matrix, provides an excellent framework for hemostatic design; however, there still lacks HA materials tailored with superior mechanical properties to address non-compressible hemorrhages. Here, we present a solvent-free thermal approach for constructing a shape-memory HA sponge for this application. Following facile thermal incubation around 130 °C, HA underwent cross-linking via esterification with poly(acrylic acid) within the sponge pre-shaped through a prior freeze-drying process. The resulting sponge system exhibited extensively interconnected macropores with a high fluid absorption capacity, excellent shape-memory property, and robust mechanical elasticity. When introduced to whole blood in vitro, the HA sponges demonstrated remarkable hemostatic properties, yielding a shorter coagulation time and lower blood clotting index compared to the commercial gelatin sponge (GS). Furthermore, in vivo hemostatic studies involving two non-compressible hemorrhage models (rat liver volume defect injury or femoral artery injury) achieved a significant reduction of approximately 64% (or 56%) and 73% (or 70%) in bleeding time and blood loss, respectively, which also outperformed GS. Additionally, comprehensive in vitro and in vivo evaluations suggested the good biocompatibility and biodegradability of HA sponges. This study highlights the substantial potential for utilizing the designed HA sponges in massive bleeding management.

Incorporation of tissue factor-integrated liposome and silica nanoparticle into collagen hydrogel as a promising hemostatic system.

Bleeding complications are associated with substantial tissue morbidities and mortalities. Biomimetic composite materials that possess the ability to sufficiently stimulate and augment different physiological mechanisms of hemostasis are highly desirable to reduce bleeding-related casualties, which, however, are still largely under-explored. This study aims to develop a composite hemostatic system by combining collagen hydrogel with tissue factor (TF)-integrated liposome and silica nanoparticle, which could integrate the platelet plug-promoting capacity of collagen with the abilities of the latter two components to activate the extrinsic and intrinsic pathways of coagulation respectively. Several hydrogel compositions were synthesized and characterized. We show that lipidated TF and silica were evenly distributed in the collagen-based hydrogels, while exhibiting tunable release kinetics in simulated body fluid. Time-to-coagulation test revealed that each component in the TF-liposome/silica/collagen ternary hydrogels was hemostasis-active, and their combination showed enhanced and potent procoagulant performance, without detectable cytotoxicity against NIH/3T3 model cells. These results suggest that collagen hydrogels with embedded TF-liposome and silica nanoparticle may serve as a platform for an effective hemostatic composite that incorporates all the basic known pathways of coagulation.

Armoring a liposome-integrated tissue factor with sacrificial CaCO3 to form potent self-propelled hemostats.

The development of hemostatic materials suitable for diverse emergency scenarios is of paramount significance, and there is growing interest in wound-site delivery of hemostasis-enhancing agents that can leverage the body's inherent mechanisms. Herein we report the design and performance of a biomimetic nanoparticle system enclosing tissue factor (TF), the most potent known blood coagulation trigger, which was reconstituted into liposomes and shielded by the liposome-templated CaCO3 mineralization. The mineral coatings, which mainly comprised water-soluble amorphous and vateritic phases, synergized with the lipidated TF to improve blood coagulation in vitro. These coatings served as sacrificial masks capable of releasing Ca2+ coagulation factors or propelling the TF-liposomes via acid-aided generation of CO2 bubbles while endowing them with high thermostability under dry conditions. In comparison to commercially available hemostatic particles, CaCO3 mineralized TF-liposomes yielded significantly shorter hemostasis times and less blood loss in vivo. When mixed with organic acids, the CO2-generating formulation further improved hemostasis by delivering TF-liposomes deep into actively bleeding wounds with good biocompatibility, as observed in a rat hepatic injury model. Therefore, the designed composite mimicry of coagulatory components exhibited strong hemostatic efficacy, which in combination with the propulsion mechanism would serve as a versatile approach to treating a variety of severe hemorrhages.

Preparation and characterization of tissue-factor-loaded alginate: Toward a bioactive hemostatic material.

Tissue factor (TF), an integral membrane protein, is by far the most potent known triggering agent of blood coagulation. Inspired by TF's effectiveness in initiating coagulation, this work aims to develop hemostatic materials with TF-integrated liposomes, which combined with alginate biopolymers are designed as composite pastes or hydrogels cross-linked with Ca2+. Fluorescence measurements revealed that the proteoliposomes were evenly distributed within alginate matrices, which also remained intact after release into simulated body fluid. The proteoliposome release rate from the composite pastes increased with the decrease of alginate concentration from 3% to 1%, or relative to the corresponding hydrogels. The latter also showed a swelling property. The combination with alginate enhanced TF procoagulant activity, and most importantly the resultant composites exhibited superior hemostatic performance, yielding a shortest blood clotting time of 1.5 min while untreated blood took 14.2 min to clot, with no cytotoxicity against mammalian cells.