In vivoandin vitroevaluation of gelation and hemostatic properties of a novel tissue-adhesive hydrogel containing a cross-linkable polymeric micelle

Improved hydration property of tissue adhesive/hemostatic microparticle based on hydrophobically-modified Alaska pollock gelatin

The management of bleeding is an important aspect of endoscopic surgery to avoid excessive blood loss and minimize pain. In clinical settings, sprayable hemostatic particles are used for their easy delivery, adaptability to irregular shapes, and rapid hydration. However, conventional hemostatic particles present challenges associated with tissue adhesion. In a previous study, we reported tissue adhesive microparticles (C10-sa-MPs) derived from Alaska pollock gelatin modified with decyl groups (C10-sa-ApGltn) using secondary amines as linkages. The C10-sa-MPs adhere to soft tissues through a hydration mechanism. However, their application as a hemostatic agent was limited by their long hydration times, attributed to their high hydrophobicity. In this study, we present a new type microparticle, C10-am-MPs, synthesized by incorporating decanoyl group modifications into ApGltn (C10-am-ApGltn), using amide bonds as linkages. C10-am-MPs exhibited enhanced hydration characteristics compared to C10-sa-MPs, attributed to superior water absorption facilitated by amide bonds rather than secondary amines. Furthermore, C10-am-MPs demonstrated comparable tissue adhesion properties and underwater adhesion stability to C10-sa-MPs. Notably, C10-am-MPs exhibited accelerated blood coagulation in vitro compared to C10-sa-MPs. The application of C10-am-MPs in an in vivo rat liver hemorrhage model resulted in a hemostatic effect comparable to a commercially available hemostatic particle. These findings highlight the potential utility of C10-am-MPs as an effective hemostatic agent for endoscopic procedures and surgical interventions.

Chitosan-based multifunctional flexible hemostatic bio-hydrogel

Realizing the potential application of chitosan as an effective biomedical hemostatic agent has become an emerging research hotspot. However, fabricating a flexible chitosan-based hemostatic bio-hydrogel with self-adhesion feature in humid conditions and rapid hemostasis capability remains a challenge. Herein, we reported the development of chitosan-based hydrogels (DCS-PEGSH gels) with typical multilevel pore structures, which were cross-linked by 3-(3,4-dihydroxyphenyl) propionic acid-modified chitosan (DCS) and sebacic acid-terminated polyethylene glycol modified by p-hydroxybenzaldehyde (PEGSH). By precisely regulating the proportion of PEGSH, the fabricated bio-hydrogels displayed favorable cytocompatibility, suitable stretchability (∼780%), and blood absorbability (1300% ± 50%). Moreover, the strong adhesion (∼68.5 kPa) of the assembled bio-hydrogel ensured its firm adherence on pigskin and on bleeding wound in both static and dynamic humid environments without shedding, thus providing a long service life. The fabricated hydrogels exhibited shorter blood clotting time (50 s) and lower blood clotting index (BCI, 41) than the commercial chitosan sponge (288 s, BCI 65). Notably, the amount of blood loss from the liver in mice was reduced by almost 90% as compared to that for the control group. This study paves a solid way for developing a chitosan-based hydrogel with self-adhesive, self-healing, stretchability, biocompatibility, and antibacterial and antioxidant properties through molecular design and structural regulation, which will enable the biomedical application of chitosan in emergency hemostasis, particularly in joints and extremities. STATEMENT OF SIGNIFICANCE: The design and preparation of multifunctional integrated green adhesive bio-hydrogels while avoiding the use of organic solvents and toxic chemical reagents has been an emerging challenge. Herein, a flexible chitosan-based hemostatic bio-hydrogel that integrates multifunctional properties was successfully synthesized. The bio-hydrogel displayed suitable stretchability (780%) and blood absorbability (1300% ± 50%). Moreover, the strong adhesion (68.5 kPa) ensured firm adherence of the assembled hydrogel on pigskin and on the bleeding wound site in both static and dynamic humid environments without shedding, thus providing a long service life. In addition, the designed hydrogel showed good compatibility and antibacterial performance. The dynamic Schiff base endowed the bio-hydrogel with excellent self-healing performance without any external stimuli.

Comprehensive assessment of Nile tilapia skin collagen sponges as hemostatic dressings

Nile tilapia skin collagen sponge was fabricated by lyophilization and cross-linked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide in the presence of N-hydroxysuccinimide (EDC/NHS). The physicochemical properties were examined. The EDC/NHS cross-linked collagen sponge presented an enhanced water absorption capacity. In addition, biocompatibility and hemostatic efficiency were evaluated by acute systemic toxicity assay, dermal irritation test, intradermal reaction test, sensitization test, cytotoxicity, blood clotting assay in vitro, and liver and femoral artery hemorrhage models in vivo. Results showed that the produced collagen sponges before and after EDC/NHS cross-linking had excellent biocompatibility. Furthermore, EDC/NHS cross-linking promoted fibroblast cells viability and proliferation reflected by the MTT reduction assay. Meanwhile, EDC/NHS cross-linked collagen sponge exhibited the best blood clotting ability and hemostatic efficiency in rat femoral artery hemorrhage model in comparison with non-crosslinked and commercial collagen sponges. Our results demonstrated that the fabricated collagen sponges could be used as perfect hemostatic dressings.

Recent Advances in Hemostasis at the Nanoscale

Rapid and effective hemostatic materials have received wide attention not only in the battlefield but also in hospitals and clinics. Traditional hemostasis relies on materials with little designability which has many limitations. Nanohemostasis has been proposed since the use of peptides in hemostasis. Nanomaterials exhibit excellent adhesion, versatility, and designability compared to traditional materials, laying a good foundation for future hemostatic materials. This review first summarizes current hemostatic methods and materials, and then introduces several cutting-edge designs and applications of nanohemostatic materials such as polypeptide assembly, electrospinning of cyanoacrylate, and nanochitosan. Particularly, their advantages and working mechanisms are introduced. Finally, the challenges and prospects of nanohemostasis are discussed.

PLA- and PLA/PLGA-Emulsion Composite Biomaterial Sheets for the Controllable Sustained Release of Hydrophilic Compounds

In the present study, by spin-coating a solution containing w/o (water-in-oil) emulsions and hydrophobic polymers, we obtained sheets possessing uniformly dispersed w/o emulsions. We performed release experiments for more than 100 days and clarified the effects of the number of layers, the sheet-forming polymers (polylactide (PLA), poly(lactic-co-glycolic acid (PLGA)), the ratio of organic solvent to water, and the composition of block copolymers on the release properties of the sheets. For a variety of sheets, we successfully achieved the sustained release of compounds from the sheets for 100–150 days. The sustained-release of compounds occurred because the compounds had to diffuse into polymer networks after their release from the emulsions. Interestingly, we observed an inflection point in the release profiles at around 50 days; that is, the sheet exhibited a “two-step” release behavior. The results obtained in the present study provide strong evidence for the future possibility of the time-programmed release of multiple compounds from sheets.

Chitosan Gel Sheet Containing Polymeric Micelles: Synthesis and Gelation Properties of PEG-Grafted Chitosan

Wound-dressing sheet biomaterials can cover wound sites and enhance wound healing. In this study, a detailed evaluation of the factors affecting both the PEG modification percentage (PMP) in poly(ethylene glycol) (PEG)-grafted chitosan synthesis and the gelation properties of PEG-grafted chitosan was presented for constructing our novel hybrid hydrogel sheet consisting of PEG-grafted chitosan (a gel-forming polymer) and a reactive polymeric micelle (a crosslinker). It was confirmed that various factors (i.e., the weight ratio of PEG/chitosan, the pH of the buffer solution, reaction times, and reaction temperatures) in the preparation stage of PEG-grafted chitosans affected the PMP of PEG-grafted chitosans. Furthermore, the PMP of PEG-grafted chitosans affected their gelation properties. Finally, a ‘flexible’ hydrogel sheet that can be reversibly dried and moistened was successfully obtained. The dried rigid, thin sheet is expected to be suitable for stable preservation. The results obtained in this paper show that the incorporation of drug carriers into biomaterials is a novel approach to improve functionality.

Functional improvement of hemostatic dressing by addition of recombinant batroxobin

Although a number of natural materials have been used as hemostatic agents, many substances do not act quickly enough. Here, we created a novel dressings using collagen and chitosan with recombinant batroxobin (r-Bat) to promote faster and more effective hemostasis. We hypothesized that r-Bat would promote synergetic blood coagulation because it contains a blood coagulation active site different than those of collagen and chitosan. Our results suggest that each substances can maintain hemostatic properties while in the mixed dressings and that our novel hemostatic dressings promotes potent control of bleeding, as demonstrated by a whole blood assay and rat hemorrhage model. In a rat femoral artery model, the scaffold with a high r-Bat concentration more rapidly controlled excessive bleeding. This novel dressings has enormous possible for rapidly controlling bleeding and it improves upon the effect of collagen and chitosan used alone. Our novel r-Bat dressings is a possible candidate for improving preoperative care and displays promising properties as an absorbable agent in hemostasis.

STATEMENT OF SIGNIFICANCE

Despite the excellent hemostatic properties of collagen and chitosan pads, they reported to brittle behavior and lack sufficient hemostatic effect within relevant time. Therefore, we created a novel pad using collagen and chitosan with recombinant batroxobin (r-Bat). r-Bat acts as a thrombin-like enzyme in the coagulation cascade. Specifically, r-Bat, in contrast to thrombin, only splits fibrinopeptide A off and does not influence other hemostatic factors or cells, which makes it clinically useful as a stable hemostatic agent. Also the materials in the pad have synergetic effect because they have different hemostatic mechanisms in the coagulation cascade. This report propose the novel hemostatic pad isreasonable that a great potential for excessive bleeding injury and improve effects of natural substance hemostatic pad.

Viscosity-controlled printing of supramolecular-polymeric hydrogels via dual-enzyme catalysis

Hybrid hydrogels based on a guanidinium-containing oligopeptide are prepared via dual-enzyme-triggered reactions. An extended time window is available for in situ viscosity-controlled 3D printing.

Poly(ɛ-caprolactone) (PCL)-polymeric micelle hybrid sheets for the incorporation and release of hydrophilic proteins

Sheets have several advantages over conventional gel- or particle-type drug carriers. Sheets have several notable attributes: sheets' size and shape are easily adjustable, sheets are highly accessible in surgery, and sheets have a large contact area relative to drug-targeting sites. However, it is difficult to incorporate hydrophilic proteins into hydrophobic sheets and to release the proteins over the long term in a sustained manner. In the present study, we show that "poly(ɛ-caprolactone) (PCL)-polymeric micelle hybrid sheets" can be used for the incorporation and release of hydrophilic proteins. Polymeric micelles (i.e., spaces that can incorporate hydrophilic compounds) are, in this study, uniformly dispersed in hydrophobic and biocompatible biomaterial sheet. We have clarified that the composition of block copolymer, methoxy-terminated poly(ethylene glycol)-block-poly(ɛ-caprolactone) (CH3O-PEG-b-PCL), can affect two variables: the stability of w/o emulsion and the release properties of the resulting sheets, by means of visual qualitative observations, newly developed quantitative analyses (advanced fractal analysis, advanced FD) based on deviation of the fractal dimension (FD), and release experiments. We clarified that the release behavior of BSA was affected by the composition of the block copolymers and the resulting emulsion. The results obtained in this paper show that the hydrophobic sheets in which polymeric micelles providing hydrophilic spaces were dispersed could be an effective platform for incorporating and releasing hydrophilic proteins.

Unexpected and successful "one-step" formation of porous polymeric particles only by mixing organic solvent and water under "low-energy-input" conditions

We found that porous particles were unexpectedly obtained in a "one-step" manner only by mixing an organic solvent and water under "low-energy-input" (i.e., low-homogenization-rate) conditions. This phenomenon was attributable to the unexpected formation of the spontaneously formed water-in-oil (w/o) emulsions in the droplets of o/w emulsions. The unexpected formation resulted in the successful formation of water-in-oil-in-water (w/o/w) emulsions instead of o/w emulsions, although the mixed solution containing both an organic solvent and water were simply emulsified in the presence of block copolymers. The present study clarifies the effects of the various preparation conditions on the morphology of unexpected w/o/w emulsions and resulting particles. The porous particles are expected to be suitable drug carriers for pulmonary delivery. The results obtained in the present study show that a newly developed one-step emulsification can be a powerful and facile technique for preparing porous polymeric particles.

Hemostatic strategies for traumatic and surgical bleeding

Wide interest in new hemostatic approaches has stemmed from unmet needs in the hospital and on the battlefield. Many current commercial hemostatic agents fail to fulfill the design requirements of safety, efficacy, cost, and storage. Academic focus has led to the improvement of existing strategies as well as new developments. This review will identify and discuss the three major classes of hemostatic approaches: biologically derived materials, synthetically derived materials, and intravenously administered hemostatic agents. The general class is first discussed, then specific approaches discussed in detail, including the hemostatic mechanisms and the advancement of the method. As hemostatic strategies evolve and synthetic-biologic interactions are more fully understood, current clinical methodologies will be replaced.

Rapidly curable chitosan-PEG hydrogels as tissue adhesives for hemostasis and wound healing

Chitosan-poly(ethylene glycol)-tyramine (CPT) hydrogels were rapidly formed in situ using horseradish peroxidase and hydrogen peroxide to explore their performance as efficient tissue adhesives. A poly(ethylene glycol) modified with tyramine was grafted onto a chitosan backbone to enhance the solubility of the chitosan and to crosslink into three-dimensional networks. The elastic modulus of the hydrogels could be controlled by changing the crosslinking conditions, and the mechanical strength influenced the tissue adhesiveness of the hydrogels. The hydrogels showed the adhesiveness ranging from 3- to 20-fold that of fibrin glue (Greenplast®). The hemostatic ability of the hydrogels was evaluated on the basis that bleeding from liver defects was significantly arrested by the combined effect of the adhesiveness of the hydrogels and the hemostatic property of the chitosan materials. The enzymatic crosslinking method enabled the water-soluble chitosan to rapidly form hydrogels within 5s of an incision into the skin of rats. Histological results demonstrated that the CPT hydrogels showed superior healing effects in the skin incision when compared to suture, fibrin glue and cyanoacrylate. By 2weeks post-implantation, the wound was completely recovered, with a newly formed dermis, due to the presence of the CPT hydrogels in the incision. These results suggest that the in situ curable chitosan hydrogels are very interesting and promising tissue adhesive devices for biomedical applications.