Coagulant Protein-Free Blood Coagulation Using Catechol-Conjugated Adhesive Chitosan/Gelatin Double Layer.

Since the discovery of polyphenolic underwater adhesion in marine mussels, researchers strive to emulate this natural phenomenon in the development of adhesive hemostatic materials. In this study, bio-inspired hemostatic materials that lead to pseudo-active blood coagulation, utilizing traditionally passive polymer matrices of chitosan and gelatin are developed. The two-layer configuration, consisting of a thin, blood-clotting catechol-conjugated chitosan (CHI-C) layer and a thick, barrier-functioning gelatin (Geln) ad-layer, maximizes hemostatic capability and usability. The unique combination of coagulant protein-free condition with CHI-C showcases not only coagulopathy-independent blood clotting properties (efficacy) but also exceptional clinical potential, meeting all necessary biocompatibility evaluation (safety) without inclusion of conventional coagulation triggering proteins such as thrombin or fibrinogen. As a result, the CHI-C/Geln is approved by the Ministry of Food and Drug Safety (MFDS, Republic of Korea) as a class II medical device. Hemostatic efficacy observed in multiple animal models further demonstrates the superiority of CHI-C/Geln sponges in achieving quick hemostasis compared to standard treatments. This study not only enriches the growing body of research on mussel-inspired materials but also emphasizes the potential of biomimicry in developing advanced medical materials, contributing a promising avenue toward development of readily accessible and affordable hemostatic materials.

Endoscopic application of mussel-inspired phenolic chitosan as a hemostatic agent for gastrointestinal bleeding: A preclinical study in a heparinized pig model.

Marine mussels secrete adhesive proteins to attach to solid surfaces. These proteins contain phenolic and basic amino acids exhibiting wet adhesion properties. This study used a mussel-inspired hemostatic polymer, chitosan-catechol, to treat gastrointestinal bleeding caused by endoscopic mucosal resection in a heparinized porcine model. We aimed to evaluate the hemostatic efficacy and short-term safety of this wet adhesive chitosan-catechol. We used 15 heparinized pigs. Four iatrogenic bleeding ulcers classified as Forrest Ib were created in each pig using an endoscopic mucosal resection method. One ulcer in each pig was untreated as a negative control (no-treatment group). The other three ulcers were treated with gauze (gauze group), argon plasma coagulation (APC group), and chitosan-catechol hemostatic agent (CHI-C group) each. The pigs were sacrificed on Days 1, 5, and 10, and histological examination was performed (n = 5 per day). Rapid hemostasis observed at 2 min after bleeding was 93.3% (14/15) in the CHI-C group, 6.7% (1/15) in the no-treatment group, 13.3% (2/15) in the gauze group, and 86.7% (13/15) in the APC group. No re-bleeding was observed in the CHI-C group during the entire study period. However, a few re-bleeding cases were observed on Day 1 in the no-treatment, gauze, and APC groups and on Day 5 in the gauze and APC groups. On histological analysis, the CHI-C group showed the best tissue healing among the four test groups. Considering the results, chitosan-catechol is an effective hemostatic material with reduced re-bleeding and improved healing.

Coagulopathy-independent, bioinspired hemostatic materials: A full research story from preclinical models to a human clinical trial.

Since the first report of underwater adhesive proteins of marine mussels in 1981, numerous studies have reported mussel-inspired synthetic adhesive polymers. However, none of them have developed up to human-level translational studies. Here, we report a sticky polysaccharide that effectively promotes hemostasis from animal bleeding models to first-in-human hepatectomy. We found that the hemostatic material instantly generates a barrier layer that seals hemorrhaging sites. The barrier is created within a few seconds by in situ interactions with abundant plasma proteins. Therefore, as long as patient blood contains proper levels of plasma proteins, hemostasis should always occur even in coagulopathic conditions. To date, insufficient tools have been developed to arrest coagulopathic bleedings originated from genetic disorders, chronic diseases, or surgical settings such as organ transplantations. Mussel-inspired adhesion chemistry described here provides a useful alternative to the use of fibrin glues up to a human-level biomedical application.

Hemostatic Needles: Controlling Hemostasis Time by a Catecholamine Oxidative Pathway.

Most infectious human viruses are generally found in the bloodstream after being released by infected organs. Thus, hemorrhage in patients, whose blood contains infectious viruses might be a significant risk for secondary infections. In this work, a self-sealing hemostatic needle that causes no bleeding even after its removal is reported. The materials used for the self-sealing needles are inspired by mussel adhesive polysaccharide, chitosan-catechol, which shows a rapid phase transition from a solid phase (i.e., a thin film) to an adhesive gel upon coming into contact with blood. We found that the self-sealing time for the complete hemostasis depends on the oxidation pathway of the conjugated catechol. For high-temperature oxidation (i.e., 60 °C), Michael addition is a dominant oxidative coupling reaction, which weakens the chitosan-catechol attachment force on the needle surface. Thus, the film is easily transferred to the hemorrhaging sites, with the result that there is no bleeding even after a short injection time (<5 s). In contrast, during low-temperature oxidation (4 °C), Schiff base formation is dominant, which strengthens the film attachment force on the needle surface, resulting in continued bleeding owing to a dearth of tissue transfer after the injection.

Dynamic Bonds between Boronic Acid and Alginate: Hydrogels with Stretchable, Self-Healing, Stimuli-Responsive, Remoldable, and Adhesive Properties.

For the increasing demand of soft materials with wide ranges of applications, hydrogels have been developed exhibiting variety of functions (e.g., stretchable, self-healing, stimuli-responsive, and etc.). So far, add-in components such as inorganic nanoparticles, carbon materials, clays, and many others to main polymers have been used to achieve various unique functions of hydrogels. The multicomponent hydrogel systems often exhibit batch-dependent inconsistent results and problems in multicomponent mixings, require labors during preparations, and accompany unpredictable cross-talk between the added components. Here, we developed 'single polymeric component', alginate-boronic acid (alginate-BA) hydrogel to overcome the aforementioned problems. It exhibits unprecedented multifunctionalities simultaneously, such as high stretchability, self-healing, shear-thinning, pH- and glucose-sensitivities, adhesive properties, and reshaping properties. Multifunctionalities of alginate-BA hydrogel is resulted from the reversible inter- and intramolecular interactions by dynamic equilibrium of boronic acid-diol complexation and dissociation, which was proved by single molecule level Atomic Force Microscopy (AFM) pulling experiments. We also found that the alginate-BA gel showed enhanced in vivo retentions along gastrointestinal (GI) tract. Our findings suggest that rational polymer designs can result in minimizing the number of a participating component for multifunctional hydrogels, instead of increasing complexity by adding various additional components.

Hemostatic Ability of Chitosan-Phosphate Inspired by Coagulation Mechanisms of Platelet Polyphosphates.

Hemostatic materials have been studied to minimize bleeding time. Recently, polyphosphate (polyP) have received attention as potential hemostatic compounds, which are released from activated platelets. Long polyP chains are essential to form thick fibrin clots. Herein, chitosan is functionalized by covalently tethering phosphate groups to mimic polyP. It is hypothesized that utilizing a known hemostatic polysaccharide, chitosan, and tethering phosphate groups to mimic polyP's functionality show synergistic effect in hemostasis. Five different phosphorylated chitosan conjugates (Chi-Ps), s-Chi-7P, s-Chi-28P, s-Chi-74P, is-Chi-29P, and is-Chi-56P are prepared, where "s" indicates water soluble Chi-Ps and "is" represents water insoluble Chi-Ps. Unexpectedly, an important carbon in D-glucosamine is found, which determines chitosan solubility. Phosphate groups conjugated to C6 carbon resulted in water soluble Chi-P, but conjugation to C3 group exhibited water insoluble behavior. Hemostasis capability showed a positive correlation with the degree of phosphate conjugations regardless of water solubility of Chi-P.

Complete prevention of blood loss with self-sealing haemostatic needles.

Bleeding is largely unavoidable following syringe needle puncture of biological tissues and, while inconvenient, this typically causes little or no harm in healthy individuals. However, there are certain circumstances where syringe injections can have more significant side effects, such as uncontrolled bleeding in those with haemophilia, coagulopathy, or the transmission of infectious diseases through contaminated blood. Herein, we present a haemostatic hypodermic needle able to prevent bleeding following tissue puncture. The surface of the needle is coated with partially crosslinked catechol-functionalized chitosan that undergoes a solid-to-gel phase transition in situ to seal punctured tissues. Testing the capabilities of these haemostatic needles, we report complete prevention of blood loss following intravenous and intramuscular injections in animal models, and 100% survival in haemophiliac mice following syringe puncture of the jugular vein. Such self-sealing haemostatic needles and adhesive coatings may therefore help to prevent complications associated with bleeding in more clinical settings.

TAPE: A Biodegradable Hemostatic Glue Inspired by a Ubiquitous Compound in Plants for Surgical Application.

This video describes the simplest protocol for preparing biodegradable surgical glue that has an effective hemostatic ability and greater water-resistant adhesion strength than commercial tissue adhesives. Medical adhesives have attracted great attention as potential alternative tools to sutures and staples due to their convenience in usage with minimal invasiveness. Although there are several protocols for developing tissue adhesives including those commercially available such as fibrin glues and cyanoacrylate-based materials, mostly they require a series of chemical syntheses of organic molecules, or complicated protein-purification methods, in the case of bio-driven materials (i.e., fibrin glue). Also, the development of surgical glues exhibiting high adhesive properties while maintaining biodegradability is still a challenge due to difficulties in achieving good performance in the wet environment of the body. We illustrate a new method to prepare a medical glue, known as TAPE, by the weight-based separation of a water-immiscible supramolecular aggregate formed after a physical mixing of a plant-derived, wet-resistant adhesive molecule, Tannic Acid (TA), and a well-known biopolymer, Poly(Ethylene) glycol (PEG). With our approach, TAPE shows high adhesion strength, which is 2.5-fold more than commercial fibrin glue in the presence of water. Furthermore, TAPE is biodegradable in physiological conditions and can be used as a potent hemostatic glue against tissue bleeding. We expect the widespread use of TAPE in a variety of medical settings and drug delivery applications, such as polymers for muco-adhesion, drug depots, and others.

Tannic Acid as a Degradable Mucoadhesive Compound.

To achieve site-specific delivery of pharmaceuticals, the development of effective mucoadhesive polymers is essential. Thus far, only a few polymers, such as thiolated ones and related variants, have been studied. However, their mucoadhesiveness varies depending on the type of polymer and the degree of chemical functionalization. Furthermore, the chemistry of tethering often requires harsh reaction conditions. Recently, pyrogallol-containing molecules have emerged as good tissue and hemostatic adhesives, but their in vivo mucoadhesive properties have not been demonstrated. Herein, we found that pyrogallol-rich tannic acid (TA) formulated with poly(ethylene glycol) (PEG), named TAPE, exhibits superior mucoadhesive properties. TAPE is prepared by a simple physical mixture of TA and PEG. It remained on esophageal mucus layers for at least several hours (<8 h) after oral feeding. The mucoadhesion originated from intermolecular interaction between the polyphenols of TA and mucin, exhibiting pH dependency. TAPE adhered strongly to mucin in neutral conditions but bound weakly in acidic conditions due to different hydrolysis rates of the ester linkages in TA. Thus, TAPE might be useful as a long-lasting esophageal mucoadhesive composite.

Chitosan-catechol: a polymer with long-lasting mucoadhesive properties.

Numerous mucoadhesive polymers have been exploited for prolonging the residence time of formulated drugs or pharmaceuticals at specific delivery sites. However, it has been difficult to achieve satisfactory mucoadhesive properties. The two major modification strategies such as thiolation or lectin functionalization have been extensively studied, but disulfide bond reversibility in the case of thiolation and the toxicity of lectins have been problems. Thus, approaches for further improvement of mucoadhesive properties need to be developed. With an overwhelming library of mucoadhesive polymers, one practical way to improve mucoadhesion is chemical modification of existing mucoadhesive polymers. In other words, the method is based on utilizing the cooperative effect that might be achieved by chemical tethering of a small adhesive moiety to an available mucoadhesive polymer. Here, we conjugated catechols derived from mussel adhesive proteins to chitosan, which is a widely known mucoadhesive polymer. We demonstrated that the gastrointestinal (GI) tract retention of chitosan-catechol was improved compared to unmodified chitosan, which is due to the formation of irreversible catechol mediated-crosslinking with mucin. The results indicate that catechol modification of mucoadhesive polymers may possibly lead to a new generation of mucoadhesive polymers for mucosal drug delivery.