Comparison of structural and hemostatic properties of the poly-N-acetyl glucosamine Syvek Patch with products containing chitosan

Hemostatic and antimicrobial properties of chitosan-based wound healing dressings: A review

Uncontrolled bleeding and microbial infections pose significant hurdles in wound healing, and the use of specialized functional dressings is pivotal in overcoming these obstacles. Among the various wound dressings currently under investigation, those based on chitosan and its derivatives have garnered significant attention due to their superior biocompatibility, antimicrobial properties, hemostatic capabilities, and healing promoting ability. In this comprehensive review, we initially delve into the hemostatic capabilities of chitosan, elucidating its interactions with blood cells and plasma proteins. We also dissect the intricate antimicrobial mechanisms of chitosan, which operate through both intracellular and extracellular pathways. The centerpiece of this review is the systematic classification of dressings based on chitosan and its derivatives, across various forms, such as hydrogels, sponges, membranes, fibers, and powders. This is followed by an exhaustive analysis of their hemostatic and antibacterial efficacy in wound healing, providing a robust foundation for further research and the advancement of clinical applications in the field.

Marine biomaterials in biomedical nano/micro-systems

Marine resources in unique marine environments provide abundant, cost-effective natural biomaterials with distinct structures, compositions, and biological activities compared to terrestrial species. These marine-derived raw materials, including polysaccharides, natural protein components, fatty acids, and marine minerals, etc., have shown great potential in preparing, stabilizing, or modifying multifunctional nano-/micro-systems and are widely applied in drug delivery, theragnostic, tissue engineering, etc. This review provides a comprehensive summary of the most current marine biomaterial-based nano-/micro-systems developed over the past three years, primarily focusing on therapeutic delivery studies and highlighting their potential to cure a variety of diseases. Specifically, we first provided a detailed introduction to the physicochemical characteristics and biological activities of natural marine biocomponents in their raw state. Furthermore, the assembly processes, potential functionalities of each building block, and a thorough evaluation of the pharmacokinetics and pharmacodynamics of advanced marine biomaterial-based systems and their effects on molecular pathophysiological processes were fully elucidated. Finally, a list of unresolved issues and pivotal challenges of marine-derived biomaterials applications, such as standardized distinction of raw materials, long-term biosafety in vivo, the feasibility of scale-up, etc., was presented. This review is expected to serve as a roadmap for fundamental research and facilitate the rational design of marine biomaterials for diverse emerging applications.

Novel cross-linked polysaccharide-polyelectrolyte hemostatic foam improves survival compared to CombatGauze in swine femoral artery hemorrhage model

BACKGROUND

Uncontrolled hemorrhage is the leading cause of preventable death in combat and civilian trauma. Efficacious hemostatic agents in junctional hemorrhage can quell blood loss and improve survival. We hypothesized that a novel hemostatic foam of starch and chitosan would improve hemostasis, and thereby increase survival in a swine femoral artery hemorrhage model when compared with CombatGauze (CG).

METHODS

A novel hemostatic foam of starch and chitosan was created and modified during the study period. Thirty pigs (four excluded) were assigned to treatment using either foam version 1 (FV1, n = 9) or 2 (FV2, n = 8), or (n = 9) in a standard swine femoral artery hemorrhage model. Animals were observed for 150 minutes. Outcomes assessed included hemostasis, survival, posttreatment blood loss, IV fluid volume, and hemodynamic and laboratory trends.

RESULTS

Hemostasis prior to 150 minutes was similar with 44.4%, 77.8%, and 50% of swine treated with CG, FV1 and FV2, respectively (Kaplan-Meyer and log-rank test [KM-LR] p > 0.05). Survival to 150 minutes was improved in swine treated with FV1 (100%) compared with CG (55.6%) (KM-LR p = 0.02). Survival was similar between FV1 and FV2 (75%) (KM-LR p > 0.05), and between CG and FV2 (KM-LR p > 0.05). Using mixed model for longitudinal data, mean arterial pressure decreased significantly in CG- and FV2-treated swine, while there was no significant change in mean arterial pressure in FV1-treated swine. Trends in lactic acid, hematocrit, platelets, INR, and thrombelastography were more favorable for FV1 compared with CG.

CONCLUSION

In this preclinical study of junctional hemorrhage, survival was improved in swine treated with version 1 of a novel chitosan/starch foam compared with CG. Trends in hemodynamics and laboratory data were also more favorable in the FV1-treated swine. This novel hemostatic foam may be an effective alternative to current hemostatic agents.

Recent advances in biomimetic hemostatic materials

Although the past decade has witnessed unprecedented medical advances, achieving rapid and effective hemostasis remains challenging. Uncontrolled bleeding and wound infections continue to plague healthcare providers, increasing the risk of death. Various types of hemostatic materials are nowadays used during clinical practice but have many limitations, including poor biocompatibility, toxicity and biodegradability. Recently, there has been a burgeoning interest in organisms that stick to objects or produce sticky substances. Indeed, applying biological adhesion properties to hemostatic materials remains an interesting approach. This paper reviews the biological behavior, bionics, and mechanisms related to hemostasis. Furthermore, this paper covers the benefits, challenges and prospects of biomimetic hemostatic materials.

Topical reinforcement of the cervical mucus barrier to sperm

Close to half of the world's pregnancies are still unplanned, reflecting a clear unmet need in contraception. Ideally, a contraceptive would provide the high efficacy of hormonal treatments, without systemic side effects. Here, we studied topical reinforcement of the cervical mucus by chitosan mucoadhesive polymers as a form of female contraceptive. Chitosans larger than 7 kDa effectively cross-linked human ovulatory cervical mucus to prevent sperm penetration in vitro. We then demonstrated in vivo using the ewe as a model that vaginal gels containing chitosan could stop ram sperm at the entrance of the cervical canal and prevent them from reaching the uterus, whereas the same gels without chitosan did not substantially limit sperm migration. Chitosan did not affect sperm motility in vitro or in vivo, suggesting reinforcement of the mucus physical barrier as the primary mechanism of action. The chitosan formulations did not damage or irritate the ewe vaginal epithelium, in contrast to nonoxynol-9 spermicide. The demonstration that cervical mucus can be reinforced topically to create an effective barrier to sperm may therefore form the technological basis for muco-cervical barrier contraceptives with the potential to become an alternative to hormonal contraceptives.

Progress in Research of Chitosan Chemical Modification Technologies and Their Applications

Chitosan, which is derived from chitin, is the only known natural alkaline cationic polymer. Chitosan is a biological material that can significantly improve the living standard of the country. It has excellent properties such as good biodegradability, biocompatibility, and cell affinity, and has excellent biological activities such as antibacterial, antioxidant, and hemostasis. In recent years, the demand has increased significantly in many fields and has huge application potential. Due to the poor water solubility of chitosan, its wide application is limited. However, chemical modification of the chitosan matrix structure can improve its solubility and biological activity, thereby expanding its application range. The review covers the period from 1996 to 2022 and was elaborated by searching Google Scholar, PubMed, Elsevier, ACS publications, MDPI, Web of Science, Springer, and other databases. The various chemical modification methods of chitosan and its main activities and application research progress were reviewed. In general, the modification of chitosan and the application of its derivatives have had great progress, such as various reactions, optimization of conditions, new synthetic routes, and synthesis of various novel multifunctional chitosan derivatives. The chemical properties of modified chitosan are usually better than those of unmodified chitosan, so chitosan derivatives have been widely used and have more promising prospects. This paper aims to explore the latest progress in chitosan chemical modification technologies and analyze the application of chitosan and its derivatives in various fields, including pharmaceuticals and textiles, thus providing a basis for further development and utilization of chitosan.

Molecular modifications, biological activities, and applications of chitosan and derivatives: A recent update

Polysaccharides arouse great interest due to their structure and unique properties, such as biocompatibility, biodegradability, and absence of toxicity. Polysaccharides from marine sources are particularly useful due to the wide variety of applications and biological activities. Chitosan, a deacetylated derivative of chitin, is an example of an interesting bioactive marine-derived polysaccharide. Moreover, a wide variety of chemical modifications and conjugation of chitosan with other bioactive molecules are responsible for improvements in physicochemical properties and biological activities, expanding the range of applications. An overview of the synthetic approaches for preparing chitosan, chitosan derivatives, and conjugates is described and discussed. A recent update of the biological activities and applications in different research fields, mainly focused on the last 5 years, is presented, highlighting current trends.

Mechanochemical Transformations of Biomass into Functional Materials

Biomass is one of the promising alternatives to petroleum-derived materials and plays a major role in our fight against climate change by providing renewable sources of chemicals and materials. Owing to its chemical and structural complexity, the transformation of biomass into value-added products requires a profound understanding of its composition at different scales and innovative methods such as combining physical and chemical processes. In this context, the use of mechanochemistry in biomass valorization is currently growing owing to its potentials as an efficient, sustainable, and environmentally friendly approach. This review highlights the latest advances in the transformation of biomass (i. e., chitin, cellulose, hemicellulose, lignin, and starch) to functional materials using mechanochemical-assisted methods. We focused here on the methodology of biomass processing, influencing factors, and resulting properties with an emphasis on achieving functional materials rather than breaking down the biopolymer chains into smaller molecules. Opportunities and limitations associated this methodology were discussed accordingly for future directions.

Investigation of the Effects of Molecular Parameters on the Hemostatic Properties of Chitosan

Hemorrhea is one of the major problems in war, trauma care, and surgical operation that threaten the life of the injured and patients. As a novel polymeric hemostatic agent, biodegradable chitosan can stop bleeding through a variety of approaches. In this paper, chitosan with various molecular parameters was prepared from chitin as raw material through deacetylation, oxidative degradation, hydrophilic modification, and salt formation reactions. The influence of different polymer parameters on the hemostatic effects of chitosan was investigated by in vitro coagulation time and dynamic coagulation assay. The results showed that when the molecular weights were high (10⁵⁻10⁶) and approximate, the coagulation effect of chitosan improved with a decrease of the deacetylation degree and achieved a prominent level in a moderate degree of deacetylation (68.36%). With the same degree of deacetylation, the higher the molecular weight of chitosan, the better the procoagulant effect. The substituent derivatives and acid salts of chitosan showed significant procoagulant effects, especially the acid salts of chitosan. In addition, the hemostasis mechanism of chitosan with various parameters was preliminarily explored by analyzing the plasma recalcification time (PRT). The efforts in this paper laid a basis for further study of the structure⁻activity relationship and the mechanism of chitosan hemostasis.

Chitosan-Based Composite Materials for Prospective Hemostatic Applications

Effective hemostasis is vital to reduce the pain and mortality of patients, and the research and development of hemostatic materials are prerequisite for effective hemostasis. Chitosan (CS), with good biodegradability, biocompatibility and non-toxicity, has been widely applied in bio-medicine, the chemical industry, the food industry and cosmetics. The excellent hemostatic properties of CS have been extensively studied. As a result, chitosan-based composite hemostatic materials have been emerging. In this review, the hemostatic mechanism of chitosan is briefly discussed, and then the progress of research on chitosan-based composite hemostatic materials with multiple forms such as films, sponges, hydrogels, particles and fibers are introduced. Finally, future perspectives of chitosan-based composite hemostatic materials are given. The objective of this review is to provide a reference for further research and development of effective hemostatic materials.

Design of New-Generation Usable Forms of Topical Haemostatic Agents Containing Chitosan

Designing usable forms of topical haemostatic agents is the most important activity during the design process, resulting in strengthened functional properties of the final medical devices. This study aimed to propose indications for a research programme based on risk management supporting the development of two usable forms of a topical haemostatic agent: chitosan/alginate lyophilized foam and chitosan/alginate impregnated gauze. Both of the usable forms of the topical haemostatic agent, being the main part of the modified combat gauze, were fabricated using the chitosan/alginate complex. Risk analysis is helpful in developing an appropriate research programme, significantly reducing the risk to an acceptable level.

Chitin and chitosan: biopolymers for wound management

Chitin and chitosan are biopolymers with excellent bioactive properties, such as biodegradability, non-toxicity, biocompatibility, haemostatic activity and antimicrobial activity. A wide variety of biomedical applications for chitin and chitin derivatives have been reported, including wound-healing applications. They are reported to promote rapid dermal regeneration and accelerate wound healing. A number of dressing materials based on chitin and chitosan have been developed for the treatment of wounds. Chitin and chitosan with beneficial intrinsic properties and high potential for wound healing are attractive biopolymers for wound management. This review presents an overview of properties, biomedical applications and the role of these biopolymers in wound care.

A comparison of 2 devices for radial artery hemostasis after transradial coronary intervention

BACKGROUND AND OBJECTIVE

Transradial access is an attractive approach for angiography or percutaneous coronary intervention. Different devices have been used to apply pressure locally at the site of arterial entry for achieving hemostasis. The aim of this study was to evaluate the effect of 2 different hemostatic devices on radial artery outcomes after transradial coronary intervention.

SUBJECTS AND METHODS

This study included 600 patients who had undergone transradial coronary intervention who were randomized into 2 groups after the procedure: 300 were treated with a radial compression device (TR Band, Terumo Medical, Tokyo, Japan) (CD group) and the other 300 patients were treated using a chitosan-based pad (Anscare, Daxon, Taoyuan, Taiwan) (CS group). Compression time, major and minor access site bleeding complications, and incidence of radial artery occlusion were recorded.

RESULTS

There were no statistical differences in the baseline clinical characteristics of the patients between the 2 groups. Compression time in the CS group was significantly shorter than that in the CD group (P < .001). Although no major access site bleeding complications were observed in either group, 6 patients in each group experienced minor access site bleeding complications. At the same time, 61 patients in the CD group and 21 patients in the CS group experienced errhysis (20% vs 7%, respectively; P < .001). Early radial artery occlusion (24 hours) occurred in 11.7% of the patients in the CD group and 5.4% of the patients in the CS group (P < .05). Chronic radial artery occlusion (30 days) occurred in 10% of the patients in the CD group and 5% of the patients in the CS group (P < .05).

CONCLUSION

The application of the chitosan-based pad showed better hemostatic efficacy and a lower incidence of radial artery occlusion after transradial coronary intervention compared with the compression device.

Comparison of the Efficiencies of Buffers Containing Ankaferd and Chitosan on Hemostasis in an Experimental Rat Model with Femoral Artery Bleeding

OBJECTIVE

In the first assessment of trauma patients with major vascular injuries, we need effective and rapid-acting homeostatic materials. In this study we compare the efficiencies of Ankaferd Blood Stopper® and a chitosan linear polymer (Celox®) in an experimental rat model with femoral artery bleeding.

MATERIALS AND METHODS

Thirty male Wistar albino rats weighing 200-250 g were divided into 3 groups: control, Ankaferd, and chitosan. The femoral artery and vein were visualized and bleeding was started by an incision. The bleeding time was recorded and categorized as 'bleeding stopped at the second minute', 'bleeding stopped at the fourth minute', and 'unsuccessful' if bleeding continued after the fourth minute.

RESULTS

In the control group, 60% of the bleeding did not stop. In the first 4 min in the Ankaferd group, the bleeding stopped in all rats; only in 1 of the rats in the chitosan group did the bleeding not stop. In stopping the bleeding in the first 4 min, Ankaferd was similar to chitosan but better than the control group; the chitosan group was similar to the control, but the p-value was close to significance.

CONCLUSION

For major arterial bleeding, the main treatment is surgical bleeding control, but outside of the hospital we can use buffers containing Ankaferd and chitosan on the bleeding region. The results of this study should be supported with larger studies. Furthermore, in our study, healthy rats were used. New studies are needed to evaluate the results of hypovolemic and hypotensive cases with major artery bleeding.

Effect of Plasma Sterilization on the Hemostatic Efficacy of a Chitosan Hemostatic Agent in a Rat Model

INTRODUCTION

The United States military has had success with chitosan (CS)-based hemostatic agents to control trauma-induced hemorrhages. Despite the positive reviews, additional physical forms of CS may enhance its hemostatic efficacy. Additionally, standard sterilization techniques may negatively affect the hemostatic efficacy of CS. We studied the effects of a CS-based hemostatic pad, the Clo-Sur P.A.D.™ (Scion Cardio-Vascular, Inc.), on severe femoral vessel bleeding in a rat model. The effects of different sterilization techniques on the bioadhesivity, surface atomic concentrations, and hemostatic efficacy of the P.A.D. were also evaluated.

METHODS

Hemostatic efficacy, bioadhesivity, and surface atomic concentrations of the P.A.D. were evaluated in its unsterilized form, after sterilization with standard e-beam treatment, and after sterilization with one of three types of non-thermal nitrogen plasma: nitrogen gas, air, or nitrous oxide plasma. After standardized puncture of the femoral artery or transection of the femoral vessels, rats were treated with either a CS P.A.D. or gauze pad.

RESULTS

The Clo-Sur P.A.D., regardless of sterilization technique, stopped arterial and mixed arterial/venous bleeding in all cases in <90 s with the time to hemostasis (TTH) significantly less for all P.A.D. treatment groups (P < 0.001; n = 4-5/group) compared to gauze-treated controls (n = 3). E-beam sterilized P.A.D.s consistently showed non-significant trends toward increased TTH and worse hemostasis scores compared to unsterilized and plasma sterilized P.A.D.s. Treating e-beam sterilized P.A.D.s with N2 plasma reverted the hemostatic efficacy to levels equivalent to native, unsterilized PADs.

CONCLUSION

A CS-based hemostatic pad successfully controlled severe bleeding in a rat model with combined e-beam and plasma sterilized P.A.D.s showing the most promising results. Further studies are warranted.

In vitro capacity of different grades of chitosan derivatives to induce platelet adhesion and aggregation

Chitosan-derived hemostatic agents with various formulations may have distinct potential in hemostasis. This study assessed the ability of different grades and forms of chitosan derivatives as hemostatic agents to enhance platelet adhesion and aggregation in vitro. The chitosan derivatives utilized were 2% NO-CMC, 7% NO-CMC (with 0.45 mL collagen), 8% NO-CMC, O-C 52, 5% O-CMC-47, NO-CMC-35, and O-C 53. Samples of chitosan derivatives weighing 5mg were incubated at 37°C with 50 μL of phosphate buffer saline (PBS) (pH 7.4) for 60 min. The morphological features of the platelets upon adherence to the chitosan were viewed using scanning electron microscope (SEM), and the platelet count was analyzed with an Automated Hematology Analyzer. For platelet aggregation, we added an adenosine diphosphate (ADP) agonist to induce the chitosan-adhered platelets. O-C 52 bound with platelets exhibited platelet aggregates and clumps on the surface of the membrane layer with approximately 70-80% coverage. A statistically significant correlation (p<0.01) for the platelet count was identified between the baseline value and the values at 10 min and 20 min. The results indicate that O-C 53 and O-C 52 were able to promote clotting have the potential to induce the release of platelets engaged in the process of hemostasis.

Poly-N-acetyl glucosamine fibers accelerate hemostasis in patients treated with antiplatelet drugs

BACKGROUND

Nanofibers consisting of poly-N-acetyl glucosamine (pGlcNAc), as the functional component of products for surface hemostasis, have been shown to activate platelets and thereby the clotting mechanism. The nanofiber-activated platelets provide a catalytic surface for acceleration of the intrinsic coagulation cascade, thrombin generation, and fibrin polymerization.

METHODS

Thromboelastographic analysis was undertaken to study the role of the pGlcNAc nanofibers in platelet activation and acceleration of fibrin polymerization. Thromboelastographic studies were performed without added activators of coagulation.

RESULTS

The pGlcNAc nanofibers were found to accelerate fibrin polymerization in whole blood and platelet-rich plasma. Treatment with eptifibatide (an inhibitor of the platelet GPIIbIIIa receptor) and corn trypsin inhibitor inhibited clotting of whole blood and platelet-rich plasma. The inhibition was reversed by treatment with pGlcNAc nanofibers. Inhibition was not observed after treatment with aspirin alone, MRS2359 (platelet ADP receptor inhibitor), or by a combination of aspirin and MRS2359. The pGlcNAc nanofibers accelerate clotting in normal blood treated with aspirin and MRS2359. Clopidogrel (Plavix) and aspirin did not affect the kinetics of pGlcNAc-mediated fibrin polymerization in blood from patients treated with antiplatelet drugs compared with nontreated blood.

CONCLUSIONS

These results provide evidence that pGlcNAc nanofibers activate platelets and accelerate the clotting of blood, and on how best to achieve surface hemostasis when patients are coagulopathic because of shock and/or to treatment with antiplatelet drugs.

Poly-N-acetylglucosamine fibers amplify the effectiveness of recombinant factor VIIA on clot formation in hemophilia B canine blood

BACKGROUND

Achieving hemostasis in anticoagulated patients is an increasingly important clinical issue. Poly-N-acetylglucosamine (pGlcNAc) nanofibers activate platelets by β3 subunit (CD61) and the von Willebrand receptor GP1b (CD42b) integrin signaling for generation of a prothrombotic surface membrane. Recombinant coagulation factor VIIa (rFVIIa) functions in hemophilia A and B by catalyzing formation of the Xa/Va complex on the surface of activated platelets. These observations suggest that pGlcNAc nanofibers may amplify the activity of rFVIIa in hemophilic blood.

METHODS

The activity of rFVIIa on platelets was tested by performing thromboelastographic analysis with blood from hemophilia B dogs in the presence of pGlcNAc nanofibers and increasing concentrations of rFVIIa. Mechanisms for hemostatic system activation were investigated with inhibitors of tissue factor, factor XIIa, and platelet function.

RESULTS

Recombinant FVIIa was observed to partially restore the ability of the hemophiliac blood to form fibrin clots in a dose-dependent manner with thromboelastographic analysis. The addition of pGlcNAc nanofibers amplified the rFVIIa effect. The activity of rFVIIa and the amplification effect of pGlcNAc were dependent on platelet integrin function but independent of FXIIa and tissue factor activities.

CONCLUSIONS

The pGlcNAc nanofibers amplify rFVIIa activity in hemophilia B canine blood by activating platelets through integrin-dependent mechanisms.

Poly-N-acetyl glucosamine fibers activate bone regeneration in a rabbit femur injury model

BACKGROUND

The purpose of this study was to evaluate the ability of a membrane material, consisting only of short poly-N-acetyl glucosamine (sNAG) nanofibers, to regenerate bone tissue after implantation into circular holes in the rabbit femur.

METHODS

Three circular holes were created in the femurs of five male New Zealand white rabbits. The holes were ∼ 2.0 mm in diameter. Three holes in the left femur were implanted with the comparative control substance (Bone Wax; Ethicon, Inc.); three holes in the right femur were implanted with the sNAG membrane test article. Animals were killed 4 weeks after surgery, and macroscopic evaluation of the implant sites was made. Hematoxylin and eosin histology was performed on both control and test sites.

RESULTS

All control (bone wax) sites had visible holes (defects) at the 28-day end point of the study and showed no evidence of new bone formation. All the 15 sNAG test sites were found to have new bone tissue present in the bone hole defects. Hematoxylin and eosin histology of the sNAG-treated test sites showed the presence of osteoblasts, osteocytes, and trabecula of new bone formation at the 28-day end point of the study.

CONCLUSIONS

The sNAG membrane test material activated the regeneration of new bone tissue in a rabbit femur bone model after 28 days of implantation, whereas the control bone wax material did not.

Heparin-conjugated scaffolds with pore structure of inverted colloidal crystals for cartilage regeneration

A uniform de novo production of neocartilage is a critical issue in the fabrication of tissue-engineered diarthrodial substitutes. The aim of this work is to develop homogeneous chondrogenesis in heparinized scaffolds with pores of inverted colloidal crystal (ICC) geometry. Monodispersed polystyrene microspheres were self-assembled by floating in the medium containing ethylene glycol, dried, annealed and infiltrated with heparin/chitin/chitosan gels. The results indicated that the colloidal template was in a structure of hexagonal arrays. In addition, the regularity of the organized pores in the scaffolds reduced when the concentration of ethylene glycol decreased. An increase in the weight percentage of heparin enhanced the viability of bovine knee chondrocytes (BKCs) in ICC matrices. Over 4 weeks of cultivation, the amount of cartilaginous components including BKCs, glycosaminoglycans (GAGs) and collagen enhanced with time. Moreover, an increase in the weight percentage of heparin promoted the production of BKCs, GAGs and collagen in ICC constructs. Histological and immunochemical staining of the cultured ICC constructs revealed minor differences in BKCs, GAGs and type II collagen between the peripheral and core regions. Therefore, the ordered pores in the heparinized ICC constructs could favor the chondrocyte culture to regenerate a uniform distribution of cartilage.

Poly-N-acetyl glucosamine gel matrix as a non-viral delivery vector for DNA-based vaccination

Intramuscular administration of plasmid DNA vaccines is one of the main delivery approaches that can generate antigen specific T cell responses. However, major limitations of the intramuscular delivery strategy are the low level of myocyte transfection, resulting in a minimal level of protein expression; the inability to directly target antigen presenting cells, in particular dendritic cells, which are critical for establishment of efficacious antigen-specific immune responses. Although several viral vectors have been designed to improve plasmid DNA delivery, they have limitations, including the generation of neutralizing antibodies in addition to lacking the simplicity and versatility required for universal clinical application. We have developed an inexpensive non-viral delivery vector based on the polysaccharide polymer poly-N-acetyl glucosamine with the capability to target dendritic cells. This vector is fully biocompatible, biodegradable, and nontoxic. The advantage of the application of this delivery system relative to other approaches is discussed.

Technologic innovations in neuroendoscopic surgery

Neuroendoscopic surgery encompasses minimally invasive approaches to the skull base using endoscopic techniques. There are unique technologic challenges with endoscopic endonasal skull base surgery, such as a limited working space, difficulty in visualization and identification of neurovascular structures and removal of tissue, hemostasis, and dural reconstruction. Technologic advances that have enabled this surgery include specialized operating suites, neurophysiologic monitoring, imaging and visualization technologies, dissection instrumentation, hemostatic materials, and reconstructive materials. Advances in each of these areas and the needs and challenges of the future of neuroendoscopic surgery are discussed.

Use of a modified chitosan dressing in a hypothermic coagulopathic grade V liver injury model

BACKGROUND

Exsanguination from hepatic trauma is exacerbated by the lethal triad of acidosis, coagulopathy, and hypothermia. We evaluated the application of a modified chitosan dressing in a hypothermic coagulopathic model of grade V liver injury.

METHODS

Subject swine underwent induced hypothermic coagulopathy followed by standardized grade V liver injuries. A modified chitosan dressing was applied and compared with standard packing.

RESULTS

Pretreatment temperature, activated clotting time, and blood loss were similar between groups. Post treatment blood loss was significantly less and resuscitation mean arterial pressure were significantly greater in the modified chitosan group (P < .0001 and P < .018, respectively). Mean fluid resuscitative volume was significantly less in the modified chitosan group (P < .0056). Hemostasis was achieved on average 5.2 minutes following modified chitosan and never achieved with standard packing. At 1 hour post injury, all treatment animals survived compared with half of controls.

CONCLUSIONS

Modified chitosan dressings provide simple rapid treatment of life-threatening liver injuries.

Differential effect of materials for surface hemostasis on red blood cell morphology

The design of devices for surface (topical) hemostasis has been based on maximizing activation of platelets and accelerating coagulation pathways. The studies reported herein examine another aspect of blood contact with topical hemostasis materials, i.e., surface binding of red blood cells (RBCs) and related alterations in RBC morphology. Whole blood was allowed to contact poly-N-acetyl glucosamine (pGlcNAc) containing materials: pGlcNAc nanofibers with parallel polymer alignment (beta-pGlcNAc), chitin, and chitosan. The effect on RBC morphology and function via contact with the artificial surfaces on the cell's morphology was examined with scanning and transmission electron microscopy (TEM). beta-pGlcNAc was found to densely bind RBCs and induce a stomatocytic-like morphology. Chitin and chitosan also bound RBCs, but with approximately 10-fold lower levels and with less distinct general morphologies. beta-pGlcNAc is thus unique in the nature of its interaction with RBCs. These studies indicate that the differential ability of various materials to bind and alter the morphology of RBCs at the artificial surface interface with blood is an important consideration in the design of devices for surface hemostasis.

Topical haemostatic agents

BACKGROUND

A variety of local haemostatic agents is now available to stop troublesome bleeding. These agents are indicated for use during surgical interventions where conventional methods of haemostasis are not applicable because of the site of surgery or the degree of bleeding.

METHOD

A literature search using the PubMed and ISI Web of Knowledge databases identified relevant studies on topical haemostatic agents. Manufacturers' recommendations were also sought through commercial websites.

RESULTS AND CONCLUSION

A significant body of evidence now exists to support the use of topical haemostatic agents in a wide variety of clinical situations. The advantages and disadvantages of many of these agents are highlighted.

Effects of poly-N-acetyl glucosamine (pGlcNAc) patch on wound healing in db/db mouse

BACKGROUND

Poly-N-acetyl glucosamine (pGlcNAc) nanofiber-based materials, produced by a marine microalga, have been characterized as effective hemostatic agents. In this study, we hypothesized that a pGlcNAc fiber patch may enhance wound healing in the db/db mouse.

METHODS

pGlcNAc patches were applied on 1-cm, full-thickness, skin wounds in the db/db mouse model. Wounds (n = 15 per group) were dressed with a pGlcNAc nanofiber patch for 1 hour, 24 hours, or left untreated. After the application time, patches were removed and wounds were allowed to heal spontaneously. The rate of wound closure was evaluated by digital analysis of unclosed wound area as a function of time. At day 10, wounds (n = 7 per group) were harvested and quantified with immunohistochemical markers of proliferation (Ki-67) and vascularization (platelet endothelial cell adhesion molecule).

RESULTS

Wounds dressed with pGlcNAc patches for 1 hour closed faster than control wounds, reaching 90% closure in 16.6 days, 9 days faster than untreated wounds. Granulation tissue showed higher levels of proliferation and vascularization after 1-hour treatment than the 24-hour and left-untreated groups. Foreign body reaction to the material was not noted in applications up to 24 hours.

DISCUSSION

In addition to its hemostatic properties, the pGlcNAc material also appears to accelerate wound closure in healing-impaired genetically diabetic mice. This material, with its combination of hemostatic and wound healing properties, has the potential to be effective agent for the treatment of complicated wounds.

Hemostatic properties of glucosamine-based materials

Glucosamine- and N-acetyl glucosamine-containing polymers are being used in an increasing number of biomedical applications, including in products for surface (topical) hemostasis. The studies presented here investigate the relationship between the structure (conformation) and function (activation of hemostasis) of glucosamine-based materials. Several polymer systems were studied, including fibers isolated from a microalgal source containing poly-N-acetyl glucosamine polymers that are organized in a parallel, hydrogen-bonded tertiary structure and can be chemically modified to an antiparallel orientation; and gel formulation derivatives of the microalgal fibers consisting of partially deacetylated (F2 gel) and fully deacetylated (F3 gel) polymers. Comparison of the properties of the poly-N-acetyl glucosamine fiber-derived materials with chitin, chitosan, and commercial chitosan-based products are presented. Several studies were performed with the glucosamine-based materials, including (1) an analysis of the ability of materials to activate platelets and turnover of the intrinsic coagulation cascade, (2) an examination of the viscoelastic properties of mixtures of platelet-rich plasma and the glucosamine-based materials via thromboelastography, and (3) scanning electron microscopic studies to examine the morphology of the glucosamine-based materials. The results presented demonstrate that hemostatic responses to the glucosamine-based materials studied are highly dependent on their chemical nature and tertiary/quaternary structure. The unique natural microalgal fibers were found to have strongly prohemostatic activity compared to the other materials studied.

Randomized controlled trial of topical hemostasis pad use for achieving vascular hemostasis following percutaneous coronary intervention

OBJECTIVES

We conducted a randomized trial to determine the efficacy of two topical hemostasis pads in promoting vascular hemostasis following PCI, and to assess the appropriate level of anticoagulation for sheath removal.

BACKGROUND

Pads coated with procoagulant materials are widely marketed and used to augment vascular hemostasis following PCI, yet clinical effectiveness and safety data are lacking.

METHODS

184 patients who underwent PCI using the femoral approach were randomized to one of four methods of sheath removal: (1) at ACT < 250 using the Chito-Seal pad; (2) at ACT < 250 using the Clo-Sur PAD; (3) at ACT < 250 using manual compression alone; (4) at ACT < 170 using manual compression alone.

RESULTS

Time to hemostasis was significantly shorter in the hemostasis pad groups compared to the conventional compression groups (16.2 +/- 4.9, 16.0 +/- 5.3, 19.3 +/- 7.8, and 18.3 +/- 5.7 min, respectively, P = 0.027), however overall bed rest times following intervention were not reduced by use of either hemostasis pad. The incidence of major or minor bleeding complications did not differ among groups. Irrespective of hemostasis pad use, removal of sheaths at higher ACT levels allowed shorter time to ambulation following PCI without an increase in bleeding events.

CONCLUSIONS

The hemostasis pads tested shortened time to hemostasis compared to standard manual compression, although the absolute reduction in time to hemostasis was relatively small and did not translate into a reduction in overall bed rest time. Independent of hemostasis pad use, removal of arterial sheaths at higher than conventional activated clotting times was safe and resulted in significant reductions in time to ambulation.

Vascular Closure Devices

This article summarizes the vascular closure device technologies that are available to physicians who perform percutaneous catheter-based procedures.

A Salmon Thrombin-Fibrin Bandage Controls Arterial Bleeding in a Swine Aortotomy Model

BACKGROUND

Recently, a wide variety of bandages have been formulated to attempt to improve the effectiveness of emergency intervention in situations of uncontrolled bleeding. The best of these dressings contain a mixture of human thrombin and fibrinogen. The presence of human components in these bandages, although effective, increases the cost of the dressing and raises questions of availability of raw materials and transmission of pathogens. The purpose of this study was to investigate the efficacy of dressings composed of salmon thrombin and fibrinogen in a swine aortotomy model.

METHODS

A 4.4-mm aortotomy was produced in the abdominal aorta of 19 anesthetized, splenectomized swine. The United States Army standard field gauze was applied to 8 animals, and the salmon thrombin-fibrin dressing (SFD) was applied to 11 animals. Survival, blood loss, and other parameters were measured over a 60-minute period.

RESULTS

All 11 animals that received the SFD survived the aortotomy injury, and bleeding stopped within 7.5 +/- 1.5 min. Seven of 8 animals in the control group were killed when bleeding continued and blood pressures decreased to the cutoff values as outlined in the animal protocol. Bleeding was significantly less in the SFD group compared with the gauze group (241 +/- 65.3 vs. 932.7 +/- 142.4 mL).

CONCLUSION

Fibrin dressing using salmon-derived thrombin and fibrinogen is effective in controlling severe, uncontrolled bleeding. This dressing may offer an alternative to dressings composed of human coagulation proteins.

The Safety and Efficacy of a Percutaneous Closure Device in Patients Undergoing Uterine Artery Embolization

PURPOSE

The use of suture-mediated closure devices (SMCDs) in patients undergoing uterine artery embolization (UAE) for symptomatic leiomyomata is controversial. With recent literature suggesting a higher complication rate with the use of SMCDs, their use in this specific population has been questioned. The purpose of this study is to assess the safety and efficacy of SMCDs specifically for those patients undergoing UAE for symptomatic uterine leiomyomata.

MATERIALS AND METHODS

A prospective database was established in a single high-volume medical center for patients undergoing UAE for symptomatic leiomyomata. Data were tracked prospectively, with technical outcome and complication rates serving as endpoints.

RESULTS

UAE was performed in 342 consecutive patients from January 2001 to September 2003. The SMCD was used in 328 of these patients (96%). Successful primary hemostasis was achieved in 320 of 328 patients (97%), with additional manual compression required in the remaining eight patients (3%). No major complications were observed. Minor complications consisted of minor hematomas in four women (1%) and anteriomedial thigh pain in 68 women (21%) within 1 month of follow-up, resulting in an overall complication rate of 22%. All symptoms related to anteromedial thigh pain ipsilateral to the arterial puncture site were managed conservatively with 1 week of oral nonsteroidal antiinflammatory medication.

CONCLUSION

The SMCD provided safe and effective hemostasis in patients undergoing UAE. Transient thigh discomfort, which may result from irritation of the anterior femoral cutaneous nerves (femoral neuralgia syndrome), was uniformly relieved with nonsteroidal antiinflammatory therapy.

Poly-N-acetyl glucosamine-mediated red blood cell interactions

BACKGROUND

Investigations were performed to assess the effect of poly-N-acetyl glucosamine (p-GlcNAc) fiber slurry-mediated hemostasis by interactions with red blood cells.

METHODS

Red blood cell aggregation studies were performed using test material-coated microscope slides and multiphoton microscopic measurements. Enzymatic removal of red blood cell surface proteins was achieved using trypsin and neuraminidase treatment. Zeta-potential measurements (surface charge) were performed.

RESULTS

Red blood cells interact directly with poly-N-acetyl glucosamine polymers through ionic interactions and cell-surface proteins. The effective concentration of poly-N-acetyl glucosamine fiber material for 50% red blood cell aggregation was 0.28 mg/mL. The p-GlcNAc beta-configuration fibers and an alpha-configuration structural modification of the fibers both produced maximal responses because of their zeta-potentials, whereas other chemically modified p-GlcNAcs and chitosans were ineffective.

CONCLUSION

Poly-N-acetyl glucosamine-induced red blood cell aggregation is mediated by interactions with red blood cell surface charges.

Comparison of poly-N-acetyl glucosamine with commercially available topical hemostats for achieving hemostasis in coagulopathic models of splenic hemorrhage

BACKGROUND

The hemostatic quality of the poly-N-acetyl glucosamine (p-GlcNAc) patch was compared with a fibrin sealant, fibrin bandage, and cellulose patch.

METHODS

A 2 x 2-cm capsular strip to a depth of 3 mm of the swine spleen was used as a source of bleeding. Splenic lacerations were created in hemophilia B dogs and treated with p-GlcNAc and Surgicel. Wounds were created in rabbits and treated with p-GlcNAc at 37degreesC and after keeping body core temperature at 29degreesC.

RESULTS

Poly-N-acetyl glucosamine was able to achieve hemostasis with greater efficacy than either of the fibrin-based bandages. In the hemophilia B dog study, p-GlcNAc significantly outperformed Surgicel, with p-GlcNAc achieving hemostasis in 75% of the treated wounds compared with 17% for the cellulose patch. The hypothermia study demonstrated that p-GlcNAc is equally effective at 29degreesC and at 37degreesC.

CONCLUSION

Poly-N-acetyl glucosamine was effective at controlling bleeding in animals with experimentally induced or genetic coagulopathic disorders.

Isolation, Purification, and Characterization of Poly-N-Acetyl Glucosamine Use as a Hemostatic Agent

BACKGROUND

A new polymeric material, poly-N-acetyl glucosamine (p-GlcNAc) fiber, has been identified and is effective in achieving hemostasis in surgical procedures and trauma. The p-GlcNAc material is purified from large-scale cultures of a marine microalga.

METHODS

Poly-N-acetyl glucosamine materials have been formulated as films, sponges, gels, and microspheres. The polymer's structure has been characterized by chemical composition, carbohydrate analysis, spectroscopic techniques, intrinsic viscosity, and electron microscopy.

RESULTS

Carbohydrate analyses indicate that the primary sugar present in p-GlcNAc is N-acetyl glucosamine. Elemental analyses yield percentage values for carbon, nitrogen, and hydrogen that support that the polymer is fully acetylated. Molecular weight determinations indicate that the polymer has a molecular weight of 2.0 x 10(6) Da. Fourier transform infrared, nuclear magnetic resonance, and circular dichroism spectral data have defined a unique tertiary structure. Biologic testing demonstrated that p-GlcNAc materials are fully biocompatible.

CONCLUSION

The p-GlcNAc fiber has a unique beta-tertiary structure.