Host-guest composites for induced hemostasis and therapeutic healing in traumatic injuries

Nanoengineered and highly porous 3D chitosan-graphene scaffold for enhanced antibacterial activity and rapid hemostasis

Chitosan-based hydrogels have been utilized over the years as an efficient hemorrhage because of their biocompatibility and biodegradability nature. Here we have nanoengineered the polycationic peptide-conjugated graphene‑silver nanocomposite into the chitosan matrix as a 3D highly porous CGrSP scaffold to facilitate rapid hemostasis and prevent bacterial infection. This CGrSP scaffold interacted with blood cells and platelets, initiating the blood coagulation process by activating the plasmatic contact system. Notably, it reduced the activated Partial Thromboplastin Time (aPTT) and Prothrombin Time (PT), indicating that the scaffold promoted platelet activation associated with Factors XII and X, leading to fibrin formation and clot stabilization. In vitro studies showed that the CGrSP scaffold reduced whole blood clotting time by 87 % compared to the commercial dressing "QuikClot." Additionally, in vivo studies using rat-tail amputation and skin laceration models demonstrated a significant reduction in hemostatic time compared to both the chitosan scaffold (p-value<0.003) and "QuikClot" (p-value<0.01). Beyond its hemostatic properties, the CGrSP scaffold exhibited strong antibacterial activity, achieving a 5-log reduction against both Escherichia coli and Staphylococcus aureus. With its biodegradable nature, rapid hemostasis, and potential for tissue regeneration, the CGrSP scaffold presents a novel and safe therapeutic material.

Mesoporous Bioactive Glass-Graphene Oxide Composite Aerogel with Effective Hemostatic and Antibacterial Activities

Hemorrhage and infection after emergency trauma are two main factors that cause deaths. It is of great importance to instantly stop bleeding and proceed with antibacterial treatment for saving lives. However, there is still a huge need and challenge to develop materials with functions of both rapid hemostasis and effective antibacterial therapy. Herein, we propose the fabrication of a composite aerogel mainly consisting of mesoporous bioactive glass (MBG) and graphene oxide (GO) through freeze-drying. This composite aerogel has a three-dimensional porous structure, high absorption, good hydrophilicity, and negative zeta potential. Moreover, it exhibits satisfactory hemostatic activities including low BCI, good hemocompatibility, and activation of intrinsic pathways. When applied to rat liver injury bleeding, it can decrease 60% hemostasis time and 75% blood loss amount compared to medical gauze. On the other hand, the composite aerogel shows excellent photothermal antibacterial capacity against Staphylococcus aureus and Escherichia coli. Animal experiments further verify that this composite aerogel can effectively kill bacteria in wound sites via photothermal treatment and promote wound healing. Hence, this MBG-GO composite aerogel makes a great choice for the therapy of emergency trauma with massive hemorrhage and bacterial infection.

High-Efficiency Antibacterial Hemostatic AgNP@Zeolite/Chitin/Bamboo Composite Sponge for Wound Healing without Heat Injury

Chitin is a popular hemostatic material, but there are still many deficiencies in its ability to effectively stop bleeding, prevent infection, and fit wounds. Herein, AgNP@zeolite/chitin/bamboo (AgZ-CB) composite sponges with shape recovery are prepared to minimize blood loss, kill bacteria, and promote wound healing. Notably, the bamboo powder is used for the first time to remarkably enhance the softness of the composite sponge (volumetric expansion ratio >5). The fabricated AgZ-CB sponge exhibits an excellent killing effect (≈100% bactericidal rate) against both Escherichia coli and Staphylococcus aureus and activates internal and external coagulation pathways to accelerate hemostasis without causing thermal damage (≈5 °C temperature difference). Moreover, the AgZ-CB sponge shows less blood loss (26 mg) and a shorter time to hemostasis (42 s) than the commercial polyvinyl formal sponge (84 mg and 76 s) in the full-thickness liver injury model. The in vivo wound healing and biodegradation experiment indicate that AgZ-CB with excellent biocompatibility can close wounds efficiently. Overall, the AgZ-CB sponge has great potential in combating a series of obstacles in wound healing.

Zeolites as Ingredients of Medicinal Products

Development of new medicinal products for particular therapeutic treatment or for better manipulations with better quality and less side effects are possible as a result of advanced inorganic and organic materials application, among which zeolites, due to their properties and versatility, have been gaining attention. This paper is an overview of the development in the use of zeolite materials and their composites and modifications as medicinal products for several purposes such as active agents, carriers, for topical treatments, oral formulations, anticancer, the composition of theragnostic systems, vaccines, parenteral dosage forms, tissue engineering, etc. The objective of this review is to explore the main properties of zeolites and associate them with their drug interaction, mainly addressing the advances and studies related to the use of zeolites for different types of treatments due to their zeolite characteristics such as molecule storage capacity, physical and chemical stability, cation exchange capacity, and possibility of functionalization. The use of computational tools to predict the drug-zeolite interaction is also explored. As conclusion was possible to realize the possibilities and versatility of zeolite applications as being able to act in several aspects of medicinal products.

A cysteine enzyme hemostat for efficient heparin-tolerant blood coagulation

It is challenging to stop bleeding effectively in patients treated with heparin which leads to enhanced risk of uncontrolled bleeding during operation. Herein, we report an easy-to-use and heparin-tolerant hemostatic agent based on a thrombin-like cysteine enzyme (papain), which catalyzes the hydrolysis of fibrinogen and cross-linking of fibrin clots. A papain-based hemostat with increased procoagulant activity is developed through immobilizing papain on the cellulose carrier, which displays short clotting time in both normal and heparinized plasmas. The excellent hemostatic performance of the papain-based hemostat is further confirmed with reduced hemostatic time and limited blood loss in a mouse tail amputation model, rabbit auricular artery injury model and rat liver injury model, in which a natural coagulation system fails to function on account of heparin. This bio-hemostat has great potential to reverse the effect of heparin and stop topical hemorrhage rapidly in surgical procedures.

Inorganic-based biomaterials for rapid hemostasis and wound healing

The challenge for the treatment of severe traumas poses an urgent clinical need for the development of biomaterials to achieve rapid hemostasis and wound healing. In the past few decades, active inorganic components and their derived composites have become potential clinical products owing to their excellent performances in the process of hemorrhage control and tissue repair. In this review, we provide a current overview of the development of inorganic-based biomaterials used for hemostasis and wound healing. We highlight the methods and strategies for the design of inorganic-based biomaterials, including 3D printing, freeze-drying, electrospinning and vacuum filtration. Importantly, inorganic-based biomaterials for rapid hemostasis and wound healing are presented, and we divide them into several categories according to different chemistry and forms and further discuss their properties, therapeutic mechanisms and applications. Finally, the conclusions and future prospects are suggested for the development of novel inorganic-based biomaterials in the field of rapid hemostasis and wound healing.

The complex hydrogel based on diatom biosilica and hydroxybutyl chitosan for wound healing

In this study, doxycycline (DOXY)-loaded diatom biosilica (DBs) were developed and coated with hydroxybutyl chitosan (HBC) hydrogel for wound healing. The HBC/DBs/DOXY composite hydrogel had significant inhibitory activity against S. aureus (100%) and E. coli (98%). In addition, the HBC/DBs/DOXY hydrogel showed minimum cytotoxicity on L929 cells in vitro, indicating the great biocompatibility of the composite hydrogel. The in vivo results demonstrated that HBC/DBs/DOXY composite hydrogel could promote the wound re-epithelialization and accelerate the healing. The wound closure was evaluated to be 99.4 ± 0.4% at day 12 after treated with the hydrogel, with the presence of neovascularization and collagen deposition, all indicating the great potential of HBC/DBs/DOXY hydrogel in wound healing.

Mesopore Controls the Responses of Blood Clot-Immune Complex via Modulating Fibrin Network

Formation of blood clots, particularly the fibrin network and fibrin network-mediated early inflammatory responses, plays a critical role in determining the eventual tissue repair or regeneration following an injury. Owing to the potential role of fibrin network in mediating clot-immune responses, it is of great importance to determine whether clot-immune responses can be regulated via modulating the parameters of fibrin network. Since the diameter of D-terminal of a fibrinogen molecule is 9 nm, four different pore sizes (2, 8, 14, and 20 nm) are rationally selected to design mesoporous silica to control the fibrinogen adsorption and modulate the subsequent fibrin formation process. The fiber becomes thinner and the contact area with macrophages decreases when the pore diameters of mesoporous silica are greater than 9 nm. Importantly, these thinner fibers grown in pores with diameters larger than 9 nm inhibit the M1-polorazation of macrophages and reduce the productions of pro-inflammatory cytokines and chemokines by macrophages. These thinner fibers reduce inflammation of macrophages through a potential signaling pathway of cell adhesion-cytoskeleton assembly-inflammatory responses. Thus, the successful regulation of the clot-immune responses via tuning of the mesoporous pore sizes indicates the feasibility of developing advanced clot-immune regulatory materials.

Biomimetic hydroxyapate/polydopamine composites with good biocompatibility and efficiency for uncontrolled bleeding

Uncontrolled bleeding is thought to be the most deadly cause of pre-hospital, traffic, and military accidents death. However, the popular commercial hemostats can only realize the hemostasis of mild bleeding. Therefore, we developed polydopamine (PDA) composite materials (PMs), which applied hydroxyapatite as the parent body. The PMs were produced via lyophilization and functionalized with amino, phenol hydroxyls groups, which endowed hydrophobicity to materials. This ensured a high aggregation ability of blood cells to the PMs and they were tested to be as high as 300% compared with the negative control group. The clotting time was shortened to 79.7% compared with the usually used commercial hemostat (Celox) in the test of in vitro hemostasis. Through the results of PT and APTT tests, blood coagulation index test, and the analysis of intracellular Ca²⁺ activation, we further understood the mechanism of the hemostasis of the materials, which explained the low blood loss and quick coagulation time of the PM hemostats in detail. Besides, the low hemolysis and cytotoxicity of the PMs suggested the good biocompatibility of the hemostats, which was further proved by the regular morphology maintained by erythrocytes in the hemolysis tests. The study of nanoscale composites led the research for the methods of hemostasis.

Tentative identification of key factors determining the hemostatic efficiency of diatom frustule

It is increasingly essential to develop excellent materials for rapid hemorrhage control. Our previous study showed that centric diatoms such as frustules were superior to QuikClot® in hemostasis, however, related studies in pennate diatoms are still scarce. The morphological and physicochemical properties of pennate diatoms are quite different from those of centric diatoms, meaning that significant differences may also be observed from their hemostatic effects. Thus, the hemostasis effects of four pennate diatom frustules (Cocconeiopsis orthoneoides, Navicula avium, Navicula sp., and Pleurosigma indicum) were investigated in this study. Herein, all diatom frustules demonstrated outstanding hemostasis performance. For example, the in vitro coagulation time of C. orthoneoides (100.33 ± 9.5 s) was 32.4% lower than that of QuikClot®. Meanwhile, the hemostatic times of C. orthoneoides in the rat tail amputation and femoral artery models were 82 s and 180 s, respectively, only around one-half and one-third of the QuikClot® values. Moreover, the blood loss amounts of C. orthoneoides in the rat tail amputation and femoral artery model were 73.4% and 61% less than that of QuikClot®. Besides that, diatom frustules also exhibited favorable biocompatibility (hemolysis ratio <5%, MEFs cell viabilities >80%, and no inflammation). To find out the key factors underlying the hemostatic effect of frustules, Pearson correlation analysis was further performed in this study. The results demonstrated that the coagulation reaction time (R) was negatively correlated with the specific surface area and liquid absorbability but positively with the diatom pore diameter. The angle α, indicating the clot formation rate, was negative to the diatom size and pore diameter. Additionally, MA also showed a negative correlation with the BET value. This study can enrich our knowledge about the application potential of diatoms in the field of bleeding control and is helpful in deepening our understanding about the hemostatic mechanism of frustules.

Chitosan/Diatom-Biosilica Aerogel with Controlled Porous Structure for Rapid Hemostasis

Uncontrolled hemorrhage is the main reason of possible preventable death after accidental injury. It is necessary to develop a hemostatic agent with rapid hemostatic performance and good biocompatibility. In this study, a chitosan/diatom-biosilica-based aerogel is developed using dopamine as cross-linker by simple alkaline precipitation and tert-butyl alcohol replacement. The chitosan/diatom-biosilica aerogel exhibits favorable biocompatibility and multiscale hierarchical porous structure (from nanometer to micrometer), which can be controlled by the concentration of tert-butyl alcohol. The displacement of tert-butyl alcohol can keep the porosity of diatom-biosilica in aerogel and give it large surface with efficient water absorption ratio. 30% tert-butyl alcohol replacement of aerogel possesses the largest surface area (74.441 m² g^-1 ), water absorption capacity (316.83 ± 2.04%), and excellent hemostatic performance in vitro blood coagulation (≈70 s). Furthermore, this aerogel exhibits the shortest clotting time and lowest blood loss in rat hemorrhage model. The strong interface effect between aerogel and blood is able to promote erythrocytes aggregation, platelets adhesion, and activation, as well as, activate the intrinsic coagulation pathway to accelerate blood coagulation. All the above results demonstrate that chitosan/diatom-biosilica aerogel has great potential to be a safe and rapid hemostatic material.

Natural Inorganic Ingredients in Wound Healing

Background:

One of the major clinical challenges is to achieve a rapid and efficient treatment of complex chronic wounds. Nowadays, most wound dressings currently available are unable to find a solution the challenges of resistance to bacterial infection, protein adsorption and increased levels of exudates. Natural inorganic ingredients (clay minerals, metal cations, zeolites, etc) could be the key to solve the problem satisfactorily. Some of these materials have shown biocompatibility and ability to enhance cell adhesion, proliferation and cellular differentiation and uptake. Besides, some natural inorganic ingredients effectively retain drugs, allowing the design of drug delivery matrices.

Objective:

possibilities of natural inorganic ingredients in wound healing treatments have been reviewed, the following sections have been included: 1. Introduction 2. Functions of Inorganic Ingredients in wound healing 2.1. Antimicrobial effects 2.2. Hemostatic effects 3. Clay minerals for wound healing 3.1. Clay minerals 3.2. Clay mineral semisolid formulations 3.3. Clay/polymer composites and nanocomposites 3.4. Clay minerals in wound dressings 4. Other inorganic materials for wound healing 4.1. Zeolites 4.2. Silica and other silicates 4.3. Other minerals 4.4. Transition metals 5. Conclusion

Conclusion:

inorganic ingredients possess useful features in the development of chronic wounds advanced treatments. They improve physical (mechanical resistance and water vapor transmission), chemical (release of drugs, hemostasis and/or adsorption of exudates and moisture) and biological (antimicrobial effects and improvement of healing) properties of wound dressings. In summary, inorganic ingredients have proved to be a promising and easily accessible products in the treatment of wounds and, more importantly, chronic wounds.

Influence of the physicochemical characteristics of diatom frustules on hemorrhage control

Diatom frustules are good resources for hemostasis agent production.

Biomaterials and Advanced Technologies for Hemostatic Management of Bleeding

Bleeding complications arising from trauma, surgery, and as congenital, disease-associated, or drug-induced blood disorders can cause significant morbidities and mortalities in civilian and military populations. Therefore, stoppage of bleeding (hemostasis) is of paramount clinical significance in prophylactic, surgical, and emergency scenarios. For externally accessible injuries, a variety of natural and synthetic biomaterials have undergone robust research, leading to hemostatic technologies including glues, bandages, tamponades, tourniquets, dressings, and procoagulant powders. In contrast, treatment of internal noncompressible hemorrhage still heavily depends on transfusion of whole blood or blood's hemostatic components (platelets, fibrinogen, and coagulation factors). Transfusion of platelets poses significant challenges of limited availability, high cost, contamination risks, short shelf-life, low portability, performance variability, and immunological side effects, while use of fibrinogen or coagulation factors provides only partial mechanisms for hemostasis. With such considerations, significant interdisciplinary research endeavors have been focused on developing materials and technologies that can be manufactured conveniently, sterilized to minimize contamination and enhance shelf-life, and administered intravenously to mimic, leverage, and amplify physiological hemostatic mechanisms. Here, a comprehensive review regarding the various topical, intracavitary, and intravenous hemostatic technologies in terms of materials, mechanisms, and state-of-art is provided, and challenges and opportunities to help advancement of the field are discussed.

Chitosan-Coated Diatom Silica as Hemostatic Agent for Hemorrhage Control

Uncontrolled hemorrhage leads to high death risk both in military and civilian trauma. Current hemostatic agents still have various limitations and side effects. In this study, natural diatom silica obtained from diatomite and diatom culture was purified and developed for hemorrhage control. To improve the biocompatibility and hemostatic performance of diatom silica, a series of chitosan-coated diatom (CS-diatom) was developed. The composition of CS-diatom prepared was optimized by in vitro hemocompatibility and blood coagulation evaluation for that prepared with 0.5%, 1%, 3%, and 5% chitosan. The results demonstrated that the CS-diatom prepared with 1% chitosan exhibited favorable biocompatibility (hemolysis ratio < 5%, no cytotoxicity to MEFs), great fluid absorbility (24.39 ± 1.53 times the weight of liquid), and desirable hemostasis effect (351 ± 14.73 s at 5 mg/mL, 248 ± 32.42s at 10 mg/mL). Further blood coagulation mechanism study indicated that CS-diatom could provide an ideal interface to induce erythrocyte absorption and aggregation, along with activating the intrinsic coagulation pathway and thus accelerated blood coagulation. Benefitting from the multiple hemostatic performances, CS-diatom showed the shortest clotting time (98.34 ± 26.54 s) and lowest blood loss (0.31 ± 0.11 g) in rat-tail amputation model compare to diatomite and diatom as well as gauze and commercial QuikClot zeolite. The results evidenced that the CS-diatom was a safe and effective hemostatic agent and provided a new understanding of nonsynthetic mesoporous materials for hemorrhage control.

Gallium-containing mesoporous bioactive glass with potent hemostatic activity and antibacterial efficacy

Gallium-containing mesoporous bioactive glass can be considered as an efficient hemostatic material due to its merits of increased platelet adhesion and thrombin formation as well as antibacterial properties.

Comparison of the topical haemostatic efficacy of nano-micro particles of clinoptilolite and kaolin in a rat model of haemorrhagic injury

PURPOSE

This study was designed to investigate if the potential haemostatic efficacy of gauze-impregnated clinoptilolite created with nano-technology is as strong as the widely used kaolin to control pulsatile arterial bleeding due to major vascular injury.

METHODS

42 rats were separated into three groups of kaolin, clinoptilolite and control groups. The femoral artery was isolated and active arterial haemorrhage was performed. After 30 s of free arterial haemorrhage, compression was applied with a standard 100 g scale and haemostasis was assessed at the 1st, 3rd and 5th minutes. All groups were observed throughout 60 min for survival without any fluid resuscitation and the mean arterial pressure, pulse, body/surface temperature and arterial blood gas values were measured.

RESULTS

In the control group, haemostasis did not develop in any of the 12 rats and the survival rate was 5/12 (41.66 %). In the kaolin group, haemostasis developed in seven rats and of these, bleeding reoccurred in four. The survival rate was 10/13 (76.92 %). In the clinoptilolite group, haemostasis developed in eight rats and bleeding recurred in only one. The survival rate was 100 %. In terms of survival, the clinoptilolite and kaolin groups showed superiority to the control group (p = 0.002, p = 0.082). In the evaluation of recurrent haemorrhaging in the rats with haemostasis, clinoptilolite was observed to provide better coagulation than kaolin.

CONCLUSION

A statistically significant difference was determined in clinoptilolite and kaolin group, when they are separately compared with the control group in respect of the effect on MAP, HCO3 (-), lactate, base excess, haemostasis duration and survival rates. The effect of clinoptilolite on haemostasis and survival time was observed to be at least as good as that of kaolin; therefore, clinoptilolite can be used as an active ingredient in a topical haemostat.

Nano-ZnO impregnated inorganic–polymer hybrid thinfilm nanocomposite nanofiltration membranes: an investigation of variation in structure, morphology and transport properties

TFN-NF membranes prepared byin situinterfacial polymerization of branched polyethyleneimine and trimesoyl chloride, with simultaneous impregnation of as-synthesized hexagonal wurtzite nano-ZnO either through aqueous or organic phase.

Zeolite-based hemostat QuikClot releases calcium into blood and promotes blood coagulation in vitro

AIM

To examine the changes in electrolyte concentrations after addition of zeolite-based hemostat QuikClot in blood and the effects of zeolite on blood coagulation in vitro.

METHODS

Fresh blood was taken from healthy adult volunteers and sheep, and the electrolyte concentrations in blood were measured using a blood electrolyte analyzer. Zeolite Saline Solution (ZSS) was prepared by addition of 2 g zeolite to 0.9% NaCl solution (4, 8, or 16 mL). The electrolytes in ZSS were measured using inductively coupled plasma atomic emission spectroscopy. The prothrombin time (PT) and activated partial thromboplastin time (APTT) of blood were measured using the test tube method. The activated clotting time (ACT) and clotting rate (CR) of blood were measured with Sonoclot Coagulation and Platelet Function Analyzer.

RESULTS

Addition of zeolite (50 and 100 mg) in 2 mL human blood significantly increased Ca(2+) concentration, while Na(+) and K(+) concentrations were significantly decreased. Addition of zeolite (50 and 100 mg) in 0.9% NaCl solution (2 mL) caused similar changes in Ca(2+) and Na(+) concentrations. Si(4+) (0.2434 g/L) and Al(3+) (0.2575 g/L) were detected in ZSS (2 g/8 mL). Addition of ZSS in sheep blood shortened APTT in a concentration dependent manner, without changing PT. ZSS or aqueous solution of CaCl2 that contained Ca(2+) concentration identical to that of ZSS significantly shortened ACT in human blood without significantly changing CR, and the effect of ZSS on ACT was not significantly different from that of CaCl2.

CONCLUSION

Zeolite releases Ca(2+) into blood, thus accelerating the intrinsic pathway of blood coagulation and shortening the clot formation time.

Biocompatibility of mesoporous silica nanoparticles

In this review, recent reports on the biocompatibility of mesoporous silica nanoparticles (MSNs) are reviewed, with special emphasis being paid to the correlations between MSNs' structural and compositional features and their biological effects on various cells and tissues. First, the different synthetic routes used to produce the most common types of MSNs and the various methods employed to functionalize their surfaces are discussed. This is, however, done only briefly because of the focus of the review being the biocompatibility of the materials. Similarly, the biological applications of MSNs in areas such as drug and gene delivery, biocatalysis, bioimaging, and biosensing are briefly introduced. Many examples have also been mentioned about the biological applications of MSNs while discussing the materials' biocompatibility. The cytotoxicity of different types of MSNs and the effects of their various structural characteristics on their biological activities, which are the focus of this review, are then described in detail. In addition, synthetic strategies developed to reduce or eliminate any possible negative biological effects associated with MSNs or to improve their biocompatibility, as necessary, are illustrated. At the same time, recent reports on the interactions between MSNs and various in vivo or in vitro biological systems, plus our opinions and remarks on what the future may hold for this field, are included.

Antibacterial hemostatic dressings with nanoporous bioglass containing silver

Nanoporous bioglass containing silver (n-BGS) was fabricated using the sol-gel method, with cetyltrimethyl ammonium bromide as template. The results showed that n-BGS with nanoporous structure had a surface area of 467 m²/g and a pore size of around 6 nm, and exhibited a significantly higher water absorption rate compared with BGS without nanopores. The n-BGS containing small amounts of silver (Ag) had a slight effect on its surface area. The n-BGS containing 0.02 wt% Ag, without cytotoxicity, had a good antibacterial effect on Escherichia coli, and its antibacterial rate reached 99% in 12 hours. The n-BGS’s clotting ability significantly decreased prothrombin time (PT) and activated partial thromboplastin time (APTT), indicating n-BGS with a higher surface area could significantly promote blood clotting (by decreasing clotting time) compared with BGS without nanopores. Effective hemostasis was achieved in skin injury models, and bleeding time was reduced. It is suggested that n-BGS could be a good dressing, with antibacterial and hemostatic properties, which might shorten wound bleeding time and control hemorrhage.

Influence of zeolite crystal size on zeolite-polyamide thin film nanocomposite membranes

Zeolite-polyamide thin film nanocomposite membranes were coated onto polysulfone ultrafiltration membranes by interfacial polymerization of amine and acid chloride monomers in the presence of Linde type A zeolite nanocrystals. A matrix of three different interfacial polymerization chemistries and three different-sized zeolite crystals produced nanocomposite thin films with widely varying structure, morphology, charge, hydrophilicity, and separation performance (evaluated as reverse osmosis membranes). Pure polyamide film properties were tuned by changing polymerization chemistry, but addition of zeolite nanoparticles produced even greater changes in separation performance, surface chemistry, and film morphology. For fixed polymer chemistry, addition of zeolite nanoparticles formed more permeable, negatively charged, and thicker polyamide films. Smaller zeolites produced greater permeability enhancements, but larger zeolites produced more favorable surface properties; hence, nanoparticle size may be considered an additional "degree of freedom" in designing thin film nanocomposite reverse osmosis membranes. The data presented offer additional support for the hypothesis that zeolite crystals alter polyamide thin film structure when they are present during the interfacial polymerization reaction.

Blood clot initiation by mesocellular foams: dependence on nanopore size and enzyme immobilization

Porous silica materials are attractive for hemorrhage control because of their blood clot promoting surface chemistry, the wide variety of surface topologies and porous structures that can be created, and the potential ability to achieve high loading of therapeutic proteins within the silica support. We show that silica cell-window size variation in the nanometers to tens of nanometers range greatly affects the rate at which blood clots are formed in human plasma, indicating that window sizes in this size range directly impact the accessibility and diffusion of clotting-promoting proteins to and from the interior surfaces and pore volume of mesocellular foams (MCFs). These studies point toward a critical window size at which the clotting speed is minimized and serve as a model for the design of more effective wound-dressing materials. We demonstrate that the clotting times of plasma exposed to MCF materials are dramatically reduced by immobilizing thrombin in the pores of the MCF, validating the utility of enzyme-immobilized mesoporous silicas in biomedical applications.

Nanotechnology, nanotoxicology, and neuroscience

Nanotechnology, which deals with features as small as a 1 billionth of a meter, began to enter into mainstream physical sciences and engineering some 20 years ago. Recent applications of nanoscience include the use of nanoscale materials in electronics, catalysis, and biomedical research. Among these applications, strong interest has been shown to biological processes such as blood coagulation control and multimodal bioimaging, which has brought about a new and exciting research field called nanobiotechnology. Biotechnology, which itself also dates back approximately 30 years, involves the manipulation of macroscopic biological systems such as cells and mice in order to understand why and how molecular level mechanisms affect specific biological functions, e.g., the role of APP (amyloid precursor protein) in Alzheimer's disease (AD). This review aims (1) to introduce key concepts and materials from nanotechnology to a non-physical sciences community; (2) to introduce several state-of-the-art examples of current nanotechnology that were either constructed for use in biological systems or that can, in time, be utilized for biomedical research; (3) to provide recent excerpts in nanotoxicology and multifunctional nanoparticle systems (MFNPSs); and (4) to propose areas in neuroscience that may benefit from research at the interface of neurobiologically important systems and nanostructured materials.

Metal oxide surface charge mediated hemostasis

Blood coagulates faster upon contact with polar glasslike surfaces than on nonpolar plastic surfaces; this phenomenon is commonly termed the glass effect. However, the variable hemostatic response that we report here for contact-activated coagulation by different metal oxides, all of which are polar substrates, requires a refinement of this simple polarity model of how inorganic metal oxides activate the intrinsic pathway of blood coagulation. To our knowledge, the role of metal oxide surface charge as determined at the physiological pH and Ca2+ concentration of blood has not been previously investigated. We find that basic oxides with an isoelectric point above the pH of blood are anticoagulant while acidic oxides with an isoelectric point below the pH of blood are procoagulant. Using a thromboelastograph, we find that the onset time for coagulation and rate of coagulation post-initiation depend on both the sign and the magnitude of the initial surface charge density of the metal oxide. This work presents a useful strategy based on a quantifiable material parameter to select metal oxides to elicit a predictable and tunable biological response when they are in contact with blood.

Harnessing the sol-gel process for the assembly of non-silicate mesostructured oxide materials

Mesostructured non-silicate oxides, with well-defined organization on the 2-50 nm size scale, may play a pivotal role in advancing vital disciplines such as catalysis, energy conversion, and biotechnology. Herein, we present selected methodologies for utilizing the sol-gel process, in conjunction with organic-directed assembly, to synthesize a variety of mesostructured oxides. The nature of the inorganic precursor is critical for this process. We discuss the development of general routes for yielding stable, nanoscopic, hydrophilic, inorganic precursors compatible with organic co-assembly. In particular, we highlight the use and characterization of organic-acid-modified transition metal oxide sol-gel precursors that allow for the synthesis and processing of designer mesostructured oxides such as titania hybrids for optical applications and porous multicomponent metal oxides useful for catalysis.

Testing of Modified Zeolite Hemostatic Dressings in a Large Animal Model of Lethal Groin Injury

BACKGROUND

We have previously identified a granular zeolite hemostat (ZH) as an effective agent for control of severe bleeding, and it is currently being used by the US troops in the battlefield. ZH causes an exothermic reaction on application, which theoretically can be decreased by altering its chemical composition or changing its physical properties. However, the effect of these alterations on the hemostatic efficacy is unknown. We tested modified zeolites and a chitosan based dressing against controls in a swine model of battlefield injury.

METHODS

A complex groin injury was created in 60 swine (40-55 kg). This included semi-transection of the proximal thigh (level of inguinal ligament), and complete division of the femoral artery and vein. After 3 minutes, the animals were assigned to (1) no dressing (ND), (2) standard dressing (SD), (3-5) SD + chemically modified ZHs, where calcium was substituted with sodium (Na), barium (Ba), or silver (Ag), respectively, (6) SD + physically modified ZH, where "beads" were packaged in a fabric bag, (7) SD + chitosan based dressing (CD). Resuscitation was started 15 minutes after application of dressing (500 mL of 6% hetastarch over 30 minutes). Survival for 180 minutes was the primary endpoint for this study. In addition, blood loss, wound temperatures, and histologic tissue damage were recorded.

RESULTS

Mortality in the group that was treated with the application of bagged ZH was 10% versus 100% in the no dressing group and 50% in the SD group (p < 0.05 vs. ND and SD groups). The Na ZH group had a mortality rate of 43%, whereas application of Ba and Ag substituted zeolites, and CD were associated with a mortality rate of 25%. Ionic substitution of zeolite decreased the in vivo temperature peak by 5 to 10 degrees C. No histologic evidence of tissue necrosis was noted in this experiment.

CONCLUSIONS

The use of zeolite hemostat can control hemorrhage and dramatically reduce mortality from a lethal groin wound. Modifications of zeolite hemostat can decrease the exothermic reaction and attenuate tissue damage.