In situ synthesis of poly (γ- glutamic acid)/alginate/AgNP composite microspheres with antibacterial and hemostatic properties

Recent research advances in polysaccharide-based hemostatic materials: A review

Massive bleeding resulting from civil and martial accidents can often lead to shock or even death, highlighting the critical need for the development of rapid and efficient hemostatic materials. While various types of hemostatic materials are currently utilized in clinical practice, they often come with limitations such as poor biocompatibility, toxicity, and biodegradability. Polysaccharides, such as alginate (AG), chitosan (CS), cellulose, starch, hyaluronic acid (HA), and dextran, have exhibit excellent biocompatibility and in vivo biodegradability. Their degradation products are non-toxic to surrounding tissues and can be absorbed by the body. As a result, polysaccharides have been extensively utilized in the development of hemostatic materials and have gained significant attention in the field of in vivo hemostasis. This review offers an overview of the different forms, hemostatic mechanisms, and specific applications of polysaccharides. Additionally, it discusses the future opportunities and challenges associated with polysaccharide-based hemostats.

Preparation and Application of Hemostatic Hydrogels

Hemorrhage remains a critical challenge in various medical settings, necessitating the development of advanced hemostatic materials. Hemostatic hydrogels have emerged as promising solutions to address uncontrolled bleeding due to their unique properties, including biocompatibility, tunable physical characteristics, and exceptional hemostatic capabilities. In this review, a comprehensive overview of the preparation and biomedical applications of hemostatic hydrogels is provided. Particularly, hemostatic hydrogels with various materials and forms are introduced. Additionally, the applications of hemostatic hydrogels in trauma management, surgical procedures, wound care, etc. are summarized. Finally, the limitations and future prospects of hemostatic hydrogels are discussed and evaluated. This review aims to highlight the biomedical applications of hydrogels in hemorrhage management and offer insights into the development of clinically relevant hemostatic materials.

Fabrication of yeast β-glucan/sodium alginate/γ-polyglutamic acid composite particles for hemostasis and wound healing

Particles with a porous structure can lead to quick hemostasis and provide a good matrix for cell proliferation during wound healing. Recently, many particle-based wound healing materials have been clinically applied. However, these products show good hemostatic ability but with poor wound healing ability. To solve this problem, this study fabricated APGG composite particles using yeast β-glucan (obtained from Saccharomyces cerevisiae), sodium alginate, and γ-polyglutamic acid as the starting materials. The structure of yeast β-glucan was modified with many carboxymethyl groups to obtain carboxymethylated β-glucan, which could coordinate with Ca2+ ions to form a crosslinked structure. A morphology study indicated that the APGG particles showed an irregular spheroidal structure with a low density (<0.1 g cm-3) and high porosity (>40%). An in vitro study revealed that the particles exhibited a low BCI value, low hemolysis ratio, and good cytocompatibility against L929 cells. The APGG particles could quickly stop bleeding in a mouse liver injury model and exhibited better hemostatic ability than the commercially available product Celox. Furthermore, the APGG particles could accelerate the healing of non-infected wounds, and the expression levels of CD31, α-SMA, and VEGF related to angiogenesis were significantly enhanced.

Preparation and application of hemostatic microspheres containing biological macromolecules and others

Bleeding from uncontrollable wounds can be fatal, and the body's clotting mechanisms are unable to control bleeding in a timely and effective manner in emergencies such as battlefields and traffic accidents. For irregular and inaccessible wounds, hemostatic materials are needed to intervene to stop bleeding. Hemostatic microspheres are promising for hemostasis, as their unique structural features can promote coagulation. There is a wide choice of materials for the preparation of microspheres, and the modification of natural macromolecular materials such as chitosan to enhance the hemostatic properties and make up for the deficiencies of synthetic macromolecular materials makes the hemostatic microspheres multifunctional and expands the application fields of hemostatic microspheres. Here, we focus on the hemostatic mechanism of different materials and the preparation methods of microspheres, and introduce the modification methods, related properties and applications (in cancer therapy) for the structural characteristics of hemostatic microspheres. Finally, we discuss the future trends of hemostatic microspheres and research opportunities for developing the next generation of hemostatic microsphere materials.

Synthesis of Poly-γ-Glutamic Acid and Its Application in Biomedical Materials

Poly-γ-glutamic acid (γ-PGA) is a natural polymer composed of glutamic acid monomer and it has garnered substantial attention in both the fields of material science and biomedicine. Its remarkable cell compatibility, degradability, and other advantageous characteristics have made it a vital component in the medical field. In this comprehensive review, we delve into the production methods, primary application forms, and medical applications of γ-PGA, drawing from numerous prior studies. Among the four production methods for PGA, microbial fermentation currently stands as the most widely employed. This method has seen various optimization strategies, which we summarize here. From drug delivery systems to tissue engineering and wound healing, γ-PGA's versatility and unique properties have facilitated its successful integration into diverse medical applications, underlining its potential to enhance healthcare outcomes. The objective of this review is to establish a foundational knowledge base for further research in this field.

Hydrogels with Reversible Crosslinks for Improved Localised Stem Cell Retention: A Review

Successful stem cell applications could have a significant impact on the medical field, where many lives are at stake. However, the translation of stem cells to the clinic could be improved by overcoming challenges in stem cell transplantation and in vivo retention at the site of tissue damage. This review aims to showcase the most recent insights into developing hydrogels that can deliver, retain, and accommodate stem cells for tissue repair. Hydrogels can be used for tissue engineering, as their flexibility and water content makes them excellent substitutes for the native extracellular matrix. Moreover, the mechanical properties of hydrogels are highly tuneable, and recognition moieties to control cell behaviour and fate can quickly be introduced. This review covers the parameters necessary for the physicochemical design of adaptable hydrogels, the variety of (bio)materials that can be used in such hydrogels, their application in stem cell delivery and some recently developed chemistries for reversible crosslinking. Implementing physical and dynamic covalent chemistry has resulted in adaptable hydrogels that can mimic the dynamic nature of the extracellular matrix.

Tissue engineering modalities in skeletal muscles: focus on angiogenesis and immunomodulation properties

Muscular diseases and injuries are challenging issues in human medicine, resulting in physical disability. The advent of tissue engineering approaches has paved the way for the restoration and regeneration of injured muscle tissues along with available conventional therapies. Despite recent advances in the fabrication, synthesis, and application of hydrogels in terms of muscle tissue, there is a long way to find appropriate hydrogel types in patients with congenital and/or acquired musculoskeletal injuries. Regarding specific muscular tissue microenvironments, the applied hydrogels should provide a suitable platform for the activation of endogenous reparative mechanisms and concurrently deliver transplanting cells and therapeutics into the injured sites. Here, we aimed to highlight recent advances in muscle tissue engineering with a focus on recent strategies related to the regulation of vascularization and immune system response at the site of injury.

Injectable carboxymethyl chitosan-based hydrogel for simultaneous anti-tumor recurrence and anti-bacterial applications

The postoperative recurrence has adversely affected the treatment of tumors. Besides, the potential bacterial infection at the wound site may lead to a series of tissue necrosis. Here, we developed an injectable γ-polyglutamic acid/carboxymethyl chitosan/polydopamine hydrogel (PCP) for simultaneously reducing the postoperative infection and preventing the tumor recurrence. On the one hand, the aqueous solution of carboxymethyl chitosan oxidized the dopamine into polydopamine; on the other, the carboxymethyl chitosan was cross-linked with the activated γ-polyglutamic acid to form a hydrogel. After local implantation, the PCP hydrogel effectively killed tumor cells and bacteria under 808 nm laser irradiation. In addition, carboxymethyl chitosan rendered the hydrogel with anti-bacterial properties as well as anti-tumor efficiencies. The anti-tumor recurrence and anti-bacterial efficiencies of PCP hydrogel were proved on a tumor-removed mouse model and a Staphylococcus aureus-infected mouse model, respectively. Moreover, the hydrogel has the advantages of good biocompatibility and simple preparation, and thus has potential application prospects in the prevention of tumor recurrence and wound bacterial infection.

Electroactive injectable hydrogel based on oxidized sodium alginate and carboxymethyl chitosan for wound healing

Electroactive hydrogel is of great significance in restoring wound currents, promoting cell proliferation, and accelerating the wound healing process. However, the poor dispersity and underlying toxicity of electronic conductive fillers and high concentration of ionic conductors in traditional electroactive hydrogel limited its application in medical care. Herein, an electroactive oxidized sodium alginate/carboxymethyl chitosan/silver nanoparticles (OSA/CMCS/AgNPs) hydrogel was constructed with no additional conductive fillers or synthesized conductive polymers being added, in which the dynamic imine bonds were rapidly formed between aldehyde groups in OSA and amino groups in CMCS, and AgNPs were further in situ formed by UV irradiation. The electroactive hydrogel exhibited the injectable property, strong self-healing ability, excellent biocompatibility, and high antibacterial activities. Moreover, the electroactive hydrogel can significantly promote the proliferation of L929 cells under electrical stimulation. Furthermore, the electroactive hydrogel was proved to significantly accelerate the wound healing process in the full-thickness skin defect model, exhibiting anti-inflammation, promoting the fibroblasts proliferation, angiogenesis, and collagen deposition under electrical stimulation. In summary, the current work explored a novel strategy to construct the polysaccharides-based electroactive hydrogel with good biocompatibility and multi-functions, which is promising to be used in deep wound treatment.

High Molecular Weight Poly(glutamic acid) to Improve BMP2-Induced Osteogenic Differentiation

FDA-approved bone morphogenetic protein 2 (BMP2) has serious side effects due to the super high dose requirement. Heparin is one of the most well-studied sulfated polymers to stabilize BMP2 and improve its functionality. However, the clinical use of heparin is questionable because of its undesired anticoagulant activity. Recent studies suggest that poly(glutamic acid) (pGlu) has the potential to improve BMP2 bioactivity with less safety concerns; however, the knowledge on pGlu's contribution remains largely unknown. Therefore, we aimed to study the role of pGlu in BMP2-induced osteogenesis and its potential application in bone tissue engineering. Our data, for the first time, indicated that both low (L-pGlu) and high molecular weight pGlu (H-pGlu) were able to significantly improve the BMP2-induced early osteoblastic differentiation marker (ALP) in MC3T3-E1 preosteoblasts. Importantly, the matrix mineralization was more rapidly enhanced by H-pGlu compared to L-pGlu. Additionally, our data indicated that only α-H-pGlu could significantly improve BMP2's activity, whereas γ-H-pGlu failed to do so. Moreover, both gene expression and mineralization data demonstrated that α-H-pGlu enabled a single dose of BMP2 to induce a high level of osteoblastic differentiation without multiple doses of BMP2. To study the potential application of pGlu in tissue engineering, we incorporated the H-pGlu+BMP2 nanocomplexes into the collagen hydrogel with significantly elevated osteoblastic differentiation. Furthermore, H-pGlu-coated 3D porous gelatin and chitosan scaffolds significantly enhanced osteogenic differentiation through enabling sustained release of BMP2. Thus, our findings suggest that H-pGlu is a promising new alternative with great potential for bone tissue engineering applications.

Microfluidic generation of multifunctional core-shell microfibers promote wound healing

Wound healing is a complex physiological process involving four coordinated stages, including hemostasis, anti-inflammatory, repair, and epithelial formation. Herein, multifunctional core-shell alkylated chitosan/calcium alginate microfibers are fabricated as a novel strategy for promoting wound healing by contributing to each four stages in the entire healing process. Taking advantages of the microfluidic technology, the core-shell microfibers can be generated in a continuous and convenient manner through the interfacial assembly between alkylated chitosan and Na-alginate, as well as the simultaneous crosslink between calcium and the alginate. Generated microfibers possess unique internal structure which can effectively promote the absorption of blood and exudate produced during trauma. Moreover, the dodecyl carbon chain and abundant amino groups of alkylated chitosan provide microfibers with excellent hemostatic and antibacterial properties, which can repair acute hemorrhage and destroy bacteria rapidly. Further, the chronic wound healing process of a skin injury model can be significantly promoted by applying the fabricated microfibers. With these sequential functions to guide the whole-stage wound healing, the presented multifunctional core-shell microfibers create a versatile and robust paradigm for comprehensive wound treatment.

Strategies adopted for the preparation of sodium alginate–based nanocomposites and their role as catalytic, antibacterial, and antifungal agents

Alginate extracted from the marine brown algae is a massively utilized biopolymer in multiple fields such as microreactors for the fabrication of metal nanoparticles along with other polymeric and nonpolymeric materials to enhance their mechanical strength. These sodium alginate (Na-Alg)-based fabricated nanocomposites find applications in the field of catalysis and biological treatment as antibacterial/antifungal agent due to the synergistic properties of Na-Alg and fabricated metal nanoparticles (NPs). Na-Alg offers mechanical strength and nanoparticles provide high reactivity due to their small size. Sodium alginate exhibits hydroxyl and carboxylate functional groups that can easily interact with the metal nanoparticles to form composite particles. The research on the preparation of Na-Alg–based nanoparticles and nanoaggregates have been started recently but developed quickly due to their extensive applications in different fields. This review article encircles different methods of preparation of sodium alginate–based metal nanocomposites; analytical techniques reported to monitor the formation of these nanocomposites and used to characterize these nanocomposites as well as applications of these nanocomposites as catalyst, antibacterial, and antifungal agent.

Recent Advances in Poly(α-L-glutamic acid)-Based Nanomaterials for Drug Delivery

Poly(α-L-glutamic acid) (PGA) is a class of synthetic polypeptides composed of the monomeric unit α-L-glutamic acid. Owing to their biocompatibility, biodegradability, and non-immunogenicity, PGA-based nanomaterials have been elaborately designed for drug delivery systems. Relevant studies including the latest research results on PGA-based nanomaterials for drug delivery have been discussed in this work. The following related topics are summarized as: (1) a brief description of the synthetic strategies of PGAs; (2) an elaborated presentation of the evolving applications of PGA in the areas of drug delivery, including the rational design, precise fabrication, and biological evaluation; (3) a profound discussion on the further development of PGA-based nanomaterials in drug delivery. In summary, the unique structures and superior properties enables PGA-based nanomaterials to represent as an enormous potential in biomaterials-related drug delivery areas.

High-Sensitivity and Environmentally Friendly Humidity Sensors Deposited with Recyclable Green Microspheres for Wireless Monitoring

The reliable, high-sensitive, wireless, and affordable requirements for humidity sensors are needed in high-precision measurement fields. Quartz crystal microbalance (QCM) based on the piezoelectric effect can accurately detect the mass changes at the nanogram level. However, water-capture materials deposited on the surface of QCM generally show disadvantages in either cost, sensitivity, or recyclability. Herein, novel QCM-based humidity sensors (NQHSs) are developed by uniformly depositing green microspheres (GMs) of natural polymers prepared by the chemical synthesis of the emulsification/inner gel method on QCM as humidity-sensitive materials. The NQHSs demonstrate high accuracy and sensitivity (27.1 Hz/% RH) owing to the various hydrophilic groups and porous nano-3D deposition structure. Compared with the devices deposited with a smooth film, the frequency of the NQHSs shows almost no changes during the cyclic test and exhibits long-term stability. The NQHSs have been successfully applied to non-contact sensing human activities and remote real-time humidity monitoring via Bluetooth transmission. In addition, the deposited humidity-sensitive GMs and QCM substrate are fully recycled and reused (72% of the original value). This work has provided an innovative idea to construct environmental-friendly, high-sensitivity, and wireless humidity sensors.

Microfluidic-based functional materials: new prospects for wound healing and beyond

Microfluidics has been applied to fabricate high-performance functional materials contributing to all physiological stages of wound healing. The advances of microfluidic-based functional materials for wound healing have been summarized.

Polymeric Materials for Hemostatic Wound Healing

Hemorrhage is one of the greatest threats to life on the battlefield, accounting for 50% of total deaths. Nearly 86% of combat deaths occur within the first 30 min after wounding. While external wound injuries can be treated mostly using visual inspection, abdominal or internal hemorrhages are more challenging to treat with regular hemostatic dressings because of deep wounds and points of injury that cannot be located properly. The need to treat trauma wounds from limbs, abdomen, liver, stomach, colon, spleen, arterial, venous, and/or parenchymal hemorrhage accompanied by severe bleeding requires an immediate solution that the first responders can apply to reduce rapid exsanguinations from external wounds, including in military operations. This necessitates the development of a unique, easy-to-use, FDA-approved hemostatic treatment that can deliver the agent in less than 30 s and stop bleeding within the first 1 to 2 min at the point of injury without application of manual pressure on the wounded area.

Preparation of physically crosslinked polyelectrolyte Gelatin-Tannic acid-κ-Carrageenan (GTC) microparticles as hemostatic agents

In humans, excessive bleeding during civilian accidents, and surgery account for 40% of the mortality worldwide. Hence, the development of biocompatible hemostatic materials useful for rapid hemorrhage control has become a fundamental research problem in the biomedicine community. In this study, we prepared biocompatible gelatin-tannic acid-κ-carrageenan (GTC) microparticles using a facile Tween 80 stabilized water-in-oil (W/O) emulsion method for rapid hemostasis. The formation of GTC microparticles occurs via polyelectrolyte interactions between gelatin and k-carrageenan as well as hydrogen bonding from tannic acid. In addition, the GTC microparticles formulated in our study showed high water adsorption ability with a low volume-swelling ratio for a particle size of 46 μm. In addition, the GTC microparticles displayed >80% biocompatibility in NIH 3T3 cells and <5% hemocompatibility in hemolysis ratio tests. Notably, the GTC microparticles induced rapid blood clotting in 50 s and blood loss of approximately 46 mg in the femoral artery of BALB/c female mice with a 100% survival rate that was significantly better than the control group (blood clot time:250 s; blood loss: 259 mg). Thus, the findings from our study collectively suggest that GTC microparticles may play a promising clinical role in medical applications to tackle hemorrhage control.

Analysis of Safety and Effectiveness of Sodium Alginate/Poly(γ-glutamic acid) Microspheres for Rapid Hemostasis

Most preventable deaths after trauma are related to hemorrhage and occur early after injury. Timely hemostatic treatment is essential to minimize blood loss and improve survival. Among the various treatment methods, the most economical and effective is to use a hemostatic agent. A powdered hemostatic agent can be used for wounds of any shape or depth with high compactness and excellent accumulation effect. Herein, we chose the natural, hydrophilic polymer poly(γ-glutamic acid) (γ-PGA) to form composite hemostatic microspheres with sodium alginate (SA), which show good biocompatibility, water absorptivity, and viscosity. The morphology and structure of the hemostatic microspheres were determined using Fourier transform infrared spectroscopy and scanning electron microscopy. The overall safety, hemolysis, pyrogenic, and intradermal irritation tests were examined. The relationship between hemostatic pressure and hemostatic time during microsphere use was also measured. The hemostatic effect was analyzed with a liver, spleen, and femoral artery bleeding model. The composite microspheres were well tolerated in vivo and exhibited better hemostatic effects in animal experiments than a microporous polysaccharide powder compound. Research results showed that SA/γ-PGA microspheres are materials with good hemostatic effect, high safety, and great potential in clinical applications.

In-situ synthesis of polypyrrole/silver for fabricating alginate fabrics with high conductivity, UV resistance and hydrophobicity

In this research, the polypyrrole/silver (PPy/Ag) composite was first in-situ prepared on alginate fabrics by chemical oxidative polymerization of pyrrole (Py) monomer using silver nitrate as oxidant and sodium dodecyl sulfate (SDS) as the dopant. The effects of mole ratio of Py to silver nitrate, reaction time and dopant concentration on the preparation of PPy/Ag composite were optimized. It was found the optimal molar ratio of Py to silver nitrate was 1:1.5 with 0.02 M SDS under the reaction time of 10 h. Then, the microstructure and properties of resultant PPy/Ag composite were analyzed by scanning electron microscope (SEM), Fourier infrared spectrometer (FT-IR), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and the thermogravimetry analysis (TGA), respectively. Finally, the influences of PPy/Ag coating on the performance of alginate fabrics including electrical conductivity, hydrophilicity, antistatic property and anti-ultraviolet capability were determined. It was found that the electrical conductivity of alginate fabric could be intensively increased after PPy/Ag coating. Meantime, the anti-ultraviolet capability and hydrophobicity could be largely improved by PPy/Ag coating especially under high Py dosage. This paper introduced a simple method for preparing PPy/Ag composite direct on alginate fabric to make it a good functional substrate which could be applied in many fields.

Adaptable hydrogel with reversible linkages for regenerative medicine: Dynamic mechanical microenvironment for cells

Hydrogels are three-dimensional platforms that serve as substitutes for native extracellular matrix. These materials are starting to play important roles in regenerative medicine because of their similarities to native matrix in water content and flexibility. It would be very advantagoues for researchers to be able to regulate cell behavior and fate with specific hydrogels that have tunable mechanical properties as biophysical cues. Recent developments in dynamic chemistry have yielded designs of adaptable hydrogels that mimic dynamic nature of extracellular matrix. The current review provides a comprehensive overview for adaptable hydrogel in regenerative medicine as follows. First, we outline strategies to design adaptable hydrogel network with reversible linkages according to previous findings in supramolecular chemistry and dynamic covalent chemistry. Next, we describe the mechanism of dynamic mechanical microenvironment influence cell behaviors and fate, including how stress relaxation influences on cell behavior and how mechanosignals regulate matrix remodeling. Finally, we highlight techniques such as bioprinting which utilize adaptable hydrogel in regenerative medicine. We conclude by discussing the limitations and challenges for adaptable hydrogel, and we present perspectives for future studies.

Sensitive colorimetric detection of ascorbic acid based on seed mediated growth of sodium alginate reduced/stabilized gold nanoparticles

A sensitive detection strategy for ascorbic acid (AA), using sodium alginate reduced/stabilized gold nanoparticles (SA-AuNPs) as the optical probe, is reported. The SA-AuNPs were prepared by mixing gold salt and SA under stirring for 2 h at room temperature, without any further steps. The mixture was aged at 4 °C overnight, after which a faint-purple colloidal solution of SA-AuNPs was obtained. Characterization shows that the synthesis is incapable of reducing all Au³⁺ to Au°, but rather to mixture of Au°/Au⁺. The addition of AA to the SA-AuNPs probe reduced completely all Au⁺ to new AuNPs which were deposited on the pre-formed SA-AuNPs seed, leading to size increment and absorption spectra enhancement. The assay exhibited a good linearity between 12.5 and 150.0 μM AA and low limit of quantification of 11.2 μM. It was further used for AA quantitation in vitamin C injection and fruit juice with satisfactory accuracy and precision.

Preparing, Characterization and Anti-Biofilm Activity of Polymer Fibers Doped by Green Synthesized AgNPs

The aim of the work was to prepare polymer matrix composite (PMC) microfibers doped by green synthesized silver nanoparticles (AgNPs). The incorporation of AgNP into the polymer matrix can provide toxic properties to the polymer. Polyvinyl alcohol (PVA) was used as a matrix. AgNPs were synthesized by the green method, where the leaf extract of Rosmarinus officinalis (R. officinalis) was used as a reduction and capping agent. PVA-AgNPs composites were prepared in two ways: the ex situ method (pre-prepared globular AgNPs with a mean diameter of 20 nm were added into polymer matrix) and the in situ method (AgNPs were synthesized in the process of polymer composite preparation; in situ synthesized nanoparticles were a mix of different shapes with a mean diameter of ~100 nm). FTIR (Infrared spectroscopy with Fourier Transformation), UV–vis (Ultraviolet–visible spectroscopy), TEM (Transmission Electron Microscope), EDX (Energy-dispersive X-ray spectroscopy), and SEM (Scanning Electron Microscope) techniques were used for the analysis of nanoparticles and prepared PMCs. Thin layers and microfibers of in situ and ex situ PMCs were prepared. The presence of AgNPs clusters was evident in both PMC thin layers. After electrospinning, the chains of nanoparticles were observed inside the fibers. The distribution of nanoparticles was improved by increasing the AgNPs volume fraction (from 5 vol.% to 20 vol.%). Toxic and antibiofilm activity of AgNPs colloid, pure PVA, and PVA-AgNPs composites against the one-cell green algae Parachlorella kessleri (P. kessleri) was analyzed. AgNPs colloid, as well as PVA-AgNPs composites, showed good toxic and antibiofilm activity, and pure PVA shows no toxic/antibiofilm activity.

Novel composite unit with one pyridinium and three N-halamine structures for enhanced synergism and superior biocidability on magnetic nanoparticles

A novel composite unit of enhanced synergism that rises from the use of a cationic pyridinium structure to attract anionic bacteria to three N-halamine structures was designed for superior biocidability on recyclable magnetic nanoparticles. Briefly, 5-(4-hydroxybenzylidene)hydantoin (HBH), containing one imide and amide NH bonds, was synthesized by Knoevenagel condensation ofp-hydroxybenzaldehyde with hydantoin. 3-Triethoxysilylpropyl succinic anhydride was ammonolyzed with 4-aminopyridine to introduce a pyridine structure and form an amide NH and a carboxylic acid group that was esterified with HBH to introduce its two NH bonds. The triethoxysilyl groups of the esterification product were hydrolyzed into silanols to condense with the counterparts of different hydrolysates and on silica modified Fe₃O₄nanoparticles to provide a layer of polymeric modifier. After quaternization of the pyridine and chlorination of NH bonds from each esterification product, the resultant layer is composed of units each of which contains one pyridinium and threeN-halamine sites and exerted higher biocidability against Escherichia coli and Staphylococcus aureus than comparable systems including synergistic ones with one cationic center and one N-halamine, demonstrating an enhanced synergism. The biocidal layer had promising stability under quenching-chlorinating cycles and long-term storage. The study affords a strategy for syntheses of more powerful biocidal surfaces.

In vitro evaluation of the hyaluronic acid/alginate composite powder for topical haemostasis and wound healing

The use of haemostatic agents can provide life-saving treatment for patients who suffer from massive bleeding in both prehospital and intraoperative conditions. However, there are still urgent demands for novel haemostatic materials that exhibit better haemostatic activity, biocompatibility, and biodegradability than existing products. In the present study, we aim to evaluate the feasibility of new wound dressing, RapidClot, for treating uncontrolled haemorrhage through a series of in vitro assessments to determine the swelling ratio, clotting time, enzymatic degradation, haemolytic activity, cytotoxicity, cell proliferation, and migration. The results indicated that the RapidClot revealed better water adsorption capacity and shorter blood clotting time (132.7 seconds) than two commercially available haemostatic agents Celox (378.7 seconds) and WoundSeal (705.3 seconds). Additionally, the RapidClot dressing exhibited a similar level of degradability in the presence of hyaluronidase and lysozyme as that of Celox, whereas negligible degradation of WoundSeal was obtained. Although both Celox and RapidClot revealed a similar level in cell viability (above than 90%) against NIH/3 T3 fibroblasts, improved cell proliferation and migration could be obtained in RapidClot. Taking together, our results demonstrated that RapidClot could possess a great potential for serving as an efficient healing dressing with haemorrhage control ability.

Engineering of antibacterial/recyclable difunctional nanoparticles via synergism of quaternary ammonia salt site and N-halamine sites on magnetic surface

A biocidal composite unit with improved synergism, using one cationic quaternary ammonia salt (QAS) site to attract electronegative bacteria to three highly biocidal N-halamine sites, was designed for the first time and attached onto surface of magnetic silica coated Fe₃O₄ nanoparticles (silica@Fe₃O₄NPs) for superior biocidability, large killing area, and easy recyclability. Briefly, a compound containing one imide and two amide NH bonds, 2-(2,5-dioxoimidazolidin-4-yl)-N-(4-hydroxyphenyl)acetamide (DHPA), was prepared by amidation of hydantoin acetic acid with p-aminophenol. A biocidal precursor of one QAS site and three N-halamine sites was then constructed by alcoholysis of 3-triethoxysilylpropyl succinic anhydride with 2-(dimethylamino)ethan-1-ol to introduce a tertiary amine and subsequent esterification with DHPA to introduce three NH bonds. The triethoxysilyl groups in the precursor were hydrolyzed to silanol groups to condense with their counterparts on silica@Fe₃O₄ NPs. The surface of resultant NPs carried units each contains one QAS site and three N-halamine sites after quaternization and chlorination. The biocidal surface showed superior biocidability against Escherichia coli and Staphylococcus aureus than reported systems due to the improved synergism between multiple antibacterial groups of different types and was stable towards quenching-chlorinating process and storage. The successful design opens insight in the syntheses of more powerful biocides.