Alginate aerogels carrying calcium, zinc and silver cations for wound care: Fabrication and metal detection

Investigation of the Antibacterial Activity of ZnO-Loaded Alginate/Hyaluronic Acid Aerogels for Wound Dressing Applications

The prevalence of bacterial infections in wounds is a significant challenge to successful wound healing. This study investigates the antibacterial effect of hyaluronic acid and alginate aerogel loaded with zinc oxide nanoparticles as a potential dressing for wound healing. The aerogel composite was synthesized via supercritical gel drying and characterized by scanning electron microscope, Fourier transform infrared spectroscopy, and nitrogen porosimetry. The absorptivity of the prepared aerogel was evaluated, as well as the antibacterial activity, which was evaluated against common wound pathogens, including Staphylococcus aureus and Escherichia coli, using the agar diffusion method. The results show the effective antibacterial properties of the prepared hydrogel and aerogel. Furthermore, the results show water absorption ability of 5791 and 1585% for loaded and unloaded aerogels, respectively. The ZnO released from the aerogel exhibited a rapid release followed by a slow and sustained release. These findings highlight the potential of aerogels based on hyaluronic acid and alginate and loaded with zinc oxide nanoparticles as an innovative antibacterial wound dressing material, which is expected to improve wound healing and reduce the risk of bacterial infections.

Recent advances of bioaerogels in medicine: Preparation, property and application

Bioaerogels represent a type of three-dimensional porous materials fabricated from natural biopolymers, and show a significant potential for medical application due to their characteristics of extremely low density, high specific surface area, excellent biocompatibility and biodegradability. The preparation method and parameters of bioaerogels are focused on, and their influence on the structure and properties of bioaerogels are discussed in detail. Then, to match the properties of bioaerogels with the medical applications, this work emphasizes the main properties (including biocompatibility, degradability, and mechanical properties), structural parameters (such as suitable porosity, pore size and high specific surface area), and further summarizes the influence of single-component and composite bioaerogels on their properties. Moreover, according to the different applications (wound healing, drug delivery, and tissue engineering and other fields), the function method, mechanism and practical effect of bioaerogels are comprehensively analyzed. Finally, the challenges, future research directions, and solutions for the practical application of bioaerogels in medicine are discussed.

The evolution of calcium alginate-based dressings in wound healing: A comprehensive bibliometric review of the top 100 cited studies

Calcium alginate, a naturally derived polysaccharide from brown seaweed, has gained significant prominence in advanced wound care technologies. Despite its widespread application, there is a need for a bibliometric analysis to map the scientific advancements and thematic evolution in the field. To conduct a bibliometric analysis of the top 100 most cited papers on calcium alginate wound dressings to identify key contributors, collaborative networks, prominent themes, and trends in citation impact. The Scopus database was utilized for its broad multidisciplinary coverage. A search string "(wound dressing) AND (calcium alginate)" was applied to the Title, Abstract, and Keywords fields without time restrictions. Only articles and reviews were included. The analysis involved two phases: (1) a general examination of all retrieved publications for productive authors, institutions, countries, sponsors, and sources; and (2) an in-depth analysis of the top 100 most cited papers using VOSviewer and the bibliometrix package in R Studio. Co-authorship, citation networks, keyword co-occurrences, and citation metrics were visualized and statistically analyzed. From a total of 330 publications identified, the United States (57 publications), the United Kingdom (54), and China (46) emerged as leading contributors. Key institutions included Donghua University (9 publications) and Chulalongkorn University (5 publications). Prominent funding sources were the National Natural Science Foundation of China (20 publications) and the Ministry of Science and Technology of China (6 publications). The International Journal of Biological Macromolecules, the International Wound Journal, and the British Journal of Plastic Surgery were frequently cited sources. The top 100 cited papers, spanning 1983-2023, demonstrated peaks in citation impact in 2014 and 2015, with mean citations per article exceeding 270. Co-word analysis revealed evolving research themes over decades, highlighting foundational and innovative contributions. This comprehensive analysis may provide valuable insights into the thematic evolution and emerging trends, serving as a foundation for future research in wound care technologies.

Enhanced antibacterial activity of starch-alginate beads by a synergistic effect between Cu2+ and Zn2+ ions with a potential wound dressing application

The synthesis and characterization of starch/alginate composite beads, crosslinked with Cu2+, Zn2+, and Cu:Zn mixtures were investigated, focusing on their potential application in exudative wound dressings. Hydrogel beads were prepared using the external gelation method and then dried via freeze-drying to create cryogels and air-drying to create xerogels. Microstructural characterization was performed using SEM and EDS, showing the typical porous structure with a homogeneous distribution of cations across the beads. Unimetallic beads exhibited higher equilibrium water uptake compared to Cu:Zn bimetallic beads (500 % vs. 300 %). After the swelling study, the total amount of Cu2+ released was significantly below the maximum allowed level as a safeguard against copper toxicity. All beads demonstrated excellent antimicrobial activity against E. coli, S. aureus, and P. aeruginosa. Bimetallic materials, particularly cryogels with equal or greater amount of zinc relative to copper, were particularly effective against P. aeruginosa. Hence, the synthesized bimetallic starch-alginate materials presented superior water absorption capacity and significantly enhanced antibacterial response compared to unimetallic beads, due to the synergistic effect between Cu2+ and Zn2+ ions, making then suitable for use in exudative wound dressings.

Structural and optical properties of alginate-based antibacterial dressing with calcium phosphate and zinc oxide for biodegradable wound painting applications

The skin is the outermost part of the body. Although susceptible to damage, the skin is in direct contact with the external environment. Wound dressing is a clinical method that plays a vital role in wound healing. Herein, we developed an antibacterial wound dressing using alginate as the basic material. The dressing was prepared using the solvent casting method, which was used to analyze the effects of adding CaP and ZnO on its structural, optical, and antibacterial properties. Adding CaP exhibited strong but stiff mechanical properties, unlike the CaP/ZnO, which possessed high strength and elasticity. The optical properties of sample S2 did not have a considerable impact. By contrast, the addition of ZnO to sample S3 notably increases the wavelength and absorption value. The diameter of the inhibition zone for S. aureus bacteria exhibited a successive increase in its antibacterial properties, and sample S3 exhibited the highest value. Thus, sample S3 is the most promising wound dressing concerning speeding up the wound healing process because it possesses the most optimal mechanical, optical, and antibacterial properties. The main limitation to be addressed is that sample S3 cannot be easily digested in the environment.

Dried Porous Biomaterials from Mealworm Protein Gels: Proof of Concept and Impact of Drying Method on Structural Properties and Zinc Retention

Dried porous materials can be found in a wide range of applications. So far, they are mostly prepared from inorganic or indigestible raw materials. The aim of the presented study was to provide a proof of concept for (a) the suitability of mealworm protein gels to be turned into dried porous biomaterials by either a combination of solvent exchange and supercritical drying to obtain aerogels or by lyophilization to obtain lyophilized hydrogels and (b) the suitability of either drying method to retain trace elements such as zinc in the gels throughout the drying process. Hydrogels were prepared from mealworm protein, subsequently dried using either method, and characterized via FT-IR, BET volume, and high-resolution scanning electron microscopy. Retention of zinc was evaluated via energy-dispersive X-ray spectroscopy. Results showed that both drying methods were suitable for obtaining dried porous biomaterials and that the drying method mainly influenced the overall surface area and pore hydrophobicity but not the secondary structure of the proteins in the gels or their zinc content after drying. Therefore, a first proof of concept for utilizing mealworm protein hydrogels as a base for dried porous biomaterials was successful and elucidated the potential of these materials as future sustainable alternatives to more conventional dried porous materials.

A greener approach for synthesizing metal-decorated carbogels from alginate for emerging technologies

In the present work, a series of metal nanoparticle-decorated carbogels (M-DCs) was synthesized starting from beads of parent metal-crosslinked alginate aerogels (M-CAs). M-CAs contained Ca(ii), Ni(ii), Cu(ii), Pd(ii) and Pt(iv) ions and were converted to M-DCs by pyrolysis under a N2 atmosphere up to pyrolysis temperatures of TP = 600 °C. The textural properties of M-CAs are found to depend on the crosslinking ion, yielding fibrous pore networks with a high specific mesoporous volume and specific surface area SV (SV ∼ 480-687 m2 g-1) for M-CAs crosslinked with hard cations, Ca(ii), Ni(ii) and Cu(ii), and comparably loose networks with increased macroporosity and lower specific surface (SV ∼ 240-270 m2 g-1) for Pd(ii) and Pt(iv) crosslinked aerogels. The pyrolysis of M-CAs resulted in two simultaneously occurring processes: changes in the solid backbone and the growth of metal/metal oxide nanoparticles (NPs). The thermogravimetric analysis (TGA) showed a significant influence of the crosslinking cation on the decomposition mechanism and associated change in textural properties. Scanning electron microscopy-backscattered electron imaging (SEM-BSE) and X-ray diffraction revealed that metal ions (molecularly dispersed in the parent aerogels) formed nanoparticles composed of elementary metals and metal oxides in varying ratios over the course of pyrolytic treatment. Increasing the TP led to generally larger nanoparticles. The pyrolysis of the nickel-crosslinked aerogel (Ni-CA) preserved, to a large extent, the mesoporous structure and resulted in the evolution of fine (∼14 nm) homogeneously dispersed Ni/NiO nanoparticles. Overall, this work presents a green approach for synthesizing metal-nanoparticle containing carbon materials, useful in emerging technologies related to heterogeneous catalysis and electrocatalysis, among others.

The effect of synthesis conditions and process parameters on aerogel properties

Aerogels are remarkable nanoporous materials with unique properties such as low density, high porosity, high specific surface area, and interconnected pore networks. In addition, their ability to be synthesized from various precursors such as inorganics, organics, or hybrid, and the tunability of their properties make them very attractive for many applications such as adsorption, thermal insulation, catalysts, tissue engineering, and drug delivery. The physical and chemical properties and pore structure of aerogels are crucial in determining their application areas. Moreover, it is possible to tailor the aerogel properties to meet the specific requirements of each application. This review presents a comprehensive review of synthesis conditions and process parameters in tailoring aerogel properties. The effective parameters from the dissolution of the precursor step to the supercritical drying step, including the carbonization process for carbon aerogels, are investigated from the studies reported in the literature.

Aerogel-Based Biomaterials for Biomedical Applications: From Fabrication Methods to Disease-Targeting Applications

Aerogel-based biomaterials are increasingly being considered for biomedical applications due to their unique properties such as high porosity, hierarchical porous network, and large specific pore surface area. Depending on the pore size of the aerogel, biological effects such as cell adhesion, fluid absorption, oxygen permeability, and metabolite exchange can be altered. Based on the diverse potential of aerogels in biomedical applications, this paper provides a comprehensive review of fabrication processes including sol-gel, aging, drying, and self-assembly along with the materials that can be used to form aerogels. In addition to the technology utilizing aerogel itself, it also provides insight into the applicability of aerogel based on additive manufacturing technology. To this end, how microfluidic-based technologies and 3D printing can be combined with aerogel-based materials for biomedical applications is discussed. Furthermore, previously reported examples of aerogels for regenerative medicine and biomedical applications are thoroughly reviewed. A wide range of applications with aerogels including wound healing, drug delivery, tissue engineering, and diagnostics are demonstrated. Finally, the prospects for aerogel-based biomedical applications are presented. The understanding of the fabrication, modification, and applicability of aerogels through this study is expected to shed light on the biomedical utilization of aerogels.

Effects of combined cannabidiol (CBD) and hops (Humulus lupulus) terpene extract treatment on RAW 264.7 macrophage viability and inflammatory markers

This study investigates the potential of cannabidiol (CBD), one major cannabinoid of the plant Cannabis sativa, alone and in combination with a terpene-enriched extract from Humulus lupulus ("Hops 1"), on the LPS-response of RAW 264.7 macrophages as an established in vitro model of inflammation. With the present study, we could support earlier findings of the anti-inflammatory potential of CBD, which showed a dose-dependent [0-5 µM] reduction in nitric oxide and tumor necrosis factor-alpha (TNF-α) released by LPS-stimulated RAW 264.7 macrophages. Moreover, we observed an additive anti-inflammatory effect after combined CBD [5 µM] and hops extract [40 µg/mL] treatment. The combination of CBD and Hops 1 showed effects in LPS-stimulated RAW 264.7 cells superior to the single substance treatments and akin to the control hydrocortisone. Furthermore, cellular CBD uptake increased dose-dependently in the presence of terpenes from Hops 1 extract. The anti-inflammatory effect of CBD and its cellular uptake positively correlated with terpene concentration, as indicated by comparison with a hemp extract containing both CBD and terpenes. These findings may contribute to the postulations for the so-called "entourage effect" between cannabinoids and terpenes and support the potential of CBD combined with phytomolecules from a non-cannabinoid source, such as hops, for the treatment of inflammatory diseases.

In vivo tests of a novel wound dressing based on agar aerogel

Aerogels, especially bio-based ones, present a promising option for wound dressing; specifically, because of their low toxicity, high stability, bio-compatibility, and good biological performance. In this study, agar aerogel was prepared and evaluated as novel wound dressing material in an in vivo rat study. Agar hydrogel was prepared by thermal gelation, after that the water inside the gel was exchanged with ethanol, and finally the alcogel was dried by supercritical CO₂. The textural and rheological properties of the prepared aerogel were characterized, showing that the prepared agar aerogels possess high porosity (97-98 %), high surface area (250-330 m²g^-1) as well as good mechanical properties and easiness of removal from the wound site. The results of the in vivo experiments macroscopically demonstrate the tissue compatibility of the aerogels in dorsal interscapular injured rat tissue and a shorter wound healing time comparable to that of gauze-treated animals. The histological analysis underpins the reorganisation and healing of the tissue for the injured skin of rats treated with agar aerogel wound dressing within the studied time frame.

Preparation of Vancomycin-Loaded Aerogels Implementing Inkjet Printing and Superhydrophobic Surfaces

Chronic wounds are physical traumas that significantly impair the quality of life of over 40 million patients worldwide. Aerogels are nanostructured dry porous materials that can act as carriers for the local delivery of bioactive compounds at the wound site. However, aerogels are usually obtained with low drug loading yields and poor particle size reproducibility and urges the implementation of novel and high-performance processing strategies. In this work, alginate aerogel particles loaded with vancomycin, an antibiotic used for the treatment of Staphylococcus aureus infections, were obtained through aerogel technology combined with gel inkjet printing and water-repellent surfaces. Alginate aerogel particles showed high porosity, large surface area, a well-defined spherical shape and a reproducible size (609 ± 37 μm). Aerogel formulation with vancomycin loadings of up to 33.01 ± 0.47 μg drug/mg of particle were obtained with sustained-release profiles from alginate aerogels for more than 7 days (PBS pH 7.4 medium). Overall, this novel green aerogel processing strategy allowed us to obtain nanostructured drug delivery systems with improved drug loading yields that can enhance the current antibacterial treatments for chronic wounds.

Recent Advances in Antimicrobial Nano-Drug Delivery Systems

Infectious diseases are among the major health issues of the 21st century. The substantial use of antibiotics over the years has contributed to the dissemination of multidrug resistant bacteria. According to a recent report by the World Health Organization, antibacterial (ATB) drug resistance has been one of the biggest challenges, as well as the development of effective long-term ATBs. Since pathogens quickly adapt and evolve through several strategies, regular ATBs usually may result in temporary or noneffective treatments. Therefore, the demand for new therapies methods, such as nano-drug delivery systems (NDDS), has aroused huge interest due to its potentialities to improve the drug bioavailability and targeting efficiency, including liposomes, nanoemulsions, solid lipid nanoparticles, polymeric nanoparticles, metal nanoparticles, and others. Given the relevance of this subject, this review aims to summarize the progress of recent research in antibacterial therapeutic drugs supported by nanobiotechnological tools.

Low-dose Indonesian Aloe vera Increases Viability and Migration of the Fibroblast: An In Vitro Study

BACKGROUND: Important stages in wound healing involve homeostasis, inflammation, proliferation, and remodeling phases. Fibroblasts are essential factors in the healing pathway through the process of cell proliferation and migration. Aloe vera contains various active compounds used for anti-inflammatory, antimicrobial, immunomodulatory, anticancer, and wound healing. AIM: This study aimed to evaluate the effect of A. vera on the viability and migration of fibroblast cells. MATERIALS AND METHODS: Fibroblasts were cultured in a monolayer with Dulbecco’s Modified Eagle Medium containing 10% fetal bovine serum, 1% pinstripe, and 0.5% fungizone. We use fresh A. vera leaves extracted with 95% ethanol. Cell viability will be evaluated using the MTT test and microscopic evaluation. Cell migration was tested using an in vitro wound scratch assay and analyzed with ImageJ software. RESULTS: A. vera stimulated cell viability compared to control (p < 0.05). Administration of A. vera does not change shape and is not toxic to fibroblasts. A. vera stimulated cell migration at doses of 250, 125, 50, and 5 μg/mL compared to control after 24 h of intervention. At 48 h incubation, migration doses of 250, 50, and 5 μg/mL were higher than control (p < 0.05). CONCLUSIONS: A. vera extract may effectively wound healing by increasing viability and migration of fibroblast cells.

Safety and efficacy assessment of aerogels for biomedical applications

The unique physicochemical properties of aerogels have made them an attractive class of materials for biomedical applications such as drug delivery, regenerative medicine, and wound healing. Their low density, high porosity, and ability to regulate the pore structure makes aerogels ideal nano/micro-structures for loading of drugs and active biomolecules. As a result of this, the number of in vitro and in vivo studies on the therapeutic efficacy of these porous materials has increased substantially in recent years and continues to be an area of great interest. However, data about their in vivo performance and safety is limited. Studies have shown that polymer-based, silica-based and some hybrid aerogels are generally regarded as safe but given that studies on the acute, subacute, and chronic toxicity for the majority of aerogel types is missing, more work is still needed. This review presents a comprehensive summary of different biomedical applications of aerogels proposed to date as well as new and innovative applications of aerogels in other areas such as decontamination. We have also reviewed their biological effect on cells and living organisms with a focus on therapeutic efficacy and overall safety (in vivo and in vitro).

Bioaerogels: Promising Nanostructured Materials in Fluid Management, Healing and Regeneration of Wounds

Wounds affect one's quality of life and should be managed on a patient-specific approach, based on the particular healing phase and wound condition. During wound healing, exudate is produced as a natural response towards healing. However, excessive production can be detrimental, representing a challenge for wound management. The design and development of new healing devices and therapeutics with improved performance is a constant demand from the healthcare services. Aerogels can combine high porosity and low density with the adequate fluid interaction and drug loading capacity, to establish hemostasis and promote the healing and regeneration of exudative and chronic wounds. Bio-based aerogels, i.e., those produced from natural polymers, are particularly attractive since they encompass their intrinsic chemical properties and the physical features of their nanostructure. In this work, the emerging research on aerogels for wound treatment is reviewed for the first time. The current scenario and the opportunities provided by aerogels in the form of films, membranes and particles are identified to face current unmet demands in fluid managing and wound healing and regeneration.

Classification and Production of Polymeric Foams among the Systems for Wound Treatment

This work represents an overview on types of wounds according to their definition, classification and dressing treatments. Natural and synthetic polymeric wound dressings types have been analyzed, providing a historical overview, from ancient to modern times. Currently, there is a wide choice of materials for the treatment of wounds, such as hydrocolloids, polyurethane and alginate patches, wafers, hydrogels and semi-permeable film dressings. These systems are often loaded with drugs such as antibiotics for the simultaneous delivery of drugs to prevent or cure infections caused by the exposition of blood vessel to open air. Among the presented techniques, a focus on foams has been provided, describing the most diffused branded products and their chemical, physical, biological and mechanical properties. Conventional and high-pressure methods for the production of foams for wound dressing are also analyzed in this work, with a proposed comparison in terms of process steps, efficiency and removal of solvent residue. Case studies, in vivo tests and models have been reported to identify the real applications of the produced foams.

Hydrogel-Forming Algae Polysaccharides: From Seaweed to Biomedical Applications

With the increasing growth of the algae industry and the development of algae biorefinery, there is a growing need for high-value applications of algae-extracted biopolymers. The utilization of such biopolymers in the biomedical field can be considered as one of the most attractive applications but is challenging to implement. Historically, polysaccharides extracted from seaweed have been used for a long time in biomedical research, for example, agarose gels for electrophoresis and bacterial culture. To overcome the current challenges in polysaccharides and help further the development of high-added-value applications, an overview of the entire polysaccharide journey from seaweed to biomedical applications is needed. This encompasses algae culture, extraction, chemistry, characterization, processing, and an understanding of the interactions of soft matter with living organisms. In this review, we present algae polysaccharides that intrinsically form hydrogels: alginate, carrageenan, ulvan, starch, agarose, porphyran, and (nano)cellulose and classify these by their gelation mechanisms. The focus of this review further lays on the culture and extraction strategies to obtain pure polysaccharides, their structure-properties relationships, the current advances in chemical backbone modifications, and how these modifications can be used to tune the polysaccharide properties. The available techniques to characterize each organization scale of a polysaccharide hydrogel are presented, and the impact on their interactions with biological systems is discussed. Finally, a perspective of the anticipated development of the whole field and how the further utilization of hydrogel-forming polysaccharides extracted from algae can revolutionize the current algae industry are suggested.

Mechanism of Hydration and Hydration Induced Structural Changes of Calcium Alginate Aerogel

The most relevant properties of polysaccharide aerogels in practical applications are determined by their microstructures. Hydration has a dominant role in altering the microstructures of these hydrophilic porous materials. To understand the hydration induced structural changes of monolithic Ca-alginate aerogel, produced by drying fully cross-linked gels with supercritical CO₂, the aerogel was gradually hydrated and characterized at different states of hydration by small-angle neutron scattering (SANS), liquid-state nuclear magnetic resonance (NMR) spectroscopy, and magic angle spinning (MAS) NMR spectroscopy. First, the incorporation of structural water and the formation of an extensive hydration sphere mobilize the Ca-alginate macromolecules and induce the rearrangement of the dry-state tertiary and quaternary structures. The primary fibrils of the original aerogel backbone form hydrated fibers and fascicles, resulting in the significant increase of pore size, the smoothing of the nanostructured surface, and the increase of the fractal dimension of the matrix. Because of the formation of these new superstructures in the hydrated backbone, the stiffness and the compressive strength of the aerogel significantly increase compared to its dry-state properties. Further elevation of the water content of the aerogel results in a critical hydration state. The Ca-alginate fibers of the backbone disintegrate into well-hydrated chains, which eventually form a quasi-homogeneous hydrogel-like network. Consequently, the porous structure collapses and the well-defined solid backbone ceases to exist. Even in this hydrogel-like state, the macroscopic integrity of the Ca-alginate monolith is intact. The postulated mechanism accounts for the modification of the macroscopic properties of Ca-alginate aerogel in relation to both humid and aqueous environments.

Investigation of Aerogel Production Processes: Solvent Exchange under High Pressure Combined with Supercritical Drying in One Apparatus

This work aims to contribute to the theoretical and experimental research of supercritical processes for intensification and combination in one apparatus. Investigation is carried out to improve production technology of organic alginate aerogels. It is proposed within the investigation to carry out the solvent exchange stage, an important stage of organic aerogels production, under pressure in a carbon dioxide medium in the same apparatus used for supercritical drying. The phase behavior in the system "carbon dioxide-water-2-propanol", which arises during such a solvent exchange stage, is studied theoretically. An experimental study of the process of step-by-step solvent exchange under pressure was carried out through multiphase and homogeneous regions of the phase diagram of such a system. As a result, new highly efficient technology for the production of organic aerogels was proposed, which can be implemented by combining the two main stages of the process.

Biorefinery Approach for Aerogels

According to the International Energy Agency, biorefinery is "the sustainable processing of biomass into a spectrum of marketable bio-based products (chemicals, materials) and bioenergy (fuels, power, heat)". In this review, we survey how the biorefinery approach can be applied to highly porous and nanostructured materials, namely aerogels. Historically, aerogels were first developed using inorganic matter. Subsequently, synthetic polymers were also employed. At the beginning of the 21st century, new aerogels were created based on biomass. Which sources of biomass can be used to make aerogels and how? This review answers these questions, paying special attention to bio-aerogels' environmental and biomedical applications. The article is a result of fruitful exchanges in the frame of the European project COST Action "CA 18125 AERoGELS: Advanced Engineering and Research of aeroGels for Environment and Life Sciences".

Ca-Zn-Ag Alginate Aerogels for Wound Healing Applications: Swelling Behavior in Simulated Human Body Fluids and Effect on Macrophages

Chronic non-healing wounds represent a substantial economic burden to healthcare systems and cause a considerable reduction in quality of life for those affected. Approximately 0.5-2% of the population in developed countries are projected to experience a chronic wound in their lifetime, necessitating further developments in the area of wound care materials. The use of aerogels for wound healing applications has increased due to their high exudate absorbency and ability to incorporate therapeutic substances, amongst them trace metals, to promote wound-healing. This study evaluates the swelling behavior of Ca-Zn-Ag-loaded alginate aerogels and their metal release upon incubation in human sweat or wound fluid substitutes. All aerogels show excellent liquid uptake from any of the formulas and high liquid holding capacities. Calcium is only marginally released into the swelling solvents, thus remaining as alginate bridging component aiding the absorption and fast transfer of liquids into the aerogel network. The zinc transfer quota is similar to those observed for common wound dressings in human and animal injury models. With respect to the immune regulatory function of zinc, cell culture studies show a high availability and anti-inflammatory activity of aerogel released Zn-species in RAW 264.7 macrophages. For silver, the balance between antibacterial effectiveness versus cytotoxicity remains a significant challenge for which the alginate aerogels need to be improved in the future. An increased knowledge of the transformations that alginate aerogels undergo in the course of the fabrication as well as during wound fluid exposure is necessary when aiming to create advanced, tissue-compatible aerogel products.

Long-term antibacterial composite via alginate aerogel sustained release of antibiotics and Cu used for bone tissue bacteria infection

Bone related-bacterial diseases including wound infections and osteomyelitis (OM) remain a serious problem accompanied with amputation in most severe cases. In this work, we report an exceptional effective antibacterial alginate aerogel, which consists of tigecycline (TGC) and octahedral Cu crystal as an organo-inorganic synergy platform for antibacterial and local infection therapy applications. The alginate aerogel could greatly prolong the release of copper ions and maintain effective antibacterial concentration over 18 days. The result of in-vitro experiments demonstrated that the alginate aerogel has an exceptional effective function on antibacterial activity. Cytotoxicity tests indicated that the alginate aerogel has low biological toxicity (average cell viability >75%). These remarkable results suggested that the alginate aerogel exhibits great potential for the treatment of OM, and has a prosperous future of application in bone tissue engineering.

Bacterial Nanocellulose-Enhanced Alginate Double-Network Hydrogels Cross-Linked with Six Metal Cations for Antibacterial Wound Dressing

Alginate (Alg) and bacterial nanocellulose (BNC) have exhibited great potential in biomedical applications, especially wound dressing. Non-toxicity and a moisture-maintaining nature are common features making them favorable for functional dressing fabrication. BNC is a natural biopolymer that promotes major advances to the current and future biomedical materials, especially in a flat or tubular membrane form with excellent mechanical strength at hydrated state. The main drawback limiting wide applications of both BNC and Alg is the lack of antibacterial activity, furthermore, the inherent poor mechanical property of Alg leads to the requirement of a secondary dressing in clinical treatment. To fabricate composite dressings with antibacterial activity and better mechanical properties, sodium alginate was efficiently incorporated into the BNC matrix using a time-saving vacuum suction method followed by cross-linking through immersion in separate solutions of six cations (manganese, cobalt, copper, zinc, silver, and cerium). The results showed the fabricated composites had not only pH-responsive antibacterial activities but also improved mechanical properties, which are capable of acting as smart dressings. All composites showed non-toxicity toward fibroblast cells. Rat model evaluation showed the skin wounds covered by the dressings healed faster than by BNC.

Polymeric hybrid aerogels and their biomedical applications

Aerogels are a class of porous materials that possess extremely high specific surface area, high pore volume, high porosity, and variable chemical structures. They have been widely applied in the fields of aerospace, chemical engineering, construction, electrotechnics, and biomedicine. In recent years a great boom in aerogels has been observed, where various new aerogels with novel physicochemical properties and functions have been synthesized. Nevertheless, native aerogels with a single component normally face severe problems such as low mechanical strength and lack of functions. One strategy to solve the problems is to construct hybrid aerogels. In this study, a comprehensive review on polymer based hybrid aerogels is presented, including polymer-polymer, polymer-carbon material, and polymer-inorganic hybrid aerogels, which will be introduced and discussed in view of their chemical structures and hybrid structures. Most importantly, polymeric hybrid aerogels are classified into three different composition levels, which are molecular-level, molecular-aggregate-level, and aggregate-level, due to the fact that hybrid aerogels with the same chemical structures but with different composition levels might show quite different functions or properties. The biomedical applications of these hybrid aerogels will also be reviewed and discussed, where the polymeric components in the hybrid aerogels provide the main contribution. This review would provide creative design principles for aerogels by considering both their chemical and physical structures.

A Review on Revolutionary Natural Biopolymer-Based Aerogels for Antibacterial Delivery

A biopolymer-based aerogel has been developed to become one of the most potentially utilized materials in different biomedical applications. The biopolymer-based aerogel has unique physical, chemical, and mechanical properties and these properties are used in tissue engineering, biosensing, diagnostic, medical implant and drug delivery applications. Biocompatible and non-toxic biopolymers such as chitosan, cellulose and alginates have been used to deliver antibiotics, plants extract, essential oils and metallic nanoparticles. Antibacterial aerogels have been used in superficial and chronic wound healing as dressing sheets. This review critically analyses the utilization of biopolymer-based aerogels in antibacterial delivery. The analysis shows the relationship between their properties and their applications in the wound healing process. Furthermore, highlights of the potentials, challenges and proposition of the application of biopolymer-based aerogels is explored.

Supercritical Fluid Applications in the Design of Novel Antimicrobial Materials

Bacterial resistance to antibiotics is one of the biggest problems in the modern world. The prevention of bacterial spreading from hospitals to the community and vice versa is an issue we have to deal with. This review presents a vast potential of contemporary high-pressure techniques in the design of materials with antimicrobial activity. Scientists from all over the world came up with ideas on how to exploit extraordinary properties of supercritical fluids in the production of advantageous materials in an environmentally friendly way. The review summarizes reported methods and results.

Jet Cutting Technique for the Production of Chitosan Aerogel Microparticles Loaded with Vancomycin

Biopolymer-based aerogels can be obtained by supercritical drying of wet gels and endowed with outstanding properties for biomedical applications. Namely, polysaccharide-based aerogels in the form of microparticles are of special interest for wound treatment and can also be loaded with bioactive agents to improve the healing process. However, the production of the precursor gel may be limited by the viscosity of the polysaccharide initial solution. The jet cutting technique is regarded as a suitable processing technique to overcome this problem. In this work, the technological combination of jet cutting and supercritical drying of gels was assessed to produce chitosan aerogel microparticles loaded with vancomycin HCl (antimicrobial agent) for wound healing purposes. The resulting aerogel formulation was evaluated in terms of morphology, textural properties, drug loading, and release profile. Aerogels were also tested for wound application in terms of exudate sorption capacity, antimicrobial activity, hemocompatibility, and cytocompatibility. Overall, the microparticles had excellent textural properties, absorbed high amounts of exudate, and controlled the release of vancomycin HCl, providing sustained antimicrobial activity.