Biopolymer Aerogels Research Articles

Chitosan aerogel containing mechanically fibrillated fibroin and its model test for wound dressing

AbstractThe biopolymer aerogels of silk fibroin and chitosan composites exhibited brilliant properties such as biocompatibility, antibacterial, nontoxicity, and renewability. Silk fibroin nanofibrils (150–300 nm) can be effectively produced via a wet mechanical method. The introduction of fibroin nanofibrils into chitosan aerogels improved their bioactivity in a stimulus environment, mechanical properties, and promoted wound healing. The results of chitosan aerogels with additional fibroin aerogels revealed a high mechanical modulus (>2.5 MPa, at 80% load), high swelling ratio (>400%), and ideal exudate uptake (>100%). The obtained bio‐aerogels could be prospective for medical applications such as biomaterials and wound dressing.Highlights Green processes to produce 3D chitosan aerogels containing silk fibroin nanofibrils. Valuable properties of CS aerogels with a small weight range of mechanically fibrillated fibroin. CS/FNF aerogels exhibited greater absorption and swelling properties than CS aerogel alone.

Enhanced specific surface area and mechanical property of silk nanofibers aerogel for potential hemostasis applications

Biopolymer aerogel is a new type of material with potential applications in the biomedical field. Silk fibroin is of particular interest as a raw material with good biocompatibility and degradable. However, the low mechanical strength and small specific surface area of silk fibroin aerogels limit its further development. Herein, a fast water absorption, highly specific surface area and mechanically strong of aerogels were prepared using low crystal silk fibroin nanofibers (SNF), sol-gel process, solvent exchange and supercritical carbon dioxide (CO2) drying method. The resulting Aero-Sc displayed highly specific surface area (251 m2/g), porosity (97.6 %) and water absorption capacity (1200 %). Furthermore, with rapid water absorption and stronger erythrocyte adhesion, the Aero-Sc showed highly effective hemostasis in vitro. In vivo, animal experiments on rat liver hemorrhage model confirmed that SNF aerogels have a less blood loss (312 ± 29 mg) and faster hemostatic time (92 ± 13 s) than commercially gelatin sponge (p < 0.05). The unique properties of silk fibroin nanofibers aerogel developed in this study has great potential to be a safe and effective hemostatic medical device.

Green thermal insulators: A review into the role of biopolymer‐based aerogels in thermal insulation applications

AbstractThe need for green thermal insulation materials, such as biopolymer aerogels, has become increasingly critical in the face of escalating environmental concerns and the urgent push toward sustainable practices. The unique characteristics of biopolymer aerogels, coupled with their environmental benefits, position them as potential disruptors in the insulation industry. As research continues, addressing challenges and refining fabrication techniques will likely lead to wider adoption of these materials, contributing to a greener and more energy‐efficient built environment. This review presents the latest developments concerning the properties and versatile applications of biopolymer‐based thermal insulators as a new type of green materials. It comprehensively examines the fundamental principles of thermal insulation, factors that influence its efficacy, and the compatibility and mechanisms underlying bioaerogels within this context. The review also addresses the latest works about the utilization of different biopolymer aerogels in different thermal insulation applications and critically assesses the obstacles currently faced by biopolymer‐based aerogels and elucidates potential avenues for future advancement.Highlights Biopolymer aerogels offer a sustainable alternative in insulation. Challenges in production limit current aerogel adoption rates. Latest advancements highlight aerogels' versatile insulation applications. Future research aims to enhance biopolymer aerogel technology and use.

Synthesis and application of a new multi-functional biopolymer-based aerogel loaded with bistriazole derivative as highly efficient adsorbent and disinfectant

Herein, we exploited xanthan gum (XG) and cationic dextran (CD) in designing a novel porous aerogel (XCD) loaded with different concentrations of a new bistriazole derivative (CPSC). The CPSC was deposited into and onto the pores of aerogels. The neat aerogel removed both AB40 dye and Cu2+ efficiently. Adding 0.5 g of CPSC to the neat aerogel (XCD-0.50 sample) improved slightly the adsorption of Cu2+ and has no effect on the adsorption of AB40 dye. XCD-0.50 removed almost completely 10 mg/L of AB40 dye in 10 min using 0.5 g/L at pHi 6 while for Cu2+ longer contact time (90 min) and higher dosage (2.0 g/L) were required to remove 10 mg/L solution at pHi 5. Relative to literature, the Langmuir adsorption capacity of XCD-0.5 toward AB40 dye (436 mg/g) was the highest and toward Cu2+ (60 mg/g) was comparable to others. The aerogel XCD-0.50 was regenerable and reusable for three cycles with reasonable efficiency. By submerging a bacterial solution (106 CFU/mL) in the XCD-0.75 aerogel for 90 min, an impressive 6-log decrease in the number of bacteria was obtained under ideal circumstances. Crucially, toxicity test clearly confirmed that the prepared aerogels had non-toxic impact. Across all investigated bacterial species, XCD-0.75 continuously achieved a 6-log CFU decrease after 180 min, demonstrating its efficacy in the context of disinfection experiment. The results of the study highlight the extraordinary potential of the biopolymer aerogel loaded with CPSC as a potent adsorbent and disinfectant. They show significant removal of toxic trace elements and dyes, along with microbial reduction in industrial wastewater, underscoring the aerogel's potential use in water treatment.

Biopolymer Aerogels as Nasal Drug Delivery Systems

Biopolymer Aerogels as Nasal Drug Delivery Systems

Hollow glass microspheres embedded in porous network of chitosan aerogel used for thermal insulation and flame retardant materials

In recent years, biopolymer aerogels as thermal insulation materials have received widespread attention due to natural abundance, cost-efficiency, and environment-friendly. However, the flammability and low strength hinder its practical application. Hollow glass microspheres (HGMs) as an inorganic thermal insulation filler have been filled in biopolymer aerogels to improve flame retardancy. However, the structure formed by HGMs embedded porous network of biopolymer aerogel has rarely been investigated, which not only reduce thermal conductivity through high porosity, but also adjust the filling volume of HGMs and achieve uniform distribution through chemical cross-linking. Herein, a biopolymer aerogel composite was assembled by chitosan aerogel (CSA) and different volume of HGMs by chemical cross-linking, freeze-drying, and silylation modification processes. When the filling volume fraction of HGMs reached 40 %, a skeleton structure was initially formed. The composites with HGMs volume of 40 %–60 % exhibited low density, high porosity, low thermal conductivity, good mechanical property, and excellent flame retardancy. According to GB 8624-2012 standard for classification, the composite with 60 % HGMs achieved class A1 non-combustible.

Implantable SDF-1α-loaded silk fibroin hyaluronic acid aerogel sponges as an instructive component of the glioblastoma ecosystem: Between chemoattraction and tumor shaping into resection cavities

In view of inevitable recurrences despite resection, glioblastoma (GB) is still an unmet clinical need. Dealing with the stromal-cell derived factor 1-alpha (SDF-1α)/CXCR4 axis as a hallmark of infiltrative GB tumors and with the resection cavity situation, the present study described the effects and relevance of a new engineered micro-nanostructured SF-HA-Hep aerogel sponges, made of silk fibroin (SF), hyaluronic acid (HA) and heparin (Hep) and loaded with SDF-1α, to interfere with the GB ecosystem and residual GB cells, attracting and confining them in a controlled area before elimination. 70 µm-pore sponges were designed as an implantable scaffold to trap GB cells. They presented shape memory and fit brain cavities. Histological results after implantation in brain immunocompetent Fischer rats revealed that SF-HA-Hep sponges are well tolerated for more than 3 months while moderately and reversibly colonized by immuno-inflammatory cells. The use of human U87MG GB cells overexpressing the CXCR4 receptor (U87MG-CXCR4+) and responding to SDF-1α allowed demonstrating directional GB cell attraction and colonization of the device in vitro and in vivo in orthotopic resection cavities in Nude rats. Not modifying global survival, aerogel sponge implantation strongly shaped U87MG-CXCR4+ tumors in cavities in contrast to random infiltrative growth in controls. Overall, those results support the interest of SF-HA-Hep sponges as modifiers of the GB ecosystem dynamics acting as “cell meeting rooms” and biocompatible niches whose properties deserve to be considered toward the development of new clinical procedures. Statement of SignificanceBrain tumor glioblastoma (GB) is one of the worst unmet clinical needs. To prevent the relapse in the resection cavity situation, new implantable biopolymer aerogel sponges loaded with a chemoattractant molecule were designed and preclinically tested as a prototype targeting the interaction between the initial tumor location and its attraction by the peritumoral environment. While not modifying global survival, biocompatible SDF1-loaded hyaluronic acid and silk fibroin sponges induce directional GB cell attraction and colonization in vitro and in rats in vivo. Interestingly, they strongly shaped GB tumors in contrast to random infiltrative growth in controls. These results provide original findings on application of exogenous engineered niches that shape tumors and serve as cell meeting rooms for further clinical developments.

Solar-powered MXene biopolymer aerogels for sorption-based atmospheric water harvesting

Solar energy-powered sorption-based atmospheric water harvesting (AWH) is an innovative approach to acquiring fresh water in water-stressed areas. Here, a method was provided for combining a polyacrylamide/chitosan skeleton and an MXene solar absorber to produce a solar-powered hygroscopic polymer aerogel for atmospheric water harvesting (AWH). Solution exchange and lyophilization were combined in the preparation method. The experiments showed that the porous aerogels enabled high-performance AWH. At 90% relative humidity and 25 °C, the water sorption capacity reached 5.0 g·g−1. At a light intensity of 1 kW·m−2 for 4 h, almost all of the adsorbed water (>98%) was released due to photothermal conversion. The tensile strength exceeded 1.3 MPa. Additionally, the water collection capacity under unstable outdoor conditions was 0.92 L·kg−1 (under unstable natural light (0.11–1.01 kW ·m−2)). This method offers a straightforward, efficient, and useful solution, even under adverse environmental conditions.

Insights into the Potential of Biopolymeric Aerogels as an Advanced Soil-Fertilizer Delivery Systems.

Soil fertilizers have the potential to significantly increase crop yields and improve plant health by providing essential nutrients to the soil. The use of fertilizers can also help to improve soil structure and fertility, leading to more resilient and sustainable agricultural systems. However, overuse or improper use of fertilizers can lead to soil degradation, which can reduce soil fertility, decrease crop yields, and damage ecosystems. Thus, several attempts have been made to overcome the issues related to the drawbacks of fertilizers, including the development of an advanced fertilizer delivery system. Biopolymer aerogels show promise as an innovative solution to improve the efficiency and effectiveness of soil-fertilizer delivery systems. Further research and development in this area could lead to the widespread adoption of biopolymer aerogels in agriculture, promoting sustainable farming practices and helping to address global food-security challenges. This review discusses for the first time the potential of biopolymer-based aerogels in soil-fertilizer delivery, going through the types of soil fertilizer and the advert health and environmental effects of overuse or misuse of soil fertilizers. Different types of biopolymer-based aerogels were discussed in terms of their potential in fertilizer delivery and, finally, the review addresses the challenges and future directions of biopolymer aerogels in soil-fertilizer delivery.

Biopolymer-Polysiloxane Double Network Aerogels.

A new series of transparent aerogels of biopolymer-polysiloxane double networks is reported. Biopolymer aerogels have attracted much attention from green and sustainable aspects but suffered from strong hydrophilicity and difficulty to make homogeneous structures in nanoscale; these drawbacks are overcome by compositing with a polysiloxane network. Alginate-polymethylsilsesquioxane aerogel has high optical transparency, water repellency, comparable superinsulation property and improved bending flexibility compared to pure polymethylsilsesquioxane aerogel. The nanoscale homogeneity is realized by separating the crosslinking steps for two networks in a sequential protocol: condensation of siloxane bonds and metal-crosslinking of biopolymer. The crosslinking order, biopolymer-first or siloxane-first, and universality/limitation of biopolymer-crosslinker pairs are discussed to construct fundamental chemistry of double network systems for their further application potentials.

Biopolymer‐Polysiloxane Double Network Aerogels

AbstractA new series of transparent aerogels of biopolymer‐polysiloxane double networks is reported. Biopolymer aerogels have attracted much attention from green and sustainable aspects but suffered from strong hydrophilicity and difficulty to make homogeneous structures in nanoscale; these drawbacks are overcome by compositing with a polysiloxane network. Alginate‐polymethylsilsesquioxane aerogel has high optical transparency, water repellency, comparable superinsulation property and improved bending flexibility compared to pure polymethylsilsesquioxane aerogel. The nanoscale homogeneity is realized by separating the crosslinking steps for two networks in a sequential protocol: condensation of siloxane bonds and metal‐crosslinking of biopolymer. The crosslinking order, biopolymer‐first or siloxane‐first, and universality/limitation of biopolymer‐crosslinker pairs are discussed to construct fundamental chemistry of double network systems for their further application potentials.

Nanostructured Bioaerogels as a Potential Solution for Particulate Matter Pollution.

Particulate matter (PM) pollution is a significant environmental and public health issue globally. Exposure to high levels of PM, especially fine particles, can have severe health consequences. These particles can come from a variety of sources, including natural events like dust storms and wildfires, as well as human activities such as industrial processes and transportation. Although an extensive development in air filtration techniques has been made in the past few years, fine particulate matter still poses a serios and dangerous threat to human health and to our environment. Conventional air filters are fabricated from non-biodegradable and non-ecofriendly materials which can cause further environmental pollution as a result of their excessive use. Nanostructured biopolymer aerogels have shown great promise in the field of particulate matter removal. Their unique properties, renewable nature, and potential for customization make them attractive materials for air pollution control. In the present review, we discuss the meaning, properties, and advantages of nanostructured aerogels and their potential in particulate matter removal. Particulate matter pollution, types and sources of particulate matter, health effect, environmental effect, and the challenges facing scientists in particulate matter removal are also discussed in the present review. Finally, we present the most recent advances in using nanostructured bioaerogels in the removal of different types of particulate matter and discuss the challenges that we face in these applications.

Wet Milling of Alginate Alco‐ and Hydrogel Composites: A Facile Top‐Down Approach for Continuous Production of Aerogel Microparticles

AbstractMoving toward high‐throughput production of biopolymer aerogel microparticles, in this work, the wet milling process is applied to hydrogels and alcogels. Alcogels are then converted into aerogels by well‐established supercritical drying. Alginate and hybrid alginate/silica gels are used as a model system. As the Young's moduli of hydrogels significantly change when water is exchanged by ethanol, it is possible to study the effect of the gel stiffness on macroscopic and microstructural properties of the resulting aerogels. Influence of process parameters (milling speed and gap size) is also investigated. Smallest particles sizes and minimal changes in microstructure are obtained for completely solvent exchanged gels. The wet milling is shown to be a versatile method to obtain aerogel particles with diameters in the range 50–300 µm.

Polyurea Aerogels: Synthesis, Material Properties, and Applications.

Polyurea is an isocyanate derivative, and comprises the basis for a well-established class of polymeric aerogels. Polyurea aerogels are prepared either via reaction of multifunctional isocyanates with multifunctional amines, via reaction of multifunctional isocyanates and water, or via reaction of multifunctional isocyanates and mineral acids. The first method is the established one for the synthesis of polyurea, the third is a relatively new method that yields polyurea doped with metal oxides in one step, while the reaction of isocyanates with water has become the most popular route to polyurea aerogels. The intense interest in polyurea aerogels can be attributed in part to the low cost of the starting materials—especially via the water method—in part to the extremely broad array of nanostructural morphologies that allow study of the nanostructure of gels as a function of synthetic conditions, and in part to the broad array of functional properties that can be achieved even within a single chemical composition by simply adjusting the synthetic parameters. In addition, polyurea aerogels based on aromatic isocyanates are typically carbonizable materials, making them highly competitive alternatives to phenolic aerogels as precursors of carbon aerogels. Several types of polyurea aerogels are already at different stages of commercialization. This article is a comprehensive review of all polyurea-based aerogels, including polyurea-crosslinked oxide and biopolymer aerogels, from a fundamental nanostructure–material properties perspective, as well as from an application perspective in thermal and acoustic insulation, oil adsorption, ballistic protection, and environmental cleanup.

Superhydrophobic aerogel membrane with integrated functions of biopolymers for efficient oil/water separation

A novel type of superhydrophobic biopolymer aerogel membrane (T-SA/lignin x /rGO-MTMS) is prepared for purifying oily wastewater. • A novel type of superhydrophobic biopolymer aerogel membrane between lignin and sodium alginate (T-SA/lignin x /rGO-MTMS) was prepared. • Confirmation of cooperative interaction between lignin and sodium alginate. • Demonstration of high-efficiency cyclicity for oil/water separation. • Degradable oil/water separation membranes. Superhydrophobic membranes have been playing crucial role in efficient remediation of organic pollutants contaminated water, especially for oily discharged wastewater. Taking advantages of the inherent features of graphene oxide (GO), sodium alginate (SA) and lignin, a novel type of superhydrophobic biopolymer aerogel membrane (T-SA/lignin x /rGO-MTMS) was prepared by freeze-casting technique and subsequent chemical vapor deposition, during which trimethoxymethylsilane (MTMS) silylation growth was achieved for the supreme protuberance, leading to the formation of rough and hydrophobic surface that favorably looks like a hedgehog carrying apples. Due to the air cushion induced by cooperative interaction between rough lignin particles and SA of 3D porous network with gas as a dispersion medium, and crumpled GO nanosheets, as-fabricated membrane with integrated functions of biopolymers possessed superhydrophobic surface characteristics (WCA = 161°). More favorably, utilizing the inherent molecular features, lignin has been successfully employed to de-oxidize GO during this preparative concept. By virtue of the low-surface-energy reduced GO (rGO) and abundant protuberance, T-SA/lignin x /rGO-MTMS exhibited potential cycling performance even with 10 cycles of oil/water separation and oil sorption. This study might shed light on the value-added utilization of integrated functions of biopolymers for designing task-specific functional materials for various applications.

Geometric and finite element modeling of biopolymer aerogels to characterize their microstructural and mechanical properties

AbstractBiopolymer aerogels belong to a class of highly open‐porous cellular materials. Their macroscopic mechanical properties (such as elasticity or thermal conductivity) depend on microstructural features (namely pore size distribution (PSD), fiber diameter and solid fraction), which can be tailored by different synthesis and drying routes. The design of modern aerogel materials requires a better perception into the microstructure and its influence on the mechanical properties. To predict the material properties using simulation, it is significant to construct a geometric model which is sufficiently precise to represent the microstructure of real materials. A tessellation approach based on Voronoi diagrams is a powerful tool to model such cellular‐like materials. In this contribution, the diversified cellular morphology of aerogels is described computationally using a Voronoi tessellation‐based approach [1]. Accordingly, Voronoi tessellations are generated to create periodic representative volume elements (RVEs) resembling the microstructural properties of the cellular network. Stress‐strain curves resulting from finite element simulations of these RVEs and experiments of the aerogels under compression are compared. This work is an extension of our previous Voronoi tessellation‐based on the 2‐d description of biopolymer aerogels [2].

Hydrophobic Modification of Biopolymer Aerogels by Cold Plasma Coating.

The aim of this work was to evaluate the potential of cold plasma polymerization as a simple, fast and versatile technique for deposition of protective hydrophobic and oleophobic polymer layers on hydrophilic biopolymer aerogels. Polymerization of different fluorinated monomers (octafluorocyclobutane C4F8 and perfluoro-acrylates PFAC-6 and PFAC-8) on aerogel monoliths derived from alginate, cellulose, whey protein isolate (WPI) and potato protein isolate (PPI) resulted in fast and significant surface hydrophobization after short process times of 5 min and led to superhydrophobic surfaces with static water contact angles up to 154° after application of poly-C4F8 coatings. Simultaneous introduction of hydro- and oleophobicity was possible by deposition of perfluoro-acrylates. While the porous structure of aerogels stayed intact during the process, polymerization inside the aerogels pores led to the generation of new porous moieties and resulted therefore in significant increase in the specific surface area. The magnitude of the effect depended on the individual process settings and on the overall porosity of the substrates. A maximization of specific surface area increase (+179 m2/g) was obtained by applying a pulsed wave mode in the C4F8-coating of alginate aerogels.

A one‐pot biosynthesis of an aerogel composite based on attapulgite clay/bacterial cellulose to remove Pb 2+ ion

A one‐pot biosynthesis of an aerogel composite based on attapulgite clay/bacterial cellulose to remove Pb ²⁺ ion

Insights into the Role of Biopolymer Aerogel Scaffolds in Tissue Engineering and Regenerative Medicine.

The global transplantation market size was valued at USD 8.4 billion in 2020 and is expected to grow at a compound annual growth rate of 11.5% over the forecast period. The increasing demand for tissue transplantation has inspired researchers to find alternative approaches for making artificial tissues and organs function. The unique physicochemical and biological properties of biopolymers and the attractive structural characteristics of aerogels such as extremely high porosity, ultra low-density, and high surface area make combining these materials of great interest in tissue scaffolding and regenerative medicine applications. Numerous biopolymer aerogel scaffolds have been used to regenerate skin, cartilage, bone, and even heart valves and blood vessels by growing desired cells together with the growth factor in tissue engineering scaffolds. This review focuses on the principle of tissue engineering and regenerative medicine and the role of biopolymer aerogel scaffolds in this field, going through the properties and the desirable characteristics of biopolymers and biopolymer tissue scaffolds in tissue engineering applications. The recent advances of using biopolymer aerogel scaffolds in the regeneration of skin, cartilage, bone, and heart valves are also discussed in the present review. Finally, we highlight the main challenges of biopolymer-based scaffolds and the prospects of using these materials in regenerative medicine.

Computational design of biopolymer aerogels and predictive modelling of their nanostructure and mechanical behaviour

To address the challenge of reconstructing or designing the three-dimensional microstructure of nanoporous materials, we develop a computational approach by combining the random closed packing of polydisperse spheres together with the Laguerre–Voronoi tessellation. Open-porous cellular network structures that adhere to the real pore-size distributions of the nanoporous materials are generated. As an example, κ-carrageenan aerogels are considered. The mechanical structure–property relationships are further explored by means of finite elements. Here we show that one can predict the macroscopic stress–strain curve of the bulk porous material if only the pore-size distributions, solid fractions, and Young’s modulus of the pore-wall fibres are known a priori. The objective of such reconstruction and predictive modelling is to reverse engineer the parameters of their synthesis process for tailored applications. Structural and mechanical property predictions of the proposed modelling approach are shown to be in good agreement with the available experimental data. The presented approach is free of parameter-fitting and is capable of generating dispersed Voronoi structures.