Nanoporous furfuryl-imine-chitosan fibers as a new pathway towards eco-materials for CO2 adsorption

Biopolymeric Nanocomposites for CO2 Capture

Carbon dioxide (CO2) impacts the greenhouse effect significantly and results in global warming, prompting urgent attention to climate change concerns. In response, CO2 capture has emerged as a crucial process to capture carbon produced in industrial and power processes before its release into the atmosphere. The main aim of CO2 capture is to mitigate the emissions of greenhouse gas and reduce the anthropogenic impact on climate change. Biopolymer nanocomposites offer a promising avenue for CO2 capture due to their renewable nature. These composites consist of biopolymers derived from biological sources and nanofillers like nanoparticles and nanotubes, enhancing the properties of the composite. Various biopolymers like chitosan, cellulose, carrageenan, and others, possessing unique functional groups, can interact with CO2 molecules. Nanofillers are incorporated to improve mechanical, thermal, and sorption properties, with materials such as graphene, carbon nanotubes, and metallic nanoparticles enhancing surface area and porosity. The CO2 capture mechanism within biopolymer nanocomposites involves physical absorption, chemisorption, and physisorption, driven by functional groups like amino and hydroxyl groups in the biopolymer matrix. The integration of nanofillers further boosts CO2 adsorption capacity by increasing surface area and porosity. Numerous advanced materials, including biopolymeric derivatives like cellulose, alginate, and chitosan, are developed for CO2 capture technology, offering accessibility and cost-effectiveness. This semi-systematic literature review focuses on recent studies involving biopolymer-based materials for CO2 capture, providing an overview of composite materials enriched with nanomaterials, specifically based on cellulose, alginate, chitosan, and carrageenan; the choice of these biopolymers is dictated by the lack of a literature perspective focused on a currently relevant topic such as these biorenewable resources in the framework of carbon capture. The production and efficacy of biopolymer-based adsorbents and membranes are examined, shedding light on potential trends in global CO2 capture technology enhancement.

Theoretical-Experimental Approach of Chitosan/Quaternized Chitosan Nanofibers' Behavior in Wound Exudate Media

This study aimed to investigate the behavior of chitosan/quaternized chitosan fibers in media mimicking wound exudates to understand their capacities as wound dressing. Fiber analysis of the fibers using dynamic vapor sorption proved their ability to adsorb moisture up to 60% and then to desorb it as a function of humidity, indicating their outstanding breathability. Dissolution analyses showed that quaternized chitosan leached from the fibers in water and PBS, whereas only small portions of chitosan were solubilized in water. In media containing lysozyme, the fibers degraded with a rate determined by their composition and pH, reaching a mass loss of up to 47% in media of physiologic pH. Notably, in media mimicking the wound exudate during healing, they adsorbed moisture even when their mass loss due to biodegradation was high, whereas they were completely degraded in the media of normal tissues, indicating bioabsorbable dressing capacities. A mathematical model was constructed, which characterized the degradation rate and morphology changes of chitosan/quaternized chitosan fibers through analyses of dynamics in scale space, using the Theory of Scale Relativity. The model was validated using experimental data, making it possible to generalize it to the degradation of other biopolymeric systems that address wound healing.

Mesoporous chitosan nanofibers loaded with norfloxacin and coated with phenylboronic acid perform as bioabsorbable active dressings to accelerate the healing of burn wounds

The paper reports new chitosan-based nanofibers, designed to address the healing of burn wounds. To this aim, mesoporous chitosan fiber mats were prepared by electrospinning using poly(ethylene oxide) as sacrificial additive, followed by loading with norfloxacin and coating with an antifungal agent via dynamic imine bonds. Dynamic vapor sorption experiment proved intra-fiber mesopores around 2.7 nm, and UV-vis, FTIR, and NMR spectroscopy confirmed the norfloxacin embedding and the imination reaction. SEM, AFM and POM techniques displayed semicrystalline nanofibers with average diameter around 170 nm entangled into a non-woven mat. Their mesoporous nature favored a rapid adsorption of fluids up to 17 g/g, and a biodegradation rate fitting the wound healing rate, i.e. up to 30 % mass loss in media of pH characteristic to wound exudate and total degradation in that characteristic to normal dermis. The composite fibers released the NFX and 2FPBA in a controlled manner, and showed antimicrobial activity against gram positive, gram negative and fungal strains. They had no cytotoxic effect on normal human dermal fibroblasts, and showed biocompatibility on experimental rats. The investigation of wound healing ability on second/third-degree burn model in rats revealed wound closure and total restoration of the fully functional dermis and epidermis.

Biodegradable trimethyl chitosan nanofiber mats by electrospinning as bioabsorbable dressings for wound closure and healing

The paper aimed to prepare quaternary chitosan-based nanofibers as bioabsorbable wound dressings. To this aim, fully biodegradable chitosan/N,N,N-trimethyl chitosan (TMC) nanofibers were designed and prepared via electrospinning, using poly(ethylene glycol) as sacrificial additive. The new biomaterials were structurally and morphologically characterized by FTIR and NMR spectroscopy, thermogravimetric analysis, X-ray diffraction and scanning electron microscopy, and their properties required for wound dressings application were investigated and discussed in detail. Thus, the nanofiber behavior was investigated by swelling, dynamic vapor sorption, and in vitro biodegradation in media mimicking the wound exudate. The mechanical properties were analysed from the stress-strain curves, the bioadhesivity from the texture analysis and the mucoadhesivity from the Zeta potential and transmittance measurements. The antimicrobial activity was assessed against S. aureus and E. coli strains, and the biocompatibility was tested in vitro on normal human dermal fibroblasts, and in vivo on rats. The application of the fiber mats with the best balance of properties as dressings on deep burn wound models in rats showed wound closure and active healing, with fully restoration of epithelia. It was concluded that the combination of chitosan with TMC into nanofibers provides new potential bioabsorbable wound dressing, opening new perspectives in regenerative medicine.

Quaternized chitosan/chitosan nanofibrous mats: An approach toward bioactive materials for tissue engineering and regenerative medicine

Chitosan based nanofibers are emerging biomaterials with a plethora of applications, especially in medicine and healthcare. Herein, binary quaternized chitosan/chitosan fibers are reported for the first time. Their preparation strategy consisted in the electrospinning of ternary chitosan/quaternized chitosan/poly(ethylene oxide) solutions followed by the selective removal of poly(ethylene oxide). Their morphology and performances were systematically investigated and discussed in detail. It was found that the fibers had reversible water vapor adsorption/desorption and showed swelling degrees similar to commercial wound dressings. They presented good mechanical properties and the content of quaternized chitosan modulated their bioadhesion, mucoadhesion and biodegradation rate and conferred them strong antimicrobial activity. Tests on normal human fibroblasts confirmed their safely use in contact with tissues and the biocompatibility investigation on rats showed no harmful effect when subcutaneous implanted. All these proved the binary quaternized chitosan/chitosan fibers as bioactive materials suitable for tissue regeneration, wound healing and drug delivery systems.

From Hazardous Waste to Green Applications: Selective Surface Functionalization of Waste Cigarette Filters for High-Performance Robust Triboelectric Nanogenerators and CO2 Adsorbents

This article reports a novel and rational approach to convert waste cigarette filters (CFs), one of the largest sources of ocean pollution, into high-performance triboelectric nanogenerators (TENGs) and efficient CO₂-capturing adsorbents. CFs are plasticized cellulose acetate, which take several years to degrade. To revalorize these fibers, selective amine surface functionalization is performed (10PAL-20T-CFs). For the proof of concept, when the modified fibers are employed in a TENG, it could generate an output voltage (96.63 V) and current (9.37 μA) that are, respectively, 43 and 8 times higher than those obtained employing the pristine CFs for the nanogenerator. The proposed TENG displays an instantaneous peak power of 3.75 mW, which is higher than that of many recently reported TENGs made from cellulose materials. Moreover, the TENG displayed outstanding durability to humidity and high-performance stability when it is subjected to cyclic loading (i.e., 12,000 cycles of loading-unloading). A 9 cm² TENG could effectively light up 100 or more colored light-emitting diodes when it is manually pressed. Finally, the modified filter fibers show an excellent CO₂ adsorption capacity of 1.93 mmol/g, which is 9.2 times higher than that obtained using the pristine fibers. These results demonstrate that hazardous wastes such as CFs can be upcycled into valuable resources.

Carbon Dioxide Capture through Physical and Chemical Adsorption Using Porous Carbon Materials: A Review

Due to rapid industrialization and urban development across the globe, the emission of carbon dioxide (CO2) has been significantly increased, resulting in adverse effects on the climate and ecosystems. In this regard, carbon capture and storage (CCS) is considered to be a promising technology in reducing atmospheric CO2 concentration. Among the CO2 capture technologies, adsorption has grabbed significant attention owing to its advantageous characteristics discovered in recent years. Porous carbon-based materials have emerged as one of the most versatile CO2 adsorbents. Numerous research activities have been conducted by synthesizing carbon-based adsorbents using different precursors to investigate their performances towards CCS. Additionally, amine-functionalized carbon-based adsorbents have exhibited remarkable potential for selective capturing of CO2 in the presence of other gases and humidity conditions. The present review describes the CO2 emission sources, health, and environmental impacts of CO2 towards the human beings, options for CCS, and different CO2 separation technologies. Apart from the above, different synthesis routes of carbon-based adsorbents using various precursors have been elucidated. The CO2 adsorption selectivity, capacity, and reusability of the current and applied carbon materials have also been summarized. Furthermore, the critical factors controlling the adsorption performance (e.g., the effect of textural and functional properties) are comprehensively discussed. Finally, the current challenges and future research directions have also been summarized.

Imination of Microporous Chitosan Fibers-A Route to Biomaterials with "On Demand" Antimicrobial Activity and Biodegradation for Wound Dressings

Microporous chitosan nanofibers functionalized with different amounts of an antimicrobial agent via imine linkage were prepared by a three-step procedure including the electrospinning of a chitosan/PEO blend, PEO removal and acid condensation reaction in a heterogeneous system with 2-formylphenylboronic acid. The fibers’ characterization was undertaken keeping in mind their application to wound healing. Thus, by FTIR and ¹H-NMR spectroscopy, it was confirmed the successful imination of the fibers and the conversion degree of the amine groups of chitosan into imine units. The fiber morphology in terms of fiber diameter, crystallinity, inter- and intra-fiber porosity and strength of intermolecular forces was investigated using scanning electron microscopy, polarized light microscopy, water vapor sorption and thermogravimetric analysis. The swelling ability was estimated in water and phosphate buffer by calculating the mass equilibrium swelling. The fiber biodegradation was explored in five media of different pH, corresponding to different stages of wound healing and the antimicrobial activity against the opportunistic pathogens inflicting wound infection was investigated according to standard tests. The biocompatibility and bioadhesivity were studied on normal human dermal fibroblast cells by direct contact procedure. The dynamic character of the imine linkage of the functionalized fibers was monitored by UV-vis spectroscopy. The results showed that the functionalization of the chitosan microporous nanofibers with antimicrobial agents via imine linkage is a great route towards bio-absorbable wound dressings with “on demand” antimicrobial properties and biodegradation rate matching the healing stages.

Amphiphilic chitosan-g-poly(trimethylene carbonate) - A new approach for biomaterials design

The paper presents the synthesis and characterization of poly(trimethylene carbonate) grafted chitosan as a new water soluble biopolymer suitable for in vivo applications. The synthesis was performed via ring-opening polymerization of 1,3-dioxan-2-one (trimethylene carbonate) (TMC) monomer, initiated by the functional groups of chitosan in the presence of toluene as solvent/swelling agent. By varying the molar ratio between the glucosamine units of chitosan and TMC, a series of chitosan derivatives with different content of poly(trimethylene carbonate) chains was synthetized. The structural characterization of the polymers was realized by FTIR and ¹H NMR spectroscopy and their solubility was assessed in water and in organic solvents as well. The biocompatibility was investigated by MTS assay on Normal Human Dermal Fibroblasts, and the biodegradability was evaluated in lysozyme buffer solution. Further, the surface properties of the polymer films were analyzed by polarized optical microscopy, atomic force microscopy and water-to-air contact angle measurements. It was established that, by 5% substitution of chitosan with poly(trimethylene carbonate) chains having an average polymerization degree of 7, a water soluble polymer can be attained. Compared to the pristine chitosan, it has improved biocompatibility in solution and moderate wettability and higher biodegradability rate in solid state, pointing its suitability for in vivo applications.

Electrospinning of chitosan-based nanofibers: from design to prospective applications

Chitosan is a biopolymer originating from renewable resources, with great properties which make it an attractive candidate for plenty of applications of contemporary interest. By manufacturing chitosan into nanofibers using the electrospinning method, its potential is amplified due to the enhancement of the active surface and the low preparation cost. Many attempts were made with the aim of preparing chitosan-based nanofibers with controlled morphology targeting their use for tissue engineering, wound healing, food packaging, drug delivery, air and water purification filters. This was a challenging task, which resulted in a high amount of data, sometimes with apparent contradictory results. In this light, the goal of the paper is to present the main routes reported in the literature for chitosan electrospinning, stressing the advantages and disadvantages of each of them. Special emphasis is placed on the influence of various electrospinning parameters on the morphological characteristics of the fibers and their suitability for distinct applications.

A Theoretical Model for Release Dynamics of an Antifungal Agent Covalently Bonded to the Chitosan

The aim of the study was to create a mathematical model useful for monitoring the release of bioactive aldehydes covalently bonded to the chitosan by reversible imine linkage, considered as a polymer-drug system. For this purpose, two hydrogels were prepared by the acid condensation reaction of chitosan with the antifungal 2-formyl-phenyl-boronic acid and their particularities; influencing the release of the antifungal aldehyde by shifting the imination equilibrium to the reagents was considered, i.e., the supramolecular nature of the hydrogels was highlighted by polarized light microscopy, while scanning electron microscopy showed their microporous morphology. Furthermore, the in vitro fungicidal activity was investigated on two fungal strains and the in vitro release curves of the antifungal aldehyde triggered by the pH stimulus were drawn. The theoretical model was developed starting from the hypothesis that the imine-chitosan system, both structurally and functionally, can be assimilated, from a mathematical point of view, with a multifractal object, and its dynamics were analyzed in the framework of the Scale Relativity Theory. Thus, through Riccati-type gauges, two synchronous dynamics, one in the scale space, associated with the fungicidal activity, and the other in the usual space, associated with the antifungal aldehyde release, become operational. Their synchronicity, reducible to the isomorphism of two SL(2R)-type groups, implies, by means of its joint invariant functions, bioactive aldehyde compound release dynamics in the form of "kink-antikink pairs" dynamics of a multifractal type. Finally, the theoretical model was validated through the experimental data.