Maria Marinela Lazar

The development of multifunctional, bio-based materials capable of simultaneously addressing microbial contamination and inorganic pollutants is of increasing interest for sustainable water purification. In this study, xanthan gum (XG)/lignin(LN) double-interpenetrating network (DN) cryogels were prepared and investigated as porous, multifunctional materials for antimicrobial applications and water purification. The cryogel architecture combines the abundant oxygen-containing functional groups of XG and LN with an interconnected porous network generated under cryogenic conditions. The prepared networks were comprehensively characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), dynamic vapor sorption (DVS), swelling analysis, and uniaxial mechanical testing to evaluate their structural, morphological, physicochemical, and mechanical properties. Their Cu²⁺ sorption performance was subsequently assessed by atomic absorption spectroscopy (AAS), and the experimental equilibrium data were analyzed using the Langmuir, Freundlich, and Sips isotherm models. The single-network (SN) XG-based materials exhibited Cu²⁺ sorption capacities of 62.13–109.81 mg/g, whereas the DN cryogels showed higher capacities of 111.87–120.84 mg/g. The Sips model provided the best description of the equilibrium data, with (R²) values of 0.991–0.994 and substantially lower (χ²) values than the Langmuir and Freundlich models, indicating heterogeneous sorption sites with finite saturation capacity. Importantly, the Cu²⁺-loaded SN and DNs exhibited sorption efficiency toward sulfate ions, demonstrating their potential for sequential contaminant removal. Sulfate sorption capacities reached 694.53 mg/g for the SN.X2/Cu²⁺ composite and up to 812.53 mg/g for the DN.XL3/Cu²⁺ composite. In addition, the prepared materials demonstrated antimicrobial activity against two Gram-negative (Escherichia coli, Salmonella Typhimurium) and two Gram-positive (Staphylococcus aureus, Listeria monocytogenes) bacterial strains. The results demonstrate that XG/LN DN cryogels combine effective metal-ion and sulfate sorption with antimicrobial activity, providing promising bio-based platforms for water purification and potentially extending the functional lifetime of the material through sequential contaminant removal.

It is known that the controlled release of anticancer drugs with low molecular weight from drug delivery systems (DDSs) based on polysaccharides such as chitosan (CS) still encounter certain difficulties because of the high hydrophilicity of the carrier. The release rate is very fast, with a burst release that is usually obvious. Therefore, finding novel systems to carry and release low molecular weight drugs such as 5-fluorouracil (5-FU) is still of interest. The impact of chitosan (CS) characteristics (deacetylation degree and molar mass), and concentration as well as of the strategy employed to fabricate porous nanocomposites CS–laponite (LAP), on the physicochemical properties of CS-LAP sponges was first investigated in the paper. Information about the incorporation of LAP within the CS-LAP nanocomposites was obtained by EDX and FTIR spectroscopy. The influence of the fabrication conditions on the physical cross-linking was evidenced first by the swelling of the composite sponges at equilibrium in distilled water, with lower values of the swelling ratio found for the composites prepared with one freeze-drying (1FD) step, than of those prepared with 2FD steps. The elastic modulus ranged between 6 and 21 kPa for CS-LAP composites prepared with 1FD, and between 2 and 10 kPa for the nanocomposites prepared with 2FD steps. The physicochemical properties of CS-LAP nanocomposite sponges were correlated with their behavior in the loading and in vitro release of 5-FU as a function of pH. It was found that the CS-LAP composites with the highest swelling ratio exhibited the fastest release of 5-FU in simulated gastric fluid (pH 2.0), with the cumulative release in the range of 85–100%, in about 60 min, at 37 °C. The CS-LAP composites with the lowest swelling ratio, displayed the slowest release rate of drug. The drug release from the double component composites was accompanied by the carrier dissolution/disintegration. To retard the release of 5-FU in the gastric environment, the drug was sealed in the porous CS-LAP nanocomposites by simple complexation of the free positive charges of CS with carboxymethylcellulose as polyanion. These systems kept their integrity at pH 2.0, pH 6.8 and phosphate buffer with pH 7.4, and released 5-FU in a controlled manner, making them suitable systems for delivery of 5-FU in both the stomach and small intestine.

The impact of chitosan (CS) characteristics (deacetilation degree and molar mass), and concentration as well as of the strategy employed to fabricate porous nanocomposites CS-laponite (LAP), on the physicochemical properties of CS-LAP sponges was investigated in the paper. Information about the incorporation of LAP within the CS-LAP nanocomposites were obtained by EDX and FTIR spectroscopy. The influence of the fabrication conditions on the physical cross-linking was evidenced first by the swelling of the composite sponges at equilibrium in distilled water, with the values of the swelling ratio of about 6-18, for the CS-LAP composites prepared with one freeze drying (1FD) step, and of about 22-40, for the composites prepared with 2FD steps. The average pore size and pore size distribution were evaluated using software assisted analysis of SEM micrographs. The elastic modulus ranged between 6 - 21 kPa for CS-LAP composites prepared with 1FD, and between 2 - 10 for the nanocomposites prepared with 2FD steps. The physicochemical properties of CS-LAP nanocomposite sponges were correlated with their behavior in the loading and in vitro release of 5-fluorouracil (5-FU) as a function of pH. It was found that the CS-LAP composites with the highest swelling ratio exhibited the fastest release of 5-FU in simulated gastric fluid (pH 2.0), with the cumulative release in the range of 85 – 100%, in about 60 min, at 37 oC. The CS-LAP composites with the lowest swelling ratio, prepared by 1FD strategy, displayed the slowest release rate of drug. The drug release from the double component composites was accompanied by the carrier dissolution/disintegration. To retard the release of 5-FU in the gastric environment, the drug was sealed in the porous CS-LAP nanocomposites by simple complexation of the free positive charges of CS with carboxymethylcellulose as polyanion. These systems kept their integrity in pH 2.0, pH 6.8 and phosphate buffer with pH 7.4, and released 5-FU in a controlled manner making them suitable systems for delivery of 5-FU in both the stomach and small intestine.

In this work, hydrogel nanocomposites, as films, were prepared by embedding cerium oxide nanoparticles (CeO₂NPs) within xanthan gum (Xn)/poly(vinylalcohol) (PVA) matrices. Their physicochemical properties were tuned by adjusting the ratio between components and thermal treatment conditions. The cross-linking of the polymer network was confirmed by attenuated total reflectance–Fourier transform infrared (ATR-FTIR), thermal analysis, and swelling behavior. Morphological features were evaluated by atomic force microscopy (AFM), scanning electron microscopy (SEM), while optical properties were investigated by UV–Vis spectroscopy. Undoped films displayed high transparency (~80% transmittance at 400 nm), with thermal cross-linking determined only slight yellowing and negligible changes in absorption edge (300 ± 2 nm). In contrast, CeO₂NPs incorporation increased reflectance and introduced a new absorption threshold around 400 ± 2 nm, indicating nanoparticle–matrix interactions that modify optical behavior. Sorption studies with Methylene Blue (MB) and Crystal Violet (CV) dyes highlighted the influence of nanoparticle content and cross-linking on functional performance, with thermally treated samples showing the highest efficiency (~97–98% MB and 71–83% CV removal). Overall, the results demonstrate how structural tailoring and cross-linking control the characteristics of Xn/PVA/CeO₂ nanocomposites, providing insight into their design as multifunctional hydrogel materials for environmental applications.

This work addresses the environmental challenge represented by persistent triphenylmethane dyes in aquatic systems through the development of chitosan (CS)–zeolite nanocomposite cryogels for the adsorption of chrome azurol S (CAS), as model dye. Nanocomposite cryogels were prepared via cryogelation at −20 °C with systematic variation in cross-linker concentration and zeolite content to modulate the network architecture and sorption performance. Comprehensive physicochemical characterization (SEM, EDX, FTIR) demonstrated that an intermediate cross-linker content (7.5 wt.% GA) combined with moderate zeolite loading (20 wt.%) yielded cryogels with the highest gel fraction yield and a homogeneous, highly interconnected macroporous structure. Swelling experiments at pH 1.2 revealed rapid water uptake equilibrium within 10 min, whereas adsorption isotherm analysis indicated that CAS sorption followed the Freundlich model, consistent with multilayer physical adsorption. The highest CAS adsorption capacity was achieved by CSGA5Z40 (250.81 mg g⁻¹), indicating that low cross-linking combined with high zeolite loading maximizes uptake. These findings demonstrate that chitosan–zeolite nanocomposite cryogels are promising, reusable, and tunable adsorbents for sustainable removal of persistent dyes from wastewater.

Porous hydrogels have brought more advantages than conventional hydrogels when used as chromatographic materials, controlled release vehicles for drugs and proteins, matrices for immobilization or separation of molecules and cells, or as scaffolds in tissue engineering. Polysaccharide-based porous hydrogels, in particular, can address challenges related to bioavailability, solubility, stability, and targeted delivery of natural antioxidant compounds. Their porous structure enables the facile encapsulation and controlled release of these compounds, enhancing their therapeutic effectiveness. In this context, in the present study, the cryogelation technique has been adopted to prepare novel dextran (Dx)-based porous hydrogels embedding polyphenol-rich natural extract from Picea abies spruce bark (SBE). The entrapment of the SBE within the Dx network was proved by FTIR, SEM, and energy-dispersive X-ray spectroscopy (EDX). SEM analysis showed that entrapment of SBE resulted in denser cryogels with smaller and more uniform pores. Swelling kinetics confirmed that higher concentrations of Dx, EGDGE, and SBE reduced water uptake. The release studies demonstrated the effective stabilization of SBE in the Dx-based cryogels, with minimal release irrespective of the approach selected for SBE incorporation, i.e., during synthesis (~3–4%) or post-synthesis (~15–16%). In addition, the encapsulation of SBE within the Dx network endowed the hydrogels with remarkable antioxidant and antimicrobial properties. These porous biomaterials could have broad applications in areas such as biomedical engineering, food preservation, and environmental protection, where stability, efficacy, and safety are paramount.

Polysaccharides have recently attracted growing attention as adsorbents for various pollutants, since they can be extracted from a variety of renewable sources at low cost. An interesting hydrophilic and biodegradable polysaccharide is dextran (Dx), which is well-known for its applications in the food industry and in medicine. To extend the application range of this biopolymer, in this study, we investigated the removal of crystal violet (CV) and methylene blue (MB) dyes from an aqueous solution by Dx-based cryogels using the batch technique. The cryogel adsorbents, consisting of cross-linked Dx embedding a polyphenolic (PF) extract of spruce bark, were prepared by the freeze-thawing approach. It was shown that the incorporation of PF into the Dx-based matrix induced a decrease in porosity, pore sizes and swelling ratio values. Moreover, the average pore sizes of the DxPF cryogels loaded with dyes further decreased from 42.30 ± 7.96 μm to 23.68 ± 2.69 μm, indicating a strong interaction between the functional groups of the cryogel matrix and those of the dye molecules. The sorption performances of the DxPF adsorbents were evaluated in comparison to those of the Dx cryogels and of the PF extract. The experimental sorption capacities of the DxPF cryogel adsorbents were higher in comparison to those of the Dx cryogels and the PF extract. The DxPF cryogels, particularly those with the highest PF contents (sample DxPF2), demonstrated sorption capacities of 1.2779 ± 0.0703 mmol·g⁻¹, for CV, and 0.3238 ± 0.0121 mmol·g⁻¹, for MB. The sorption mechanisms were analyzed using mathematical models, including Langmuir, Freundlich, Sips and Dubinin–Radushkevich isotherms, and kinetic models, like pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich and intra-particle diffusion (IPD). The sorption process was best described by the Sips isotherm and PSO kinetic models, indicating chemisorption as the dominant mechanism. This study outlines the importance of developing advanced renewable materials for environmental applications.

Environmental contamination with pesticides occurs at a global scale as a result of prolonged usage and, therefore, their removal by low-cost and environmentally friendly systems is actively demanded. In this context, our study was directed to investigate the feasibility of using some self-assembled hydrogels, comprising chitosan (CS) and carboxymethylcellulose (CMC) or dialdehyde (DA)-CMC, for the removal of four complex fungicide formulations, namely Melody Compact (MC), Dithane (Dt), Curzate Manox (CM), and Cabrio^®Top (CT). Porous CS/CMC and CS/DA-CMC hydrogels were prepared as discs by combining the semi-dissolution acidification sol-gel transition method with a freeze-drying approach. The obtained CS/CMC and CS/DA-CMC hydrogels were characterized by gel fraction yield, FTIR, SEM, swelling kinetics, and uniaxial compression tests. The batch-sorption studies indicated that the fungicides’ removal efficiency (RE%) by the CS/CMC hydrogels was increased significantly with increasing sorbent doses reaching 94%, 93%, 66% and 48% for MC, Dt, CM and CT, respectively, at 0.2 g sorbent dose. The RE values were higher for the hydrogels prepared using DA-CMC than for those prepared using non-oxidized CMC when initial fungicide concentrations of 300 mg/L or 400 mg/L were used. Our results indicated that CS/DA-CMC hydrogels could be promising biosorbents for mitigating pesticide contamination of aqueous environments.

The use of polysaccharides with good film-forming properties in food packaging systems is a promising area of research. Xanthan gum (XG), an extracellular polysaccharide, has many industrial uses, including as a common food additive (E415). It is an effective thickening agent, emulsifier, and stabilizer that prevents ingredients from separating. Nevertheless, XG-based polymer films have some disadvantages, such as poor mechanical properties and high hydrophilic features, which reduce their stability when exposed to moisture and create difficulties in processing and handling. Thus, the objective of this work was to stabilize a XG matrix by cross-linking it with glycerol diglycidyl ether, 1,4-butanediol diglycidyl ether, or epichlorohydrin below the freezing point of the reaction mixture. Cryogelation is an ecological, friendly, and versatile method of preparing biomaterials with improved physicochemical properties. Using this technique, XG-based cryogels were successfully prepared in the form of microspheres, monoliths, and films. The XG-based cryogels were characterized by FTIR, SEM, AFM, swelling kinetics, and compressive tests. A heterogeneous morphology with interconnected pores, with an average pore size depending on both the nature of the cross-linker and the cross-linking ratio, was found. The use of a larger amount of cross-linker led to both a much more compact structure of the pore walls and to a significant decrease in the average pore size. The uniaxial compression tests indicated that the XG-based cryogels cross-linked with 1,4-butanediol diglycidyl ether exhibited the best elasticity, sustaining maximum deformations of 97.67%, 90.10%, and 81.80%, respectively.

The introduction of selective recognition sites toward certain heavy metal ions (HMIs) is a great challenge, which has a major role when the separation of species with similar physicochemical features is considered. In this context, ion-imprinted polymers (IIPs) developed based on the principle of molecular imprinting methodology, have emerged as an innovative solution. Recent advances in IIPs have shown that they exhibit higher selectivity coefficients than non-imprinted ones, which could support a large range of environmental applications starting from extraction and monitoring of HMIs to their detection and quantification. This review will emphasize the application of IIPs for selective removal of transition metal ions (including HMIs, precious metal ions, radionuclides, and rare earth metal ions) from aqueous solution by critically analyzing the most relevant literature studies from the last decade. In the first part of this review, the chemical components of IIPs, the main ion-imprinting technologies as well as the characterization methods used to evaluate the binding properties are briefly presented. In the second part, synthesis parameters, adsorption performance, and a descriptive analysis of solid phase extraction of heavy metal ions by various IIPs are provided.