Search Results (304)

7,12-Dimethylbenzo[a]anthracene (DMBA-7,12), a highly toxic and environmentally persistent polycyclic aromatic hydrocarbon (PAH), poses significant threats to marine biodiversity and human health due to its bioaccumulation through the food chain. Conventional chromatographic methods, while achieving comparable detection limits, are hindered by the need for expensive instrumentation and prolonged analysis times, rendering them unsuitable for rapid on-site monitoring of DMBA-7,12 in marine environments. Therefore, the development of novel, efficient detection techniques is imperative. In this study, we have successfully developed an electrochemical immunosensor based on a polydopamine (PDA)–chitosan (CTs) composite interface to overcome existing technical limitations. PDA provides a robust scaffold for antibody immobilization due to its strong adhesive properties, while CTs enhances signal amplification and biocompatibility. The synergistic integration of these materials combines the high efficiency of electrochemical detection with the specificity of antigen–antibody recognition, enabling precise qualitative and quantitative analysis of the target analyte through monitoring changes in the electrochemical properties at the electrode surface. By systematically optimizing key experimental parameters, including buffer pH, probe concentration, and antibody loading, we have constructed the first electrochemical immunosensor for detecting DMBA-7,12 in seawater. The sensor achieved a detection limit as low as 0.42 ng/mL. In spiked seawater samples, the recovery rates ranged from 95.53% to 99.44%, with relative standard deviations (RSDs) ≤ 4.6%, demonstrating excellent accuracy and reliability. This innovative approach offers a cost-effective and efficient solution for the in situ rapid monitoring of trace carcinogens in marine environments, potentially advancing the field of marine pollutant detection technologies. Full article

Water quality is essential for safeguarding human health and ensuring the stability of ecosystems. Nonetheless, the rising prevalence of emerging contaminants, particularly pharmaceutical compounds, has raised serious environmental concerns due to their bioactivity, widespread use, persistence, and potential toxicity. Among these, acetaminophen (paracetamol) is one of the most frequently detected pharmaceutical pollutants in aquatic environments. Among the various degradation strategies explored, biological methods, especially those involving white-rot fungi, have shown substantial promise owing to their production of ligninolytic enzymes capable of degrading complex pollutants. This study investigates the use of laccases from Ganoderma parvulum, covalently immobilized on chitosan microspheres, for acetaminophen degradation. The immobilization involved a 10% crosslinking agent, 60-min crosslinking time, and 10,000 U/L enzyme concentration, resulting in an immobilization efficiency of 123%, 203%, and 218%, respectively. The immobilized enzymes displayed enhanced stability across pH 3–8 and temperatures between 20 and 60 °C. Biodegradation assays achieved 97% acetaminophen removal within four hours. Nuclear Magnetic Resonance (¹H NMR and COSY) confirmed structural transformation. The enzymes also retained over 95% catalytic activity after multiple reuse cycles. These findings highlight the novel application of laccases as efficient and reusable biocatalysts for pharmaceutical pollutant removal, providing valuable insights into the mechanisms of enzymatic environmental remediation. Full article

This work aims to study the catalytic properties of Fe, Cr, and Cu catalysts deposited on chitosan–silica (SBA-15) composites in liquid phase oxidation of cyclohexane (CH) with H₂O₂ and photocatalytic hydrogen evolution reaction. The catalysts were obtained by consecutive adsorption of chitosan (CS) and metal ions (Fe³⁺, Cr³⁺, Cu²⁺) on SBA-15 at ambient conditions. Characterization of the catalysts by XRD, IR spectroscopy, XPS, TEM, SEM, etc., showed the CS and metal ion adsorption on the solid support. Modification with CS provided better immobilization of the metal ions on SBA-15. The synthesized catalysts demonstrated different performance in liquid phase oxidation of cyclohexane with H₂O₂ under mild conditions at 40 °C and atmospheric pressure. Cyclohexane conversion on Fe–CS/SBA-15 (18.5%) and Cr–CS/SBA-15 (21.6%) was higher than on Cu–CS/SBA-15 (9.3%). The influence of different conditions of the reaction such as time, temperature, catalyst dosage, substrate and oxidant ratio on cyclohexane conversion in the presence of the most efficient Cr–CS/SBA-15 catalyst was also studied. The optimal reaction conditions were found to be the following: duration of reaction—4 h, temperature of reaction—50 °C, m_cat—0.03 g, a substrate/H₂O₂ ratio of 1:3. In addition, Cr–CS/SBA-15 and Fe–CS/SBA-15 catalysts were studied in a photocatalytic H₂ evolution reaction. The Fe-containing catalyst demonstrated superior efficiency in photocatalytic H₂ evolution. The total volume of hydrogen produced within 3 h was 103 mL/g. Thus, this study demonstrates that chitosan possesses promising potential in the design of the supported catalysts for cyclohexane oxidation and photocatalytic hydrogen evolution reactions. Full article

D-allulose is a rare sugar with promising applications in food and health industries, owing to its low caloric value and multiple health benefits. In this study, we systematically investigated a thermostable D-allulose 3-epimerase (TcDAEase) from Thermogemmatispora carboxidivorans for food-compatible continuous production. The enzyme exhibited remarkable thermostability, with over 70% activity retained at 80 °C, and showed broad pH tolerance across the range of 8.0 to 13.0. Notably, TcDAEase exhibited high catalytic activity toward D-allulose and D-fructose even without the addition of metal ions. Moreover, food-grade Mg²⁺ was identified as enhancing enzyme activity by 14.3%, thus ensuring compliance with Generally Recognized as Safe (GRAS) standards for food applications. To improve industrial applicability, the enzyme was immobilized using a chitosan-diatomaceous earth (DE) matrix via three-step adsorption–crosslinking–embedding strategy. The immobilized TcDAEase achieved 48.7% ± 2.4% activity recovery and retained 90.3% ± 1.5% activity over seven reaction cycles. Furthermore, continuous production of D-allulose was realized in a packed-bed reactor, operating stably at 60 °C, pH 8.0 and 5 mM Mg²⁺ for 150 days, producing 756 kg of D-allulose with a conversion yield exceeding 89.7% of the theoretical maximum. Overall, this study provides a feasible strategy for the continuous and efficient production of high-value-added D-allulose in the food industry. Full article

This study reports, for the first time, the successful application of chitosan oligosaccharide (COS) and 2-hydroxyethyl cellulose (HEC) coatings on electrospun poly(3-hydroxybutyrate) (PHB) materials for the immobilization of non-conventional yeast strains with fungal biocontrol potential. The coatings enhanced the surface wettability of PHB fibers, facilitating efficient yeast adhesion and viability maintenance. Among the tested strains, Pichia acaciae YD6 was newly isolated and characterized, while Pichia fermentans YP6 and Zygosaccharomyces bailii YE1 had previously been identified as endophytic colonizers. All three strains demonstrated high adaptability, efficient immobilization, and antagonistic activity, confirming their potential for biocontrol applications. COS-coated PHB fibers promoted greater colony expansion than those coated with HEC. Antifungal assays of the yeast-containing biocarriers showed significant inhibition of F. graminearum growth. These findings underscore the potential of PHB-based fibrous materials as sustainable, bioactive carriers for yeast immobilization, with desirable biological properties. This approach offers a promising and eco-friendly strategy for pest control and bioactive agent delivery in agricultural applications. Full article

The low effectiveness of various brain cancer treatment methods is due to a number of significant challenges. Most of them are unable to penetrate the blood–brain barrier (BBB) when drugs are administered systemically through the bloodstream. Nanoscale particles play a special role among materials capable of binding drug molecules and successfully crossing the BBB. Biopolymeric nanoparticles (NPs) demonstrate excellent biocompatibility and have the remarkable ability to modify the environment surrounding tumor cells, thereby potentially improving cellular uptake of delivery agents. In our research, nanoscale polyelectrolyte complexes (PECs) ranging in size from 56 to 209 nm were synthesized by ionic interaction of the oppositely charged polysaccharides pectin and chitosan. The structural characteristics of these complexes were carefully characterized by infrared (FTIR) and Raman spectroscopy. The immobilization efficiency of antitumor drugs was comprehensively evaluated using UV spectrophotometry. The cytotoxicity of the NPs was evaluated in the U87-MG cell line. The preliminary data indicate a significant decrease in the metabolic activity of these tumor cells. Important details on the interaction of the NPs with an endothelial layer structurally similar to the BBB were obtained by simulating the BBB using a model based on human blood vessels. Our studies allowed us to establish a significant correlation between the kinetic parameters of drug immobilization and the ratio of biopolymer concentrations in the initial compositions, which provides valuable information for future optimization of drug delivery system design. Full article

In this study, we developed an innovative method for one-step enzyme purification and immobilization utilizing polysaccharide-based microspheres through a chitosan-binding module that mediated affinity adsorption. The chitosan-binding domain derived from Paenibacillus sp. IK-5 was genetically fused with multiple target enzymes (lysine decarboxylase, glutamate oxidase, and formate dehydrogenase), all of which were successfully expressed in soluble forms. Three distinct polysaccharide microspheres with optimized surface characteristics were engineered to facilitate the concurrent purification and immobilization of these fusion enzymes. Comprehensive characterization using organic elemental analysis, fluorescence microscopy, and thermogravimetric analysis confirmed the efficient immobilization of fusion enzymes. Remarkably, the immobilized enzymes demonstrated exceptional operational stability, maintaining over 80% of their initial catalytic activity after ten consecutive reuse cycles. This study establishes a robust and versatile platform for enzyme immobilization, providing significant advantages in biocatalyst engineering applications. Full article

Implant-associated infections (IAIs) are major complications in dental and orthopedic implants, potentially compromising osseointegration and eventually causing implant loosening or removal. Thus, early prevention of bacterial adhesion and biofilm formation is critical for successful long-term osseointegration. Polyetheretherketone (PEEK) exhibits excellent physicochemical properties and an elastic modulus similar to bone tissue, making it a promising material for dental and orthopedic implants. However, its inherent lack of antibacterial properties limits its ability to prevent IAIs. Herein, an antibacterial coating with controlled drug release and excellent biocompatibility is designed by immobilizing minocycline (Mino)-doped carboxymethyl chitosan (CMCS) onto the PEEK surface via a polydopamine (PDA)-mediated Michael addition and Schiff base reaction. The coating is characterized by SEM, XPS, water contact angle measurements, and in vitro Mino release assays. Antibacterial activity is evaluated using the zone of inhibition (ZOI), turbidity, and colony counting assays, while biocompatibility is assessed through a SEM analysis of cell morphology and CCK-8 assay. The results show that the Mino-modified coating is successfully fabricated on the PEEK surface, achieving sustained Mino release for up to 14 days. Among the three Mino concentrations, the PEEK-0.5Mino group demonstrates the best balance of antibacterial activity and biocompatibility, highlighting its potential for preventing IAIs in orthopedic and dental applications. Full article

The BRCA-1 protein, recognized for its diagnostic relevance in a wide spectrum of malignancies, has been the focus of extensive investigation. In this study, an electrochemical immunosensor specifically designed for BRCA-1 detection was fabricated. The sensing platform utilizes disposable pencil graphite electrodes modified with a nanocomposite composed of gold nanoparticles (AuNPs), molybdenum disulfide (MoS₂), and chitosan (CS). This multifunctional nanostructure significantly promotes electron transfer efficiency and supports the effective immobilization of antibodies. The constructed immunosensor exhibited excellent analytical performance, with a linear detection range between 0.05 and 20 ng/mL for BRCA-1 and a notably low limit of detection at 0.04 ng/mL. The device maintained a relative standard deviation of 3.59% (n = 3), indicating strong reproducibility. In addition, a high recovery rate of 98 ± 3% was achieved in spiked serum samples, even in the presence of common electroactive interferents such as dopamine and ascorbic acid. These findings highlight the sensor’s promising applicability for the clinical detection of BRCA-1 and potentially other cancer-related biomarkers. Full article

This study investigates the regeneration, reuse, stabilization, and environmental safety of Fe–Mn polymer nanocomposites for arsenic (As) removal and their environmental safety. The regeneration performance of Fe–Mn polymer nanocomposites (PS-FMBO) used in this study was assessed through batch adsorption–desorption cycles using various eluents, including NaOH, NaOH–NaCl, and NaOH–NaOCl mixtures. The results demonstrated that 0.1 M NaOH yielded the best regeneration performance, maintaining higher adsorption efficiency over multiple cycles. Stronger desorption agents caused a significant decline in removal efficiency due to possible structural degradation of the PS-FMBO nanocomposite, suggesting that aggressive desorption conditions could compromise its long-term effectiveness. The stabilization of PS-FMBO with cement and quicklime was evaluated for immobilizing As, iron (Fe), and manganese (Mn). Leaching tests indicated that the composites effectively immobilized these contaminants, with minimal leaching observed even after prolonged aging, ensuring compliance with environmental safety regulations. Furthermore, chitosan-based foams were analyzed for their chemical stability, with leaching tests confirming low concentrations of As, Fe, and Mn, even under aggressive conditions, further reinforcing the material’s safety and environmental compliance. These findings underscore the potential of PS-FMBO composites and chitosan-based foams as sustainable materials for hazardous waste management and eco-friendly construction applications. Their ability to immobilize contaminants while maintaining structural integrity highlights their practical significance in reducing environmental pollution and advancing circular economy principles. Full article

The need for sustainable and efficient water decontamination methods has led to the increasing use of redox enzymes such as glucose oxidase (GOx). GOx immobilization on textile supports provides a promising alternative for catalyzing pollutant degradation in bio-Fenton (BF) and bio-electro-Fenton (BEF) systems. However, challenges related to enzyme stability, reusability, and environmental impact remain a concern. This communication paper outlines innovative strategies developed to address these challenges, notably the use of ecotechnologies to achieve efficient GOx immobilization while maintaining biocatalytic activity. Plasma ecoprocesses, amino-bearing biopolymer-chitosan, as well as a bio-crosslinker genipin have been used efficiently on conductive carbon and non-conductive polyester-PET nonwovens. In certain cases, immobilized GOx can retain high catalytic activity after multiple cycles, making them an effective biocatalyst for organic dye degradation (Crystal Violet and Remazol Blue) via bio-Fenton reactions, including total heterogeneous bio-Fention system. Moreover, the conductive carbon felt-based bioelectrodes successfully supported simultaneous pollutant degradation and energy generation in a BEF system. This work highlights the potential of textile-based enzyme immobilization for sustainable wastewater treatment, bio-electrochemical energy conversion, and also for bacterial deactivation. Future research will focus on optimizing enzyme stability and enhancing BEF efficiency for large-scale applications. Full article

The quantitative determination of conotoxins has great potential in the development of natural marine peptide pharmaceuticals. Considering the time-consuming sample pretreatment and expensive equipment in MS or LC-MS/MS analysis, an electrochemical sensor combined with molecularly imprinted polymer (MIP) is fabricated for the rapid monitoring of conotoxin αB-VxXXIVA to promote its pharmaceutical value and eliminate the risk of human poisoning. Electrochemically reduced graphene oxide–gold composite (rGO-Au) is modified with chitosan (CS) and glutaraldehyde (GA) to immobilize the macromolecular peptide, conotoxin αB-VxXXIVA. Subsequently, acrylamide (AAM) with a cross-linking agent, N,N′-methylene-bisacrylamide (NNMBA), is introduced into the rGO-Au electrode to form MIPs by electro-polymerization. The proposed MIP-based electrochemical sensor, PAM/αB-CTX/CS-GA/rGO-Au/SPE, exhibits satisfactory sensing performance in the detection of αB-VxXXIVA. Based on current change versus logarithm concentration, a wide linear range from 0.1 to 10,000 ng/mL and a low detection limit (LOD) of 0.014 ng/mL for this sensor are obtained. This work provides a promising method in electrochemical determination combined with MIP for the determination of macromolecular peptides. Full article

Ochratoxin A (OTA) exposure in food is very dangerous to human health. Therefore, the development of a fast and efficient technique for OTA removal has become an urgent research topic in the field of food safety. Nano Fe₃O₄ modified chitosan nanocomposite (nano-Fe₃O₄@CTS) was synthesized as a rapidly separable and safe adsorbent and was used to adsorb OTA in wine. FT-IR, XRD, and VSM characterization methods indicated that chitosan was successfully modified by Fe₃O₄ and exhibited good magnetism. The adsorption and kinetics isotherms between OTA and nano-Fe₃O₄@CTS were studied by the Langmuir equation and the pseudo-second order kinetics equation. The mechanism of OTA adsorption on nano-Fe₃O₄@CTS nanoparticles was the combined effect of physical adsorption and chemisorption. The negative ΔH°, ΔG° and ΔS° values proved that the adsorption was a spontaneous and exothermic process. Nano-Fe₃O₄@CTS with a high maximum adsorption capacity of 5018.07 ng/g at 25 °C can rapidly separate the matrix immobilized OTA from wine, and to a certain extent retains some of the wine quality after OTA removal. Full article

Chitosan-based biosorbents are particularly valuable in environmental applications, such as wastewater treatment for contaminant removal. However, several challenges remain in optimizing their production and performance related to improving adsorption efficiency, stability, scalability, cost, and sustainable sourcing for large-scale applications. The removal of Methylene Blue (MB) and Orange 16 (O16) from aqueous solutions was studied using a biosorbent derived from the waste biomass of the brewing industry, specifically Saccharomyces pastorianus immobilized into chitosan. The biosorbent (obtained by a straightforward entrapment technique) was characterized using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDAX) to evaluate its structural properties. The biosorption behavior toward organic contaminants, specifically a cationic and an anionic dye, was investigated. Key operational factors that influenced the biosorbent’s efficiency were examined, including the initial dye concentration, dye type, pH of the aqueous solution, and the amount of biosorbent used. These factors were evaluated during the initial stage of the biosorption studies to assess their impact on the overall performance and effectiveness of the biosorbent in removing the dyes from aqueous solutions. Using this eco-friendly biosorbent, the biosorption capacities obtained using the Langmuir isotherm model were 212.77 mg/g in the case of MB dye and 285.71 mg/g in the case of O16 mg/g, and the results confirmed that the biosorption process is based on a physical mechanism as suggested by the energy values of the process, E, obtained using the DR model: the obtained values of 6.09 kJ/mol (MB dye) and 7.07 kJ/mol (O16 dye) suggest a process based on electrostatic interaction bonds. These results indicate that residual biomass of Saccharomyces pastorianus, as a byproduct of a biotechnological process, can be exploited as a biosorbent by immobilization in an organic matrix (chitosan) for the retention of polluting organic species from the aqueous environment present in aqueous solutions in moderate concentrations. Full article

This study investigates the immobilization of Lactobacillus paracasei AAL (LpAAL) protein onto polyvinyl alcohol/nylon 6/chitosan nanofiber membranes using dextran polyaldehyde as a biodegradable cross-linker. Immobilization enhanced the enzyme’s stability, shifting its optimal reaction conditions from 40 °C to 45 °C and pH from 8.0 to 8.5. While immobilization slightly reduced its catalytic efficiency, it significantly improved enzyme stability and reusability. The immobilized enzyme retained 85% of its initial activity after 7 days of storage at room temperature, compared to 55% for the free enzyme. Reusability tests demonstrated that immobilized LpAAL protein maintained approximately 50% of its activity after six consecutive reaction cycles, highlighting its robustness over repeated use. These results underscore the advantages of nanofiber-based immobilization in enhancing enzyme stability and utility for industrial applications, offering a practical approach to overcoming the limitations associated with free enzyme systems. Full article