Studies of Fe3O4-chitosan nanoparticles prepared by co-precipitation under the magnetic field for lipase immobilization

Synthesis, modifications, and applications of iron-based nanoparticles

Magnetic nanoparticles (MNPs) are appealing materials as assistant to resolve environmental pollution issues and as recyclable catalysts for the oxidative degradation of resistant contaminants. Moreover, they can significantly influence the advancement of medical applications for imaging, diagnostics, medication administration, and biosensing. On the other hand, due to unique features, excellent biocompatibility, high curie temperatures and low cytotoxicity of the Iron-based nanoparticles, they have received increasing attention in recent years. Using an external magnetic field, in which the ferrite magnetic nanoparticles (FMNPs) in the reaction mixtures can be easily removed, make them more efficient approach than the conventional method for separating the catalyst particles by centrifugation or filtration. Ferrite magnetic nanoparticles (FMNPs) provide various advantages in food processing, environmental issues, pharmaceutical industry, sample preparation, wastewater management, water purification, illness therapy, identification of disease, tissue engineering, and biosensor creation for healthcare monitoring. Modification of FMNPs with the proper functional groups and surface modification techniques play a significant role in boosting their capability. Due to flexibility of FMNPs in functionalization and synthesis, it is possible to make customized FMNPs that can be utilized in variety of applications. This review focuses on synthesis, modifications, and applications of Iron-based nanoparticles.

Magnetic-Plasmonic Nanocomposites as Versatile Substrates for Surface-enhanced Raman Scattering (SERS) Spectroscopy

Surface-enhanced Raman scattering (SERS) spectroscopy, a highly sensitive technique for detecting trace-level analytes, relies on plasmonic substrates. The choice of substrate, its morphology, and the excitation wavelength are crucial in SERS applications. To address advanced SERS requirements, the design and use of efficient nanocomposite substrates have become increasingly important. Notably, magnetic-plasmonic (MP) nanocomposites, which combine magnetic and plasmonic properties within a single particle system, stand out as promising nanoarchitectures with versatile applications in nanomedicine and SERS spectroscopy. In this review, we present an overview of MP nanocomposite fabrication methods, explore surface functionalization strategies, and evaluate their use in SERS. Our focus is on how different nanocomposite designs, magnetic and plasmonic properties, and surface modifications can significantly influence their SERS-related characteristics, thereby affecting their performance in specific applications such as separation, environmental monitoring, and biological applications. Reviewing recent studies highlights the multifaceted nature of these materials, which have great potential to transform SERS applications across a range of fields, from medical diagnostics to environmental monitoring. Finally, we discuss the prospects of MP nanocomposites, anticipating favorable developments that will make substantial contributions to various scientific and technological areas.

A Novel Recyclable Magnetic Nano-Catalyst for Fenton-Photodegradation of Methyl Orange and Imidazole Derivatives Catalytic Synthesis

A magnetite chlorodeoxycellulose/ferroferric oxide (CDC@Fe3O4) heterogeneous photocatalyst was synthesised via treated and modified cotton in two steps. The designed nanocomposites were characterised by FTIR, TGA, XRD, SEM, and VSM analyses. The Fenton-photocatalytic decomposition efficiency of the synthesised magnetic catalyst was evaluated under visible sunlight using Methyl Orange (MO) as a model organic pollutant. The impacts of several degradation parameters, including the light source, catalyst load, irradiation temperature, oxidant dose, and pH of the dye aqueous solution and its corresponding concentration on the Fenton photodegradation performance, were methodically investigated. The (CDC@Fe3O4) heterogeneous catalyst showed a remarkable MO removal rate of 97.9% at 10 min under visible-light irradiation. (CDC@Fe3O4) nanomaterials were also used in a heterogeneous catalytic optimised protocol for a multicomponent reaction procedure to obtain nine tetra-substituted imidazole derivatives. The green protocol afforded imidazole derivatives in 30 min with good yields (91-97%) at room temperature and under ultrasound irradiation. Generally, a synthesised recyclable heterogeneous nano-catalyst is a good example and is suitable for wastewater treatment and organic synthesis.

Recent applications and future prospects of magnetic biocatalysts

Magnetic biocatalysts combine magnetic properties with the catalytic activity of enzymes, achieving easy recovery and reuse in biotechnological processes. Lipases immobilized by magnetic nanoparticles dominate. This review covers an advanced bibliometric analysis and an overview of the area, elucidating research advances. Using WoS, 34,949 publications were analyzed and refined to 450. The prominent journals, countries, institutions, and authors that published the most were identified. The most cited articles showed research hotspots. The analysis of the themes and keywords identified five clusters and showed that the main field of research is associated with obtaining biofuels derived from different types of sustainable vegetable oils. The overview of magnetic biocatalysts showed that these materials are also employed in biosensors, photothermal therapy, environmental remediation, and medical applications. The industry shows a significant interest, with the number of patents increasing. Future studies should focus on immobilizing new lipases in unique materials with magnetic profiles, aiming to improve the efficiency for various biotechnological applications.

Green synthesis of iron nanoparticles: Sources and multifarious biotechnological applications

Green synthesis of iron nanoparticles is a highly fascinating research area and has gained importance due to reliable, sustainable and ecofriendly protocol for synthesizing nanoparticles, along with the easy availability of plant materials and their pharmacological significance. As an alternate to physical and chemical synthesis, the biological materials, like microorganisms and plants are considered to be less costly and environment-friendly. Iron nanoparticles with diverse morphology and size have been synthesized using biological extracts. Microbial (bacteria, fungi, algae etc.) and plant extracts have been employed in green synthesis of iron nanoparticles due to the presence of various metabolites and biomolecules. Physical and biochemical properties of biologically synthesized iron nanoparticles are superior to that are synthesized using physical and chemical agents. Iron nanoparticles have magnetic property with thermal and electrical conductivity. Iron nanoparticles below a certain size (generally 10-20 nm), can exhibit a unique form of magnetism called superparamagnetism. They are non-toxic and highly dispersible with targeted delivery, which are suitable for efficient drug delivery to the target. Green synthesized iron nanoparticles have been explored for multifarious biotechnological applications. These iron nanoparticles exhibited antimicrobial and anticancerous properties. Iron nanoparticles adversely affect the cell viability, division and metabolic activity. Iron nanoparticles have been used in the purification and immobilization of various enzymes/proteins. Iron nanoparticles have shown potential in bioremediation of various organic and inorganic pollutants. This review describes various biological sources used in the green synthesis of iron nanoparticles and their potential applications in biotechnology, diagnostics and mitigation of environmental pollutants.

Effect of Electrode Spacing on the Performance of a Membrane-Less Microbial Fuel Cell with Magnetite as an Additive

A microbial fuel cell (MFC) is a bioelectrochemical system that can be employed for the generation of electrical energy under microbial activity during wastewater treatment practices. The optimization of electrode spacing is perhaps key to enhancing the performance of an MFC. In this study, electrode spacing was evaluated to determine its effect on the performance of MFCs. The experimental work was conducted utilizing batch digesters with electrode spacings of 2.0 cm, 4.0 cm, 6.0 cm, and 8.0 cm. The results demonstrate that the performance of the MFC improved when the electrode spacing increased from 2.0 to 6.0 cm. However, the efficiency decreased after 6.0 cm. The digester with an electrode spacing of 6.0 cm enhanced the efficiency of the MFC, which led to smaller internal resistance and greater biogas production of 662.4 mL/g VS_fed. The electrochemical efficiency analysis demonstrated higher coulombic efficiency (68.7%) and electrical conductivity (177.9 µS/cm) for the 6.0 cm, which was evident from the enrichment of electrochemically active microorganisms. With regards to toxic contaminant removal, the same digester also performed well, revealing removals of over 83% for chemical oxygen demand (COD), total solids (TS), total suspended solids (TSS), and volatile solids (VS). Therefore, these results indicate that electrode spacing is a factor affecting the performance of an MFC, with an electrode spacing of 6.0 cm revealing the greatest potential to maximize biogas generation and the degradability of wastewater biochemical matter.

Recent advances in development of functional magnetic adsorbents for selective separation of proteins/peptides

Nowadays, proteins separation has attracted great attention in proteomics research. Because the proteins separation is helpful for making an early diagnosis of many diseases. Magnetic nanoparticles are an interesting and useful functional material, and have attracted extensive research interest during the past decades. Because of the excellent properties such as easy surface functionalization, tunable biocompatibility, high saturation magnetization etc, magnetic microspheres have been widely used in isolation of proteins/peptides. Notably, with the rapid development of surface decoration strategies, more and more functional magnetic adsorbents have been designed and fabricated to meet the growing demands of biological separation. In this review, we have collected recent information about magnetic adsorbents applications in selective separation of proteins/peptides. Furthermore, we present a comprehensive prospects and challenges in the field of protein separation relying on magnetic nanoparticles.

Zinc oxide nanoparticles-impregnated chitosan surfaces for covalent immobilization of trypsin: Stability & kinetic studies

Trypsin (Try, EC. 3.4.21.4) was effectively immobilized on the surface of glutaraldehyde(GA)-activated ZnO/Chitosan nanocomposite through covalent attachment via Schiff-base linkages. Size, structure, surface morphology, & percentage elemental composition of the prepared ZnO nanoparticles and chitosan-coated ZnO nanocomposite were studied by UV-Visible spectroscopy, Fourier-transform infrared spectroscopy (FTIR), X-Ray diffraction analysis (XRD), transmission electron microscopy (TEM), Scanning electron microscopy (SEM), and Energy-Dispersive X-Ray Microanalysis (EDAX) techniques. Optimal immobilization conditions (incubation time (16 h), enzyme concentration (1.8 mg/ml), and pH (7.8)) were investigated to obtain the maximum expressed activity of the immobilized trypsin. Immobilized & solubilized trypsin exhibited the optimum catalytic activity at pH 8.5, 60 °C, and pH 7.8, 45 °C respectively. Kinetic parameters (K_m, V_max) of immobilized (27.12 μM, 8.82 μM/min) & free trypsin (25.76 μM, 4.16 μM/min) were determined, indicating that efficiency of trypsin improves after immobilization. Immobilized trypsin preserved 67% of initial activity at 50 °C during 2 h of incubation & sustained nearly 50% of catalytic activity until the 9th repeated cycle of utilization. Moreover, immobilized trypsin retained 50% of enzymatic activity after 90 days of storage at 4 °C. Hence, the current findings suggest that ZnO/Chitosan-GA-Trypsin would be a promising biocatalyst for large-scale biotechnological applications.

Surface-coated magnetic nanostructured materials for robust bio-catalysis and biomedical applications-A review

BACKGROUND

Enzymes based bio-catalysis has wide range of applications in various chemical and biological processes. Thus, the process of enzymes immobilization on suitable support to obtain highly active and stable bio-catalysts has great potential in industrial applications. Particularly, surface-modified magnetic nanomaterials have garnered a special interest as versatile platforms for biomolecules/enzyme immobilization.

AIM OF REVIEW

This review spotlights recent progress in the immobilization of various enzymes onto surface-coated multifunctional magnetic nanostructured materials and their derived nano-constructs for multiple applications. Conclusive remarks, technical challenges, and insightful opinions on this field of research which are helpful to expand the application prospects of these materials are also given with suitable examples.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Nanostructured materials, including surface-coated magnetic nanoparticles have recently gained immense significance as suitable support materials for enzyme immobilization, due to their large surface area, unique functionalities, and high chemical and mechanical stability. Besides, magnetic nanoparticles are less expensive and offers great potential in industrial applications due to their easy recovery and separation form their enzyme conjugates with an external magnetic field. Magnetic nanoparticles based biocatalytic systems offer a wide-working temperature, pH range, increased storage and thermal stabilities. So far, several studies have documented the application of a variety of surface modification and functionalization techniques to circumvent the aggregation and oxidation of magnetic nanoparticles. Surface engineering of magnetic nanoparticles (MNPs) helps to improve the dispersion stability, enhance mechanical and physicochemical properties, upgrade the surface activity and also increases enzyme immobilization capabilities and biocompatibility of the materials. However, several challenges still need to be addressed, such as controlled synthesis of MNPs and clinical aspects of these materials require consistent research from multidisciplinary scientists to realize its practical applications.

Application of chitosan nanoparticles in skin wound healing

The rising prevalence of impaired wound healing and the consequential healthcare burdens have gained increased attention over recent years. This has prompted research into the development of novel wound dressings with augmented wound healing functions. Nanoparticle (NP)-based delivery systems have become attractive candidates in constructing such wound dressings due to their various favourable attributes. The non-toxicity, biocompatibility and bioactivity of chitosan (CS)-based NPs make them ideal candidates for wound applications. This review focusses on the application of CS-based NP systems for use in wound treatment. An overview of the wound healing process was presented, followed by discussion on the properties and suitability of CS and its NPs in wound healing. The wound healing mechanisms exerted by CS-based NPs were then critically analysed and discussed in sections, namely haemostasis, infection prevention, inflammatory response, oxidative stress, angiogenesis, collagen deposition, and wound closure time. The results of the studies were thoroughly reviewed, and contradicting findings were identified and discussed. Based on the literature, the gap in research and future prospects in this research area were identified and highlighted. Current evidence shows that CS-based NPs possess superior wound healing effects either used on their own, or as drug delivery vehicles to encapsulate wound healing agents. It is concluded that great opportunities and potentials exist surrounding the use of CSNPs in wound healing.

Efficient Synthesis of Biodiesel Catalyzed by Chitosan-Based Catalysts

Catalysts play an important role in the preparation of biodiesel. It is of great significance to study catalysts with high efficiency, low cost, and easy preparation. Compared with the homogeneous catalyst system, the heterogeneous catalyst is easy to separate and has a better catalytic effect. In heterogeneous catalysts, supports and preparation methods have important effects on the dispersion of active centers and the overall performance of catalysts. However, the supports of existing solid catalysts have defects in porosity, structural uniformity, stability, and specific surface area, and the preparation methods cannot stabilize covalent bonds or ionic bonds to bind catalytic sites. Considering the activity, preparation method, and cost of the catalyst, biomass-based catalyst is the best choice, but the specific surface area of the biomass-based catalyst is relatively low, the distribution of active centers is uneven, and it is easy to lose. Therefore, the hybrid carrier of biomass-based catalyst and other materials can not only improve the specific surface area but also make the distribution of active centers uniform and the catalytic activity better. Based on this, we summarized the application of chitosan hybrid material catalysts in biodiesel. The preparation, advantages and disadvantages, reaction conditions, and so on of chitosan-based catalysts were mainly concerned. At the same time, exploring the effects of different types of chitosan-based catalysts on the preparation of biodiesel and exploring the process technology with high efficiency and low consumption is the focus of this paper.

Heavy Metal Adsorption Using Magnetic Nanoparticles for Water Purification: A Critical Review

Research on contamination of groundwater and drinking water is of major importance. Due to the rapid and significant progress in the last decade in nanotechnology and its potential applications to water purification, such as adsorption of heavy metal ion from contaminated water, a wide number of articles have been published. An evaluating frame of the main findings of recent research on heavy metal removal using magnetic nanoparticles, with emphasis on water quality and method applicability, is presented. A large number of articles have been studied with a focus on the synthesis and characterization procedures for bare and modified magnetic nanoparticles as well as on their adsorption capacity and the corresponding desorption process of the methods are presented. The present review analysis shows that the experimental procedures demonstrate high adsorption capacity for pollutants from aquatic solutions. Moreover, reuse of the employed nanoparticles up to five times leads to an efficiency up to 90%. We must mention also that in some rare occasions, nanoparticles have been reused up to 22 times.

Different strategies for the lipase immobilization on the chitosan based supports and their applications

Immobilized enzymes have received incredible interests in industry, pharmaceuticals, chemistry and biochemistry sectors due to their various advantages such as ease of separation, multiple reusability, non-toxicity, biocompatibility, high activity and resistant to environmental changes. This review in between various immobilized enzymes focuses on lipase as one of the most practical enzyme and chitosan as a preferred biosupport for lipase immobilization and provides a broad range of studies of recent decade. We highlight several aspects of lipase immobilization on the surface of chitosan support containing various types of lipase and immobilization techniques from physical adsorption to covalent bonding and cross-linking with their benefits and drawbacks. The recent advances and future perspectives that can improve the present problems with lipase and chitosan such as high-price of lipase and low mechanical resistance of chitosan are also discussed. According to the literature, optimization of immobilization methods, combination of these methods with other techniques, physical and chemical modifications of chitosan, co-immobilization and protein engineering can be useful as a solution to overcome the mentioned limitations.

Cross-linked Enzyme Aggregates of Fibrinolytic Protease BC1 Immobilized on Magnetic Chitosan Nanoparticles (CLEAs-Fib-mChi): Synthesis, Purification, and Characterization

Bacterial fibrinolytic proteases achieved more attention in the prevention and treatment of cardiovascular diseases, so purification, characterization, and activity enhancement are of prime importance. In this study, a fibrinolytic serine metalloprotease was purified from the culture supernatant from Bacillus sp. BC1. It was purified to homogeneity by a two-step procedure with a 24-fold increase in specific activity and a 33.1% yield. It showed 28 kDa molecular weight, while its optimal pH and temperature were obtained 8 and 50-60 °C. The cross-link enzyme aggregates of this fibrinolytic BC1 successfully immobilized on magnetic chitosan nanoparticles. A 52% activity enhancement was obtained by immobilized enzyme at pH 6.0, compared to free protease. K_m values of the free and immobilized proteases were obtained about 0.638 and 0.61 mg/ml, respectively. The free and immobilized enzymes did not show any activity concerning transferrin, γ-globulins, and hemoglobin, as blood plasma proteins. The in vitro blood clot lysis test of the free and immobilized proteases showed a maximum of 42 and 50% clot lysis, which was comparatively higher than that revealed by streptokinase and heparin at the same condition. These results indicated that the free and immobilized proteases have the potential to be effective fibrinolytic agents.

Nanostructured materials as a host matrix to develop robust peroxidases-based nanobiocatalytic systems

Nanostructured materials constitute an interesting and novel class of support matrices for the immobilization of peroxidase enzymes. Owing to the high surface area, robust mechanical stability, outstanding optical, thermal, and electrical properties, nanomaterials have been rightly perceived as immobilization matrices for enzyme immobilization with applications in diverse areas such as nano-biocatalysis, biosensing, drug delivery, antimicrobial activities, solar cells, and environmental protection. Many nano-scale materials have been employed as support matrices for the immobilization of different classes of enzymes. Nanobiocatalysts, enzymes immobilized on nano-size materials, are more stable, catalytically robust, and could be reused and recycled in multiple reaction cycles. In this review, we illustrate the unique structural/functional features and potentialities of nanomaterials-immobilized peroxidase enzymes in different biotechnological applications. After a comprehensive introduction to the immobilized enzymes and nanocarriers, the first section reviewed carbonaceous nanomaterials (carbon nanotube, graphene, and its derivatives) as a host matrix to constitute robust peroxidases-based nanobiocatalytic systems. The second half covers metallic nanomaterials (metals, and metal oxides) and some other novel materials as host carriers for peroxidases immobilization. The next section vetted the potential biotechnological applications of the resulted nanomaterials-immobilized robust peroxidases-based nanobiocatalytic systems. Concluding remarks, trends, and future recommendations for nanomaterial immobilized enzymes are also given.

Immunomagnetic separation: An effective pretreatment technology for isolation and enrichment in food microorganisms detection

The high efficiency and accurate detection of foodborne pathogens and spoilage microorganisms in food are a task of great social, economic, and public health importance. However, the contamination levels of target bacteria in food samples are very low. Owing to the background interference of food ingredients and negative impact of nontarget flora, the establishment of efficient pretreatment techniques is very crucial for the detection of food microorganisms. With the significant advantages of high specificity and great separation efficiency, immunomagnetic separation (IMS) assay based on immunomagnetic particles (IMPs) has been considered as a powerful system for the separation and enrichment of target bacteria. This paper mainly focuses on the development of IMS as well as their application in food microorganisms detection. First, the basic principle of IMS in the concentration of food bacteria is presented. Second, the effect of different factors, including the sizes of magnetic particles (MPs), immobilization of antibody and operation parameters (the molar ratio of antibody to MPs, the amount of IMPs, incubation time, and bacteria concentration) on the immunocapture efficiency of IMPs are discussed. The performance of IMPs in different food samples is also evaluated. Finally, the combination of IMS and various kinds of detection methods (immunology-based methods, nucleic acid-based methods, fluorescence methods, and biosensors) to detect pathogenic and spoilage organisms is summarized. The challenges and future trends of IMS are also proposed. As an effective pretreatment technique, IMS can improve the detection sensitivity and shorten their testing time, thus exhibiting broad prospect in the field of food bacteria detection.

Immobilization of horseradish peroxidase on Fe3O4 nanoparticles for enzymatic removal of endocrine disrupting chemicals

The modified Fe₃O₄ nanoparticles were used as a support for the immobilization of horseradish peroxidase (HRP). The immobilized enzyme (HRP@Fe₃O₄) was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier-transform infrared spectrometer (FTIR), and vibration sample magnetometer (VSM). According to the results, the optimum concentration of glutaraldehyde (GA) and agitation time were 300 μL and 7 h. HRP was well loaded on the surface of the Fe₃O₄. There was no change in the crystal structure of HRP@Fe₃O₄ compared with Fe₃O₄. The removals of bisphenol A (BPA) and 17α-ethinylestradiol (EE2) using HRP@Fe₃O₄ had been investigated. The degradation efficiencies of BPA and EE2 catalyzed by HRP@Fe₃O₄ were higher than that of soluble HRP. In addition, HRP@Fe₃O₄ can be reused through magnetic separation. After the fifth repeated use, the removal efficiencies of BPA and EE2 were up to 56% and 48%, respectively. Batch studies of catalyzed oxidation and coagulation on the degradation of BPA and EE2 in the presence of humic acid (HA) were also investigated. The order of the removal efficiencies was HRP+PACl (polyaluminum chloride)+SDS (lauryl sodium sulfate)>HRP+PACl>HRP>HRP+PAM (Polyacrylamide)>HRP+PAM+SDS. The coagulation effect of HRP@Fe₃O₄ and PACl was better than that of HRP@Fe₃O₄ and PAM. The removals of BPA and EE2 were 90.3% and 64.5% by use HRP@Fe₃O₄ and PACl as coagulant, while the removals were 78.7% and 57.6% by use HRP@Fe₃O₄ and PAM as coagulant. SDS had a positive effect on PACl, while a negative effect on PAM. Moreover, the products generated by enzymatic oxidation reaction can be effectively removed after coagulation.

Fe3O4@chitosan Microspheres Coating as Cytoprotective Exoskeletons for the Enhanced Production of Butyric Acid With Clostridium tyrobutyricum Under Acid Stress

The introduction of inorganic nano-materials may endow microbial cells with unique new features, including greater resistance to adverse abiotic stress. The aim of this work was to enhance the acid tolerance of Clostridium tyrobutyricum ATCC 25755 by coating cells with self-assembled Fe₃O₄@chitosan (Fe₃O₄@CS) microspheres, and thereby increase the production of butyric acid. The optimal coating efficiency of 81.19% was obtained by systematically optimizing the three operational parameters temperature, rpm and mass ratio, which were determined to be 37°C, 80 rpm and 1:2, respectively. Physicochemical characterization was used to assess the superparamagnetism, thermostability and subsize of Fe₃O₄@CS attached to the cells. Compared to free cells, C. tyrobutyricum coated with Fe₃O₄@CS (CtFC) exhibited stronger acid tolerance at low pH. At a pH of 4 or 5, the levels of ROS, MDA, LDH, and SOD caused by the acid environment in free cells were significant higher than in CtFC. Moreover, without adding NaOH, CtFC fermentation showed a higher butyric acid titer (37.60 vs. 31.56 g/L) compared to free-cell fermentation. At the same time, an average butyric acid yield of 0.46 g/g in each repeated-batch fermentation was also obtained by taking advantage of the biocatalyst’s reusability and convenient separation from the fermentation broth via an external magnetic force. Overall, the developed CtFC illustrates a new paradigm for developing an economical and reusable biocatalyst for industrial application in butyric acid production.

Encapsulation of HRP Enzyme onto a Magnetic Fe3O4 Np–PMMA Film via Casting with Sustainable Biocatalytic Activity

Horseradish peroxidase (HRP) enzyme was effectively encapsulated onto an Fe3O4 nanoparticle–polymethyl methacrylate (PMMA) film via the casting method. The HRP was immobilized on the 0.5% Fe3O4Np–PMMA film and characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscopy. Moreover, the reusability, thermal stability, optimum pH, optimum temperature, the influence of metal ions, and the effects of detergent and organic solvent were investigated. After optimizing the immobilization conditions, the highest efficiency of the immobilized enzyme was 88.4% using 0.5% Fe3O4Np–PMMA. The reusability of the immobilized HRP activity was 78.5% of its initial activity after being repeatedly used for 10 cycles. When comparing the free and immobilized forms of the HRP enzyme, changes in the optimum temperature and optimum pH from 30 to 40 °C and 7.0 to 7.5, respectively, were observed. The Km and Vmax for the immobilized HRP were estimated to be 41 mM, 0.89 U/mL for guaiacol and 5.84 mM, 0.66 U/mL for H2O2, respectively. The high stability of the immobilized HRP enzyme was obtained using metal ions, a high urea concentration, isopropanol, and Triton X-100. In conclusion, the applicability of immobilized HRP involves the removal of phenol in the presence of hydrogen peroxide, therefore, it could be a potential catalyst for the removal of wastewater aromatic pollutants.

Temperature selectivity for single phase hydrothermal synthesis of PEG-400 coated magnetite nanoparticles

Temperature plays a vital role in the hydrothermal synthesis of the nanoparticles. Herein, we have provided a very detailed spin dynamic investigation on the varying size Fe₃O₄ nanoparticles using FMR technique.

A detailed investigation on interactions between magnetite nanoparticles functionalized with aminated chitosan and a cell model membrane

Magnetite nanoparticles are promising materials for application in magnetic resonance imaging, targeted drug delivery, enzyme immobilization and cancer therapies based on hyperthermia thanks to their biocompatibility, wide chemical affinity and superparamagnetic properties. However, there is still the lack of the knowledge of interactions between magnetite nanoparticles covered with the bioactive polymers and biological cells. In order to fulfil this gap, we have investigated interactions of newly synthetized magnetite nanoparticles functionalized with aminated chitosan (Fe₃O₄-aminated chitosan) and a model biological membrane made of dipalmitoylphosphatidylcholine (DPPC) using a Langmuir technique. Surface pressure-mean area per DPPC molecule isotherms and Brewster angle microscope images (BAM) recorded during compression of the two-component Fe₃O₄-aminated chitosan:DPPC films revealed the strong influence of the Fe₃O₄-aminated chitosan nanoparticles on the stability, phase state and structure of the phospholipid membrane. The studies on the adsorption/incorporation process of the Fe₃O₄-aminated chitosan nanoparticles showed that they can adsorb/incorporate into the DPPC model membrane at the surface pressure corresponding to this present in the cellular membrane under the biological conditions (35 mN·m^-1). The number of the adsorbed/incorporated Fe₃O₄-aminated chitosan nanoparticles can be regulated by the nanoparticles concentration in the neighbourhood of the DPPC model membrane even at high surface pressure of 35 mN·m^-1.

Iron oxide nanoparticles: Diagnostic, therapeutic and theranostic applications

Many different iron oxide nanoparticles have been evaluated over the years, for a wide variety of biomedical applications. We here summarize the synthesis, surface functionalization and characterization of iron oxide nanoparticles, as well as their (pre-) clinical use in diagnostic, therapeutic and theranostic settings. Diagnostic applications include liver, lymph node, inflammation and vascular imaging, employing mostly magnetic resonance imaging but recently also magnetic particle imaging. Therapeutic applications encompass iron supplementation in anemia and advanced cancer treatments, such as modulation of macrophage polarization, magnetic fluid hyperthermia and magnetic drug targeting. Because of their properties, iron oxide nanoparticles are particularly useful for theranostic purposes. Examples of such setups, in which diagnosis and therapy are intimately combined and in which iron oxide nanoparticles are used, are image-guided drug delivery, image-guided and microbubble-mediated opening of the blood-brain barrier, and theranostic tissue engineering. Together, these directions highlight the versatility and the broad applicability of iron oxide nanoparticles, and indicate the integration in future medical practice of multiple iron oxide nanoparticle-based materials.

A Review on Nanoparticles as Boon for Biogas Producers—Nano Fuels and Biosensing Monitoring

Nanotechnology has an increasingly large impact on a broad scope of biotechnological, pharmacological and pure technological applications. Its current use in bioenergy production from biomass is very restricted. The present study is based on the utilization of nanoparticles as an additive to feed bacteria that break down natural substances. The novel notion of dosing ions using modified nanoparticles can be used to progress up biogas production in oxygen free digestion processes. While minute nanoparticles are unstable, they can be designed to provide ions in a controlled approach, so that the maximum enhancement of biogas production that has been reported can be obtained. Nanoparticles are dissolved in a programmed way in an anaerobic atmosphere and are supplied in a sustainable manner to microbiotic organisms responsible for the degradation of organic material, which is a role that fits them well. Therefore, biogas fabrication can be increased up to 200%, thereby increasing the degradation of organic waste.

Magnetic nanoparticles as versatile carriers for enzymes immobilization: A review

Enzymes are highly efficient biocatalysts and widely employed in biotechnological sectors. However, lack of (re)-purification and efficient recovery of enzymes are among the most critical and challenging aspects, which render them enormously expensive for industrial exploitability. Aiming to tackle these challenges, magnetic nanoparticles (MNPs) have gained a special place as versatile carriers and supporting matrices for immobilization purposes, owing to the exceptional properties of MNPs, such as large surface area, large surface-to-volume ratio, and mobility and high mass transference. More importantly, they can also be easily separated and recovered by applying an external magnetic field. Apart from their biocompatible micro-environment, the utilization of such MNPs represents a noteworthy green chemistry approach, since it lengthens the biocatalyst lifetime through multiple recovery cycles. According to the literature evidence, various modification and/or functionalization approaches have been developed to produce MNPs for the effective immobilization of a broad variety of industrially important enzymes and biomolecules with improved characteristics. Enzymes immobilized on MNPs displayed a wide-working pH and temperature range, as well as, improved thermal and storage stabilities than that of their pristine counterparts. Co-immobilization of multi-enzymes could also be accomplished through nanoparticle-based approaches. This review presents an updated outlook on the development and characterization of MNPs, in particular, iron-based MNPs-derived nano-constructs as support materials for enzyme immobilization.

Asparaginase conjugated magnetic nanoparticles used for reducing acrylamide formation in food model system

Acrylamide is a potent carcinogen and neurotoxin formed by the Maillard reaction when l-asparagine reacts with starch at high temperature. It is formed in food materials mainly deep fried and bakery products. Enzymatic pretreatment of these food products with asparaginase enzyme leads to reduction in acrylamide. However, enzymatic process is quite expensive due to high cost, low catalytic efficiency as well as problem with enzyme reusability. Present work deals with these problems by exploring l-asparaginase from Bacillus aryabhattai. Asparaginase enzyme was immobilized on APTES modified magnetic nanoparticles. It was found to be more than three-fold increase their thermal stability from free enzyme and retained 90% activity after fifth cycle. The immobilized enzyme also showed better affinity towards its substrate. During pretreatment of asparagine in a starch-asparagine food model system and it was clearly demonstrated that asparaginase nanoconjugates had reduced the formation of acrylamide by more than 90% within 30 min.

Magnetic nanoparticles: a versatile carrier for enzymes in bio-processing sectors

Many industrial processes experience the advantages of enzymes which evolved the demand for enzymatic technologies. The enzyme immobilisation technology using different carriers has trustworthy applications in industrial biotechnology as these techniques encompass varied advantages such as enhanced stability, activity along with reusability. Immobilisation onto nanomaterial is highly favourable as it includes almost all aspects of science. Among the various techniques of immobilisation, the uses of nanoparticles are remarkably well perceived as these possess high-specific surface area leading to high enzyme loadings. The magnetic nanoparticles (MNPs) are burgeoning in the field of immobilisation as it possess some of the unique properties such as high surface area to volume ratio, uniform particle size, biocompatibility and particularly the recovery of enzymes with the application of an external magnetic field. Immobilisation of industrially important enzymes onto nanoparticles offers overall combined benefits. In this review, the authors here focus on the current scenario in synthesis and functionalisation of MNPs which makes it more compatible for the enzyme immobilisation and its application in the biotechnological industries.

Iron Oxide Nanoparticles for Biomedical Applications: A Perspective on Synthesis, Drugs, Antimicrobial Activity, and Toxicity

Medical applications and biotechnological advances, including magnetic resonance imaging, cell separation and detection, tissue repair, magnetic hyperthermia and drug delivery, have strongly benefited from employing iron oxide nanoparticles (IONPs) due to their remarkable properties, such as superparamagnetism, size and possibility of receiving a biocompatible coating. Ongoing research efforts focus on reducing drug concentration, toxicity, and other side effects, while increasing efficacy of IONPs-based treatments. This review highlights the methods of synthesis and presents the most recent reports in the literature regarding advances in drug delivery using IONPs-based systems, as well as their antimicrobial activity against different microorganisms. Furthermore, the toxicity of IONPs alone and constituting nanosystems is also addressed.

High removal performance of a magnetic FPA90-Cl anion resin for bromate and coexisting precursors: kinetics, thermodynamics, and equilibrium studies

In this study, the FPA90-Cl resin was magnetized with supported Fe₃O₄ particles using a chemical co-precipitation method and its removal performance of bromate and coexisting precursors was explored. The magnetized FPA90-Cl resin was structurally characterized by SEM, FT-IR, and XRD. The effects of the initial concentrations, temperature, and resin dosage on bromate and bromide ion removal in drinking water were investigated using batch experiments. The magnetized FPA90-Cl resin exhibited a high removal efficiency for bromate and bromide ions at three initial concentrations, and the residual bromate concentrations were under the maximum contaminant level (MCL) of 10 μg L^-1 after 80 min. The adsorption data of bromate and bromide ion could be well described by a pseudo-first-order kinetic model (R² ˃ 0.98). The bromate removal alone was further studied by varying the initial solution pH, temperature, and competitive anions. The results showed that the magnetized FPA90-Cl resin could be used over a wide pH range (4.0-9.0). The maximum sorption capacity of the magnetized FPA90-Cl resin for bromate reached 132.83 mg g^-1 at 298 K. The Freundlich and Redlich-Peterson isotherm models fit the bromate adsorption equilibrium better (R² ˃ 0.99) than the Langmuir isotherm model (R² ˃ 0.98). The thermodynamic analysis showed that the bromate adsorption process was endothermic. The negative ΔG and positive ΔS indicated that the process was spontaneous and that randomness increased after adsorption, respectively. The competition of coexisting anions with bromate was in the order of SO₄^2- > CO₃^2- > Cl^- > NO₃^- > HCO₃^- > PO₄^3-. Additionally, the magnetized FPA90-Cl resin could maintain a high bromate and bromide ion adsorption capacity after five cycles of regeneration by a 0.1 M NaCl solution. Graphical abstract ᅟ.

Design of epoxy-functionalized Fe3O4@MCM-41 core-shell nanoparticles for enzyme immobilization

The scope of our research was to prepare the organosilane-modified Fe₃O₄@MCM-41 core-shell magnetic nanoparticles, used for L-ASNase immobilization and explored screening of immobilization conditions such as pH, temperature, thermal stability, kinetic parameters, reusability and storage stability. In this content, Fe₃O₄ core-shell magnetic nanoparticles were prepared via co-precipitation method and coated with MCM-41. Then, Fe₃O₄@MCM-41 magnetic nanoparticles were functionalized by (3-glycidyloxypropyl) trimethoxysilane (GPTMS) as an organosilane compound. Subsequently, L-ASNase was covalently immobilized on epoxy-functionalized Fe₃O₄@MCM-41 magnetic nanoparticles. The immobilized L-ASNase had greater activity at high pH and temperature values. It also maintained >92% of the initial activity after incubation at 55 °C for 3 h. Regarding kinetic values, immobilized L-ASNase showed a higher Vmax and lower Km compared to native L-ASNase. In addition, it displayed excellent reusability for 12 successive cycles. After 30 days of storage at 4 °C and 25 °C, immobilized L-ASNase retained 54% and 26% of its initial activities while native L-ASNase lost about 68% and 84% of its initial activity, respectively. As a result, the immobilization of L-ASNase onto magnetic nanoparticles may provide an advantage in terms of removal of L-ASNase from reaction media.

Synthesis, characterization and application of lipase-conjugated citric acid-coated magnetic nanoparticles for ester synthesis using waste frying oil

In the present work, magnetic nanoparticles (MNPs) were prepared by chemical precipitation of trivalent and divalent iron ions which were functionalized using citric acid. The bacterial isolate Staphylococcus epidermidis KX781317 was isolated from oil-contaminated site. The isolate produced lipase, which was purified and immobilized on magnetic nanoparticles (MNPs) for ester synthesis from waste frying oil (WFO). The characterization of MNPs employed conventional TEM, XRD and FTIR techniques. TEM analysis of MNPs showed the particle size in the range of 20-50 nm. FTIR spectra revealed the binding of citric acid to Fe₃O₄ and lipase on citric acid-coated MNPs. The citric acid-coated MNPs and lipase-conjugated citric acid-coated MNPs had similar XRD patterns which indicate MNPs could preserve their magnetic properties. The maximum immobilization efficiency 98.21% of lipase-containing citric acid-coated MNPs was observed at ratio 10:1 of Cit-MNPs:lipase. The pH and temperature optima for lipase conjugated with Cit-MNPs were 7 and 35 °C, respectively. Isobutanol was found to be an effective solvent for ester synthesis and 1:2 ratio of oil:alcohol observed significant for ester formation. The ester formation was determined using TLC and the % yield of ester conversion was calculated. The rate of ester formation is directly proportional to the enzyme load. Formed esters were identified as isobutyl laurate ester and isobutyl myristate ester through GC-MS analysis.