Immobilization Strategy Research Articles

Synergetic effects of hydrothermal treatment on the behavior of toxic sludge-modified geopolymer: Immobilization of cerium and lead, textural characteristics, and mechanical efficiency

Geopolymers have been subjected as a promising strategy for heavy metals immobilization due to their sustainability (environmental and energy saving). This study proposed a novel hydrothermal technology for the solidification/stabilization of lead and cerium present in a sludge resulting from the glass polishing process. Slag and fly-ash (50wt.%slag + 50wt.%fly-ash) activated with 6 wt% NaOH solution were used as base materials for geopolymer fabrication. The sludge was incorporated in the fabricated geopolymeric composite as a fly-ash replacement (10, 20 and 30 wt%). The impact of sludge incorporation and different curing regimes (humidity at 20 °C and 80 °C for 28-days and hydrothermal treatment at 3 and 6 bar for 1, 2, 6, 12 and 24 hrs) on the mechanical and textural characteristics as well as the formed phases were investigated via compression test, N2-adsorption/desorption technique, SEM/EDX, TGA/DSC and XRD. Moreover, the efficiency of the immobilization process was examined by determining the concentration of lead and cerium in the leachate solution (0.1 M HNO3 and 0.1 M CH3COOH) using Inductively Coupled Plasma Mass Spectroscopy to ensure the safety of developed composites. The results indicated that autoclaving at 6 bar/6hrs greatly returned the strength values for all hardened geopolymers, particularly the composite containing 50wt.%slag + 40wt.%fly-ash + 10wt.%sludge; its strength values were 22, 46 and 60 MPa at 20 °C/28 days, 80 °C/28 days and 6 bar/6hrs, respectively. The enthalpy change calculated by the DSC technique has the highest value (122.2 J/g) at 6 bar/6hrs, indicating the formation of additional hydration products. Hydrothermal treatment technology has proven its worth in immobilizing heavy metals in geopolymeric materials; curing at 6 bar/6hrs for specimen containing 30wt.%sludge decreased lead concentration by 95.2 and 97.8 % and cerium by 98.2 and 99.6 % in leachate solutions (HNO3 and CH3COOH, respectively). This may be attributed to the transformation of lead and cerium into insoluble Ce2Si2O7 and Pb3SiO5 as detected by XRD that are physically encapsulated in a cross-linked geopolymer structure. Furthermore, due to pore structure rearrangement that shifted to micro/mesoporous (2–50 nm) under the steam condition with a high BET surface area (31.7 m2/g) and low BJH average pore diameter (10.01 nm).

A 3D printable synthetic hydrogel as an immobilization matrix for continuous synthesis with fungal peroxygenases

Development of a novel immobilization strategy using synthetic 3D printable hydrogels for flow biocatalysis.

Cyclic voltammetry, square wave voltammetry or electrochemical impedance spectroscopy? Interrogating electrochemical approaches for the determination of electron transfer rates of immobilized redox proteins

In this article, we cross-examine three well-established electrochemical approaches, namely cyclic voltammetry (CV), cyclic square-wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) to dissect the electron transfer (ET) rate of electrostatically immobilized cytochrome c on Ag electrodes. A detailed analysis supported by simulations of redox transition provided three distinct values for the heterogeneous electron transfer (HET) rate constant of cyt c interfaced on COOH-terminated C10-long alkanethiol, i.e., kHET= 47.8 (±2,91) s−1 in CV, kHET= 64.8 (±1,27) s−1 in SWV, and kHET= 26.5 s−1 in EIS. We discuss the obtained discrepancies obtained from electrochemical methods and compare them with the data from spectro-electrochemical experiments. A comprehensive selection list is created from which the most applicable approach can be chosen for studying proteins of interest. CV is most applicable to study the interfaced proteins exhibiting kHET of ca. 0.5 - 70 s−1, SWV is suitable for a broader range of kHET of 5 – 120 s−1 and EIS for kHET of 0.5 to 5 s−1 if alkanethiols are used as immobilization strategy.

Immobilizing ultrasmall Pt nanocrystals on 3D interweaving BCN nanosheet-graphene networks enables efficient methanol oxidation reaction.

Currently, the state-of-the-art anode catalysts employed in direct methanol fuel cells (DMFCs) consist of nanosize Pt dispersed on a carbonaceous support; however, the relatively weak Pt-carbon interfacial interactions severely affect their overall electrocatalytic activity and service life. Herein, we demonstrate a convenient and robust stereo-assembly strategy for the efficient immobilization of ultrasmall Pt nanocrystals on 3D interweaving porous B-doped g-C3N4 nanosheet-graphene networks (Pt/BCN-G) by combining thermal annealing and solvothermal processes. This delicate configuration endowed the resulting hybrid nanoarchitecture with unusual textural merits, including 3D crosslinked porous skeletons, well-separated ultrathin nanosheets, rich B and N species, homogeneous Pt dispersion, stable heterointerface, and high electrical conductivity. Consequently, the 3D Pt/BCN-G nanoarchitecture with an optimized composition exhibited a large electrochemically active surface area of up to 121.2 m2 g-1, high mass activity of 1782.2 mA mg-1, superior poison tolerance, and excellent cycling stability towards the electrooxidation of methanol, all of which exceeded that of the reference Pt/graphene, Pt/BCN, Pt/carbon nanotube, Pt/carbon black, and Pt/g-C3N4 catalysts.

Hydrogel-Based Multi-enzymatic System for Biosynthesis.

Biosynthesis involving multi-enzymatic reactions is usually an efficient and economic method to produce plentiful important molecules. To increase the product yield in biosynthesis, the involved enzymes can be immobilized to carriers for enhancing enzyme stability, increasing synthesis efficiency and improving enzyme recyclability. Hydrogels with three-dimensional porous structures and versatile functional groups are promising carriers for enzyme immobilization. Herein, we review the recent advances of the hydrogel-based multi-enzymatic system for biosynthesis. First, we introduce the strategies of enzyme immobilization in hydrogel, including the pros and cons of the strategies. Then we overview the recent applications of the multi-enzymatic system for biosynthesis, including cell-free protein synthesis (CFPS) and non-protein synthesis, especially high value-added molecules. In the last section, we discuss the future perspective of the hydrogel-based multi-enzymatic system for biosynthesis.

Advances in high abundance protein molecular imprinting techniques in human serum

The detection of protein biomarkers is crucial for early disease diagnosis. However, these biomarkers are present at low levels in serum, and the detection signal is easily interfered with by high levels of proteins. These factors pose major challenges for direct biomarker detection by existing technologies; thus, sample pre-treatments are performed as the best solution. Molecularly imprinted polymers have excellent properties of good binding ability, high selectivity and low cost, making this technique one of the best for serum pre-treatment. This review discusses the recent research status and development of bulk and surface imprinting techniques for high-abundance proteins. Furthermore, this paper emphasizes the research overview and progress of substrate and template selection, template immobilization technology and strategies to control the thickness of imprinted polymers when using the surface imprinting technique. Finally, the main challenges of molecular imprinting technique (MIT) application for high-abundance proteins and the future direction of this field are highlighted.

Covalent conjugation of proteins onto fluorescent single-walled carbon nanotubes for biological and medical applications.

Single-walled carbon nanotubes (SWCNTs) have optical properties that are conducive for biological applications such as sensing, delivery, and imaging. These applications necessitate the immobilization of macromolecules that can serve as therapeutic drugs, molecular templates, or modulators of surface interactions. Although previous studies have focused on non-covalent immobilization strategies, recent advances have introduced covalent functional handles that can preserve or even enhance the SWCNT optical properties. This review presents an overview of covalent sidewall modifications of SWCNTs, with a focus on the latest generation of "sp3 defect" modifications. We summarize and compare the reaction conditions and the reported products of these sp3 chemistries. We further review the underlying photophysics governing SWCNT fluorescence and apply these principles to the fluorescence emitted from these covalently modified SWCNTs. Finally, we provide an outlook on additional chemistries that could be applied to covalently conjugate proteins to these chemically modified, fluorescent SWCNTs. We review the advantages of these approaches, emerging opportunities for further improvement, as well as their implications for enabling new technologies.

An electrochemical immunosensor based on a carboxylated multiwalled carbon nanotube-silver nanoparticle-chitosan functional layer for the detection of fipronil.

Fipronil (FP) is a very effective phenylpyrazole insecticide and is now widely used in agriculture. At the same time, the water and soil in the environment are polluted by FP. For the rapid detection of FP toxicants in food and the environment, we have designed an entirely novel electrochemical immunosensor that employs the combined functionalities of a cMWCNTs-AgNPs-CS-FAb-BSA layer to modify an SPCE by the freeze-drying technique. The high porosity of chitosan (CS) coupled with an excellent electron transfer enabled by the cMWCNTs and AgNPs increased the surface area for anti-fipronil (FAb) antibody immobilization and enhanced the current signal of the immunosensor. Cyclic voltammetry (CV) was applied for the quantitative determination of FP under optimized conditions (0.1 M PBS, pH 7.5, 35 °C incubation temperature, and 40 min incubation duration). The modified electrochemical immunosensor displayed excellent analytical performance, including a wide linear concentration range from 0.1 to 1000 ng mL-1 with a very low limit of detection of 0.021 ng mL-1 and good reproducibility (RSD = 2.58%, n = 6), stability (80.4% sensitivity after 5 days), and selectivity. Not only could the modified electrochemical immunosensor be applied in the FP residue analysis of agricultural products, but the present immobilization strategy can also potentially be applied to different biomolecules.

Laser-induced immobilization of an amorphous iron-phosphate/Fe3O4 composite on nickel foam for efficient water oxidation.

A laser-induced immobilization strategy is applied to prepare an amorphous iron-phosphate/Fe3O4 (L-FePO) composite on a nickel foam (NF) support. By laser-irradiating an iron hydrogen phosphate (FeHP) precursor, a melting and oxidation process leads to the generation of L-FePO with hierarchical pores and an amorphous structure. L-FePO shows exceptional electrocatalytic performance for the OER in an alkaline electrolyte, demonstrating an overpotential of 256 mV at 100 mA cm-2, a Tafel slope of 71 mV dec-1, and good stability over 100 h. The active Fe3O4, partially dissolved phosphate, and newly formed FeOOH species provide abundant active sites, contributing to the excellent OER performance.

Microbial Lignocellulolytic Enzymes for the Effective Valorization of Lignocellulosic Biomass: A Review

The urgent demand for alternative energy sources has been sparked by the tremendous burden on fossil fuels and the resulting acute energy crisis and climate change issues. Lignocellulosic biomass is a copious renewable and alternative bioresource for the generation of energy fuels and biochemicals in biorefineries. Different pretreatment strategies have been established to overcome biomass recalcitrance and face technological challenges, such as high energy consumption and operational costs and environmental hazards, among many. Biological pretreatment using microbial enzymes is an environmentally benign and low-cost method that holds promising features in the effective pretreatment of lignocellulosic biomass. Due to their versatility and eco-friendliness, cellulases, hemicellulases, and ligninolytic enzymes have been recognized as “green biocatalysts” with a myriad of industrial applications. The current review provides a detailed description of different types of lignocellulolytic enzymes, their mode of action, and their prospective applications in the valorization of lignocellulosic biomass. Solid state fermentation holds great promise in the microbial production of lignocellulolytic enzymes owing to its energy efficient, environment friendly, and higher product yielding features utilizing the lignocellulosic feedstocks. The recent trends in the application of enzyme immobilization strategies for improved enzymatic catalysis have been discussed. The major bottlenecks in the bioprocessing of lignocellulosic biomass using microbial enzymes and future prospects have also been summarized.

Biofunctionalization of Multiplexed Silicon Photonic Biosensors.

Silicon photonic (SiP) sensors offer a promising platform for robust and low-cost decentralized diagnostics due to their high scalability, low limit of detection, and ability to integrate multiple sensors for multiplexed analyte detection. Their CMOS-compatible fabrication enables chip-scale miniaturization, high scalability, and low-cost mass production. Sensitive, specific detection with silicon photonic sensors is afforded through biofunctionalization of the sensor surface; consequently, this functionalization chemistry is inextricably linked to sensor performance. In this review, we first highlight the biofunctionalization needs for SiP biosensors, including sensitivity, specificity, cost, shelf-stability, and replicability and establish a set of performance criteria. We then benchmark biofunctionalization strategies for SiP biosensors against these criteria, organizing the review around three key aspects: bioreceptor selection, immobilization strategies, and patterning techniques. First, we evaluate bioreceptors, including antibodies, aptamers, nucleic acid probes, molecularly imprinted polymers, peptides, glycans, and lectins. We then compare adsorption, bioaffinity, and covalent chemistries for immobilizing bioreceptors on SiP surfaces. Finally, we compare biopatterning techniques for spatially controlling and multiplexing the biofunctionalization of SiP sensors, including microcontact printing, pin- and pipette-based spotting, microfluidic patterning in channels, inkjet printing, and microfluidic probes.

Explore how immobilization strategies affected immunosensor performance by comparing four methods for antibody immobilization on electrode surfaces

Among the common methods used for antibody immobilization on electrode surfaces, which is the best available option for immunosensor fabrication? To answer this question, we first used graphene-chitosan-Au/Pt nanoparticle (G-Chi-Au/PtNP) nanocomposites to modify a gold electrode (GE). Second, avian reovirus monoclonal antibody (ARV/MAb) was immobilized on the GE surface by using four common methods, which included glutaraldehyde (Glu), 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide/N-hydroxysuccinimide (EDC/NHS), direct incubation or cysteamine hydrochloride (CH). Third, the electrodes were incubated with bovine serum albumin, four different avian reovirus (ARV) immunosensors were obtained. Last, the four ARV immunosensors were used to detect ARV. The results showed that the ARV immunosensors immobilized via Glu, EDC/NHS, direct incubation or CH showed detection limits of 100.63 EID50 mL−1, 100.48 EID50 mL−1, 100.37 EID50 mL−1 and 100.46 EID50 mL−1 ARV (S/N = 3) and quantification limits of 101.15 EID50 mL−1, and 101.00 EID50 mL−1, 100.89 EID50 mL−1 and 100.98 EID50 mL−1 ARV (S/N = 10), respectively, while the linear range of the immunosensor immobilized via CH (0–105.82 EID50 mL−1 ARV) was 10 times broader than that of the immunosensor immobilized via direct incubation (0–104.82 EID50 mL−1 ARV) and 100 times broader than those of the immunosensors immobilized via Glu (0–103.82 EID50 mL−1 ARV) or EDC/NHS (0–103.82 EID50 mL−1 ARV). And the four immunosensors showed excellent selectivity, reproducibility and stability.

Sandwich-like heterostructured nanomaterials immobilized laccase for the degradation of phenolic pollutants and boosted enzyme stability

A novel magnetic 2D/2D heterogeneous structure MXene@NiFe-LDH@Fe3O4 was prepared for immobilization of laccase. In this work, two-dimensional MXene nanosheets with abundant surface functional groups were heterogeneously assembled with layered double hydroxide (LDH) by in situ co-precipitation method, and magnetic nanoparticle Fe3O4 with excellent biocompatibility and rapid separation of materials and substrates was introduced subsequently, and then silane coupling agent was coated on the surface of MXene@NiFe-LDH@Fe3O4. The functionalized MXene@NiFe-LDH@Fe3O4 was employed as a carrier to immobilize laccase from Trametes-Versicolor. The enzyme loading of the nanocomposite material is as high as 167.9 mg/g. Compared with free enzymes, the immobilized laccase showed a notable improvement in stability in a wider range of pHs (2.0–8.0), temperatures (25–60 °C), and organic solvent concentration (1–5 M). The reusability study suggested that after 7 cycles of repeated catalysis, the degradation efficiency could reach 55.5% for 2,4-dichlorophenol, 92.1% for bisphenol A and70.9% for pyrocatechol. The results provide a new carrier preparation strategy for the efficient immobilization of laccase.

Molecular and Interactions Modelling of PETase and Its Variant with Different Types of Crosslinker in Enzyme Immobilization


 
 
 
 Plastics are made from non-renewable resources and due to the tremendous production of plastics nowadays, they can lead to high levels of pollution. Biodegradation of plastic by utilizing enzymatic catalytic reaction is an environmentally friendly strategy that produce less or no negative carbon footprint. PETase from Ideonella sakaiensis (IsPETase) is an enzyme that able to degrade polyethylene terephthalate (PET), a building block of plastic. However, free enzyme has several limitations such as unstable in harsh conditions and lack of reusability. One of the strategies to overcome this drawback is through enzyme immobilization that able to improve the enzymatic properties. A suitable crosslinker is very important as it would determine the interactions of the enzymatic particles. Crosslinker should be chosen before performing the enzyme immobilization and this can be accomplished by molecular docking. Thus, the purpose of this research is to determine the suitability of glutaraldehyde, chitosan, dialdehyde starch (DAS) and ethylene glycol as the crosslinker for IsPETase and its variant. Three-dimensional structure of the enzymes was built and docked with different types of crosslinkers. Binding affinity and interactions between the enzymes and the crosslinkers were analyzed and it was found that chitosan has the lowest binding affinity (-7.9 kcal/mol) and the highest number of interactions. This is followed by DAS, ethylene glycol and glutaraldehyde. By using computational analysis, suitable crosslinker for IsPETase could be determine and this would a cost-effective practice in enzyme immobilization strategy. 
 
 
 

Recent advancement in sensitive detection of carcinoembryonic antigen using nanomaterials based immunosensors

Carcinoembryonic antigen (CEA) is a prominent cancer biomarker that allows for early diagnosis of various cancers. Present immunoassays techniques help quantify such target molecules in test samples via anti-antibody reaction. Despite their rapid usage, conventional immunoassay techniques demonstrate several limitations that can be easily overcome by employing nanomaterials in sensing assays. Thus, nanomaterial-based immunosensors have gained steady attention from the scientific community owing to their high specificity and low detection limit. Various nanomaterials like platinum, gold, silver and carbon exhibit exceptional properties have allowed promising results in the detection and diagnostics of CEA. Thus, the present review aims to explore the significance and the recent developments of nanomaterial-based biosensors for detecting CEA biomarkers with high sensitivity, selectivity, and specificity. After a brief introduction, we discussed the fundamentals of immunosensors immobilization strategies and common nanomaterials. In the next section, we highlighted the recent advances in the common immunosensors detection approaches for CEA alone and simultaneous detection of CEA with other biomarkers detection. Finally, we concluded the review by discussing the future perspectives of this promising field of biomarkers detection.

Controlling anammox speciation and biofilm attachment strategy using N-biotransformation intermediates and organic carbon levels

Conventional nitrogen removal in wastewater treatment requires a high oxygen and energy input. Anaerobic ammonium oxidation (anammox), the single-step conversion of ammonium and nitrite to nitrogen gas, is a more energy and cost effective alternative applied extensively to sidestream wastewater treatment. It would also be a mainstream treatment option if species diversity and physiology were better understood. Anammox bacteria were enriched up to 80%, 90% and 50% relative abundance, from a single inoculum, under standard enrichment conditions with either stepwise-nitrite and ammonia concentration increases (R1), nitric oxide supplementation (R2), or complex organic carbon from mainstream wastewater (R3), respectively. Candidatus Brocadia caroliniensis predominated in all reactors, but a shift towards Ca. Brocadia sinica occurred at ammonium and nitrite concentrations > 270 mg NH4–N L−1 and 340 mg NO2–N L−1 respectively. With NO present, heterotrophic growth was inhibited, and Ca. Jettenia coexisted with Ca. B. caroliniensis before diminishing as nitrite increased to 160 mg NO2–N L−1. Organic carbon supplementation led to the emergence of heterotrophic communities that coevolved with Ca. B. caroliniensis. Ca. B. caroliniensis and Ca. Jettenia preferentially formed biofilms on surfaces, whereas Ca. Brocadia sinica formed granules in suspension. Our results indicate that multiple anammox bacteria species co-exist and occupy sub-niches in anammox reactors, and that the dominant population can be reversibly shifted by, for example, changing nitrogen load (i.e. high nitrite concentration favors Ca. Brocadia caroliniensis). Speciation has implications for wastewater process design, where the optimum cell immobilization strategy (i.e. carriers vs granules) depends on which species dominates.

Tailor-made novel electrospun polycaprolactone/polyethyleneimine fiber membranes for laccase immobilization: An all-in-one material to biodegrade textile dyes and phenolic compounds

In spite of many works on the biodegradation of textile dyes and phenolic compounds, we propose a new, inexpensive, environmentally friendly, and sustainable material based on electrospun fiber and immobilized laccase. The polycaprolactone (PCL)/polyethyleneimine (PEI) electrospun fibers were optimized and prepared by electrospinning technique according to the operational parameters like PCL concentration (12 wt%), PEI concentration (10 wt%), voltage (16 kV), needle tip-collector distance (20 cm), and injection speed (0.7 mL/h). Next, characterization studies were performed to investigate the morphology and structure of the electrospun fibers without and with laccase. The crude laccase was obtained by cultivating the white rot fungus T. trogii (TT), and T. versicolor (TV). The resulting electrospun fibers showed a smooth surface with a mean diameter of around 560 nm, and larger diameters were observed after laccase immobilization. According to the results, immobilization increased the stability properties of laccase such as storage, and operational. For instance, the residual activity of the PCL/PEI/TTL and PCL/PEI/TVL after 10 repeated cycles, was 33.2 ± 0.2% and 26.0 ± 0.9%, respectively. After 3 weeks of storage, they retained around 30% of their original activity. Moreover, the PCL/PEI/TTL and PCL/PEI/TVL were found to possess high decolorization yield to remove Orange II and Malachite Green textile dyes from solutions imitating polluted waters. Among them, the PCL/PEI/TTL exhibited the highest decolorization efficiencies of Orange II and Malachite Green after 8 continuous uses at pH 5 and a temperature of 50 °C, reaching over 86%, and 46%, respectively. Moreover, PCL/PEI/TTL and PCL/PEI/TVL effectively degraded the 2,6-dichlorophenol phenolic compound at an optimal pH and temperature range and exhibited maximum removal efficiency of 52.6 ± 0.1% and 64.5 ± 7.6%, respectively. Our approach combines the advantageous properties of electrospun fiber material and immobilization strategy for the efficient use of industrial scale important enzymes such as laccase in various enzymatic applications.

Establishment of a salt-induced bioremediation platform from marine Vibrio natriegens

Industrial wastewater discharge, agricultural production, marine shipping, oil extraction, and other activities have caused serious marine pollution, including microplastics, petroleum and its products, heavy metals, pesticides, and other organics. Efficiency of bioremediation of marine pollutions may be limited by high salt concentrations (>1%, w/v), which can cause an apparent loss of microbial activities. In this study, functional promoters P1, P2-1, and P2-2 censoring salt stress were isolated and identified from a Vibrio natriegens strain Vmax. Three salt-induced degradation models were constructed to degrade polyethylene terephthalate (PET), chlorpyrifos (CP), and hexabromocyclododecanes (HBCDs) using the marine strain Vmax. The engineered strains are efficient for degradation of the corresponding substrates, with the degradation rates at 15 mg/L PET in 8 d, 50 mg/L CP in 24 h, and 1 mg/L HBCDs in 4 h, respectively. In addition, an immobilization strategy for recycling and reusing of engineered strains was realized by expressing the chitin-binding protein GbpA. This study may help answer the usage of rapidly growing marine bacteria such as V. natriegens Vmax to degrade marine pollution efficiently.

Fabrication of hollow mesoporous silica-based nanoreactors for enzyme immobilization: high loading capacity, effective protection, and recyclability

The poor stability and low reusability of enzymes have always been the hindrances to their large-scale applications. Herein, hollow mesoporous silica (HMS) nanoparticles have been constructed as nanoreactors for in situ enzyme immobilization, hemoglobin (Hb) was selected as a model enzyme. By utilizing zeolitic imidazolate framework-8 (ZIF-8) as the sacrificial template, the synthesis mechanism of Hb@ZIF-8 has been explored by adjusting the molar ratios of Zn2+ and 2-methylimidazole. When the amount of Hb was constant, the shape of Hb@ZIF-8 gradually changed from flake to granular (from 50:200 mM to 50:800 mM). Furthermore, when the molar ratio of Zn2+ and 2-methylimidazole was fixed, with the amount of Hb increasing, the size of Hb@ZIF-8 decreased gradually, with maximum loading capacity of 460 μg/mg. Subsequently, Hb@ZIF-8 was coated with silica shells and followed by the removal of ZIF-8 in phosphate-buffered saline (pH 5), resulting in Hb@HMS. Compared to free Hb, Hb in HMS nanoreactors maintained over 74% of original catalytic activity under extreme conditions, showing significant improvements on the stability. Further, Hb@HMS still retains 80% of enzymatic activity after 5 cycles, exhibiting its excellent reusability. This work provides an efficient strategy for enzyme immobilization, giving new horizons for biosensing, biocatalysis and biomedicine.

Magnetic Polyethyleneimine Nanoparticles Fabricated via Ionic Liquid as Bridging Agents for Laccase Immobilization and Its Application in Phenolic Pollutants Removal

In this study, polyethyleneimine was combined with magnetic Fe3O4 nanoparticles through the bridging of carboxyl-functionalized ionic liquid, and laccase was loaded onto the carrier by Cu2+ chelation to achieve laccase immobilization (MCIL-PEI-Cu-lac). The carrier was characterized by Fourier transform infrared spectroscopy, scanning electron microscope, thermogravimetric analysis, X-ray diffraction analysis, magnetic hysteresis loop and so on. MCIL-PEI-Cu-lac has good immobilization ability; its loading and activity retention could reach 52.19 mg/g and 91.65%, respectively. Compared with free laccase, its thermal stability and storage stability have been significantly improved, as well. After 6 h of storage at 60 °C, 51.45% of the laccase activity could still be retained, and 81.13% of the laccase activity remained after 1 month of storage at 3 °C. In the pollutants removal test, the removal rate of 2,4-dichlorophenol (10 mg/L) by MCIL-PEI-Cu-lac could reach 100% within 10 h, and the removal efficiency could still be maintained 60.21% after repeated use for 8 times. In addition, MCIL-PEI-Cu-lac also has a good removal effect on other phenolic pollutants (such as bisphenol A, phenol, 4-chlorophenol, etc.). Research results indicated that an efficient strategy for laccase immobilization to biodegrade phenolic pollutants was developed.