Novel polydopamine imprinting layers coated magnetic carbon nanotubes for specific separation of lysozyme from egg white

Fundamentals, Synthetic Strategies and Applications of Non-Covalently Imprinted Polymers

Molecular imprinting has emerged as an important and practical technology to create economical and stable synthetic mimics of antibodies and enzymes. It has already found a variety of important applications, such as affinity separation, chemical/biological sensing, disease diagnostics, proteomics, bioimaging, controlled drug release, and catalysis. In the past decade, significant breakthroughs have been made in non-covalently imprinted polymers, from their synthesis through to their applications. In terms of synthesis, quite a few versatile and facile imprinting approaches for preparing MIPs have been invented, which have effectively solved some key issues in molecular imprinting. Additionally, important applications in several areas, such as sensors, proteomics and bioimaging, have been well demonstrated. In this review, we critically and comprehensively survey key recent advances made in the preparation of non-covalently imprinted polymers and their important applications. We focus on the state-of-art of this technology from three different perspectives: fundamentals, synthetic strategies, and applications. We first provide a fundamental basis for molecular imprinting technologies that have been developed, which is extremely helpful for establishing a sound understanding of the challenges in molecular imprinting. Then, we discuss in particular the major breakthroughs within the last ten years (2014-2024), with emphasis on new imprinting approaches, what strengths the breakthroughs can provide, and which new applications the properties of the prepared non-covalently imprinted polymers are fit for.

Ovotransferrin, an alternative and potential protein for diverse food and nutritional applications

Ovotransferrin(OVT)is a protein found in many types of egg white and has a wide range of functional properties. It has 50% homology with human/bovine lactoferrin, and is expected to be one of the most important alternative proteins for use in food and nutritional applications. This paper mainly reviews the structural characteristics and chemical properties of OVT, as well as its extraction and purification methods. It also systematically describes the various biological activities of OVT and its applications in food and medical industries. The challenges and limitations in the research of OVT were suggested. This review recommends some possible methods such as nanoparticle carriers and microencapsulation to improve the bioavailability and stability of OVT. In addition, this review highlights several strategies to overcome the limitations of OVT in terms of preparation and purification. This review systematically summarizes the recent advances in OVT and will provide guidance for the its development for food and nutritional applications.

The Impact of Processing and Extraction Methods on the Allergenicity of Targeted Protein Quantification as Well as Bioactive Peptides Derived from Egg

This review article discusses advanced extraction methods to enhance the functionality of egg-derived peptides while reducing their allergenicity. While eggs are considered a nutrient-dense food, some proteins can cause allergic reactions in susceptible individuals. Therefore, various methods have been developed to reduce the allergenicity of egg-derived proteins, such as enzymatic hydrolysis, heat treatment, and glycosylation. In addition to reducing allergenicity, advanced extraction methods can enhance the functionality of egg-derived peptides. Techniques such as membrane separation, chromatography, and electrodialysis can isolate and purify specific egg-derived peptides with desired functional properties, improving their bioactivity. Further, enzymatic hydrolysis can also break down polypeptide sequences and produce bioactive peptides with various health benefits. While liquid chromatography is the most commonly used method to obtain individual proteins for developing novel food products, several challenges are associated with optimizing extraction conditions to maximize functionality and allergenicity reduction. The article also highlights the challenges and future perspectives, including optimizing extraction conditions to maximize functionality and allergenicity reduction. The review concludes by highlighting the potential for future research in this area to improve the safety and efficacy of egg-derived peptides more broadly.

Aptamer-functionalized pH-responsive polymer-modified magnetic nanoparticles for specific enrichment and sensitive determination of lactoferrin

A new type of aptamer-functionalized pH-responsive polymer-modified magnetic nanoparticles (ApMNPs) is introduced for specific enrichment and sensitive determination of lactoferrin (Lf) in complex matrixes. In the construction, Fe₃O₄@3-(Triethoxysilyl)propylmethacrylate@poly(4-Vinyl-1, 3-dioxolan-2-one-acrylic acid) (Fe₃O₄@MPS@p(VEC-AA)) were synthesized as pH-responsive polymer-modified magnetic nanoparticles (pMNPs) through free radical polymerization to increase the tunable interaction. Lf-binding aptamers were conjugated onto pMNPs through the reaction of amino-group in aptamer and epoxide-group in VEC, innovatively applied to prepare Lf-ApMNPs. On the basis of the synergistic effect of specific affinity of aptamer on Lf and tunable hydrophobic/hydrophilic property of pH-responsive polymer, Lf-ApMNPs presented good selectivity toward Lf, excellent adsorption capacity (as high as 233.9 mg g^-1), as well as good recoveries in the range 93.6-99.6% in Lf-related nutrition samples. Significantly, the introduction of pH-responsive monomer (AA) effectively regulated the adsorption-desorption process of Lf, with the function similar to a switch. Moreover, the good performances of Ct-ApMNPs toward α-Chymotrypsin showed that ApMNPs exhibited universality to other proteins through easily changing the binding aptamer, thereby offering a facile and efficient approach for specific enrichment and sensitive determination of targets in real biological samples.

Functional Properties and Extraction Techniques of Chicken Egg White Proteins

Chicken egg whites contain hundreds of proteins, and are widely used in the food, biological and pharmaceutical industries. It is highly significant to study the separation and purification of egg white proteins. This review first describes the structures and functional properties of several major active proteins in egg whites, including ovalbumin, ovotransferrin, ovomucoid, lysozyme, ovomucin, ovomacroglobulin and avidin. Then, the common techniques (including precipitation, chromatography and membrane separation) and some novel approaches (including electrophoresis, membrane chromatography, aqueous two-phase system and molecular imprinting technology) for the separation and purification of egg white proteins broadly reported in the current research are introduced. In addition, several co-purification methods for simultaneous separation of multiple proteins from egg whites have been developed to improve raw material utilization and reduce costs. In this paper, the reported techniques in the last decade for the separation and purification of chicken egg white proteins are reviewed, discussed and prospected, aiming to provide a reference for further research on egg proteins in the future.

Recent advances in magnetic carbon nanotubes: synthesis, challenges and highlighted applications

Magnetic carbon nanotubes (MCNTs), consisting of carbon nanotubes (CNTs) and magnetic nanoparticles (MNPs), have enormous exploration and application potentials due to their superior physical and chemical properties, such as unique magnetism and high enrichment performance. This review concentrates on the rapid advances in the synthesis and application of magnetic carbon nanotubes. Great progress has been made in the preparation of MCNTs by developing methods including chemical vapor deposition, pyrolysis procedure, sol-gel process, template-based synthesis, filling process and hydrothermal/solvothermal method. Various applications of MCNTs as a mediator of the adsorbent in magnetic solid-phase extraction, sensors, antibacterial agents, and imaging system contrast agents, and in drug delivery and catalysis are discussed. In order to overcome the drawbacks of MCNTs, such as sidewall damage, lack of convincing quantitative characterization methods, toxicity and environmental impact, and deficiency of extraction performance, researchers proposed some solutions in recent years. We systematically review the latest advances in MCNTs and discuss the direction of future development.

Highly efficient porous magnetic polydopamine/copper phosphate with three-dimensional hierarchical nanoflower morphology as a selective platform for recombinant proteins separation

The separation and purification of recombinant pharmaceutical proteins is a fundamental and challenging step in the biotechnology industry. Hierarchical nanostructures with unique features and high stability can be used as efficient adsorbents. In this study, hierarchical magnetic polydopamine-copper phosphate nanoflowers (Cu-PDA MNFs) were synthesized as high-performance magnetic adsorbents in a simple and low-cost method based on green chemistry. The prepared hybrid Cu-PDA MNFs revealed great performance for separating pure recombinant human growth hormone (rhGH) and the rhGH acquired from recombinant Pichia pastoris yeast fermentation. The analysis confirmed that Cu-PDA MNFs exhibited a high adsorption capacity of 257.4 mg rhGH g^-1 Cu-PDA MNFs and a fast adsorption rate for approaching the adsorption equilibrium within less than 30 min with a recovery efficiency of 74% of rhGH from the real sample. In addition, recycling tests demonstrated the stability and recyclability of Cu-PDA MNFs for at least six cycles with almost constant adsorption capacity and no toxicity. Based on these results, Cu-PDA MNFs could be considered as a promising candidate for separation and purification of rhGH. This work presents a new approach to using organic-inorganic nanoflowers as the hierarchical nanostructure for purification of pharmaceutical proteins with high performance.

Magnetic solid-phase extraction using polydopamine-coated magnetic multiwalled carbon nanotube composites coupled with high performance liquid chromatography for the determination of chlorophenols

Polydopamine (PDA)-coated magnetic multiwalled carbon nanotube (M-MWCNT) composites were synthesized in two facile preparation steps, and were used as adsorbents for magnetic solid-phase extraction (MSPE) coupled with high-performance liquid chromatography (HPLC) for simultaneous extraction, enrichment and determination of five kinds of typical chlorophenols (CPs) in water samples. The as-prepared magnetic composites showed excellent magnetic properties and high thermal stability. Various main parameters influencing the extraction efficiency of MSPE were systematically investigated. Under the optimized MSPE-HPLC conditions, a high enrichment factor (EF) was obtained in the range of 85-112 for 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), 2,6-dichlorophenol (2,6-DCP), 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP). Good linearity was obtained in the range of 2.0-200 μg L^-1 for 2-CP and 4-CP and 1.0-200 μg L^-1 for 2,6-DCP, 2,4-DCP and 2,4,6-TCP, with a correlation coefficient (R²) higher than 0.9964. The limits of detection (LODs) and the limits of quantification (LOQs) were in the range of 0.10-0.31 μg L^-1 and 0.35-1.03 μg L^-1, respectively. The intraday and interday precisions evaluated using relative standard deviation (RSD) values were in the range of 1.05-2.25% and 1.88-2.83%, respectively. The validated MSPE-HPLC method was also successfully applied to analyze five kinds of CPs in tap water, lake water, river water and seawater samples, and satisfactory recoveries were obtained in the range of 76.87-106.5% with RSDs of 1.64-6.78%.

Use of magnetic Fe3O4 nanoparticles coated with bovine serum albumin for the separation of lysozyme from chicken egg white

Fe₃O₄ magnetic nanoparticles modified with tetraethyl orthosilicate and bovine serum albumin (Fe₃O₄@TEOS@BSA) were synthesized and efficiently used to separate lysozyme from egg white. Glutaraldehyde was used to crosslink the bovine serum albumine molecules around the nanoparticles. The surface modifications were attested by transmission electron microscopy, infrared spectroscopy, thermogravimetry analysis, and zeta potential. The material was thermally stable, and its surface charge was pH-dependent. The best lysozyme adsorption and desorption were obtained at pHs 10.0 and 5.0, respectively. The pseudo-second-order model fitted well into the lysozyme adsorption kinetic data and the time for the equilibrium was 15 min. The adsorption equilibrium results were best described by the Freundlich model. Fe₃O₄@TEOS@BSA particles were very efficient to extract lysozyme from chicken egg, according to the SDS-PAGE analyses. The extracted molecules maintained their enzymatic activity in about 90%. Fe₃O₄@TEOS@BSA particles were easily recycled, with their reuse being possible 5 times with the same performance.

Facile covalent preparation of carbon nanotubes / amine-functionalized Fe3O4 nanocomposites for selective extraction of estradiol in pharmaceutical industry wastewater

As a typical steroid hormone drug, estradiol (E2) is also one of the most frequently detected endocrine disrupting chemicals (EDCs) in the aquatic environment. Herein, in response to the potential risk of E2 in steroid hormone pharmaceutical industry wastewater to human and wildlife, a novel carbon nanotubes / amine-functionalized Fe₃O₄ (CNTs/MNPs@NH₂) nanocomposites with magnetic responsive have been developed for the enrichment and extraction of E2 in pharmaceutical industry wastewater, where amino-functionalized Fe₃O₄ magnetic nanoparticles (MNPs@NH₂) were used as a magnetic source. The resultant CNTs/MNPs@NH₂ possessed both the features of CNTs and desired magnetic property, enabling to rapidly recognize and separate E2 from pharmaceutical industry wastewater. Meanwhile, the CNTs/MNPs@NH₂ had good binding behavior toward E2 with fast binding kinetics and high adsorption capacity, as well as exhibited satisfactory selectivity to steroidal estrogen compounds. Furthermore, the change of pH value of aqueous phase in adsorption solvent hardly affected the adsorption of E2 by CNTs/MNPs@NH₂, and the adsorption capacity of E2 ranged from 19.9 to 17.2 mg g^-1 in the pH range of 3.0 to 11.0, which is a latent advantage of the follow-up development method to detect E2 in pharmaceutical industry wastewater. As a result, the CNTs/MNPs@NH₂ serving as a solid phase extraction medium were successfully applied to efficiently extract E2 from pharmaceutical industry wastewater. Therefore, the CNTs/MNPs@NH₂ nanocomposites could be used as a potential adsorbent for removing steroidal estrogens from water. More importantly, the developed method would provide a promising solution for the monitoring and analysis of EDCs in pharmaceutical industry wastewater.

Preparation of polydopamine-coated, graphene oxide/Fe3 O4 - imprinted nanoparticles for selective removal of sulfonylurea herbicides in cereals

BACKGROUND

Sulfonylureas are potentially toxic broad-spectrum herbicides. They pose a persistent threat to food safety and the environment. It is therefore important to develop a rapid and efficient pretreatment and detection method to prevent their harmful effects on human health.

RESULTS

In the present work, a novel and highly selective absorbent for chlorosulfuron (CS) detection was prepared by the simple self-polymerization of dopamine on the surface of magnetic graphene oxide using a CS template. The resultant imprinted nanoparticles (MGO@PDA-MIPs) were characterized by transmission electron microscopy, X-ray diffraction, vibrating-sample magnetometry, thermogravimetric analysis, and nitrogen adsorption-desorption. The adsorption experiments demonstrated that the MGO@PDA-MIPs have excellent selectivity with regard to CS, with a high imprinting factor of 3.41 compared with a non-imprinted polymer. The nanoparticles rapidly achieve adsorption equilibrium and efficient desorption because there are numerous binding sites on the thin polydopamine imprinting layer. Under optimized conditions, the MGO@PDA-MIPs can be used to detect sulfonylurea residues in cereal samples by magnetic solid phase extraction coupled with high performance liquid chromatography (HPLC). The nanoparticles have a satisfactory recovery rate (80.65-101.01%) with a relative standard deviation (RSD) of less than 7.15%, and a limit of detection with regard to CS of 1.61 μg kg^-1 (S/N = 3). They can also be re-used at least seven times.

CONCLUSION

The MGO@PDA-MIPs have outstanding recognition performance, and can be prepared by a facile, single-step, and environmentally friendly process. They therefore have excellent potential for the recognition and separation of trace sulfonylurea herbicides in complex matrices. © 2020 Society of Chemical Industry.

Efficient removal of Alizarin Red S from aqueous solution by polyethyleneimine functionalized magnetic carbon nanotubes

Alizarin Red S (ARS) has been extensively used in the dyeing industry. In order to effectively remove the ARS form dyeing wastewater, polyethyleneimine (PEI)-functionalized magnetic carbon nanotubes (PEI@MCNTs) adsorbent was successfully prepared and its adsorption performances were also investigated in detail. The PEI@MCNTs could efficiently remove the ARS from acidic aqueous solution (pH ≤ 6.0) within 40 min under room temperature. Benefiting from a large number of adsorption sites and multiple interactions, PEI@MCNTs possessed high selectivity towards ARS with spontaneous adsorption process. The maximum adsorption capacity of PEI@MCNTs for ARS was 196.08 mg g^-1 obtained from Langmuir isotherm, higher than that of available conventional adsorbents. Moreover, the PEI@MCNTs could be easily collected by an external magnet, and then effectively regenerated through 10 mM NaOH solution. The prepared PEI@MCNTs could be considered as the promising adsorbent for the removal of anthraquinone dyes in large-scale wastewater treatment.

Surface modification of chitosan film via polydopamine coating to promote biomineralization in bone tissue engineering

Chitosan-based material has been widely used as bone substitute due to its good biocompatibility and biodegradability. However, the hydrophobic surface of chitosan film constrains the osteogenesis mineralization in the process of bone regeneration. For this reason, we develop a novel polydopamine-modified chitosan film suitable for bone tissue engineering applications by a simple and feasible route in this study. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy confirm the process of surface modification. For comparison, surface wettability, the capacity of mineralization in vitro, and biocompatibility of the chitosan film and the polydopamine-modified chitosan film were assessed. Research results indicate that the polydopamine-modified chitosan film has good hydrophilicity. It is very evident that the polydopamine treatment significantly influences the biomineralization capacity of the chitosan-based substrates, which enhance the growth rate of apatite on the modified chitosan film. Besides, MC3T3-E1 osteoblast experiments demonstrate that the cells can adhere and grow well on the polydopamine-modified chitosan film. It is anticipated that this polydopamine-modified chitosan film, which can be prepared in large quantities simply, should have potential applications in bone tissue engineering.

Ultrasensitive magnetic field-assisted surface plasmon resonance immunoassay for human cardiac troponin I

An ultrasensitive surface plasmon resonance (SPR) immunoassay was developed for the specific detection of human cardiac troponin I (cTnI), a principle diagnostic marker for myocardial damage. The thin gold film evaporated on a glass slate, which was employed as the SPR sensing film, was modified by hollow gold nanoparticles (HGNPs) and polydopamine (PDA) sequentially, and then was immobilized with antibodies for specific recognition of target analyte. Electronic coupling of the surface plasmon waves originating from the HGNPs and the gold film leads to the remarkable amplification of SPR response. The PDA film modified on the gold film via self-polymerization of dopamine (DA) facilitates the direct immobilization of capture antibodies (cAb). To separate and enrich the target analyte, PDA-wrapped magnetic multi-walled carbon nanotubes (MMWCNTs-PDA) were conjugated with detection antibodies (dAb) and used as the extracting agent for the magnetic extraction of cTnI in sample. Large surface area of MMWCNTs-PDA ensures its loading capacity for dAb, as well as its extraction efficiency for cTnI. By serving as the "vehicles" for fast delivering the concentrated analyte to the SPR sensing surface, MMWCNTs-PDA-dAb also overcomes the disadvantage of slow diffusion-limited mass transfer and matrix interference effect in regular patterns. The combination of the above improvements results in the significant sensitivity enhancement of the SPR immunoassay. The concentration of cTnI with minimum detectable SPR response obtained by the present assay is 1.25ngmL^-1, which is 1000-fold lower than that obtained by the traditional SPR immunoassay based on PDA-modified gold film.

Recovery of a bacteriocin-like inhibitory substance from Pediococcus acidilactici Kp10 using surfactant precipitation

Bacteriocin is an important peptide which can be used as an anti-microbial agent in food. However, simpler and more cost-effective purification methods need to be developed compared to chromatography to enhance its commercial viability. Surfactant precipitation was employed for the first time to purify bacteriocin-like inhibitory substance (BLIS) from a fermentation broth of Pediococcus acidilactici Kp10, and the amount precipitated was investigated as a function of anionic surfactant (AOT) concentration, and pH. Protein recovery from the precipitate was accomplished using solvent extraction, and solvent type, NaCl concentration, and ionic strength of the final solution were optimised. Optimal conditions were; 1.05mM of AOT at pH 4 for precipitation, and acetone extraction (with 1mM NaCl), which resulted in an 86.3% yield, and 53.8 purification factor. This study highlighted the fact that surfactant precipitation can be used as a primary recovery method for BLIS from a complex fermentation broth.

Polydopamine-Encapsulated Fe3O4 with an Adsorbed HSP70 Inhibitor for Improved Photothermal Inactivation of Bacteria

Photothermal treatment, a new approach for inactivation of bacteria and pathogens that does not depend on traditional therapeutic approaches, has recently received much attention. In this study, a new type of nanoplatform (PDA@Fe3O4 + PES) was fabricated by using polydopamine (PDA, a photothermal conversion agent) to encapsulate Fe3O4 (a magnetic nanoparticle) and support 2-phenylethynesulfonamide (PES, an inhibitor of heat shock protein 70 (HSP70)). Upon near-infrared light irradiation, the increased temperature weakens π-π and hydrogen bonding interactions, and PES is released from the PDA@Fe3O4 + PES. The released PES inhibits the function of HSP70, reducing bacterial tolerance to photothermal therapy and improving the therapeutic effect against infectious bacterial pathogens. After treatment, PDA@Fe3O4 + PES can be recovered using the magnetic property of the Fe3O4 cores. Consequently, PDA@Fe3O4 + PES possesses the potential to be a recyclable photothermal agent for enhanced photothermal bacterial inactivation without causing secondary pollution.

Removal of bisphenol A from aqueous medium using molecularly surface imprinted microbeads

The aim of this study is to prepare bisphenol A (BPA) imprinted polymers, which can be used for the selective removal of BPA from aqueous medium. The BPA-imprinted (MIP) and non-imprinted (NIP) microbeads were synthesized, and characterized by Zeta-sizer, FTIR, SEM and BET method. Bisphenol A was determined in solutions using liquid chromatography-mass spectroscopy (LC-MS). The effect of initial concentration of BPA, the adsorption rate and the pH of the medium on the capacity of BPA-imprinting polymer were studied. Adsorption capacity of BPA was affected by the amount of the incorporated functional monomer in the polymer network. BPA adsorption capacity of MIP-3 and NIP microbeads from aqueous medium was estimated as 76.7 and 59.9 mg g(-1), respectively. The binding efficiencies of BPA-MIP-3 microbeads for different phenolic compounds (i.e., BPA with p-toluidine, 4-aminophenol or 2-naphthol) were explored at binary solutions, and the binding capacities of BPA-imprinted microbeads were found to be 2.79 × 10(-1), 2.39 × 10(-1), 7.59 × 10(-2) and 5.48 × 10(-2) mmol g(-1) microbeads, respectively. The satisfactory results demonstrated that the obtained BPA-MIP microbeads showed an appreciable binding specificity toward BPA than similar structural compounds in the aqueous medium. Moreover, the reusability of BPA-MIP-3 microbeads was tested for several times and no significant loss in adsorption capacity was observed. Finally, the binary and multi-component systems results show that MIP-3 microbeads have special recognition selectivity and excellent binding affinity for template molecule "BPA".

Molecularly Imprinted Electropolymer for a Hexameric Heme Protein with Direct Electron Transfer and Peroxide Electrocatalysis

For the first time a molecularly imprinted polymer (MIP) with direct electron transfer (DET) and bioelectrocatalytic activity of the target protein is presented. Thin films of MIPs for the recognition of a hexameric tyrosine-coordinated heme protein (HTHP) have been prepared by electropolymerization of scopoletin after oriented assembly of HTHP on a self-assembled monolayer (SAM) of mercaptoundecanoic acid (MUA) on gold electrodes. Cavities which should resemble the shape and size of HTHP were formed by template removal. Rebinding of the target protein sums up the recognition by non-covalent interactions between the protein and the MIP with the electrostatic attraction of the protein by the SAM. HTHP bound to the MIP exhibits quasi-reversible DET which is reflected by a pair of well pronounced redox peaks in the cyclic voltammograms (CVs) with a formal potential of -184.4 ± 13.7 mV vs. Ag/AgCl (1 M KCl) at pH 8.0 and it was able to catalyze the cathodic reduction of peroxide. At saturation the MIP films show a 12-fold higher electroactive surface concentration of HTHP than the non-imprinted polymer (NIP).