Lysozyme Aptamer-Functionalized Magnetic Nanoparticles for the Purification of Lysozyme from Chicken Egg White

Screening, identification, and application of aptamers against allergens in food matrices

Food allergies have become one of the most pressing issues in food safety and public health globally along with their incidence increasing in recent years. The reliable recognition of allergens from different sources, especially food-hidden allergens, is essential for preventing and controlling food allergies. Recently, aptamers, as emerging recognition elements, have gained considerable attention in food allergy, especially in the detection of food allergens. This review systematically summarizes the latest progress in screening, identification, and application of aptamers against food allergens over the past five years. We first introduce a brief overview of food allergy and aptamers, followed by a detailed focus on the aptamers' research against different food allergens broadly based on the major categories of the Big-8 allergens: highlighting the newly screened aptamers and their applied systematic evolution of ligands by exponential enrichment (SELEX) strategies, and emphasizing their practical applications including aptasensors, allergy inhibitors, or affinity adsorptions. Finally, the remaining challenges and future exploitations faced by aptamers in food allergens are comprehensively discussed and depicted. This review holds the promise of inspiring a broader range of researchers to gain an in-depth understanding of food allergy assisted by aptamer recognition and to facilitate improved biochemical analyses and successful application.

Self-Assembled Eutectogel with Cell Permeation and Multiple Anti-Inflammatory Abilities for Treating Chronic Periodontitis

Eutectogels represent an attractive option for various industrial applications that use deep eutectic solvents (DESs) as effective liquid active ingredients and offer remarkable stability, cost-effectiveness, and environmental friendliness. However, the biological applications of these compounds are limited. DESs are highly structurally tunable and exhibit remarkable biofunctionality and biocompatibility, conferring substantial benefits in the treatment of diseases. In this study, choline-chloride and mannose are used to fabricate ChCl/M DES, followed by introduction of lysozyme fibers and gallic acid for self-assembly into injectable eutectogels through hydrogen bonding and hydrophilic/hydrophobic interaction interactions. The eutectogels demonstrate almost 100% bactericidal activities against three strains and significant immune-regulation. This is supported by a decrease in the proportion of CD86-expressing cells from 64.02% to 18.17% and an increase in CD206-expressing cells from 2.53% to 29.96% through flow cytometry experiments. The eutectogels effectively inhibit alveolar bone loss and alleviated local inflammation in a rat model of chronic periodontitis owing to the promotion of gallic acid in the cell membrane by the ChCl/M DES. Hence, self-assembled eutectogels exhibit the potential to enhance the efficacy if treatments/therapies against inflammatory diseases by facilitating bacterial control, reactive oxygen species scavenging, and the regulation of macrophages by promoting cell permeation of small-molecule drugs.

Colourimetric and SERS dual-mode aptasensor using Au@Ag and magnetic nanoparticles for the detection of Campylobacter jejuni

A dual-mode aptasensor has been developed for the effective detection of Campylobacter jejuni (C. jejuni), a major cause of gastrointestinal disease worldwide. The aptasensor utilizes nanoparticles, specifically a core-shell structure consisting of gold and silver (Au@Ag NPs), along with magnetic nanoparticles (MNPs). When Campylobacter jejuni is introduced, "Au@Ag NPs-Aptamer-Campylobacter jejuni-Aptamer-MNPs" sandwich complexes are formed due to the high affinity of the aptamer for the bacterial surface membrane proteins. The dual-mode aptasensor can magnetically enrich the sample in just 15 min, and the presence of Campylobacter jejuni is determined by observing a color change. Additionally, the concentration of Campylobacter jejuni can be quantified using surface-enhanced Raman spectroscopy (SERS) and standard curves. This results in a wider linear range (1.8 × 101-108 CFU/mL) under optimal conditions, a lower limit of detection (6 CFU/mL), and a higher selectivity for the detection of bacteria compared to previously reported sensors. Compared with traditional microbial culture counting methods, the dual-mode aptasensor does not require Raman reporters. The physical action of magnetic enrichment, along with the application of Au@Ag NPs, improves the accuracy of the dual-mode aptasensor, offering the advantages of convenience and high sensitivity. Moreover, by utilizing different types of aptamers, this aptasensor can be modified to detect a wider range of harmful pathogens in various environments.

Selection of DNA aptamers for the aptamer-assisted magnetic capture of the purified xylanase from Aspergillus niger

Xylanases are a group of enzymes that catalyze the hydrolysis of xylan. Xylanases have wide industrial applications, and they can produced by various organisms. In this study, we aimed to develop aptamers for the capture of xylanase produced by a wild-type Aspergillus niger strain. Xylanase was produced by Aspergillus niger in a 5-liter stirred-tank bioreactor and then purified by column chromatography. Magnetic bead-based SELEX (Systematic Evolution of Ligands by Exponential Enrichment) was performed to select DNA aptamers specific to the purified xylanase. After nine rounds of selection, next-generation sequencing (NGS) analysis was performed. Four aptamers, namely AXYL-1, AXYL-2, AXYL-3, and AXYL-4, were identified for further characterization. The binding properties of the selected aptamers were characterized by fluorescence quenching (FQ) analysis and an enzyme-linked aptamer assay (ELAA). The Kd values were found to be in the low μM range. Then, each aptamer was immobilized on streptavidin-coated magnetic particles, and the recovery ratio of xylanase was determined. Although AXYL-1 wasn't effective, AXYL-2, AXYL-3, and AXYL-4 were proven to capture the xylanase. The maximum recovery rate of xylanase was found to be approximately 54 %.

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.

Peanut allergen induces more serious allergic reactions than other allergens involving MAPK signaling pathways

There is no universally accepted uniform research to classify the severity of allergic reactions triggered by different food allergens. We established a food allergy model based on repeated intragastric administrations of proteins from peanut, egg, milk, or soybean mixed with cholera toxin followed by oral food challenges with a high dose of the sensitizing proteins. Increased specific IgE, specific IgG1, allergic symptom scores, histamine, murine mast cell proteases-1, vascular leakage, Th2 cytokines, and mast cell infiltration in the lungs and intestine were found in the allergic groups via enzyme-linked immunosorbent assay, hematoxylin-eosin, and toluidine blue staining. Each sensitized group showed a decrease in body temperature and Th1 cytokines after oral food challenge. The increased levels of Th2 cytokines, IL-25, IL-33, and TSLP, and related asthma genes ARG1, DCN, LTB4R1 and NFKBIA as well as the activation of MAPK signaling pathways were also revealed by quantitative real-time PCR and western blotting. In terms of the severity of food allergies, peanut allergy was the most serious followed by egg and milk, and soybean allergy was the least severe. Compared to other allergic groups, asthma genes were regulated through the MAPK signaling pathways to produce related Th2 cytokines in peanut allergy; consequently, mice in the peanut group exhibited more severe allergic reactions. Comparison of the severity of food allergies is required for the development of milder prevention for severe food allergies.

Selective isolation and sensitive detection of lysozyme using aptamer based magnetic adsorbent and a new quartz crystal microbalance system

Magnetic chitosan beads and quartz crystal microbalance chip were decorated with lysozyme specific aptamer for isolation and detection of lysozyme, respectively. The lysozyme specific aptamer was immobilized on poly (dopamine) coated magnetic chitosan beads and the chip via Schiff base reaction. The percentage of the removal efficiency and purity of the isolated lysozyme from egg white were 87.6% and 91.8%, respectively. Further, the sensor system was contacted with different concentrations of lysozyme and other test proteins. This sensor system provided a method for the label-free, concentration-dependent, and selective detection of lysozyme with an observed detection limit of 17.9 ± 0.6 ng/mL. The sensor system was very selective and not significantly responded to the other tested proteins such as ovalbumin, trypsin, cytochrome C, and glucose oxidase. The prepared new sensor system showed a good durability and a high sensitivity for determination of lysozyme from solutions and whole egg white.

Determination of aflatoxin B1 in Pixian Douban based on aptamer magnetic solid-phase extraction

Aflatoxin B1 (AFB₁) is considered as the most prevalent and toxic mycotoxin in food, and is the indispensable index in the monitoring of Pixian Douban, a traditional chinese fermented bean paste from Sichuan. However, the effeciency of AFB₁ detection in Pixian Douban is influenced by the traditional extraction, which is usually complex and time consuming. Therefore, an aptamer-based magnetic solid-phase extraction method was designed for the pretreatment of AFB₁ in this sample, for which Fe₃O₄ was synthesized via the solvothermal method and then a Fe₃O₄@SiO₂–NH₂ with a core–shell structure was prepared, followed by an AFB₁-aptamer attachment. The validation was performed via an enzyme-linked immunosorbent assay and compared with HPLC-MS/MS. The linearity range of this method was 0.5–2.0 ng mL ⁻¹ with R² of 0.981, and recoveries of AFB₁ ranged from 80.19% to 113.92% with RSDs below 7.28% with no significant differences compared to HPLC-MS/MS. The three-time reusability efficiencies of aptamer-MNPs were averaged at 78.24%. The results proved that aptamer-MNPs were high-performance adsorbents for extracting and enriching AFB₁, facilitating quick and effective detection of AFB₁ in Pixian DouBan samples.

An aptamer-based magnetic solid-phase extraction method was designed for the pretreatment of AFB1 from a Pixian Douban sample. It was developed based on aptamer–Fe₃O₄@SiO₂–NH₂ with subsequent ELISA validation, showing an efficient result.

The construction of multifunctional nanoparticles system for dual-modal imaging and arteriosclerosis targeted therapy

Atherosclerosis is a major risk factor for the development of cardiovascular disease. Unfortunately, due to relatively low sensitivities and poor resolution, the results of surgical resection are often largely unsatisfactory. Moreover, many chemotherapeutic agents, such as curcumin (Cur), are restricted by the low blood-brain barrier (BBB) permeability. Recently, nanotechnology proposes new opportunities to overcome these treatment barriers. In this study, superparamagnetic iron oxide nanoparticles (SPIO) was prepared by the high-temperature solid-state method, and then loaded into amphiphilic polymer DSPE-PEG to form SDP nanoparticles by hydrogen bonding in oil phase. The curcumin was encapsulated in SDP nanoparticles by self-assembly. Finally, vascular cell adhesion molecule-1 (VCAM-1) and Cy5.5 were conjugated on into SDP/Cur nanoparticles by amidation reaction. The average particle size of the prepared multifunctional SDP-VCAM-1/Cur/Cy5.5 nanoparticles is 124.4 nm, which can provide the sustained release of Cur. Moreover, the nanoparticles are proved to have superparamagnetic properties and fluorescence properties. In vitro cell experiments show that nanoparticles have excellent biocompatibility, blood compatibility and macrophage targeting. These results show that SDP-VCAM-1/Cur/Cy5.5 nanoparticles can be used not only as dual imaging probe for magnetic resonance (MR) and fluorescence imaging, but also as carriers to deliver chemotherapeutic drugs to inflammatory tissue, thus providing a promising opportunity for the treatment, molecular imaging and targeted therapy in atherosclerosis due to their established specificity and safety.

Adsorption and purification performance of lysozyme from chicken egg white using ion exchange nanofiber membrane modified by ethylene diamine and bromoacetic acid

A high-performance polyacid ion exchange (IEX) nanofiber membrane was used in membrane chromatography for the recovery of lysozyme from chicken egg white (CEW). The polyacid IEX nanofiber membrane (P-BrA) was prepared by the functionalization of polyacrylonitrile (PAN) nanofiber membrane with ethylene diamine (EDA) and bromoacetic acid (BrA). The adsorption performance of P-BrA was evaluated under various operating conditions using Pall filter holder. The results showed that optimal conditions of IEX membrane chromatography for lysozyme adsorption were 10% (w/v) of CEW, pH 9 and 0.1 mL/min. The purification factor and yield of lysozyme were 402 and 91%, respectively. The adsorption process was further scaled up to a larger loading volume, and the purification performance was found to be consistent. Furthermore, the regeneration of IEX nanofiber membrane was achieved under mild conditions. The adsorption process was repeated for five times and the adsorption capacity of adsorber was found to be unaffected.

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.

Strong and weak cation-exchange groups generated cryogels films for adsorption and purification of lysozyme from chicken egg white

Here, the macroporous poly(hydroxylmethyl methacrylate/glycidyl methacrylate [p(HEMA-GMA)] cryogels with large porous surface were prepared, and then the epoxy groups of the p(HEMA-GMA) cryogels were systematically modified into strong and weak cationic groups. The effects of initial protein concentrations, adsorption time, pH, salt concentrations and temperatures on adsorption efficiency of cation exchange cryogels for lysozyme were determined. The maximum lysozyme adsorption capacities of strong and weak cation exchange cryogels were found to be 188.3 and 79.7 mg/g cryogel at 25 °C, respectively. The performance of the strong cationic cryogel was evaluated by purification of lysozyme from egg white. The activity of the isolated lysozyme was found to be 21,347 U/mg. The cationic cryogel maintained its expected high adsorption capacity and efficiency of the purification levels during repeated adsorption desorption processes. Finally, the purpose of this work is the design a cation exchange system for purification of lysozyme from egg-white.

Purification of low-abundance lysozyme in egg white via free-flow electrophoresis with gel-filtration chromatography

As an effective separation tool, free-flow electrophoresis has not been used for purification of low-abundance protein in complex sample matrix. Herein, lysozyme in complex egg white matrix was chosen as the model protein for demonstrating the purification of low-content peptide via an FFE coupled with gel fitration chromatography (GFC). The crude lysozyme in egg while was first separated via free-flow zone electrophoresis (FFZE). After that, the fractions with lysozyme activity were condensed via lyophilization. Thereafter, the condensed fractions were further purified via a GFC of Sephadex G50. In all of the experiments, a special poly(acrylamide- co-acrylic acid) (P(AM-co-AA)) gel electrophoresis and a mass spectrometry were used for identification of lysozyme. The conditions of FFZE were optimized as follows: 130 μL/min sample flow rate, 4.9 mL/min background buffer of 20 mM pH 5.5 Tris-Acetic acid, 350 V, and 14 °C as well as 2 mg/mL protein content of crude sample. It was found that the purified lysozyme had the purity of 80% and high activity as compared with its crude sample with only 1.4% content and undetectable activity. The recoveries in the first and second separative steps were 65% and 82%, respectively, and the total recovery was about 53.3%. The reasons of low recovery might be induced by diffusion of lysozyme out off P(AM-co-AA) gel and co-removing of high-abundance egg ovalbumin. All these results indicated FFE could be used as alternative tool for purification of target solute with low abundance.

FRET-Based Aptasensor for the Selective and Sensitive Detection of Lysozyme

Lysozyme is a conserved antimicrobial enzyme and has been cited for its role in immune modulation. Increase in lysozyme concentration in body fluids is also regarded as an early warning of some diseases such as Alzheimer’s, sarcoidosis, Crohn’s disease, and breast cancer. Therefore, a method for a sensitive and selective detection of lysozyme can benefit many different areas of research. In this regard, several aptamers that are specific to lysozyme have been developed, but there is still a lack of a detection method that is sensitive, specific, and quantitative. In this work, we demonstrated a single-molecule fluorescence resonance energy transfer (smFRET)-based detection of lysozyme using an aptamer sensor (also called aptasensor) in which the binding of lysozyme triggers its conformational switch from a low-FRET to high-FRET state. Using this strategy, we demonstrated that the aptasensor is sensitive down to 2.3 picomoles (30 nM) of lysozyme with a dynamic range extending to ~2 µM and has little to no interference from similar biomolecules. The smFRET approach used here requires a dramatically small amount of aptasensor (~3000-fold less as compared to typical bulk fluorescence methods), and it is cost effective compared to enzymatic and antibody-based approaches. Additionally, the aptasensor can be readily regenerated in situ via a process called toehold mediated strand displacement (TMSD). The FRET-based aptasensing of lysozyme that we developed here could be implemented to detect other protein biomarkers by incorporating protein-specific aptamers without the need for changing fluorophore-labeled DNA strands.