A portable electrochemiluminescence aptasensor for β-lactoglobulin detection

Highly sensitive and catalytic electrochemical aptamer-based biosensor for β-lactoglobulin via coupling redox recycling background minimization with DNAzyme amplification

BACKGROUND

β-lactoglobulin (β-Lg), a major allergen in dairy products, can trigger severe allergic reactions and even fatal outcomes in infants. In this work, we develop a new low background current redox recycling strategy by conjugating the electrochemical mediator to trimetallic hybrid nanoparticles (NPs)-dispersed graphene as the signal tag, which is coupled with DNAzyme amplifications to construct highly catalytic and ultrasensitive β-Lg aptasensor.

RESULTS

Target β-Lg molecules bind aptamers in DNAzyme/aptamer duplexes to release active DNAzymes to initiate cyclic cleavage of hairpin substrates. This subsequently leads to confinement of many probes for signal generation on electrode. Assisted by K3 [Fe(CN)6] in detection buffer, catalytic redox recycling of mediators induced by trimetallic hybrid NPs thus yield considerably magnified currents for detecting β-Lg with detection limit of 5.4 pg/mL. Our results show that attachment of redox mediator to NP-dispersed graphene can effectively and significantly lower the background current compared with its presence in buffer. At the meantime, the coupling of the DNAzyme amplification with catalytic hybrid NPs can enhance the current signal, leading to high signal-to-noise ratio and sensitivity. Such aptasensor also exhibits high selectivity and can achieve detection of low levels of β-Lg in infant rice cereal.

SIGNIFICANCE

The simultaneous background current reduction and dual catalytic signal amplification of our biosensor strategy leads to highly improved signal-to-noise ratio and sensitivity, which suggesting its promising potential for the monitoring of different trace molecular biomarkers for diverse applications.

Aptasensors application for cow's milk allergens detection and early warning: Progress, challenge, and perspective

Cow's milk allergy (CMA) is considered one of the most prevalent food allergies and a public health concern. Modern medical research shows that the effective way to prevent allergic reactions is to prevent allergic patients from consuming allergenic substances. Therefore, the development of rapid and accurate detection technology for milk allergens detection and early warning is critical to safeguarding those with a cow milk allergy. As the oligonucleotide sequences with high specificity and selectivity, aptamers frequently assemble with transduction elements forming multifarious aptasensors for quantitative detection owing to their high-affinity binding to the target. Current aptasensors in the field of cow's milk allergen detection in recent years are explored in this review. This review takes a look back at a few common assays, including ELISA and PCR, before presenting a clear overview of the aptamer and threshold doses. It delves into a detailed discussion of the current aptamer-based detection techniques and related theories for milk allergen identification. Last but not least, we conclude with a discussion and outlook of the advancements made in allergen detection with aptamers. We sincerely hope that there will be more extensive applications for aptasensors in the future contributing to reducing the possibility of patients suffering from adverse reactions.

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.

Aptamer-based sensitive fluorescence β-lactoglobulin food allergen bioassay via dual and cyclic bidirectional strand displacement amplifications

β-Lactoglobulin (β-Lg) is a prevalent allergenic protein found in most dairy products, which poses great food safety risks for individuals with allergies, especially for infants. Sensitive and effective detection methods for such allergens are essential to reduce the risk of allergies in daily life. Herein, a fluorescent aptamer bioassay based on a dual and cyclic bidirectional strand displacement means is developed for the sensitive detection of β-Lg in infant rice porridge and milk. The aptamer in the duplex DNA probe binds β-Lg to release the assistance strand to further hybridize with two hairpins, which triggers the initiation of two cyclic amplification cycles through the polymerization, displacement, and nicking of the strands under the action of DNA polymerase and endonuclease restriction enzymes. The amplification cycles lead to the unfolding of many fluorescently quenched signal probes to exhibit substantially enhanced fluorescence recovery for detecting β-Lg. The assay can realize detection of β-Lg in concentrations as low as 4.41 pM within the range of 0.01 to 10 nM. Furthermore, our sensing method has the capability to discriminate β-Lg from other proteins with high selectivity, resulting in low levels of β-Lg detection in rice porridge and milk samples, demonstrating promising potentials of the developed sensing method for monitoring various food allergens.

Designing tannic acid-polyethyleneimine-modified electrode and novel affinity peptide for β-lactoglobulin detection in milk

Harmful substances that cause food allergies can pose a significant threat to consumers along with food safety. According to the World Health Organization (WHO), approximately 10 % of the global population is currently affected by food allergies. Therefore, there is an urgent need for the development of more accurate and precise biosensors capable of detecting these hazardous substances including beta-lactoglobulin. Although numerous detection and analysis methods have been developed, they still suffer from various limitations. In this study, a tannic acid-polyethyleneimine (TA-PEI) network modified screen-printed electrodes (SPE) are newly developed and the binding sequence of peptide against β-LG was successfully screened using random peptide library. A novel affinity peptide with the desired sequence of S-L-S-P-S-L-W-Q-V-S-M-L-G-G-G-G-E-P-L-Q-L-K-M against β-lactoglobulin (β-LG) is designed and synthesized. The synthesized affinity peptide was immobilized on TA-PEI modified SPE to develop peptide-based sensor against β-LG for the first time. Under successful optimization, the developed sensor exhibited a linear relationship between 50 and 750 ng, with a Kd of 213.9 ng. In addition, the sensor was able to detect β-LG in cow and goat milk, with average recoveries of 88.5 % and 92.2 %, respectively.