Aptamer-based sensing of β-casomorphin-7

The potential of aptamers for the analysis of ceramic bound proteins found within pottery

Archaeological pottery are the most numerous objects found during excavations and reflect the culinary practices of the past. However, their functionality for cooking/storing specific foods or drinks cannot be deduced solely from comparing their shapes and sizes. Analysis of protein residues bound to ceramics can reveal the protein/animal type through their amino acid sequence, thus enabling direct identification of food types. Therefore, the aim of our experimental study was to test sixteen aptamers for the analysis of proteinaceous organic residues found within the porous structure of pottery. Traditionally prepared archaeological ceramic replicas were cooked for 5 days in various food/protein suspensions, were UV aged, buried for a year, excavated, and extensively cleaned. Their shards were analysed using immunofluorescence microscopy with aptamers. Results show that eight aptamers (Clone1 and Kirby for egg residuals; seqU5 and BLG14 for milk residuals; HA for blood residuals; Gli4 for gluten residuals; Par1 for fish residuals; and D1 for collagen residuals) produced a successful/specific immunofluorescence microscopy result when they were hybridised to shards containing target protein residuals. Interestingly, on whole egg control samples, when the egg lysozyme-targeting aptamer Kirby was used, fluorescence intensity was 3.1 times greater compared to that observed with anti-ovalbumin antibodies.

DNA Meets Protein─Development, Characterization, and Application of Aptamers against Peanut Allergen

Allergen detection methods support food labeling and quality assessment at the allergen component level of allergen preparations used for allergy diagnosis and immunotherapy (AIT). Commonly applied enzyme-linked immunosorbent assay (ELISA) requires animal antibodies but potentially shows batch variations. We developed synthetic aptamers as alternative binders in allergen detection to meet the replacement, reduction, and refinement (3R) principle on animal protection in science. ssDNA aptamers were specifically selected against the major peanut allergen Ara h 1 and identified by next-generation sequencing. Application in various detection systems (ELISA-like assays, western blot, and surface plasmon resonance) was demonstrated. The ELISA-like assay comprised a sensitivity of 10 ng/mL Ara h 1, comparable to published antibody-based ELISA, and allowed Ara h 1 detection in various peanut flours, similar to those used in peanut AIT as well as in processed food. This ELISA-like aptamer-based assay proofs antibody-free allergen detection for food labeling or quality assessment of diagnostic and therapeutic allergen products.

Recent advances in the bovine β-casein gene mutants on functional characteristics and nutritional health of dairy products: Status, challenges, and prospects

β-casein is the second most abundant form of casein in milk. Changes in amino acid sequence at specific positions in the primary structure of β-casein in milk will produce gene mutations that affect the physicochemical properties of dairy products and the hydrolysis site of digestive enzymes. The screening method of β-casein allele frequency detection in dairy products also has attracted the extensive attention of scientists and farmers. The A1 and A2 β-casein is the two usual mutation types, distinguished by histidine and proline at position 67 in the peptide chain. This paper summarizes the effects of A1 and A2 β-casein on the physicochemical properties of dairy products and evaluates the effects on human health, and the genotyping methods were also concluded. Impressively, this review presents possible future opportunities and challenges for the promising field of A2 β-casein, providing a valuable reference for the development of the functional dairy market.

Detection of A2A2 genotype of beta casein protein (CSN2) gene in local, exotic and cross bred cattle in Pakistan

Genetic variants of bovine Beta-casein protein (CSN2) gene especially A1 and A2 are the most important variants in dairy cattle. A1 milk protein is considered as risk factor for different disease and milk intolerance which release Beta-Casomorphin-7 during digestion which is a bioactive opioid but not released from A2 milk protein. This opioid is responsible for several human health problems like Coronary Heart disease, type 1 diabetics, milk intolerance and other neurological disorders. In present study, 360 blood sample were collected from Lohani, Achai, jersey, Holstein Friesian, Achai x jersey, Friesian x Sahiwal and Sahiwal x Friesian from different region of Khyber Pakhtunkhwa (KP) province. The polymerase chain reaction (PCR) amplicons were sequenced for the identification of polymorphism in exon 7 of Beta-casein protein (CSN2) gene. Sequencing analysis explored CSN2 genotype in exon 7 using the Genomic sequence from GenBank (X.71104) g.8101 C > A at codon 67. The allelic and genotypic frequencies of CSN2 gene were analyzed and observed that Holstein Friesian cattle exhibited A1A2 33%, A1A1 50% and A2A2 17%, Jersey cattle show 68% A1A1, 18% A1A2 and 14% A2A2, Sahiwal x Friesian 56% A1A1, 26% A1A2 and 18% A2A2, Jersey × Achai 78% A2A2, 15% A1A2 and 7% A1A1, Achai 100% A2A2 Lohani 100% A2A2. This is a preliminary study, conducted with meager resources, therefore, it is very difficult to make conclusion that which particular breed possess harmful alleles and which breed possess useful alleles of beta-casein gene. Therefore, a comprehensive molecular work is needed to be performed with greater number of samples sequencing.

Exploring bioactive peptides as potential therapeutic and biotechnology treasures: A contemporary perspective

In preceding years, bioactive peptides (BAPs) have piqued escalating attention owing to their multitudinous biological features. To date, many potential BAPs exhibiting anti-cancer activities have been documented; yet, obstacles such as their safety profiles and consumer acceptance continue to exist. Moreover, BAPs have been discovered to facilitate the suppression of Coronavirus Disease 2019 (CoVID-19) and maybe ideal for treating the CoVID-19 infection, as stated by published experimental findings, but their widespread knowledge is scarce. Likewise, there is a cornucopia of BAPs possessing neuroprotective effects that mend neurodegenerative diseases (NDs) by regulating gut microbiota, but they remain a subject of research interest. Additionally, a plethora of researchers have attempted next-generation approaches based on BAPs, but they need scientific attention. The text format of this critical review is organized around an overview of BAPs' versatility and diverse bio functionalities with emphasis on recent developments and novelties. The review is alienated into independent sections, which are related to either BAPs based disease management strategies or next-generation BAPs based approaches. BAPs based anti-cancer, anti-CoVID-19, and neuroprotective strategies have been explored, which may offer insights that could help the researchers and industries to find an alternate regimen against the three aforementioned fatal diseases. To the best of our knowledge, this is the first review that has systematically discussed the next-generation approaches in BAP research. Furthermore, it can be concluded that the BAPs may be optimal for the management of cancer, CoVID-19, and NDs; nevertheless, experimental and preclinical studies are crucial to validate their therapeutic benefits.

β-Casomorphin: A complete health perspective

β-Casomorphin-7 (BCM-7) is a heptapeptide dietary molecule derived from the digestion of the β-casein of dairy and dairy products. In this review, we have covered the extensive details about BCM and its derived peptides out of the gastrointestinal and enzymatic digestion of milk and milk products, its structure and properties, and its immunological aspects related to human health among infants and adults of both genders. We have left judgment about BCM's pros and cons to the reader by describing the details in a cyclopedic perspective. In addition, a section on the possible ways to detect BCMs from their sources using proteomics, genome-based techniques, such as PCR and aptamers, and other analytical techniques equip the reader to get an idea about the details of the diagnostics available and possible applications in future. Overall, this review will provide information to the end-users of milk and milk products to enable them to make their own decisions about BCMs.

Architecting of a biodevice based on a screen-printed carbon electrode modified with the NiONP nanolayer and aptamer in BCM-7 detection

In this study, an ultrasensitive and robust biodevice implemented on a screen-printed carbon electrode (SPCE) surface is introduced. The β-casomorphin-7 (BCM-7) peptide as an early warning sign of autism disorder is distinguished in this system. The SPCE surface was directly electrodeposited with a nanolayer of the nickel oxide nanoparticles (NiONP). In next step, an Apt sequence as a capture of the BCM-7 was strongly attached on this surface. The embedded sensing interface offered some admirable characterizes to detect the BCM-7. The obtained DPV signals were reversely proportional to the concentrations of the BCM-7 through a stable binding reaction in two working linear ranges from 0.5 × 10^-9-1.5 μmol l-. Also, an unrivaled limit of detection (LOD) value of 166.6 aM was achieved that is so superior by other reported methods in the BCM-7 sensing. This hand-held biodevice was satisfactorily tested for the BCM-7 detection in human urine and blood sample with an average recovery rate of ∼101.87 %. More importantly, this strategy is free from labeling steps, complex sample processing and interference from common biomolecules in blood or urine. Due to the inherent advantages of the SPCE and the NiONP, utilizing this facile sensing interface may be an ideal choice in constructing of the ultrasensitive biodevice with low cost for distinguishing of the autism disorder.

Designing of an ultrasensitive BCM-7 aptasensor based on an SPCE modified with AuNR for promising distinguishing of autism disorder

Abstractly, in this study, an aptasensor is introduced based on a platform consisting of the gold nanorod (AuNR) on a screen printed carbon electrode (SPCE) surface. The aptasensor is applied for detection of the β-casomorphin (BCM-7) as a promising biomarker of autism disorder. The NH₂-Apt sequence is directly immobilized onto the AuNR/SPCE surface by formation of a chemisorption bond between the amine-Au groups. By incubation of the BCM-7 onto the aptasensor surface, the aptasensor directed against BCM-7 and cleverly formed a target/Apt complex to produce a measurable electrical current change. The aptasensor shows linearity over the range of 1 fmol L^-1 to 25 nmol L^-1 with a limit of detection (LOD) of 334 amol L^-1. Furthermore, the function of the aptasensor in real samples such as human urine and plasma samples is evaluated. The achieved satisfactory results are mainly due to three main reasons including (1) the large specific surface area of the AuNR which forms a 3D network on the SPCE surface to capture more Apt sequences at the sensing interface, (2) utilizing Apt as the BCM-7 receptor with inherent unique properties to produce a synergetic effect with the AuNR, and finally, (3) effective using screen printing technology with the fantastic capability to less cost of the aptasensor preparation. There is hope that miniaturization of the proposed aptasensor may aid future efforts to detect autism symptoms as early as infancy under clinical conditions in real-world.

Aptamers: an emerging class of bioaffinity ligands in bioactive peptide applications

The food and health applications of bioactive peptides have grown remarkably in the past few decades. Current elucidations have shown that bioactive peptides have unique structural arrangement of amino acids, conferring distinct functionalities, and molecular affinity characteristics. However, whereas interest in the biological potency of bioactive peptides has grown, cost-effective techniques for monitoring the structural changes in these peptides and how these changes affect the biological properties have not grown at the same rate. Due to the high binding affinity of aptamers for other biomolecules, they have a huge potential for use in tracking the structural, conformational, and compositional changes in bioactive peptides. This review provides an overview of bioactive peptides and their essential structure-activity relationship. The review further highlights on the types and methods of synthesis of aptamers before the discussion of the prospects, merits, and challenges in the use of aptamers for bioaffinity interactions with bioactive peptides.

Expression of active chimeric-tissue plasminogen activator in tobacco hairy roots, identification of a DNA aptamer and purification by aptamer functionalized-MWCNTs chromatography

Tissue-type plasminogen activator (tPA) is a serine protease that plays a crucial role in the fibrinolytic system. We increased the activity of tPA by splicing the active site of dodder-cuscutain gene to human tPA. The chimeric cDNA of tPA was constructed by Splicing by Overlap Extension Polymerase Chain Reaction (SOEing-PCR) method and transferred to the hairy roots of tobacco using different strains of Agrobacterium rhizogenes. Chimeric-tPA was purified by lysine-sepharose chromatography and specific aptamers were designed using SELEX method. Multi wall carbon nanotubes were functionalized with selected aptamers, packed in a column, and used for purification. The results demonstrated that selected aptamer having KD values of 0.320 nM and IC50 of 28.9 nM possessed good affinity to tPA, and the chimeric-tPA was properly purified by aptamer-chromatography. Hairy roots expressing chimeric-tPA and normal-tPA produced 900 and 450 ngmg-1 of total protein, respectively. The activities of chimeric-tPA and normal-tPA were 90 and 60 IUml-1, respectively. Compared to the normal-tPA, chimeric-tPA showed more activity.

Aptamers in HIV research diagnosis and therapy

Aptamers are high affinity single-stranded nucleic acid or protein ligands which exhibit specificity and avidity comparable to, or exceeding that of antibodies and can be generated against most targets. The functionality of aptamers is based on their unique tertiary structure, complexity and their ability to attain unique binding pockets by folding. Aptamers are selected in vitro by a process called Systematic Evolution of Ligands by Exponential enrichment (SELEX). The Kd values for the selected aptamer are often in the picomolar to low nanomolar range. Stable and nontoxic aptamers could be selected for a wide range of ligands including small molecules to large proteins. Aptamers have shown tremendous potential and have found multipurpose application in the field of therapeutic, diagnostic, biosensor and bio-imaging. While their mechanism of action can be similar to that of monoclonal antibodies, aptamers provide additional advantages in terms of production cost, simpler regulatory approval and lower immunogenicity as they are synthesized chemically. Human immunodeficiency virus (HIV) is the primary cause of acquired immune deficiency syndrome (AIDS), which causes significant morbidity and mortality with a significant consequent decrease in the quality of patient's lives. While cART has led to good viral control, people living with HIV now suffer from non-HIV comorbidities due to viral protein expression that cannot be controlled by cART. Hence pathophysiological mechanisms that govern these comorbidities with a focus on therapies that neutralize these HIV effects gained increased attention. Recent advances in HIV/AIDS research have identified several molecular targets and for the development of therapeutic and diagnostic using aptamers against HIV/AIDS. This review presents recent advances in aptamers technology for potential application in HIV diagnostics and therapeutics towards improving the quality of life of people living with HIV.

Structure-informed detection and quantification of peptides in food and biological fluids

Peptides with biological properties, that is, bioactive peptides, are a class of biomolecules whose health-promoting properties are increasingly being exploited in food and health products. However, research on targeted techniques for the detection and quantification of these peptides is still in its infancy. Such information is needed in order to enhance the biological and chemometric characterization of peptides and their subsequent application in the functional food and pharmaceutical industries. In this review, the role of classic techniques such as electrophoretic, chromatographic, and peptide mass spectrometry in the structure-informed detection and quantitation of bioactive peptides are discussed. Prospects for the use of aptamers in the characterization of bioactive peptides are also discussed. PRACTICAL APPLICATIONS: Although bioactive peptides have huge potential applications in the functional foods and health area, there are limited techniques in enhancing throughput detection, quantification, and characterization of these peptides. This review discusses state-of-the-art techniques relevant in complementing bioactive detection and profiling irrespective of the small number of amino acid units. Insights into challenges, possible remedies and prevailing areas requiring thorough research in the extant literature for food chemists and biotechnologists are also presented.

Immobilized aptamer on gold electrode senses trace amount of aflatoxin M1

An electrochemical aptasensor for detection of trace amounts of aflatoxin M1 was developed. This required immobilization of aptamer on screen printed gold electrode comprising of working electrode, counter electrode and reference electrode and was achieved by sequentially layering dithiodipropionic acid, streptavidin and biotinylated-tetraethylene glycol-aptamer. Immobilization of aptamer was monitored by cyclic voltammetry. Peak current in square wave voltammogram was inversely related to logarithmic concentration of aflatoxin M1. Dynamic range of sensor was 1-105 ppt aflatoxin M1. Sensor can be regenerated by treating electrode with 10% sodium dodecyl sulfate or 40 mM tris-HCl (pH 8.0) containing 10 mM ethylenediaminetetraacetic acid and 0.02% tween-20.

Prospects in the use of aptamers for characterizing the structure and stability of bioactive proteins and peptides in food

Food-derived bioactive proteins and peptides have gained acceptance among researchers, food manufacturers and consumers as health-enhancing functional food components that also serve as natural alternatives for disease prevention and/or management. Bioactivity in food proteins and peptides is determined by their conformations and binding characteristics, which in turn depend on their primary and secondary structures. To maintain their bioactivities, the molecular integrity of bioactive peptides must remain intact, and this warrants the study of peptide form and structure, ideally with robust, highly specific and sensitive techniques. Short single-stranded nucleic acids (i.e. aptamers) are known to have high affinity for cognate targets such as proteins and peptides. Aptamers can be produced cost-effectively and chemically derivatized to increase their stability and shelf life. Their improved binding characteristics and minimal modification of the target molecular signature suggests their suitability for real-time detection of conformational changes in both proteins and peptides. This review discusses the developmental progress of systematic evolution of ligands by exponential enrichment (SELEX), an iterative technology for generating cost-effective aptamers with low dissociation constants (K _d) for monitoring the form and structure of bioactive proteins and peptides. The review also presents case studies of this technique in monitoring the structural stability of bioactive peptide formulations to encourage applications in functional foods. The challenges and potential of aptamers in this research field are also discussed. Graphical abstract Advancing bioactive proteins and peptide functionality via aptameric ligands.

Aptamers in Therapeutics

Aptamers are single strand DNA or RNA molecules, selected by an iterative process known as Systematic Evolution of Ligands by Exponential Enrichment (SELEX). Due to various advantages of aptamers such as high temperature stability, animal free, cost effective production and its high affinity and selectivity for its target make them attractive alternatives to monoclonal antibody for use in diagnostic and therapeutic purposes. Aptamer has been generated against vesicular endothelial growth factor 165 involved in age related macular degeneracy. Macugen was the first FDA approved aptamer based drug that was commercialized. Later other aptamers were also developed against blood clotting proteins, cancer proteins, antibody E, agents involved in diabetes nephropathy, autoantibodies involved in autoimmune disorders, etc. Aptamers have also been developed against viruses and could work with other antiviral agents in treating infections.