Analytical performances of a DNA-ligand system using time-resolved fluorescence for the determination of ochratoxin A in wheat

Rapid and sensitive detection of mycotoxins by advanced and emerging analytical methods: A review

Quantification of mycotoxins in foodstuffs is extremely difficult as a limited amount of toxins are known to be presented in the food samples. Mycotoxins are secondary toxic metabolites, made primarily by fungal species, contaminating feeds and foods. Due to the presence in globally used grains, it is an unpreventable problem that causes various acute and chronic impacts on human and animal health. Over the previous few years, however, progress has been made in mycotoxin analysis studies. Easier techniques of sample cleanup and advanced chromatographic approaches have been developed, primarily high-performance liquid chromatography. Few extremely sophisticated and adaptable tools such as high-resolution mass spectrometry and gas chromatography-tandem MS/MS have become more important. In addition, Immunoassay, Advanced quantitative techniques are now globally accepted for mycotoxin analysis. Thus, this review summarizes these traditional and highly advance methods and their characteristics for evaluating mycotoxins.

Coordination of mycotoxins with lanthanides in luminescent complexes

The ability of several chelating mycotoxins to form coordination complexes with the lanthanide metals europium and terbium was explored. The mycotoxins examined included ochratoxin A, citrinin, cyclopiazonic acid (CPA), kojic acid, and tenuazonic acid (TeA). Of these compounds, TeA and CPA resulted in the greatest luminescence. Parameters influencing luminescence of TeA were investigated further. These included the type of lanthanide and its concentration, certain environmental factors, and the effect of competing metal cations. Of the two lanthanide metals, the terbium coordination complex (TeA-Tb³⁺) showed greater luminescence relative to the europium complex (TeA-Eu³⁺). The effects of solvent type, water content, and pH on the TeA-Tb³⁺ system suggested that optimal conditions for luminescence were in 90% methanol with 10% aqueous buffer at pH 3. In competitive assays, the luminescence of the TeA-Tb³⁺ complex decreased as the concentration of competing metal cations increased. Among the cations tested, Cu²⁺ was the best inhibitor followed by Al³⁺, Au³⁺, Fe³⁺, Co²⁺, Mn²⁺, Mg²⁺, and Ca²⁺. Two cations, Na⁺ and K⁺, showed no significant inhibition. This is the first report to describe the coordination of the metal-chelating mycotoxin TeA with lanthanides and the ability of TeA to serve as an "antenna" for the efficient transfer of energy to the lanthanide with resulting luminescence. Understanding the ability of mycotoxins such as TeA to chelate metals provides insight into how they exert their toxic effects.

Highly hydrophilic polyhedral oligomeric silsesquioxane (POSS)-containing aptamer-modified affinity hybrid monolith for efficient on-column discrimination with low nonspecific adsorption

A highly hydrophilic aptamer-modified POSS-containing hybrid affinity monolith is presented for efficient on-column discrimination with low non-specific adsorption.

A facile AuNPs@aptamer-modified mercaptosiloxane-based hybrid affinity monolith with an unusually high coverage density of aptamer for on-column selective extraction of ochratoxin A

A convenient and high-performance AuNPs@aptamer-modified mercaptosiloxane-based hybrid affinity monolithic column with an unusually high coverage density of aptamers was facilely prepared and used for on-column selective recognition of ochratoxin A (OTA). Due to the high surface-to-volume ratio of AuNPs, the robust conjugation of Au-SH and large specific surface area of hybrid-silica monolith, high coverage density of 5'-SH-aptamers up to 3494 pmol μL-1 was achieved, which was 2.5-10 folds higher than that of other previously reported affinity monoliths modified with AuNPs@Apt. Using OTA as the model analyte, the highly selective recognition of OTA was carried out via online coupling with HPLC, and the cross-reactivity towards analogues, such as OTB and aflatoxin B1, was weak. High recovery yields of OTA were achieved at more than 92% (n = 3) even when OTB was added at a high concentration level up to 50 ng mL-1. For sample analysis, efficient discrimination of OTA was successfully obtained with a sensitive detection limit of 25 pg mL-1. The recoveries of OTA with different fortified levels were achieved at 88.6%-94.1% and 88.2%-94.3% for beer and wine samples, respectively. This protocol provides a facile approach for fabricating a desirable affinity monolith modified with abundant aptamers for highly selective and sensitive on-column extraction of target analyte OTA.

Complexation of the Mycotoxin Cyclopiazonic Acid with Lanthanides Yields Luminescent Products

Cycopiazonic acid (CPA) is a neurotoxin that acts through inhibition of the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA). CPA blocks the calcium access channel of the enzyme. The inhibition may involve the binding of CPA with a divalent cation such as Mg2+. The potential for CPA to act as a chelator also has implications for methods to detect this toxin. Certain of the lanthanide metals undergo a dramatic increase in luminescence upon coordination with small molecules that can transfer excitation energy to the metal. This report is the first to describe the coordination of CPA with lanthanide metals, resulting in a substantial enhancement of their luminescence. The luminescence expressed was dependent upon the type of lanthanide, its concentration, and the environment (solvent, water content, pH). Based upon the phenomenon, a competitive assay was also developed wherein terbium (Tb3+) and a series of metal cations competed for binding with CPA. With increasing cation concentration, the luminescence of the CPA/Tb3+ complex was inhibited. The chlorides of ten metals were tested. Inhibition was best with Cu2+, followed by Co2+, Al3+, Fe3+, Mn2+, Au3+, Mg2+, and Ca2+. Two cations in oxidation state one (Na⁺, K⁺) did not inhibit the interaction significantly. The interaction of CPA with lanthanides provides a novel recognition assay for this toxin. It also provides a novel way to probe the binding of CPA to metals, giving insights into CPA’s mechanism of action.

Aptamer-based polyhedral oligomeric silsesquioxane (POSS)-containing hybrid affinity monolith prepared via a "one-pot" process for selective extraction of ochratoxin A

A novel aptamer-based polyhedral oligomeric silsesquioxane (POSS)-containing hybrid affinity monolith has been prepared with a facile "one-pot" process simultaneously via "free radical polymerization" and "thiol-ene" click reaction, and used for on-line selective extraction and practical analysis to trace ochratoxin A (OTA). By using the ternary porogenic mixture composed of water/DMF/PEG, a homogeneous polymerization mixture with POSS chemicals, acrylate-based monomers and aptamer aqueous solution was obtained, and the copolymerization of POSS chemicals, polymer monomers and aptamer aqueous solution was systematically studied. Characterizations such as the morphology, FT-IR and fluorescence spectra, mechanical stability, dynamic binding capacity, cross-reactivity and selectivity of the resultant affinity monolith were also evaluated. Attributed to the porous monolithic structure and aptamer-based affinity interaction, acceptable selective recognition and recovery yields towards trace OTA were obtained. With a 5-fold volume enrichment, the limit of detection (LOD) and limit of quantitation (LOQ) of OTA in fortified beer samples were gained at 0.025 ng/mL (S/N = 3) and 0.045 ng/mL (S/N = 10), respectively. It could be competent for the sensitive measure of actual OTA residues in real beer samples. In comparison with the previously reported strategies containing common "sol-gel" chemistry, the proposed protocol to fabricating aptamer-modified POSS-containing hybrid affinity monolith showed a simpler preparation with acceptable selectivity and higher recovery to trace OTA.

Solid phase extraction as sample treatment for the determination of Ochratoxin A in foods: A review

Ochratoxin A (OTA) is a mycotoxin produced by two main types of fungi, Aspergillus and Penicillium species. OTA is a natural contaminant found in a large number of different matrices and is considered as a possible carcinogen for humans. Hence, low maximum permitted levels in foods have been established by competent authorities around the world, making essential the use of very sensitive analytical methods for OTA detection. Sample treatment is a crucial step of analytical methodology to get clean and concentrated extracts, and therefore low limits of quantification. Solid phase extraction (SPE) is a useful technique for rapid and selective sample preparation. This sample treatment enables the concentration and purification of analytes from the sample solution or extract by sorption on a solid sorbent. This review is focused on sample treatment procedures based on SPE prior to the determination of OTA in food matrices, published from 2010.

Aptamers for respiratory syncytial virus detection

The identification of the infectious agents is pivotal for appropriate care of patients with viral diseases. Current viral diagnostics rely on selective detection of viral nucleic acid or protein components. In general, detection of proteins rather than nucleic acids is technically more suitable for rapid tests. However, protein-based virus identification methods depend on antibodies limiting the practical applicability of these approaches. Aptamers rival antibodies in target selectivity and binding affinity, and excel in terms of robustness and cost of synthesis. Although aptamers have been generated for virus identification in laboratory settings, their introduction into routine virus diagnostics has not been realized, yet. Here, we demonstrate that the rationally designed SELEX protocol can be applied on whole virus to select aptamers, which can potentially be applied for viral diagnostics. This approach does not require purified virus protein or complicated virus purification. The presented data also illustrate that corroborating the functionality of aptamers with various approaches is essential to pinpoint the most appropriate aptamer amongst the panel of candidates obtained by the selection. Our protocol yielded aptamers capable of detecting respiratory syncytial virus (RSV), an important pathogen causing severe disease especially in young infants, at clinically relevant concentrations in complex matrices.

Use of anchor protein modules in fluorescence polarisation aptamer assay for ochratoxin A determination

A new strategy for sensitive fluorescence polarisation (FP) analysis is proposed which uses aptamer as the receptor and anchor protein modules as the enhancers by including the aptamers in complexes with protein modules. This approach is based on increasing the size differences of bound and unbound fluorophores. The strategy was applied in an ochratoxin A (ОТА) assay with the competitive binding of fluorophore-labelled and free OTA with aptamer-based receptors. We showed that the binding of labelled OTA with aptamer included in complexes with anchors led to higher a FP than binding with free aptamer. This allowed the aptamer concentration to be reduced, thus lowering the limit of detection by a factor of 40, down to 3.6 nM. The assay time was 15 min. To evaluate the applicability of the FP assay with aptamer-anchor complex to real samples, we conducted OTA measurements in spiked white wine. The OTA limit of detection in wine was 2.8 nM (1.1 μg/kg), and the recoveries ranged from 83% to 113%. The study shows that the proposed anchor strategy is efficient for increasing the sensitivity of FP-based aptamer assays.

Selective tools for the solid-phase extraction of Ochratoxin A from various complex samples: immunosorbents, oligosorbents, and molecularly imprinted polymers

The evolution of instrumentation in terms of separation and detection has allowed a real improvement of the sensitivity and the analysis time. However, the analysis of ultra-traces of toxins such as ochratoxin A (OTA) from complex samples (foodstuffs, biological fluids…) still requires a step of purification and of preconcentration before chromatographic determination. In this context, extraction sorbents leading to a molecular recognition mechanism appear as powerful tools for the selective extraction of OTA and of its structural analogs in order to obtain more reliable and sensitive quantitative analyses of these compounds in complex media. Indeed, immunosorbents and oligosorbents that are based on the use of immobilized antibodies and of aptamers, respectively, and that are specific to OTA allow its selective clean-up from complex samples with high enrichment factors. Similar molecular recognition mechanisms can also be obtained by developing molecularly imprinted polymers, the synthesis of which leads to the formation of cavities that are specific to OTA, thus mimicking the recognition site of the biomolecules. Therefore, the principle, the advantages, the limits of these different types of extraction tools, and their complementary behaviors will be presented. The introduction of these selective tools in miniaturized devices will also be discussed.

A qPCR aptasensor for sensitive detection of aflatoxin M1

Aflatoxin M1 (AFM1), one of the most toxic mycotoxins, imposes serious health hazards. AFM1 had previously been classified as a group 2B carcinogen [1] and has been classified as a group 1 carcinogen by the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) [2]. Determination of AFM1 thus plays an important role for quality control of food safety. In this work, a sensitive and reliable aptasensor was developed for the detection of AFM1. The immobilization of aptamer through a strong interaction with biotin-streptavidin was used as a molecular recognition element, and its complementary ssDNA was employed as the template for a real-time quantitative polymerase chain reaction (RT-qPCR) amplification. Under optimized assay conditions, a linear relationship (ranging from 1.0 × 10(-4) to 1.0 μg L(-1)) was achieved with a limit of detection (LOD) down to 0.03 ng L(-1). In addition, the aptasensor developed here exhibits high selectivity for AFM1 over other mycotoxins and small effects from cross-reaction with structural analogs. The method proposed here has been successfully applied to quantitative determination of AFM1 in infant rice cereal and infant milk powder samples. Results demonstrated that the current approach is potentially useful for food safety analysis, and it could be extended to a large number of targets.

Recent Advances for the Detection of Ochratoxin A

Ochratoxin A (OTA) is one of the mycotoxins secreted by Aspersillus and Penicillium that can easily colonize various grains like coffee, peanut, rice, and maize. Since OTA is a chemically stable compound that can endure the physicochemical conditions of modern food processing, additional research efforts have been devoted to develop sensitive and cost-effective surveillance solutions. Although traditional chromatographic and immunoassays appear to be mature enough to attain sensitivity up to the regulation levels, alternative detection schemes are still being enthusiastically pursued in an attempt to meet the requirements of rapid and cost-effective detections. Herein, this review presents recent progresses in OTA detections with minimal instrumental usage, which have been facilitated by the development of OTA aptamers and by the innovations in functional nanomaterials. In addition to the introduction of aptamer-based OTA detection techniques, OTA-specific detection principles are also presented, which exclusively take advantage of the unique chemical structure and related physicochemical characteristics.

A time-resolved luminescent competitive assay to detect L-selectin using aptamers as recognition elements

L-selectin is a protein with potential importance for numerous diseases and clinical disorders. In this paper, we present a new aptamer-based luminescent assay developed to detect L-selectin. The sensing system working principle is based on Förster Resonance Energy Transfer (FRET) from a donor terbium complex (TbC) to an acceptor cyanine dye (Cy5). In the present approach, the biotinylated aptamer is combined with Cy5-labelled streptavidin (Cy5-Strep) to yield an aptamer-based acceptor construct (Apta-Cy5-Strep), while L-selectin is conjugated using luminescent TbC. Upon aptamer binding to the TbC-labelled L-selectin (L-selectin-TbC), permanent donor-acceptor proximity is established which allows for radiationless energy transfer to occur. However, when unlabelled L-selectin is added, it competes with the L-selectin-TbC and the FRET signal decreases as the L-selectin concentration increases. FRET from the TbC to Cy5 was observed with time-gated time-resolved luminescence spectroscopy. A significant change in the corrected luminescence signal was observed in the dynamic range of 10-500 ng/mL L-selectin, the concentration range relevant for accelerated cognitive decline of Alzheimer's disease, with a limit of detection (LOD) equal to 10 ng/mL. The aptasensor-based assay is homogeneous and can be realized within one hour. Therefore, this method has the potential to become an alternative to tedious heterogeneous analytical methods, e.g. based on enzyme-linked immunosorbent assay (ELISA).

A review on immobilised aptamers for high throughput biomolecular detection and screening

The discovery of Systematic Evolution of Ligands by Exponential Enrichment (SELEX) assay has led to the generation of aptamers from libraries of nucleic acids. Concomitantly, aptamer-target recognition and its potential biomedical applications have become a major research endeavour. Aptamers possess unique properties that make them superior biological receptors to antibodies with a plethora of target molecules. Some specific areas of opportunities explored for aptamer-target interactions include biochemical analysis, cell signalling and targeting, biomolecular purification processes, pathogen detection and, clinical diagnosis and therapy. Most of these potential applications rely on the effective immobilisation of aptamers on support systems to probe target species. Hence, recent research focus is geared towards immobilising aptamers as oligosorbents for biodetection and bioscreening. This article seeks to review advances in immobilised aptameric binding with associated successful milestones and respective limitations. A proposal for high throughput bioscreening using continuous polymeric adsorbents is also presented.

Single-Stranded DNA Aptamers against Pathogens and Toxins: Identification and Biosensing Applications

Molecular recognition elements (MREs) can be short sequences of single-stranded DNA, RNA, small peptides, or antibody fragments. They can bind to user-defined targets with high affinity and specificity. There has been an increasing interest in the identification and application of nucleic acid molecular recognition elements, commonly known as aptamers, since they were first described in 1990 by the Gold and Szostak laboratories. A large number of target specific nucleic acids MREs and their applications are currently in the literature. This review first describes the general methodologies used in identifying single-stranded DNA (ssDNA) aptamers. It then summarizes advancements in the identification and biosensing application of ssDNA aptamers specific for bacteria, viruses, their associated molecules, and selected chemical toxins. Lastly, an overview of the basic principles of ssDNA aptamer-based biosensors is discussed.

Aptamer-based technology for food analysis

Aptamers are short and functional single-stranded oligonucleotide sequences selected from systematic evolution of ligands by exponential enrichment (SELEX) process, which have the capacity to recognize various classes of target molecules with high affinity and specificity. Various analytical aptamers acquired by SELEX are widely used in many research fields, such as medicine, biology, and chemistry. However, the application of this innovative and emerging technology to food safety is just in infant stage. Food safety plays a very important role in our daily lives because varieties of poisonous and harmful substances in food affect human health. Aptamer technique is promising, which can overcome many disadvantages of existing detection methods in food safety, such as long detection time, low sensitivity, difficult, and expensive antibody preparation. This review provides an overview of various aptamer screening technologies and summarizes the recent applications of aptamers in food safety, and future prospects are also discussed.

Aptamer-based-sorbents for sample treatment--a review

To improve selectivity during sample pretreatment, various selective tools inducing a molecular recognition mechanism during the extraction procedure have been developed, such as sorbents constituted of immobilized antibodies, i.e., immunosorbents, or molecularly imprinted polymers. More recently, as an alternative to both previous approaches, aptamers immobilized onto a solid support, i.e., oligosorbents, were proposed. Thanks to the high affinity and high selectivity of the interaction that some aptamers offer toward some target analytes, they also provide powerful techniques that make selective extraction and the concentration of a target analyte from liquid matrices in one step or sample purification of extracts from solid matrices possible. This review describes the development and the properties of these oligosorbents developed for different types of targets-pharmaceuticals, mycotoxins, proteins, cells, etc. After describing the immobilization procedures, we discuss different parameters characterizing the potential of aptamer-based supports as extraction sorbents. Close relations exist between extraction recoveries and the affinity and amounts of aptamers immobilized on the extraction device. In addition, analyte-aptamer interactions may be affected by matrix components and by additives in the samples. This may also lower extraction recoveries and affect the stability and the possible reusability of the aptamer-based sorbent. All these points are discussed and illustrated. Numerous examples of applications of these sorbents to the treatment of complex samples such as food samples, environmental samples, and biological fluids are also reported. Their association with analytical devices, from conventional to miniaturized analytical systems, is also discussed.

Aptamer-affinity column clean-up coupled with ultra high performance liquid chromatography and fluorescence detection for the rapid determination of ochratoxin A in ginger powder

Aptamers are single-stranded oligonucleotides with high affinity and specificity and are widely used in targets separation and enrichment. Here, an aptamer-affinity column (AAC) was firstly prepared in-house through a covalent immobilization strategy. Then, ochratoxin A (OTA) in ginger powder was absorbed and enriched using the new aptamer-based clean-up technology for the first time, and was further analyzed by ultra high performance liquid chromatography with fluorescence detection. After optimization, the average recoveries for blank samples spiked with OTA at 5, 15, and 45 μg/kg ranged from 85.36 to 96.83%. Furthermore, the AAC exhibited a similar accuracy as an immunoaffinity column to clean up OTA in ginger powder. Above all, it exhibited better reusability, twice that of the immunoaffinity column, had lower toxicity and cost, and took less time. Of 25 contaminated ginger powder samples, OTA contamination levels ranged from 1.51 to 4.31 μg/kg, which were lower than the European Union (EU) regulatory limits. All the positive samples were further confirmed by ultra-fast LC with MS/MS. In conclusion, the method of clean-up based on the AAC coupled to ultra-HPLC with fluorescence detection was rapid, specific, and sensitive for the quantitative analysis of OTA in a complex matrix.

Using commercial immunoassay kits for mycotoxins: ‘joys and sorrows’?

Rapid test methods are widely used for measuring mycotoxins in a variety of matrices. This review presents an overview of the current commercially available immunoassay rapid test formats. Enzyme linked immune-sorbent assay (ELISA), lateral flow tests, flow through immunoassay, fluorescent polarisation immunoassay, and immunoaffinity columns coupled with fluorometric assay are common formats in the current market. The two existing evaluation programs for commercial testing kits by United State Department of Agricultural Grain Inspection, Packers & Stockyards Administration (USDA-GIPSA) and AOAC Research Institute are introduced. The strengths and weaknesses of these test kits are discussed with regard to the application scope, variance, specificity and cross reactivity, accuracy and precision, and measurement range. Generally speaking, the current commercially available testing kits meet research and industrial needs as ‘fit-for-purpose’. Furthermore, quality assurance concerns and future perspectives are elaborated for broader application of commercial test kits in research, industry and regulatory applications. It is expected that new commercial kits based on advanced technologies such as electrochemical affinity biosensors, molecularly imprinted polymers, surface plasmon resonance, fluorescence resonance energy transfer, aptamer-based biosensors and dynamic light scattering might be available to users in the future. Meanwhile, harmonisation of testing kit evaluation, incorporation of more quality assurance into the testing kit utilisation scheme, and a larger variety of kits available at lower cost will expand the usage of testing kits for food safety testing worldwide.

Ultrasensitive electrochemical aptasensor for ochratoxin A based on two-level cascaded signal amplification strategy

Ochratoxin A (OTA) has a number of toxic effects to both humans and animals, so developing sensitive detection method is of great importance. Herein, we describe an ultrasensitive electrochemical aptasensor for OTA based on the two-level cascaded signal amplification strategy with methylene blue (MB) as a redox indicator. In this method, capture DNA, aptamers, and reporter DNA functionalized-gold nanoparticles (GNPs) were immobilized on the electrode accordingly, where GNPs were used as the first-level signal enhancer. To receive the more sensitive response, a larger number of guanine (G)-rich DNA was bound to the GNPs' surface to provide abundant anchoring sites for MB to achieve the second-level signal amplification. By employing this novel strategy, an ~8.5 (±0.3) fold amplification in signal intensity was obtained. Afterward, OTA was added to force partial GNPs/G-rich DNA to release from the sensing interface and thus decreased the electrochemical response. An effective sensing range from 2.5pM to 2.5nM was received with an extremely low detection limit of 0.75 (±0.12) pM. This amplification strategy has the potential to be the main technology for aptamer-based electrochemical biosensor in a variety of fields.

Aptamers: a promosing tool for ochratoxin A detection in food analysis

The contamination of food and feed by mycotoxins has become an increasingly serious problem. Mycotoxins represent a major risk to human and animal health, as well as economics. Herein, we focus on Ochratoxin A (OTA), which is one of the most common mycotoxins contaminating feed and foodstuffs. OTA is a secondary metabolite produced by various Aspergillus and Penicillium strains. Upon ingestion, OTA has a number of acute and chronic toxic effects. It is nephrotoxic, teratogenic, immunosuppressive, and carcinogenic (group 2B). As a consequence, some regulatory limits have been introduced on the levels of OTA in several commodities. The toxic nature of OTA demands highly sensitive and selective monitoring techniques to protect human and animal health. As alternative to traditional analytical techniques, biochemical methods for OTA analysis have attained great interest in the last few decades. They are mainly based on the integration of antibodies or aptamers as biorecognition elements in sensing platforms. However, aptamers have gained more attention in affinity-based assays because of their high affinity, specificity, stability, and their easy chemical synthesis. In this brief review, we present an overview of aptamer-based assays and their applications in OTA purification and detection, appeared in the literature in the last five years.

Fluorescent sensing ochratoxin A with single fluorophore-labeled aptamer

We explored a fluorescent strategy for sensing ochratoxin A (OTA) by using a single fluorophore-labeled aptamer for detection of OTA. This method relied on the change of the fluorescence intensity of the labeled dye induced by the specific binding of the fluorescent aptamer to OTA. Different fluorescein labeling sites of aptamers were screened, including the internal thymine bases, 3'-end, and 5'-end of the aptamer, and the effect of the labeling on the aptamer affinity was investigated. Some fluorophore-labeled aptamers showed a signal-on or signal-off response. With the fluorescent aptamer switch, simple, rapid, and selective sensing of OTA at nanomolar concentrations was achieved. OTA spiked in diluted red wine could be detected, showing the feasibility of the fluorescent aptamer for a complex matrix. This method shows potential for designing aptamer sensors for other targets.

Nucleic acid aptamers as high affinity ligands in biotechnology and biosensorics

Aptamers are small nucleic acid molecules capable of binding to a wide range of target molecules with high affinity and specificity. They have been developed and widely used not only as research tools, but also as biosensors, specific antagonists, and diagnostic markers and as protein purification platform for many pharmaceutical and clinical applications. Here, in this paper we will explore biochemical aspects of aptamer-target interactions and show why aptamers rival antibodies in target recognition and purification procedures. This review will focus on strategies of using aptamers as affinity ligands for molecules of therapeutic and pharmaceutical interest including applications in chromatography and capillary electrophoresis for protein and small molecule purification. Moreover, we will also discuss aptamers whose binding parameters can be controlled on demand for diagnostic approaches and used as sensitive receptors in biosensorics. Aptamers have opened up exciting fields in basic and applied research of pharmaceutical and biotechnological interest.

Challenges and opportunities for small molecule aptamer development

Aptamers are single-stranded oligonucleotides that bind to targets with high affinity and selectivity. Their use as molecular recognition elements has emerged as a viable approach for biosensing, diagnostics, and therapeutics. Despite this potential, relatively few aptamers exist that bind to small molecules. Small molecules are important targets for investigation due to their diverse biological functions as well as their clinical and commercial uses. Novel, effective molecular recognition probes for these compounds are therefore of great interest. This paper will highlight the technical challenges of aptamer development for small molecule targets, as well as the opportunities that exist for their application in biosensing and chemical biology.

Challenges and opportunities for small molecule aptamer development

Aptamers are single-stranded oligonucleotides that bind to targets with high affinity and selectivity. Their use as molecular recognition elements has emerged as a viable approach for biosensing, diagnostics, and therapeutics. Despite this potential, relatively few aptamers exist that bind to small molecules. Small molecules are important targets for investigation due to their diverse biological functions as well as their clinical and commercial uses. Novel, effective molecular recognition probes for these compounds are therefore of great interest. This paper will highlight the technical challenges of aptamer development for small molecule targets, as well as the opportunities that exist for their application in biosensing and chemical biology.