Impedimetric aptasensor for tobramycin detection in human serum

Design and application of an ultrasensitive and selective tobromycin electrochemiluminescence aptasensor using MXene /Ni/Sm-LDH-based nanocomposite

Using a chemiluminescence reaction between luminol and H2O2 in basic solution, an ultrasensitive electrochemiluminescence (ECL) aptasensor was developed for the determination of tobramycin (TOB), as an aminoglycoside antibiotic. Ti3C2/Ni/Sm-LDH-based nanocomposite effectively catalyzes the oxidation of luminol and decomposition of H2O2, leading to the formation of different reactive oxygen species (ROSs), thus amplifying the ECL signal intensity of luminol, which can be used for the determination of TOB concentration. To evaluate the performance of the electrochemiluminescence aptasensor and synthesized nanocomposite, different methods such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) analyses were performed. The considerable specific area, large number of active sites, and enhanced electron transfer reaction on this nanocomposite led to the development of an ECL aptasensor with high sensitivity and electrocatalytic activity. After optimizing the preparation method and analysis conditions, the aptasensor revealed a wide linear response ranging from 1.0 pM to 1.0 μM with a detection limit of 18 pM, displaying outstanding accuracy, specificity, and response stability. The developed ECL sensor was found to be applicable to the determination of TOB in human serum samples and is anticipated to possess excellent clinical potentials for detecting other antibiotics, as well.

Displacement Assay in a Polythiophene Sensor System Based on Supramacromolecuar Disassembly-Caused Emission Quenching

Exploring new methodologies for simple and on-demand methods of manipulating the emission and sensing ability of fluorescence sensor devices with solid-state emission molecular systems is important for realizing on-site sensing platforms. In this regard, although conjugated polymers (CPs) are some of the best candidates for preparing molecular sensor devices owing to their luminescent and molecular recognition properties, the development of CP-based sensor devices is still in its early stages. In this study, we herein propose a novel strategy for preparing a chemical stimuli-responsive solid-state emission system based on supramacromolecular assembly-induced emission enhancement (SmAIEE). The system was spontaneously developed by mixing only the component polymers (i.e., polythiophene and a transient cross-linking polymer). The proposed strategy can be applied to the facile preparation of molecular sensor devices. The analyte-induced fluorescent response of polythiophene originated from the dynamic displacement of the transient cross-linker in the polythiophene ensemble and the generation of the polythiophene-analyte complex. Our successful demonstration of the spontaneous preparation of the fluorescence sensor system by mixing two component polymers could lead to the development of on-site molecular analyzers including the determination of multiple analytes.

A novel strategy for therapeutic drug monitoring: application of biosensors to quantify antimicrobials in biological matrices

Over the past few years, therapeutic drug monitoring (TDM) has gained practical significance in antimicrobial precision therapy. Yet two categories of mainstream TDM techniques (chromatographic analysis and immunoassays) that are widely adopted nowadays retain certain inherent limitations. The use of biosensors, an innovative strategy for rapid evaluation of antimicrobial concentrations in biological samples, enables the implementation of point-of-care testing (POCT) and continuous monitoring, which may circumvent the constraints of conventional TDM and provide strong technological support for individualized antimicrobial treatment. This comprehensive review summarizes the investigations that have harnessed biosensors to detect antimicrobial drugs in biological matrices, provides insights into the performance and characteristics of each sensing form, and explores the feasibility of translating them into clinical practice. Furthermore, the future trends and obstacles to achieving POCT and continuous monitoring are discussed. More efforts are necessary to address the four key 'appropriateness' challenges to deploy biosensors in clinical practice, paving the way for personalized antimicrobial stewardship.

Electrochemical Aptasensors for Antibiotics Detection: Recent Achievements and Applications for Monitoring Food Safety

Antibiotics are often used in human and veterinary medicine for the treatment of bacterial diseases. However, extensive use of antibiotics in agriculture can result in the contamination of common food staples such as milk. Consumption of contaminated products can cause serious illness and a rise in antibiotic resistance. Conventional methods of antibiotics detection such are microbiological assays chromatographic and mass spectroscopy methods are sensitive; however, they require qualified personnel, expensive instruments, and sample pretreatment. Biosensor technology can overcome these drawbacks. This review is focused on the recent achievements in the electrochemical biosensors based on nucleic acid aptamers for antibiotic detection. A brief explanation of conventional methods of antibiotic detection is also provided. The methods of the aptamer selection are explained, together with the approach used for the improvement of aptamer affinity by post-SELEX modification and computer modeling. The substantial focus of this review is on the explanation of the principles of the electrochemical detection of antibiotics by aptasensors and on recent achievements in the development of electrochemical aptasensors. The current trends and problems in practical applications of aptasensors are also discussed.

A novel aptasensor for colorimetric monitoring of tobramycin: Strategy of enzyme-like activity of AuNPs controlled by three-way junction DNA pockets

In this study, a novel colorimetric sensor was introduced to detect tobramycin (TOB) based on controlling the catalytic activity of gold nanoparticles (AuNPs) by the three-way junction aptamer pockets. In the absence of TOB, the surfaces of AuNPs were masked by the three-way junction pockets that prevented their catalytic activation for the reduction of 4-Nitrophenol in the presence of NaBH₄. While the formation of the pockets was prevented in the presence of TOB that facilitated the 4-Nitrophenol access to AuNPs. Hence, the catalytic reduction of 4-Nitrophenol induced a color change of the solution from yellow to colorless, highlighting the presence of the target. The aptasensing assay provided good target specificity with a detection limit (LOD) of 1.16 µM and a linear dynamic range over 4-32 µM. The aptasensor was successfully applied to quantitatively monitor TOB in the human serum and milk samples with the LODs of 1.38 and 1.42 µM and recovery values of 94.87-105.75% and 93.75-105.31%, respectively.

A lateral flow strip for on-site detection of tobramycin based on dual-functional platinum-decorated gold nanoparticles

A novel lateral flow strip assay has been developed for rapid on-site detection of tobramycin. In this assay, unique dual-functional platinum-decorated gold nanoparticles (Au@Pt NPs) are synthesized by covering conventional gold nanoparticles (AuNPs) with an ultra-thin Pt film. Au@Pt NPs retain the plasmon activity of AuNPs and exhibit ultra-high catalytic activity that the Pt skin can achieve. The aptamer (Apt) specific for tobramycin and its complementary DNA (cDNA) are loaded on Au@Pt NPs as a duplex probe through the thiol group modified at the 5' end of the cDNA. When tobramycin is present, it binds specifically to the aptamer, resulting in its dehybridization from the cDNA and detachment from the surface of Au@Pt NPs. Then Au@Pt NPs can be captured by the fixed probe (DNA1) on the test zone (T zone) of the lateral flow strip through the hybridization between DNA1 and cDNA. The dual-functional Au@Pt NPs provide two different detection modes: one is based on the color of AuNPs (low sensitivity mode) and the other is based on the chromogenic reaction catalyzed by the Pt nanozyme (high sensitivity mode). The strip can complete the visual detection process of tobramycin within 10 min, and the cutoff values for the naked eye detection in the two modes are 60 nM and 5 nM, respectively. Furthermore, using a portable scanning reader and ImageJ software, quantitative detection can be achieved. The limits of detection (LOD) of the two modes are 0.09 nM and 0.02 nM, respectively. The strip has been successfully applied to detect tobramycin in different food samples. Therefore, Au@Pt NPs and the strip provide a highly sensitive, rapid and economical way for in-spot detection of tobramycin residues. The strip can be run in two modes, which can realize the on-demand adjustment of the detection performance and offer wider application prospects in diverse scenarios.

Contribution of Nanomaterials to the Development of Electrochemical Aptasensors for the Detection of Antimicrobial Residues in Food Products

The detection of antimicrobial residues in food products of animal origin is of utmost importance. Indeed antimicrobial residues could be present in animal derived food products because of animal treatments for curative purposes or from illegal use. The usual screening methods to detect antimicrobial residues in food are microbiological, immunological or physico-chemical methods. The development of biosensors to propose sensitive, cheap and quick alternatives to classical methods is constantly increasing. Aptasensors are one of the major trends proposed in the literature, in parallel with the development of immunosensors based on antibodies. The characteristics of electrochemical sensors (i.e., low cost, miniaturization, and portable instrumentation) make them very good candidates to develop screening methods for antimicrobial residues in food products. This review will focus on the recent advances in the development of electrochemical aptasensors for the detection of antimicrobial residues in food products. The contribution of nanomaterials to improve the performance characteristics of electrochemical aptasensors (e.g., Sensitivity, easiness, stability) in the last ten years, as well as signal amplification techniques will be highlighted.

Advances in Gold Nanoparticles-Based Colorimetric Aptasensors for the Detection of Antibiotics: An Overview of the Past Decade

Misuse of antibiotics has recently been considered a global issue because of its harmful effects on human health. Since conventional methods have numerous limitations, it is necessary to develop fast, simple, sensitive, and reproducible methods for the detection of antibiotics. Among numerous recently developed methods, aptasensors are fascinating because of their good specificity, sensitivity and selectivity. These kinds of biosensors combining aptamer with colorimetric applications of gold nanoparticles to recognize small molecules are becoming more popular owing to their advantageous features, for example, low cost, ease of use, on-site analysis ability using naked eye and no prerequisite for modern equipment. In this review, we have highlighted the recent advances and working principle of gold nanoparticles based colorimetric aptasensors as promising methods for antibiotics detection in different food and environmental samples (2011–2020). Furthermore, possible advantages and disadvantages have also been summarized for these methods. Finally, the recent challenges, outlook, and promising future perspectives for developing novel aptasensors are also considered.

Pinacho D. Personalized Medicine for Antibiotics: The Role of Nanobiosensors in Therapeutic Drug Monitoring

Due to the high bacterial resistance to antibiotics (AB), it has become necessary to adjust the dose aimed at personalized medicine by means of therapeutic drug monitoring (TDM). TDM is a fundamental tool for measuring the concentration of drugs that have a limited or highly toxic dose in different body fluids, such as blood, plasma, serum, and urine, among others. Using different techniques that allow for the pharmacokinetic (PK) and pharmacodynamic (PD) analysis of the drug, TDM can reduce the risks inherent in treatment. Among these techniques, nanotechnology focused on biosensors, which are relevant due to their versatility, sensitivity, specificity, and low cost. They provide results in real time, using an element for biological recognition coupled to a signal transducer. This review describes recent advances in the quantification of AB using biosensors with a focus on TDM as a fundamental aspect of personalized medicine.

Impedimetric Aptamer-Based Biosensors: Applications

Impedimetric aptamer-based biosensors show high potential for handheld devices and point-of-care tests. In this review, we report on recent advances in aptamer-based impedimetric biosensors for applications in biotechnology. We detail on analytes relevant in medical and environmental biotechnology as well as food control, for which aptamer-based impedimetric biosensors were developed. The reviewed biosensors are examined for their performance, including sensitivity, selectivity, response time, and real sample validation. Additionally, the benefits and challenges of impedimetric aptasensors are summarized.

Aptamer-based ellipsometric sensor for ultrasensitive determination of aminoglycoside group antibiotics from dairy products

BACKGROUND

Residual antibiotics taken along with food consumed through the food chain are the main cause of the super-bacteria and may damage organs such as liver and kidney. Therefore, monitoring residual antibiotic levels of products in the food chain is both important and a requirement. Maximum residual limits for kanamycin and neomycin are 150 ng mL^-1 and 500 ng mL^-1 respectively, which are challenging for most sensor platforms. In this paper, a novel method is presented for the determination of antibiotics residues in animal-derived foods.

RESULTS

Aptamer-based kanamycin and neomycin biosensors based on the spectroscopic ellipsometer and the surface plasmon resonance-enhanced total internal reflection ellipsometer methods as transducing element were developed. Detection limits of both sensor platforms were in the 0.1-1 nmol L^-1 ranges, and the detection range was between the detection limit and 1000 nmol L^-1 .

CONCLUSION

Both ellipsometry-based aptasensors can be used as an alternative to the existing enzyme-linked immunosorbent assay-based method in terms of assay time (10 min), detection limit (0.22 ng mL^-1 for neomycin and 0.048 ng mL^-1 for kanamycin), and detection range. © 2020 Society of Chemical Industry.

Aptamer-Based Biosensors for Antibiotic Detection: A Review

Antibiotic resistance and, accordingly, their pollution because of uncontrolled usage has emerged as a serious problem in recent years. Hence, there is an increased demand to develop robust, easy, and sensitive methods for rapid evaluation of antibiotics and their residues. Among different analytical methods, the aptamer-based biosensors (aptasensors) have attracted considerable attention because of good selectivity, specificity, and sensitivity. This review gives an overview about recently-developed aptasensors for antibiotic detection. The use of various aptamer assays to determine different groups of antibiotics, like β-lactams, aminoglycosides, anthracyclines, chloramphenicol, (fluoro)quinolones, lincosamide, tetracyclines, and sulfonamides are presented in this paper.

Gold nanoparticle based photometric determination of tobramycin by using new specific DNA aptamers

A magnetic bead-based SELEX was applied to identify 37 single-stranded DNA aptamers specific for tobramycin after ten rounds of selection. The aptamers were classified into nine families according to sequence analysis. Among them, several aptamers with typical sequences were selected and their dissociation constants (K_ds) were determined by a fluorescent method. An aptamer termed "Ap 32", with a K_d value of 56.8 ± 4.6 nM, possesses the highest affinity and satisfactory specificity. Theoretical modeling showed that nucleotides 14-18 and 26-29 play a most significant role in the interaction between aptamer and tobramycin. Subsequently, the sequence of Ap 32 was optimized through rationally designed truncation. The truncated aptamer Ap 32-2 consists of 34 nucleotides and has a K_d that is similar to the original one. It was chosen as the optimal aptamer for use in the assay and was immobilized on gold nanoparticles. On addition of tobramycin, the color turns from red to purple. The findings were used to design a photometric assay (best performed at 520 nm) that has a linear response in the 100 nM to 1.4 μM concentration range, with a 37.9 nM detection limit. The method was successfully applied to the determination of tobramycin in (spiked) honey samples. Graphical abstract A 34-nucleotide aptamer specific for tobramycin was obtained through magnetic beads-based systematic evolution of ligands by exponential enrichment (SELEX) and structural analysis-based rational post-SELEX truncation, and then applied to the determination of tobramycin using a gold nanoparticle-based photometric assay.

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.

Selection and Biosensor Application of Aptamers for Small Molecules

Small molecules play a major role in the human body and as drugs, toxins, and chemicals. Tools to detect and quantify them are therefore in high demand. This review will give an overview about aptamers interacting with small molecules and their selection. We discuss the current state of the field, including advantages as well as problems associated with their use and possible solutions to tackle these. We then discuss different kinds of small molecule aptamer-based sensors described in literature and their applications, ranging from detecting drinking water contaminations to RNA imaging.

Aptamer-based sensing of β-casomorphin-7

β-Casomorphin-7 (BCM-7), a seven amino acid peptide, is released during digestion of β-casein A1 variant of milk which is speculated to be associated with certain diseases. Fifteen ssDNA aptamers having high affinity toward BCM-7 were identified from a 72 nt long random library after ten rounds of systematic evolution of ligands by exponential enrichment. Dissociation constant values of selected aptamers were in the range of 7.7-156.7 nM. Seq6 aptamer exhibited the lowest Kd value. Nine aptamers were evaluated for their binding toward BCM-7, BCM-9A1, and BCM-9A2 peptides, and binding was variable. SeqU5 exhibited the lowest binding with BCM-9A1 and BCM-9A2. Aptamer-coated gold nanoparticles (GNPs) resulted in color change of GNPs in the presence of BCM-7, thereby establishing recognition of BCM-7 by aptamers. The enzyme-linked aptamer-sorbent assay (ELASA) was evaluated as an assay of BCM-7 in biological fluids. BCM-7-peroxidase competed with BCM-7 in ELASA, performed with BCM-7 solution and BCM-7 spiked urine pretreated with urease, plasma, and β-casein digest samples.

A simple and label-free aptasensor based on nickel hexacyanoferrate nanoparticles as signal probe for highly sensitive detection of 17β-estradiol

A simple and label-free electrochemical aptasensor was developed for detecting 17β-estradiol (E2). To translate the binding events between aptamer and E2 into the measurable electrochemical signal, the nickel hexacyanoferrate nanoparticles (NiHCF NPs) as signal probe was in situ introduced on the electrode by a simple two-step deposition method, exhibiting well-defined peaks with good stability and reproducibility. Subsequently, Au nanoparticles (Au NPs) was covered on the NiHCF NPs, which not only provided a platform for immobilizing the aptamer by S-Au interaction, but further enhanced the conductivity and stability of the signal probe. With the addition of E2, the formation of E2-aptamer complexes on the sensing interface retarded the interfacial electron transfer reaction of the probe, resulting in the decrease of the electrochemical signal. E2 could be readily examined by measuring the signal change. A linear range of 1×10(-12)-6×10(-10) M was obtained with a low detection limit of 0.8×10(-12) M. The aptasensor also exhibited high specificity to E2 in control experiments employing seven endocrine disrupting compounds as the interferents that had similar structure or coexisted with E2 in the environment. Besides, the applicability of the aptasensor was successfully evaluated by determining E2 in the real samples.

Aptamer and its potential applications for food safety

Accompanied by industrial globalization, rapid urbanization, and population increment, mass production and staple trading for food consumption are upsoaring continuously, foodborne disease resulted from various food safety issues is currently a crucial public health concern worldwide, which has not only created a great burden on both economy and society, but also greatly threatened the sustainability of mankind's livelihood and human reproduction. In order to better ensure food safety and thus effectively curb the occurrence of foodborne diseases, the development and evolving of inspection strategies are indispensable measures for quality assurance and conformity assessment. Nowadays, as complementary measures to and with advantageous merits over classic analytical methods, highly specific and selective aptamer-based assays have found their increasingly important roles in various domains of food analysis. This critical review summarizes the advantages of aptamer as compared with antibody, introduces important evolving variants of systematic evolution of ligands by exponential enrichment (SELEX), and presents an overview of potential aptamer applications for food safety.

Selection and identification of streptomycin-specific single-stranded DNA aptamers and the application in the detection of streptomycin in honey

Single-stranded DNA (ssDNA) aptamers specific to streptomycin were screened and identified from a random oligonucleotides library by affinity magnetic beads-based SELEX. After eight rounds of selection, 16 ssDNA with different sequences were identified. Then the dissociation constants (Kd) of these ssDNA were determined and an aptamer (STR1) with highest affinity for streptomycin was identified. Further study showed that aptamer STR1 exhibits very low affinity for other aminoglycoside antibiotics, indicating high specificity. With this aptamer, detection of streptomycin was achieved by using gold nanoparticles (AuNPs)-based colorimetric method. In the presence of streptomycin, the competitive binding of the target and the aptamer decreases the stability of AuNPs in NaCl solution, triggers the aggregation, and exhibits visible color change of AuNPs solution. Through UV-visible spectroscopic quantitative analysis, streptomycin can be detected in the range of 0.2-1.2 μM. The presence of other aminoglycoside antibiotics shows neglectable disturbance. Furthermore, the established method was utilized to detect streptomycin in honey, and the same low detection limit and linear detection range were achieved.

Comparative study on aptamers as recognition elements for antibiotics in a label-free all-polymer biosensor

We present an all-polymer electrochemical microfluidic biosensor using Topas(®) as substrate and a conductive polymer bilayer as electrode material. The conductive bilayer consists of tosylate doped poly(3,4-ethylenedioxythiophene) (PEDOT:TsO) and the hydroxymethyl derivative PEDOT-OH:TsO, which was covalently functionalized with two aptamer probes with affinity to ampicillin or kanamycin A, respectively. Using electrochemical impedance spectroscopy (EIS) we were able to detect ampicillin in a concentration range from 100pM to 1μM and kanamycin A from 10nM to 1mM. The obtained EIS spectra were fitted with an equivalent circuit model successfully explaining the impedance signal. Real samples from regular ultra-high temperature treated low-fat milk spiked with ampicillin were successfully tested to assess the functionality of the sensor with real samples. In conclusion, we have demonstrated the applicability of the newly developed platform for real time, label-free and selective impedimetric detection of commonly used antibiotics. Additionally it was possible to detect ampicillin in a milk sample at a concentration below the allowed maximum residue limit (MRL) in the European Union.

SPR evaluation of binding kinetics and affinity study of modified RNA aptamers towards small molecules

Establishing an efficient method for evaluating the affinity changes after post-SELEX modification of aptamers is essential for broadening the application of these oligonucleotides in biosensing. This is especially challenging when the ligand is a small molecule. Changes in affinity upon partial or total replacement of 2'-OH with 2'-OMe groups in the ribose moieties of a tobramycin binding RNA aptamer are described. The kinetic profile and binding properties of the different anti-tobramycin aptamers were measured by surface plasmon resonance (SPR) experiments through a real-time binding assay with the antibiotic covalently coupled to the gold sensor. This configuration maximizes the changes associated to the recognition event, which is otherwise undetectable. The results indicated that the modification slightly affects the binding characteristics of the parent RNA, while conferring biological stability to the aptamers against nucleases.

Aptamers for pharmaceuticals and their application in environmental analytics

Aptamers are single-stranded DNA or RNA oligonucleotides, which are able to bind with high affinity and specificity to their target. This property is used for a multitude of applications, for instance as molecular recognition elements in biosensors and other assays. Biosensor application of aptamers offers the possibility for fast and easy detection of environmental relevant substances. Pharmaceutical residues, deriving from human or animal medical treatment, are found in surface, ground, and drinking water. At least the whole range of frequently administered drugs can be detected in noticeable concentrations. Biosensors and assays based on aptamers as specific recognition elements are very convenient for this application because aptamer development is possible for toxic targets. Commonly used biological receptors for biosensors like enzymes or antibodies are mostly unavailable for the detection of pharmaceuticals. This review describes the research activities of aptamer and sensor developments for pharmaceutical detection, with focus on environmental applications.

An electrochemical aptasensor for chiral peptide detection using layer-by-layer assembly of polyelectrolyte-methylene blue/polyelectrolyte-graphene multilayer

Here we demonstrate for the first time that by physically adsorbing aptamer onto conductive film assembled via alternate adsorption of graphene/polyelectrolyte and methylene blue/polyelectrolyte, a label-free electrochemical aptasensor with high sensitivity and selectivity for peptide detection is constructed. Graphene multilayer derived from layer-by-layer assembly has played significant roles in this sensing strategy: allowing accumulation of methylene blue, facilitating electron transfer and providing much more adsorption site. As compared to previous electrochemical aptasensors, the current sensor based on graphene multilayer alternated with electroactive molecule layer offers extremely high capability for sensitive detection of target without interference of environmental surrounding. This electroactive probe-confined graphene multilayer confers great flexibility to combine with differential pulse voltammetry (DPV) together. In the presence of target d entiomer of arginine vasopressin (D-VP), the binding of peptide to aptamer block the electron transfer process of MB, leading to decreased current peak of DPV. By this way, this electrochemical aptasensor based on electroactive molecule-intercalated graphene multilayer provide highly sensitive and specific detection of D-VP with the lowest detectable concentration of 1 ng mL(-1) and a wide detection range from 1 to 265 ng mL(-1).

Electrochemical Aptamer-Based Biosensors: Recent Advances and Perspectives

This paper reviews the advancements of a wide range of electrochemical aptamer-based biosensors, electrochemical aptasensors, for target analytes monitoring. Methods for immobilizing aptamers onto an electrode surface are discussed. Aptasensors are presented according to their detection strategies. Many of these are simply electrochemical, aptamer-based equivalents of traditional immunochemical approaches, sandwich and competition assays employing electroactive signaling moieties. Others, exploiting the unusual physical properties of aptamers, are signal-on (positive readout signal) and signal-off (negative readout signal) aptasensors based on target binding-induced conformational change of aptamers. Aptamer label-free devices are also discussed.