Naked-eye based point-of-care detection of E.coli O157: H7 by a signal-amplified microfluidic aptasensor

Lab-on-a-Chip Devices for Nucleic Acid Analysis in Food Safety

Lab-on-a-chip (LOC) devices have been developed for nucleic acid analysis by integrating complex laboratory functions onto a miniaturized chip, enabling rapid, cost-effective, and highly sensitive on-site testing. This review examines the application of LOC technology in food safety, specifically in the context of nucleic acid-based analyses for detecting pathogens and contaminants. We focus on microfluidic-based LOC devices that optimize nucleic acid extraction and purification on the chip or amplification and detection processes based on isothermal amplification and polymerase chain reaction. We also explore advancements in integrated LOC devices that combine nucleic acid extraction, amplification, and detection processes within a single chip to minimize sample preparation time and enhance testing accuracy. The review concludes with insights into future trends, particularly the development of portable LOC technologies for rapid and efficient nucleic acid testing in food safety.

Advances in novel biosensors in biomedical applications

Biosensors, devices capable of detecting biomolecules or bioactive substances, have recently become one of the important tools in the fields of bioanalysis and medical diagnostics. A biosensor is an analytical system composed of biosensitive elements and signal-processing elements used to detect various biological and chemical substances. Biomimetic elements are key to biosensor technology and are the components in a sensor that are responsible for identifying the target analyte. The construction methods and working principles of biosensors based on synthetic biomimetic elements, such as DNAzyme, molecular imprinted polymers and aptamers, and their updated applications in biomedical analysis are summarised. Finally, the technical bottlenecks and future development prospects for biomedical analysis are summarised and discussed.

Aptamers: precision tools for diagnosing and treating infectious diseases

Infectious diseases represent a significant global health challenge, with bacteria, fungi, viruses, and parasitic protozoa being significant causative agents. The shared symptoms among diseases and the emergence of new pathogen variations make diagnosis and treatment complex. Conventional diagnostic methods are laborious and intricate, underscoring the need for rapid, accurate techniques. Aptamer-based technologies offer a promising solution, as they are cost-effective, sensitive, specific, and convenient for molecular disease diagnosis. Aptamers, which are single-stranded RNA or DNA sequences, serve as nucleotide equivalents of monoclonal antibodies, displaying high specificity and affinity for target molecules. They are structurally robust, allowing for long-term storage without substantial activity loss. Aptamers find applications in diverse fields such as drug screening, material science, and environmental monitoring. In biomedicine, they are extensively studied for biomarker detection, diagnostics, imaging, and targeted therapy. This comprehensive review focuses on the utility of aptamers in managing infectious diseases, particularly in the realms of diagnostics and therapeutics.

Carbon dots and covalent organic frameworks based FRET immunosensor for sensitive detection of Escherichia coli O157:H7

The combination of carbon dots (CDs) with covalent organic frameworks (COFs) was used to design an innovative sensor based on fluorescence resonance energy transfer (FRET) for the detection of Escherichia coli O157:H7 (E. coli O157:H7) in food samples. Carbon dots were used as fluorescence donors, covalent organic frameworks as fluorescence acceptors. The antibody (Ab) specific to E. coli O157:H7 was used to form a CD-Ab-COF immunosensor by linking CDs and COFs. The antibody was specifically bound with E. coli O157:H7, which caused the connection between CDs and COFs to be interrupted, and the carbon dots exhibited fluorescence restoration. The sensor exhibited a linear detection range spanning from 0 to 106 CFU/mL, with the limit of detection (LOD) of 7 CFU/mL. The analytical performance of the developed immunosensor was evaluated using spiked food samples with different concentrations of E. coli O157:H7, validating the capability of assessing risks in food testing.

Au-Pt Coating Improved Catalytic Stability of Au@AuPt Nanoparticles for Pressure-Based Point-of-Care Detection of Escherichia coli O157:H7

Point-of-care testing (POCT) technologies facilitate onsite detection of pathogens in minutes to hours. Among various POCT approaches, pressure-based sensors that utilize gas-generating reactions, particularly those catalyzed by nanozymes (e.g., platinum nanoparticles, PtNPs, or platinum-coated gold nanoparticles, and Au@PtNPs) have been shown to provide rapid and sensitive detection capabilities. The current study introduces Au-Pt alloy-coated gold nanoparticles (Au@AuPtNPs), an innovative nanozyme with enhanced catalytic activity and relatively high stability. For pathogen detection, Au@AuPtNPs are modified with H1 or H2 hairpin DNAs that can be triggered to undergo a hybridization chain reaction (HCR) that leads to their aggregation upon recognition by an initiator strand (Ini) with H1-/H2-complementary aptamers tethered to magnetic beads (MBs). Pathogen binding to the aptamer exposes Ini, which then binds Au@AuPtNPs and initiates a HCR, resulting in Au@AuPtNP aggregation on MBs. These Au@AuPtNP aggregates exhibit strong catalysis of O2 from the H2O2 substrate, which is measured by a pressure meter, enabling detection of Escherichia coli (E. coli) O157:H7 at concentrations as low as 3 CFU/mL with high specificity. Additionally, E. coli O157:H7 could also be detected in simulated water and tea samples. This method eliminates the need for costly, labor- and training-intensive instruments, supporting its further testing and validation for deployment as a rapid-response POCT application in the detection of bacterial contaminants.

Visual Loop-Mediated Isothermal Amplification (LAMP) Assay for Rapid On-Site Detection of Escherichia coli O157: H7 in Milk Products

(1) Background: Rapid on-site testing is an effective method for the detection of Escherichia coli O157: H7(E. coli O157: H7) in food ingredients and the environment. (2) Methods: In this study, we developed colorimetric loop-mediated isothermal amplification (LAMP) and immunochromatographic test strips (ICTs) for the rapid and visual detection of E. coli O157: H7. This study designed new specific LAMP primers for E. coli O157: H7 virulence island genes. After the LAMP amplification, the double-stranded DNA target sequence labeled with digoxin and fluorescein isothiocyanate (FITC) at both ends was bound to the anti-digoxin antibody on the gold nanoparticles. Subsequently, it was further bound to the anti-FITC antibody at the T line of the ICTs, forming a positive test result. Hydroxynaphthyl blue dye was directly added to the LAMP amplification product. A blue color indicated positive results, while a purple color indicated negative results. (3) Results: Two visualization methods showed high specificity for the target strains. The visualization tests had sensitivities of 5.7 CFU mL-1, and the detection limit of the Escherichia coli O157: H7 in artificially contaminated milk samples was 5.7 × 102 CFU mL-1, which was consistent with the results of the standard method (LAMP-electrophoresis method) used in commercial inspection. (4) Conclusions: Both methods could be useful in remote and under-resourced areas.

Recent advances in microfluidic-based spectroscopic approaches for pathogen detection

Rapid identification of pathogens with higher sensitivity and specificity plays a significant role in maintaining public health, environmental monitoring, controlling food quality, and clinical diagnostics. Different methods have been widely used in food testing laboratories, quality control departments in food companies, hospitals, and clinical settings to identify pathogens. Some limitations in current pathogens detection methods are time-consuming, expensive, and laborious sample preparation, making it unsuitable for rapid detection. Microfluidics has emerged as a promising technology for biosensing applications due to its ability to precisely manipulate small volumes of fluids. Microfluidics platforms combined with spectroscopic techniques are capable of developing miniaturized devices that can detect and quantify pathogenic samples. The review focuses on the advancements in microfluidic devices integrated with spectroscopic methods for detecting bacterial microbes over the past five years. The review is based on several spectroscopic techniques, including fluorescence detection, surface-enhanced Raman scattering, and dynamic light scattering methods coupled with microfluidic platforms. The key detection principles of different approaches were discussed and summarized. Finally, the future possible directions and challenges in microfluidic-based spectroscopy for isolating and detecting pathogens using the latest innovations were also discussed.

One-pot rapid visual detection of E. coli O157:H7 by label-free AuNP-based plasmonic-aptasensor in water sample

Access to clean water for irrigation and drinking has long been a global concern. The need for fast, precise, and cost-effective methods to detect harmful bacteria like Enterohemorrhagic Escherichia coli (EHEC) serotype O157:H7 is high due to the potential for severe infectious diseases. Fortunately, recent research has led to developing and utilizing rapid bacterial detection methods. The creation of an aptamer-based biosensor (aptasensor) for the detection of E. coli O157:H7 using label-free aptamers and gold nanoparticles (AuNPs) is described in this study. The specific aptamers that can detect target bacteria are adsorbed on the surface of unmodified AuNPs to form the aptasensor. The detection is performed by target bacterium-induced aptasensor aggregation, which is associated with a red-to-purple color change under high-salt circumstances. We devised a quick and easy method for detecting bacteria using an anti-E. coli O157:H7 aptamer without the need for specialized equipment or pretreatment processes like cell lysis. The aptasensor could identify target bacteria with only as few as 250 colony-forming units (CFU)/ml in 15 min or less, and its specificity based on our test was 100%. This method not only provides a fast direct preparation process but also exhibits remarkable proficiency in promptly identifying the intended target with a heightened level of sensitivity and specificity. Therefore, it can serve as an intelligent tool for monitoring water reservoirs and preventing the transmission of infectious diseases associated with EHEC.

Advances in signal amplification strategies applied in pathogenic bacteria apta-sensing analysis-A review

Pathogenic bacteria are primarily kinds of food hazards that provoke serious harm to human health via contaminated or spoiled food. Given that pathogenic bacteria continue to reproduce and expand once they contaminate food, pathogenic bacteria of high concentration triggers more serious losses and detriments. Hence, it is essential to detect low-dose pollution at an early stage with high sensitivity. Aptamers, also known as "chemical antibodies", are oligonucleotide sequences that have attracted much attention owing to their merits of non-toxicity, small size, variable structure as well as easy modification of functional group. Aptamer-based bioanalysis has occupied a critical position in the field of rapid detection of pathogenic bacteria. This is attributed to the unique advantage of using aptamers as recognition elements in signal amplification strategies. The signal amplification strategy is an effective means to improve the detection sensitivity. Some diverse signal amplification strategies emphasize the synthesis and assembly of nanomaterials with signal amplification capabilities, while others introduce various nucleic acid amplification techniques into the detection system. This review focuses on a variety of signal amplification strategies employed in aptamer-based detection approaches to pathogenic bacteria. Meanwhile, we provided a detailed introduction to the design principles and characteristics of signal amplification strategies, as well as the improvement of sensor sensitivity. Ultimately, the existing issues and development trends of applying signal amplification strategies in apta-sensing analysis of pathogenic bacteria are critically proposed and prospected. Overall, this review discusses from a new perspective and is expected to contribute to the further development of this field.

The Application of Hybridization Chain Reaction in the Detection of Foodborne Pathogens

Today, with the globalization of the food trade progressing, food safety continues to warrant widespread attention. Foodborne diseases caused by contaminated food, including foodborne pathogens, seriously threaten public health and the economy. This has led to the development of more sensitive and accurate methods for detecting pathogenic bacteria. Many signal amplification techniques have been used to improve the sensitivity of foodborne pathogen detection. Among them, hybridization chain reaction (HCR), an isothermal nucleic acid hybridization signal amplification technique, has received increasing attention due to its enzyme-free and isothermal characteristics, and pathogenic bacteria detection methods using HCR for signal amplification have experienced rapid development in the last five years. In this review, we first describe the development of detection technologies for food contaminants represented by pathogens and introduce the fundamental principles, classifications, and characteristics of HCR. Furthermore, we highlight the application of various biosensors based on HCR nucleic acid amplification technology in detecting foodborne pathogens. Lastly, we summarize and offer insights into the prospects of HCR technology and its application in pathogen detection.

Strategy of functional nucleic acids-mediated isothermal amplification for detection of foodborne microbial contaminants: A review

Foodborne microbial contamination (FMC) is the leading cause of food poisoning and foodborne illness. The foodborne microbial detection methods based on isothermal amplification have high sensitivity and short detection time, and functional nucleic acids (FNAs) could extend the detectable object of isothermal amplification to mycotoxins. Therefore, the strategy of FNAs-mediated isothermal amplification has been emergingly applied in biosensors for foodborne microbial contaminants detection, making biosensors more sensitive with lower cost and less dependent on nanomaterials for signal output. Here, the mechanism of six isothermal amplification technologies and their application in detecting FMC is firstly introduced. Then the strategy of FNAs-mediated isothermal amplification is systematically discussed from perspectives of FNAs' versatility including recognition elements (Aptamer, DNAzyme), programming tools (DNA tweezer, DNA walker and CRISPR-Cas) and signal units (G-quadruplex, FNAs-based nanomaterials). Finally, challenges and prospects are presented in terms of addressing the issue of nonspecific amplification reaction, developing better FNAs-based sensing elements and eliminating food matrix effects.

Sensor integration into microfluidic systems: trends and challenges

The combination of sensors and microfluidics has become a promising approach for detecting a wide variety of targets relevant in biotechnology. Thanks to recent advances in the manufacturing of microfluidic systems, microfluidics can be manufactured faster, cheaper, and more accurately than ever before. These advances make microfluidic systems very appealing as a basis for constructing sensor systems, and microfluidic devices have been adapted to house (bio)sensors for various applications (e.g. protein biomarker detection, cell culture oxygen control, and pathogen detection). This review article highlights several successfully integrated microfluidic sensor systems, with a focus on work that has been published within the last two years. Different sensor integration methods are discussed, and the latest trends in wearable- and smartphone-based sensors are described.

Nanozyme-Mediated Catalytic Signal Amplification for Microfluidic Biosensing of Foodborne Bacteria

Early detection of foodborne bacteria is urgently needed to ensure food quality and to avoid the outbreak of foodborne bacterial diseases. Here, a kind of metal-organic framework (Zr-MOF) modified with Pt nanoparticles (Pt-PCN-224) was designed as a peroxidase-like signal amplifier for microfluidic biosensing of foodborne bacteria. Taking Escherichia coli (E. coli) O157:H7 as a model, a linear range from 2.93 × 102 to 2.93 × 108 CFU/mL and a limit of detection of 2 CFU/mL were obtained. The whole detection procedure was integrated into a single microfluidic chip. Water, milk, and cabbage samples were successfully detected, showing consistency with the results of the standard culture method. Recoveries were in the range from 90 to 110% in spiked testing. The proposed microfluidic biosensor realized the specific and sensitive detection of E. coli O157:H7 within 1 h, implying broad prospects of MOF with biomimetic enzyme activities for biosensing.

Point-of-Care Diagnostic Devices for Detection of Escherichia coli O157:H7 Using Microfluidic Systems: A Focused Review

Bacterial infections represent a serious and global threat in modern medicine; thus, it is very important to rapidly detect pathogenic bacteria, such as Escherichia coli (E. coli) O157:H7. Once treatments are delayed after the commencement of symptoms, the patient's health quickly deteriorates. Hence, real-time detection and monitoring of infectious agents are highly critical in early diagnosis for correct treatment and safeguarding public health. To detect these pathogenic bacteria, many approaches have been applied by the biosensors community, for example, widely-used polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA), culture-based method, and adenosine triphosphate (ATP) bioluminescence. However, these approaches have drawbacks, such as time-consumption, expensive equipment, and being labor-intensive, making it critical to develop ultra-sensitive and highly selective detection. The microfluidic platform based on surface plasmon resonance (SPR), electrochemical sensing, and rolling circle amplification (RCA) offers proper alternatives capable of supplementing the technological gap for pathogen detection. Note that the microfluidic biochip allows to develop rapid, sensitive, portable, and point-of-care (POC) diagnostic tools. This review focuses on recent studies regarding accurate and rapid detection of E. coli O157:H7, with an emphasis on POC methods and devices that complement microfluidic systems. We also examine the efficient whole-body detection by employing antimicrobial peptides (AMPs), which has attracted growing attention in many applications.

Nanostructured biosensing platforms for the detection of food- and water-borne pathogenic Escherichia coli

Pathogenic bacterial infection is one of the principal causes affecting human health and ecosystems. The accurate identification of bacteria in food and water samples is of significant interests to maintain safety and health for humans. Culture-based tests are practically tedious and may produce false-positive results, while viable but non-culturable microorganisms (NCMs) cannot be retrieved. Thus, it requires fast, reliable, and low-cost detection strategies for on-field analysis and point-of-care (POC) monitoring. The standard detection methods such as nucleic acid analysis (RT-PCR) and enzyme-linked immunosorbent assays (ELISA) are still challenging in POC practice due to their time-consuming (several hours to days) and expensive laboratory operations. The optical (surface plasmon resonance (SPR), fluorescence, and surface-enhanced Raman scattering (SERS)) and electrochemical-based detection of microbes (early stage of infective diseases) have been considered as alternative routes in the emerging world of nanostructured biosensing since they can attain a faster and concurrent screening of several pathogens in real samples. Moreover, optical and electrochemical detection strategies are opening a new route for the ability of detecting pathogens through the integration of cellphones, which is well fitted for POC analysis. This review article covers the current state of sensitive mechanistic approaches for the screening and detection of Escherichia coli O157:H7 (E. coli) pathogens in food and water samples, which can be potentially applied in clinical and environmental monitoring.

A point-of-care detection platform for Escherichia coli O157:H7 by integration of smartphone and the structural colour of photonic microsphere

A smartphone-based sensitive, rapid, label-free and high-throughput detection platform for Escherichia coli O157:H7 was established. The specific recognition capability of this platform was dependent of the aptamer modified on the silica photonic microsphere (SPM), whose structural colour was utilized for the quantification of the target bacterium. Gold nanoparticles and silver staining technique were employed to improve the sensitivity of the detection platform. Such smartphone-based detection platform gave a wide linear detection range of 10² ∼ 10⁸ CFU/mL with a low limit of detection (LOD) of 68 CFU/mL and high specificity for Escherichia coli O157:H7. Moreover, the recovery rates of the detection method were measured in the range of 99 ∼ 108% in the milk, pork and purified water samples. Furthermore, the developed detection platform did not require complex sample pretreatment and could be easily manipulated, displaying great application potential in the fields of food safety, environmental monitoring and disease diagnosis.

An instrument-free visual quantitative detection method based on clock reaction: the detection of thrombin as an example

Instrument-free visual quantitative detection in chemical and biochemical analysis is of great significance in practical applications especially in point-of-care testing and in places where resources are limited. In this paper, we report the development of a time-based instrument-free visual quantitative detection method by employing a clock reaction, a type of chemical reaction displaying characteristic clocking behavior. The feasibility of the method was illustrated by the quantitative detection of thrombin in buffer solution using the lapse of time as the readout signal. The linear range of detection was from 1.3 to 43 nM (r² = 0.990, n = 3) with a LOD of 0.9 nM, which is lower than the physiological concentrations of thrombin in the resting and activated blood, which range from low nanomolar to low micromolar, respectively. This method was also validated by detecting thrombin in the serum and a good recovery of nearly 100 ± 8.0% was obtained. To the best of our knowledge, this work is the first report that uses the characteristic time of a clock reaction as the readout signal in instrument-free colorimetry for quantitative bioanalysis.

Nucleic acid amplification-based strategy to detect foodborne pathogens in milk: a review

Milk contaminated with trace amounts of foodborne pathogens can considerably threaten food safety and public health. Therefore, rapid and accurate detection techniques for foodborne pathogens in milk are essential. Nucleic acid amplification (NAA)-based strategies are widely used to detect foodborne pathogens in milk. This review article covers the mechanisms of the NAA-based detection of foodborne pathogens in milk, including polymerase chain reaction (PCR), loop-mediated isothermal amplification (LAMP), recombinase polymerase amplification (RPA), rolling circle amplification (RCA), and enzyme-free amplification, among others. Key factors affecting detection efficiency and the advantages and disadvantages of the above techniques are analyzed. Potential on-site detection tools based on NAA are outlined. We found that NAA-based strategies were effective in detecting foodborne pathogens in milk. Among them, PCR was the most reliable. LAMP showed high specificity, whereas RPA and RCA were most suitable for on-site and in-situ detection, respectively, and enzyme-free amplification was more economical. However, factors such as sample separation, nucleic acid target conversion, and signal transduction affected efficiency of NAA-based strategies. The lack of simple and effective sample separation methods to reduce the effect of milk matrices on detection efficiency was noteworthy. Further research should focus on simplifying, integrating, and miniaturizing microfluidic on-site detection platforms.

Colorimetric Systems for the Detection of Bacterial Contamination: Strategy and Applications

Bacterial contamination is a public health concern worldwide causing enormous social and economic losses. For early diagnosis and adequate management to prevent or treat pathogen-related illnesses, extensive effort has been put into the development of pathogenic bacterial detection systems. Colorimetric sensing systems have attracted increasing attention due to their simple and single-site operation, rapid signal readout with the naked eye, ability to operate without external instruments, portability, compact design, and low cost. In this article, recent trends and advances in colorimetric systems for the detection and monitoring of bacterial contamination are reviewed. This article focuses on pathogen detection strategies and technologies based on reaction factors that affect the color change for visual readout. Reactions used in each strategy are introduced by dividing them into the following five categories: external pH change-induced pH indicator reactions, intracellular enzyme-catalyzed chromogenic reactions, enzyme-like nanoparticle (NP)-catalyzed substrate reactions, NP aggregation-based reactions, and NP accumulation-based reactions. Some recently developed colorimetric systems are introduced, and their challenges and strategies to improve the sensing performance are discussed.

Aptasensor Based on Microfluidic for Foodborne Pathogenic Bacteria and Virus Detection: A Review

In today's world, which is entangled with numerous foodborne pathogenic bacteria and viruses, it appears to be essential to rethink detection methods of these due to the importance of food safety in our lives. The vast majority of detection methods for foodborne pathogenic bacteria and viruses have suffered from sensitivity and selectivity due to the small size of these pathogens. Besides, these types of sensing approaches can improve on-site detection platforms in the fields of food safety. In recent, microfluidics systems as new emerging types of portable sensing approaches can introduce efficient and simple biodevice by integration with several analytical methods such as electrochemical, optical and colorimetric techniques. Additionally, taking advantage of aptamer as a selective bioreceptor in the sensing of microfluidics system has provided selective, sensitive, portable and affordable sensing approaches. Furthermore, some papers use increased data transferability ability and computational power of these sensing platforms by exploiting smartphones. In this review, we attempted to provide an overview of the current state of the recent aptasensor based on microfluidic for screening of foodborne pathogenic bacteria and viruses. Working strategies, benefits and disadvantages of these sensing approaches are briefly discussed.

Bioinspired fabrication of bifunctional antibody-enzyme co-assembled nanocomposites for chemiluminescence immunoassays of E. coli O157:H7

Immunoassays based on enzyme-labeled antibodies have been widely used in the food safety field. However, the production process of enzyme-labeled antibodies is complicated and the low storage stability limits their application. Herein, antibody-horseradish peroxidase (HRP) co-assembled nanocomposites (AHC NCs) with outstanding advantages such as enhanced stability, lower cost, and substrate affinity were successfully prepared via a one-pot green method. Then the AHC NCs were employed as an alternative to traditional enzyme-labeled antibodies to develop a chemiluminescence enzyme immunoassay (CLEIA) toward Escherichia coli (E. coli) O157:H7. Under optimal conditions, E. coli O157:H7 can be detected in a linear range from 1 × 10³ CFU mL^-1 to 5 × 10⁶ CFU mL^-1, while the limit of detection (LOD) is as low as 2.2 × 10² CFU mL^-1 (3σ). A series of repeatability studies showed reproducible results with a coefficient of variation of less than 7%. In addition, the proposed CLEIA was successfully applied to the analysis of spiked samples (tap water) and gave quantitative recoveries from 93.72% to 100.72%. This work demonstrates that the developed CLEIA can be applied as a universal platform for specific detection of diversified analytes.

Recent Advances in Microfluidic Devices for Contamination Detection and Quality Inspection of Milk

Milk is a necessity for human life. However, it is susceptible to contamination and adulteration. Microfluidic analysis devices have attracted significant attention for the high-throughput quality inspection and contaminant analysis of milk samples in recent years. This review describes the major proposals presented in the literature for the pretreatment, contaminant detection, and quality inspection of milk samples using microfluidic lab-on-a-chip and lab-on-paper platforms in the past five years. The review focuses on the sample separation, sample extraction, and sample preconcentration/amplification steps of the pretreatment process and the determination of aflatoxins, antibiotics, drugs, melamine, and foodborne pathogens in the detection process. Recent proposals for the general quality inspection of milk samples, including the viscosity and presence of adulteration, are also discussed. The review concludes with a brief perspective on the challenges facing the future development of microfluidic devices for the analysis of milk samples in the coming years.

Recent Advances in Aptamer Sensors

Recently, aptamers have attracted attention in the biosensing field as signal recognition elements because of their high binding affinity toward specific targets such as proteins, cells, small molecules, and even metal ions, antibodies for which are difficult to obtain. Aptamers are single oligonucleotides generated by in vitro selection mechanisms via the systematic evolution of ligand exponential enrichment (SELEX) process. In addition to their high binding affinity, aptamers can be easily functionalized and engineered, providing several signaling modes such as colorimetric, fluorometric, and electrochemical, in what are known as aptasensors. In this review, recent advances in aptasensors as powerful biosensor probes that could be used in different fields, including environmental monitoring, clinical diagnosis, and drug monitoring, are described. Advances in aptamer-based colorimetric, fluorometric, and electrochemical aptasensing with their advantages and disadvantages are summarized and critically discussed. Additionally, future prospects are pointed out to facilitate the development of aptasensor technology for different targets.