SERS aptasensor for simultaneous detection of ochratoxin A and zearalenone utilizing a rigid enhanced substrate (ITO/AuNPs/GO) combined with Au@AgNPs.

The contamination of mycotoxins poses a serious threat to global food security, hence the urgent need for simultaneous detection of multiple mycotoxins. Herein, two SERS nanoprobes were synthesized by embedded SERS tags (4-mercaptopyridine, 4MPy; 4-mercaptobenzonitrile, TBN) into the Au and Ag core-shell structure, and each was coupled with the aptamers specific to ochratoxin A (OTA) and zearalenone (ZEN). Meanwhile, a rigid enhanced substrate Indium tin oxide glass/AuNPs/Graphene oxide (ITO/AuNPs/GO) was combined with aptamer functionalized Au@AgNPs via π-π stacking interactions between the aptamer and GO to construct a surface-enhanced Raman spectroscopy (SERS) aptasensor, thereby inducing a SERS enhancement effect for the effective and swift simultaneous detection of both OTA and ZEN. The presence of OTA and ZEN caused signal probes dissociation, resulting in an inverse correlation between Raman signal intensity (1005 cm-1 and 2227 cm-1) and the concentrations of OTA and ZEN, respectively. The SERS aptasensor exhibited wide linear detection ranges of 0.001-20 ng/mL for OTA and 0.1-100 ng/mL for ZEN, with low detection limits (LOD) of 0.94 pg/mL for OTA and 59 pg/mL for ZEN. Furthermore, the developed SERS aptasensor demonstrated feasible applicability in the detection of OTA and ZEN in maize, showcasing its substantial potential for practical implementation.

Plasmon-enhanced fluorescence and electrochemical aptasensor for SARS-CoV-2 Spike protein detection.

In this work, we combined plasmon-enhanced fluorescence and electrochemical (PEF-EC) transduction mechanisms to realize a highly sensitive dual-transducer aptasensor. To implement two traducers in one biosensor, a novel large-scale nanoimprint lithography process was introduced to fabricate gold nanopit arrays (AuNpA) with unique fringe structures. Light transmitting through the AuNpA samples exhibited a surface plasmon polariton peak overlapping with the excitation peak of the C7 aptamer-associated fluorophore methylene blue (MB). We observed a five and seven-times higher average fluorescence intensity over the AuNpA and fringe structure, respectively, in comparison to a plane Au film. Furthermore, the MB fluorophore was simultaneously utilized as a redox probe for electrochemical investigations and is described here as a dual transduction label for the first time. The novel dual transducer system was deployed for the detection of SARS-CoV-2 Spike protein via a C7 aptamer in combination with a strand displacement protocol. The PEF transducer exhibited a detection range from 1 fg/mL to 10 ng/mL with a detection limit of 0.07 fg/mL, while the EC traducer showed an extended dynamic range from 1 fg/mL to 100 ng/mL with a detection limit of 0.15 fg/mL. This work provides insights into an easy-to-perform, large-scale fabrication process for nanostructures enabling plasmon-enhanced fluorescence, and the development of an advanced but universal aptasensor platform.

Synthesis of SnC@Au@Apta by electrospinning as an electrochemical sensor for detection of tetracycline.

A highly efficient electrochemical aptamer sensor for the detection of tetracycline (TC) was prepared by using SnC@Au@Apta. Metal tin has good electrochemical activity and high conductivity. It is often used as an electrochemical sensing material. The nanofibers prepared by electrospinning machine make the metal distribution more uniform, not easy to agglomerate, and have a certain porosity, which can improve the sensitivity of sensor detection. Carbonization further enhances conductivity. The gold nanoparticles (AuNPs) on the surface of SnC nanomaterials improve the electrochemical detection performance, and also act as the binding site of the TC aptamer, which is stably combined with the thiol group at the end of the TC aptamer. The TC aptamer specifically binds to TC to detect TC in the sample. The electrochemical performance of SnC@Au@Apta was evaluated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under the optimal conditions, the detection range of SnC@Au@Apta is wide (0.001-100 µM), the detection limit is low (0.83 nM), and it has excellent selectivity, stability and reproducibility. In addition, SnC@Au@Apta can be used to detect TC in milk samples.

Label-free SELEX of aptamers for ultra-sensitive electrochemical aptasensor detection of amanitin in wild mushrooms.

BACKGROUND: Mushroom poisoning poses a significant global health concern, with high morbidity and mortality rates. The primary lethal toxins responsible for this condition are alpha-amanitin (ɑ-AMA) and beta-amanitin (ß-AMA). As a promising bio-recognition molecules in biosensors, aptamers, have been broadly used in the field of food detection. However, the current SELEX-based methods for screening aptamers for structurally similar small molecules were limited by the labelling or salt ion induction. In this study, we aimed to develop a novel label-free SELEX strategy for the screening of aptamers with high affinity and constructed new aptasensors for the detection of ɑ-AMA and ß-AMA. RESULTS: A novel label-free SELEX strategy based on the positively charged gold nanoparticles (AuNPs) was proposed to simultaneous screening of aptamers for ɑ-AMA and ß-AMA. Only 18 rounds of SELEX were required to obtain new aptamers. The candidate aptamers were analyzed by colloidal gold assay, and the sequences of ɑ-30 and ß-37 displayed great affinity with Kd values of 22.26 nM and 23.32 nM, respectively, without interference from botanical toxins. Notably, the truncated aptamers ɑ-30-2 (50 bp) and ß-37-2 (57 bp) exhibited higher affinity than their original counterpart (79 bp). Subsequently, the selected aptamers were utilized to construct recognition probes for electrochemical aptasensors based on hairpin cyclic cleavage of substrates by Cu2+ dependent DNAzyme and Exo I-triggered recycling cascades. The detection platform showed excellent analytical performance with limits of detection as low as 4.57 pg/mL (ɑ-AMA) and 8.49 pg/mL (ß-AMA). Moreover, the aptasensors exhibited superior performance in mushroom and urine samples. SIGNIFICANCE: This work developed a simple and efficient label-free SELEX method for screening new aptamers for ɑ-AMA and ß-AMA, which employed the positively charged AuNPs as the screening medium, without the need for chemical labelling of libraries or induction of salt ions. Furthermore, two novel electrochemical aptasensors were developed based on our newly obtained aptamers, which offer the new biosensing tool for ultrasensitive detection of the AMA poisoning, showing great potential in practical applications.

A Surface-Enhanced Raman Spectroscopy-Based Aptasensor for the Detection of Deoxynivalenol and T-2 Mycotoxins.

The quality of food is one of the emergent points worldwide. Many microorganisms produce toxins that are harmful for human and animal health. In particular, mycotoxins from Fusarium fungi are strictly controlled in cereals. Simple and robust biosensors are necessary for 'in field' control of the crops and processed products. Nucleic acid-based sensors (aptasensors) offer a new era of point-of-care devices with excellent stability and limits of detection for a variety of analytes. Here we report the development of a surface-enhanced Raman spectroscopy (SERS)-based aptasensor for the detection of T-2 and deoxynivalenol in wheat grains. The aptasensor was able to detect as low as 0.17% of pathogen fungi in the wheat grains. The portable devices, inexpensive SERS substrate, and short analysis time encourage further implementation of the aptasensors outside of highly equipped laboratories.

A signal-on photoelectrochemical aptasensor based on WO3/CdS heterojunction for the ultrasensitive detection of kanamycin.

In this study, a signal-on photoelectrochemical (PEC) aptasensor for the ultrasensitive determination of kanamycin (KANA) was constructed using WO3/CdS heterojunction as photoactive material. Firstly, WO3/CdS heterojunction with excellent photoelectric response was successfully prepared by simple co-precipitation method, resulting in a strong and stable initial photocurrent. In addition, amino modified aptamers were immobilized on the electrode surface by glutaraldehyde as biological recognition components. In the presence of the target KANA, it is specifically recognized and captured by the aptamers. More importantly, KANA can act as a signal amplifier to enhance the photocurrent due to the oxidation of KANA by photogenerated holes. Therefore, a signal-on PEC aptasensor based on WO3/CdS heterojunction with high selectivity was obtained for the detection of KANA. Under optimized experimental conditions, the PEC aptasensor demonstrated a wide linear range of 10 pM to 400 nM, with a detection limit of 6.77 pM. Meanwhile, the designed PEC aptasensor had been successfully utilized for the analytical examination of milk, fish, serum, and water samples.

Tetrodotoxin and the state-of-the-art progress of its associated analytical methods.

Tetrodotoxin (TTX), which is found in various marine organisms, including pufferfish, shellfish, shrimp, crab, marine gastropods, and gobies, is an effective marine toxin and the cause of many seafood poisoning incidents. Owing to its toxicity and threat to public health, the development of simple, rapid, and efficient analytical methods to detect TTX in various food matrices has garnered increasing interest worldwide. Herein, we reviewed the structure and properties, origin and sources, toxicity and poisoning, and relevant legislative measures of TTX. Additionally, we have mainly reviewed the state-of-the-art progress of analytical methods for TTX detection in the past five years, such as bioassays, immunoassays, instrumental analysis, and biosensors, and summarized their advantages and limitations. Furthermore, this review provides an in-depth discussion of the most advanced biosensors, including cell-based biosensors, immunosensors, and aptasensors. Overall, this study provides useful insights into the future development and wide application of biosensors for TTX detection.

PolyPyrrole based-impedimetric aptasensor for selective determination of beta-HCG from urine sample.

Herein, a conjugated conducting polymer-based impedimetric aptasensor has been developed to detect beta-human chorionic gonadotropin (bHCG), the one of the important biomarkers in gynecology, from synthetic human urine samples. In this context, gold electrodes were, firstly coated with pyrrole and pyrrole-3-carboxylic acid to obtain the poly(pyrrole-pyrrole-3-carboxylic acid) [poly(Py-PyCOOH)] conductive copolymer by cyclic voltammetry (CV). Then, bHCG-specific peptide aptamer was covalently linked onto the surface via applying a well-known carbodiimide-succinimide chemistry. The sensor developed was characterized to confirm modification steps via both electrochemical methods including CV, electrochemical impedance spectroscopy (EIS), and chronoamperometry and physico-chemically via attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), atomic force microscope (AFM), and contact angle measurements (CA). The analytical performance of the sensor was evaluated in the concentration range from 1 µg/mL to 100 µg/mL for successful detection of bHCG even in the presence of interference agents. The results have also revealed that the sensor could be classified as a promising alternative to its benchmark commercial clinical methods due its superior properties such as cost-friendliness, easy-to-prepare, stable, robust, and selectivity / sensitivity.

An easy-operation aptasensor for simultaneous detection of multiple tumor-associated exosomal proteins based on multicolor fluorescent DNA nanoassemblies.

As a promising liquid biopsy biomarker, exosomes have demonstrated great potential and advantages in the noninvasive tumor diagnosis. However, an accurate and sensitive method for tumors-associated exosomes detection is scarce. Herein, we presented an easy-operation aptasensor which simultaneously detect multiple exosomal proteins by using multicolor fluorescent DNA nanoassemblies (FDNs) and CD63 aptamer-modified magnetic beads (MNPs-AptCD63). In this system, the FDNs were firstly constructed by encapsulating different quantum dots (QDs) into rolling circle amplification (RCA) products that contained different aptamer sequences. Thus, the FDNs could selectively recognize the different exosomal proteins captured by the MNPs-AptCD63, and achieve the multiplex and sensitive detection according to the fluorescence of QDs. Benefiting from the signal amplification capacity and high selectivity of FDNs, this aptasensor not only could detect exosomes as low as 650 particles/µL, but also showed accurate analysis in clinical samples. In addition, we can also achieve point-of-care testing (POCT) due to the simple analysis steps and naked-eye observable fluorescence of QDs under the ultraviolet irradiation. We believe that our aptasensor could provide a promising platform for exosomes-based personalized diagnosis and precise monitoring of human health.

Double hook-type aptamer-based colorimetric and electrochemical biosensor enables rapid and robust analysis of EpCAM expression.

Epithelial cell adhesion molecule (EpCAM), which is overexpressed in breast cancer cells and participates in cell signaling, migration, proliferation, and differentiation, has been utilized as a biomarker for cancer diagnosis and therapeutic prognosis. Here, a dual-signal readout nonenzymatic aptasensor is fabricated for the evaluation of EpCAM at the level of three breast cancer cell lines. The central principle of this enzyme-free aptasensor is the use of double hook-type aptamers (SYL3C and SJ3C2)-functionalized magnetic iron oxide (Fe3O4) as capture probes and quasi-CoFe prussian blue analogs (QCoFe PBAs) as nonenzymatic signal probes for colorimetric and electrochemical analysis. Following ligand detachment, the CoFe PBA was transformed to QCoFe PBA (calcined at 350 °C for 1 h), with its metal active sites exposed by controllable pyrolysis. We found that the enhanced sensitivity was attributed to the resonance effect of QCoFe PBA with the remarkable enzymatic properties. The dual-signal readout nonenzymatic aptasensor exhibited limits of detection for EpCAM as low as 0.89 pg mL-1 and 0.24 pg mL-1, within a wide linear range from 0.001 to 100 ng mL-1, respectively. We successfully employed this nonenzymatic aptasensor for monitoring EpCAM expression in three breast cancer cell lines, which provides an economical and robust alternative to costly and empirical flow cytometry. The dual-signal readout nonenzymatic aptasensor provides rapid, robust, and promising technological support for the accurate management of tumors.

Electrochemical Aptasensor with Antifouling Properties for Label-Free Detection of Oxytetracycline.

Oxytetracycline (OTC) is a widely employed antibiotic in veterinary treatment and in the prevention of infections, potentially leaving residues in animal-derived food products, such as milk, that are consumed by humans. Given the detrimental effects of prolonged human exposure to antibiotics, it has become imperative to develop precise and sensitive methods for monitoring the presence of OTC in food. Herein, we describe the development and results of a preliminary label-free electrochemical aptasensor with antifouling properties designed to detect OTC in milk samples. The sensor was realized by modifying a gold screen-printed electrode with α-lipoic acid-NHS and an amine-terminated aptamer. Different electrochemical techniques were used to study the steps of the fabrication process and to quantify OTC in the presence of the Fe(CN)64-/Fe(CN)63- redox couple The detectable range of concentrations satisfy the maximum residue limits set by the European Union, with an limit of detection (LOD) of 14 ng/mL in phosphate buffer (BP) and 10 ng/mL in the milk matrix, and a dynamic range of up to 500 ng/mL This study is a steppingstone towards the implementation of a sensitive monitoring method for OTC in dairy products.

Novel electrochemiluminescence platform utilizing AuNPs@Uio-66-NH2 bridged luminescent substrates and aptamers for the detection of pesticide residues in Chinese herbal medicines.

A large number of Chinese herbal medicines (CHMs) are included in daily recipes, but their pesticide residues have aroused more and more concerns. In this paper, an electrochemiluminescence aptasensor was constructed for the trace detection of acetamiprid (ACE) in Angelica sinensis and Lycium barbarum. Possessing a large specific surface area, UiO-66 was modified with amino groups to improve biocompatibility, and the addition of AuNPs allowed UiO-66-NH2 to catalyze the formation of excited states of luminescent molecules (TPrA⁎; Ru(bpy)32+⁎), and AuNPs@UiO-66-NH2 was used to bridge the aptamer (Au-S) and luminescent substrate (peptide bond). The conventional luminescent reagent Ru(bpy)32+ was doped with multi-walled carbon nanotubes (MWCNTs) to obtain a more powerful and stable light signal. After optimizing the experimental parameters, the aptasensor could give results in 10 min with a detection range from 1×10-2-1×104 nM and a lower limit of detection (LOD) of 0.8 pM. The LOD of the study was at least one order of magnitude lower than that of the fluorescence detection method. Furthermore, the accuracy of the aptasensor was validated for spiked recovery experiments.

Advancements in SERS based systematic evolution of ligands by exponential enrichment for detection of pesticide residues in fruits and vegetables.

Fruits and vegetables with pesticide residues pose a serious public health risk. Since 2022, 3 million people worldwide have been poisoned by pesticides annually, with a 20 % fatality rate. This review provides an overview of current research on detecting pesticide residues in produce, focusing on the potential of SERS-based aptasensor. These sensors offer improved efficiency and accuracy in pesticide analysis, ensuring the safety of fruits and vegetables. The review also discusses essential techniques for efficient aptamer production, highlighting their advantages and disadvantages. It emphasizes the benefits and challenges of using SERS-based aptasensor, particularly the need for enhanced anti-interference capabilities and the development of intelligent sensors for on-site detection without extensive sample preparation. This comprehensive review is a great resource that can help with future developments in pesticide residue analysis, food safety, and consumer health protection in contemporary agriculture.

High sensitive aptasensing chronic myeloid leukemia on circular electrode-modified by single-walled carbon nanotube.

Chronic myeloid leukemia (CML) is a cancer in the bone marrow caused by the proliferation of granulocyte cells at all the maturation stages. Late diagnosis of CML decreases the patient survival rate, makes diagnosing CML is mandatory before entering the blastic phase. CD 19 is an important target for CML and is effectively utilized for therapeutic and diagnosis purposes. This research was focused on developing an aptamer-mediated circular interdigitated electrode (IDE) sensor for detecting the level of CD 19 and measured at 0-2 V with the step of 0.1 V. To improve the surface functionalization on IDE, the surface of IDE was modified with a single-walled carbon nanotube (SWCN) to enhance the aptamer immobilization. SWCN increased the aptamer attachment and also enhanced the analytical performances on IDE. This SWCN-aptamer modified IDE detected the CD 19 as low as 10 nM on a linear co-regression range from 10 to 100 nM [y = 2.0126x - 2.3857; R2 = 0.9749]. Furthermore, control performances with CD 33, and complementary aptamer did not show the increment of current, and CD 19 spiked human serum increased the current flow without significant interference, demonstrating the specific and selective detection of CD 19. This biosensor quantifies CD 19 biomarker at its lower level and diagnoses CML and its associated complications.

Advancements in Chronic Myeloid Leukemia detection: Development and evaluation of a novel QCM aptasensor for use in clinical practice.

Oncological diseases represent a significant global health challenge, with high mortality rates. Early detection is crucial for effective treatment, and aptamers, which demonstrate superior specificity and stability compared to antibodies, offer a promising avenue for diagnostic advancement. This study presents the design, development and evaluation of a quartz crystal microbalance (QCM) sensor functionalized with the T2-KK1B10 aptamer for the sensitive and specific detection of Chronic Myeloid Leukemia (CML) K562 cells. The research focuses on optimizing the biorecognition layer by adjusting the aptamer conditions, demonstrating the sensor's ability to detect these CML cells with high specificity and sensitivity. The aptamer-modified QCM sensor operates on the principle of mass change detection upon binding of target cells. By employing the Langmuir isotherm model, the performance of the sensor was optimized for the capture of CML cells from biological samples with LOD of 263 K562 cells. The sensor was also successfully regenerated multiple times without sensitivity loss. Validation of the sensor's performance was conducted under controlled laboratory settings, followed by extensive testing utilizing human lyophilized plasma and clinical samples from patients. The sensor exhibited high sensitivity and specificity in the detection of CML cells within clinical specimens, thereby illustrating its potential for practical clinical deployment. This research presents a novel approach to the early diagnosis of CML, facilitating timely intervention and enhanced patient outcomes. The developed aptasensor demonstrates potential for broader application in cancer diagnostics and personalized medicine.

Perylene Diimide-based Fluorescent Aptasensor for Quantitative Analysis of Pb2+ Based on Terminal Deoxynucleotidyl Transferase-assisted Formation of Elongated Aptamer and Gold Nanoparticles.

Due to the exceedingly poisonous properties of Pb2+, it is imperative to conduct a thorough assessment of its quantity in both biological and environmental samples, as this is crucial for safeguarding public health. This study describes an economic turn-off fluorescent aptasensor for the quantitative analysis of Pb2+ employing 3,4,9,10-perylenetetracarboxylic acid diimide (PTCDI) as a cost-effective fluorophore, gold nanoparticles (AuNPs) as separating agent and an elongated aptamer as both targeting agent and PTCDI loading site. The fundamental principle of the suggested fluorescent aptasensor, which is based on PTCDI, relies on detecting variations in the fluorescence intensity of PTCDI when an elongated aptamer (as single-stranded DNA) is present or absent. The advanced aptasensor is advantageous due to the elongation of the lead aptamer sequence length induced by terminal deoxynucleotidyl transferase (TdT), resulting in enhanced sensitivity. The presence of Pb2+ and the centrifugation process causes the separation of the poly A-modified aptamer/Pb2+ conjugate from the poly T sequence. Hence, the interaction of PTCDI with the poly A moiety in the modified aptamer leads to a decrease in its fluorescence emission. The findings showcased that the fluorescent aptasensor exhibited exceptional specificity towards Pb2+ ions, while the biosensing platform accomplished an impressive detection limit of 3.7 pM. Moreover, the suggested aptasensor utilizing PTCDI exhibits a commendable capability in quantitatively analyzing Pb2+ within human serum samples and mineral water.

Comparative Analysis of QCM and Electrochemical Aptasensors for SARS-CoV-2 Detection.

The rapid and accurate detection of SARS-CoV-2, particularly its spike receptor-binding domain (S-RBD), was crucial for managing the COVID-19 pandemic. This study presents the development and optimization of two types of aptasensors: quartz crystal microbalance (QCM) and electrochemical sensors, both employing thiol-modified DNA aptamers for S-RBD detection. The QCM aptasensor demonstrated exceptional sensitivity, achieved by optimizing aptamer concentration, buffer composition, and pre-treatment conditions, with a limit of detection (LOD) of 0.07 pg/mL and a linear range from 1 pg/mL to 0.1 µg/mL, and a significant frequency change was observed upon target binding. The electrochemical aptasensor, designed for rapid and efficient preparation, utilized a one-step modification process that reduced the preparation time to 2 h while maintaining high sensitivity and specificity. Electrochemical impedance spectroscopy (EIS) enabled the detection of S-RBD concentrations as low as 132 ng/mL. Both sensors exhibited high specificity, with negligible non-specific interactions observed in the presence of competing proteins. Additionally, the QCM aptasensor's functionality and stability were verified in biological fluids, indicating its potential for real-world applications. This study highlights the comparative advantages of QCM and electrochemical aptasensors in terms of preparation time, sensitivity, and specificity, offering valuable insights for the development of rapid, sensitive, and specific diagnostic tools for the detection of SARS-CoV-2 and other viruses.

An ultrasensitive and specific fluorescence split-aptasensor for VEGF165 detection based on nicking enzyme-assisted 3D DNA walker coupling with CRISPR-Cas12a.

The overexpression of vascular endothelial growth factor 165 (VEGF165) in cancer cells plays a pivotal role in promoting tumor metastasis by facilitating their excessively rapid proliferation and division. Hence, the development of analytical methods possessing high sensitivity and resistance to interference is imperative for the detection of VEGF165. Various types of aptasensors have been devised for VEGF165 detection; however, the performance of these biosensors can be influenced by non-target signals caused by conformational changes in unbound aptamers. The paper shows the creation of a precise and sensitive fluorescence biosensor designed to detect VEGF165 by using a VEGF165-specific split aptamer. Additionally, this biosensor employs nicking enzyme-assisted DNA walker coupling with CRISPR-Cas12a to achieve dual-signal amplification. The VEGF165 calibration curve shows a detection limit of 268 fM and has a broad linear range from 5 to 4000 nM. The fluorometric biosensor was utilized to detect VEGF165 in human serum and cellular homogenate samples, yielding good outcomes. The innovative design serves as proof of concept and demonstrates significant potential in detecting various targets.

Enzyme- and label-free cascade isothermal amplification aptasensor for the ultrasensitive detection of ochratoxin A.

BACKGROUND: Ultrasensitive detection is crucial for the early warning and intervention of risk factors, ultimately benefiting the environment and human health. Low levels of ochratoxin A (OTA) present a hidden yet significant threat, and rapid detection via high-performing biosensors is therefore essential. RESULTS: A cascade isothermal amplification aptasensor (CIA-aptasensor) was designed for OTA detection. On the surface of a magnetic bead probe, the OTA level was converted into positively correlated trigger cDNA through its competitive binding with OTA-Apt. The released trigger cDNA activated catalytic hairpin assembly followed by coupling with a hybridization chain reaction to achieve CIA. After adding graphene oxide and SYBR Green I, the background interference was eliminated to specifically obtain OTA-related fluorescence. The ultrasensitive limit of detection was 0.22 pg mL-1, an improvement of 1368-fold over conventional enzyme-linked aptamer sorbent assay by the same OTA-Apt, demonstrating satisfactory reliability and practicability. Thus, the CIA-aptasensor provides an enzyme- and label-free simplified homogeneous system with minimal background interference using isothermal conditions. SIGNIFICANCE: This study provides a polymerase chain reaction-like approach for enhancing the sensitivity and performance of a biosensor, which could be extended for the application of CIA and label-free signaling strategy to other risk factors.

A multifunctional N-GO/PtCo nanocomposite bridged carbon fiber interface for the electrochemical aptasensing of CA15-3 oncomarker.

The development of integrated analytical devices is crucial for advancing next-generation point-of-care platforms. Herein, we describe a facile synthesis of a strongly catalytic and durable Nitrogen-doped graphene oxide decorated platinum cobalt (NGO-PtCo) nanocomposite that is conjugated with target-specific DNA aptamer (i-e. MUC1) and grown on carbon fiber. Benefitting from the combined features of the high electrochemical surface area of N-doped GO, high capacitance and stabilization by Co, and high kinetic performance by Pt, a robust, multifunctional, and flexible nanotransducer surface was created. The designed platform was applied for the specific detection of a blood-based oncomarker, CA15-3. The electrochemical characterization proved that nanosurface provides a highly conductive and proficient immobilization support with a strong bio-affinity towards MUC1 aptamer. The specific interaction between CA15-3 and the aptamer alters the surface properties of the aptasensor and the electroactive signal probe generated a remarkable increase in signal intensity. The sensor exhibited a wide dynamic range of 5.0 × 10-2 -200 U mL-1, a low limit of detection (LOD) of 4.1 × 10-2 U mL-1, and good reproducibility. The analysis of spiked serum samples revealed outstanding recoveries of up to 100.03 %, by the proposed aptasensor. The aptasensor design opens new revelations in the reliable detection of tumor biomarkers for timely cancer diagnosis.