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.

A photoelectrochemical aptasensor based on W6+-doped carbon nitride with carbon-rich structure for sensitive detection of diazinon.

A photoelectrochemical (PEC) aptasensor us reported based on W6+-doped carbon nitride with carbon-rich structure (WCCN). WCCN exhibited excellent photoelectric conversion performance owing to the carbon-rich structure and W6+ doping. C atoms can replace the center N/edge N atoms to form a carbon-rich structure, improving the insufficient light absorption of CN in the visible region. Also, W6+ doping forms a directional electron transfer channel, achieving the efficient separation and transport of carriers. W6+ doping and carbon-rich structure can promote the generation, transfer, and separation of photogenerated carriers, further enhancing PEC performance. The fabricated PEC aptasensor based on WCCN demonstrated a wide detection range (3.92 ~ 588 pg L-1), a low detection limit (1.31 pg L-1, S/N = 3), good reproducibility, selectivity, stability, and practical application in actual water samples. This work explores the modification strategy of element doping for carbon nitride with high photoelectric property and offers a cost-effective and simplified method for the detection of pesticide residues.

Multiplex electrochemical aptasensor for the simultaneous detection of linomycin and neomycin antibiotics.

The escalating use of antibiotics across diverse sectors, including human healthcare, agriculture, and livestock, has led to their pervasive presence in the environment, raising concerns about their impact on ecosystems and human health. Traditional detection methods, reliant on high-performance liquid chromatography and immuno-assays, face challenges of complexity, cross-reactivity, and limited specificity. Aptamer-based biosensors offer a promising alternative, leveraging the specificity, stability, and cost-effectiveness of aptamers. Herein, we present a novel dual-screen-printed carbon electrode (SPCE) biosensor, modified with a nanocomposite of gold nanoparticles (AuNPs) and carbon nanofibers (CNFs), for the label-free electrochemical detection of lincomycin and neomycin antibiotics. Lincomycin and neomycin, two antibiotics of environmental concern due to their widespread usage and potential ecological impact, were simultaneously detected using square wave voltammetry. The aptasensors showed high sensitivity with detection limits of 0.02 pg/mL and 0.035 pg/mL for lincomycin and neomycin, respectively. The developed biosensor exhibited high selectivity and reproducibility in detecting both antibiotics. This multiplex biosensing platform offers a promising strategy for efficient and cost-effective monitoring of antibiotic residues in environmental samples, addressing the critical need for robust detection methods in environmental monitoring and public health surveillance.

Development of transition metal oxide platforms for aptasensing of PSA in cell cultures.

In this study, a novel aptasensor based on a transition metal oxide-modified pencil graphite electrode (PGE) was developed for the diagnosis of early-stage prostate cancer (PCa) via monitoring the prostate-specific antigen (PSA), which is the main biomarker for PCa. Single-use PGEs modified with pulsed deposited manganese oxide (MnOx) film were used to attach the amino-terminated aptamer specific to the PSA via carbodiimide chemistry. The designed aptasensor was placed in an electrochemical cell containing ferri/ferrocyanide ions as a redox probe to measure the charge transfer resistances (Rct) of the electrode surface by electrochemical impedance spectroscopy (EIS) to follow the response of each modification step. The effect of the medium pH on the ionic structure of the aptamer molecule according to its pI value and, thus, the reversing of the direction of the response (ΔRct) by the pH change was also discussed. The level of PSA secreted from PCa cells was investigated using impedimetric transduction. The specificity of the aptasensor was validated through selectivity studies against non-specific tumor markers like VEGF and different cancer cell lines including breast cancer and androgen-insensitive prostate cancer. The developed system showcases a label-free, fast, specific, and cost-effective approach for PSA detection, highlighting the importance of medium pH and the electrostatic environment on the aptamer's response. Our work emphasizes the potential for such aptasensors in clinical diagnostics and paves the way for further exploration into using transition metal oxides in biosensing applications.

An autocatalytic hybridization circuit-based FRET aptasensor for detection of low-abundant sulfameter in human serum.

Exposure to antibiotics is considered a potential risk factor for human health. Yet, the extensive and cost-effective detection of low-abundant antibiotics in complex matrices remains a significant challenge. Herein, an aptamer and an autocatalytic hybridization circuit (AHC) were used to fabricate a fluorescence resonance energy transfer (FRET) platform to detect sulfameter (SME) in human serum. The AHC system comprised two mutually motivated hybridization chain reactions (HCR) modules, ultimately producing long-branched DNA copolymeric nanowires. This mutually reciprocal activation of two HCR modules enables continuous signal amplification, providing the AHC system with wide linear range and high sensitivity for the SME detection. Compared to the HCR-based aptasensor, the AHC-based aptasensor exhibited a wider linear range and improved sensitivity (3.3 times greater). Under optimal conditions, the fluorescent AHC-based aptasensor demonstrated a linear range (R2 was 0.996) from 0.5 to 2000 nM, with a low detection limit of 0.301 nM (S/N = 3). The fluorescent aptasensor was also validated by SME-spiked human serum samples, showing average recoveries ranging from 96.40 % to 109.30 %, with a relative standard deviation below 10.45 %. Furthermore, when tested on six human serum samples, the aptasensor results were consistent with those obtained from the commercial ELISA method. These findings demonstrate that the proposed aptasensor provides a promising approach for the practical monitoring of low-abundant SME in human serum.

Construction of a In2O3/ultrathin g-C3N4 S-scheme heterojunction for sensitive photoelectrochemical aptasensing of diazinon.

A single semiconductor-based photoelectrochemical (PEC) aptasensor usually faces a challenge of low sensitivity due to poor solar energy utilization and a high photogenerated carrier recombination rate. Herein, an ultra-thin carbon nitride nanosheet-coated In2O3 (In2O3/CNS) S-type heterojunction-based PEC aptasensor has been established to achieve highly sensitive detection of diazinon (DZN) pesticide in water environment. Construction of S-type heterojunction induces a band shift and an electric field effect, enhancing light utilization and accelerating directional transmission of carriers, leading to outstanding PEC performance. The creation of internal electric field at interface ensures stable carrier transport. Additionally, ultrathin CNS structure can effectively shorten the transport path of carriers. The close coating of In2O3 and CNS promotes the transfer of charge. The synergistic effects amplify the sensor's response, ultimately enabling the effective detection of DZN residue over a wide detection range (0.98 âˆ¼ 980.0 pg mL-1), a low detection limit (0.33 pg mL-1, S/N = 3) and excellent accuracy in practical application (RSD < 5 %). This work provides a reference for the construction of a new S-type heterojunction-based PEC sensor.

An ultrasensitive free-of-electronic sacrificial agent photoelectrochemical aptasensor for the detection of dibutyl phthalate based on Z-scheme p-n Bi-doped BiOI/Bi2S3 heterojunction.

Dibutyl phthalate (DBP), a common and outstanding plasticizer, exhibits estrogenic, mutagenic, carcinogenic, and teratogenic properties. It is easily liberated from plastic materials and pollutes aquatic ecosystems, endangering human health. Therefore, highly sensitive and selective DBP detection methods are necessary. In this work, a free-of-electronic sacrificial agent photoelectrochemical (PEC) aptasensor for DBP detection was constructed using a novel Z-scheme Bi-doped BiOI/Bi2S3 (Bi-BIS) p-n heterojunction. The Bi-BIS composites had higher visible-light absorption, charge transfer, and separation efficiency. This is attributed to the synergistic effect of the formation of Z-scheme p-n heterojunction between BiOI and Bi2S3, the plasma resonance effect of metallic Bi and photosensitization of Bi2S3, thus exhibiting large and stable photocurrent response in the absence of electron sacrificial agent, that was 10.4 and 6.4 times higher than that of BiOI and Bi2S3, respectively. Then, a DBP PEC aptasensor was constructed by modifying the DBP aptamer on the surface of the ITO/Bi-BIS electrode. The aptasensor demonstrated a broad linear range (2-500 pM) and a low detection limit (0.184 pM). What's more, because there is no interference from electronic sacrificial agent, the aptasensor exhibited excellent selectivity in real water samples. Therefore, the proposed PEC has considerable potential for DBP monitoring.

Development of a label-free electrochemical aptasensor for Rift Valley fever virus detection.

In this research, we describe the first aptasensor for the detection of the Rift Valley Fever virus (RVFV). The process involved the selection of aptamers through the systematic evolution of ligands by the exponential enrichment (SELEX) technique. After 12 rounds of selection, 6 aptamers were selected and the corresponding binding affinities were assessed using fluorescence binding assays, revealing dissociation constants ranging from 15.45 to 40.98 nM. Notably, among the aptamers, RV2 and RV3 exhibited the highest binding affinities toward RVFV, with dissociation constants of 15.45 and 18.62 nM, respectively. Thiol-modified aptamers were subsequently immobilized onto screen-printed gold electrodes, facilitating the label-free detection of RVFV through square wave voltammetry. The voltammetric aptasensor demonstrated an excellent sensitivity, with a detection limit of 0.015 ng/mL. In addition, cross-reactivity assessments were conducted, where negligible response was obtained when the aptasensor was exposed to non-specific proteins.

Optimized aptamer-based next generation biosensor for the ultra-sensitive determination of SARS-CoV-2 S1 protein in saliva samples.

COVID-19 is an infectious disease caused by the SARS-CoV-2 virus, which rapidly spread worldwide and resulted in a pandemic. Efficient and sensitive detection techniques have been devised since the onset of the epidemic and continue to be improved at present. Due to the crucial role of the SARS-CoV-2 S1 protein in facilitating the virus's entry into cells, efforts in detection and treatment have primarily centered upon this protein. In this study, a rapid, ultrasensitive, disposable, easy-to-use, cost-effective next generation biosensor based on optimized aptamer (Optimer, OPT) was developed by using a disposable pencil graphite electrode (PGE) and applied for the impedimetric determination of SARS-CoV-2 S1 protein. The S1 protein interacted with the OPT in the solution phase and then immobilized onto the PGE surface. Subsequently, measurements using electrochemical impedance spectroscopy (EIS) were conducted in a solution containing a redox probe of 1 mM [Fe(CN)6]3-/4-. Under optimum conditions, the limit of detection (LOD) for the S1 protein in buffer medium at concentrations ranging from 101 to 106 ag/mL was calculated as 8.80 ag/mL (0.11 aM). The selectivity of the developed biosensor was studied against MERS-CoV-S1 protein (MERS) and Influenza Hemagglutinin antigen (HA). Furthermore, the application of the biosensor in artificial saliva medium is demonstrated. The LOD was also calculated in artificial saliva medium in the concentration range of 101-105 ag/mL and calculated as 2.01 ag/mL (0.025 aM). This medium was also used to assess the selectivity of optimized-aptamer based biosensor.

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.

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.

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.

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.

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.

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.

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.

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.