Sensitive Detection Of Analytes Research Articles

Advanced nanomaterials-based biosensors intended for food applications

Many food hazards and agricultural chemicals generate food analysis to detect various analytes. Currently used methods for detecting threats and analyzing food quality require costly devices, workforce, and tedious procedures. Emerging nanomaterials can play an essential role in bridging this gap by rapid, sensitive, and selective detection of analytes are highlighted in this featured article. Additionally, it put some light on the characteristics, classification, and prospects of nanobiosensors.

A Versatile Platform for Sensitive and Label-Free Identification of Biomarkers through an Exo-III-Assisted Cascade Signal Amplification Strategy.

The development of a versatile and sensitive analytical biomarker detection platform is important for both early diagnosis and treatment of diseases. In the present study, we propose a novel fluorescence-based, ultrasensitive, and label-free biomarker detection platform. This platform relies on a flexible probe design compatible for multiple biomarker identification and Exo-III enzyme-triggered cascade signal amplification. We have validated that this label-free platform exhibits high sensitivity and specificity. Indeed, this platform exhibited brilliant analytical performance in qualifying a carcinoembryonic antigen and small extracellular vesicles (sEVs). It also shows excellent capability in multiplexing mapping of surface proteins of various cancer-derived sEVs. Therefore, we believe that the proposed sensing platform has great potential for clinical diagnosis and anticancer drug development.

Silica Nanochannel Array Film Supported by ß-Cyclodextrin-Functionalized Graphene Modified Gold Film Electrode for Sensitive and Direct Electroanalysis of Acetaminophen.

Convenient and sensitive detection of active analytes in complex matrix is crucial in biological, medical, and environmental analysis. Silica nanochannel array film (SNF) equipped electrochemical sensors have shown excellent anti-fouling performance in direct analysis of complex samples. In this work, we demonstrated an electrochemical sensor with anti-fouling performance for highly sensitive detection of acetaminophen (APAP) based on SNF supported by ß-cyclodextrin-graphene (CDG) nanocomposite modified Au film electrode (AuF). Because of their rich surface hydroxyls and 2D lamellar structure, CDG on AuF can serve as the nanoadhesive for compact binding SNF, which can be grown by electrochemical assisted self-assembly method in a few seconds. Attributable to the electrocatalytic property of graphene and the synergistic enrichment from both CD and SNF nanochannels towards analyte, the SNF/CDG/AuF sensor demonstrates sensitive detection of acetaminophen ranged from 0.2 to 50 μM with an ultralow limit-of-detection of 14 nM. Taking advantage of the anti-fouling ability of SNF, the sensor is able to realize accurate and convenient analysis of APAP in commercially available paracetamol tablets.

Molecularly imprinted polymers in diagnostics: accessing analytes in biofluids.

Bio-applied molecularly imprinted polymers (MIPs) are biomimetic materials with tailor-made synthetic recognition sites, mimicking biological counterparts known for their sensitive and selective analyte detection. MIPs, specifically designed for biomarker analysis within biofluids, have the potential to significantly aid patient diagnostics at the point-of-care, enabling self-health monitoring and management. Recent research in this field, facilitated by the hybridisation of materials science and biology, has developed and utilised a variety of different polymerisation synthesis methods tailored to the bio-application of MIPs. This review evaluates the principles of molecular imprinting for disease diagnostics, including recent progress in integrated MIP-sensor technologies for high-affinity analyte detection in complex biofluids from serum and saliva to cerebrospinal fluid, sweat, urine, nasopharyngeal fluid, and tears. The work highlights the state-of-the-art in the progression of MIP-sensor technologies' translation into commercially available sensors and their potential contribution to disease detection systems in healthcare settings.

An entropy-driven signal-off DNA circuit for label-free, visual detection of small molecules with enhanced accuracy.

An entropy-driven DNA circuit offers an efficient means of sensitive analyte detection with signal amplification. In this article, we rationally engineered an aptamer-based entropy-driven signal-off DNA circuit for colorimetric detection of small molecules. The proposed signal-off DNA circuit is activated by target small molecule binding to drive the collapse of G-quadruplex DNAzyme, accompanied by the colour change of the detection solution from dark blue to light blue. Entropy-driven recycling hybridization significantly magnified the input signal of the target small molecule. Such an assay enables naked-eye detection of adenosine triphosphate and oxytetracycline at concentrations as low as 0.5 μM and 1 μM respectively. Moreover, when compared with the signal-on DNA circuit, the entropy-driven signal-off DNA circuit for colorimetric detection has two advantages. Firstly, unlike in the signal-on DNA circuit, the unavoidable formation of waste complexes in the absence of a target in the signal-off DNA circuit has no influence on target detection performance as its background signal is only determined by the substrate complex. Secondly, the signal-on DNA circuit cannot distinguish false-positive signals generated by invasive catalysts (e.g., HRP, serum, Fe3O4), while the signal-off DNA circuit can distinguish those signals as undesired signals. Overall, the signal-off DNA circuit affords a novel strategy for sensitive and accurate detection of small molecules.

Recent Advances in Metal-Organic Framework-Based Electrochemical Biosensing Applications.

In the face of complex environments, considerable effort has been made to accomplish sensitive, accurate and highly-effective detection of target analytes. Given the versatility of metal clusters and ligands, high porosity and large specific surface area, metal–organic framework (MOF) provides researchers with prospective solutions for the construction of biosensing platforms. Combined with the benefits of electrochemistry method such as fast response, low cost and simple operation, the untapped applications of MOF for biosensors are worthy to be exploited. Therefore, this review briefly summarizes the preparation methods of electroactive MOF, including synthesize with electroactive ligands/metal ions, functionalization of MOF with biomolecules and modification for MOF composites. Moreover, recent biosensing applications are highlighted in terms of small biomolecules, biomacromolecules, and pathogenic cells. We conclude with a discussion of future challenges and prospects in the field. It aims to offer researchers inspiration to address the issues appropriately in further investigations.

A Comparison of EIS and QCM NanoMIP-Based Sensors for Morphine.

In this work we have compared two different sensing platforms for the detection of morphine as an example of a low molecular weight target analyte. For this, molecularly imprinted polymer nanoparticles (NanoMIP), synthesized with an affinity towards morphine, were attached to an electrochemical impedance spectroscopy (EIS) and a quartz crystal microbalance (QCM) sensor. Assay design, sensors fabrication, analyte sensitivity and specificity were performed using similar methods. The results showed that the EIS sensor achieved a limit of detection (LOD) of 0.11 ng·mL−1, which is three orders of magnitude lower than the 0.19 µg·mL−1 achieved using the QCM sensor. Both the EIS and the QCM sensors were found to be able to specifically detect morphine in a direct assay format. However, the QCM method required conjugation of gold nanoparticles (AuNPs) to the small analyte (morphine) to amplify the signal and achieve a LOD in the µg·mL−1 range. Conversely, the EIS sensor method was labor-intensive and required extensive data handling and processing, resulting in longer analysis times (~30–40 min). In addition, whereas the QCM enables visualization of the binding events between the target molecule and the sensor in real-time, the EIS method does not allow such a feature and measurements are taken post-binding. The work also highlighted the advantages of using QCM as an automated, rapid and multiplex sensor compared to the much simpler EIS platform used in this work, though, the QCM method will require sample preparation, especially when a sensitive (ng·mL−1) detection of a small analyte is needed.

Highly sensitive label-free detection of analytes at different scales using uniform graphene-nanopyramids hybrid SERS system

Surface-enhanced Raman spectroscopy (SERS) has attracted enormous interests as a biological sensing technique. However, the wide application of SERS technique suffers from the limitation of sensitivity, uniformity and universality for the analytes. Herein, a graphene-nanopyramids hybrid SERS system with high uniformity and sensitivity was used to label-freely detect analytes at different scales. Colloidal lithography and modern semiconductor nanofabrication process were employed for the fabrication of wafer-scale highly-ordered array of Au nanopyramids, which ensures the uniformity of the system. The graphene layer not only plays a role of biology-compatible supporting layer for analytes but also further enhances the Raman signals and facilitates the quantitative analysis capability of the hybrid system as an intensity gauge. For nanoscale chemical and protein molecules including Rhodamine 6G (R6G), methylene blue (MB), catalase and lysozyme with concentrations lower than 10−10 M, clear SERS signals can be obtained with analytical enhancement factors (EFs) of ~109 for R6G and MB. For micron-scale analytes, Raman fingerprints of cells, i.e. erythrocyte and leukocyte have been obtained. Moreover, using statistical principal component analysis method, one can easily distinguish different analytes based on their Raman fingerprints. The experiment results of EF are in good agreement with the theoretical values predicted by finite-difference time-domain simulation. Such a wafer-scale, highly uniform and universal system will certainly enable the wider application of SERS in multiscale label-free detection of chemicals, proteins and cells, etc. with high sensitivity and specificity.

A Customized Microfluidic Paper-Based Platform for Colorimetric Immunosensing: Demonstrated via hCG Assay for Pregnancy Test

Over the past decades, paper-based lateral flow immunoassays (LFIAs) have been extensively developed for rapid, facile, and low-cost detection of a wide array of target analytes in a point-of-care manner. Conventional home pregnancy tests are the most significant example of LFAs, which detect elevated concentrations of human chorionic gonadotrophin (hCG) in body fluids to identify early pregnancy. In this work, we have upgraded these platforms to a higher version by developing a customized microfluidic paper-based analytical device (μPAD), as the new generation of paper-based point-of-care platforms, for colorimetric immunosensing. This will offer a cost-efficient and environmentally friendly alternative platform for paper-based immunosensing, eliminating the need for nitrocellulose (NC) membrane as the substrate material. The performance of the developed platform is demonstrated by detection of hCG (as a model case) in urine samples and subsequently indicating positive or negative pregnancy. A dual-functional silane-based composite was used to treat filter paper in order to enhance the colorimetric signal intensity in the detection zones of μPADs. In addition, microfluidic pathways were designed in a manner to provide the desired regulated fluid flow, generating sufficient incubation time (delays) at the designated detection zones, and consequently enhancing the obtained signal intensity. The presented approaches allow to overcome the existing limitations of μPADs in immunosensing and will broaden their applicability to a wider range of assays. Although, the application of the developed hCG μPAD assay is mainly in qualitative (i.e., positive or negative) detection of pregnancy, the semi-quantitative measurement of hCG was also investigated, indicating the viability of this assay for sensitive detection of the target hCG analyte within the related physiological range (i.e., 10–500 ng/mL) with a LOD value down to 10 ng/mL.

Molecular Detection of Borrelia Bacteria in Cerebrospinal Fluid-Optimisation of Pre-Analytical Sample Handling for Increased Analytical Sensitivity.

The main tools for clinical diagnostics of Lyme neuroborreliosis (LNB) are based on serology, i.e., detection of antibodies in cerebrospinal fluid (CSF). In some cases, PCR may be used as a supplement, e.g., on CSF from patients with early LNB. Standardisation of the molecular methods and systematic evaluation of the pre-analytical handling is lacking. To increase the analytical sensitivity for detection of Borrelia bacteria in CSF by PCR targeting the 16S rRNA gene, parameters were systematically evaluated on CSF samples spiked with a known amount of cultured Borrelia bacteria. The results showed that the parameters such as centrifugation time and speed, the use of complementary DNA as a template (in combination with primers and a probe aiming at target gene 16S rRNA), and the absence of inhibitors (e.g., erythrocytes) had the highest impact on the analytical sensitivity. Based on these results, a protocol for optimised handling of CSF samples before molecular analysis was proposed. However, no clinical evaluation of the proposed protocol has been done so far, and further investigations of the diagnostic sensitivity need to be performed on well-characterised clinical samples from patients with LNB.

Measurement of trace bisphenol A in drinking water with combination of immunochromatographic detection technology and SERS method

Sensitive and selective detection of target analyte is very important in many fields such as commodity inspection and quality monitoring. In this work, based on the principle of competitive immunoassay, surface-enhanced Raman spectroscopy (SERS) was used to establish a rapid and highly sensitive method for the detection of trace amounts of bisphenol A in water. Here, Raman molecule 5,5-dithiobis-2-nitrobenzoic acid and anti-BPA antibody were conjugated with Au (core)@Ag (shell) nanoparticle to serve as SERS nanoprobe. After the SERS nanoprobe is combined with the substance to be tested, it uses the siphon effect to pass through the test line and the charging line on the test strip. And the Raman test was performed on the T line with a Raman spectrometer. The detection limitation was 0.1 pg/mL. Compared with the reported gas chromatography, liquid chromatography, fluorescence analysis, and other detection methods, SERS ICA does not demand complicated sample preparation procedures, and has the advantages of simple detection methods, quick results, High sensitivity, good specificity, and low technical demands for laboratory environment and testers. In addition, Raman spectrometers have gradually developed to be portable, making it easier to meet the needs of on-site rapid and highly sensitive detection, and will show broad prospects for applications in the fields of biomedical diagnosis and food safety monitoring.

Immunological Analytical Techniques for Cosmetics Quality Control and Process Monitoring

Cosmetics analysis represents a rapidly expanding field of analytical chemistry as new cosmetic formulations are increasingly in demand on the market and the ingredients required for their production are constantly evolving. Each country applies strict legislation regarding substances in the final product that must be prohibited or regulated. To verify the compliance of cosmetics with current regulations, official analytical methods are available to reveal and quantitatively determine the analytes of interest. However, since ingredients, and the lists of regulated/prohibited substances, rapidly change, dedicated analytical methods must be developed ad hoc to fulfill the new requirements. Research focuses on finding innovative techniques that allow a rapid, inexpensive, and sensitive detection of the target analytes in cosmetics. Among the different methods proposed, immunological techniques are gaining interest, as they make it possible to carry out low-cost analyses on raw materials and finished products in a relatively short time. Indeed, immunoassays are based on the specific and selective antibody/antigen reaction, and they have been extensively applied for clinical diagnostic, alimentary quality control and environmental security purposes, and even for routine analysis. Since the complexity and variability of the matrices, as well as the great variety of compounds present in cosmetics, are analogous with those from food sources, immunological methods could also be applied successfully in this field. Indeed, this would provide a valid approach for the monitoring of industrial production chains even in developing countries, which are currently the greatest producers of cosmetics and the major exporters of raw materials. This review aims to highlight the immunological techniques proposed for cosmetics analysis, focusing on the detection of prohibited/regulated compounds, bacteria and toxins, and allergenic substances, and the identification of counterfeits.

Sensitive analytical detection of nitrite using an electrochemical sensor with STAB-functionalized Nb2C@MWCNTs for signal amplification

An electrochemical sensor based on stearyl trimethyl ammonium bromide - functionalized niobium carbide@multi-walled carbon nanotubes (Nb2C@MWCNTs-STAB) for signal amplification was successfully constructed for sensitive detection of nitrite (NO2−). Niobium carbide@multi-walled carbon nanotubes (Nb2C@MWCNTs) with high electrical conductivity and water dispersibility were first prepared in a one-pot hydrothermal synthesis, after which cationic STAB was added to overcome the negative surface charge on the Nb2C@MWCNTs. The electrostatic attraction between Nb2C@MWCNTs-STAB and NO2− was improved by the STAB, which enhanced the sensitivity of the constructed sensor for NO2−. Under optimized conditions, Nb2C@MWCNTs-STAB/GCE exhibited excellent analytical performance for detection NO2− with two wide liner ranges (0.1–100 μmol L−1 and 100–2000 μmol L−1) and a limit of detection of 0.022 μmol L−1. Nitrite recovery tests in milk and spinach samples showed recoveries in the range of 89.82–104.52%. The NO2− residues in ham and pickled vegetable (cedrela sinensis) samples were analysed using the presented sensor and a spectrophotometric method, with no significant difference found between the results of the two methods.

Toward the Development of Rapid, Specific, and Sensitive Microfluidic Sensors: A Comprehensive Device Blueprint.

Recent advances in nano/microfluidics have led to the miniaturization of surface-based chemical and biochemical sensors, with applications ranging from environmental monitoring to disease diagnostics. These systems rely on the detection of analytes flowing in a liquid sample, by exploiting their innate nature to react with specific receptors immobilized on the microchannel walls. The efficiency of these systems is defined by the cumulative effect of analyte detection speed, sensitivity, and specificity. In this perspective, we provide a fresh outlook on the use of important parameters obtained from well-characterized analytical models, by connecting the mass transport and reaction limits with the experimentally attainable limits of analyte detection efficiency. Specifically, we breakdown when and how the operational (e.g., flow rates, channel geometries, mode of detection, etc.) and molecular (e.g., receptor affinity and functionality) variables can be tailored to enhance the analyte detection time, analytical specificity, and sensitivity of the system (i.e., limit of detection). Finally, we present a simple yet cohesive blueprint for the development of high-efficiency surface-based microfluidic sensors for rapid, sensitive, and specific detection of chemical and biochemical analytes, pertinent to a variety of applications.

Low-Cost, Open-Source Device for High-Performance Fluorescence Detection of Isothermal Nucleic Acid Amplification Reactions.

The ability to detect SARS-CoV-2 is critical to implementing evidence-based strategies to address the COVID-19 global pandemic. Expanding SARS-CoV-2 diagnostic ability beyond well-equipped laboratories widens the opportunity for surveillance and control efforts. However, such advances are predicated on the availability of rapid, scalable, accessible, yet high-performance diagnostic platforms. Methods to detect viral RNA using reverse transcription loop-mediated isothermal amplification (RT-LAMP) show promise as rapid and field-deployable tests; however, the per-unit costs of the required diagnostic hardware can be a barrier for scaled deployment. Here, we describe a diagnostic hardware configuration for LAMP technology, named the FABL-8, that can be built for approximately US$380 per machine and provide results in under 30 min. Benchmarking showed that FABL-8 has a similar performance to a high-end commercial instrument for detecting fluorescence-based LAMP reactions. Performance testing of the instrument with RNA extracted from a SARS-CoV-2 virus dilution series revealed an analytical detection sensitivity of 50 virus copies per microliter-a detection threshold suitable to detect patient viral load in the first few days following symptom onset. In addition to the detection of SARS-CoV-2, we show that the system can be used to detect the presence of two bacterial pathogens, demonstrating the versatility of the platform for the detection of other pathogens. This cost-effective and scalable hardware alternative allows democratization of the instrumentation required for high-performance molecular diagnostics, such that it could be available to laboratories anywhere-supporting infectious diseases surveillance and research activities in resource-limited settings.

Refractometric gas sensing using a whispering gallery mode microresonator coated with a supra-micron sol-gel layer

Spherical microresonators have been used to measure small concentrations of ammonia vapors. By tracking the shift of a whispering gallery mode (WGM) frequency, we can detect small changes of the refractive index of the medium in which the WGM electric field is confined. These changes are correlated to the chemical content of the medium. When a porous layer of silica (SiO2) is coated onto a silica sphere surface, molecules of the gas analyte can diffuse into the layer and interact with the WGM electric field thus increasing the sensitivity of analyte detection. In this paper, we present a theoretical analysis of the phenomenon and demonstrate both theoretically and experimentally that the sensitivity of the WGM sensors for ammonia gas detection can be significantly increased by varying the thickness of the porous coating.

Gold Nanoparticles Photosensitization towards 3,4,9,10-Perylenetetracarboxylic Dianhydride Integrated with a Dual-Particle Three-Dimensional DNA Roller: A General “ON–OFF–ON” Photoelectric Plasmon-Enhanced Biosensor

A high initial signal for the sensitive detection of analytes is critical in photoelectrochemical (PEC) biosensing systems. As a semiconductor, 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) possesses an appropriate optical band gap of 2.5 eV and inherently intense and stable PEC response. When gold nanoparticles (Au NPs) are electrodeposited on the surface of PTCDA to form a Schottky junction (Au NPs/PTCDA), a surprising and satisfactory PEC performance is unfolded before our eyes. Considering the outstanding PEC behaviors of Au NPs/PTCDA and the great quenching effect of gold nanoclusters (Au NCs), the "ON-OFF-ON" PEC sensing platform has been developed for microRNA 1246 (miRNA 1246) detection combined with the cascaded quadratic amplification strategy of the polymerization/nicking reaction and dual-particle 3D DNA roller. The higher initial PEC signals of the system can be acquired by regulating the deposition time for 35 s (-0.2 V), which is derived from the synergetic effect of localized surface plasmon resonance of Au NPs and the formation of a Schottky junction. The dual-particle 3D DNA roller has been designed to guarantee wide walking space, remarkable operation performances, and inhibition of derailment. The proposed biosensor shows a dynamic range from 10 aM to 1 pM at a low detection limit of 3.1 aM and exhibits good analytical behaviors while analyzing miRNA 1246 in healthy human serum samples. This work not only expands the application of organic photoelectric materials in bioanalysis but also provides potential possibility of detecting other biomarkers by choosing appropriate target units.

Exponential Amplification Using Photoredox Autocatalysis

Exponential molecular amplification such as the polymerase chain reaction is a powerful tool that allows ultrasensitive biodetection. Here, we report a new exponential amplification strategy based on photoredox autocatalysis, where eosin Y, a photocatalyst, amplifies itself by activating a nonfluorescent eosin Y derivative (EYH3-) under green light. The deactivated photocatalyst is stable and rapidly activated under low-intensity light, making the eosin Y amplification suitable for resource-limited settings. Through steady-state kinetic studies and reaction modeling, we found that EYH3- is either oxidized to eosin Y via one-electron oxidation by triplet eosin Y and subsequent 1e-/H+ transfer, or activated by singlet oxygen with the risk of degradation. By reducing the rate of the EYH3- degradation, we successfully improved EYH3--to-eosin Y recovery, achieving efficient autocatalytic eosin Y amplification. Additionally, to demonstrate its flexibility in output signals, we coupled the eosin Y amplification with photoinduced chromogenic polymerization, enabling sensitive visual detection of analytes. Finally, we applied the exponential amplification methods in developing bioassays for detection of biomarkers including SARS-CoV-2 nucleocapsid protein, an antigen used in the diagnosis of COVID-19.

Chemical modification of M13 bacteriophage as nanozyme container for dramatically enhanced sensitivity of colorimetric immunosensor

Herein, a sulfydryl modification of M13 bacteriophage was introduced as bio-functional component including biological recognition, and nanozyme container for enhancing sensitivity of colorimetric immunsensor, where the seven peptide sequence fused on the p3 protein of M13 was used to mimic deoxynivalenol (DON) antigen for recognizing the anti-DON monoclonal antibody, while the sulfydryl groups modified on capsid proteins were used to load numerous Ag coated Au nanoparticles (AuNPs@Ag) for improving the peroxidase-like activity of AuNPs@Ag. Owing its great loading capacity, the M13 bacteriophage assembled AuNPs@Ag nanocomposites (M13DON@AuNPs@Ag) showed approximately 48- and 105-fold enhanced catalytic efficacy to hydrogen peroxide and tramethylbenzidine than those of natural horse radish peroxidase (HRP). Using the M13DON@AuNP@Ag as signal amplifier, the proposed immunosensor exhibits a very high sensitivity for DON detection with the 50 % competitive inhibition concentration (IC50) and detection limit (LOD) of 2.03 ng/mL and 13.67 pg/mL, respectively. These values are about 26- and 947-fold lower than those of conventional HRP based ELISA method (IC50 and LOD values =52.43 ng/mL and 12.95 ng/mL, respectively). In addition, the proposed method also showed good specificity and accepted accuracy for DON detection in real corn samples. Moreover, the reliability of this novel strategy was further confirmed through compared with the high performance liquid chromatography method (HPLC). All in all, the M13 bacteriophage exhibits a promising potential as nanozyme container for enhancing the sensitivity of immunosensor, and this novel signal amplification system can be easily extended for highly sensitive detection of other analytes by altering specific mimic peptide sequence.

Synthesis of Zn metal–organic framework doped magnetic graphene oxide for preconcentration and extraction of cefixime followed by its measurement using HPLC

In this work, an attempt was made to develop a powerful method for the determination of cefixime, as a widely used cephalosporin antibiotic. The method was based on the facile extraction and preconcentration of cefixime using Zn metal–organic framework doped magnetic graphene oxide composite (ZnMOF@MGO), followed by its determination using high-performance liquid chromatography (HPLC). The high surface area, great stability, and distinct features of the new adsorbent made it ideal for very efficient interactions with analyte molecules. ZnMOF@MGO was able to effectively extract cefixime from the complex matrix of real samples. Furthermore, the application of the magnetic-solid phase extraction (MSPE) process provided a low-cost and simple extraction process with a reduced extraction time. The combination of a high-performance extraction with a potent HPLC system resulted in a highly sensitive and selective analytical detection method. The method was able to detect cefixime in a linear range of 0.5–130 ng mL−1, with a detection limit of 0.11 ng mL−1, no important interfering effect was caused by other examined drugs. It was examined for the analysis of cefixime content of pharmaceutical and biological samples and acceptable recovery values were obtained.