Detection Of Saxitoxin Research Articles

Development of a rapid magnetic relaxation switching aptasensor for detection of saxitoxin using Fe3+/silver nanoparticles reaction system

Saxitoxin (STX) is a highly toxic marine bio-toxin, which has attracted great attention in the field of environmental and food safety. It is of crucial importance to develop efficient, sensitive and cost-effective methods for detecting STX. Here, we designed a magnetic relaxation switching (MRS) aptasensor for detection of STX based on FeCl3-regulated the aptamer-functionalized silver nanoparticles-coated magnetic nanoparticles (MNP@Ag NPs). In the light of the sensing effect of transverse relaxation time (T2) for optimizing, the etched time, the concentration of MNP@Ag NPs, the concentration of aptamers and incubation time were 15 min, 4 mg mL−1, 0.4 μM and 90 min, respectively. The MRS aptasensor showed good linearity amidst the sensing range of 0.2 μM to 1.0 μM and the limit of detection (LOD, S/N = 3) of 0.18 μM. Additionally, the MRS aptasensor demonstrated excellent sensitivity, reproducibility, and stability in clams and mantis shrimps. The recovery of STX ranged from 82.6 % to 101.5 % with low relative standard deviation (RSD) values, suggesting its effectiveness for detecting STX across a wide array of seafood samples.

Nanoflower Microreactor Based Versatile Enhancer for Recognition Cofactor-Dependent Enzyme Biocatalysis toward Saxitoxin Detection.

Investigating organic carriers' utilization efficiency and bioactivity within organic-inorganic hybrid nanoflowers is critical to constructing sensitive immunosensors. Nevertheless, the sensitivity of immunosensors is interactively regulated by different classes of biomolecules such as antibodies and enzymes. In this work, we introduced a new alkaline phosphatase-antibody-CaHPO4 hybrid nanoflowers (AAHNFs) microreactor based colorimetric immunoprobe. This system integrates a biometric unit (antibody) with a signal amplification element (enzyme) through the biomineralization process. Specifically, the critical factors affecting antibody recognition activity in the formation mechanism of AAHNFs are investigated. The designed AAHNFs retain antibody recognition ability with enhanced protection for encapsulated proteins against high temperature, organic solvents, and long-term storage, facilitating the selective construction of lock structures against antigens. Additionally, a colorimetric immunosensor based on AAHNFs was developed. After ascorbic acid 2-phosphate hydrolysis by alkaline phosphatase (ALP), the generated ascorbic acid decomposes I2 to I-, inducing the localized surface plasmon resonance in the silver nanoplate, which is effectively tuned through shape conversion to develop the sensor. Further, a 3D-printed portable device is fabricated, integrated with a smartphone sensing platform, and applied to the data of collection and analysis. Notably, the immunosensor exhibits improved analytical performance with a 0.1-6.25 ng·mL-1 detection range and a 0.06 ng·mL-1 detection limit for quantitative saxitoxin (STX) analysis. The average recoveries of STX in real samples ranged from 85.9% to 105.9%. This study presents a more in-depth investigation of the recognition element performance, providing insights for improved antibody performance in practical applications.

Nanopillar array-based electrochemical aptamer sensor for STX sensitivity detection.

Saxitoxin (STX) is a cyanotoxin with high toxicity, and therefore, there is an urgent need to develop a facile detection method for STX. In this study, an ordered nanopillar array-based electrochemical aptasensor was fabricated for the high-performance detection of STX. The anti-STX aptamer with methylene blue (MB) incorporated at the 3'-end (MB-Apt) was immobilized at the surface of an Au@PAN nanopillar array electrode and used as the recognition element. The proposed aptasensor demonstrated highly sensitive and selective STX detection because of synergistic catalysis effects of MB and ordered nanopillar arrays along with the selection of MB-Apt. The nanopillar array-based electrochemical aptasensor exhibited high sensitivity over a wide linear concentration range of 1 pM-3 nM with a linear regression equation of ΔI (μA) = 28.0 + 6.9 × log[STX] (R2 = 0.98079) and 3-100 nM with a linear regression equation of ΔI (μA) = 10.7 + 43.4 × log[STX] (R2 = 0.98772), where R is the correlation coefficient. In addition, the limit of detection (LOD) was as low as 1 pM. Furthermore, the designed aptasensor demonstrated excellent selectivity toward STX, preventing interference from neo-STX, okadaic acid, and common metal ions. The presented orderly nanopillar array-based strategy to develop an electrochemical aptasensor for STX detection offers a promising method for developing high-performance electrochemical sensors, and the presented aptasensor should find useful application in the detection of shellfish poison.

Development of a Quick and Highly Sensitive Amplified Luminescent Proximity Homogeneous Assay for Detection of Saxitoxin in Shellfish.

Saxitoxin (STX), an exceptionally potent marine toxin for which no antidote is currently available, is produced by methanogens and cyanobacteria. This poses a significant threat to both shellfish aquaculture and human health. Consequently, the development of a rapid, highly sensitive STX detection method is of great significance. The objective of this research is to create a novel approach for identifying STX. Therefore, amplified luminescent proximity homogeneous assay (AlphaLISA) was established using a direct competition method based on the principles of fluorescence resonance energy transfer and antigen-antibody specific binding. This method is sensitive, rapid, performed without washing, easy to operate, and can detect 8-128 ng/mL of STX in only 10 min. The limit of detection achieved by this method is as low as 4.29 ng/mL with coefficients of variation for the intra-batch and inter-batch analyses ranging from 2.61% to 3.63% and from 7.67% to 8.30%, respectively. In conclusion, our study successfully establishes a simple yet sensitive, rapid, and accurate AlphaLISA method for the detection of STX which holds great potential in advancing research on marine biotoxins.

Possibility of spectrofluorimetric detection of saxitoxins when monitoring water bodies during their «blooming» period

Possibility of spectrofluorimetric detection of saxitoxins when monitoring water bodies during their «blooming» period

Review of the occurrence, treatment technologies, and detection methods for saxitoxins in freshwaters.

The increasing occurrence of saxitoxins in freshwaters is becoming a concern for water treatment facilities owing to its structural properties which make it resistant to oxidation at pH < 8. Hence, it is crucial to be able to monitor these toxins in surface and drinking water to protect public health. This review aims to outline the current state of knowledge related to the occurrence of saxitoxins in freshwaters and its removal strategies and provide a critical assessment of the detection methods to provide a basis for further development. Temperature and nutrient content are some of the factors that influence the production of saxitoxins in surface waters. A high dose of sodium hypochlorite with sufficient contact time or activated carbon has been shown to efficiently remove extracellular saxitoxins to meet the drinking water guidelines. While HILIC-MS has proven to be a powerful technology for more sensitive and reliable detection of saxitoxin and variants after solid phase extraction, ELISA is cost-effective and easy to use and is used by Ohio EPA for surveillance with a limit of detection of 0.015 μg/L. However, there is a need for the development of cost-effective and sensitive techniques that can quantify the variants of saxitoxin.

Enhanced SERS aptasensor for sensitive detection of saxitoxin based on HAuCl 4/H 2O 2reaction system and Pt/Au nanozyme

Enhanced SERS aptasensor for sensitive detection of saxitoxin based on HAuCl ₄/H ₂O ₂reaction system and Pt/Au nanozyme

Nanozyme-assisted molecularly imprinted polymer-based indirect competitive ELISA for the detection of marine biotoxin

Saxitoxin (STX), which is produced by certain dinoflagellate species, is a type of paralytic shellfish poisoning toxin that poses a serious threat to human health and the environment. Therefore, developing a technology for the convenient and cost-effective detection of STX is imperative. In this study, we developed an affinity peptide-imprinted polymer-based indirect competitive ELISA (ic-ELISA) without using enzyme–toxin conjugates. AuNP/Co3O4@Mg/Al cLDH was synthesized by calcining AuNP/ZIF-67@Mg/Al LDH, which was obtained by combining AuNPs, ZIF-67, and flower-like Mg/Al LDH. This synthesized nanozyme exhibited high catalytic activity (Km = 0.24 mM for TMB and 132.5 mM for H2O2). The affinity peptide-imprinted polymer (MIP) was imprinted with an STX-specific template peptide (STX MIP) on a multi-well microplate and then reacted with an STX-specific signal peptide (STX SP). The interaction between the STX SP and MIP was detected using a streptavidin-coated nanozyme (SA-AuNP/Co3O4@Mg/Al cLDH). The developed MIP-based ic-ELISA exhibited excellent selectivity and sensitivity, with a limit of detection of 3.17 ng/mL (equivalent: 0.317 μg/g). Furthermore, the system was validated using a commercial ELISA kit and mussel tissue samples, and it demonstrated a high STX recovery with a low coefficient of variation. These results imply that the developed ic-ELISA can be used to detect STX in real samples.

A novel screening on the specific peptides by molecular simulation and development of the highly-sensitive electrochemical sensor for saxitoxin

A simple and quick electrochemical sensor has been developed for the detection of saxitoxin (STX) based on the specific peptides, which were screened and identified by molecular simulation and electrochemical characterization, respectively. The library of saxitoxin peptides was obtained followed by structural analysis of the receptor and STX, molecular docking, amino acid mutation, and molecular dynamics. The specific peptide (named S4) was screened by the theoretical interaction energy (ΔE) and the fact electrochemical identification. Meanwhile, the reduced graphene oxide (rGO) and gold nanoparticles (AuNPs) materials were introduced to improve the electron mass transfer and increase the electrochemical signal. Under the optimal condition, one simple and quick electrochemical sensor was developed between the ΔI and the concentration of STX in the range of 10 ∼ 1000 ng/L with a limit of detection (LOD) of 6.9 × 10–4 μg/L (S/N = 3). In seawater, artificial seawater, and oyster powder samples, a good recovery rate was found in the range of 87.3 %–116.2 %. In addition, excellent selectivity, good reproducibility, and stability were obtained. It provides a novel idea for the screening of the specific peptides of toxins and the development of the electrochemical peptides sensor.

A dual-mode optical sensor for sensitive detection of saxitoxin in shellfish based on three-in-one functional nanozymes

Saxitoxin (STX), one of paralytic shellfish poison neurotoxins with high toxicity, posing a significant threat to seafood safety. Therefore, it is of great need to protect human health by screening STX contaminated seafood samples. In this study, to achieve specificity for STX, molecularly imprinted polymers (MIP) were fabricated on Au-Pt nanoparticles modified Fe3O4 magnetic nanozymes (MS@Au-Pt NZs) with numerous memory cavities (MS@Au-Pt/MIP), which catalyzed the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB). STX will occupy the recognition cavity of MIP and obstruct the catalytic site of MS@Au-Pt, thus hindering the color development reaction, and the oxidized TMB (oxTMB) can be measured by Raman spectroscopy and recorded with Raman signals. Under the optimal conditions, the MIDMs method obtained a wide linear range for colorimetric assay (0.01 μM to 100 μM) and Raman detection (0.1 nM to 100 nM), with limits of detection (3σ/S, n=3) of 3.1 nM and 0.03 nM, respectively. As a proof-of-concept, the approach showed acceptable recoveries of 78.0∼96.2% in real samples of mussel and clam. The dual-mode optical sensor, therefore, is hopeful to be a potential candidate for sensitive and accurate detection of STX in seafood.

Development of magnetic fluorescence aptasensor for sensitive detection of saxitoxin based on Fe3O4@Au-Pt nanozymes

In this work, on the basis of Fe3O4@Au-Pt nanozymes (MAP NZs) and aptamer recognition, a magnetic fluorescent aptasensor (MFA) was developed for sensitive and accurate detection of saxitoxin (STX). With the bridge of STX aptamer (AptSTX) and complementary DNA (cDNA), AptSTX decorated MAP NZs (MAP/Apt) and cDNA modified green quantum dots (cDNA@g-QDs) were connected to form MAP/Apt-cDNA@g-QDs complex. As STX behaves a strong binding ability towards AptSTX, it will compete with cDNA and hybridize with Apt to release cDNA@g-QDs. With the addition of TMB, MAP will catalyze TMB to the oxidized TMB (ox-TMB), thereby quenching the fluorescence of g-QDs due to the inner filter effect. Based on this finding, the quantitative relationship between the change in fluorescence of gQDs and STX concentration was explored with a limit of detection (LOD, S/N = 3) of 0.6 nM. An internal standard signal of oxTMB was adopted and reduced the fluctuation of fluorescence signal output. Besides, the fluorescence probe can selectively recognize and detect STX among five marine toxins. Eventually, the MFA method behaved good performance in detecting seafood samples with recoveries of 82.0 % ∼ 102.6 % as well as coefficient of variations (CV) of 7.2 % ∼ 10.3 %. Therefore, the method with internal signal is hopeful to be a potential candidate for sensitive and accurate detection of STX in seafood.

DNA walker coupled with nicking endonuclease for sensitive electrochemical detection of saxitoxin

Based on DNA-based signal amplification strategies, a nicking endonuclease Nb.BbvCI powered DNA walker machine-based electrochemical aptasensor exhibited high sensitivity and good selectivity in the detection of STX.

Highly sensitive electrochemical peptide-based biosensor for marine biotoxin detection using a bimetallic platinum and ruthenium nanoparticle-tethered metal-organic framework modified electrode.

Saxitoxin (STX) is a highly toxic small-molecule cyanotoxin that is water-soluble, stable in acidic media, and thermostable. STX is hazardous to human health and the environment in ocean, thus it is an important to detect it at very low concentrations. Herein, we developed an electrochemical peptide-based biosensor for the trace detection of STX in different sample matrix utilizing differential pulse voltammetry (DPV) signal. We synthesized the nanocomposite of zeolitic imidazolate framework-67 (ZIF-67) decorated bimetallic platinum (Pt) and ruthenium (Ru) nanoparticles (Pt-Ru@C/ZIF-67) using impregnation method. The nanocomposite modified with screen-printed electrode (SPE) was subsequently used to detect STX in the range of 1-1,000ngmL-1, with a detection limit (LOD) of 26.7pgmL-1. The developed peptide-based biosensor is highly selective and sensitive towards STX detection, thus it represents a promising strategy for the development of novel portable bioassay for monitoring various hazardous molecules in aquatic food chains.

A Novel Fluorescent Aptasensor Based on Mesoporous Silica Nanoparticles for Selective and Sensitive Detection of Saxitoxin in Shellfish

Background: Saxitoxin (STX) stands as one of the most potent marine biotoxins, exhibiting high lethality. Despite its severity, current treatments remain ineffective, and existing detection techniques are limited due to ethical concerns and technical constraints. Methods: Herein, an innovative approach was constructed for STX detection, utilizing mesoporous silica nanoparticles (MSN) as a foundation. This innovative, easy, and label-free aptamer (Apt)- sensor was fabricated. Apts were employed as molecular identification probes and "gated molecules," while rhodamine 6G was encapsulated within particles to serve as a signal probe. In a lack of STX, Apts immobilized on an MSN surface kept a "gate" closed, preventing signal probe leakage. Upon the presence of STX, the "gate" opened, allowing a particular binding of Apts to STX and a subsequent release of a signal probe. Results: Experimental results demonstrated a positive correlation between fluorescence intensity and concentrations of STX within a range of 1 to 80 nM, with an exceptional limit of detection of 0.12 nM. Furthermore, the selectivity and stability of a biosensor were rigorously evaluated, validating its reliability. Conclusion: This newly developed sensing strategy exhibits remarkable performance in STX detection. Its success holds significant promise for advancing portable STX detection equipment, thereby addressing a pressing need for efficient and ethical detection methods in combating marine biotoxin contamination.

Enzyme-nanozyme cascade-amplified ratiometric fluorescence immunoassay for the ultrasensitive detection of saxitoxin

Herein, a ratiometric fluorescence (RF) immunoassay platform coupling with enzyme-nanozyme cascade amplification strategy was fabricated for precise and ultrasensitive quantification of saxitoxin (STX). In this strategy, oxidase-like cobalt oxyhydroxide nanoflakes (CoOOH NFs) catalyzed the oxidation of non-fluorescent o-phenylenediamine (OPD) into fluorescent 2,3-diaminophenazine with the maximum emission at 568 nm. This nanozyme-triggered fluorogenic reaction was cascaded with the alkaline phosphatase (ALP)-catalyzed hydrolysis of ascorbic acid 2-phosphate into ascorbic acid (AA) through the redox reaction between AA and CoOOH NFs. During the redox reaction, CoOOH NFs were reduced into Co2+ without oxidase-like activity, whereas AA was converted into dehydroascorbic acid (DHAA). Consequently, an ALP activity-dependent RF response was achieved by coupling with the condensation reaction between OPD and the DHAA, which yields fluorescent 3-(1,2-dihydroxy ethyl) furo[3,4-b] quinoxalin-1(3 H)-on with the maximum emission at 430 nm. Using the anti-STX polyclonal antibody and the commercial ALP-labelled secondary antibody as the recognition unit and signal transducing module, an ultrasensitive and accurate RF-ELISA for STX was developed with a detection limit of 3.2 pg/mL, which was 12-fold more sensitive than that of classic colorimetric ELISA. This work opened up new ways for ultrasensitive and accurate detection of STX and other analytes in food safety supervision.

Detection of saxitoxin by a SERS aptamer sensor based on enzyme cycle amplification technology.

Saxitoxin (STX) is a typical toxic guanidinium neurotoxin, one of the paralytic shellfish poisons (PSP), which poses a serious threat to human health. In this paper, a simple and sensitive SERS aptamer sensor (abbreviated as AuNP@4-NTP@SiO2) for the quantitative determination of STX was developed. Hairpin aptamers of saxitoxin are modified on magnetic beads and used as recognition elements. In the presence of STX, DNA ligase, and the rolling circle template (T1), a rolling circle amplification reaction was triggered to produce long single-stranded DNA containing repetitive sequences. The sequence can be hybridized with the SERS probe to realize the rapid detection of STX. Due to the inherent merits of its components, the obtained AuNP@4-NTP@SiO2 SERS aptamer sensor manifests excellent sensing performance for STX detection with a wide linear range from 2.0 × 10-10 mol L-1 to 5.0 × 10-4 mol L-1 and a lower detection limit of 1.2 × 10-11 mol L-1. This SERS sensor can provide a strategy for the micro-detection of other biological toxins by changing the aptamer sequence.

A Label-Free Colorimetric Aptasensor Containing DNA Triplex Molecular Switch and AuNP Nanozyme for Highly Sensitive Detection of Saxitoxin

A Label-Free Colorimetric Aptasensor Containing DNA Triplex Molecular Switch and AuNP Nanozyme for Highly Sensitive Detection of Saxitoxin

Label-Free Detection of Saxitoxin with Field-Effect Device-Based Biosensor.

Saxitoxin (STX) is a highly toxic and widely distributed paralytic shellfish toxin (PSP), posing a serious hazard to the environment and human health. Thus, it is highly required to develop new STX detection approaches that are convenient, desirable, and affordable. This study presented a label-free electrolyte-insulator-semiconductor (EIS) sensor covered with a layer-by-layer developed positively charged Poly (amidoamine) (PAMAM) dendrimer. An aptamer (Apt), which is sensitive to STX was electrostatically immobilized onto the PAMAM dendrimer layer. This results in an Apt that is preferably flat inside a Debye length, resulting in less charge-screening effect and a higher sensor signal. Capacitance-voltage and constant-capacitance measurements were utilized to monitor each step of a sensor surface variation, namely, the immobilization of PAMAM dendrimers, Apt, and STX. Additionally, the surface morphology of PAMAM dendrimer layers was studied by using atomic force microscopy and scanning electron microscopy. Fluorescence microscopy was utilized to confirm that Apt was successfully immobilized on a PAMAM dendrimer-modified EIS sensor. The results presented an aptasensor with a detection range of 0.5–100 nM for STX detection and a limit of detection was 0.09 nM. Additionally, the aptasensor demonstrated high selectivity and 9-day stability. The extraction of mussel tissue indicated that an aptasensor may be applied to the detection of STX in real samples. An aptasensor enables marine toxin detection in a rapid and label-free manner.

Electrochemical biosensor with aptamer/porous platinum nanoparticle on round-type micro-gap electrode for saxitoxin detection in fresh water

Cyanotoxins are toxins produced by cyanobacteria; they negatively impact water resources used by humans and disrupt ecosystems worldwide. Among cyanotoxins, saxitoxin (STX) is a small molecule that causes paralysis in humans and contamination in freshwater resources. To monitor low concentration of STX levels, a sensitive and high fidelity detection system is required. In this study, a round-type micro-gap electrode (RMGE) was fabricated that provides the high signal fidelity for STX detection in real freshwater sample. The RMGE has the 15 pairs of identical electrode wire length between gap that gives the high signal fidelity. In addition, the sensitivity for STX detection was improved by introducing the porous platinum nanoparticle (pPtNP) that enahced the electrochemical sensitivity and the STX aptamer was used as the bioprobe. An electrochemical measurement method (square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS)) was introduced to construct STX biosensor. To evaluate the biosensor performance, the limit of detection (LOD) and selectivity test were performed on real freshwater samples. The biosensor demonstrated high selectivity even in freshwater samples over a wide linear concentration range of 10 pg/mL to 1 μg/mL and a detection limit of 4.669 pg/mL. These results suggest that the designed biosensor shows a wide range of possibilities for the detection of toxicants in freshwater that provide the new direction to the biosensor electrode design.

An electrochemical PAH-modified aptasensor for the label-free and highly-sensitive detection of saxitoxin.

Saxitoxin (STX), is one of the most dangerous and widespread paralytic shellfish toxins, causing a severe threat to the ecosystem and human health. So, it is important and highly essential to develop novel techniques for STX detection in a convenient, desirable, and low-cost manner. Herein, this study developed an electrolyte-insulator-semiconductor (EIS) sensor covered with a layer-by-layer prepared, positively-charged weak polyelectrolyte layer of poly (allylamine hydrochloride) (PAH) for the label-free detection of STX. The specific aptamer (Apt) sensitive to STX was electrostatically adsorbed onto the PAH layer. This leads to a preferentially flat orientation of the Apt within the Debye length, thus yielding a reduced charge-screening influence and a higher sensor signal. Each step of sensor surface modification, i.e. PAH adsorption, immobilization of Apt, and attachment of STX, was monitored by capacitance-voltage (C-V) and constant-capacitance (ConCap) measurements. Furthermore, atomic force microscopy (AFM) was employed to characterize the surface morphology and roughness of the PAH layer. Fluorescence microscopy was used to confirm the effective immobilization of Apt onto the PAH-modified EIS sensor. The results showed that the detection range of this aptasensor for STX detection was 0.5-100nM and the detection limit was as low as 0.05nM. Furthermore, this aptasensor showed good selectivity and 9 days' stability. The mussel tissue extraction test suggested that this aptasensor can be used to detect STX in real samples. This aptasensor provides a convenient approach for moderate, rapid, and label-free detection of marine biological toxins.