A novel electrochemical immunosensor for highly sensitive detection of aflatoxin B1 in corn using single-walled carbon nanotubes/chitosan

Boron-doped diamond electrochemical aptasensors for trace aflatoxin B1 detection

An electrochemical aptasensor for detecting trace aflatoxin B₁ (AFB₁) is designed and fabricated consisting of aptamers and gold nanoparticles on conductive boron-doped diamond (BDD) electrode. By examining the relative impedance shift from electrochemical impedance spectroscopy as a function of AFB₁ concentration, the low detection limit (wide linear relationship range) of the aptasensor is realized to be 5.5 × 10^-14 mol L^-1 (1.0 × 10^-13‒1.0 × 10^-8 mol L^-1). The variation in impedance property of the aptasensor is determined by the specific adsorption of AFB₁ molecules to the aptamer at a certain concentration covering the electrode. By means of multiple characteristic processes, it is demonstrated that the constructed aptasensor is favorable for testing the trace AFB₁ with high specificity, sensitivity, stability, repeatability, and reusability, which lead to a possibility to achieve high performance biosensor for practical application to quantitatively detract trace AFB₁ in environments.

Advances in Analysis and Detection of Major Mycotoxins in Foods

Mycotoxins are the most widely studied biological toxins, which contaminate foods at very low concentrations. This review describes the emerging extraction techniques and the current and alternatives analytical techniques and methods that have been used to successfully detect and identify important mycotoxins. Some of them have proven to be particularly effective in not only the detection of mycotoxins, but also in detecting mycotoxin-producing fungi. Chromatographic techniques such as high-performance liquid chromatography coupled with various detectors like fluorescence, diode array, UV, liquid chromatography coupled with mass spectrometry, and liquid chromatography-tandem mass spectrometry, have been powerful tools for analyzing and detecting major mycotoxins. Recent progress of the development of rapid immunoaffinity-based detection techniques such as immunoassays and biosensors, as well as emerging technologies like proteomic and genomic methods, molecular techniques, electronic nose, aggregation-induced emission dye, quantitative NMR and hyperspectral imaging for the detection of mycotoxins in foods, have also been presented.

Sensitivity programmable ratiometric electrochemical aptasensor based on signal engineering for the detection of aflatoxin B1 in peanut

Accurately monitoring of aflatoxin B1 (AFB1), the most hazardous mycotoxin in agricultural products, is essential for the public health, but various testing demands (e.g. detection range, sensitivity) for different samples can be challenging for sensors. Here, we developed a sensitivity-programmable ratiometric electrochemical aptasensor for AFB1 analysis in peanut. Thionine functionalized reduced graphene oxide (THI-rGO) served as reference signal generator, ferrocene-labelled aptamer (Fc-apt) output the response signal. During analysis, the formation of Fc-apt-AFB1 complex led to its stripping from the electrode and faded the current intensity of Fc (I_Fc), while the current intensity of THI (I_THI) was enhanced. And ratiometric detection of AFB1 was achieved by using the current intensity ratio (I_THI/I_Fc) as quantitative signal. Compared with ratiometric strategies that highly rely on the labelled aptamers, the proposed strategy could regulate the value of I_THI/I_Fc by changing the modification of Fc-apt. And the detection sensitivity was found to be closely related to I_THI/I_Fc. Under the optimal conditions, the fabricated aptasensor with a dynamic range from 0.05-20 ng mL^-1 and a detection limit of 0.016 ng mL^-1 for AFB1 analysis. Besides, it exhibited excellent selectivity, reliability and reproducibility. The proposed sensitivity-programmable biosensor can be applied to detect various aptamer-recognized mycotoxins in agricultural sensing.

Functional nanomaterials based immunological detection of aflatoxin B1: a review

Aflatoxin B1 (AFB1) is highly carcinogenic, mutagenic and teratogenic. Accordingly, sensitive, rapid and cost-effective techniques for detection of AFB1 is in urgent demand for food safety and the health of consumers. In this review, we report the current state of immunoassay formats and development, mainly based on nanomaterials for determination of AFB1. Following an introduction of the field, the microplate-, membrane- and microelectrode-based immunoassays are described. The relevant mechanisms, sensitivities, superiorities and deficiencies of each format are discussed. Finally, perspectives on the future development of nanomaterials-based immunoassays for AFB1 are provided.

Electrochemical biosensors: perspective on functional nanomaterials for on-site analysis

BACKGROUND

The electrochemical biosensor is one of the typical sensing devices based on transducing the biochemical events to electrical signals. In this type of sensor, an electrode is a key component that is employed as a solid support for immobilization of biomolecules and electron movement. Thanks to numerous nanomaterials that possess the large surface area, synergic effects are enabled by improving loading capacity and the mass transport of reactants for achieving high performance in terms of analytical sensitivity.

MAIN BODY

We categorized the current electrochemical biosensors into two groups, carbon-based (carbon nanotubes and graphene) and non-carbon-based nanomaterials (metallic and silica nanoparticles, nanowire, and indium tin oxide, organic materials). The carbon allotropes can be employed as an electrode and supporting scaffolds due to their large active surface area as well as an effective electron transfer rate. We also discussed the non-carbon nanomaterials that are used as alternative supporting components of the electrode for improving the electrochemical properties of biosensors.

CONCLUSION

Although several functional nanomaterials have provided the innovative solid substrate for high performances, developing on-site version of biosensor that meets enough sensitivity along with high reproducibility still remains a challenge. In particular, the matrix interference from real samples which seriously affects the biomolecular interaction still remains the most critical issues that need to be solved for practical aspect in the electrochemical biosensor.

Electrochemical immunosensor based on carboxylated single-walled carbon nanotube-chitosan functional layer for the detection of cephalexin

In this study, a sensitive and selective electrochemical immunosensor for cephalexin (CEX) determination on a glassy carbon electrode (GCE) surface was modified by a carboxylated single-walled carbon nanotubes/chitosan (SWNTs-COOH/CS) composite. The SWNTs-COOH/CS composite was used to enhance sensor performance and to enlarge the electrochemical response of CEX. The cephalosporin-ovalbumin coupling (CEX-OVA) was synthesized using the reactive ester method. The free CEX in solution could be effectively measured based on the competitive immunoreaction between CEX-antibody and CEX. Under optimal conditions, the electrochemical immunosensor offered an excellent response for CEX. The linear range was 1-800 ng/ml, with a detection limit of 45.7 ng/ml (S/N = 3). This method was applied to determine CEX in six different samples and obtained the recovery range from 80.15% to 94.04%. These results indicated that the fabricated electrochemical immunosensor and sensing method are suitable for quantification of CEX in real samples. These have great potential for wider applications in environmental and agri-food products industries.

Label-Free Electrochemical Immunosensor Based on β-Cyclodextrin-Functionalized Helical Carbon Nanotube and Ionic Liquid Containing Ferrocene and Aldehyde Groups

We fabricated an electrochemical immunosensor for the detection of cardiac troponin I using β-cyclodextrin-functionalized helical carbon nanotube and ionic liquid functionalized with ferrocene and aldehyde groups. β-Cyclodextrin-functionalized helical carbon nanotube was first modified on the electrode surface. Then, ferrocene- and aldehyde-functionalized ionic liquid was modified on the surface of the electrode through host-guest interaction, resulting in an interface with aldehyde groups. The aldehyde groups attached to the ionic liquid capture antibody directly, which simplifies the fabrication of immunosensor. Because of the use of ionic liquid and helical carbon nanotube, the conductivity of the sensing interface was improved. Thus, the sensitivity of the fabricated immunosensor was increased. The immunosensor for cardiac troponin I shows a linear range from 0.05 to 20 ng mL^-1 with a detection limit of 0.04 ng mL^-1 (S/N = 3).

Detection of potential biomarkers associated with outrageous diseases and environmental pollutants by nanoparticle-based immuno-PCR assays

Immuno-polymerase chain reaction (I-PCR) assay with advantages of both enzyme-linked immunosorbent assay (ELISA) and PCR exhibits several-fold enhanced sensitivity in comparison to respective ELISA, which has wide applications for ultralow detection of several molecules, i.e. cytokines, protooncogenes and biomarkers associated with several diseases. Conjugation of reporter DNA to the detection antibodies is the most crucial step of I-PCR assay that usually employs streptavidin-protein A, streptavidin-biotin conjugate or succinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxylate (SMCC) system by a covalent binding. However, coupling of antibodies and oligonucleotides to nanoparticles (NPs) is relatively easier in the NP-based I-PCR (NP-I-PCR) that also displays better accuracy. This article is mainly focused on the detection of important biomarkers associated with several outrageous infectious and non-infectious diseases by NP-I-PCR assays, which would expedite an early initiation of therapy thus human health would be improved. Similarly, ultralow detection of environmental pollutants by these assays and their elimination would certainly improve human health.

Advances in biosensors for the detection of ochratoxin A: Bio-receptors, nanomaterials, and their applications

Ochratoxin A (OTA) is a class of mycotoxin mainly produced by the genera Aspergillus and Penicillium. OTA can cause various forms of kidney, liver and brain diseases in both humans and animals although trace amount of OTA is normally present in food. Therefore, development of fast and sensitive detection technique is essential for accurate diagnosis of OTA. Currently, the most commonly used detection methods are enzyme-linked immune sorbent assays (ELISA) and chromatographic techniques. These techniques are sensitive but time consuming, and require expensive equipment, highly trained operators, as well as extensive preparation steps. These drawbacks limit their wide application in OTA detection. On the contrary, biosensors hold a great potential for OTA detection at for both research and industry because they are less expensive, rapid, sensitive, specific, simple and portable. This paper aims to provide an extensive overview on biosensors for OTA detection by highlighting the main biosensing recognition elements for OTA, the most commonly used nanomaterials for fabricating the sensing interface, and their applications in different read-out types of biosensors. Current challenges and future perspectives are discussed as well.

Prevalent Mycotoxins in Animal Feed: Occurrence and Analytical Methods

Today, we have been witnessing a steady tendency in the increase of global demand for maize, wheat, soybeans, and their products due to the steady growth and strengthening of the livestock industry. Thus, animal feed safety has gradually become more important, with mycotoxins representing one of the most significant hazards. Mycotoxins comprise different classes of secondary metabolites of molds. With regard to animal feed, aflatoxins, fumonisins, ochratoxins, trichothecenes, and zearalenone are the more prevalent ones. In this review, several constraints posed by these contaminants at economical and commercial levels will be discussed, along with the legislation established in the European Union to restrict mycotoxins levels in animal feed. In addition, the occurrence of legislated mycotoxins in raw materials and their by-products for the feeds of interest, as well as in the feeds, will be reviewed. Finally, an overview of the different sample pretreatment and detection techniques reported for mycotoxin analysis will be presented, the main weaknesses of current methods will be highlighted.

Recent development in chitosan nanocomposites for surface-based biosensor applications

Recent years have witnessed ever expanding use of biosensors in the fields of environmental monitoring, homeland security, pharmaceutical, food and bioprocessing, and agricultural industries. To produce effective and reliable biosensors, good quality immobilization of biological recognition elements is critical. Chitosan and its nanocomposites emerge as an excellent immobilization matrix on biosensor surface. As a natural polysaccharide, chitosan has many useful characteristics, such as high permeability and mechanical strength, biocompatibility and non-toxicity, availability, and low cost. Due to the presence of amino and hydroxyl groups on chitosan, chitosan can easily crosslink with a variety of nanomaterials. This investigation of chitosan nanocomposite-based biosensors presents recent development and innovations in the preparation of chitosan nanocomposites in coordination with biosensors for various bio-detection applications, including chitosan nanocomposites formed with carbon nanomaterials, various inorganic and biological complexes. These chitosan nanocomposite based biosensors have demonstrated good sensitivity selectivity and stability for the detection of different types of targets ranging from glucose, proteins, DNAs, small biomolecules to bacteria. It is in our hope that this review will offer guidance for the development of novel biosensors and open up opportunities in the field of biosensor research.

A novel fluorescence aptasensor based on mesoporous silica nanoparticles for selective and sensitive detection of aflatoxin B1

Based on the mesoporous silica nanoparticles (MSN), a novel, simple and label-free aptamer biosensor was designed for the detection of aflatoxin B₁ (AFB₁). Here, the aptamers were used as molecular recognition probes and "gated molecules" while Rh6G was loaded into the interior of the particles as the signal probe. In the absence of AFB₁, the "gate" was closed to prevent the leakage of the signal probe because of the immobilization of aptamers on the surface of MSN-NH₂. With the presence of AFB₁, the "gate" could be opened to release the signal probe for the specifical binding of aptamers to AFB₁. Our results showed that the fluorescence intensity was positively correlated with the concentration of AFB₁ (0.5-50 ng mL^-1), with the detection limit as low as 0.13 ng mL^-1. What's more, this design provides a new approach for rapid, sensitive and selective detection based on aptamers and it could be applied to numerous other analytes if appropriate aptamers are available.

Construction of Electrochemical Immunosensor Based on Gold-Nanoparticles/Carbon Nanotubes/Chitosan for Sensitive Determination of T-2 Toxin in Feed and Swine Meat

T-2 toxin (T-2) is one of major concern mycotoxins acknowledged as an unavoidable contaminant in human foods, animal feeds and also agriculture products. Thus, a facile and sensitive method is essential for accurate T-2 toxin detection. In our work, a specific electrochemical immunosensor based on gold nanoparticles/carboxylic group-functionalized single-walled carbon nanotubes/chitosan (AuNPs/cSWNTs/CS) composite was established. The mechanism of the electrochemical immunosensor was an indirect competitive binding to a given amount of anti-T-2 between free T-2 and T-2-bovine serum albumin, which was conjugated on covalently functionalized cSWNTs decorated on the glass carbon electrode. Afterwards, the alkaline phosphatase labeled anti-mouse secondary antibody was bound to the electrode surface by reacting with the primary antibody. Lastly, alkaline phosphatase catalyzed the hydrolysis of the substrate α-naphthyl phosphate, which produced an electrochemical signal. Compared with conventional methods, the established immunosensor was more sensitive and simpler. Under optimal conditions, this method could quantitatively detect T-2 from 0.01 to 100 μg·L-1 with a detection limit of 0.13 μg·L-1 and favorable recovery 91.42⁻102.49%. Moreover, the immunosensor was successfully applied to assay T-2 in feed and swine meat, which showed good correlation with the results obtained from liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Target-driven switch-on fluorescence aptasensor for trace aflatoxin B1 determination based on highly fluorescent ternary CdZnTe quantum dots

Development of sensitive methods for trace aflatoxin B1 (AFB1) determination is of great significance due to its high toxicity and carcinogenicity. Herein, 3-mercaptopropionic acid (MPA)-capped ternary CdZnTe quantum dots (QDs) have been prepared via a simple hydrothermal route. We found that they exhibited enhanced intensity when benchmarked against their binary counterpart CdTe QDs. On this basis, a target-driven switch-on fluorescence aptasensor for trace AFB1 determination has been developed by employing the fluorescence resonance energy transfer (FRET) between the CdZnTe QDs and Au nanoparticles (AuNPs) pair. In the detection diagram, amino group-functionalized aptamers against AFB1 were firstly labelled with the CdZnTe QDs donors coated on silica nanospheres while the AuNPs acceptors were bioconjugated with the thiol group-modified complementary DNA (cDNA) of aptamer. By taking advantage of the DNA hybridization of aptamer and cDNA, the CdZnTe QDs (energy donor) and AuNPs (energy acceptor) were brought into close proximity, thereby leading to the occurrence of FRET during the aptasensor fabrication. When the aptasensor was incubated with AFB1, the specific binding between aptamer and target resulted in the detachment of AuNPs acceptors. This behavior would disturb the FRET process and led to the subsequent fluorescence recovery of CdZnTe QDs. Such designed aptasensor showed an increased fluorescence recovery upon the increasing concentration of AFB1 over a broad range of 50 pg mL^-1 - 100 ng mL^-1 and succeeded in spiked peanut samples. The proposed aptasensor is separation-free and easy-to-use, which might open up new possibilities in aptasensor fabrication by employing the novel CdZnTe QDs-AuNPs pair.

Progress on nanostructured electrochemical sensors and their recognition elements for detection of mycotoxins: A review

Nanomaterial-embedded sensors have been developed and applied to monitor various targets. Mycotoxins are fungal secondary metabolites that can exert carcinogenic, mutagenic, teratogenic, immunotoxic, and estrogenic effects on humans and animals. Consequently, the need for the proper regulation on foodstuff and feed materials has been recognized from times long past. This review provides an overview of recent developments in electrochemical sensors and biosensors employed for the detection of mycotoxins. Basic aspects of the toxicity of mycotoxins and the implications of their detection are comprehensively discussed. Furthermore, the development of different molecular recognition elements and nanomaterials required for the detection of mycotoxins (such as portable biosensing systems for point-of-care analysis) is described. The current capabilities, limitations, and future challenges in mycotoxin detection and analysis are also addressed.

Electrochemical Immunosensor for Detection of Aflatoxin B₁ Based on Indirect Competitive ELISA

Mycotoxins are the secondary toxic metabolites produced naturally by fungi. Analysis of mycotoxins is essential to minimize the consumption of contaminated food and feed. In this present work, an ultrasensitive electrochemical immunosensor for the detection of aflatoxin B₁ (AFB₁) was successfully developed based on an indirect competitive enzyme-linked immunosorbent assay (ELISA). Various parameters of ELISA, including antigen⁻antibody concentration, blocking agents, incubation time, temperature and pH of reagents, were first optimized in a 96-well microtiter plate to study the antigen⁻antibody interaction and optimize the optimum parameters of the assay. The optimized assay was transferred onto the multi-walled carbon nanotubes/chitosan/screen-printed carbon electrode (MWCNTs/CS/SPCE) by covalent attachment with the aid of 1-Ethyl-3-(3-dimetylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS). Competition occurred between aflatoxin B₁-bovine serum albumin (AFB₁⁻BSA) and free AFB₁ (in peanut sample and standard) for the binding site of a fixed amount of anti-AFB₁ antibody. Differential pulse voltammetry (DPV) analysis was used for the detection based on the reduction peak of TMB(ox). The developed immunosensor showed a linear range of 0.0001 to 10 ng/mL with detection limit of 0.3 pg/mL. AFB₁ analysis in spiked peanut samples resulted in recoveries between 80% and 127%. The precision of the developed immunosensor was evaluated by RSD values (n = 5) as 4.78% and 2.71% for reproducibility and repeatability, respectively.

Dual-competitive lateral flow aptasensor for detection of aflatoxin B1 in food and feedstuffs

A novel dual-competitive lateral flow aptasensor (LFA) benefited from aptamer and lateral flow strips was first designed by using aflatoxin B₁ (AFB₁) as the model target. In this LFA assay, the target AFB₁ competed with AFB₁-hapten at T line for binding to Cy5-labeled AFB₁ aptamer and the complementary strand competed with the target AFB₁ for binding to Cy5-labeled AFB₁ aptamer at C line. The ratio of their fluorescent intensities at the T line and C line (ST/SC ratio) was employed in order to increase the sensitivity for target AFB₁ detection. This technique has the limit of detection (LOD) of 0.1ng/mL for AFB₁ within the linear range from 0.1ng/mL to 1000ng/mL. Subsequently, the LFA approach was validated using 11 kinds of food and feedstuff samples with a simple aqueous extraction protocol. The test results with different naturally contaminated feedstuffs indicated a good correlation between this LFA and a commercial ELISA kit. The assay can be completed within 20min and its sensitivity, specificity and reproducibility are highly satisfactory. This is the first LFA that has been rigorously validated, which will be greatly beneficial to development of commercial aptamer-based biosensors for food safety, environmental analysis, particularly in clinical diagnosis.

Electrochemical Immunosensor for the Detection of Aflatoxin B₁ in Palm Kernel Cake and Feed Samples

Palm kernel cake (PKC) is the solid residue following oil extraction of palm kernels and useful to fatten animals either as a single feed with only minerals and vitamins supplementation, or mixed with other feedstuffs such as corn kernels or soy beans. The occurrence of mycotoxins (aflatoxins, ochratoxins, zearalenone, and fumonisins) in feed samples affects the animal's health and also serves as a secondary contamination to humans via consumption of eggs, milk and meats. Of these, aflatoxin B₁ (AFB₁) is the most toxically potent and a confirmed carcinogen to both humans and animals. Methods such as High Performance Liquid Chromatography (HPLC) and Liquid Chromatography-Mass Spectrometry (LC-MS/MS) are common in the determination of mycotoxins. However, these methods usually require sample pre-treatment, extensive cleanup and skilled operator. Therefore, in the present work, a rapid method of electrochemical immunosensor for the detection of AFB₁ was developed based on an indirect competitive enzyme-linked immunosorbent assay (ELISA). Multi-walled carbon nanotubes (MWCNT) and chitosan (CS) were used as the electrode modifier for signal enhancement. N-ethyl-N'-(3-dimethylaminopropyl)-carbodiimide (EDC) and N-hydroxysuccinimide (NHS) activated the carboxyl groups at the surface of nanocomposite for the attachment of AFB₁-BSA antigen by covalent bonding. An indirect competitive reaction occurred between AFB₁-BSA and free AFB₁ for the binding site of a fixed amount of anti-AFB₁ antibody. A catalytic signal based on horseradish peroxidase (HRP) in the presence of hydrogen peroxide (H₂O₂) and 3,3',5,5'-tetramethylbenzidine (TMB) mediator was observed as a result of attachment of the secondary antibody to the immunoassay system. As a result, the reduction peak of TMB_(Ox) was measured by using differential pulse voltammetry (DPV) analysis. Based on the results, the electrochemical surface area was increased from 0.396 cm² to 1.298 cm² due to the electrode modification with MWCNT/CS. At the optimal conditions, the working range of the electrochemical immunosensor was from 0.0001 to 10 ng/mL with limit of detection of 0.1 pg/mL. Good recoveries were obtained for the detection of spiked feed samples (PKC, corn kernels, soy beans). The developed method could be used for the screening of AFB₁ in real samples.

A sensitive and rapid immunoassay for Mycoplasma pneumoniae in children with pneumonia based on single-walled carbon nanotubes

Mycoplasma pneumoniae(MP) is a leading pathogen of respiratory infection, especially community-acquired pneumonia (CAP), in children worldwide. However, its diagnosis is frequently ineffective because bacterial culture and serology test are usually positive 1–2 weeks or more after the disease onset. To achieve a better detection efficiency, the single-walled carbon nanotubes(SWCNT) were coupled with the colloidal gold-monoclonal antibody immunochromatographic strips(CGIC). Interestingly, the SWCNT/CGIC assay allowed MP identification, with a detection limit of 1 × 10² copies/ml. Using referenced throat swabs of 97 MP and 40 non-MP cases, the assay yielded 72.2% sensitivity, 100.0% specificity, 100.0% positive predictive value (PPV), 59.7% negative predictive value (NPV). In summary, our assay was far more effective than any conventional methods for the diagnosis of acute MP. The ease of use, rapid and stability further enhance its feasibility for clinical use on-site.

Recent Advances in Electrochemical Immunosensors

Immunosensors have experienced a very significant growth in recent years, driven by the need for fast, sensitive, portable and easy-to-use devices to detect biomarkers for clinical diagnosis or to monitor organic pollutants in natural or industrial environments. Advances in the field of signal amplification using enzymatic reactions, nanomaterials such as carbon nanotubes, graphene and graphene derivatives, metallic nanoparticles (gold, silver, various oxides or metal complexes), or magnetic beads show how it is possible to improve collection, binding or transduction performances and reach the requirements for realistic clinical diagnostic or environmental control. This review presents these most recent advances; it focuses first on classical electrode substrates, then moves to carbon-based nanostructured ones including carbon nanotubes, graphene and other carbon materials, metal or metal-oxide nanoparticles, magnetic nanoparticles, dendrimers and, to finish, explore the use of ionic liquids. Analytical performances are systematically covered and compared, depending on the detection principle, but also from a chronological perspective, from 2012 to 2016 and early 2017.

FRET-based aptamer biosensor for selective and sensitive detection of aflatoxin B1 in peanut and rice

Aflatoxins are potential food pollutants produced by fungi. Among them, Aflatoxin B1 (AFB1) is the most toxic. Therefore, a great deal of concern is associated with AFB1 toxicity. In this work, utilizing a FRET-based method, we have developed a nanobiosensor for detection of AFB1 in agricultural foods. Aptamer-conjugated Quantum dots (QDs) are adsorbed to Au nanoparticles (AuNPs) due to interaction of aptamers with AuNPs leading to quenching effect on QDs fluorescence. Upon the addition of AFB1, the specific aptamers are attracted to AFB1, getting distance from AuNPs which result in fluorescence recovery. Under optimized conditions the detection limit of proposed nanobiosensor was 3.4nM with linear range of 10-400nM. Selectivity test demonstrates that the nanobiosensor could be a promising tool for specific evaluation of food stuff. This method was successfully applied for the analysis of AFB1 in rice and peanut samples.

A simple aptamer-based fluorescent assay for the detection of Aflatoxin B1 in infant rice cereal

A fluorescent assay for the rapid, sensitive and specific detection of Aflatoxin B1 (AFB1) was developed in this study. Initially, a DNA/DNA duplex was formed between a fluorescein-labeled AFB1 aptamer and its partially complementary DNA strand containing a quencher moiety, resulting in fluorescence quenching due to the close proximity of fluorophore and quencher. Upon the addition of AFB1, an aptamer/AFB1 complex was generated to release the quencher-modified DNA strand, thus recovered the fluorescence of fluorescein and enabled quantitative detection for AFB1 by monitoring fluorescence enhancement. Under optimized conditions, this assay exhibited a linear response to AFB1 in the range of 5-100ng/mL with a detection limit down to 1.6ng/mL. Trials of this assay in infant rice cereal with satisfactory recovery in the range of 93.0%-106.8%, demonstrate that the new assay could be a potential sensing platform for AFB1 determination in food.

An electrochemical immunosensor for quantitative detection of ficolin-3

Diabetes mellitus (DM) is one of the most common metabolic disorders in the world, of which more than 90% is type-2 diabetes mellitus (T2DM). There is a rather urgent need for reliable, sensitive and quick detection techniques in clinical application of T2DM. Ficolin-3 is a potential biomarker of T2DM, because serum ficolin-3 levels are associated with insulin resistance and predict the incidence of T2DM. Herein, a sandwich-type electrochemical immunosensor was developed for the detection of ficolin-3 in human serum. Cyclic voltammetry and the amperometric current versus time were used to characterize the performance of the immunosensor. Under optimal conditions, the detection limitation of ficolin-3 was 100 ng ml(-1) and the linear dynamic range was between 2 and 50 μg ml(-1). The method has ideal accuracy, excellent stability and selectivity and has wide application prospects in clinical research.