Multifunctionalized reduced graphene oxide-doped polypyrrole/pyrrolepropylic acid nanocomposite impedimetric immunosensor to ultra-sensitively detect small molecular aflatoxin B1

Progress on Electrochemical Biomimetic Nanosensors for the Detection and Monitoring of Mycotoxins and Pesticides

Monitoring agricultural toxins such as mycotoxins is crucial for a healthy society. High concentrations of these toxins lead to the cause of several chronic diseases; therefore, developing analytical systems for detecting/monitoring agricultural toxins is essential. These toxins are found in crops such as vegetables, fruits, food, and beverage products. Currently, screening of these toxins is mostly performed with sophisticated instrumentation such as chromatography and spectroscopy techniques. However, these techniques are very expensive and require extensive maintenance, and their availability is limited to metro cities only. Alternatively, electrochemical biomimetic sensing methodologies have progressed hugely during the last decade due to their unique advantages like point-of-care sensing, miniaturized instrumentations, and mobile/personalized monitoring systems. Specifically, affinity-based sensing strategies including immunosensors, aptasensors, and molecular imprinted polymers offer tremendous sensitivity, selectivity, and stability to the sensing system. The current review discusses the principal mechanisms and the recent developments in affinity-based sensing methodologies for the detection and continuous monitoring of mycotoxins and pesticides. The core discussion has mainly focused on the fabrication protocols, advantages, and disadvantages of affinity-based sensing systems and different exploited electrochemical transduction techniques.

Recent Advances in Recognition Receptors for Electrochemical Biosensing of Mycotoxins-A Review

Mycotoxins are naturally occurring toxic secondary metabolites produced by fungi in cereals and foodstuffs during the stages of cultivation and storage. Electrochemical biosensing has emerged as a rapid, efficient, and economical approach for the detection and quantification of mycotoxins in different sample media. An electrochemical biosensor consists of two main units, a recognition receptor and a signal transducer. Natural or artificial antibodies, aptamers, molecularly imprinted polymers (MIP), peptides, and DNAzymes have been extensively employed as selective recognition receptors for the electrochemical biosensing of mycotoxins. This article affords a detailed discussion of the recent advances and future prospects of various types of recognition receptors exploited in the electrochemical biosensing of mycotoxins.

Advances in functional photonic crystal materials for the analysis of chemical hazards in food

Chemical contaminants in food generally include natural toxins (mycotoxins, animal toxins, and phytotoxins), pesticides, veterinary drugs, environmental pollutants, heavy metals, and illegal additives. Developing a low-cost, simple, and rapid detection technology for harmful substances in food is urgently needed. Analytical methods based on different advanced materials have been developed into rapid detection methods for food samples. In particular, photonic crystal (PC) materials have a unique surface periodic structure, structural color, a large surface area, easy integration with photoelectronic and magnetic devices which have great advantages in the development of rapid, low-cost, and highly sensitive analytical methods. This review focuses on the PC materials in the view of their fabrication processes, functionalized recognition components for the specific recognition of hazardous substances, and applications in the separation, enrichment, and detection of chemical hazards in real samples. Suspension array based on three-dimensional PC microspheres by droplet-based microfluidic assembly is a great promising and powerful platform for food safety detection fields. For the PCs selective analysis, biological antibodies, aptamers, and molecularly imprinted polymers (MIPs) could be modified for specific recognition of target substances, particularly MIPs because of their low-cost and easy mass production. Based on these functional PCs, various toxic and hazardous substances can be selectively enriched or recognized in real samples and further quantified in combination of liquid chromatography method or optical detection methods including fluorescence, chemiluminescence, and Raman spectroscopy.

Nanoarchitectonics of graphene based sensors for food safety monitoring

Since the desire for the real-time food quality monitoring, plenty of research effort has been made to develop novel tools and to offer extremely efficient detection of food contaminants. Unique electrical, mechanical, and thermal properties make graphene an important material in the field of sensor research. The material can be manufactured into flakes, sheets, films and with its oxidized derivatives could be almost used for a limitless set of application. Herein, current graphene-based sensors for food quality monitoring, novel designs, sensing mechanisms and elements of sensor systems and potential challenges will be outlined and discussed.

A sensitive electrochemical immunosensing interface for label-free detection of aflatoxin B1 by attachment of nanobody to MWCNTs-COOH@black phosphorene

A label-free electrochemical immunosensor has advantages of real-time and rapid detection, but it is weak in detection of small molecular toxins such as aflatoxin B₁ (AFB₁). The greatest obstacle to achieving this is that small molecules bound to a common immunosensing interface cannot interfere with electron transfer effectively and the detection signal is so weak. Therefore, a sensitive electrochemical immunosensing interface for small molecules is urgently needed. Here, we employed functionalized black phosphorene (BP) as electrode modification materials and anti-AFB₁ nanobody (Nb) as a biorecognition element to construct a very sensitive immunosensing interface towards small molecular AFB₁. The BP functionalized by carboxylic multi-walled carbon nanotubes (MWCNTs-COOH) via P-C bonding behaved with a satisfactory stability and good catalytic performance for the ferricyanide/ferrocyanide probe, while the small-sized Nb showed good compatibility with the functionalized BP and also had less influence on electron transfer than monoclonal antibody (mAb). Expectedly, the as-prepared immunosensing interface was very sensitive to AFB₁ detection by differential pulse voltammetry (DPV) in a redox probe system. Under optimized conditions, a linear range from 1.0 pM to 5.0 nM and an ultralow detection limit of 0.27 pM were obtained. Additionally, the fabricated immunosensor exhibited satisfactory stability, specificity, and reproducibility. The strategy proposed here provides a more reliable reference for label-free sensing of small molecules in food samples.

Polypyrrole-palladium nanocomposite as a high-efficiency transducer for thrombin detection with liposomes as a label

Sensitive and selective determination of protein biomarkers with high accuracy often remains a great challenge due to their existence in the human body at an exceptionally low concentration level. Therefore, sensing mechanisms that are easy to use, simple, and capable of accurate quantification of analyte are still in development to detect biomarkers at a low concentration level. To meet this end, we demonstrated a methodology to detect thrombin in serum at low concentration levels using polypyrrole (PPy)-palladium (Pd)nanoparticle-based hybrid transducers using liposomes encapsulated redox marker as a label. The morphology of Ppy-Pd composites was characterized by scanning electron microscopy, and the hybrid structure provided excellent binding and detection platform for thrombin detection in both buffer and serum solutions. For quantitative measurement of thrombin in PBS and serum, the change in current was monitored using differential pulse voltammetry, and the calculated limit of quantification (LOQ) and limit of detection (LOD) for the linear segment (0.1-1000 nM of thrombin) were 1.1 pM and 0.3 pM, in serum, respectively. The sensors also exhibited good stability and excellent selectivity towards the detection of thrombin, and thus make it a strong candidate for adopting its sensing applications in biomarker detection technologies.

Two-Dimensional Nanostructures for Electrochemical Biosensor

Current advancements in the development of functional nanomaterials and precisely designed nanostructures have created new opportunities for the fabrication of practical biosensors for field analysis. Two-dimensional (2D) and three-dimensional (3D) nanomaterials provide unique hierarchical structures, high surface area, and layered configurations with multiple length scales and porosity, and the possibility to create functionalities for targeted recognition at their surface. Such hierarchical structures offer prospects to tune the characteristics of materials-e.g., the electronic properties, performance, and mechanical flexibility-and they provide additional functions such as structural color, organized morphological features, and the ability to recognize and respond to external stimuli. Combining these unique features of the different types of nanostructures and using them as support for bimolecular assemblies can provide biosensing platforms with targeted recognition and transduction properties, and increased robustness, sensitivity, and selectivity for detection of a variety of analytes that can positively impact many fields. Herein, we first provide an overview of the recently developed 2D nanostructures focusing on the characteristics that are most relevant for the design of practical biosensors. Then, we discuss the integration of these materials with bio-elements such as bacteriophages, antibodies, nucleic acids, enzymes, and proteins, and we provide examples of applications in the environmental, food, and clinical fields. We conclude with a discussion of the manufacturing challenges of these devices and opportunities for the future development and exploration of these nanomaterials to design field-deployable biosensors.

Label-Free Amperometric Immunosensor Based on Versatile Carbon Nanofibers Network Coupled with Au Nanoparticles for Aflatoxin B1 Detection

Facile detection methods for mycotoxins with high sensitivity are of great significance to prevent potential harm to humans. Herein, a label-free amperometric immunosensor based on a 3-D interconnected carbon nanofibers (CNFs) network coupled with well-dispersed Au nanoparticles (AuNPs) is proposed for the quantitative determination of aflatoxin B₁ (AFB₁) in wheat samples. In comparison to common carbon nanotubes (CNTs), the CNFs network derived from bacterial cellulose biomass possesses a unique hierarchically porous structure for fast electrolyte diffusion and a larger electrochemical active area, which increases the peak current of differential pulse voltammetry curves for an immunosensor. Combined with AuNPs that are incorporated into CNFs by using linear polyethyleneimine (PEI) as a soft template, the developed Au@PEI@CNFs-based immunosensor showed a good linear response to AFB₁ concentrations in a wide range from 0.05 to 25 ng mL^-1. The limit of detection was 0.027 ng mL^-1 (S/N = 3), more than three-fold lower than that of an Au@PEI@CNTs-based sensor. The reproducibility, storage stability and selectivity of the immunosensor were proved to be satisfactory. The developed immunosensor with appropriate sensitivity and reliable accuracy can be used for the analysis of wheat samples.

A review on graphene-based electrochemical sensor for mycotoxins detection

This work focuses on the study of nanomaterial-based sensors for mycotoxins detection. Due to their adverse effects on humans and animals, mycotoxins are heavily regulated, and the foodstuff and feed stocks with a high probability of being contaminated are often analyzed. In this context, the recent developments in graphene-based electrochemical sensors for mycotoxins detection were examined. The mycotoxins' toxicity implications on their detection and the development of diverse recognition elements are described considering the current challenges and limitations.

An Impedance Based Electrochemical Immunosensor for Aflatoxin B1 Monitoring in Pistachio Matrices

Aflatoxins are highly toxic fungal secondary metabolites that often contaminate food and feed commodities. An electrochemical immunosensor for the determination of aflatoxin B1 (AFB1) was fabricated by immobilizing monoclonal AFB1 antibodies onto a screen-printed gold electrode that was modified with carbo-methyldextran by N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride/N-hydroxysuccinimide cross-linking. An electrochemical interfacial modelling of biomolecular recognition was suggested and reasonably interpreted. Impedance technology was employed for the quantitative determination of AFB1. The limit of detection concentration of AFB1 for standard solutions and spiked pistachio samples was 0.5 ng/mL and 1 ng/mL, respectively. The immunosensor was able to successfully determine AFB1 concentrations in the range of 4.56–50.86 ng/mL in unknown pistachio samples. Comparative chromatographic analysis revealed that AFB1 concentrations that were higher than 345 ng/mL were not within the immunosensor’s upper limits of detection. Selectivity studies against Ochratoxin A and Aflatoxin M1 demonstrated that the proposed AFB1 immunosensor was able to differentiate between these other fungal mycotoxins. The novel electrochemical immunosensor approach has the potential for rapid sample screening in a portable, disposable format, thus contributing to the requirement for effective prevention and the control of aflatoxin B1 in pistachios.

Recent Advances in Aflatoxins Detection Based on Nanomaterials

Aflatoxins are the secondary metabolites of Aspergillus flavus and Aspergillus parasiticus and are highly toxic and carcinogenic, teratogenic and mutagenic. Ingestion of crops and food contaminated by aflatoxins causes extremely serious harm to human and animal health. Therefore, there is an urgent need for a selective, sensitive and simple method for the determination of aflatoxins. Due to their high performance and multipurpose characteristics, nanomaterials have been developed and applied to the monitoring of various targets, overcoming the limitations of traditional methods, which include process complexity, time-consuming and laborious methodologies and the need for expensive instruments. At the same time, nanomaterials provide general promise for the detection of aflatoxins with high sensitivity, selectivity and simplicity. This review provides an overview of recent developments in nanomaterials employed for the detection of aflatoxins. The basic aspects of aflatoxin toxicity and the significance of aflatoxin detection are also reviewed. In addition, the development of different biosensors and nanomaterials for aflatoxin detection is introduced. The current capabilities and limitations and future challenges in aflatoxin detection and analysis are also addressed.

Electrochemical impedimetric biosensors for food safety

Electrochemical impedimetric biosensors (EIBs) have a simple structure and can be used to rapidly and sensitively detect and measure hazards in food. EIBs detect and measure target molecules by transducing biochemical reactions on their surface to electrical signal outputs responding to a sinusoidal electrical signal input. Due to their structural simplicity and analytical sensitivity, EIBs are regarded as the most potent method of food hazard monitoring that can be implemented in the food supply chain. This paper discusses the theoretical background, structure, and construction of EIB and its applications in food safety.

Two-Dimensional Layered Nanomaterial-Based Electrochemical Biosensors for Detecting Microbial Toxins

Toxin detection is an important issue in numerous fields, such as agriculture/food safety, environmental monitoring, and homeland security. During the past two decades, nanotechnology has been extensively used to develop various biosensors for achieving fast, sensitive, selective and on-site analysis of toxins. In particular, the two dimensional layered (2D) nanomaterials (such as graphene and transition metal dichalcogenides (TMDs)) and their nanocomposites have been employed as label and/or biosensing transducers to construct electrochemical biosensors for cost-effective detection of toxins with high sensitivity and specificity. This is because the 2D nanomaterials have good electrical conductivity and a large surface area with plenty of active groups for conjugating 2D nanomaterials with the antibodies and/or aptamers of the targeted toxins. Herein, we summarize recent developments in the application of 2D nanomaterial-based electrochemical biosensors for detecting toxins with a particular focus on microbial toxins including bacterial toxins, fungal toxins and algal toxins. The integration of 2D nanomaterials with some existing antibody/aptamer technologies into electrochemical biosensors has led to an unprecedented impact on improving the assaying performance of microbial toxins, and has shown great promise in public health and environmental protection.

Alkaline Hydrolysis Behavior of Metal-Organic Frameworks NH2-MIL-53(Al) Employed for Sensitive Immunoassay via Releasing Fluorescent Molecules

Nanosized metal-organic frameworks (MOFs) NH₂-MIL-53(Al) were synthesized from 2-aminoterephthalic acid (NH₂·H₂BDC) and AlCl₃ by a facile hydrothermal method. The synthesized MOFs displayed good stability and a uniform particle size in a netural medium and were hydrolyzed in alkaline medium to release a large amount of fluorescent ligand NH₂·H₂BDC. Therefore, they can act as large-capability nanovehicles to load signal molecules for investigating various biorecognition events. In this work, based on the alkaline hydrolysis behavior of MOFs NH₂-MIL-53(Al), a sensitive immunoassay method was developed for the detection of aflatoxin B₁ (AFB₁) by employing them as fluorescent signal probes. With a competitive immunoassay mode on microplate, AFB₁ can be detected within a linear range of 0.05-25 ng mL^-1. The method was successfully employed to detect AFB₁ spiked in Job tears, Polygala tenuifolia and with acceptable recovery values of 83.00-114.00%. The detection results for moldy Fructus xanthii displayed an acceptable agreement with those from the high-performance liquid chromatography method, with relative errors of -14.21 to 3.49%. With the merits of high sensitivity, facile manipulation, and ideal reliability, the approach can also be extended to other areas such as aptasensor and receptor-binding assay.

Electrochemical Immuno- and Aptasensors for Mycotoxin Determination

Modern analysis of food and feed is mostly focused on development of fast and reliable portable devices intended for field applications. In this review, electrochemical biosensors based on immunological reactions and aptamers are considered in the determination of mycotoxins as one of most common contaminants able to negatively affect human health. The characteristics of biosensors are considered from the point of view of general principles of bioreceptor implementation and signal transduction providing sub-nanomolar detection limits of mycotoxins. Moreover, the modern trends of bioreceptor selection and modification are discussed as well as future trends of biosensor development for mycotoxin determination are considered.

Fabrication of gold/graphene nanostructures modified ITO electrode as highly sensitive electrochemical detection of Aflatoxin B1

Aflatoxins (AFs) are a family of fungal toxins that produced in food and feed by two Aspergillus species (Aspergillus flavus and Aspergillus parasiticus). Several techniques have been reported for AFs detection including high-pressure liquid chromatography, enzyme-linked immunosorbent assay, surface plasmon resonance and recombinant immune blotting assay. But, these methods are disadvantaged because they consumed a long time for analysis; in addition, they required a piece of complicated and expensive equipment. Therefore, developing of inexpensive sensors with high selectivity and sensitivity for detecting of AFs levels without extensive sample preparation has received great attention. Several electrochemical AFs sensors have been reported; however, there is still a need for developing a new, simple and rapid electrochemical AFs sensor. Here, we have developed a new AFs sensor based on Au nanostructures/graphene nanosheets modified ITO substrate that could enhance the Raman effect and the electrochemical conductivity. The modified electrode was prepared based on layer-by-layer electrochemical deposition method. AFs antibody was immobilized onto the Au nanostructures/graphene nanosheets; then it was used as a probe for rapid, simple and cheap detection of AFs level using Raman spectroscopy and electrochemical techniques. Our results demonstrated that the developed system showed a simple, easy and sensitive sensor for monitoring low concentrations of AFB1 with a detection limit of about 6.9 pg/mL, also it allowed the determination of AFB1 in spiked food samples.

A review on graphene-based nanocomposites for electrochemical and fluorescent biosensors

Biosensors with high sensitivity, selectivity and a low limit of detection, reaching nano/picomolar concentrations of biomolecules, are important to the medical sciences and healthcare industry for evaluating physiological and metabolic parameters.

Elastomeric conductive hybrid hydrogels with continuous conductive networks

The DA–PPy–GP ECHs with continuous conductive networks show high force and strain sensitivity.

Sandwich pair nanobodies, a potential tool for electrochemical immunosensing serum prostate-specific antigen with preferable specificity

Prostate-Specific Antigen (PSA) is a crucial biomarker for screening prostate cancer, but a sensitive and selective immunosensor for rapid quantification of serum PSA remains to be developed. In this study, a sandwich pair of nanobodies (Nbs) (i.e., Nb2 and Nb40) against PSA surface antigen was obtained from an alpaca-derived immune phage display library. A sandwich-type immunosensor for the sensitive and selective detection of PSA in serum samples was ingeniously designed based on the pair of Nbs. The small size of Nb40 allowed high capture densities on the surface of reduced graphene oxide (rGO) nanocomposed with massive Au nanoparticles (rGO@AuNPs), which significantly improved the conductivity and provided a large area to anchor many primary antibodies. The secondary antibody Nb2 fused with streptavidin -binding peptide (SBP) cooperated with Nb40 for PSA sandwiching. Accompanying introduction of horseradish peroxidase-streptavidin (HRP-SA) coupled with Nb2-SBP, the faradaic current was linearly correlated with the logarithm of PSA concentration in a range of 0.1-100 ng mL^-1. More importantly, this immunosensor exhibited excellent selectivity, stability, and reproducibility due to the sandwich pair Nbs. The proposed immunosensor was successfully applied in determining PSA in serum samples and could be used for the sensitive and specific detection of PSA.

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.

Affinity Biosensors for Detection of Mycotoxins in Food

This chapter reviews recent achievements in methods of detection of mycotoxins in food. Special focus is on the biosensor technology that utilizes antibodies and nucleic acid aptamers as receptors. Development of biosensors is based on the immobilization of antibodies or aptamers onto various conventional supports like gold layer, but also on nanomaterials such as graphene oxide, carbon nanotubes, and quantum dots that provide an effective platform for achieving high sensitivity of detection using various physical methods, including electrochemical, mass sensitive, and optical. The biosensors developed so far demonstrate high sensitivity typically in subnanomolar limit of detection. Several biosensors have been validated in real samples. The sensitivity of biosensors is similar and, in some cases, even better than traditional analytical methods such as ELISA or chromatography. We believe that future trends will be focused on improving biosensor properties toward practical application in food industry.

Label-Free Impedance Sensing of Aflatoxin B₁ with Polyaniline Nanofibers/Au Nanoparticle Electrode Array

Aflatoxin B1 (AFB₁) is produced by the Aspergillus flavus and Aspergillus parasiticus group of fungi which is most hepatotoxic and hepatocarcinogenic and occurs as a contaminant in a variety of foods. AFB₁ is mutagenic, teratogenic, and causes immunosuppression in animals and is mostly found in peanuts, corn, and food grains. Therefore, novel methodologies of sensitive and expedient strategy are often required to detect mycotoxins at the lowest level. Herein, we report an electrochemical impedance sensor that selectively detects AFB₁ at the lowest level by utilizing polyaniline nanofibers (PANI) coated with gold (Au) nanoparticles composite based indium tin oxide (ITO) disk electrodes. The Au-PANI nanocomposites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) spectroscopy, and electrochemical impedance spectroscopy (EIS). The composite electrode exhibited a 14-fold decrement in |Z|1Hz in comparison with the bare electrode. The Au-PANI acted as an effective sensing platform having high surface area, electrochemical conductivity, and biocompatibility which enabled greater loading deposits of capture antibodies. As a result, the presence of AFB₁ was screened with high sensitivity and stability by monitoring the changes in impedance magnitude (|Z|) in the presence of a standard iron probe which was target specific and proportional to logarithmic AFB₁ concentrations (CAFB₁). The sensor exhibits a linear range 0.1 to 100 ng/mL with a detection limit (3) of 0.05 ng/mL and possesses good reproducibility and high selectivity against another fungal mycotoxin, Ochratoxin A (OTA). With regard to the practicability, the proposed sensor was successfully applied to spiked corn samples and proved excellent potential for AFB₁ detection and development of point-of-care (POC) disease sensing applications.

Progress in utilisation of graphene for electrochemical biosensors

This review discusses recent graphene (GR) electrochemical biosensor for accurate detection of biomolecules, including glucose, hydrogen peroxide, dopamine, ascorbic acid, uric acid, nicotinamide adenine dinucleotide, DNA, metals and immunosensor through effective immobilization of enzymes, including glucose oxidase, horseradish peroxidase, and haemoglobin. GR-based biosensors exhibited remarkable performance with high sensitivities, wide linear detection ranges, low detection limits, and long-term stabilities. Future challenges for the field include miniaturising biosensors and simplifying mass production are discussed.

A non-toxic enzyme-linked immunosorbent assay for aflatoxin B1 using anti-idiotypic antibodies as substitutes

BACKGROUND

Immunoassays are widely employed techniques to detect aflatoxins since they are rapid, selective and sensitive. One common disadvantage of them is using aflatoxins as standard substances, which may trigger exposure risks to operators and environmental contamination without proper handling. Anti-idiotypic antibodies (anti-Ids or Ab2s), also named as internal-image anti-Ids, are able to mimic and function as antigens, so a non-toxic enzyme-linked immunosorbent assay (ELISA) for aflatoxin B₁ (AFB₁ ) is developed and validated using anti-Ids as substitutes.

RESULTS

Mouse monoclonal anti-idiotypic antibody (McAb2) to AFB₁ was generated by the hybridoma technique using Fab fragments of rabbit anti-AFB₁ idiotype antibody (Ab1) as immunogen. As indicated by indirect competitive ELISA, McAb2, represented an internal-image of antigen AFB₁ , was able to bind Fab with competition to AFB₁ . Then, analysis of AFB₁ in spiked samples by non-toxic ELISA using anti-Ids as substitutes was developed, and it showed no significant differences with comparison to AFB₁ as competitive antigens.

CONCLUSION

Our work demonstrated that anti-Ids could be used as internal-image mimicry of AFB₁ , and it had potential applications in immunoassays for antigen substitution to reduce operational risk for operators and environmental contamination. © 2016 Society of Chemical Industry.

Graphene and the immune system: Challenges and potentiality

In the growing area of nanomedicine, graphene-based materials (GBMs) are some of the most recent explored nanomaterials. For the majority of GBM applications in nanomedicine, the immune system plays a fundamental role. It is necessary to well understand the complexity of the interactions between GBMs, the immune cells, and the immune components and how they could be of advantage for novel effective diagnostic and therapeutic approaches. In this review, we aimed at painting the current picture of GBMs in the background of the immune system. The picture we have drawn looks like a cubist image, a sort of Picasso-like portrait looking at the topic from all perspectives: the challenges (due to the potential toxicity) and the potentiality like the conjugation of GBMs to biomolecules to develop advanced nanomedicine tools. In this context, we have described and discussed i) the impact of graphene on immune cells, ii) graphene as immunobiosensor, and iii) antibodies conjugated to graphene for tumor targeting. Thanks to the huge advances on graphene research, it seems realistic to hypothesize in the near future that some graphene immunoconjugates, endowed of defined immune properties, can go through preclinical test and be successfully used in nanomedicine.

Electrochemical Impedance Analysis of Biofunctionalized Conducting Polymer-Modified Graphene-CNTs Nanocomposite for Protein Detection

We report an electrodeposited poly(pyrrole-co-pyrrolepropylic acid) copolymer modified electroactive graphene-carbon nanotubes composite deposited on a glassy carbon electrode to detect the protein antigen (cTnI). The copolymer provides pendant carboxyl groups for the site-specific covalent immobilization of protein antibody, anti-troponin I. The hybrid nanocomposite was used as a transducer for biointerfacial impedance sensing for cTnI detection. The results show that the hybrid exhibits a pseudo capacitive behaviour with a maximum phase angle of 49° near 1 Hz, which is due to the inhomogeneous and porous structure of the hybrid composition. The constant phase element of copolymer is 0.61 (n = 0.61), whereas, it is 0.88 (n = 0.88) for the hybrid composites, indicating a comparatively homogeneous microstructure after biomolecular functionalization. The transducer shows a linear change in charge transfer characteristic (R _et) on cTnI immunoreaction for spiked human serum in the concentration range of 1.0 pg mL^-1-10.0 ng mL^-1. The sensitivity of the transducer is 167.8 ± 14.2 Ω cm² per decade, and it also exhibits high specificity and good reproducibility.

Mycotoxin Determination in Foods Using Advanced Sensors Based on Antibodies or Aptamers

Mycotoxin contamination threatens health and life of humans and animals throughout the food supply chains. Many of the mycotoxins have been proven to be carcinogens, teratogens and mutagens. The reliable and sensitive sensing methods are requested to monitor mycotoxin contamination. Advanced sensors based on antibodies or aptamers boast the advantages of high sensitivity and rapidity, and have been used in the mycotoxin sensing. These sensors are miniaturized, thereby lowering costs, and are applicable to high-throughput modes. In this work, the latest developments in sensing strategies for mycotoxin determination were critically discussed. Optical and electrochemical sensing modes were compared. The sensing methods for single mycotoxin or multiple mycotoxins in food samples were reviewed, along with the challenges and the future of antibody or aptamer-based sensors. This work might promote academic studies and industrial applications for mycotoxin sensing.