Amperometric determination of bisphenol A in milk using PAMAM–Fe3O4 modified glassy carbon electrode

Design and synthesis of hierarchical MnO-Fe3O4@C/expanded graphite composite for sensitive electrochemical detection of bisphenol A

Hierarchically nanostructured binary transition metal oxide-based materials with high conductivity and catalytic activity are quite attractive for the electrochemical quantitative detection of environmental pollutants due to their natural abundance, variable oxidation state, and excellent synergies between metal sites. Herein, a new hierarchical MnO-Fe3O4@C/expanded graphite (EG) composite is designed and synthesized through a simple and in situ annealing method with the utilization of bimetallic organic framework (FeMn-MOF)/EG precursor. The synthesized MnO-Fe3O4@C/EG composite possesses a unique hierarchical nanoarchitecture that small-sized bimetallic oxide nanoparticles of 10-40 nm completely encapsulated by amorphous carbon layers of 2-4 nm are uniformly distributed on the EG platform. This distinctive structure combines the advantages of high conductivity, excellent catalytic activity, and strong stability. Resultantly, when it is applied to monitor environmental endocrine disruptors, the sensor exhibits a significant catalytic effect on the electrochemical oxidation of bisphenol A (BPA), inducing an amplified response current. In addition, the sensor shows a wide linear range of 1-50 μM and 50-400 μM for the BPA monitor, giving a sensitivity of 5208.8 and 1641.9 μA mM-1 cm-2, respectively. This study offers a new approach to design hierarchical binary metal oxide-based sensing materials as well as to explore their electrochemical properties and applications for the determination of emerging contaminants.

A dual-mode "signal-on" split-type aptasensor for bisphenol A via target-induced hybridization chain reaction amplification

Herein, a dual-mode detection system was constructed for efficient and accurate detection of bisphenol A (BPA) with the assistance of the BPA-induced hybridization chain reaction (HCR). The captured DNA (cDNA) was first modified on the surface of magnetic spheres modified with gold nanoparticles and polydopamine and then hybridized with the BPA aptamer to form double-stranded DNA (dsDNA). In the presence of the BPA target, the BPA aptamer was released from the surface of the magnetic sphere. The free cDNA triggered a HCR to construct a DNA duplex. Methylene blue (MB), as a bifunctional probe, was intercalated into the double-stranded DNA to amplify the photocurrent (IPEC) of the CdS-modified electrode and generate an electrochemical current (IEC) at the same time. Under the optimized conditions, the PEC and EC signal responses of the system were linear to the logarithm of BPA concentration in the range of 1.0 × 10-10 M to 1.0 × 10-5 M. The detection limits were found to be 1.27 × 10-11 M and 3.0 × 10-11 M using the PEC and EC methods, respectively. The constructed dual-mode biosensor exhibited good performance for real sample analysis, demonstrating its promising potential for practical applications. In addition, this dual-mode detection strategy provides more accurate and reliable detection results.

An indirect method for the analysis of bisphenol A, as a Mn(III)-chelate complex, in milk samples by ultrasound assisted-cloud point extraction/flame atomic absorption spectrometry

A method for indirect determination of bisphenol A (BPA), as a Mn(III)-chelate complex, in milk samples by flame atomic absorption spectrometry (FAAS) was developed. The method was based on cloud point extraction with ultrasound assistance (UA-CPE). In the pre-concentration step by UA-CPE, the ternary complex selectively formed between BPA and Mn(III)-oxalate at pH 5.0 was extracted into the mixed micellar phase of ionic and nonionic surfactants, cetyltrimethylammonium bromide (CTABr) and polyethylene glycol tert-octylphenyl ether (Triton X-114) as a sensitivity enhancer and extractant. After phase separation by centrifugation, the separated extract was diluted with acidic methanol and analyzed by FAAS. The reproducibility of the signal in the detection step especially at low concentrations was greatly improved by the use of polyvinyl alcohol (PVA) as a stabilizer. Using indirect Mn-responses by FAAS, the main variables affecting the extraction efficiency were evaluated and optimized. Under optimized conditions, the calibration graph was highly linear in the range of 0.8-130 μg L^-1 with limits of detection and quantification of 0.23 and 0.76 μg L^-1, intra- and inter-day precisions in the range of 2.8-5.2% and 3.8-7.2%, and recovery in the range of 94.2-98.5% (10, 25, 100 μg L^-1, n: 5 and 3 × 5). From pre-concentration of a 35 mL sample by UA-CPE, the pre-concentration factor was found to be 70 with a 41-fold sensitivity improvement. The matrix effect was greatly reduced by deproteinization with trichloroacetic acid (TCA) and 20-fold dilution of milk samples before analysis. The method accuracy was checked by analysis of trace BPA in milk samples via a calibration curve in solvent and a matrix-matched calibration curve prepared from sample extracts. The results were in the range of 2.1-7.3 μg L^-1 and 2.0-7.0 μg L^-1 without any matrix effect. According to the Student's t-test, there is not a statistically significant difference between the results found by using the two calibration curves. Finally, it can be concluded that the method is suitable for detecting BPA in milk based products at concentrations far below the specific migration limit (SML) of 600 μg L^-1.

Simultaneous detection of carmoisine and tartrazine in food samples using GO-Fe3O4-PAMAM and ionic liquid based electrochemical sensor

This study was performed to investigate the simultaneous detection of carmoisine and tartrazine, two food azo dyes, with a new voltammetric sensor based on graphene oxide-Fe3O4 (GO-Fe3O4) nanocomposite functionalized with fourth-generation poly(amidoamine) (G4 PAMAM) dendrimers (GO-Fe3O4-G4 PAMAM) and ionic liquid (IL) modified carbon paste electrode (GO-Fe3O4-G4 PAMAM/ILCPE). The GO-Fe3O4-G4 PAMAM was synthesized and characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), vibrating-sample magnetometer (VSM), and fourier transform infrared (FT-IR) techniques. Cyclic voltammetry (CV) was used to evaluate the electrochemical behavior of carmoisine, revealing the good electrocatalytic function of GO-Fe3O4-G4 PAMAM/ILCPE. Linear response from 0.1 to 170.0 μM was obtained based on carmoisine electrochemical oxidation through differential pulse voltammetry (DPV). The limit of detection (LOD) value obtained was 0.02 μM. Also, the GO-Fe3O4-G4 PAMAM/ILCPE was used for the simultaneous determination of carmoisine and tartrazine. In co-existence system containing carmoisine and tartrazine, the developed sensor exhibited well-defined and separate DPV peaks (i.e., 770 mV) for carmoisine and tartrazine. Besides, repeatability, reproducibility and stability studies were performed. Additionally, the analytical application of this sensor was demonstrated by determination of carmoisine and tartrazine in food samples including lemon juice and powdered juice.

Electrochemical Methods for the Analysis of Milk

The milk and dairy industries are some of the most profitable sectors in many countries. This business requires close control of product quality and continuous testing to ensure the safety of the consumers. The potential risk of contaminants or degradation products and undesirable chemicals necessitates the use of fast, reliable detection tools to make immediate production decisions. This review covers studies on the application of electrochemical methods to milk (i.e., voltammetric and amperometric) to quantify different analytes, as reported over the last 10 to 15 years. The review covers a wide range of analytes, including allergens, antioxidants, organic compounds, nitrogen- and aldehyde containing compounds, biochemicals, heavy metals, hydrogen peroxide, nitrite, and endocrine disruptors. The review also examines pretreatment procedures applied to milk samples and the use of novel sensor materials. Final perspectives are provided on the future of cost-effective and easy-to-use electrochemical sensors and their advantages over conventional methods.

Ultrasensitive and Highly Selective Detection of Bisphenol a Using Core-Shell Magnetic Molecularly Imprinted Quantum Dots Electrochemiluminescent Probe

The main aim of this work was to develop a magnetic molecularly imprinted polymer (MMIP)-based quantum dots electrochemiluminescent (ECL) probe for the ultrasensitive and highly selective detection of bisphenol A (BPA). The prepared core-shell Fe₃O₄@SiO₂ exhibited superparamagnetic properties, making them easy to separate. The MIP was fabricated by the self-polymerization of dopamine on the surface of amine-terminated Fe₃O₄@SiO₂ (Fe₃O₄@SiO₂-NH₂) magnetic nanoparticles and doped with quantum dots (QDs) to form an ECL system. The ECL intensity decrease with the concentration of BPA increased, due to the BPA molecules occupied molecularly imprinted sites and blocked the strong ECL emission of QDs. The prepared ECL sensor performed satisfactorily in the detection of BPA, with a wide linear range from 10^- 4 to 10^- 9 mol L^- 1 and a low detection limit of 3.4 × 10^- 10 mol L^- 1 (S/N = 3). The recoveries of BPA achieved were in the range 96%-107% in the detection of actual water samples. The proposed ECL sensor displayed high sensitivity and stability, and may provide an approach for determining other important analytes.

Preparation of 2D Graphene/MXene nanocomposite for the electrochemical determination of hazardous bisphenol A in plastic products

Bisphenol A (BPA) is one of the major contaminants with significant health hazards, which could also affect the endocrine system or induce cancer. It is essential to develop a highly sensitive and selective BPA sensor for environmental and food safety. Herein, 2D hybrid graphene/Ti₃C₂T_x nanocomposite (Gr/MXene) was prepared via a top-down method and then used to fabricate an electrochemical BPA sensor. The X-ray diffraction spectrometer (XRD) and Raman spectroscopy analysis were carried out to verify the successful formation of Gr sheets with MXene. The high resolution scanning electron microscopy (HR-SEM) was revealed the formation of MXene, and Gr/MXene nanocomposite. Furthermore, the 2D hybrid Gr/MXene nanocomposite modified glassy carbon electrode (GCE) was prepared for BPA oxidation in 100 mM phosphate buffer solution (PBS). Under the optimized condition, the Gr/MXene/GCE was displayed a linear range of detection from 10 to 180 nM and 1 to 10 μM BPA with the detection limits of 4.08 nM and 0.35 μM by amperometry and differential pulse voltammetry (DPV), respectively. Moreover, the proposed Gr/MXene modified electrode exhibited excellent stability, selectivity, repeatability and reproducibility towards the BPA detection. As a proof of concept, Gr/MXene modified sensor was effectively used to detect BPA in modern plastic products with the recovery ranging from 99.2 to 104.5%.

Triple-signaling amplification strategy based electrochemical sensor design: boosting synergistic catalysis in metal-metalloporphyrin-covalent organic frameworks for sensitive bisphenol A detection

A covalent organic framework (COF) is a promising type of porous material with customizable surface characteristics. Confining multiple catalytic units within a mesoporous COF can generate abundant active sites and improve the catalytic performance. In this work, a COF with both metalloporphyrin and a metal nanoparticle complex denoted as hemin/TAPB-DMTP-COF/AuNPs (TAPB: 1,3,5-tris(4-amino-phenyl)benzene, DMTP: 2,5-dimethoxyterephaldehyde, AuNPs: Au nanoparticles) has been successfully fabricated through a hierarchical encapsulation method. The as-synthesized composite was then employed to construct an electrochemical sensing platform for the efficient detection of bisphenol A (BPA). Under the optimal conditions, the hemin/TAPB-DMTP-COF/AuNP sensor presented a linear range of 0.01-3 μmol L^-1 and a low detection limit of 3.5 nmol L^-1. The satisfactory signal amplification is based on a triple-signaling amplification strategy due to the abundant Fe³⁺ sites of Fe-porphyrin, high conductivity of AuNPs and a large specific surface area of the TAPB-DMTP-COF. The proposed method was used to measure the content of BPA in different water samples with a satisfactory recovery from 95.5 to 104.0%, suggesting the great potential of the sensor in practical applications.

A Silver-Loaded Exfoliated Graphite Nanocomposite Anti-Fouling Electrochemical Sensor for Bisphenol A in Thermal Paper Samples

Silver nanoparticles (AgNPs) were synthesized separately and loaded onto the expanded layers of exfoliated graphite (EG) to form a silver nanoparticle-exfoliated graphite nanocomposite (AgNPs-EG). The AgNPs-EG was compressed into a pellet (0.6 cm in diameter) and used to prepare an electrochemical sensor for bisphenol A (BPA) in standard samples and in thermal paper. The synthesized materials were characterized by ultraviolet-visible spectrophotometry, X-ray diffraction spectroscopy, scanning electron microscopy, and energy-dispersive X-ray. The electrochemical behavior of BPA on the AgNPs-EG sensor was investigated by cyclic voltammetry and square wave voltammetry. Under optimized experimental conditions, the oxidation peak current was linearly proportional to bisphenol A concentrations in the range from 5.0 to100 μM, with a coefficient of determination (R2 ) of 0.9981. The obtained limit of detection of the method was 0.23 μM. The fabricated sensor was able to overcome electrode fouling with good reproducibility (RSD = 2.62%, n = 5) by mechanical polishing of the electrode on emery paper. The proposed method was successfully applied to determine bisphenol A in thermal paper samples and demonstrated good accuracy of 93.1 to 113% recovery.

Sensitive and selective electrochemical detection of bisphenol A based on SBA-15 like Cu-PMO modified glassy carbon electrode

This work reports the electrochemical detection of bisphenol A (BPA) using a novel and sensitive electrochemical sensor based on the Cu functionalized SBA-15 like periodic mesoporous organosilica-ionic liquid composite modified glassy carbon electrode (Cu@TU-PMO/IL/GCE). The structural morphology of Cu@TU-PMO is characterized by X-ray powder diffraction (XRD), energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), Field emission scanning electron microscopy (FE-SEM), and Brunauer-Emmett-Teller (BET). The catalytic activity of the modified electrode toward oxidation of BPA was interrogated with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in phosphate buffer solution (pH 7.0) using the fabricated sensor. The electrochemical detection of the analyte was carried out at a neutral pH and the scan rate studies revealed that the sensor was stable. Under the optimal conditions, a linear range from 5.0 nM to 2.0 µM and 4.0 to 500 µM for detecting BPA was observed with a detection limit of 1.5 nM (S/N = 3). The sensor was applied to detect BPA in tap and seawater samples, and the accuracy of the results was validated by high-performance liquid chromatography (HPLC). The proposed method provides a powerful tool for the rapid and sensitive detection of BPA in environmental samples.

Magnetic nanomaterials based electrochemical (bio)sensors for food analysis

It is widely accepted that nanotechnology attracted more interest because of various values that nanomaterial applications offers in different fields. Recently, researchers have proposed nanomaterials based electrochemical sensors and biosensors as one of the potent alternatives or supplementary analytical tools to the conventional detection procedures that consumes a lot of time. Among different nanomaterials, researchers largely considered magnetic nanomaterials (MNMs) for developing and fabricating the electrochemical (bio)sensors for numerous utilizations. Among several factors, healthier and higher quality foods are the most important preferences of consumers and manufacturers. For this reason, developing new techniques for rapid, precise as well as sensitive determination of components or contaminants of foods is very important. Therefore, developing the new electrochemical (bio)sensors in food analysis is one of the key and effervescent research fields. In this review, firstly, we presented the properties and synthesis strategies of MNMs. Then, we summarized some of the recently developed MNMs-based electrochemical (bio)sensors for food analysis including detecting the antioxidants, synthetic food colorants, pesticides, heavy metal ions, antibiotics and other analytes (bisphenol A, nitrite and aflatoxins) from 2010 to 2020. Finally, the present review described advantages, challenges as well as future directions in this field.

Recent Developments in Polymer Nanocomposite-Based Electrochemical Sensors for Detecting Environmental Pollutants

The human population is generally subjected to diverse pollutants and contaminants in the environment like those in the air, soil, foodstuffs, and drinking water. Therefore, the development of novel purification techniques and efficient detection devices for pollutants is an important challenge. To date, experts in the field have designed distinctive analytical procedures for the detection of pollutants including gas chromatography/mass spectrometry and atomic absorption spectroscopy. While the mentioned procedures enjoy high sensitivity, they suffer from being laborious, expensive, require advanced skills for operation, and are inconvenient to deploy as a result of their massive size. Therefore, in response to the above-mentioned limitations, electrochemical sensors are being developed that enjoy robustness, selectivity, sensitivity, and real-time measurements. Considerable advancements in nanomaterials-based electrochemical sensor platforms have helped to generate new technologies to ensure environmental and human safety. Recently, investigators have expanded considerable effort to utilize polymer nanocomposites for building the electrochemical sensors in view of their promising features such as very good electrocatalytic activities, higher electrical conductivity, and effective surface area in comparison to the traditional polymers. Herein, the first section of this review briefly discusses the most important methods for polymer nanocomposites synthesis, such as in situ polymerization, direct mixing of polymer and nanofillers (melt-mixing and solution-mixing), sol-gel, and electrochemical methods. It then summarizes the current utilization of polymer nanocomposites for the preparation of electrochemical sensors as a novel approach for monitoring and detecting environmental pollutants which include heavy metal ions, pesticides, phenolic compounds, nitroaromatic compounds, nitrite, and hydrazine in different mediums. Finally, the current challenges and future directions for the polymer nanocomposites-based electrochemical sensing of environmental pollutants are outlined.

Colorimetric detection and bio-magnification of bisphenol A in fish organs and water sources using 3',6'-bis(diethylamino)-2- ((3,4,5trimethyl benzylidene) amino) spiro [isoindoline -1,9'-xanthen ]-3-one (BTSIXO)-Fe3+ ion conjugate

Current study is focusing mainly on the development of simple, novel, and cost-effective optical sensor to detect and quantify Bisphenol A (BPA) contamination. We designed a very selective and sensitive colorimetric sensor using synthesized 3', 6'- bis(diethylamino) -2- ((3,4,5 trimethyl benzylidene) amino)spiro [isoindoline-1,9'-xanthen] -3-one (BTSIXO) conjugated with Fe³⁺-ions via very simple eco- friendly synthetic protocol. The sensor has an excellent wide detection range for BPA from 0.1 to 150 ppm with LODs of 0.02 ppm. Finally, the applicability of the sensor was demonstrated in fish samples especially in the organs of Oreochromis mossambicus fingerlings and contaminated industrial water samples. The sensor was also applied for the quantification of BPA present drinking water stored in the plastic bottles. The developed sensor has shown a good agreement and accuracy when compared with ESI-Mass techniques.

Synthesis of a hierarchically structured Fe3O4–PEI nanocomposite for the highly sensitive electrochemical determination of bisphenol A in real samples

In this work, a novel, highly sensitive and cost-effective sensing electrode was fabricated for the sensitive detection of bisphenol A in milk and water samples.

Novel electrochemical sensors from poly[N-(ferrocenyl formacyl) pyrrole]@multi-walled carbon nanotubes nanocomposites for simultaneous determination of ascorbic acid, dopamine and uric acid

Novel multi-walled carbon nanotubes coated with poly[N-(ferrocenyl formacyl) pyrrole] (MWCNTs@PFFP) nanocomposites were prepared through the in situ oxidation polymerization reaction of N-(ferrocenyl formacyl) pyrrole in the presence of MWCNTs. The MWCNTs@PFFP nanocomposites were characterized by FT-IR, Raman, TGA, XRD, XPS, SEM and TEM techniques. The MWCNTs@PFFP nanocomposites were fabricated into novel electrochemical sensors for simultaneous determination of ascorbic acid (AA), dopamine (DA) and uric acid (UA). The electrochemical behavior of the MWCNTs@PFFP/GCE sensors was examined, and the parameters that influence electrochemical signals were optimized. The experimental results showed that the fabricated modified electrode sensors exhibited good sensitivity, selectivity, specificity, repeatability and a long lifetime, remaining the initial current of at least 92.5% after 15 days storage in air. The sensors possessed a linear response concentration range over 200-400 μM for AA, 2-16 μM for both DA and UA, and a limit of detection as low as 40.0, 1.1 and 7.3 × 10-1 μM for AA, DA and UA, respectively. They are expected to be used as a potential tool for the simultaneous detection of DA, AA and UA in the human body.

Metal-based Nanoparticles as Conductive Mediators in Electrochemical Sensors: A Mini Review

Background:

Modified electrodes are a new approach to improving the characteristics of the electrochemical sensors. The high conductivity and low charge transfer resistance are the major properties of new mediators for improving electrochemical sensors. Metal-based nanoparticles showed good electrical conductivity and can be selected as the suitbale mediator for modified electrodes.

Objective:

Recently, metal-based nanoparticles, such as Au nanoparticle, TiO2 nanoparticle, Fe3O4 nanoparticle and etc. were suggested as the suitable mediator for modification of solid electrodes. The high surface area and low charge transfer resistance of metal-based nanoparticles, suggested the exceptional intermediate in the electrochemical sensors. Here, we tried to consider these exceptional effects through reviewing some of the recently published works.

Rapid and Sensitive Determination of Vanillin Based on a Glassy Carbon Electrode Modified with Cu₂O-Electrochemically Reduced Graphene Oxide Nanocomposite Film

A facile cuprous oxide nanoparticles functionalized electro-reduced graphene oxide modified glassy carbon electrode (denoted as Cu₂O NPs-ERGO/GCE) was fabricated via a simple physical adsorption and electrochemical reduction approach. Cyclic voltammetry and second-order derivative linear scan voltammetry were used to investigate the electrocatalysis oxidation of vanillin on the Cu₂O NPs-ERGO/GCE. The compound yielded a well-defined voltammetric response in 0.1 M H₂SO₄ at 0.916 V (vs. saturated calomel electrode (SCE)). A linear calibration graph was obtained in the concentration range of 0.1 μM to 10 μM and 10 μM to 100 μM, while the detection limit (S/N = 3) is 10 nM. In addition, the Cu₂O NPs-ERGO/GCE presented well anti-interference ability, stability, and reproducibility. It was used to detect vanillin sensitively and rapidly in different commercial food products, and the results were in agreement with the values obtained by high performance liquid chromatography.

Advances in sensing and biosensing of bisphenols: A review

Bisphenols (BPs) are well known endocrine disrupting chemicals (EDCs) that cause adverse effects on the environment, biotic life and human health. BPs have been studied extensively because of an increasing concern for the safety of the environment and for human health. They are major raw materials for manufacturing polycarbonates, thermal papers and epoxy resins and are considered hazardous environmental contaminants. A vast array of sensors and biosensors have been developed for the sensitive screening of BPs based on carbon nanomaterials (carbon nanotubes, fullerenes, graphene and graphene oxide), quantum dots, metal and metal oxide nanocomposites, polymer nanocomposites, metal organic frameworks, ionic liquids and molecularly imprinted polymers. This review is devoted mainly to a variety of sensitive, selective and reliable sensing and biosensing methods for the detection of BPs using electrochemistry, fluorescence, colorimetry, surface plasmon resonance, luminescence, ELISAs, circular dichroism, resonance Rayleigh scattering and adsorption techniques in plastic products, food samples, food packaging, industrial wastes, pharmaceutical products, human body fluids and many other matrices. It summarizes the advances in sensing and biosensing methods for the detection of BPs since 2010. Furthermore, the article discusses challenges and future perspectives in the development of novel sensing methods for the detection of BP analogs.

A hydrogen peroxide sensor based on TNM functionalized reduced graphene oxide grafted with highly monodisperse Pd nanoparticles

Addressed herein, we report the synthesis and characterization of a tert-nonyl mercaptan (TNM) functionalized reduced graphene oxide (rGO) supported palladium (Pd) nanoparticles (NPs) (Pd/TNM@rGO) as electrochemical sensor. The highly monodisperse Pd/TNM@rGO nanocomposite was applied for electrochemical determination of hydrogen peroxide (H₂O₂) at a potential range of -0.6 to +0.8 V. The Pd/TNM@rGO sensor demonstrated very high activity, sensitivity, reusability and durability toward H₂O₂ sensing. The well dispersed Pd/TNM@rGO nanocomposite has been characterized by using several analytical techniques such as, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), electron energy loss spectroscopy (EELS) and electrochemical impedance spectroscopy (EIS). The catalytic performance of prepared biosensor was also characterized by using cyclic voltammetry (CV) and chronoamperometry (CA) methods. The proposed H₂O₂ biosensor showed a broad linear range up to 12 mM, and a very low detection limit of 0.0025 μM, with a quick response time of less than 10 s. Additionally, the biosensor exhibited great capability, reproducibility and durability for the examination of H₂O₂.

Dendrimer nanohybrid carrier systems: an expanding horizon for targeted drug and gene delivery

Highly controllable dendritic structural design means dendrimers are a leading carrier in drug delivery applications. Dendrimer- and other nanocarrier-based hybrid systems are an emerging platform in the field of drug delivery. This review is a compilation of increasing reports of dendrimer interactions, such as dendrimer-liposome, dendrimer-carbon-nanotube, among others, known as hybrid carriers. This should prompt entirely new research with promising results for these hybrid carriers. It is assumed that such emerging hybrid nanosystems - from combining two already-established drug delivery platforms - could lead the way for the development of newer delivery systems with multiple applicability for latent theranostic applications in the future.

Portable Bio/Chemosensoristic Devices: Innovative Systems for Environmental Health and Food Safety Diagnostics

This mini-review covers the newly developed biosensoristic and chemosensoristic devices described in recent literature for detection of contaminants in both environmental and food real matrices. Current needs in environmental and food surveillance of contaminants require new simplified, sensitive systems, which are portable and allow for rapid and on-site monitoring and diagnostics. Here, we focus on optical and electrochemical bio/chemosensoristic devices as promising tools with interesting analytical features that can be potentially exploited for innovative on-site and real-time applications for diagnostics and monitoring of environmental and food matrices (e.g., agricultural waters and milk). In near future, suitably developed and implemented bio/chemosensoristic devices will be a new and modern technological solution for the identification of new quality and safety marker indexes as well as for a more proper and complete characterization of abovementioned environmental and food matrices. Integrated bio/chemosensoristic devices can also allow an “holistic approach” that may prove to be more suitable for diagnostics of environmental and food real matrices, where the copresence of more bioactive substances is frequent. Therefore, this approach can be focused on the determination of net effect (mixture effect) of bioactive substances present in real matrices.

Diamond-based electrochemical aptasensor realizing a femtomolar detection limit of bisphenol A

In this study, we designed and fabricated an electrochemical impedance aptasensor based on Au nanoparticles (Au-NPs) coated boron-doped diamond (BDD) modified with aptamers, and 6-mercapto-1-hexanol (MCH) for the detection of bisphenol A (BPA). The constructed BPA aptasensor exhibits good linearity from 1.0×10^-14 to 1.0×10^-9molL^-1. The detection limitation of 7.2×10^-15molL^-1 was achieved, which can be attributed to the synergistic effect of combining BDD with Au-NPs, aptamers, and MCH. The examine results of BPA traces in Tris-HCl buffer and in milk, UV spectra of aptamer/BPA and interference test revealed that the novel aptasensors are of high sensitivity, specificity, stability and repeatability, which could be promising in practical applications.

A label-free photoelectrochemical aptasensor for bisphenol A based on surface plasmon resonance of gold nanoparticle-sensitized ZnO nanopencils

A simple and novel photoelectrochemical (PEC) aptasensor for selective detection of bisphenol A (BPA) was developed using surface plasmon resonance of Au nanoparticles activated ZnO nanopencils. With the irradiation of simulated light, the increased photocurrent of nano-Au/ZnO than that of pure ZnO nanopencil is induced by the hot electrons from excited Au nanoparticles. The perfect selectivity is attributed to the specific binding of BPA to its aptamer. With the addition of BPA, the conformation of aptamer changed to a G-quadruplex structure, which resulted in the blockages of photogenerated electron-transfer channels. Based on the above mechanisms and the optimized conditions, the assembled PEC aptasensor was linear with the concentration of BPA in the range of 1-1000nmolL(-1) with a detection limit of 0.5nmolL(-1). The presence of the same concentration and similar structure of other organics did not interfere in the detection of BPA and the recovery was between 96.2% and 108.4%. It has been successfully applied to the detection of BPA in drinking water and liquid milk samples. This PEC aptasensor has good performances in novelty, selectivity, sensitivity and low cost, and it provides an alternative approach to the detection of BPA.

Design of ultrasensitive bisphenol A-aptamer based on platinum nanoparticles loading to polyethyleneimine-functionalized carbon nanotubes

Here, a highly sensitive electrochemical aptasensor based on a novel signal amplification strategy for the determination of bisphenol A (BPA) was developed. Construction of the aptasensor began with the deposition of highly dispersed platinum nanoparticles (PtNPs)/acid-oxidized carbon nanotubes (CNTs-COOH) functionalized with polyethyleneimine (PEI) at the surface of glassy carbon (PtNPs/PEI/CNTs-COOH/GC) electrode. After immobilizing the amine-capped capture probe (ssDNA1) through the covalent amide bonds formed by the carboxyl groups on the nanotubes and the amino groups on the oligonucleotides, we employed a designed complementary BPA-aptamer (ssDNA2) as a detection probe to hybridize with the ssDNA1. By adding BPA as a target, the aptamer specifically bound to BPA and its end folded into a BPA-binding junction. Because of steric/conformational restrictions caused by aptamer-BPA complex formation at the surface of modified electrode, the interfacial electron transfer of [Fe(CN)6](3-/4-) as a probe was blocked. Sensitive quantitative detection of BPA was carried out by monitoring the decrease of differential pulse voltammetric responses of [Fe(CN)6](3-/4-) peak current with increasing BPA concentrations. The newly developed aptasensor embraced a number of attractive features such as ease of fabrication, low detection limit, excellent selectivity, good stability and a wide linear range with respect to BPA.

Sensitive Adsorptive Voltammetric Method for Determination of Bisphenol A by Gold Nanoparticle/Polyvinylpyrrolidone-Modified Pencil Graphite Electrode

A novel electrochemical sensor gold nanoparticle (AuNP)/polyvinylpyrrolidone (PVP) modified pencil graphite electrode (PGE) was developed for the ultrasensitive determination of Bisphenol A (BPA). The gold nanoparticles were electrodeposited by constant potential electrolysis and PVP was attached by passive adsorption onto the electrode surface. The electrode surfaces were characterized by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). The parameters that affected the experimental conditions were researched and optimized. The AuNP/PVP/PGE sensor provided high sensitivity and selectivity for BPA recognition by using square wave adsorptive stripping voltammetry (SWAdSV). Under optimized conditions, the detection limit was found to be 1.0 nM. This new sensor system offered the advantages of simple fabrication which aided the expeditious replication, low cost, fast response, high sensitivity and low background current for BPA. This new sensor system was successfully tested for the detection of the amount of BPA in bottled drinking water with high reliability.

ZrO2 supported Nano-ZSM-5 nanocomposite material for the nanomolar electrochemical detection of metol and bisphenol A

ZrO₂ decorated Nano-ZSM-5 was synthesized by the calcination of the physical mixture of ZrO₂ and Nano-ZSM-5. Electrochemical sensor based on this material was investigated in the determination of hazardous organic water pollutants.

Electrochemical determination of bisphenol A at ordered mesoporous carbon modified nano-carbon ionic liquid paste electrode

A simple bisphenol A (BPA) sensor was successfully fabricated based on ordered mesoporous carbon CMK-3 modified nano-carbon ionic liquid paste electrode (CMK-3/nano-CILPE). The nanostructure of CMK-3 and the surface morphologies of modified electrodes were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Electrochemical properties of the fabricated electrodes were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The fabricated sensor displayed excellent electroactivity towards bisphenol A using linear sweep voltammetry (LSV). Experimental conditions influencing the analytical performance of the modified electrode were optimized. Under optimal conditions, the oxidation peak current was proportional to BPA concentration in the range from 0.2 μM to 150 μM with a detection limit of 0.05 μM (S/N=3). This method was successfully used for determination of BPA leached from drinking bottle and plastic bag with good recoveries.