An amperometric sensor for the determination of benzophenone in food packaging materials based on the electropolymerized molecularly imprinted poly-o-phenylenediamine film

Enzyme-free impedimetric biosensor-based molecularly imprinted polymer for selective determination of L-hydroxyproline

This study first reported enzyme-free impedimetric biosensor-based molecularly imprinted polymers for selective and sensitive determination of L-hydroxyproline (L-hyp), a biomarker for the early diagnosis of bone diseases. In recent study, utilizing a single 3-aminophenylboronic acid (3-APBA) to create imprinted surfaces could result in a strong interaction and difficulty in removal of a template molecule. Hence, a mixture of monomer solution containing 3-APBA and o-phenylenediamine (OPD) in the presence of the L-hyp molecule was co-electropolymerized onto the screen-printed electrode using cyclic voltammetry (CV) to eradicate this mentioned limitation. The detection principle of this sensor is relied on alteration of mediator's charge transfer resistance (R_ct) that could be obstructed by L-hyp occupied in imprinted surface. The successfully fabricated biosensor was explored by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and confocal scanning microscopy. Furthermore, the effect of polymer composition on the R_ct response was systematically investigated. The result exhibited that the mixture of monomers could provide the highest change of R_ct due to high selectivity from esterification of 3-APBA and from hydrogen bond of OPD surrounding the template. The sensor showed a significant increase in R_ct in the presence of L-hyp, whereas no observable resistance change was detected in the absence thereof. The calibration curve was obtained in the range from 0.4 to 25 μg mL^-1 with limits of detection (3SD_blank/Slope) and quantification (10SD_blank/Slope) of 0.13 and 0.42 μg mL^-1, respectively. This biosensor exhibited high selectivity and sensitivity and was successfully applied to determine L-hyp in human serum samples with satisfactory results.

A review on contaminants of emerging concern in European raptors (2002-2020)

Raptors (birds of prey and owls) have been widely used as suitable bioindicators of environmental pollution. They occupy the highest trophic positions in their food chains and are documented to bioaccumulate high concentrations of persistent pollutants such as toxic metals and legacy persistent organic pollutants (POPs).Whereas raptors played a critical role in developing awareness of and policy for chemical pollution, they have thus far played a much smaller role in current research on contaminants of emerging concern (CECs). Given the critical knowledge obtained from monitoring 'legacy contaminants' in raptors, more information on the levels and effects of CECs on raptors is urgently needed. This study critically reviews studies on raptors from Europe reporting the occurrence of CECs with focus on the investigated species, the sampled matrices, and the bioanalytical methods applied. Based on this, we aimed to identify future needs for monitoring CECs in Europe. Perfluoroalkyl substances (PFASs), novel flame retardants (NFRs), and to a lesser extent UV-filters, neonicotinoids, chlorinated paraffins, parabens and bisphenols have been reported in European raptors. White-tailed Eagle (Haliaeetus albicilla), Peregrine falcon (Falco peregrinus) and Northern goshawk (Accipiter gentilis) were the most frequently studied raptor species. Among matrices, eggs, feathers and plasma were the most widely employed, although the potential role of the preen gland as an excretory organ for CECs has recently been proposed. This review highlights the following research priorities for pollution research on raptors in Europe: 1) studies covering all the main classes of CECs; 2) research in other European regions (mainly East Europe); 3) identification of the most suitable matrices and species for the analysis of different CECs; and 4) the application of alternative sample treatment strategies (e.g. QuEChERS or pressurized liquid extraction) is still limited and conventional solvent-extraction is the preferred choice.

Molecularly Imprinted Electrochemical Sensors: Analytical and Pharmaceutical Applications Based on Ortho-Phenylenediamine Polymerization

Background:

The molecular imprinting technique has been applied in many fields including separation, artificial antibody mimics, catalysis, sensing studies, and drug delivery. The reasons for the popularity of this technique among the researchers are high selectivity due to the cavities that are formed on the polymer surface for the specific analyte, high robustness, high durability under extreme conditions and low cost. When these advantages are combined with the advantages of electrochemical methods such as rapid response time, ease of use, cheapness and miniaturizability, Molecularly Imprinted Polymer (MIP) based electrochemical sensors turn out to be a widely-preferred sensing tool.

Objective:

This article provides the reader with information on MIP-based electrochemical sensors and reviews the applications of the MIP sensors prepared by electropolymerization of orthophenylenediamine, a monomer whose mechanical and chemical stability is very high.

Results and Conclusion:

The literature survey summarized in this review shows that cyclic voltammetry is the most widely preferred electrochemical technique for electropolymerization of o-PD. The media chosen is generally acetate or phosphate buffers with different pH values. Although there are numerous solvents used for template removal, generally methanol and NaOH have been chosen.

Voltammetric determination of adefovir dipivoxil by using a nanocomposite prepared from molecularly imprinted poly(o-phenylenediamine), multi-walled carbon nanotubes and carbon nitride

An electrochemical sensor for adefovir dipivoxil (ADV) detection was prepared by electropolymerization of o-phenylenediamine in the presence of ADV on a glassy carbon electrode modified with multi-walled carbon nanotubes and carbon nitride. The electrode was characterized by field emission scanning electron microscopy and differential pulse voltammetry. The performance was optimized by response surface methodology. The changes in differential pulse voltammetric peak currents of the redox probe, ferricyanide, were linear to ADV concentrations in the range from 0.1 to 9.9 μmol L^-1, with the detection limit of 0.05 μmol L^-1 (S/N = 3). The sensor was applied to the determination of ADV in drug formulations, human serum and urine samples. It is selective due to the use of an imprinted material, well reproducible, long-term stable, and regenerable. Graphical abstract By merging the unique properties of carbon nitride with intrinsic properties of MWCNTs, and molecularly imprinted polymers, a novel electrochemical sensor with selective binding sites was prepared for determination of adefovir dipivoxil in pharmaceutical and biological samples.

Recent Advances in Electrosynthesized Molecularly Imprinted Polymer Sensing Platforms for Bioanalyte Detection

The accurate detection of biological materials has remained at the forefront of scientific research for decades. This includes the detection of molecules, proteins, and bacteria. Biomimetic sensors look to replicate the sensitive and selective mechanisms that are found in biological systems and incorporate these properties into functional sensing platforms. Molecularly imprinted polymers (MIPs) are synthetic receptors that can form high affinity binding sites complementary to the specific analyte of interest. They utilise the shape, size, and functionality to produce sensitive and selective recognition of target analytes. One route of synthesizing MIPs is through electropolymerization, utilising predominantly constant potential methods or cyclic voltammetry. This methodology allows for the formation of a polymer directly onto the surface of a transducer. The thickness, morphology, and topography of the films can be manipulated specifically for each template. Recently, numerous reviews have been published in the production and sensing applications of MIPs; however, there are few reports on the use of electrosynthesized MIPs (eMIPs). The number of publications and citations utilising eMIPs is increasing each year, with a review produced on the topic in 2012. This review will primarily focus on advancements from 2012 in the use of eMIPs in sensing platforms for the detection of biologically relevant materials, including the development of increased polymer layer dimensions for whole bacteria detection and the use of mixed monomer compositions to increase selectivity toward analytes.

Molecularly imprinted polymers for sample preparation and biosensing in food analysis: Progress and perspectives

Molecularly imprinted polymers (MIPs) are biomimetics which can selectively bind to analytes of interest. One of the most interesting areas where MIPs have shown the biggest potential is food analysis. MIPs have found use as sorbents in sample preparation attributed to the high selectivity and high loading capacity. MIPs have been intensively employed in classical solid-phase extraction and solid-phase microextraction. More recently, MIPs have been combined with magnetic bead extraction, which greatly simplifies sample handling procedures. Studies have consistently shown that MIPs can effectively minimize complex food matrix effects, and improve recoveries and detection limits. In addition to sample preparation, MIPs have also been viewed as promising alternatives to bio-receptors due to the inherent molecular recognition abilities and the high stability in harsh chemical and physical conditions. MIPs have been utilized as receptors in biosensing platforms such as electrochemical, optical and mass biosensors to detect various analytes in food. In this review, we will discuss the current state-of-the-art of MIP synthesis and applications in the context of food analysis. We will highlight the imprinting methods which are applicable for imprinting food templates, summarize the recent progress in using MIPs for preparing and analysing food samples, and discuss the current limitations in the commercialisation of MIPs technology. Finally, future perspectives will be given.

A highly sensitive metronidazole sensor based on a Pt nanospheres/polyfurfural film modified electrode

A sensitively electrochemical metronidazole sensor basing on a Pt nanospheres/polyfurfural modified glassy carbon electrode.

Molecular imprinting: perspectives and applications

This critical review presents a survey of recent developments in technologies and strategies for the preparation of MIPs, followed by the application of MIPs in sample pretreatment, chromatographic separation and chemical sensing.

Applications of molecularly imprinted polymers to the analysis and removal of personal care products: A review

Personal-care products (PCPs) involve a variety of chemicals whose persistency along with their constant release into the environment raised concern to their potential impact on wildlife and humans health. Regarded as emergent contaminants, PCPs demonstrated estrogenic activity leading to the need of new methodologies to detect and remove those compounds from the environment. Molecular imprinting starts with a complex between a template molecule and a functional monomer, which is then polymerized in the presence of a cross-linker. After template removal, the polymer will contain specific cavities. Based on a good selectivity towards the template, molecularly imprinted polymers (MIPs) have been investigated as efficient materials for the analysis and extraction of the so called emergent pollutants contaminants. Rather than lowering the limit of detections, the key theoretical advantage of MIP over existing methodologies is the potential to target specific chemicals. This unique feature, sometime named specificity (as synonym to very high selectivity) allows to use cheap, simple and/or rapid quantitative techniques such as fast separation with ultra-violet (UV) detection, sensors or even spectrometric techniques. When a high degree of selectivity is achieved, samples extracted with MIPs can be directly analyzed without the need of a separation step. However, while some papers clearly demonstrated the specificity of their MIP toward the targeted PCP, such prove is often lacking, especially with real matrices, making it difficult to assess the success of the different approaches. This review paper focusses on the latest development of MIPs for the analysis of personal care products in the environment, with particular emphasis on design, preparation and practical applications of MIPs.

A molecularly imprinted sensor based on an electrochemiluminescent membrane for ultratrace doxycycline determination

A new electrochemical luminescence sensor was developed based on a molecularly imprinted membrane prepared by electropolymerization of pyrogallol doped with alizarin red. The ECL signal was produced by the oxidation of the polypyrogallol polymer, which was then reacted with alizarin red, and enhanced by doxycycline molecules due to energy transfer.

Facile and novel electrochemical preparation of a graphene-transition metal oxide nanocomposite for ultrasensitive electrochemical sensing of acetaminophen and phenacetin

A facile and novel preparation strategy based on electrochemical techniques for the fabrication of electrodeposited graphene (EGR) and zinc oxide (ZnO) nanocomposite was developed. The morphology and structure of the EGR-based nanocomposite were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (XPS) and Raman spectroscopy. Meanwhile, the electrochemical performance of the nanocomposite was demonstrated with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Due to the synergistic effect of EGR and ZnO nanoparticles, an ultrasensitive electrochemical sensor for acetaminophen (AC) and phenacetin (PCT) was successfully fabricated. The linearity ranged from 0.02 to 10 μM for AC and 0.06 to 10 μM for PCT with high sensitivities of 54,295.82 μA mM(-1) cm(2) for AC and 21,344.66 μA mM(-1) cm(2) for PCT, respectively. Moreover, the practical applicability was validated to be reliable and desirable in pharmaceutical detections. The excellent results showed the promise of the proposed preparation strategy of EGR-transition metal oxide nanocomposite in the field of electroanalytical chemistry.

Voltammetric Studies on Gold Electrodes Coated with Chitosan-Containing Layer-by-Layer Films

Gold (Au) electrodes coated with layer-by-layer (LbL) thin films composed of chitosan (CHI) were prepared to evaluate the redox properties of hexaammine ruthenium ions, Ru(NH₃)₆3+, and ferricyanide ions, Fe(CN)₆3- LbL films were prepared on an Au electrode by electrostatic LbL deposition using polycationic CHI and poly(vinyl sulfate) (PVS) or poly(acrylic acid) (PAA) as anionic component. Redox peak current in cyclic voltammetry of Ru(NH₃)₆3+ on the CHI/PVS and CHI/PAA film-coated electrodes increased with increasing thickness of the films. Interestingly, the cyclic voltammograms showed two pair of redox peaks, originating from Ru(NH₃)₆3+ diffusing across the LbL layers and from those confined in the film. The results were rationalized in terms of the electrostatic interactions between Ru(NH₃)₆3+ and excess negative charges in the LbL films originating from PVS and PAA. In contrast, Fe(CN)₆3- was not confined in the LbL films due to electrostatic repulsion of Fe(CN)₆3- and excess negative charges. Significant amounts of Ru(NH₃)₆3+ were confined in the films at pH 7.0, whereas few ions were bound at pH 3.0 due to the reduced net negative charge in the films. The results suggest a potential use of the CHI-containing LbL films as scaffold for immobilizing positively charged ionic species on the electrode surface.