Multicolor enzyme-linked immunosorbent sensor for sensitive detection of organophosphorus pesticides based on TMB2+-mediated etching of gold nanorods

Aptamer-modified paper-based analytical devices for the detection of food hazards: Emerging applications and future perspective

Food analysis plays a critical role in assessing human health risks and monitoring food quality and safety. Currently, there is a pressing need for a reliable, portable, and quick recognition element for point-of-care testing (POCT) to better serve the demands of on-site food analysis. Aptamer-modified paper-based analytical devices (Apt-PADs) have excellent characteristics of high portability, high sensitivity, high specificity, and on-site detection, which have been widely used and concerned in the field of food safety. The article reviews the basic components and working principles of Apt-PADs, and introduces their representative applications detecting food hazards. Finally, the advantages, challenges, and future directions of Apt-PADs-based sensing performance are discussed, to provide new directions and insights for researchers to select appropriate Apt-PADs according to specific applications.

Algae-derived biochar nanozyme array for discrimination and detection of multiple pesticides in soil, water and food

Despite the potential of nanozymes combined with sensor arrays for discriminating multiple pesticides simultaneously, they have few practical pesticide sensing uses due to the limited performance of existing nanozymes and the complexity of their preparation. Here, agricultural waste is utilized for the facile synthesis of high-performance biochar nanozymes and the fabrication of biochar nanozyme sensor arrays. The production of autogenous N-doped biochars with abundant surface functional groups and good peroxidase-like activities is achieved with different types of algae. High-performance biochar nanozyme sensor arrays can discriminate pesticides in a concentration range from 1 to 500 μM and in real samples from soil, lake water, seawater, apples, cucumbers, peaches, tomatoes and cabbages. Furthermore, pesticides can be quantified down to 1 μM. The development of high-performance nanozyme sensor arrays based on waste conversion could be a step toward pesticide discrimination and detection, which would improve human and environmental safety.

Nanomaterials for detection of biomolecules and delivering therapeutic agents in theragnosis: A review

Nanomaterials are emerging facts used to deliver therapeutic agents in living systems. Nanotechnology is used as a compliment by implementing different kinds of nanotechnological applications such as nano-porous structures, functionalized nanomaterials, quantum dots, carbon nanomaterials, and polymeric nanostructures. The applications are in the initial stage, which led to achieving several diagnoses and therapy in clinical practice. This review conveys the importance of nanomaterials in post-genomic employment, which includes the design of immunosensors, immune assays, and drug delivery. In this view, genomics is a molecular tool containing large databases that are useful in choosing an apt molecular inhibitor such as drug, ligand and antibody target in the drug delivery process. This study identifies the expression of genes and proteins in analysis and classification of diseases. Experimentally, the study analyses the design of a disease model. In particular, drug delivery is a boon area to treat cancer. The identified drugs enter different phase trails (Trails I, II, and III). The genomic information conveys more essential entities to the phase I trials and helps to move further for other trails such as trails-II and III. In such cases, the biomarkers play a crucial role by monitoring the unique pathological process. Genetic engineering with recombinant DNA techniques can be employed to develop genetically engineered disease models. Delivering drugs in a specific area is one of the challenging issues achieved using nanoparticles. Therefore, genomics is considered as a vast molecular tool to identify drugs in personalized medicine for cancer therapy.

Organophosphorus pesticide contaminants in fruits and vegetables: A meta-analysis

The worldwide demand for organophosphorus pesticides (OPs) in food production has raised concerns about pesticide residues. Meta-analysis, proven effective in assessing contaminants like aflatoxins and organotin compounds, is applied here to comprehensively study OP contamination in fresh fruits and vegetables. Employing Comprehensive Meta-Analysis V3.0 software, we meticulously examined 24 relevant articles encompassing 69,467 data points. Our findings revealed that while the residual concentrations of OPs (such as chlorpyrifos and profenofos) in most fruits and vegetables have typically met international or national safety standards, including Codex Alimentarius Commission, European Union, British, and Chinese standards, there are some instances in which the maximum residue limits have been exceeded, posing safety risks. Therefore, significant efforts are required to maintain residual OP contamination at safe concentrations.

Fast and Facile Etching of Gold Nanorods by N-Halosuccinimides: Toward Multicolorimetric Identification and Quantification of 20 Natural Amino Acids

Gold nanorods (AuNRs) have recently become fascinating chromophores in the field of colorimetric sensing because of their eye-catching rainbow colors along with the high dimensionality of their optical profile. The etching of AuNRs using an analyte-sensitive oxidizing agent is particularly an attractive tool not only for adjusting their plasmonic behavior through altering their aspect ratio but also for correlating the observed signal with the identity and concentration of the analyte. However, the deployment of this strategy in the field of sensing has been seriously hindered by various factors ranging from slow etching kinetics and the need for nonambient temperatures to low degrees of controllability along with the high toxicity of the etchants. To resolve these challenges, the present study aims to introduce the outstanding potentials of two inexpensive mild oxidants comprising N-bromosuccinimide (NBS) and N-chlorosuccinimide (NCS) in the highly fast and controllable etching of AuNRs at room temperature. By controlling the concentration of the etchant and the pH of the medium, the longitudinal and transversal peaks could be well adjusted with nanometer precision. In an attempt to elucidate the etching mechanism, the effects of various parameters including the etchant concentration and pH, as well as the kinetics of the etching process were thoroughly investigated. After all, the capability of NBS in decarboxylating the amino acids was further exploited in the design of an all-inclusive multicolorimetric sensor array based on the etching of AuNRs for the sensitive quantification and highly accurate discrimination of all 20 amino acids in the micromolar range. To this end, the acquired data set was analyzed by two machine learning techniques including partial least-squares regression (PLSR) and linear discriminant analysis (LDA). The versatility of N-halosuccinimide reactions with various categories of organic compounds underlies ample opportunities for the design of diverse multicolorimetric sensors, further glamorizing the prospect of this approach.

Research advances of SERS analysis method based on silent region molecules for food safety detection

Food safety is a critical issue that is closely related to people's health and safety. As a simple, rapid, and sensitive detection technique, surface-enhanced Raman scattering (SERS) technology has significant potential for food safety detection. Recently, researchers have shown a growing interest in utilizing silent region molecules for SERS analysis. These molecules exhibit significant Raman scattering peaks in the cellular Raman silent region between 1800 and 2800 cm-1 avoiding overlapping with the SERS spectrum of biological matrices in the range 600-1800 cm-1, which could effectively circumvent matrix effects and improve the SERS accuracy. In this review, the application of silent region molecules-based SERS analytical technique for food safety detection is introduced, detection strategies including label-free detection and labeled detection are discussed, and recent applications of SERS analysis technology based on molecules containing alkyne and nitrile groups, as well as Prussian blue (PB) in the detection of pesticides, mycotoxins, metal ions, and foodborne pathogens are highlighted. This review aims to draw the attention to the silent region molecules-based SERS analytical technique and to provide theoretical support for its further applications in food safety detection.

Two Fe(III)/Eu(III) Salophen complex-based optical sensors for determination of organophosphorus pesticide monocrotophos

Monocrotophos (MP), an organophosphorus pesticide, poses a serious threat to human health, so a rapid and simple technique is needed to detect it. In this study, two novel optical sensors for MP detection were created using the Fe(III) Salophen complex and Eu(III) Salophen complex, respectively. One sensor is an Fe(III) Salophen complex (I-N-Sal), which can bind MP selectively and form a supramolecule, resulting in a strong resonance light scattering (RLS) signal at 300 nm. Under the optimum conditions, the detection limit was 30 nM, the linear range was 0.1-1.1 μM, the correlation coefficient R² = 0.9919, and the recovery rate range was 97.0-103.1%. Interaction properties between the sensor I-N-Sal and MP and the RLS mechanism were investigated using density functional theory (DFT). And another sensor is based on the Eu(III) Salophen complex and 5-aminofluorescein derivatives. The Eu(III) Salophen complex was immobilized on the surface of amino-silica gel (Sigel-NH₂) particles as the solid phase receptor (ESS) of MP and 5-aminofluorescein derivatives as the fluorescent (FL)-labeled receptor (N-5-AF) of MP, which can selectively bind the MP and form a sandwich-type supramolecule. Under the optimum conditions, the detection limit was 0.4 μM, the linear range was 1.3-7.0 μM, the correlation coefficient R² = 0.9983, and the recovery rate range was 96.6-101.1%. Interaction properties between the sensor and MP were investigated by UV-vis, FT-IR, and XRD. Both sensors were successfully applied to the determination of MP content in tap water and camellia.

Sensor technologies for the detection and monitoring of endocrine-disrupting chemicals

Endocrine-disrupting chemicals (EDCs) are a class of man-made substances with potential to disrupt the standard function of the endocrine system. These EDCs include phthalates, perchlorates, phenols, some heavy metals, furans, dimethoate, aromatic hydrocarbons, some pesticides, and per- and polyfluoroalkyl substances (PFAS). EDCs are widespread in the environment given their frequent use in daily life. Their production, usage, and consumption have increased many-fold in recent years. Their ability to interact and mimic normal endocrine functions makes them a potential threat to human health, aquatics, and wild life. Detection of these toxins has predominantly been done by mass spectroscopy and/or chromatography-based methods and to a lesser extent by advanced sensing approaches such as electrochemical and/or colorimetric methods. Instrument-based analytical techniques are often not amenable for onsite detection due to the lab-based nature of these detecting systems. Alternatively, analytical approaches based on sensor/biosensor techniques are more attractive because they are rapid, portable, equally sensitive, and eco-friendly. Advanced sensing systems have been adopted to detect a range of EDCs in the environment and food production systems. This review will focus on advances and developments in portable sensing techniques for EDCs, encompassing electrochemical, colorimetric, optical, aptamer-based, and microbial sensing approaches. We have also delineated the advantages and limitations of some of these sensing techniques and discussed future developments in sensor technology for the environmental sensing of EDCs.

Selection and electrochemical-sensor application of an DNA-aptamer for methyl parathion detection

An aptamer-based electrochemical sensor for methyl parathion (MP) detection is herein reported. The modified magnetic beads-systematic evolution of ligands by enrichment (MB-SELEX) was used to select the MP aptamer. After 14 rounds of selection, the aptamer (MPapta-6) with high affinity for MP was obtained, and its dissociation constant (K_d) was 39.66 ± 14.73 μM. Using the MPapta-6, the ultra-sensitive electrochemical sensor based on PLL-BP and AuNPs was constructed. The linear range of MP was 1-10⁵ pM and detection limit (LOD) was as low as 0.49 pM. In addition, the application of the sensor in water samples was verified, and the recovery rate was 96.6%-103.5%. The results from this study showed that this strategy could be applied in practical detection.

Multicolor Biosensor for Trypsin Detection Based on the Regulation of the Peroxidase Activity of Bovine Serum Albumin-Coated Gold Nanoclusters and Etching of Gold Nanobipyramids

The detection of trypsin is significantly important for both clinical diagnosis and disease treatment. In this study, an innovative multicolor sensor for trypsin detection has been established based on the regulation of the peroxidase activity of bovine serum albumin-coated gold nanoclusters (BSA-Au NCs) and efficient etching of gold nanobipyramids (Au NBPs). BSA-Au NCs have slight peroxidase enzyme activity and can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to generate TMB⁺, while trypsin can hydrolyze BSA ligands on the surface of BSA-Au NCs, thus exposing more catalytic active sites of BSA-Au NCs and resulting in the enhancement of the peroxidase activity of BSA-Au NCs, hence more TMB⁺ is generated. Under acidic conditions, TMB⁺ can etch Au NBPs efficiently, consequently affecting the aspect ratio of Au NBPs accompanied by the ultraviolet-visible (UV-vis) spectra blue shifting of the system. Furthermore, this also results in color variations that can be distinguished and recognized by naked eyes without any expensive and sophisticated instruments. This multicolor sensor has an available linear relationship with the logarithm of the trypsin concentration in the range of 0.1-100 μg/mL, and the detection limit is 0.045 μg/mL. The designed sensor has been used to detect the concentration of trypsin in human serum samples from healthy individuals and pancreatitis patients with satisfactory results.

Optical sensing techniques for rapid detection of agrochemicals: Strategies, challenges, and perspectives

In recent years, the irrational use of agrochemicals has caused great harm to the environment and public health. Along with the rapid development of optical technology and nanotechnology, the research of optical sensing methods in agrochemical detection has been developed rapidly owing to its advantages of simplicity, fast response, and cost-effectiveness. In this review, the strategies of employing optical systems based on colorimetric sensor, fluorescence, chemiluminescence, terahertz spectroscopy, surface plasmon resonance, and surface-enhanced Raman spectroscopy for sensing agrochemicals were summarized. In addition, the challenges in the practical application of optical sensing technologies for agrochemical detection were discussed in-depth, and potential future trends and prospects of these techniques were addressed. A variety of nanomaterials have been developed for enhancing the sensitivity of optical sensing systems. The optical properties of nanomaterials are governed by their size, shape, and chemical structure. Although each optical sensing system holds its advantages, there are still many challenges that need to be overcome in practical applications. With the continuous developments in novel functional nanomaterials, sample preparation methods, and spectral processing algorithms, optical sensors are expected to have powerful potential for rapid testing of agrochemicals in the environment and foods.

A comprehensive review on electrochemical and optical aptasensors for organophosphorus pesticides

There has been a rise in pesticide use as a result of the growing industrialization of agriculture. Organophosphorus pesticides have been widely applied as agricultural and domestic pest control agents for nearly five decades, and they remain as health and environmental hazards in water supplies, vegetables, fruits, and processed foods causing serious foodborne illness. Thus, the rapid and reliable detection of these harmful organophosphorus toxins with excellent sensitivity and selectivity is of utmost importance. Aptasensors are biosensors based on aptamers, which exhibit exceptional recognition capability for a variety of targets. Aptasensors offer numerous advantages over conventional approaches, including increased sensitivity, selectivity, design flexibility, and cost-effectiveness. As a result, interest in developing aptasensors continues to expand. This paper discusses the historical and modern advancements of aptasensors through the use of nanotechnology to enhance the signal, resulting in high sensitivity and detection accuracy. More importantly, this review summarizes the principles and strategies underlying different organophosphorus aptasensors, including electrochemical, electrochemiluminescent, fluorescent, and colorimetric ones.

Enzyme-assisted metal nanoparticles etching based plasmonic ELISA: Progress and insights

The unique size and shape tunable localized surface plasmon resonance (LSPR) properties of the noble metal nanoparticle have been extensively exploited to realize a variety of enzyme-based optical biosensors. Although approaches like metal film deposition, nanoparticle aggregation, and synthesis & growth of metal nanoparticles are quite useful, metal nanoparticle etching-based biosensors offer greater sensitivity, selectivity, and stability against various environmental factors which makes this strategy easy to use for field applications. This review discusses the current state-of-art of plasmonic nanoparticle etching-based enzyme-linked immunosorbent assay (ELISA) realized for visual detection of various analytes. The naked eye detection, i.e. without any optical readout device, is the additional advantage of this sensing approach that reduces the analysis cost significantly making it feasible under resource-constrained settings. This review paper provides deeper insights into biocatalytic etching mechanisms of various plasmonic nanoparticles resulting in vivid color change as a function of analyte concentration. Although nanoparticle etching-based ELISA has huge potential, steps need to be taken to realize a point-of-care (POC) nanodiagnostic before its translation to a commercial technique or product that can be achieved in near future by integrating it with microfluidics technology and other technological avenues.