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Background Synthetic chemical pesticides play a significant role in increasing the overall yield and productivity of agricultural foods by controlling and eradicating pests, insects, and numerous plant-related diseases. The over-spraying of pesticides onto crops has escalated pesticide contamination of food products and water bodies, as well as disturbing ecological and environmental systems. In this regard, developing simple, low-cost, and rapid-sensing strategies and portable devices for the precise, efficient, rapid, and on-site detection of pesticide residues in agricultural fields is indeed necessary and urgently required for the wellbeing and safety of mankind and other species. Scope and approach In this review, we make a comprehensive study of the up-to-date state-of-the-art research progress on the on-site sensing strategies and portable devices for the detection of pesticide residues in agricultural foods using paper-, liquid-, and gel-based optical-sensing techniques. Moreover, we delineate the detailed on-site detection mechanism and sensing behavior of the aforementioned strategies and discuss the challenges and future perspectives associated with the development of optical techniques. Key findings and conclusions Recent scientific and technological studies on optical sensors such as fluorescence sensors, target-responsive hydrogels, chemiluminescence assay, tube enzyme-linked immunosorbent assay, enzymatic fiber-optic biosensor, phosphorescence, lateral flow immunoassay, double-signal fluorescence strategy, wearable glove-based sensors, and paper-based sensors have made novel advancements and brought scientific insight for the on-site detection of pesticide residues in agricultural foods. This review provides significant insights and future perspectives that might serve as the basis for the fabrication of novel optical sensors with applicability in various fields.

Traditional laboratory-based sensing strategies for food contaminant detection are often limited because they are time-consuming and expensive and require trained personnel, which makes them unsuitable for routine sensing. Therefore, the scientific and industrial community is showing enormous interest in the design and development of portable sensing devices for the on-site and point-of-care detection of food contaminants. Portability is one of the chief characteristic features of designing contemporary analytical devices. Portable devices have received tremendous attention, as these novel devices have advanced the field of sensing. Various sensing strategies have been utilized for on-site detection of food contaminants. Among these, portable electrochemical devices have emerged vigorously in the past few years. Scientists and industrialists have worked effortlessly to develop portable electrochemical devices for a minute amount of food contaminant detection in water bodies and food products. The current work aims to demonstrate recent research progress related to the design, development, and improvement of portable electrochemical devices for detection of food contaminants.

Over the past few decades, electrochemiluminescence (ECL) has been used as a powerful analytical tool for in vitro diagnosis due to its promising potential in light-emitting and, which has greatly promoted recent for biosensor studies. Plenty of research articles on the ECL technique have been published by various researchers around the globe. On the other hand, studies on the coupling of ECL sensing strategies with other techniques are recently getting widespread attention. ECL strategies have been effectively coupled with scanning electrochemical microscope (SECM), flow injection analysis (FIA), and capillary electrophoresis. These coupled techniques have been effectively employed for various health care applications. Among these techniques, FIA coupled ECL sensing strategies have been designated as the most emerging technique, especially sensing of clinical samples. This critical review discusses the vibrant developments in FIA-ECL, the mechanism of ECL, the design of FIA-ECL, and highlights the application of FIA-ECL for the detection of immunoassays, catecholamines, antioxidant compounds, choline, tetracyclines, and pharmaceutical drugs. The current review will pave the way for the design and development of FIA-ECL for efficient point-of-care applications.

Pesticide residues are posing an increasing threat to ecosystems and human health due to the over-application of synthetic pesticides in pest control to meet the global demand for agricultural food products. In this regard, electrochemical sensor and biosensor platforms have emerged as powerful analytical methods to detect pesticides due to several advantages, including synergistic aspects, systematic fabrication procedure, ease of detection, appreciable sensitivity, and selectivity. Furthermore, portable electrochemical devices have been fabricated recently for point-of-care and on-site detection of pesticides residues. This comprehensive review focuses on recent advances in portable electrochemical (bio)sensing methods for the on-site detection of pesticide residues in fruits and vegetables. Moreover, detailed information has been provided on the principal mechanism and electrochemical (bio)sensing behavior of the specified strategies. Discussed the significant developments in electrochemical strategies and the integration of smartphone technology with electrochemical sensing platforms for real-time monitoring. It is anticipated that the current review will be an added advantage and valuable tool for scientific and technological readers to understand the fabrication of portable electrochemical devices, the role of electrochemical (bio)sensing strategies for rapid on-site detection of pesticides, and to promote further developments in agricultural science, electrochemical science, and food science and technology.

Agricultural food crop yields have increased enormously due to the implementation of chemical pesticides; however, their excessive and uncontrolled use has led to food contamination, as well as environmental, aquatic, and agricultural pollution. Therefore, on-site monitoring of pesticide residues in agricultural food products is crucial to ensure global food and environmental safety. Conventional pesticide detection strategies are time-consuming and unsuitable for on-site or on-field detection of pesticides. Among the current approaches for field detection of pesticides, including colorimetric, non-colorimetric, electrochemical, and optical sensing strategies, colorimetric sensing strategies exhibit the most promising potential for the on-site detection of pesticide residues due to their quick detection, easy fabrication, and high selectivity and sensitivity, in addition to being readable by the naked eye. Nonetheless, although pesticide quantification methods have been extensively described in the literature, only a few studies have conducted on-site pesticide residue analyses. Therefore, this study provides a comprehensive overview of the major advances in colorimetric sensing approaches based on nanoparticle aggregation, label-free hydrogel particles, lateral flow immunoassays (LFAs), integrated digital readers, portable field detection, and paper-based sensors for the on-site detection of pesticide residues in food crops. Moreover, this review also compares the analytical performances of the aforementioned strategies and discusses the new horizons, perspectives, and challenges associated with the development of portable devices. Therefore, we believe that this review provides important insights that might serve as the basis for the fabrication of novel colorimetric sensors with applicability in materials science, environmental science, food science, nanoscience, and biotechnology.

Continuing efforts to develop stimuli-responsive polymers (SRPs) as novel smart materials/biomaterials are anticipated to upgrade the quality life of humans. The details of the molecular, physico chemical and biophysical interactions between SRPs and proteins are not fully understood. Indeed, protein - polymer interactions play a major role in a wide range of biomedical/biomaterial applications. In this regard, we have demonstrated the influence of proteins (β-lactoglobulin (BLG) and stem bromelain (BM) as biological stimuli) on the phase transition behavior of biomedical thermoresponsive poly(N-isopropylacrylamide) (PNIPAM). In order to predict these, we have used a set of biophysical techniques to unveil the influence of biological stimuli on the phase transition behavior of PNIPAM. Absorption spectroscopy, steady-state fluorescence spectroscopy, Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM) were operated at room temperature to examine the changes in absorbance, fluorescence intensity, molecular interactions and surface morphologies, respectively. Furthermore, temperature dependent fluorescence spectroscopy and dynamic light scattering (DLS) studies were also performed to analyze conformational changes, agglomeration behavior, particle size, coil to globule transition and phase behavior. The significant variations obtained in the phase transition temperature values, conformational changes and agglomeration behavior clearly reflects the different molecular interplay induced in presence of biological stimuli. The results demonstrated that the added proteins act as biological stimuli via preferential interactions between the amide group of the polymer and water molecules. The present study can be useful for the design and development of the next generation smart responsive materials/biomaterials.

Hypothesis Thorough knowledge of the biomolecular interactions between thermoresponsive polymers (TRPs) and proteins are necessary to fabricate potential materials for various bio-related science and technology applications. Although over the past four decades have evidenced that tremendous growth in the utilization of TRPs in the addition of various stimuli systems, a underlying molecular origins of the role of biological stimuli on TRPs phase transition is still missing. Experiments We demonstrated the comparative effect of heme proteins (biological stimuli) such as cytochrome c (Cyt c) and myoglobin (Mb) on the phase behaviour of poly(N-isopropylacrylamide) (PNIPAM) aqueous solution. The sophisticated multiple techniques have confirmed that the structural integrity of the proteins is found to play a vital role in altering the phase transition temperature of PNIPAM to different extents with increasing the concentration of proteins. Findings With the addition of Cyt c, the lower critical solution temperature (LCST) of PNIPAM (33.0 °C) increased towards higher temperature (35.7 °C) in contrast to this with the addition of Mb the LCST of PNIPAM decreased towards lower temperature (30.7 °C). This discrepancy is due to the difference in contrast structural arrangements of both proteins on the LCST of PNIPAM. On the basis of these results, the variation in the structures of both heme proteins, hydration and dehydration between the heme proteins are compared. These results demonstrated that depending on the type of smart polymers used for bio-related applications, it is necessary to take into account the effect of biological stimuli while designing polymers. We hope that the present study can stimulate more novel concepts and dramatic changes in smart polymer and protein interactions.