Current Analytical Chemistry - Volume 18, Issue 5, 2022

The design of high-performance electrochemical sensor and biosensor platforms has attracted much interest for the sensitive and selective detection of emergent biomarkers. The electrochemical sensor offers numerous advantageous features including cost-effectiveness and ease of miniaturization, rapid and online monitoring, simultaneous detection ability, etc., which have captivated the potential interdisciplinary research. In this review, the advances and challenges towards the electrochemical detection of emergent biomarkers such as hydrogen peroxide, nitric oxide, β- nicotinamide adenine acetaminophen, dinucleotide (NADH) in biofluids are highlighted based on the recent research outcomes. In fact, the effective utility and benefits of transition metal nanocomposites without the utilization of biological materials, including enzymes, antibodies, etc., as electrode materials towards the detection of selected biomarkers in practical biofluids, monitoring early-stage and diagnosis of disease related biomarkers, are also described. These promising metal nanomaterials based electrochemical sensor platforms concrete the tactic for a new generation of sensing devices.

Background: Speciation analysis is defined as the identification and/or measurement of the quantities of one or more individual chemical species in a sample. The knowledge of elemental species provides more complete information about mobility, bioavailability and the impact of elements on ecological systems or biological organisms. It is no longer sufficient to quantitate the total elemental content of samples to define toxicity or essentiality. Thus speciation analysis is of vital importance and generally offers a better understanding of a specific element. Discussion: Thorough speciation scheme consisting of sampling, sample preparation, species analysis and evaluation was described. Special emphasis is placed on recent speciation analysis approaches, including both direct and coupling methods. An updated summary of advantages and limitations of the various methods as well as an illustrative comparison is presented. Certain elements and species of interest are briefly mentioned and practical examples of speciation applications in tobacco and other important economic crops are also discussed. Aim/Conclusion: This review aims to offer comprehensive knowledge about elemental speciation and provide readers with valuable information. Many strategies have been developed for the determination of multiple elemental species in tobacco and other important economic crops. Nevertheless, it is an eternal pursuit to establish speciation methods which can balance accuracy, agility as well as universality.

Background: Biosensors are analytical devices that include a sample-delivery approach between a biological recognition element and a transducer required to convert the physicochemical change produced from the interaction of biological molecule-receptor interaction into a signal. The immunosensor is a special type of biosensor that includes an antibody as a biorecognition element to detect analytes as antigens. In mass sensitive sensors, antigen-antibody interactions can be specified by measuring the frequency change and the most commonly knowns are the surface acoustic wave, bulk acoustic wave, quartz crystal microbalance and microcantilevers. Methods: Different methods for antibody immobilization, including functionalization of the transducer surface with specific groups, have been reported for antibody immobilization. This stage affects the limit of detection and overall performance. In this review, perspectives on immobilization strategies of mass sensitive immunosensors according to transducer types will be presented. The choice of immobilization methods and their impact on performance in terms of capture molecule loading, orientation and signal improvement will also be discussed. Results: One of the most critical points during the configuration of the biorecognition layer is to improve the sensitivity. Therefore, we initially focused on comparisons of the antibody immobilization strategies in the biorecognition layer in terms of mass load level and high sensitivity. Conclusion: The lack of significant data on the mass accumulations up to the functionalization and antibody immobilization steps, which are the basis of immusensor production, has been identified. However, mass sensitive immunosensors have the potential to become more common and effective analytical devices for many application areas.

Background: This is the first review on Poly(diphenylamine) and its nanohybrids, which covers about 181 references demonstrating the brief discussion on the theoretical studies, chemical, electrochemical and other-phase preparation techniques, polymerization and oxidation-reduction (redox) mechanisms, physicochemical and electrochemical properties along with electrochemical sensors and spectroscopic applications on the detection of chemicals and biomolecules analysis applications. Objective: The main aim of this detailed report is merely to afford a survey of the literature existing on this multifunctional conducting organic polymer (poly(diphenylamine)) that provokes a pathway to innovations and discoveries in the near future claim its applications in multidisciplinary fields, especially in the detection of chemicals and bio-molecules applications. Methods: We discussed the overall studies on poly(diphenylamine) and its various nanohybrids, including copolymers, homopolymers, carbon-based, and metal/metal-oxide hybrids. The different synthesis methods of poly(diphenylamine) such as chemical/electrochemical/mechano-chemical polymerization in terms of morphology and electrical conductivity were briefly discussed. Conclusion: This review manuscript deliberates the various synthesis approaches and applications based on the multifunctional conducting polymer poly(diphenylamine) and its nanohybrids. This review provides an outlook and challenges ahead that ignites spotlight to innovations and discoveries in the near future claims its applications in multidisciplinary fields, particularly in electrochemical sensors and spectroscopic applications towards the detection of chemicals and bio-molecules.

Background: The interest in breath analysis for non-invasive disease diagnosis of the scientific community has been increased over the past decade. This is due to the exhalation of prominent volatile organic compounds (VOCs) corresponding to the metabolic activities in the body and their concentration variation. To identify these biomarkers, various analytical techniques have been used in the past and the threshold concentration is established between a healthy and diseased state. Subsequently, various nanomaterials-based gas sensors are being explored for their demand in quantifying these biomarkers in real-time, low cost and portable breathalyzers along with the essential sensor performances. Methods: We focus on the classification of graphene derivatives and their composites’ gas sensing efficiency for the development of breathalyzers. The review begins with the feasibility of the application of nanomaterial gas sensors for healthcare applications. Then, we report the gas sensing performance of various graphene derivatives/semiconductor metal oxides (SMO) binary nanocomposites and their optimizing strategies in selective detection of biomarkers specific for diseases. Finally, we provide insights on the challenges, opportunities and future research directions for the development of breathalyzers using other graphene derivatives/SMO binary nanocomposites. Results: On the basis of these analyses, graphene and its derivatives/metal oxides based binary nanocomposites have been a choice for gas sensing material owing to their high electrical conductivity and extraordinary thickness-dependent physicochemical properties. Moreover, the presence of oxygen vacancies in SMO not only alters the conductivity but also accelerates the carrier transport rate and has an influence on the adsorption behavior of target analyte on the sensing materials. Hence, researchers are in search of ultrathin graphene and metal oxide counterpart for high sensing performance. Conclusion: The impressive properties of graphene derivatives and SMO binary nanocomposites compared to their bulk counterparts have been uncovered for sensitive and selective detection of biomarkers in portable breathalyzers.

Background: Sample preparation has gained significant recognition in the chemical analysis workflow. Substantial efforts have been made to simplify the comprehensive process of sample preparation that is focused on green sample preparation methodology, including the miniaturization of extraction method, elimination of the sample pre-treatment as well as the posttreatment steps, elimination of toxic as well as hazardous organic solvent consumption, reduction in sample volume requirements, reduction of the extraction time, maximization of the extraction efficiency and possible automation. Methods: Among various microextraction processes, liquid-phase microextraction (LPME) is most abundantly used in the extraction of the target analytes. The salting-out phenomenon has been introduced into the LPME procedure and has been raised as a new technique called the ‘Salt-Assisted Liquid-Liquid Microextraction (SALLME)’. The principle is based on decreasing the solubility of the less polar solvent or analyte with an increase in the concentration of the salt in an aqueous solution leading to two-phase separation. Results: SALLME is mainly based on the salting-out phase separation phenomenon. It is important to optimize the SALLME experimental parameters, such as solvent volume, salt amount, and extraction time, to achieve the maximum extraction capacity of the target analytes from the sample matrices. Conclusion: SALLME proved to be a simple, rapid, and cost-effective sample preparation technique for the efficient extraction and preconcentration of organic and inorganic contaminants from various sample matrices, including environmental, biological, and food samples. SALLME exhibits higher extraction efficiency and recovery and is compatible with multiple analytical instruments. This review provides an overview of developments in SALLME technique and its applications to date.

Background: Microplastics are found to be one of the major emerging contaminants in the environment. Various environmental occurrences cause the macro plastics to degrade slowly into microplastics. Microplastics present in the water bodies may enter into the fish’s body through ingestion of food and also get adsorbed onto the surface of their gills or skin. Objective: Microplastics of polyethylene were chosen to investigate their sorption capacity on fish scales. The dispersion of polyethylene microplastics was studied by using a Total Dissolved Solids meter. Using this dispersion, the sorption effect was studied, and it revealed that the microplastics had the sorption ability on the fish scales. Method: Polyethylene microplastics were chosen to investigate its sorption capacity on fish scales of Lutjanus gibbus. The sorption effect of microplastics on fish scales was performed by using polyethylene microplastics obtained by bath sonication, and the concentration was studied using a Total Dissolved Solids meter. Using polyethylene microplastics dispersion, the sorption effect was carried out on the scales of Lutjanus gibbus for ten days at 8 ^oC. The sorption of microplastics on fish scales was characterized by FE-SEM, FT-IR, and Raman spectroscopy. Results: Polymer sorption was confirmed by using optical microscopy and FE-SEM. FT-IR and Raman spectroscopy confirmed the existence of polyethylene microplastics on the fish scale. Moreover, polyethylene microplastics sorption studies were also studied at different pH, various concentrations of NaCl and at different time intervals. Conclusions: We synthesized microplastics from the bulk polyethylene by NaCl solution. This study confirmed the successful sorption of polyethylene microplastics on the fish scale. Our study revealed that marine water might be a suitable medium to facilitate the polymer sorption on aquatic animals/organisms.