What Is Left for Real-Life Lactate Monitoring? Current Advances in Electrochemical Lactate (Bio)Sensors for Agrifood and Biomedical Applications

Monitoring of lactate is spreading from the evident clinical environment, where its role as a biomarker is notorious, to the agrifood ambit as well. In the former, lactate concentration can serve as a useful indicator of several diseases (e.g., tumour development and lactic acidosis) and a relevant value in sports performance for athletes, among others. In the latter, the spotlight is placed on the food control, bringing to the table meaningful information such as decaying product detection and stress monitoring of species. No matter what purpose is involved, electrochemical (bio)sensors stand as a solid and suitable choice. However, for the time being, this statement seems to be true only for discrete measurements. The reality exposes that real and continuous lactate monitoring is still a troublesome goal. In this review, a critical overview of electrochemical lactate (bio)sensors for clinical and agrifood situations is performed. Additionally, the transduction possibilities and different sensor designs approaches are also discussed. The main aim is to reflect the current state of the art and to indicate relevant advances (and bottlenecks) to keep in mind for further development and the final achievement of this highly worthy objective

Molecularly imprinted polymer-based sensors for priority pollutants

Globally, there is growing concern about the health risks of water and air pollution. The U.S. Environmental Protection Agency (EPA) has developed a list of priority pollutants containing 129 different chemical compounds. All of these chemicals are of significant interest due to their serious health and safety issues. Permanent exposure to some concentrations of these chemicals can cause severe and irrecoverable health effects, which can be easily prevented by their early identification. Molecularly imprinted polymers (MIPs) offer great potential for selective adsorption of chemicals from water and air samples. These selective artificial bio(mimetic) receptors are promising candidates for modification of sensors, especially disposable sensors, due to their low-cost, long-term stability, ease of engineering, simplicity of production and their applicability for a wide range of targets. Herein, innovative strategies used to develop MIP-based sensors for EPA priority pollutants will be reviewed. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Real-Time Water Quality Monitoring with Chemical Sensors

Water quality is one of the most critical indicators of environmental pollution and it affects all of us. Water contamination can be accidental or intentional and the consequences are drastic unless the appropriate measures are adopted on the spot. This review provides a critical assessment of the applicability of various technologies for real-time water quality monitoring, focusing on those that have been reportedly tested in real-life scenarios. Specifically, the performance of sensors based on molecularly imprinted polymers is evaluated in detail, also giving insights into their principle of operation, stability in real on-site applications and mass production options. Such characteristics as sensing range and limit of detection are given for the most promising systems, that were verified outside of laboratory conditions. Then, novel trends of using microwave spectroscopy and chemical materials integration for achieving a higher sensitivity to and selectivity of pollutants in water are described

Recent Trends in Monitoring of European Water Framework Directive Priority Substances Using Micro-Sensors: A 2007–2009 Review

This review discusses from a critical perspective the development of new sensors for the measurement of priority pollutants targeted in the E.U. Water Framework Directive. Significant advances are reported in the paper and their advantages and limitations are also discussed. Future perspectives in this area are also pointed out in the conclusions. This review covers publications appeared since December 2006 (the publication date of the Swift report). Among priority substances, sensors for monitoring the four WFD metals represent 81% of published papers. None of analyzed publications present a micro-sensor totally validated in laboratory, ready for tests under real conditions in the field. The researches are mainly focused on the sensing part of the micro-sensors. Nevertheless, the main factor limiting micro-sensor applications in the environment is the ruggedness of the receptor towards environmental conditions. This point constitutes the first technological obstacle to be overcome for any long-term field tests

A new potentiometric sensor for determination and screening phenylalanine in blood serum based on molecularly imprinted polymer

Methods routinely utilized for detection of phenylalanine in new-born blood consist of enzymatic assays, lacking sensitivity and HPLC assays which are expensive and timeconsuming to conduct. We, here, report for the first time, the construction of a phenylalanine sensitive electrode, on the basis of a selective molecularly imprinted polymer, offering sensitivity, economy and ease of use for the measurement of phenylalanine. The sensor was constructed of a graphite-rod electrode which was coated by MIP embedded polymer base made from polyvinyl chloride and plasticizer mixture, dissolved in THF. At optimized conditions the electrode revealed a Nernstian response 29.73 ± 1.0 mV decade-1 in a concentration range of 1 � 10�� to 1 � 10-4 M with detection limit of 5 � 10�� M. The potential response of the electrode was constant in the pH range of 4.0�7.5. The electrode unfolded a response time of ~20 sec. The selectivity coefficient of the sensor towards a number of different amino acids with molecular similarities and some metal ions was evaluated. The sensor was successfully used for determination of phenylalanine in blood serum and the results were in good compatibility with HPLC method. © 2019, Iranian Journal of Pharmaceutical Research. All rights reserved

The development of molecularly imprinted polymers for sensor and colorimetric assay applications

The development of devices capable of sensing the presence or absence of molecules is a staple of the modern day world, with fields such as healthcare, forensics, agriculture and industrial processing relying upon biosensors to operate. The presented work sets focus on the use of Molecularly Imprinted Polymers (MIPs) as receptor elements in biosensing applications, demonstrating how these synthetic alternatives to traditional affinity reagents are of value. The thesis initially gives a detailed overview of the current MIP landscape, before determining areas of the field that are currently underdeveloped. The ensuing research highlights how these areas can be built upon, deploying MIPs for drug analysis and antibiotic detection. To this end, the use of MIPs in conjugation with a thermal biosensing platform is presented before shifting the research towards the use of these synthetic receptors in simple colorimetric assays designed for the rapid analysis of compounds

Applications of Graphene Quantum Dots in Biomedical Sensors

Due to the proliferative cancer rates, cardiovascular diseases, neurodegenerative disorders, autoimmune diseases and a plethora of infections across the globe, it is essential to introduce strategies that can rapidly and specifically detect the ultralow concentrations of relevant biomarkers, pathogens, toxins and pharmaceuticals in biological matrices. Considering these pathophysiologies, various research works have become necessary to fabricate biosensors for their early diagnosis and treatment, using nanomaterials like quantum dots (QDs). These nanomaterials effectively ameliorate the sensor performance with respect to their reproducibility, selectivity as well as sensitivity. In particular, graphene quantum dots (GQDs), which are ideally graphene fragments of nanometer size, constitute discrete features such as acting as attractive fluorophores and excellent electro-catalysts owing to their photo-stability, water-solubility, biocompatibility, non-toxicity and lucrativeness that make them favorable candidates for a wide range of novel biomedical applications. Herein, we reviewed about 300 biomedical studies reported over the last five years which entail the state of art as well as some pioneering ideas with respect to the prominent role of GQDs, especially in the development of optical, electrochemical and photoelectrochemical biosensors. Additionally, we outline the ideal properties of GQDs, their eclectic methods of synthesis, and the general principle behind several biosensing techniques.DFG, 428780268, Biomimetische Rezeptoren auf NanoMIP-Basis zur Virenerkennung und -entfernung mittels integrierter Ansätz

Molecularly imprinted polymers and their application as environmental sensors

Molecularly imprinted polymers are specialty polymers with ability of selectively capturing target molecules. They show great potential to be environmental sensors for the detection of specific contaminant. The overall research objective is to investigate the sensing ability of MIPs based on two mechanisms fluorescence quenching and reflectance for two example contaminants 2, 4-dinitrotoluene and 2-butoxylethanol, which are fingerprinting contaminant of explosive manufacturing and hydraulic fracking. The water chemistry effects are explored on MIPs for their potential use as in-situ sensors in complex aquatic environments. Fluorescent carbon dots with different surface functionality were fabricated and their environmental fate was explored. Amino-functionalized carbon dots (AC-dots) were applied to fluorescently label a molecularly imprinted polymer (MIP) for 2, 4-dinitrotoluene (DNT) as a template. DNT is specifically captured by the cavities in the MIP and interact with AC-dots on the surface, resulting in quenching of the fluorescence of the AC-dots. Response to DNT reaches equilibrium within [about]30 min. The method has a dynamic range that extends from 1 to 15 ppm, and allows for quantitation of DNT in aqueous solutions, with a detection limit of 0.28 ppm. Selectivity tests conducted in presence of DNT analogs demonstrated the specific recognition of DNT. The effect of sample water chemistry on carbon dots labeled molecularly imprinted polymer (AC-MIP) sensor the detection of 2, 4-dinitrotoluene (DNT) was investigated. With the increase of ionic strength from 1 mM to 100 mM, the quenching amount of MIPs decreased about 19% and 30% with NaCl and CaCl2 respectively. In the range of pH from 4 to 9, quenching effect is slightly higher at basic environment for both MIPs and non-imprinted polymers (NIPs) resulting from swelling properties of the films. NOM added the quenching amount to the sensor with a modified equation developed with NOM as a variable. In both lake water and tap water, DNT concentrations read by the sensors were very close to the HPLC measured DNT concentrations with the range from 72% to 105%. Molecularly imprinted polymers (MIPs) sensors for detection of 2-butoxyethanol (2BE), a pollutant associated with hydraulic fracturing contamination, were developed based on the combination of a colloidal crystal templating method and a molecular imprinting technique. MIPs exhibited higher binding than non-imprinted films (NIPs) due to the specific adsorption provided by molecular imprinting with imprinting efficiencies around 2. Optical tests were performed because of the uniformly ordered porous structure. The reflectance spectra of the sensors showed Bragg's peaks, which responded to the presence of 2BE; peaks presented increasing red shifts up to 50 nm with 2BE concentrations in the range of 1 ppb to 100 ppm, which allowed quantitative estimates of present 2BE concentration in aqueous solutions. The material has the potential for early detection of hydraulic fracturing sites contamination.Includes biblographical reference

A Bifunctional Nanocomposites Based Electrochemical Biosensor for In-field Detection of Pathogenic Bacteria in Food

This research focused on the application of electrochemical biosensors for the rapid detection of pathogenic bacteria, Escherichia coli O157:H7 and Salmonella Typhimurium, in foods. The possible presence of pathogenic bacteria in foods has always been a great threat to the wellbeing of people and the revenue of food companies. Therefore, the demand for rapid and sensitive methods to detect foodborne pathogens is growing. In this research, an impedimetric immunosensor was first developed for the rapid detection of E. coli O157:H7 and S. Typhimurium in foods. It was based on the techniques of immunomagnetic separation, enzyme labelling, and electrochemical impedance spectroscopy (EIS). This impedimetric immunosensor was capable of specifically detecting E. coli O157:H7 and S. Typhimurium within the range of 102 to 106 colony forming unit (cfu)/ml in the pure culture. The limits of detection (LODs) of E. coli O157:H7 in ground beef and S. Typhimurium in chicken carcass rinse water were 2.05 x 103 cfu/g and 1.04 x 103 cfu/ml, respectively. The second electrochemical biosensor was designed for rapid detection of E. coli O157:H7. This biosensor integrated magnetic GOx-polydopamine (PDA) based polymeric nanocomposites (PMNCs) which served dual functions as both the carrier and the label, and Prussian blue (PB) modified SP-IDMEs for measurement. The core-shell Abs/GOxext/gold nanoparticles (AuNPs)/magnetic beads (MBs)-GOx@PDA PMNCs acted efficiently to get a high load of enzyme onto the surface of bacterial cells. A filtration step separated the free PMNCs from the bonded ones and reduce the background noise to achieve better sensitivity. The constructed biosensor had been proved to be able to detect E. coli O157:H7 with the LOD of 52 cfu/ml in the pure culture. The third electrochemical aptasensor was developed to detect S. Typhimurium based on the concept of the bifunctional nanocomposites. The ssDNA aptamers were used as the biorecognition element. The achieved LOD in the pure culture was 96 cfu/ml. The biosensors developed in this research exhibited good specificity, reproducibility, and easy-to-operate, and are expected to find broad applications in the detection, especially in-field detection, of foodborne pathogens