Advances in fabrication of molecularly imprinted electrochemical sensors for detection of contaminants and toxicants

Construction of Ion-Imprinted Graphene Oxide Mixed-Matrix Membranes for Selective Adsorption and Separation of Tm3

Efficient adsorption and separation of rare earth from other similar rare earth wastewater has become an urgent demand for resource utilization of ion-type rare earth minerals in China. Herein, thulium (Tm) ion-imprinted graphene oxide (GO)-doped polyether sulfone (PES) membranes (GO-TII/PES-2 membranes) were prepared, in which ion-imprinted graphene oxide was applied as an efficient Tm3+ ionic ligand in the imprinted layer and polyether sulfone was applied as a carrier in the membrane matrix to achieve the selective adsorption and separation of Tm3+ and neighboring rare earth ions. Combined with an ion rectifier, the separation and purification performances of Tm3+ were explored. The separation factors β(Tm3+/Tb3+), β(Tm3+/Sm3+), β(Tm3+/Nd3+), and β(Tm3+/Ce3+) in the dynamic adsorption process increased significantly from 1.22, 1.04, 1.04, and 1.02 for nonimprinting to 3.07, 3.91, 3.91, and 3.33 for imprinted membranes. The GO-TII/PES-2 membrane adsorbed about three times more Tm3+ than the nonionic-imprinted (GO-NII/PES) membrane by adding a color developer and quantifying Tm3+ based on a fast and easy UV-photometric method. After eight dynamic permeations, the adsorption of Tm3+ by the GO-TII/PES-2 membrane decreased by only 13%, indicating that the membrane has good reuse performance. Additionally, the investigation examined the influence of Tm3+ on wheat seed germination, underscoring its potential application in agriculture and the importance of adsorbing and separating rare earth ions.

Construction of a self-reporting molecularly-imprinted electrochemical sensor based on CuHCF modified by rGNR-rGO for the detection of zearalenone

A self-reporting molecularly-imprinted electrochemical sensor is prepared for the detection of Zearalenone (ZEA). Firstly, the reduced graphene nanoribbons and reduced graphene oxide (rGNR-rGO) were simultaneously modified onto a glassy carbon electrode (GCE) to improve the sensor's sensitivity. After electrodepositing copper nanoparticles onto the rGNR-rGO/GCE, cyclic voltammetry scanning was performed in potassium ferrocyanide solution, and copper hexacyanoferrate (CuHCF) was deposited onto rGNR-rGO/GCE to further improve the sensor's sensitivity while giving it self-reporting capability. Then, molecularly-imprinted polymer films were prepared on the CuHCF/rGNR-rGO/GCE to ensure the selectivity of the sensor. It is found that the linear range of ZEA detection by the constructed sensor is 0.25-500 ng·mL -1, with a detection limit of 0.09 ng·mL -1. This sensor shows the merits of good selectivity, high sensitivity and accurate detection, providing a great possibility for the precise detection of low concentration ZEA in food.

Analysis of atorvastatin in environmental waters: Validation of an electrochemical molecularly imprinted polymer sensor with application of life cycle assessment

The widespread presence of pharmaceuticals in wastewater effluents after treatment stands as a significant challenge faced in the field of wastewater management and public health. Governments and the scientific community have worked to meet this urgent need for effective solutions. Nevertheless, the development of detection strategies for pharmaceutical monitorization capable of delivering rapid, on-site, and sensitive responses remains an ongoing necessity. In this work, the performance of a previously developed molecularly imprinted polymer (MIP) based electrochemical sensor for detecting atorvastatin (ATV) in wastewater effluents and surface waters is presented. A simple preconcentration method followed by electrochemical measurements by differential pulse voltammetry (DPV) in 0.1 M phosphate buffer (pH = 7), was implemented. The analytical results were validated with those obtained on a set of 16 water samples by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Additionally, a life cycle assessment (LCA) was conducted to compare the environmental impact of both methodologies. The results obtained demonstrated that ATV detection using MIP-sensor was reliable when compared to the results found by UHPLC-MS/MS presenting a robust linear correlation coefficient of 0.843. The LCA results show that the novel MIP-sensor technique has lower associated environmental impacts than UHPLC-MS/MS, when the current analytical protocol for pharmaceuticals detection is applied. These findings highlight the potential of the developed MIP-sensor as an eco-friendly analytical tool for routine analysis and point-of-care monitoring of ATV in WWTP wastewater and surface water samples.

Disease diagnosis and application analysis of molecularly imprinted polymers (MIPs) in saliva detection

Saliva has significantly evolved as a diagnostic fluid in recent years, giving a non-invasive alternative to blood analysis. A high protein concentration in saliva is delivered directly from the bloodstream, making it a "human mirror" that reflects the body's physiological state. It plays an essential role in detecting diseases in biomedical and fitness monitoring. Molecularly imprinted polymers (MIPs) are biomimetic materials with custom-designed synthetic recognition sites that imitate biological counterparts renowned for sensitive analyte detection. This paper reviews the progress made in research about MIP biosensors for detecting saliva biomarkers. Specifically, we investigate the link between saliva biomarkers and various diseases, providing detailed insights into the corresponding biosensors. Furthermore, we discuss the principles of molecular imprinting for disease diagnostics and application analysis, including recent advances in integrated MIP-sensor technologies for high-affinity analyte detection in saliva. Notably, these biosensors exhibit high discrimination, allowing for the detection of saliva biomarkers linked explicitly to chronic stress disorders, diabetes, cancer, bacterial or viral-induced illnesses, and exposure to illicit toxic substances or tobacco smoke. Our findings indicate that MIP-based biosensors match and perhaps surpass their counterparts featuring integrated natural antibodies in terms of stability, signal-to-noise ratios, and detection limits. Additionally, we highlight the design of MIP coatings, strategies for synthesizing polymers, and the integration of advanced biodevices. These tailored biodevices, designed to assess various salivary biomarkers, are emerging as promising screening or diagnostic tools for real-time monitoring and self-health management, improving quality of life.

An Overview on Recent Advances in Biomimetic Sensors for the Detection of Perfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFAS) are a class of materials that have been widely used in the industrial production of a wide range of products. After decades of bioaccumulation in the environment, research has demonstrated that these compounds are toxic and potentially carcinogenic. Therefore, it is essential to map the extent of the problem to be able to remediate it properly in the next few decades. Current state-of-the-art detection platforms, however, are lab based and therefore too expensive and time-consuming for routine screening. Traditional biosensor tests based on, e.g., lateral flow assays may struggle with the low regulatory levels of PFAS (ng/mL), the complexity of environmental matrices and the presence of coexisting chemicals. Therefore, a lot of research effort has been directed towards the development of biomimetic receptors and their implementation into handheld, low-cost sensors. Numerous research groups have developed PFAS sensors based on molecularly imprinted polymers (MIPs), metal-organic frameworks (MOFs) or aptamers. In order to transform these research efforts into tangible devices and implement them into environmental applications, it is necessary to provide an overview of these research efforts. This review aims to provide this overview and critically compare several technologies to each other to provide a recommendation for the direction of future research efforts focused on the development of the next generation of biomimetic PFAS sensors.

Molecularly Imprinted Electrochemical Sensors Based on Ti3C2Tx-MXene and Graphene Composite Modifications for Ultrasensitive Cortisol Detection

The increasing pressure and unhealthy lifestyle are gradually eroding the physical and mental health of modern people. As a key hormone responsible for maintaining the normal functioning of human systems, cortisol plays a vital role in regulating physiological activities. Moreover, cortisol can serve as a marker for monitoring psychological stress. The development of cortisol detection sensors carries immense potential, as they not only facilitate timely adjustments and treatments by detecting abnormal physiological indicators but also provide comprehensive data for conducting research on the correlation between cortisol and several potential diseases. Here, we report a molecularly imprinted polymer (MIP) electrochemical biosensor that utilizes a porous composite (MXG) modified electrode. MXG composite is prepared by combining Ti3C2Tx-MXene sheets and graphene (Gr). MXG composite material with high conductive properties and large electroactive surface area promotes the charge transfer capability of the electrode surface, expands the effective surface area of the sensor, and increases the content of cortisol-imprinted cavities on the electrode, thereby improving the sensing ability of the sensor. By optimizing the preparation process, the prepared sensor has an ultralow lower limit of detection of 0.4 fM, a wide detection range of 1 fM-10 μM, and good specificity for steroid hormones and interfering substances with similar cortisol structure. The ability of the sensor to detect cortisol in saliva was also confirmed experimentally. This highly sensitive and selective cortisol sensor is expected to be widely used in the fields of physiological and psychological care.

Design of a versatile and selective electrochemical sensor based on dummy molecularly imprinted PEDOT/laser-induced graphene for nitroaromatic explosives detection

Considering the formidable explosive power and human carcinogenicity of nitroaromatic explosives, the implementation of an accurate and sensitive detection technology is imperative for ensuring public safety and monitoring post-blast environmental contamination. In the present work, a versatile and selective electrochemical sensor based on dummy molecularly imprinted poly (3,4-ethylenedioxythiophene)/laser-induced graphene (MIPEDOT/LIG) was successfully developed and the specific detection of multiple nitroaromatic explosives was realized in the single sensor. The accessible and nontoxic trimesic acid (TMA) and superior 3, 4-ethylenedioxythiophene (EDOT) were selected as the dummy-template and the functional monomer, respectively. The interaction between the functional monomer and the template, and the morphology, electrochemical properties and detection performance of the sensor were comprehensively investigated by ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry. Benefiting from the alliance of TMA and EDOT, the MIPEDOT/LIG sensor manifested outstanding selectivity and sensitivity for 2,4,6-trinitrotolueen (TNT), 2,4,6-trinitrophenol (TNP), 2,4-dinitrotoluene (DNT), 1,3,5-trinitrobenzene (TNB), 2,4-dinitrophenol (DNP), and 1,3-dinitrobenzene (DNB) (representative nitroaromatic explosives) with limits of determination of 1.95 ppb, 3.06 ppb, 2.49 ppb, 1.67 ppb, 1.94 ppb, and 4.56 ppb, respectively. The sensor also exhibited extraordinary reliability and convenience for environmental sample detection. Therefore, a perfect combination of versatility and selectivity in the MIPEDOT/LIG sensor was achieved. The findings of this work provide a new direction for the development of multi-target electrochemical sensors using a versatile dummy template for explosives detection.

Fabrication of a Molecularly-Imprinted-Polymer-Based Graphene Oxide Nanocomposite for Electrochemical Sensing of New Psychoactive Substances

As new psychoactive substances (commonly known as "the third generation drugs") have characteristics such as short-term emergence, rapid updating, and great social harmfulness, there is a large gap in the development of their detection methods. Herein, graphite oxide (GO) was first prepared and immobilized with a reversible addition-fragmentation chain transfer (RAFT) agent, then a new psychoactive substance (4-MEC) was chosen as a template, and then the surface RAFT polymerization of methacrylamide (MAAM) was carried out by using azobisisobutyronitrile (AIBN) as an initiator and divinylbenzene (DVB) as a cross-linker. After the removal of the embedded template, graphene oxide modified by molecularly imprinted polymers (GO-MIPs) was finally obtained. Owing to the specific imprinted cavities for 4-MEC, the satisfactory selectivity and stability of the GO-MIP nanocomposite have been demonstrated. The GO-MIP nanocomposite was then used to fabricate the electrochemical sensor, which displayed a high selectivity in detecting 4-MEC over a linear concentration range between 5 and 60 μg mL^-1 with a detection limit of 0.438 μg mL^-1. As a result, the GO-MIPs sensor developed an accurate, efficient, convenient, and sensitive method for public security departments to detect illicit drugs and new psychoactive substances.

Nanomaterials-Based Ion-Imprinted Electrochemical Sensors for Heavy Metal Ions Detection: A Review

Heavy metal ions (HMIs) pose a serious threat to the environment and human body because they are toxic and non-biodegradable and widely exist in environmental ecosystems. It is necessary to develop a rapid, sensitive and convenient method for HMIs detection to provide a strong guarantee for ecology and human health. Ion-imprinted electrochemical sensors (IIECSs) based on nanomaterials have been regarded as an excellent technology because of the good selectivity, the advantages of fast detection speed, low cost, and portability. Electrode surfaces modified with nanomaterials can obtain excellent nano-effects, such as size effect, macroscopic quantum tunneling effect and surface effect, which greatly improve its surface area and conductivity, so as to improve the detection sensitivity and reduce the detection limit of the sensor. Hence, the present review focused on the fundamentals and the synthetic strategies of ion-imprinted polymers (IIPs) and IIECSs for HMIs detection, as well as the applications of various nanomaterials as modifiers and sensitizers in the construction of HMIIECSs and the influence on the sensing performance of the fabricated sensors. Finally, the potential challenges and outlook on the future development of the HMIIECSs technology were also highlighted. By means of the points presented in this review, we hope to provide some help in further developing the preparation methods of high-performance HMIIECSs and expanding their potential applications.