Effective imprinting of an anticancer drug, 6-thioguanine, via mussel-inspired self-polymerization of dopamine over reduced graphene oxide.

Apart from being a vital catecholamine molecule responsible for the proper functioning of the central nervous system (CNS), hormonal and renal systems, dopamine (DA) has also been increasingly employed as a functional monomer in the fabrication of surface molecular imprinting polymers (MIPs) for valuable analytes. Herein, we demonstrate the effective imprinting of 6-thioguanine (6-TG), an anticancer drug, via mussel-inspired self-polymerization of dopamine conducted in a weakly alkaline solution over reduced graphene oxide (rGO). The polymerization of 6-TG resulted into a thin polydopamine (PDA) film of 8.4 nm thickness. Removal of 6-TG molecules from this imprinted PDA film created numerous cavities of 6-TG. The electrochemical investigation of MIP electrodes found an excellent electrocatalytic activity toward 6-TG with a significant decrease in the over-potential as compared to that of the bare glassy carbon electrode (GCE). This can be attributed to the graphene's distinct physical and chemical features such as subtle electronic characteristics, an attractive π-π interaction as well as the strong adsorptive capability of MIP films. This electrochemical sensor displayed a high selectivity owing to the specific imprinted cavities for adrenaline and worked well over a wide linear concentration range of adrenaline between 0.0015 and 50 µM with a detection limit (LOD) of 0.25 nM and good reproducibility and stability. Our system depicts excellent recoveries from 97.0% to 100.6% for two different samples of urine and thioguanine drugs. These results show the great potential of our system with multiple advantages, including convenient fabrication and optimization, high sensitivity and selectivity, high reproducibility and stability, and cost-effectiveness.

Dual-templates molecularly imprinted monolithic columns for the evaluation of serotonin and histamine in CEC.

To extend the application of molecularly imprinted polymers, the dual-templates molecularly imprinted monolithic columns were developed in a capillary format. Two templates serotonin and histamine were simultaneously imprinted using two different functional monomers such as methacrylic acid (MAA) and methylenesuccinic acid (MSA) in a mixture of ethylene glycol dimethacrylate (EDMA) as a cross-linker and AIBN as polymerization initiator dissolved in DMF as porogen. The resulting molecular imprinted polymers (MIPs) were characterized based on their performance in the CEC separation of two imprinted templates. The optimization parameters such as pH, ACN composition, and concentration of the eluent were varied to achieve best resolution and efficiency for CEC separation of templates with each MIP column. It was found that the MIP monolith column fabricated using MSA offered better resolution and separation efficiency compared to column fabricated with MAA. This work utilized the dual-templates imprinting approach successfully and broadens the scope of multi-templates imprinting capabilities in capillary format in CEC application.

Special Issue in "Nanomaterials and Their Applications in Sensing and Biosensing".

The identification of the target molecule is required for rapid and reliable clinical diagnosis and disease monitoring [...].

Crumpled MXene nanosheets for sensing of ascorbic acid in food, biological fluids, and erythrocytes in-vitro microenvironment.

In this work, a simple and facile method was developed to achieve controlled oxidation and enhance the surface area of MXene nanosheets and their utilization in the efficient sensing of ascorbic acid (AA or vitamin C). After etching of MAX phase to MXene via the MILD technique, controlled flash oxidation was carried out in the open air environment for 1.5 h, followed by flocculation of oxidized MXene nanosheets by using H2SO4, consequently achieving crumpled MXene possessing anatase phase, porosity, and improved surface area as revealed and confirmed by SEM, TEM, Raman, and BET analysis results. The as-prepared crumpled MXene was coated over a glassy carbon electrode (GCE) and used to determine AA successfully via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV) with a linear concentration range of 300 µM to 0.005 µM with a detection limit (LOD) of 2 nM (2.8 % RSD and S/N = 3). The developed electrochemical sensor was used to determine the AA in various actual samples such as juice, urine, serum, and erythrocytes spiked with AA with excellent recoveries in the 94-103 % range. The sensor also demonstrated excellent reproducibility (~1 % RSD for five repetitive assays) and a shelf life of nearly one month with a negligible decrease in response. Furthermore, it lost only 10 % of its response for the next ten days. It also showed satisfactory selectivity toward AA in the presence of other similar compounds, including uric acid (UA), dopamine (DA), and glucose.

Current trends in carbon-based quantum dots development from solid wastes and their applications.

Urbanization and a massive population boom have immensely increased the solid wastes (SWs) generation and are expected to reach 3.40 billion tons by 2050. In many developed and emerging nations, SWs are prevalent in both major and small cities. As a result, in the current context, the reusability of SWs through various applications has taken on added importance. Carbon-based quantum dots (Cb-QDs) and their many variants are synthesized from SWs in a straightforward and practical method. Cb-QDs are a new type of semiconductor that has attracted the interest of researchers due to their wide range of applications, which include everything from energy storage, chemical sensing, to drug delivery. This review is primarily focused on the conversion of SWs into useful materials, which is an essential aspect of waste management for pollution reduction. In this context, the goal of the current review is to investigate the sustainable synthesis routes of carbon quantum dots (CQDs), graphene quantum dots (GQDs), and graphene oxide quantum dots (GOQDs) from various types SWs. The applications of CQDs, GQDs, and GOQDs in the different areas are also been discussed. Finally, the challenges in implementing the existing synthesis methods and future research directions are highlighted.

Molecularly Imprinted Polymer-Based Sensors Integrated with Transition Metal Dichalcogenides (TMDs) and MXenes: A Review.

Molecularly imprinted polymer (MIP)-based electrochemical sensors have been extensively researched due to their higher sensitivity, quick response, and operational ease. To develop more advanced sensing devices with enhanced properties, MIPs have been integrated with two-dimensional (2D) layered materials such as transition metal dichalcogenides (TMDs) and MXenes. These 2D materials have unique electronic properties and an extended surface area, making them promising sensing materials that can improve the performance of MIPs. In this review article, we describe the methods used for the synthesis of TMDs and MXenes integrated MIP-based electrochemical sensors. Furthermore, we have provided a critical review of a wide range of analytes determined through the application of these electrochemical sensors. We also go over the influence of TMDs and MXenes on the binding kinetics and adsorption capacity which has enhanced binding recognition and sensing abilities. The combination of TMDs and MXenes with MIPs shows promising synergy in the development of highly efficient recognition materials. In the future, these sensors could be explored for a wider range of applications in environmental remediation, drug delivery, energy storage, and more. Finally, we address the challenges and future perspectives of using TMDs and MXenes integrated MIPs. We conclude with a focus on future development and the scope of integrating these materials in sensing technology.

La(0.7)Sr(0.3)MnO3 nanoparticles based ultra-high sensitive ammonia chemical sensor.

A facile, reliable, reproducible and ultra-high sensitive aqueous ammonia chemical sensor has been fabricated based on the utilization of La(0.7)Sr(0.3)MnO3 nanoparticles (LSMO NPs), as efficient electron mediators, and reported in this paper. The LSMO NPs were prepared by hydrothermal protocol followed by the annealing process and characterized in detail in terms of their mophological, structural and compositional properties. The I-V technique based aqueous ammonia sensor exhibits an ultra-high sensitivity of 494.68 +/- 0.01 microA cm(-2)mM(-1) and very low-detection limit of 0.2 microM with a response time less than 10 s. To the best of our knowledge, this is the first report in which LSMO is used as an efficient electron mediator for the fabrication of aqueous ammonia chemical sensor. Moreover, by comparing the literature, it is confirmed that the fabricated sensor exhibits highest sensitivity towards the detection of aqueous ammonia. This LSMO nanomaterial based research broadens the range of efficient electron mediators utilized for the fabrication of ultra-high sensitive chemical sensors.

2D Transition Metal Carbides (MXene) for Electrochemical Sensing: A Review.

MXene, a novel class of 2-dimensional transition metal carbides has evolved as a promising material for various applications owing to its outstanding characteristics such as hydrophilicity, high electrical conductivity, surface area, and attractive topological structure. MXenes can form dispersion in common solvents and constitute composite with other nanomaterials, which can be utilized as effective transducers for molecular sensing. MXene-modified support materials, thus provide an intriguing platform for immobilization of target molecules onto their surface. The literature reveals that it has been increasingly utilized in the sensing of diverse types of analytes including glucose, pharmaceuticals, metals and dyes, cancer markers, pesticides, neurotransmitters, small valuable molecules, and so on. In this review, we summarize the recent updates in the MXene modified materials for sensing. For the convenience of our audience, we have distributed the analytes into categories and discussed them comprehensively. Not only we present the synthesis approach, electrochemical properties and surface chemistry of MXenes but also discussed briefly the current challenges and an outlook for future research in the related area.

Picomolar or beyond Limit of Detection Using Molecularly Imprinted Polymer-Based Electrochemical Sensors: A Review.

Over the last decades, molecularly imprinted polymers (MIPs) have emerged as selective synthetic receptors that have a selective binding site for specific analytes/target molecules. MIPs are synthetic analogues to the natural biological antigen-antibody system. Owing to the advantages they exhibit, such as high stability, simple synthetic procedure, and cost-effectiveness, MIPs have been widely used as receptors/sensors for the detection and monitoring of a variety of analytes. Moreover, integrating electrochemical sensors with MIPs offers a promising approach and demonstrates greater potential over traditional MIPs. In this review, we have compiled the methods and techniques for the production of MIP-based electrochemical sensors along with the applications of reported MIP sensors for a variety of analytes. A comprehensive in-depth analysis of recent trends reported on picomolar (pM/10-12 M)) and beyond picomolar concentration LOD (≥pM) achieved using MIPs sensors is reported. Finally, we discuss the challenges faced and put forward future perspectives along with our conclusion.

Progress in smartphone-enabled aptasensors.

Despite their high analytical performance, conventional analytical biosensor devices are usually difficult to handle, time-consuming, bulky and expensive. As a result, their applications remain restricted to resource-limited environments. In particular, the transportation of conventional analytical equipment is challenging for the proper in-situ point of need (PON)/point of care (POC) detection of biomolecules. In this context, smartphones, the most widely utilized cutting-edge mobile gadgets, continue to be a favored option because of their ease of portability and revolutionary sensing capabilities. On the other hand, aptamers are molecular recognition units consisting of nucleic acids with highly sensitive and selective recognition capabilities towards their respective targets. The coupling of smartphones with aptamers have led the development of advanced, user-friendly, portable, and cost-effective in-situ PON/POC biosensors for the detection of biomolecules. Such sensors are well-suited for a variety of applications, including food safety, environmental monitoring, and disease diagnostics. Herein, for the first time, achievements made between 2017 and 2022 in the concept and design of the smartphone-enabled aptasensors for biosensing applications are reviewed. The review covers different fabrication strategies and the discussion of several operating systems, underlying programs, and related software. At the end, the important merits, challenges, and future prospects of smart phone-driven aptasensors are presented. This report intends to assist scientists and engineers in comprehending the fabrication of smartphone-based aptasensors and their underlying sensing principles, as well as stimulating the future developments in the direction of affordable, portable, simple, and readily available sensing devices.

Analysis of phospholipids using an open-tubular capillary column with a monolithic layer of molecularly imprinted polymer in capillary electrochromatography-electrospray ionization-tandem mass spectrometry.

In this study, an open-tubular capillary electrochromatography (OT-CEC) column with a monolithic layer of molecularly imprinted polymer (MIP) based on methacrylic acid, ethylene glycol dimethacrylate, and 4-styrenesulfonic acid was utilized for the simultaneous separation and characterization of phospholipid (PL) molecular structures by interfacing with electrospray ionization-tandem mass spectrometry (ESI-MS-MS). Introducing an MIP-based monolith along with charged species at the OT column made it possible to separate PL molecules based on differences in head groups and acyl chain lengths in CEC. For the interface of OT-CEC with ESI-MS-MS, a simple nanospray interface utilizing a sheath flow was developed and the resulting OT-CEC-ESI-MS-MS was able to separate PL standards (phosphatidylserines, phosphatidylethanolamines, phosphatidylglycerols, phosphatidic acid, and lysophosphatidylglycerols). The developed method was applied to human urinary lipid extracts, and resulted in the separation and structural identification of 18 molecules by data-dependent collision-induced dissociation.

An Overview of Bio-Inspired Intelligent Imprinted Polymers for Virus Determination.

The molecular imprinting polymers (MIPs) have shown their potential in various applications including pharmaceuticals, chemical sensing and biosensing, medical diagnosis, and environmental related issues, owing to their artificial selective biomimetic recognition ability. Despite the challenges posed in the imprinting and recognition of biomacromolecules, the use of MIP for the imprinting of large biomolecular oragnism such as viruses is of huge interest because of the necessity of early diagnosis of virus-induced diseases for clinical and point-of-care (POC) purposes. Thus, many fascinating works have been documented in which such synthetic systems undoubtedly explore a variety of potential implementations, from virus elimination, purification, and diagnosis to virus and bacteria-borne disease therapy. This study is focused comprehensively on the fabrication strategies and their usage in many virus-imprinted works that have appeared in the literature. The drawbacks, challenges, and perspectives are also highlighted.

Bacterial Imprinting Methods and Their Applications: An Overview.

Microbial contaminations and infections are hazardous and pose crucial concerns for humans. They result in severe morbidity and mortality around the globe. Even though dish-culturing, polymerase chain reaction (PCR), an enzyme-linked immunosorbent assay (ELISA) exhibits accurate and reliable detection of bacteria but these methods are time-consuming, laborious, and expensive. This warrants early detection and quantification of bacteria for timely diagnosis and treatment. Bacteria imprinting ensures a solution for selective and early detection of bacteria by snagging them inside their imprinted cavities. This review provides an insight into MIPs based bacterial detection strategies, challenges, and future perspectives.

Preparation of open tubular molecule imprinted polymer capillary columns with various templates by a generalized procedure and their chiral and non-chiral separation performance in CEC.

A generalized preparation procedure of open tubular (OT) molecule imprinted polymer (MIP) columns is proposed for a number of templates with acidic functionality such as profen drugs and others. The template (S-enantiomer) was mixed with methacrylic acid, ethylene glycol dimethacrylate and 4-styrenesulfonic acid, dissolved in a porogen mixture of ACN/2-propanol (9/1), and incubated in a pretreated and silanized fused silica capillary by the thermal non-covalent polymerization procedure. The whole preparation procedure was exactly the same for all the MIP capillaries except for the selection of template. Nevertheless, the morphologies of the MIP layers were markedly variant depending upon the choice of template. The separation efficiency of each OT-MIP column for chiral separation of R- and S-enantiomers was examined and tuned to obtain the best separation efficiency by changing the chromatographic parameters such as eluent composition and pH. Different optimized conditions were obtained for different OT-MIP columns. Nevertheless, a unified eluent could be used to obtain still quite satisfactory results. Non-chiral separation of the MIP columns were also examined in the unified eluent with two sets of test mixtures, that is, a mixture of alkylbenzenes and a mixture of small polar solutes. The chiral and non-chiral separation of this study resulted in very good separation efficiencies. This work is the very first study for the generalization of preparation of OT-MIP columns for a number of templates.

Use of chain transfer agent attached to silica particles in preparation of polystyrene-based stationary phases.

A new stationary phase has been prepared by attaching a new chain transfer agent on silica particles followed by reversible addition-fragmentation chain transfer polymerization. Porous silica particles were reacted with 3-chloropropyltrimethoxysilane followed by sodium diethyl dithiocarbarmate. The silica particles were then allowed to undergo radical polymerization with styrene. The phase had improved ligand morphology to show better separation performance than that of the conventional C18 phase.

Progress in cancer biomarkers monitoring strategies using graphene modified support materials.

Cancer is the one of the fatal and dreaded disease responsible for huge number of morbidity and mortality across the globe. It is expected that the global burden will increase to 21.7 million fresh cancer cases as compared to present estimate of 18.1 million cancer cases in addition to nearly 9.6 million cancer deaths worldwide. In response to cancerous or certain benign conditions; specific type of tumor or cancer markers (biomarkers) are produced at much higher levels which are secreted into the urine, blood, stool, tumor or other tissues. Therefore, the efficient and early detection of cancer biomarkers is necessary which can offer a reliable way for cancer patient screening and diagnosis. This process not only helps in the evaluation of pathogenic processes but also the prognosis of different cancers and pharmacological responses to therapeutic interventions are secured. Over the past several years, electrochemical detection methods have proved to be the most attractive methods among many, due to the advantages, such as simple instrumentation, portability, low cost and high sensitivity. Furthermore, the modifications of these electrochemical immunosensors by utilizing various types of nanomaterials enable these systems to detect trace amount of target tumor markers. Hence, herein, we intend to review the selective works on electrochemical detection of various biomarkers using wide range of nanomaterials with a particular focus on graphene.

Long open tubular molecule imprinted polymer capillary columns with excellent separation efficiencies in chiral and non-chiral separation by capillary electrochromatography.

Long open tubular S-ketoprofen molecule imprinted polymer capillary columns (1, 2, and 3 m) with the number of theoretical plates (N) over a million for both chrial and non-chiral CEC separation have been prepared. Chiral separation of racemic ketoprofen and non-chiral separation of other profen drugs have been achieved with excellent efficiency and good selectivity after optimization of the chromatographic conditions. The N value per column was not proportional to the effective column length although it was increased with the column length. This study has shown the outstanding prospect of the strategy to form a porous and rugged open tubular layer in a moderately long (1 m) capillary column in molecule imprinted polymer-CEC studies.

Open tubular layer of S-ofloxacin imprinted polymer fabricated in silica capillary for chiral CEC separation.

An open tubular molecule imprinted polymer (OT-MIP) capillary column has been prepared for chiral separation of ofloxacin enantiomers in CEC. The S-ofloxacin imprinted OT column was fabricated by thermally initiated non-covalent polymerization procedure inside a pretreated and silanized fused silica capillary. The template molecule was incorporated with methacrylic acid (MAA), ethylene glycol dimethacrylate (EDMA) and 4-styrenesulfonic acid (4-SSA) and dissolved in a porogen mixture of ACN/2-propanol (9:1). The separation efficiency of the 4-SSA MIP column was found quite better than that of the MIP column without 4-SSA. It has been demonstrated that our OT-MIP column can separate ofloxacin enantiomers with excellent chiral separation efficiency after tuning the various chromatographic conditions. The optimized chromatographic eluent was 85:15, v/v%, ACN/60 mM sodium acetate at pH 7. The separation efficiency and selectivity of chiral separation of this study were far better than those obtained by previous methods for chiral separation of R- and S-ofloxacin.

Molecular Imprinting Prevents Environmental Contamination and Body Toxicity from Anticancer Drugs: An Update.

Cancer has been responsible for high morbidity and mortality globally. The treatment of cancer is possible using different kinds of therapies using anticancer drugs if it is diagnosed at the right time. Nevertheless, their appropriate administration for maximum therapeutic effect and their elimination from the patient's body causing environmental problems are two big issues which could be successfully abated using molecular imprinted polymers (MIPs) owing to their unique features. In this review, we have compiled and discussed the works on the determination and controlled release of anticancer drugs based on MIPs. We also highlighted the current challenges and remedies, and the future direction of MIPs in this area.

Facile preparation of molybdenum carbide (Mo2C) nanoparticles and its effective utilization in electrochemical sensing of folic acid via imprinting.

Herein, we propose a facile chemical reduction method to synthesize the molybdenum carbide (Mo2C) nanoparticles and its application for the electrochemical detection of folic acid (FA) through imprinting technique. Raman scattering, photoelectron spectroscopy and electron microscopy techniques were employed to study the properties of Mo2C nanoparticles. FA imprinting was carried out in the presence of pyrrole monomer over Mo2C modified glassy carbon electrode (GCE). The proposed sensor showed the detection behavior for wide range of FA concentrations from 0.01 µM to 120 µM with an excellent LOD value of 4 nM and good selectivity toward FA as compared to other co-existing species in real samples. The fabricated MIP-Mo2C/GCE sensors were able to be replicated with ∼1.9% RSD, and their reproduced sensor offered good repeatability (RSD; 1.6%) and stability.