Transitioning from Supramolecular Chemistry to Molecularly Imprinted Polymers in Chemical Sensing.

This perspective article focuses on the overwhelming significance of molecular recognition in biological processes and its emulation in synthetic molecules and polymers for chemical sensing. The historical journey, from early investigations into enzyme catalysis and antibody-antigen interactions to Nobel Prize-winning breakthroughs in supramolecular chemistry, emphasizes the development of tailored molecular recognition materials. The discovery of supramolecular chemistry and molecular imprinting, as a versatile method for mimicking biological recognition, is discussed. The ability of supramolecular structures to develop selective host-guest interactions and the flexible design of molecularly imprinted polymers (MIPs) are highlighted, discussing their applications in chemical sensing. MIPs, mimicking the selectivity of natural receptors, offer advantages like rapid synthesis and cost-effectiveness. Finally, addressing major challenges in the field, this article summarizes the advancement of molecular recognition-based systems for chemical sensing and their transformative potential.

Aerosol-assisted nanostructuring of nickel/cobalt oxide thin films for viable electrochemical hydrazine sensing.

Herein, we report the fabrication of NiO-CoO films for the electrochemical detection of hydrazine. An electrochemical sensor was devised where aerosol assisted chemical vapor deposition (AACVD) was employed as a nifty method for synthesizing NiO-CoO films over FTO electrodes. NiO-CoO-nanoparticle (NP) and NiO-CoO-nanowall (NW) films were fabricated over FTO substrates. The electrocatalytic analysis was performed in a standard three-electrode electrochemical setup. NiO-CoO-NW/FTO showed enhanced electro-oxidation for hydrazine at all concentrations tested. XRD, XPS, EDX, and FE-SEM techniques were used to characterize the structural, morphological, and elemental properties of NiO-CoO films. The results showed improved sensitivity, a large dynamic range, and good long-term stability of NiO-CoO-NW films. The amperometric response was used to measure the detection limit, and it was as low as 0.01 µM, and the sensitivity is ∼33 µA µM-1 cm-2. Besides, the NiO-CoO-NW/FTO electrodes showed significant selectivity towards hydrazine upon testing cross-sensitivity to other common interfering molecules. This strategy of using NiO-CoO-NW/FTO electrodes prepared via AACVD has great potential for the direct determination of hydrazine in environmental sensing applications.

An Overview of High Frequency Acoustic Sensors-QCMs, SAWs and FBARs-Chemical and Biochemical Applications.

Acoustic devices have found wide applications in chemical and biosensing fields owing to their high sensitivity, ruggedness, miniaturized design and integration ability with on-field electronic systems. One of the potential advantages of using these devices are their label-free detection mechanism since mass is the fundamental property of any target analyte which is monitored by these devices. Herein, we provide a concise overview of high frequency acoustic transducers such as quartz crystal microbalance (QCM), surface acoustic wave (SAW) and film bulk acoustic resonators (FBARs) to compare their working principles, resonance frequencies, selection of piezoelectric materials for their fabrication, temperature-frequency dependency and operation in the liquid phase. The selected sensor applications of these high frequency acoustic transducers are discussed primarily focusing on the two main sensing domains, i.e., biosensing for working in liquids and gas/vapor phase sensing. Furthermore, the sensor performance of high frequency acoustic transducers in selected cases is compared with well-established analytical tools such as liquid chromatography mass spectrometry (LC-MS), gas chromatographic (GC) analysis and enzyme-linked immunosorbent assay (ELISA) methods. Finally, a general comparison of these acoustic devices is conducted to discuss their strengths, limitations, and commercial adaptability thus, to select the most suitable transducer for a particular chemical/biochemical sensing domain.

Manifestation of hydatid cyst of liver with pancreatitis, cholangitis and jaundice: A case report.

Hydatid disease or echinococcosis, a systemic zoonosis is caused by Echinococcusgranulosus larvae. This is a common disease found all over the world, especially in the Mediterranean region. We report a 40 year old male with no known comorbids who came with complaints of fever with rigors and chills, right hypochondriac pain, and yellow discolouration of the sclera. A CT scan abdomen with endoscopic retrograde cholangiopancreatography (ERCP) gave a diagnosis of hydatid cyst of the liver with pancreatitis, cholangitis and jaundice due to involvement of the biliary tree and common bile duct ERCP was done and a stent was placed after which the patient was referred to general surgery department where the resection of cyst was performed under general anaesthesia. Pancreatitis was managed conservatively. We could not find any case reported in the literature, which showed manifestation of hydatid cyst of liver with pancreatitis, cholangitis and jaundice simultaneously, which made us report this case.

Developing imprinted polymer nanoparticles for the selective separation of antidiabetic drugs.

In this study, new molecularly imprinted polymer (MIP) nanoparticles are designed for selective recognition of different drugs used for the treatment of type 2 diabetes mellitus, i.e. sitagliptin (SG) and metformin (MF). The SG- and MF-imprinted polymer nanoparticles are synthesized by free-radical initiated polymerization of the functional monomers: methacrylic acid and methyl methacrylate; and the crosslinker: ethylene glycol dimethacrylate. The surface morphology of resultant MIP nanoparticles is studied by atomic force microscopy. Fourier transform infrared spectra of MIP nanoparticles suggest the presence of reversible, non-covalent interactions between the template and the polymer. The effect of pH on the rebinding of antidiabetic drugs with SG- and MF-imprinted polymers is investigated to determine the optimal experimental conditions. The molecular recognition characteristics of SG- and MF-imprinted polymers for the respective drug targets are determined at low concentrations of SG (50-150 ppm) and MF (5-100 ppm). In both cases, the MIP nanoparticles exhibit higher binding response compared to non-imprinted polymers. Furthermore, the MIPs demonstrate high selectivity with four fold higher responses toward imprinted drugs targets, respectively. Recycled MIP nanoparticles retain 90% of their drug-binding efficiency, which makes them suitable for successive analyses with significantly preserved recognition features.

Preparation, characterization, and enhanced thermal and mechanical properties of epoxy-titania composites.

This paper presents the synthesis and thermal and mechanical properties of epoxy-titania composites. First, submicron titania particles are prepared via surfactant-free sol-gel method using TiCl4 as precursor. These particles are subsequently used as inorganic fillers (or reinforcement) for thermally cured epoxy polymers. Epoxy-titania composites are prepared via mechanical mixing of titania particles with liquid epoxy resin and subsequently curing the mixture with an aliphatic diamine. The amount of titania particles integrated into epoxy matrix is varied between 2.5 and 10.0 wt.% to investigate the effect of sub-micron titania particles on thermal and mechanical properties of epoxy-titania composites. These composites are characterized by X-ray photoelectron (XPS) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric (TG), and mechanical analyses. It is found that sub-micron titania particles significantly enhance the glass transition temperature (>6.7%), thermal oxidative stability (>12.0%), tensile strength (>21.8%), and Young's modulus (>16.8%) of epoxy polymers. Epoxy-titania composites with 5.0 wt.% sub-micron titania particles perform best at elevated temperatures as well as under high stress.

Discerning biomimetic nanozyme electrodes based on g-C3N4 nanosheets and molecularly imprinted polythiophene nanofibers for detecting creatinine in microliter droplets of human saliva.

The growing risk of death associated with kidney dysfunction underlines the requirement for a cost-effective and precise point-of-care (POC) diagnostic tool to identify chronic kidney disease (CKD) at an early stage. This work reports the development of a non-invasive POC diagnostic based on cost-efficient, disposable electrodes and in situ-designed biomimetic nanozymes. The nanozymes are composed of graphitic carbon nitride nanosheets (gCN) and creatinine-imprinted polythiophene nanofibers (miPTh). Microscopic analyses reveal porous nanofibrous surface morphology of biomimetic miPTh/gCN nanozymes. Bulk imprinting and the inclusion of conductive gCN nanosheets drastically reduced the charge transfer resistance and improved the electron exchange kinetics at the nanozyme-electrolyte interface. The electrochemical oxidation of creatinine is studied via cyclic voltammetry (CV), and differential pulse voltammetry (DPV), which exhibit excellent creatinine recognition ability of biomimetic miPTh/gCN nanozyme sensors compared to pristine polymeric or non-imprinted nanozymes. The sensor reveals linear response toward 200-1000 nmol L-1 creatinine, high sensitivity (4.27 µA cm-2 nmol-1 L), sub-nanomolar detection limit (340 pmol L-1), and excellent selectivity over common salivary analytes. To corroborate its real-world utility, the miPTh/gCN nanozyme sensor shows an impressive 94.8% recovery of spiked creatinine concentrations in microliter droplets of human saliva samples. This disposable sensor reveals great potential in the realm of reliable and efficient non-invasive POC diagnostics for healthcare delivery.

Electrocatalytic FeFe2O4 embedded, spermine-imprinted polypyrrole (Fe/MIPpy) nanozymes for cancer diagnosis and prognosis.

Developing synthetic materials, with enzyme-like molecular recognition capabilities, as functional receptors in electronic or electrochemical devices for the timely diagnosis of major diseases is a great challenge. Herein, we present the development of Fe/MIPpy nanozymes, characterized as enzyme-like artificial receptors, for the precise and non-invasive monitoring of cancer biomarkers in aqueous solutions and human saliva. Through the integration of PVA-stabilized FeFe2O4 nanocrystals in a molecularly imprinted conducting polypyrrole matrix, the Fe/MIPpy nanozymes demonstrate 424 nA cm-2 nM-1 sensitivity and 220 pM detection limit. Charge-transfer mechanisms, Fe/MIPpy-spermine interactions, and the principle of spermine recognition are investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The disposable Fe/MIPpy sensor operates wirelessly and offers rapid and remote quantification of spermine, making it a promising material for the development of cost-effective tools for non-invasive cancer diagnosis and prognosis.

Portable smartphone-enabled dydrogesterone sensors based on biomimetic polymers for personalized gynecological care.

Dydrogesterone, a frequently prescribed synthetic hormone integral to the treatment of diverse gynecological conditions, necessitates precise quantification in complex human plasma. In this study, the development of a portable, smartphone-based electrochemical sensor employing screen-printed gold electrodes (SPAuEs) modified with a biomimetic, molecularly imprinted poly(methacrylic acid-co-methyl methacrylate) (MIP) is presented for dydrogesterone detection in human plasma. FTIR spectroscopy illustrates the transformation of a pre-polymer mixture into a polymerized matrix, while SEM reveals a uniform MIP/SPAuE surface morphology. The sensor fabrication protocol, encompassing MIP/SPAuE composition, polymerization solvent, incubation time, and scan rate, is optimized to achieve enhanced sensitivity. The MIP/SPAuEs sensor exhibits a linear sensor response to dydrogesterone within the concentration range of 1-500 nM, as evidenced by cyclic and differential pulse voltammetry. The MIP/SPAuE sensor demonstrates exceptional sensitivity, recording 8.2 × 10-3 µA nM-1, with a sub-nanomolar limit of detection (LOD = 370 pM), and low limit of quantification (LOQ = 1.12 nM), along with appreciable selectivity over common interferents. In real-world clinical applications, the designed sensor is effectively employed for the rapid and precise determination of dydrogesterone in human blood plasma, achieving a remarkable recovery of 81%. Furthermore, MIP/SPAuE coatings possess suitable stability over 15 days, indicating the robustness of the sensor material for multiple rounds of analysis. The developed sensor provides a sensitive, selective, and cost-effective solution for monitoring dydrogesterone in plasma during various gynecological disorders, allowing for personalized healthcare applications.

Correction: Portable smartphone-enabled dydrogesterone sensors based on biomimetic polymers for personalized gynecological care.

Correction for 'Portable smartphone-enabled dydrogesterone sensors based on biomimetic polymers for personalized gynecological care' by Sobia Ashraf et al., J. Mater. Chem. B, 2024, https://doi.org/10.1039/D4TB00657G.

Core-shell niobium(v) oxide@molecularly imprinted polythiophene nanoreceptors for transformative, real-time creatinine analysis.

Creatinine, a byproduct of muscle metabolism, is typically filtered by the kidneys. Deviations from normal concentrations of creatinine in human saliva serve as a crucial biomarker for renal diseases. Monitoring these levels becomes particularly essential for individuals undergoing dialysis and those with kidney conditions. This study introduces an innovative disposable point-of-care (PoC) sensor device designed for the prompt detection and continuous monitoring of trace amounts of creatinine. The sensor employs a unique design, featuring a creatinine-imprinted polythiophene matrix combined with niobium oxide nanoparticles. These components are coated onto a screen-printed working electrode. Thorough assessments of creatinine concentrations, spanning from 0 to 1000 nM in a redox solution at pH 7.4 and room temperature, are conducted using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). The devised sensor exhibits a sensitivity of 4.614 µA cm-2 nM-1, an impressive trace level limit of detection at 34 pM, and remarkable selectivity for creatinine compared to other analytes found in human saliva, such as glucose, glutamine, urea, tyrosine, etc. Real saliva samples subjected to the sensor reveal a 100% recovery rate. This sensor, characterized by its high sensitivity, cost-effectiveness, selectivity, and reproducibility, holds significant promise for real-time applications in monitoring creatinine levels in individuals with kidney and muscle-related illnesses.

Electrochemical Creatinine (Bio)Sensors for Point-of-Care Diagnosis of Renal Malfunction and Chronic Kidney Disorders.

In the post-pandemic era, point-of-care (POC) diagnosis of diseases is an important research frontier. Modern portable electrochemical (bio)sensors enable the design of POC diagnostics for the identification of diseases and regular healthcare monitoring. Herein, we present a critical review of the electrochemical creatinine (bio)sensors. These sensors either make use of biological receptors such as enzymes or employ synthetic responsive materials, which provide a sensitive interface for creatinine-specific interactions. The characteristics of different receptors and electrochemical devices are discussed, along with their limitations. The major challenges in the development of affordable and deliverable creatinine diagnostics and the drawbacks of enzymatic and enzymeless electrochemical biosensors are elaborated, especially considering their analytical performance parameters. These revolutionary devices have potential biomedical applications ranging from early POC diagnosis of chronic kidney disease (CKD) and other kidney-related illnesses to routine monitoring of creatinine in elderly and at-risk humans.

Dual and tetraelectrode QCMs using imprinted polymers as receptors for ions and neutral analytes.

Polymers as coating materials were combined with quartz crystal microbalances (QCMs) to design sensor devices for the detection of both ionic and neutral analytes in liquid phase. The design and geometry of dual and tetraelectrode QCMs have been optimized to reduce electric field interferences. An unusual Sauerbrey effect was observed while exposing potassium salt solution to 10- and 20-MHz QCMs, i.e. increase in the frequency shifts by a factor of seven, which is attributed to electro-acoustic phenomena. Non-functionalized sol-gel materials were synthesized by templating with hydrophobic salt such as tetraethyl ammonium picrate. Imprinting with these ions of low charge density leads to sensitive layers, and UV-Vis spectroscopy was used to check re-inclusion of this analyte. In the next strategy, functionalized polyurethane for potassium ions and sol-gel materials with aminopropyl group as ligand were generated to tune selectivity and sensitivity towards Ni(2+) and Cu(2+). Methacrylic acid polymers were optimized for the detection of atrazine by hydrogen bonding; double molecular imprinted polyurethane approach was followed for pyrene recognition. Finally, these imprinted polymers were combined with tetraelectrode QCM to develop sensor platform.

Molybdenum impregnated g-C3N4 nanotubes as potentially active photocatalyst for renewable energy applications.

Molybdenum (Mo) impregnated g-C3N4 (Mo-CN) nanotubes are fabricated via a thermal/hydrothermal process to augment photoelectrochemical properties during solar-driven water-splitting (SDWS) reactions. Graphitic-C3N4 is an attractive material for photocatalysis because of its suitable band energy, high thermal and chemical stability. The FE-SEM and HR-TEM comprehend the nanotube-like morphology of Mo-CN. The spectroscopic characterization revealed bandgap energy of 2.63 eV with high visible-light activity. The x-ray diffraction of pristine g-C3N4 and Mo-CN nanotubes discloses the formation of triazine-based nanocrystalline g-C3N4, which remains stable during hydrothermal impregnation of Mo. Furthermore, Mo-CN nanotubes possess high sp2-hybridized nitrogen content, and metallic/oxidized Mo nanoparticles (in a ratio of 1:2) are impregnated into g-C3N4. The XPS analysis confirms C, N, and Mo for known atomic and oxidation states in Mo-CN. Furthermore, high photocurrent efficiency (~ 5.5 mA/cm2) is observed from 5%-Mo-CN nanotubes. That displays efficient SDWS by 5%-Mo-CN nanotubes than other counterparts. Impedance spectroscopy illustrated the lowest charge transfer resistance (Rct) of 5%-Mo-CN nanotubes, which further confirms the fast electron transfer kinetics and efficient charge separation resulting in high photocurrent generation. Hence, 5%Mo-CN composite nanotubes can serve as a potential photocatalytic material for viable solar-driven water splitting.

Rapid antibody diagnostics for SARS-CoV-2 adaptive immune response.

The emergence of a pandemic scale respiratory illness (COVID-19: coronavirus disease 2019) and the lack of the world's readiness to prevent its spread resulted in an unprecedented rise of biomedical diagnostic industries, as they took lead to provide efficient diagnostic solutions for COVID-19. However, these circumstances also led to numerous emergency use authorizations without appropriate evaluation that compromised standards, which could result in a larger than usual number of false-positive or false-negative results, leading to unwanted ambiguity in already confusing realities of the pandemic-hit closures of the world economy. This review is aimed at comparing the claimed or reported clinical sensitivity and clinical specificity of commercially available rapid antibody diagnostics with independently evaluated clinical performance results of the tests. Thereby, we not only present the types of modern antibody diagnostics and their working principles but summarize their experimental evaluations and observed clinical efficiencies to highlight the research, development, and commercialization issues with future challenges. Still, it must be emphasized that the serological or antibody tests do not serve the purpose of early diagnosis but are more suitable for epidemiology and screening populaces with an active immune response, recognizing convalescent plasma donors, and determining vaccine efficacy.

Molecular diagnostic technologies for COVID-19: Limitations and challenges.

BACKGROUND: To curb the spread of the COVID-19 (coronavirus disease 2019) pandemic, the world needs diagnostic systems capable of rapid detection and quantification of the novel coronavirus (SARS-CoV-2). Many biomedical companies are rising to the challenge and developing COVID-19 diagnostics. In the last few months, some of these diagnostics have become commercially available for healthcare workers and clinical laboratories. However, the diagnostic technologies have specific limitations and reported several false-positive and false-negative cases, especially during the early stages of infection. AIM: This article aims to review recent developments in the field of COVID-19 diagnostics based on molecular technologies and analyze their clinical performance data. KEY CONCEPTS: The literature survey and performance-based analysis of the commercial and pre-commercial molecular diagnostics address several questions and issues related to the limitations of current technologies and highlight future research and development challenges to enable timely, rapid, low-cost, and accurate diagnosis of emerging infectious diseases.

High permittivity, breakdown strength, and energy storage density of polythiophene-encapsulated BaTiO3 nanoparticles.

High permittivity and breakdown strength are desired to improve the energy storage density of dielectric materials based on reinforced polymer composites. This article presents the synthesis of polythiophene-encapsulated BaTiO3 (BTO-PTh) nanoparticles via an in situ Cu(II)-catalyzed chemical oxidative polymerization of thiophene monomer on hydrothermally obtained tetragonal BTO nanocrystals. The formed core-shell-type BTO-PTh nanoparticles exhibit excellent dielectric properties with high permittivity (25.2) and low loss (0.04) at high frequency (106 Hz). A thick PTh encapsulation layer on the surface of the BTO nanoparticles improves their breakdown strength from 47 to 144 kV/mm and the energy storage density from 0.32 to 2.48 J/cm3. A 7.75-fold increase in the energy storage density of the BTO-PTh nanoparticles is attributed to simultaneously high permittivity and breakdown strength, which are excellent for potential energy storage applications.

Enhanced High-Temperature (600 °C) NO2 Response of ZnFe2O4 Nanoparticle-Based Exhaust Gas Sensors.

Fabrication of gas sensors to monitor toxic exhaust gases at high working temperatures is a challenging task due to the low sensitivity and narrow long-term stability of the devices under harsh conditions. Herein, the fabrication of a chemiresistor-type gas sensor is reported for the detection of NO2 gas at 600 °C. The sensing element consists of ZnFe2O4 nanoparticles prepared via a high-energy ball milling and annealed at different temperatures (600-1000 °C). The effects of annealing temperature on the crystal structure, morphology, and gas sensing properties of ZnFe2O4 nanoparticles are studied. A mixed spinel structure of ZnFe2O4 nanoparticles with a lattice parameter of 8.445 Å is revealed by X-ray diffraction analysis. The crystallite size and X-ray density of ZnFe2O4 nanoparticles increase with the annealing temperature, whereas the lattice parameter and volume are considerably reduced indicating lattice distortion and defects such as oxygen vacancies. ZnFe2O4 nanoparticles annealed at 1000 °C exhibit the highest sensitivity (0.13% ppm-1), sharp response (τres = 195 s), recovery (τrec = 17 s), and linear response to 100-400 ppm NO2 gas. The annealing temperature and oxygen vacancies play a major role in determining the sensitivity of devices. The plausible sensing mechanism is discussed. ZnFe2O4 nanoparticles show great potential for high-temperature exhaust gas sensing applications.

Molecularly imprinted polymeric coatings for sensitive and selective gravimetric detection of artemether.

Monitoring antimalarial drugs is necessary for clinical assays, human health, and routine quality control practices in pharmaceutical industries. Herein, we present the development of sensor coatings based on molecularly imprinted polymers (MIPs) combined with quartz crystal microbalance (QCM) for sensitive and selective gravimetric detection of an antimalarial drug: artemether. The MIP coatings are synthesized by using artemether as the template in a poly(methacrylic acid-co-ethylene glycol dimethacrylate) matrix. Artemether-MIP and the non-imprinted polymer (NIP) control or reference layers are deposited on 10 MHz dual-electrode QCM by spin coating (187 ± 9 nm layer thickness after optimization). The coatings are characterized by FTIR spectroscopy and atomic force microscopy that reveal marked differences among the MIP and NIP. The MIP-QCM sensor exhibits high sensitivity (0.51 Hz ppm-1) with sub-10 ppm detection and quantification limits. The MIP-QCM sensor also exhibits a 6-fold higher sensitivity compared to the NIP-QCM, and a dynamic working range of 30-100 ppm. The response time of MIP-QCM devices for a single cycle of analyte adsorption, signal saturation, and MIP regeneration is less than 2.5 min. The sensor also demonstrates selectivity factors of artemether-MIP of 2.2 and 4.1 compared to artemisinin and lumefantrine, respectively. Reversibility tests reveal less than 5% variation in sensor responses over three cycles of measurements at each tested concentration. The MIP-QCM showed lower detection limits than conventional HPLC-UV, and faster response time compared to HPLC-UV and liquid chromatography-mass spectrometry (LC-MS).

Polymers imprinted with PAH mixtures--comparing fluorescence and QCM sensors.

Molecular imprinting with binary mixtures of different polycyclic aromatic hydrocarbons (PAH) is a tool for design of chemically highly sensitive layers for detection of these analytes. Sensor responses increase by one order of magnitude compared with layers imprinted with one type of template. Detection limits, e.g. for pyrene, reach down to 30 ng L(-1) in water, as could be observed with a naphthalene and pyrene-imprinted polyurethane. Comparing sensor characteristics obtained by QCM and fluorescence reveals different saturation behaviours indicating that, first, single PAH molecules occupy the interaction centres followed by gradual excimer incorporation at higher concentrations finally leading to substantial quenching, when all accessible cavities are occupied. The plateau in the mass-sensitive measurements suggests that up to 80% of the cavities generated in the MIP are re-occupied. Displacement measurements between chrysene and pyrene revealed that for imprinted layers with very high pyrene sensitivities the signals of both PAH are additive, whereas in materials with lower pyrene uptake the two analytes replace each other in the interaction sites of the polymer.