Imprinted polymer-modified hanging mercury drop electrode for differential pulse cathodic stripping voltammetric analysis of creatine

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.

Electrochemical Determination of Dopamine and Uric Acid Using Poly(proline) Modified Carbon Paste Electrode: A Cyclic Voltammetric Study

A cyclic voltammetric technique was used for electropolymerisation of proline on the surface of carbon paste electrode and for individual and concurrent determination of dopamine (DA) and uric acid (UA). The surface morphology of the developed electrode was studied by using field emission scanning electron microscopy. The modified electrode showed a high current response towards DA as compared to the bare electrode. The developed modified electrode shows good catalytic activity with a different oxidation potential of DA and UA. The electrode process was found to be adsorption controlled. The developed method shows very good stability and reproducibility. Under the optimized conditions, the concentration range is (1‒2)∙10-4 M and the observed detection limit was 4.7∙10-6 M. The developed sensor was applied for the determination of DA in the real sample with a good recovery.

Simultaneous quantification of Cd(II) and Pb(II) in surface marine sediments using Ag-Hg and Ag-Bi nanoalloys glassy carbon modified electrodes

The evaluation of glassy carbon (GC) electrodes modified with a Nafion (Nf) film and doped with nanoalloys (Nys) deposits of Ag-Hg and Ag-Bi and their application to determination of Cd (II) and Pb(II) in marine sediments, is described. Deposited Ag-Hg and AgBi Nys have a size of approximately ~80 nm dispersed and embedded inside the booths of the Nf net, while other of them remained on Nf net surface. For the AgBiNysNf-GC electrode, a detection limit (DL), 3 s criterion, slightly higher than for the AgHgNysNf-GC modified electrode was obtained. Accuracy of measurements was asserted by comparison with quantification of Cd and Pb in three sets of marine sediments samples previously analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES). The values of the standard deviation and the coefficients of variation are very low, and also comparable between the different determinations.

Synergetic Sensing Effect of Sodium Carboxymethyl Cellulose and Bismuth on Cadmium Detection by Differential Pulse Anodic Stripping Voltammetry

In the present work, a novel electrochemical sensor was developed for the detection of trace cadmium with high sensitivity and selectivity in an easy and eco-friendly way. Firstly, a glassy carbon electrode (GCE) was modified with nontoxic sodium carboxymethyl cellulose (CMC) by a simple drop-casting method, which was applied to detect cadmium by differential pulse anodic stripping voltammetry (DPASV) in a solution containing both target cadmium and eco-friendly bismuth ions, based on a quick electro-codeposition of these two metal ions on the surface of the modified electrode (CMC-GCE). Investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FT-IR), both CMC (with good film-forming ability) and bismuth (with well-defined stripping signal) were found to be well complexed with target cadmium, leading to vital signal amplification for cadmium detection at a sub-nanomolar level. Under the optimal conditions, the proposed sensor exhibited a good linear stripping signal response to cadmium (Ⅱ) ion, in a concentration range of 0.001 μmol/L–1 μmol/L with a limit of detection of 0.75 nmol/L (S/N = 3). Meanwhile, the results demonstrate that this novel electrochemical sensor has excellent sensitivity and reproducibility, which can be used as a promising detection technique for testing natural samples such as tap water.

Ultrasensitive and label-free detection of creatine based on CdO nanoparticles: a real sample approach

Low-dimensional cadmium oxide nanoparticles (CdO NPs) were prepared by a facile wet-chemical method, which later electrochemically investigated for the determination of selective creatine and measured the analytical sensor parameters such as sensitivity, limit of detection (LOD), linear dynamic range (LDR), long-term stability, and real-sample validation.

Mesosponge Optical Sinks for Multifunctional Mercury Ion Assessment and Recovery from Water Sources

Using the newly developed organic-inorganic colorant membrane is an attractive approach for the optical detection, selective screening and removal, and waste management recovery of highly toxic elements, such as Hg(II) ions, from water sources. In the systematic mesosponge optical sinks (MOSs), anchoring organic colorants into 3D, well-defined cage cavities and interconnected tubular pores (10 nm) in the long microscale channels of membrane scaffolds enhances the requirements and intrinsic properties of the hierarchal membrane. This scalable design is the first to allow control of the multifunctional processes of a membrane in a one-step screening procedure, such as the detection/recognition, removal, and filtration of ultratrace Hg(II) ions, even from actual water sources (i.e., tap, underground). The selective recovery, detection, and extraction processes of Hg(II) ions in a heterogeneous mixture with inorganic cations and anions as well as organic molecules and surfactants are mainly dependent on the structure of the colorant agent, the pH conditions, competitive ion-system compositions and concentrations, and Hg-to-colorant binding events. Our result shows that the solid MOS membrane arrays can be repeatedly recycled and retain their hierarchal mesosponge sink character, avoiding fouling via the precipitation of metal salts as a result of the reuse cycle. The Hg(II) ion rejection and the permeation of nonselective elements based on the membrane filtration protocol may be key considerations in water purification and separation requirements. The selective recovery process of Hg(II) ions in actual contaminated samples collected from tap and underground water sources in Saudi Arabia indicates the practical feasibility of our designed MOS membrane arrays.

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011

Herein, we present a survey of the literature covering the development of molecular imprinting science and technology over the years 2004-2011. In total, 3779 references to the original papers, reviews, edited volumes and monographs from this period are included, along with recently identified uncited materials from prior to 2004, which were omitted in the first instalment of this series covering the years 1930-2003. In the presentation of the assembled references, a section presenting reviews and monographs covering the area is followed by sections describing fundamental aspects of molecular imprinting including the development of novel polymer formats. Thereafter, literature describing efforts to apply these polymeric materials to a range of application areas is presented. Current trends and areas of rapid development are discussed.

Novel creatine biosensors based on all solid-state contact ammonium-selective membrane electrodes

Novel creatine bienzymatic potentiometric biosensors were prepared by immobilizing urease and creatinase on all solid-state contact PVC-containing palmitic acid and carboxylated PVC matrix membrane ammonium-selective electrodes without inner reference solution. Potentiometric characteristics of biosensors were examined in physiological model solutions at different creatine concentrations. The linear working range and long-term sensitivity of the biosensors were also determined. The creatine biosensors prepared by using the carboxylated PVC membrane electrodes showed more effective performance than those of the PVC containing palmitic acid membrane electrodes. Creatine assay in serum samples was successfully carried out by using the standard addition method.

Ultratrace analysis of uracil and 5-fluorouracil by molecularly imprinted polymer brushes grafted to silylated solid-phase microextraction fiber in combination with complementary molecularly imprinted polymer-based sensor

Main inborn errors of metabolism diagnosable through uracil (Ura) analysis and the therapeutic monitoring of toxic 5-fluorouracil (5FU) in dihydro pyrimidine dehydrogenase (DPD) deficient patients require a sensitive, reproducible, selective and accurate method. In this work, an artificial receptor in the format of molecularly imprinted polymer (MIP) brush 'grafted to' the surface of sol-gel immobilized on cost-effective homemade solid-phase microextraction (SPME) fibers, individually imprinted with either of Ura and 5FU, was used in combination with a voltammetric sensor duly modified with the same MIP. This combination provided up to 10- and 8.4-fold preconcentrations of Ura and 5FU, respectively, which was more than sufficient for achieving stringent detection limits in the primitive diagnosis of uracil disorders and fluoropyrimidine toxicity in DPD-deficient patients. The proposed method permits the assessment of Ura and 5FU plasma concentrations with detection limits pf 0.0245 and 0.0484 ng mL(-1) (RSD = 1.0-2.5%, S/N = 3), respectively, without any problems of non-specific false-positives and cross-reactivities in complicated matrices of biological samples.

Molecularly imprinted nanopatterns for the recognition of biological warfare agent ricin

Molecularly imprinted polymer (MIP) for biological warfare agent (BWA) ricin was synthesized using silanes in order to avoid harsh environments during the synthesis of MIP. The synthesized MIP was utilized for the recognition of ricin. The complete removal of ricin from polymer was confirmed by fluorescence spectrometer and SEM-EDAX. SEM and EDAX studies confirmed the attachment of silane polymer on the surface of silica gel matrix. SEM image of Ricin-MIP exhibited nanopatterns and it was found to be entirely different from the SEM image of non-imprinted polymer (NIP). BET surface area analysis revealed more surface area (227 m(2)/g) for Ricin-MIP than that of NIP (143 m(2)/g). In addition, surface area study also showed more pore volume (0.5010 cm(3)/g) for Ricin-MIP than that of NIP (0.2828 cm(3)/g) at 12 nm pore diameter confirming the presence of imprinted sites for ricin as the reported diameter of ricin is 12 nm. The recognition and rebinding ability of the Ricin-MIP was tested in aqueous solution. Ricin-MIP rebound more ricin when compared to the NIP. Chromatogram obtained with Ricin-MIP exhibited two peaks due to imprinting, however, chromatogram of NIP exhibited only one peak for free ricin. SDS-PAGE result confirmed the second peak observed in chromatogram of Ricin-MIP as ricin peak. Ricin-MIP exhibited an imprinting efficiency of 1.76 and it also showed 10% interference from the structurally similar protein abrin.