Sulphonamide-imprinted sol–gel materials as ionophores in potentiometric transduction

Potentiometric Sensor Arrays Based on Hybrid PFSA/CNTs Membranes for the Analysis of UV-Degraded Drugs

The degradation of drugs is a substantial problem since it affects the safety and effectiveness of pharmaceutical products, as well as their influence on the environment. A novel system of three potentiometric cross-sensitive sensors (using the Donnan potential (DP) as an analytical signal) and a reference electrode was developed for the analysis of UV-degraded sulfacetamide drugs. The membranes for DP-sensors were prepared by a casting procedure from a dispersion of perfluorosulfonic acid (PFSA) polymer, containing carbon nanotubes (CNTs), whose surface was preliminarily modified with carboxyl, sulfonic acid, or (3-aminopropyl)trimethoxysilanol groups. A correlation between the sorption and transport properties of the hybrid membranes and cross-sensitivity of the DP-sensor to sulfacetamide, its degradation product, and inorganic ions was revealed. The analysis of the UV-degraded sulfacetamide drugs using the multisensory system based on hybrid membranes with optimized properties did not require a pre-separation of the components. The limits of detection of sulfacetamide, sulfanilamide, and sodium were 1.8 × 10^-7, 5.8 × 10^-7, and 1.8 × 10^-7 M. The relative errors of the determination of the components of the UV-degraded sulfacetamide drugs were 2-3% (at 6-8% relative standard deviation). PFSA/CNT hybrid materials provided the stable work of the sensors for at least one year.

Multisensory Systems Based on Perfluorosulfonic Acid Membranes Modified with Functionalized CNTs for Determination of Sulfamethoxazole and Trimethoprim in Pharmaceuticals

Sulfamethoxazole and trimethoprim are synthetic bacteriostatic drugs. A potentiometric multisensory system for the analysis of sulfamethoxazole and trimethoprim combination drugs was developed. Perfluorosulfonic acid membranes containing functionalized CNTs were used as the sensor materials. The CNTs' surface was modified by carboxyl, sulfonic acid, or (3-aminopropyl)trimethoxysilanol groups. The influence of the CNT concentration and the properties of their surface, as well as preliminary ultrasonic treatment of the polymer and CNT solution before the casting of hybrid membranes, on their ion-exchange capacity, water uptake, and transport properties was revealed. Cross-sensitivity of the sensors to the analytes was achieved due to ion exchange and hydrophobic interactions with hybrid membranes. An array of cross-sensitive sensors based on the membranes containing 1.0 wt% of CNTs with sulfonic acid or (3-aminopropyl)trimethoxysilanol groups enabled us to provide the simultaneous determination of sulfamethoxazole and trimethoprim in aqueous solutions with a concentration ranging from 1.0 × 10^-5 to 1.0 × 10^-3 M (pH 4.53-8.31). The detection limits of sulfamethoxazole and trimethoprim were 3.5 × 10^-7 and 1.3 × 10^-7 М. The relative errors of sulfamethoxazole and trimethoprim determination in the combination drug as compared with the content declared by the manufacturer were 4% (at 6% RSD) and 5% (at 7% RSD).

Multisensory Systems Based on Perfluorosulfonic Acid Membranes Modified with Polyaniline and PEDOT for Multicomponent Analysis of Sulfacetamide Pharmaceuticals

The degradation of sulfacetamide with the formation of sulfanilamide leads to a deterioration in the quality of pharmaceuticals. In this work, potentiometric sensors for the simultaneous determination of sulfanilamide, sulfacetamide and inorganic ions, and for assessing the degradation of pharmaceuticals were developed. A multisensory approach was used for this purpose. The sensor cross-sensitivity to related analytes was achieved using perfluorosulfonic acid membranes with poly(3,4-ethylenedioxythiophene) or polyaniline as dopants. The composite membranes were prepared by oxidative polymerization and characterized using FTIR and UV-Vis spectroscopy, and SEM. The influence of the preparation procedure and the dopant concentration on the membrane hydrophilicity, ion-exchange capacity, water uptake, and transport properties was investigated. The characteristics of the potentiometric sensors in aqueous solutions containing sulfanilamide, sulfacetamide and alkali metals ions in a wide pH range were established. The introduction of proton-acceptor groups and π-conjugated moieties into the perfluorosulfonic acid membranes increased the sensor sensitivity to organic analytes. The relative errors of sulfacetamide and sulfanilamide determination in the UV-degraded eye drops were 1.2 to 1.4 and 1.7 to 4%, respectively, at relative standard deviation of 6 to 9%.

Potentiometric Biosensor Based on Artificial Antibodies for an Alzheimer Biomarker Detection

This paper presents a potentiometric biosensor for the detection of amyloid β-42 (Aβ-42) in point-of-care analysis. This approach is based on the molecular imprint polymer (MIP) technique, which uses covalently immobilised Aβ-42 to create specific detection cavities on the surface of single-walled carbon nanotubes (SWCNTs). The biosensor was prepared by binding Aβ-42 to the SWCNT surface and then imprinting it by adding acrylamide (monomer), N,N’-methylene-bis-acrylamide (crosslinker) and ammonium persulphate (initiator). The target peptide was removed from the polymer matrix by the proteolytic action of an enzyme (proteinase K). The presence of imprinting sites was confirmed by comparing a MIP-modified surface with a negative control (NIP) consisting of a similar material where the target molecule had been removed from the process. The ability of the sensing material to rebind Aβ-42 was demonstrated by incorporating the MIP material as an electroactive compound in a PVC/plasticiser mixture applied to a solid conductive support of graphite. All steps of the synthesis of the imprinted materials were followed by Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). The analytical performance was evaluated by potentiometric transduction, and the MIP material showed cationic slopes of 75 mV-decade−1 in buffer pH 8.0 and a detection limit of 0.72 μg/mL. Overall, potentiometric transduction confirmed that the sensor can discriminate Aβ-42 in the presence of other biomolecules in the same solution.

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.

Bio-mimetic sensors based on molecularly imprinted membranes

An important challenge for scientific research is the production of artificial systems able to mimic the recognition mechanisms occurring at the molecular level in living systems. A valid contribution in this direction resulted from the development of molecular imprinting. By means of this technology, selective molecular recognition sites are introduced in a polymer, thus conferring it bio-mimetic properties. The potential applications of these systems include affinity separations, medical diagnostics, drug delivery, catalysis, etc. Recently, bio-sensing systems using molecularly imprinted membranes, a special form of imprinted polymers, have received the attention of scientists in various fields. In these systems imprinted membranes are used as bio-mimetic recognition elements which are integrated with a transducer component. The direct and rapid determination of an interaction between the recognition element and the target analyte (template) was an encouraging factor for the development of such systems as alternatives to traditional bio-assay methods. Due to their high stability, sensitivity and specificity, bio-mimetic sensors-based membranes are used for environmental, food, and clinical uses. This review deals with the development of molecularly imprinted polymers and their different preparation methods. Referring to the last decades, the application of these membranes as bio-mimetic sensor devices will be also reported.

Molecularly imprinted membranes

Although the roots of molecularly imprinted polymers lie in the beginning of 1930s in the past century, they have had an exponential growth only 40-50 years later by the works of Wulff and especially by Mosbach. More recently, it was also proved that molecular imprinted membranes (i.e., polymer thin films) that show recognition properties at molecular level of the template molecule are used in their formation. Different procedures and potential application in separation processes and catalysis are reported. The influences of different parameters on the discrimination abilities are also discussed.

Disposable and integrated amperometric immunosensor for direct determination of sulfonamide antibiotics in milk

The preparation and performance of a disposable amperometric immunosensor, based on the use of a selective capture antibody and screen-printed carbon electrodes (SPCEs), for the specific detection and quantification of sulfonamide residues in milk is reported. The antibody was covalently immobilized onto a 4-aminobenzoic acid (4-ABA) film grafted on the disposable electrode, and a direct competitive immunoassay using a tracer with horseradish peroxidase (HRP) for the enzymatic labeling was performed. The amperometric response measured at -0.2 V vs the silver pseudo-reference electrode of the SPCE upon the addition of H(2)O(2) in the presence of hydroquinone (HQ) as mediator was used as transduction signal. The developed methodology showed very low limits of detection (in the low ppb level) for 6 sulfonamide antibiotics tested in untreated milk samples, and a good selectivity against other families of antibiotics residues frequently detected in milk and dairy products. These features, together with the short analysis time (30 min), the simplicity, and easy automation and miniaturization of the required instrumentation make the developed methodology a promising alternative in the development of devices for on-site analysis.