Electrochemically synthesized molecularly imprinted polymer of thiophene derivatives for flow-injection analysis determination of adenosine-5'-triphosphate (ATP)

Green Synthesis of a Molecularly Imprinted Polymer Based on a Novel Thiophene-Derivative for Electrochemical Sensing

An environmentally friendly and sustainable approach was adopted to produce a molecularly imprinted polymer (MIP) via electropolymerization, with remarkable electrochemical sensing properties, tested in tyrosine (tyr) detection. The 2,2'-bis(2,2'-bithiophene-5-yl)-3,3'-bithianaphtene (BT2-T4) was chosen as functional monomer and MIP electrosynthesis was carried out via cyclic voltammetry on low-volume (20 μL) screen-printed carbon electrodes (C-SPE) in ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ((BMIM) TFSI). An easy and rapid washing treatment allowed us to obtain the resulting MIP film, directly used for tyr electrochemical detection, carried out amperometrically. The sensor showed a linear response in the concentration range of 15-200 μM, with LOD of 1.04 µM, LOQ of 3.17 μM and good performance in selectivity, stability, and reproducibility. Tyrosine amperometric detection was also carried out in human plasma, resulting in a satisfactory recovery estimation. The work represents the first use of BT2-T4 as a functional monomer for the production of a molecularly imprinted polymer, with a green approach afforded by using a few microliters of a room temperature ionic liquid as an alternative to common organic solvents on screen-printed carbon electrodes, resulting in a valuable system that meets the green chemistry guidelines, which is today an essential criterion in both research and application field.

Novel adsorptive materials by adenosine 5'-triphosphate imprinted-polymer over the surface of polystyrene nanospheres for selective separation of adenosine 5'-triphosphate biomarker from urine

In this study, we have developed a method to assess adenosine 5'-triphosphate by adsorptive extraction using surface adenosine 5'-triphosphate-imprinted polymer over polystyrene nanoparticles (412 ± 16 nm) for selective recognition/separation from urine. Molecularly imprinted polymer was synthesized by emulsion copolymerization reaction using adenosine 5'-triphosphate as a template, functional monomers (methacrylic acid, N-isopropyl acrylamide, and dimethylamino ethylmethacrylate) and a crosslinker, methylenebisacrylamide. The binding capacities of imprinted and non-imprinted polymers were measured using high-performance liquid chromatography with UV detection with a detection limit of 1.6 ± 0.02 µM of adenosine 5'-triphosphate in the urine. High binding affinity (Q_MIP , 42.65 µmol/g), and high selectivity and specificity to adenosine 5'-triphosphate compared to other competitive nucleotides including adenosine 5'-diphosphate, adenosine 5'-monophosphate, and analogs such as adenosine, adenine, uridine, uric acid, and creatinine were observed. The imprinting efficiency of imprinted polymer is 2.11 for urine (Q_MIP , 100.3 µmol/g) and 2.51 for synthetic urine (Q_MIP , 48.5 µmol/g). The extraction protocol was successfully applied to the direct extraction of adenosine 5'-triphosphate from spiked human urine indicating that this synthesized molecularly imprinted polymer allowed adenosine 5'-triphosphate to be preconcentrated while simultaneously interfering compounds were removed from the matrix. These submicron imprinted polymers over nano polystyrene spheres have a potential in the pharmaceutical industries and clinical analysis applications.

Promoting bioanalytical concepts in genetics: A TATA box molecularly imprinted polymer as a small isolated fragment of the DNA damage repairing system

We demonstrate that a new, stable, artificial TATA (T - thymine, A - adenine) box is recognized by amino acids recognizing the natural TATA box. Here, the former mimicked, as a minimal motif, oligodeoxyribonucleotide interactions with amino acids of proteins involved in repairing of damaged dsDNA. By electropolymerization, we molecularly imprinted non-labeled 5'-TATAAA-3' via Watson-Crick nucleobase pairing, thus synthesizing, in a one-step procedure, the hexakis[bis(2,2'-bithien-5-yl)] TTTATA and simultaneously hybridizing it with the 5'-TATAAA-3' template. That is, a stable dsDNA analog having a controlled sequence of nucleobases was formed in the molecularly imprinted polymer (MIP). The 5'-TATAAA-3' was by the X-ray photoelectron spectroscopy (XPS) depth profiling found to be homogeneously distributed both in the bulk of the MIP film and on its surface. The 5'-TATAAA-3' concentration in the 2.8(±0.2)-nm relative surface area, ~140-nm thick MIP film was 2.1 mM. The MIP served as a matrix of an artificial TATA box with the TATAAA-promoter sequence. We comprehensively characterized this artificial DNA hybrid by the polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and X-ray photoelectron spectroscopy (XPS). Further, we examined interactions of DNA repairing TATA binding protein (TBP) amino acids with the artificial TATA box prepared. That is, molecules of l-phenylalanine aromatic amino acid were presumably engaged in stacking interactions with nucleobase steps of this artificial TATA box. The nitrogen-to‑phosphorus atomic % ratio on the surface of the MIP-(5'-TATAAA-3') film increased by ~1.6 times after film immersing in the l-glutamic acid solution, as determined using the XPS depth profiling. Furthermore, l-lysine and l-serine preferentially interacted with the phosphate moiety of 5'-TATAAA-3'. We monitored amino acids interactions with the artificial TATA box using real-time piezoelectric microgravimetry at a quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) spectroscopy under flow injection analysis (FIA) conditions.

Single frequency analysis for clinical immunosensor design

A novel bioelectrochemical approach: Tau protein determination for the diagnosis of neurodiseases via time-dependant phase angle shift.

Boronate affinity materials for separation and molecular recognition: structure, properties and applications

Boronate affinity materials, as unique sorbents, have emerged as important media for the selective separation and molecular recognition of cis-diol-containing compounds. With the introduction of boronic acid functionality, boronate affinity materials exhibit several significant advantages, including broad-spectrum selectivity, reversible covalent binding, pH-controlled capture/release, fast association/desorption kinetics, and good compatibility with mass spectrometry. Because cis-diol-containing biomolecules, including nucleosides, saccharides, glycans, glycoproteins and so on, are the important targets in current research frontiers such as metabolomics, glycomics and proteomics, boronate affinity materials have gained rapid development and found increasing applications in the last decade. In this review, we critically survey recent advances in boronate affinity materials. We focus on fundamental considerations as well as important progress and new boronate affinity materials reported in the last decade. We particularly discuss on the effects of the structure of boronate ligands and supporting materials on the properties of boronate affinity materials, such as binding pH, affinity, selectivity, binding capacity, tolerance for interference and so on. A variety of promising applications, including affinity separation, proteomics, metabolomics, disease diagnostics and aptamer selection, are introduced with main emphasis on how boronate affinity materials can solve the issues in the applications and what merits boronate affinity materials can provide.

Selective electrochemical sensing of human serum albumin by semi-covalent molecular imprinting

We devised and prepared a conducting molecularly imprinted polymer (MIP) for human serum albumin (HSA) determination using semi-covalent imprinting. The bis(2,2'-bithien-5-yl)methane units constituted the MIP backbone. This MIP was deposited as a thin film on an Au electrode by oxidative potentiodynamic electropolymerization to fabricate an electrochemical chemosensor. The HSA template imprinting, and then its releasing from the MIP was confirmed by the differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), XPS, and PM-IRRAS measurements as well as by AFM imaging. Semi-covalent imprinting provided a very well defined locations of recognition sites in the MIP molecular cavities. These sites populated the imprinted cavities or the MIP surface only. The DPV and EIS response of the MIP film coated electrode to the HSA analyte was linear in the range of 0.8 to 20 and 4 to 80 µg/mL HSA, respectively, with the limit of detection of 16.6 and 800 ng/mL, respectively. The impressively high imprinting factor reached, exceeding 20, strongly confirmed that semi-covalent imprinting resulted in formation of a large number of very well defined molecular cavities with high affinity to the HSA molecules. The MIP selectivity against low-(molecular weight) interferences, common for physiological fluids, such as blood and urea, was very high. There was no response to the presence of these interferences at concentrations encountered in the samples analyzed. Moreover, the chemosensor selectivity to the myoglobin and cytochrome c interferences was excellent while that to lysozyme was slightly lower but still high. The chemosensor was useful for determination of abnormal HSA concentration in a control blood serum.

Molecularly imprinted polymers as recognition materials for electronic tongues

For over three decades now, molecularly imprinted polymers (MIPs) have successfully been used for selective chemical sensing because the shape and size of their imprinted molecular cavities perfectly matched those of the target analyte molecules. Moreover, orientation of recognizing sites of these cavities corresponded to those of the binding sites of the template molecules. In contrast, electronic tongue (e-tongue) is usually an array of low-affinity recognition units. Its selectivity is based on recognition pattern or multivariate analysis. Merging these two sensing devices led to a synergetic hybrid sensor, an MIP based e-tongue. Fabrication of these e-tongues permitted simultaneous sensing and discriminating several analytes in complex solutions of many components so that these arrays compensated for limitation in cross-reactivity of MIPs. Apparently, analytical signals generated by MIP-based e-tongues, compared to those of ordinary sensor arrays, were more reliable where a unique pattern or 'fingerprint' for each analyte was generated. Additionally, several transduction platforms (from spectroscopic to electrochemical) engaged in constructing MIP-based e-tongues, found their broad and flexible applications. The present review critically evaluates achievements in recent developments of the MIP based e-tongues for chemosensing.

Fullerene derived molecularly imprinted polymer for chemosensing of adenosine-5'-triphosphate (ATP)

For molecular imprinting of oxidatively electroactive analytes by electropolymerization, we used herein reductively electroactive functional monomers. As a proof of concept, we applied C60 fullerene adducts as such for the first time. For that, we derivatized C60 to bear either an uracil or an amide, or a carboxy addend for recognition of the adenosine-5'-triphosphate (ATP) oxidizable analyte with the ATP-templated molecularly imprinted polymer (MIP-ATP). Accordingly, the ATP complex with all of the functional monomers formed in solution was potentiodynamically electropolymerized to deposit an MIP-ATP film either on an Au electrode of the quartz crystal resonator or on a Pt disk electrode for the piezoelectric microgravimetry (PM) or capacitive impedimetry (CI) determination of ATP, respectively, under the flow-injection analysis (FIA) conditions. The apparent imprinting factor for ATP was ∼4.0. After extraction of the ATP template, analytical performance of the resulting chemosensors, including detectability, sensitivity, and selectivity, was characterized. The limit of detection was 0.3 and 0.03mM ATP for the PM and CI chemosensor, respectively. The MIP-ATP film discriminated structural analogues of ATP quite well. The Langmuir, Freundlich, and Langmuir-Freundlich isotherms were fitted to the experimental data of the ATP sorption and sorption stability constants appeared to be nearly independent of the adopted sorption model.

Poly(glycidyl methacrylate-co-N-methylolacrylamide-co-ethylene dimethacrylate) monolith coupled to high-performance liquid chromatography for the determination of adenosine phosphates in royal jelly

A polymer monolith microextraction method coupled with high-performance liquid chromatography was developed for the determination of adenosine triphosphate, adenosine diphosphate, and adenosine monophosphate. The monolithic column was synthesized inside fused-silica capillaries using thermal initiation free-radical polymerization with glycidyl methacrylate as the monomer, ethylene dimethacrylate as the cross-linker, cyclohexanol, and 1-dodecanol as the porogen. N-Methylolacrylamide, an important hydrophilic monomer, was incorporated into the polymerization mixture to enhance the hydrophilicity of the poly(glycidyl methacrylate-co-ethylene dimethacrylate) column. The obtained poly(glycidyl methacrylate-co-N-methylolacrylamide-co-ethylene dimethacrylate) monolith was characterized by scanning electron microscopy, Fourier-transform infrared spectra, and X-ray photoelectron spectroscopy. Optimum conditions for the preconcentration and separation of the target adenosines were also investigated. Under the optimum conditions, we obtained acceptable linearities, low limits of detection, and good relative standard deviations. The developed polymer monolith microextraction with high-performance liquid chromatography method exhibited a good performance with recovery values in the range of 76.9-104.7% when applied to the determination of the adenosines in five royal jelly samples.

Novel electrochemical sensing platform based on magnetic field-induced self-assembly of Fe3O4@Polyaniline nanoparticles for clinical detection of creatinine

A novel electrochemical sensing platform based on magnetic field-induced self-assembly of Fe3O4@Polyaniline nanoparticles (Fe3O4@PANI NPs) has been for the first time fabricated for the sensitive detection of creatinine in biological fluids. The template molecule, creatinine, was self-assembled on the surface of Fe3O4@PANI NPs together with the functional monomer aniline by the formation of N-H hydrogen bonds. After pre-assembled, through the magnetic-induction of the magnetic glassy carbon electrode (MGCE), the ordered structure of molecularly imprinted polymers (MIPs) were established by the electropolymerization and assembled on the surface of MGCE with the help of magnetic fields by a simple one-step approach. The structural controllability of the MIPs film established by magnetic field-induced self-assembly was further studied. The stable and hydrophilic Fe3O4@PANI can not only provide available functionalized sites with which the template molecule creatinine can form hydrogen bond by the abundant amino groups in PANI matrix, but also afford a promoting pathway for electron transfer. The as-prepared molecularly imprinted electrochemical sensor (MIES) shows good stability and reproducibility for the determination of creatinine with the detection limit reached 0.35 nmol L(-1) (S/N=3). In addition, the highly sensitive and selective MIES has been successfully used for the clinical determination of creatinine in human plasma and urine samples. The average recoveries were 90.8-104.9% with RSD lower than 2.7%.

Molecularly imprinted polymer for recognition of 5-fluorouracil by RNA-type nucleobase pairing

A 6-aminopurine (adenine) derivative of bis(2,2'-bithienyl)methane, vis., 4-[2-(6-amino-9H-purin-9-yl)ethoxy]phenyl-4-[bis(2,2'-bithienyl)methane] or Ade-BTM, was designed and synthesized for recognition of 5-fluorouracil (FU), an antitumor chemotherapy agent, by RNA-type (nucleobase pairing)-driven molecular imprinting. The prepolymerization complex stoichiometry involved one FU molecule and two molecules of the Ade-BTM functional monomer. Molecular structure of this complex was thermodynamically optimized via density functional theory at the B3LYP/3-21G* level. The stability constant of the FU-Ade-BTM complex of 1:2 stoichiometry was K = 2.17(±0.07) × 10(7) M(-2), as determined by titration with quenching of fluorescence of the bis(2,2'-bithienyl)methane moiety of Ade-BTM by the FU titrant, in benzonitrile, at 352 nm excitation. Next, (5-fluorouracil)-templated molecularly imprinted polymer (MIP-FU) films were deposited on indium-tin oxide (ITO) or Au film-coated glass slides, Pt disk electrodes, or 10-MHz quartz crystal resonators by potentiodynamic electropolymerization from solution of FU, Ade-BTM, and tris([2,2'-bithiophen]-5-yl)methane (TTM) cross-linking monomer at FU:Ade-BTM:TTM = 1:2:3 mol ratio. Then UV-visible and Fourier transform infrared (FT-IR) spectra of the MIP-FU films were recorded to confirm the FU template presence in the MIP-FU film and its subsequent release by extraction with methanol from this film. For determination of the stability constant of the complex of the MIP cavity and FU, piezoelectric microgravimetry (PM) under both batch- and flow-injection analysis conditions was used. For sensing application, three different transduction platforms [differential pulse voltammetry (DPV), capacitive impedimetry (CI), and PM] were integrated with the MIP-FU recognition unit. The limit of detection (LOD) was 56 nM, 75 nM, and 0.26 mM, for these chemosensors, respectively, indicating suitability of the former two for FU determination in blood plasma or serum (~500 nM). Moreover, the CI chemosensor was appreciably more sensitive to FU than to their common interferences.

Piezomicrogravimetric and impedimetric oligonucleotide biosensors using conducting polymers of biotinylated bis(2,2'-bithien-5-yl)methane as recognition units

A new conducting polymer of biotinylated bis(2,2'-bithien-5-yl)methane was prepared and applied as the recognition unit of two different biosensors for selective oligonucleotide determination using either electrochemical impedance spectroscopy (EIS) or piezoelectric microgravimetry (PM) for label-free analytical signal transduction. For preparation of this unit, first, a biotinylated bis(2,2'-bithien-5-yl)methane functional monomer was designed and synthesized. Then, this monomer was potentiodynamically polymerized to form films on the surface of a glassy carbon electrode (GCE) and a Au electrode of a quartz crystal resonator (QCR) for the EIS and PM transduction, respectively. On top of these films, neutravidin was irreversibly immobilized by complexing the biotin moieties of the polymer. Finally, recognizing biotinylated oligonucleotide was attached by complexing the surface-immobilized neutravidin. This layer-by-layer assembling of the poly(thiophene-biotin)-neutravidin-(biotin-oligonucleotide) recognition film served to determine the target oligonucleotide via complementary nucleobase pairing. Under optimized determination conditions, the target oligonucleotide limit of detection (LOD) was 0.5 pM and 50 nM for the EIS and PM transduction, respectively. The sensor response to the target oligonucleotide was linear with respect to logarithm of the target oligonucleotide concentration in a wide range of 0.5 pM to 30 μM and with respect to its concentration in the range of 50 to 600 nM for the EIS and PM transduction, respectively. The biosensors were appreciably selective with respect to the nucleobase mismatched oligonucleotides.