Improving the Selectivity of the C-C Coupled Product Electrosynthesis by Using Molecularly Imprinted Polymer─An Enhanced Route from Phenol to Biphenol.

We developed a procedure for selective 2,4-dimethylphenol, DMPh, direct electro-oxidation to 3,3',5,5'-tetramethyl-2,2'-biphenol, TMBh, a C-C coupled product. For that, we used an electrode coated with a product-selective molecularly imprinted polymer (MIP). The procedure is reasonably selective toward TMBh without requiring harmful additives or elevated temperatures. The TMBh product itself was used as a template for imprinting. We followed the template interaction with various functional monomers (FMs) using density functional theory (DFT) simulations to select optimal FM. On this basis, we used a prepolymerization complex of TMBh with carboxyl-containing FM at a 1:2 TMBh-to-FM molar ratio for MIP fabrication. The template-FM interaction was also followed by using different spectroscopic techniques. Then, we prepared the MIP on the electrode surface in the form of a thin film by the potentiodynamic electropolymerization of the chosen complex and extracted the template. Afterward, we characterized the fabricated films by using electrochemistry, FTIR spectroscopy, and AFM, elucidating their composition and morphology. Ultimately, the DMPh electro-oxidation was performed on the MIP film-coated electrode to obtain the desired TMBh product. The electrosynthesis selectivity was much higher at the electrode coated with MIP film in comparison with the reference nonimprinted polymer (NIP) film-coated or bare electrodes, reaching 39% under optimized conditions. MIP film thickness and electrosynthesis parameters significantly affected the electrosynthesis yield and selectivity. At thicker films, the yield was higher at the expense of selectivity, while the electrosynthesis potential increase enhanced the TMBh product yield. Computer simulations of the imprinted cavity interaction with the substrate molecule demonstrated that the MIP cavity promoted direct coupling of the substrate to form the desired TMBh product.

Polytyramine Film-Coated Single-Walled Carbon Nanotube Electrochemical Chemosensor with Molecularly Imprinted Polymer Nanoparticles for Duloxetine-Selective Determination in Human Plasma.

We devised, fabricated, and tested differential pulse voltammetry (DPV) and impedance spectroscopy (EIS) chemosensors for duloxetine (DUL) antidepressant determination in human plasma. Polyacrylic nanoparticles were synthesized by precipitation polymerization and were molecularly imprinted with DUL (DUL-nanoMIPs). Then, together with the single-walled carbon nanotube (SWCNT) scaffolds, they were uniformly embedded in polytyramine films, i.e., nanoMIPs-SWCNT@(polytyramine film) surface constructs, deposited on gold electrodes by potentiodynamic electropolymerization. These constructs constituted recognition units of the chemosensors. The molecular dynamics (MD) designing of DUL-nanoMIPs helped select the most appropriate functional and cross-linking monomers and determine the selectivity of the chemosensor. Three different DUL-nanoMIPs and non-imprinted polymer (nanoNIPs) were prepared with these monomers. DUL-nanoMIPs, synthesized from respective methacrylic acid and ethylene glycol dimethyl acrylate as the functional and cross-linking monomers, revealed the highest affinity to the DUL analyte. The linear dynamic concentration range, extending from 10 pM to 676 nM DUL, and the limit of detection (LOD), equaling 1.6 pM, in the plasma were determined by the DPV chemosensor, outperforming the EIS chemosensor. HPLC-UV measurements confirmed the results of DUL electrochemical chemosensing.

Molecularly imprinted polymer-based extended-gate field-effect transistor (EG-FET) chemosensor for selective determination of matrix metalloproteinase-1 (MMP-1) protein.

A conducting molecularly imprinted polymer (MIP) film was integrated with an extended-gate field-effect transistor (EG-FET) transducer to determine epitopes of matrix metalloproteinase-1 (MMP-1) protein biomarker of idiopathic pulmonary fibrosis (IPF) selectively. Most suitable epitopes for imprinting were selected with Basic Local Alignment Search Tool software. From a pool of MMP-1 epitopes, the two, i.e., MIAHDFPGIGHK and HGYPKDIYSS, the relatively short ones, most promising for MMP-1 determination, were selected, mainly considering their advantageous outermost location in the protein molecule and stability against aggregation. MIPs templated with selected epitopes of the MMP-1 protein were successfully prepared by potentiodynamic electropolymerization and simultaneously deposited as thin films on electrodes. The chemosensors, constructed of MIP films integrated with EG-FET, proved useful in determining these epitopes even in a medium as complex as a control serum. The limit of detection for the MIAHDFPGIGHK and HGYPKDIYSS epitope was ∼60 and 20 nM, respectively. Moreover, the chemosensors selectively recognized whole MMP-1 protein in the 50-500 nM concentration range in buffered control serum samples.

Valorizing the Unexplored Filtration Waste of Brewing Industry for Green Silver Nanocomposite Synthesis.

The brewing industry generates a substantial amount of by-products rich in polyphenols, carbohydrates, sugars, sulfates, nitrogen compounds, organic carbon, and several elements, including chlorine, magnesium, and phosphorus. Although limited quantities of these by-products are used in fertilizers and composts, a large amount is discarded as waste. Therefore, it is crucial to identify different ways of valorizing the by-products. Research regarding the valorization of the brewery by-products is still in its nascent stage; therefore, it still has high potential. Herein, we report the valorization of the brewery by-product from the filtration stage of the brewing process (BW9) to synthesize silver nanocomposites as this waste has remained largely unexplored. The BW9 nanocomposites have been compared to those obtained from the brewery product B. The chemical composition analysis of BW9 and B revealed several organic moieties capable of reducing metal salts and capping the formed nanoparticles. Therefore, the brewery waste from stage 9 was valorized as a precursor and added to silver-based precursor at various temperatures (25, 50, and 80 °C) and for various time periods (10, 30, and 120 min) to synthesize silver nanocomposites. The nanocomposites obtained using BW9 were compared to those obtained using the main product of the brewing industry, beer (B). Synthesized nanocomposites composed of AgCl as a major phase and silver metal (Agmet) was incorporated in minor quantities. In addition, Ag3PO4 was also found in B nanocomposites in minor quantities (up to 34 wt.%). The surface morphology depicted globular nanoparticles with layered structures. Small ball-like aggregates on the layer representative of Ag3PO4 were observed in B nanocomposites. The surface of nanocomposites was capped with organic content and functional groups present in the brewery products. The nanocomposites demonstrated high antibacterial activity against Escherichia coli (E. coli), with BW9 nanocomposites exhibiting a higher activity than B nanocomposites.

Cilostazol-imprinted polymer film-coated electrode as an electrochemical chemosensor for selective determination of cilostazol and its active primary metabolite.

An electrochemical chemosensor for cilostazol (CIL) determination was devised, engineered, and tested. For that, a unique conducting film of the functionalized thiophene-appended carbazole-based polymer, molecularly imprinted with cilostazol (MIP-CIL), was potentiodynamically deposited on a Pt disk electrode by oxidative electropolymerization. Thanks to electro-oxidation potentials lower than that of CIL, the carbazole monomers outperformed pyrrole, thiophene, and phenol monomers, in this electropolymerization. The pre-polymerization complexes quantum-mechanical and molecular dynamics analysis allowed selecting the most appropriate monomer from the three thiophene-appended carbazoles examined. The electrode was then used as a selective CIL chemosensor in the linear dynamic concentration range of 50 to 924 nM with a high apparent imprinting factor, IF = 10.6. The MIP-CIL responded similarly to CIL and CIL's pharmacologically active primary metabolite, 3,4-dehydrocilostazol (dhCIL), thus proving suitable for their determination together. Simulated models of the MIP cavities binding of the CIL, dhCIL, and interferences' molecules allowed predicting chemosensor selectivity. The MIP film sorption of CIL and dhCIL was examined using DPV by peak current data fitting with the Langmuir (L), Freundlich (F), and Langmuir-Freundlich (LF) isotherms. The LF isotherm best described this sorption with the sorption equilibrium constant (KLF) for CIL and dhCIL of 12.75 × 10-6 and 0.23 × 10-6 M, respectively. Moreover, the chemosensor cross-reactivity to common interferences study resulted in the selectivity to cholesterol and dehydroaripiprazole of 1.52 and 8.0, respectively. The chemosensor proved helpful in determining CIL and dhCIL in spiked human plasma with appreciable recovery (99.3-134.1%) and limit of detection (15 nM).

Selective Impedimetric Chemosensing of Carcinogenic Heterocyclic Aromatic Amine in Pork by dsDNA-Mimicking Molecularly Imprinted Polymer Film-Coated Electrodes.

Inspired by the easy intercalation of quinoxaline heterocyclic aromatic amines (HAAs) in double-stranded DNA (dsDNA), we synthesized a nucleobase-functionalized molecularly imprinted polymer (MIP) as the recognition unit of an impedimetric chemosensor for the selective determination of a 2-amino-3,7,8-trimethyl-3H-imidazo[4,5-f]quinoxaline (7,8-DiMeIQx) HAA. HAAs are generated in meat and fish processed at high temperatures. They are considered to be potent hazardous carcinogens. The MIP film was prepared by potentiodynamic electropolymerization of a pre-polymerization complex of two adenine- and one thymine-substituted bis(2,2'-bithien-5-yl)methane functional monomer molecules with one 7,8-DiMeIQx template molecule, in the presence of the 2,4,5,2',4',5'-hexa(thiophene-2-yl)-3,3'-bithiophene cross-linking monomer, in solution. The as-formed MIP chemosensor allowed for the selective impedimetric determination of 7,8-DiMeIQx in the 47 to 400 µM linear dynamic concentration range with a limit of detection of 15.5 µM. The chemosensor was successfully applied for 7,8-DiMeIQx determination in the pork meat extract as a proof of concept.

Valorization of Brewery Wastes for the Synthesis of Silver Nanocomposites Containing Orthophosphate.

Brewery wastes from stage 5 (Wort precipitate: BW5) and stage 7 (Brewer's spent yeast: BW7) were valorized for the synthesis of silver phosphate nanocomposites. Nanoparticles were synthesized by converting silver salt in the presence of brewery wastes at different temperatures (25, 50, and 80 °C) and times (10, 30, and 120 min). Unexpectedly, BW7 yielded Ag3PO4 nanoparticles with minor contents of AgCl and Ag metal (Agmet). Contrastingly, BW5 produced AgCl nanoparticles with minor amounts of Ag3PO4 and Agmet. Nanocomposites with different component ratios were obtained by simply varying the synthesis temperature and time. The morphology of the nanocomposites contained ball-like structures representative of Ag3PO4 and stacked layers and fused particles representing AgCl and Agmet. The capping on the nanoparticles contained organic groups from the brewery by-products, and the surface overlayer had a rich chemical composition. The organic overlayers on BW7 nanocomposites were thinner than those on BW5 nanocomposites. Notably, the nanocomposites exhibited high antibacterial activity against Escherichia coli ATCC 25922. The antibacterial activity was higher for BW7 nanocomposites due to a larger silver phosphate content in the composition and a thin organic overlayer. The growth of Agmet in the structure adversely affected the antimicrobial property of the nanocomposites.

Molecularly imprinted polymer nanoparticles-based electrochemical chemosensors for selective determination of cilostazol and its pharmacologically active primary metabolite in human plasma.

Molecularly imprinted polymer (MIP) nanoparticles-based differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) chemosensors for antiplatelet drug substance, cilostazol (CIL), and its pharmacologically active primary metabolite, 3,4-dehydrocilostazol (dhCIL), selective determination in human plasma were devised, prepared, and tested. Molecular mechanics (MM), molecular dynamics (MD), and density functional theory (DFT) simulations provided the optimum structure and predicted the stability of the pre-polymerization complex of the CIL template with the chosen functional acrylic monomers. Moreover, they accounted for the MIP selectivity manifested by the molecularly imprinted cavity with the CIL molecule complex stability higher than that for each interference. On this basis, a fast and reliable method for determining both compounds was developed to meet an essential requirement concerning the personalized drug dosage adjustment. The limit of detection (LOD) at the signal-to-noise ratio of S/N = 3 in DPV and EIS determinations using the ferrocene redox probe in a "gate effect" mode was 93.5 (±2.2) and 86.5 (±4.6) nM CIL, respectively, and the linear dynamic concentration range extended from 134 nM to 2.58 µM in both techniques. The chemosensor was highly selective to common biological interferences, including cholesterol and glucose, and less selective to structurally similar dehydroaripiprazole. Advantageously, it responded to dhCIL, thus allowing for the determination of CIL and dhCIL together. The EIS chemosensor appeared slightly superior to the DPV chemosensor concerning its selectivity to interferences. The CIL DPV sorption data were fitted with Langmuir, Freundlich, and Langmuir-Freundlich isotherms. The determined sorption parameters indicated that the imprinted cavities were relatively homogeneous and efficiently interacted with the CIL molecule.

Electrochemical sensor for selective tyramine determination, amplified by a molecularly imprinted polymer film.

A molecularly imprinted polymer (MIP) film based electrochemical sensor for selective determination of tyramine was devised, fabricated, and tested. Tyramine is generated in smoked and fermented food products. Therefore, it may serve as a marker of the rottenness of these products. Importantly, intake of large amounts of tyramine by patients treated with monoamine oxidase (MAO) inhibitors may lead to a "cheese effect", namely, a dangerous hypertensive crisis. The limit of detection at S/N = 3 of the chemosensor, in both differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) determinations, with the use of the Fe(CN)64-/Fe(CN)63- redox probe, was 159 and 168 µM tyramine, respectively. The linear dynamic concentration range was 290 µM to 2.64 mM tyramine. The chemosensor was highly selective with respect to the glucose, urea, and creatinine interferences. Its DPV determined apparent imprinting factor was 5.6. Moreover, the mechanism of the "gate effect" in the operation of the polymer film-coated electrodes was unraveled.

Low-oxidation-potential thiophene-carbazole monomers for electro-oxidative molecular imprinting: Selective chemosensing of aripiprazole.

New thiophene-carbazole functional and cross-linking monomers electropolymerizing at potentials sufficiently low for molecular imprinting of an electroactive aripiprazole antipsychotic drug were herein designed and synthesized. Numerous conducting molecularly imprinted polymer (MIP) films are deposited by electropolymerization at relatively low potentials by electro-oxidation of pyrrole, aniline, phenol, or 3,4-ethylenedioxythiophene (EDOT). However, their interactions with templates are not sufficiently strong. Hence, it is necessary to introduce additional recognizing sites in these cavities to increase their affinity to the target molecules. For that, functional monomers derivatized with substituents forming stable complexes with the templates are used. However, oxidation potentials of these derivatives are often, disadvantageously, higher than that of parent monomers. Therefore, we designed and synthesized new functional and cross-linking monomers, which are oxidized at sufficiently low potentials. The deposited MIP and non-imprinted polymer (NIP) films were characterized by PM-IRRAS and UV-vis spectroscopy and imaged with AFM. The structure of the aripiprazole pre-polymerization complex with functional monomers was optimized with density functional theory (DFT), and aripiprazole interactions with imprinted cavities were simulated with molecular mechanics (MM) and molecular dynamics (MD). MIP-aripiprazole film-coated electrodes were used as extended gates for selective determination of aripiprazole with the extended-gate field-effect transistor (EG-FET) chemosensor. The linear dynamic concentration range was 30-300 pM, and the limit of detection was 22 fM. An apparent imprinting factor of the MIP-1 was IF = 4.95. The devised chemosensor was highly selective to glucose, urea, and creatinine interferences. The chemosensor was successfully applied for aripiprazole determination in human plasma. The results obtained were compared to those of the validated HPLC-MS method.

Protein Determination with Molecularly Imprinted Polymer Recognition Combined with Birefringence Liquid Crystal Detection.

Liquid crystal-based sensors offer the advantage of high sensitivity at a low cost. However, they often lack selectivity altogether or require costly and unstable biomaterials to impart this selectivity. To incur this selectivity, we herein integrated a molecularly imprinted polymer (MIP) film recognition unit with a liquid crystal (LC) in an optical cell transducer. We tested the resulting chemosensor for protein determination. We examined two different LCs, each with a different optical birefringence. That way, we revealed the influence of that parameter on the sensitivity of the (human serum albumin)-templated (MIP-HSA) LC chemosensor. The response of this chemosensor with the (MIP-HSA)-recognizing film was linear from 2.2 to 15.2 µM HSA, with a limit of detection of 2.2 µM. These values are sufficient to use the devised chemosensor for HSA determination in biological samples. Importantly, the imprinting factor (IF) of this chemosensor was appreciable, reaching IF = 3.7. This IF value indicated the predominant binding of the HSA through specific rather than nonspecific interactions with the MIP.

Influence of the heteroatom introduction on the physicochemical properties of 5-heterotruxenes containing nitrogen, oxygen and sulfur atom.

5-heterotruxenes are a class of heterocyclic aromatic compounds derived from the parent heptacyclic hydrocarbon, namely truxene. Currently, few substances belonging to this group are known. These include derivatives of 5-oxatruxene, 5-azatruxene, and 5-thiatruxene, along with its sulfone and sulfoxide. The introduction of one heteroatom, not only enables selective monofunctionalization of the 5-heterotruxene system but also allows adjustment of physico-chemical properties depending on the needs. Two investigated compounds, namely 5-oxatruxene and 5-azatruxene, exhibit fluorescence enhancement by symmetry breaking (FESB) phenomena, manifested by a fourfold increase in the fluorescence quantum yield. Therefore, derivatives of 5-heterotruxenes may contribute to the development of new stable optoelectronic substances as well as other functional materials. Nevertheless, in the beginning, it is crucial to investigate their spectral, thermal, and electrochemical properties to learn more about the advantages and limitations of these aromatic systems. The following article also presents a new simplified and universal synthetic methodology, without use of anhydrous conditions or organometallic substances, giving easy access to 5-azatruxene and structural-related heteroaromatic systems. The discussed heteroatom influence is not limited to the truxene core but also helps to understand the physicochemical properties of other, currently top-rated high-symmetric heteroaromatic systems such as circulenes, sumanenes and their analogues.

"Gate Effect" in p-Synephrine Electrochemical Sensing with a Molecularly Imprinted Polymer and Redox Probes.

The "gate effect" mechanism for conductive molecularly imprinted polymer (MIP) film coated electrodes was investigated in detail. It was demonstrated that the decrease of the DPV signal for the Fe(CN)64-/Fe(CN)63- redox probe with the increase of the p-synephrine target analyte concentration in solution at the polythiophene MIP-film coated electrode did not originate from swelling or shrinking of the MIP film, as it was previously postulated, but from changes in the electrochemical process kinetics. The MIP-film coated electrode was examined with cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), and surface plasmon resonance (SPR). The MIP-film thickness in the absence and in the presence of the p-synephrine analyte was examined with in situ AFM imaging. Moreover, it was demonstrated that doping of the MIP film was not affected by p-synephrine binding in MIP-film molecular cavities. It was concluded that the "gate effect" was most likely caused by changes in radical cation (polaron) mobility in the film.

Selective PQQPFPQQ Gluten Epitope Chemical Sensor with a Molecularly Imprinted Polymer Recognition Unit and an Extended-Gate Field-Effect Transistor Transduction Unit.

A molecularly imprinted polymer (MIP) recognition system was devised for selective determination of an immunogenic gluten octamer epitope, PQQPFPQQ. For that, a thin MIP film was devised, guided by density functional theory calculations, and then synthesized to become the chemosensor recognition unit. Bis(bithiophene)-based cross-linking and functional monomers were used for this synthesis. An extended-gate field-effect transistor (EG-FET) was used as the transduction unit. The EG-FET gate surface was coated with the PQQPFPQQ-templated MIP film, by electropolymerization, to result in a complete chemosensor. X-ray photoelectron spectroscopy analysis confirmed the presence of the PQQPFPQQ epitope, and its removal from the MIP film. The chemosensor selectively discriminated between the octamer analyte and another peptide of the same number of amino acids but with two of them mismatched (PQQQFPPQ). The chemosensor was validated with respect to both the PQQPFPQQ analyte and a real gluten extract from semolina flour. It was capable to determine PQQPFPQQ in the concentration range of 0.5-45 ppm with the limit of detection (LOD) = 0.11 ppm. Moreover, it was capable of determining gluten in real samples in the concentration range of 4-25 ppm with LOD = 4 ppm, which is a value sufficient for discriminating between gluten-free and non-gluten-free food products. The gluten content in semolina flour determined with the chemosensor well correlated with that determined with a commercial ELISA gluten kit. The Langmuir, Freundlich, and Langmuir-Freundlich isotherms were fitted to the epitope sorption data. The sorption parameters determined from these isotherms indicated that the imprinted cavities were quite homogeneous and that the epitope analyte was chemisorbed in them.

Straightforward Synthesis of Single-Crystalline and Redox-Active Cr(II)-carboxylate MOFs.

We report on a facile and environmentally friendly synthetic approach for single-crystalline chromium(II) carboxylate metal-organic frameworks (i.e., Cr3(BTC)2·3H2O (1) and Cr(hfipbb)·H2O (2) at room temperature in water. Both MOFs can be easily dehydrated, affording single-crystalline materials with open Cr(II) sites. In addition, the redox activity and porosity of the resulting Cr(II) MOFs were examined.

Molecular recognition by synthetic receptors: Application in field-effect transistor based chemosensing.

Molecular recognition, i.e., ability of one molecule to recognize another through weak bonding interactions, is one of the bases of life. It is often implemented to sensing systems of high merits. Preferential recognition of the analyte (guest) by the receptor (host) induces changes in physicochemical properties of the sensing system. These changes are measured by using suitable signal transducers. Because of possibility of miniaturization, fast response, and high sensitivity, field-effect transistors (FETs) are more frequently being used for that purpose. A FET combined with a biological material offers the potential to overcome many challenges approached in sensing. However, low stability of biological materials under measurement conditions is a serious problem. To circumvent this problem, synthetic receptors were integrated with the gate surface of FETs to provide robust performance. In the present critical review, the approach utilized to devise chemosensors integrating synthetic receptors and FET transduction is discussed in detail. The progress in this field was summarized and important outcome was provided.

Synthesis and application of a "plastic antibody" in electrochemical microfluidic platform for oxytocin determination.

By means of molecular imprinting of a conducting polymer, molecular cavities selective for oxytocin nonapeptide, an autism biomarker, were designed. Embedding of the oxytocin template, and then its extracting from the molecularly imprinted polymer (MIP) was confirmed by the XPS analysis. AFM imaging of the MIP film surface indicated changes in mechanical properties of the film after template extraction. The MIP synthetic receptor was deposited by potentiodynamic electropolymerization as a thin film on an Au film electrode in an electrochemical miniaturized microfluidic cell. The use of this cell allowed to shorten analysis time and to decrease the sample volume. The linear dynamic concentration range extended from 0.06 to 1mM with the limit of detection of 60µM (S/N = 3). Advantageously, sensitivity of the diagnostic microfluidic platform devised for oxytocin determination in both synthetic serum samples and in aqueous solutions was similar and, moreover, it was selective to common interferences, such as oxytocin analogs and potential metabolites.

Hierarchical templating in deposition of semi-covalently imprinted inverse opal polythiophene film for femtomolar determination of human serum albumin.

Nanostructured artificial receptor materials with unprecedented hierarchical structure for determination of human serum albumin (HSA) are designed and fabricated. For that purpose a new hierarchical template is prepared. This template allowed for simultaneous structural control of the deposited molecularly imprinted polymer (MIP) film on three length scales. A colloidal crystal templating with optimized electrochemical polymerization of 2,3'-bithiophene enables deposition of an MIP film in the form of an inverse opal. Thickness of the deposited polymer film is precisely controlled with the number of current oscillations during potentiostatic deposition of the imprinted poly(2,3'-bithiophene) film. Prior immobilization of HSA on the colloidal crystal allows formation of molecularly imprinted cavities exclusively on the internal surface of the pores. Furthermore, all binding sites are located on the surface of the imprinted cavities at locations corresponding to positions of functional groups present on the surface of HSA molecules due to prior derivatization of HSA molecules with appropriate functional monomers. This synergistic strategy results in a material with superior recognition performance. Integration of the MIP film as a recognition unit with a sensitive extended-gate field-effect transistor (EG-FET) transducer leads to highly selective HSA determination in the femtomolar concentration range.

Programmed Transfer of Sequence Information into a Molecularly Imprinted Polymer for Hexakis(2,2'-bithien-5-yl) DNA Analogue Formation toward Single-Nucleotide-Polymorphism Detection.

A new strategy of simple, inexpensive, rapid, and label-free single-nucleotide-polymorphism (SNP) detection using robust chemosensors with piezomicrogravimetric, surface plasmon resonance, or capacitive impedimetry (CI) signal transduction is reported. Using these chemosensors, selective detection of a genetically relevant oligonucleotide under FIA conditions within 2 min is accomplished. An invulnerable-to-nonspecific interaction molecularly imprinted polymer (MIP) with electrochemically synthesized probes of hexameric 2,2'-bithien-5-yl DNA analogues discriminating single purine-nucleobase mismatch at room temperature was used. With density functional theory modeling, the synthetic procedures developed, and isothermal titration calorimetry quantification, adenine (A)- or thymine (T)-substituted 2,2'-bithien-5-yl functional monomers capable of Watson-Crick nucleobase pairing with the TATAAA oligodeoxyribonucleotide template or its peptide nucleic acid (PNA) analogue were designed. Characterized by spectroscopic techniques, molecular cavities exposed the ordered nucleobases on the 2,2'-bithien-5-yl polymeric backbone of the TTTATA hexamer probe designed to hybridize the complementary TATAAA template. In that way, an artificial TATAAA-promoter sequence was formed in the MIP. The purine nucleobases of this sequence are known to be recognized by RNA polymerase to initiate the transcription in eukaryotes. The hexamer strongly hybridized TATAAA with the complex stability constant KsTTTATA-TATAAA = ka/kd ≈ 106 M-1, as high as that characteristic for longer-chain DNA-PNA hybrids. The CI chemosensor revealed a 5 nM limit of detection, quite appreciable as for the hexadeoxyribonucleotide. Molecular imprinting increased the chemosensor sensitivity to the TATAAA analyte by over 4 times compared to that of the nonimprinted polymer. The herein-devised detection platform enabled the generation of a library of hexamer probes for typing the majority of SNP probes as well as studying a molecular mechanism of the complex transcription machinery, physics of single polymer molecules, and stable genetic nanomaterials.

Surface enhancement of a molecularly imprinted polymer film using sacrificial silica beads for increasing l-arabitol chemosensor sensitivity and detectability.

Molecular imprinting in polymers leads, among others, to synthetic receptors of high selectivity, comparable to that of their biological counterparts. Deposition of a thin non-porous molecularly imprinted polymer (MIP) film directly on a transducer surface enables fabrication of chemosensors for various health relevant biocompounds. However, the sensitivity of a chemosensor with such an MIP film as the recognition unit is limited, mostly because of slow analyte diffusion through this film. Herein, a simple procedure was developed to enhance, in a controlled way, the active surface area of an l-arabitol imprinted polymer film. For this, a macroporous MIP-(l-arabitol) film was synthesized and simultaneously deposited on a gold electrode of a quartz crystal resonator transducer by potentiodynamic electropolymerization. This large surface area film effectively enhanced analytical signals of mass changes at a quartz crystal microbalance. Hence, the l-arabitol limit of quantification was ∼16-fold better than that of the corresponding non-porous MIP film of the same mass.