Nicotine, Cotinine, and Myosmine Determination Using Polymer Films of Tailor-Designed Zinc Porphyrins as Recognition Units for Piezoelectric Microgravimetry Chemosensors

Two electropolymerizable zinc porphyrins with receptor sites tailor-designed for selective recognition of the nicotine, cotinine, or myosmine alkaloids were synthesized. These were 5-(2-phenoxyacetamide)-10,15,20-tris­(triphenylamino)­porphyrinato zinc­(II) <b>1</b> and 5-(2,5-phenylene-bis­(oxy)­diacetamide)-10,15,20-tris­(triphenylamino)­porphyrinato zinc­(II) <b>2</b> featuring one and two pendant amide side “pincers”, respectively, and three triphenylamine substituents at the meso positions of the porphyrin macrocycles capable of electrochemical polymerization. Thin polymer films of these porphyrins served for recognition and the piezoelectric microgravimetry (PM) for analytical signal transduction of a new chemical sensor devised for determination of these alkaloids. The films were deposited by potentiodynamic electropolymerization on the 10 MHz quartz resonators of the electrochemical quartz crystal microbalance (EQCM) without affecting the electronic structure of the porphyrin macrocycles. Under favorable flow injection analysis (FIA) conditions, the alkaloid analytes were determined at the concentration level of 0.1 mM with high sensitivity and selectivity. Affinity toward the analytes of the polymer of <b>2</b> was higher than that of <b>1</b> due to the higher binding ability offered by two pendant pincers of the former. Because of the selective receptors and PM applied under FIA conditions, the developed procedure offered an alternative to the time-consuming and relatively expensive high-performance liquid chromatography (HPLC), capillary electrophoresis (CE), and gas chromatography mass spectrometry (GC-MS) methods of detection and quantification of these alkaloids

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 (<b>1</b>) and Cr­(hfipbb)·H₂O (<b>2</b>) 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

Molecularly Imprinted Polymer (MIP) Film with Improved Surface Area Developed by Using Metal–Organic Framework (MOF) for Sensitive Lipocalin (NGAL) Determination

Electropolymerizable functional and cross-linking monomers were used to prepare conducting molecularly imprinted polymer film with improved surface area with the help of a sacrificial metal–organic framework (MOF). Subsequent dissolution of the MOF layer resulted in a surface developed MIP film. This surface enlargement increased the analyte accessibility to imprinted molecular cavities. Application of the porous MIP film as a recognition unit of an extended-gate field effect transistor (EG-FET) chemosensor effectively enhanced analytical current signals of determination of recombinant human neutrophil gelatinase-associated lipocalin (NGAL

Langmuir–Blodgett Films of Self-Assembled (Alkylether-Derivatized Zn Phthalocyanine)–(C₆₀ Imidazole Adduct) Dyad with Controlled Intermolecular Distance for Photoelectrochemical Studies

A multilayer Langmuir–Blodgett (LB) film of the self-assembled electron donor–acceptor dyad of Zn phthalocyanine, appended with four long-chain aliphatic ether peripheral substituents, and an imidazole adduct of C₆₀ was prepared and applied as a photoactive material in a photoelectrochemical cell. Changes in the simultaneously recorded surface pressure and surface potential vs area per molecule compression isotherms for Langmuir films of the dyad and, separately, of its components helped to identify phase transitions and mutual interactions of molecules in films. The Brewster angle microscopy (BAM) imaging of the Langmuir films showed circular condensed phase domains of the dyad molecules. The determined area per molecule was lower than that estimated for the dyad and its components, separately. The multilayer LB films of the dyad were transferred onto hydrophobized fluorine-doped tin oxide-coated (FTO) glass slides under different conditions. The presence of both components in the dyad LB films was confirmed with the UV–vis spectroscopy measurements. For the LB films transferred at different surface pressures, the PM-IRRAS measurements revealed that the phthalocyanine macrocycle planes and ether moieties in films were tilted with respect to the FTO surface. The AFM imaging of the LB films indicated formation of relatively uniform dyad LB films. Then, the femtosecond transient absorption spectral studies evidenced photoinduced electron transfer in the LB film. The obtained transient signals corresponding to both Zn­(TPPE)^<b>•</b>+ and C₆₀im^{<b>•–</b>} confirmed the occurrence of intramolecular electron transfer. The determined rate constants of charge separation, <i>k</i>_cs = 2.6 × 10¹¹ s^–1, and charge recombination, <i>k</i>_cr = 9.7 × 10⁹ s^–1, indicated quite efficient electron transfer within the film. In the photoelectrochemical studies, either photoanodic or photocathodic current was generated depending on the applied bias potential when the dyad LB film-coated FTO was used as the working electrode and ascorbic acid or methylviologen, respectively, as the charge mediator in an aqueous solution

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 <i>K</i>_s^{TTTATA–TATAAA} = <i>k</i>_a/<i>k</i>_d ≈ 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