Maciej Cieplak

Early diagnosis of fungal infections using piezomicrogravimetric and electric chemosensors based on polymers molecularly imprinted with d-arabitol

An elevated concentration of d-arabitol in urine, especially compared to that of l-arabitol or creatinine, is indicative of a fungal infection. For that purpose, we devised, fabricated, and tested chemical sensors determining d-arabitol. These chemosensors comprised the quartz crystal resonator (QCR) or extended-gate field-effect transistor (EG-FET) transducers integrated with molecularly imprinted polymer (MIP) film recognition units. To this end, we successfully applied a covalent approach to molecular imprinting, which involved formation of weak reversible covalent bonds between vicinal hydroxyl groups of arabitol and boronic acid substituents of the bithiophene functional monomer used. The MIP films were synthesized and simultaneously deposited on gold electrodes of quartz crystal resonators (Au-QCRs) or Au-glass slides by oxidative potentiodynamic electropolymerization. With the QCR and EG-FET chemosensors, the d-arabitol concentration was determined under flow-injection analysis and stagnant-solution binding conditions, respectively. Selectivity with respect to common interferences, and l-arabitol in particular, of the devised chemosensors was superior. Limits of detection and linear dynamic concentration ranges of the QCR and EG-FET chemosensors were 0.15 mM and 0.15 to 1.25 mM as well as 0.12 mM and 0.12 to 1.00 mM, respectively, being lower than the d-arabitol concentrations in urine of patients with invasive candidiasis (>220 μM). Therefore, the devised chemosensors are suitable for early diagnosis of fungal infections caused by Candida sp. yeasts.

Nanostructured molecularly imprinted polymers for protein chemosensing

Molecularly imprinted polymers (MIPs) are tailor made recognition materials that can mimic biological receptors. If used as recognition units for chemosensors fabrication, they outperform natural receptors with their durability, chemical stability, and low production costs. Novel techniques of MIP deposition as thin films, surface development, and introduction of additional properties are very much demanded in terms of selective and sensitive chemosensors fabrication. Therefore, in recent years a particular attention has been paid to syntheses of nanostructured MIP films and MIP nanoparticles. The present brief review surveys novel achievements in the field of MIP nanostructures and their application for determination of protein analytes.

Molecularly Imprinted Polymer Chemosensor for Selective Determination of an N-Nitroso-l-proline Food Toxin

A molecularly imprinted polymer (MIP)-based chemosensor for the selective determination of a chosen toxin, N-nitroso-l-proline (Pro-NO), was devised and fabricated. By means of DFT, the structure of the pre-polymerization (functional monomer)-template complex was modeled. This complex was then potentiodynamically electropolymerized in the presence of cross-linking monomer to form a MIP-Pro-NO thin film. Next, the Pro-NO template was extracted from MIP-Pro-NO with 0.1 m NaOH. Piezoelectric microgravimetry (PM) on an electrochemical quartz crystal microbalance and electrochemical (differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS)) techniques were used to transduce binding of Pro-NO to molecular cavities of the MIP-Pro-NO. With DPV and EIS chemosensing, the limits of detection (LODs) were about 80.9 and 36.9 nM Pro-NO, respectively; and the selectivity coefficients for urea, glucose, creatinine, and adrenalin interferences were 6.6, 13.2, 2.1, and 2.0, respectively, with DPV as well as 2.3, 2.0, 3.3, and 2.5, respectively, with EIS. With PM under flow injection analysis conditions, the LOD was 10 μm Pro-NO. The MIP-Pro-NO chemosensor detectability and selectivity with respect to interferences were sufficiently high to determine Pro-NO in protein-providing food products.

Synthesis of octitols and the respective amino-derivatives from 'organo-aldols'.

Two diastereoisomeric keto-octoses, obtained in the reaction of 2,3:4,5-diacetone-D-arabinose with protected dihydroxyacetone catalyzed with L- or D-proline, were converted into octitols by stereoselective reduction of the carbonyl group with zinc borohydride and final deprotection. The study on the preparation of the respective amino-derivatives by reductive amination of these organo-adducts is presented; stereochemical aspects of these processes are discussed.

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.

CHAPTER 9:Protein Determination Using Molecularly Imprinted Polymer (MIP) Chemosensors

Synthesis of molecularly imprinted polymers (MIPs) using macromolecular templates (Mw > 1.5 kDa), and proteins in particular, is highly demanding. So it is no wonder that this issue has attracted significant attention for nearly last two decades, especially in the field of selective chemosensor devising. Despite an extensive research effort in this field, there had been only a limited progress made till the beginning of the present decade. New approaches and new ideas that were proposed in the last few years raised protein imprinting to a completely new level. This progress prompted us to prepare a comprehensive overview of the research accomplished toward devising MIP based chemosensors for selective protein determination.

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.