STRATEGIES FOR PREPARATION OF MOLECULARLY IMPRINTED POLYMERS MODIFIED ELECTRODES AND THEIR APPLICATION IN ELECTROANALYSIS: A REVIEW

Molecularly imprinted polymers (MIP's) have been applied in several areas of analytical chemistry, including the modification of electrodes. The main purpose of such modification is improving selectivity; however, a gain in sensitivity was also observed in many cases. The most frequent approaches for these modifications are the electrodeposition of polymer films and sol gel deposits, spin and drop coating and self-assembling of films on metal nanoparticles. The preparation of bulk (body) modified composites as carbon pastes and polymer agglutinated graphite have also been investigated. In all cases several analytes including pharmaceuticals, pesticides, and inorganic species, as well as molecules with biological relevance have been successfully used as templates and analyzed with such devices in electroanalytical procedures. Herein, 65 references are presented concerning the general characteristics and some details related to the preparation of MIP's including a description of electrodes modified with MIP's by different approaches. The results using voltammetric and amperometric detection are described.

Determination of Tetracycline in Environmental Water Samples at a Graphite-Polyurethane Composite Electrode

A bare graphite-polyurethane composite was evaluated in the tetracycline (TC) determination in natural water samples. Using differential pulse voltammetry (DPV), a linear response was observed in the range of 4.00-40.0 mu mol L-1 with limit of detection of 2.80 mu mol L-1, without the need of surface renewing between successive runs. During the tetracycline determination in water samples, recoveries between 92.6 and 100% were found. The results for TC determination in water samples after a pre-concentration stage agreed with spiked value at a 95% confidence level according to student t-test.

Performance of an electronic tongue during monitoring 2-rnethylisoborneol and geosmin in water samples

2-Methylisoborneol (MIB) and geosmin (GSM) are sub products from algae decomposition and, depending on their concentration, can be toxic: otherwise, they give unpleasant taste and odor to water. For water treatment companies it is important to constantly monitor their presence in the distributed water and avoid further costumer complaints. Lower-cost and easy-to-read instrumentation would be very promising in this regard. In this study, we evaluate the potentiality of an electronic tongue (ET) system based on non-specific polymeric sensors and impedance measurements in monitoring MIB and GSM in water samples. Principal component analysis (PCA) applied to the generated data matrix indicated that this ET was capable to perform with remarkable reproducibility the discrimination of these two contaminants in either distilled or tap water, in concentrations as low as 25 ng L-1. Nonetheless, this analysis methodology was rather qualitative and laborious, and the outputs it provided were greatly subjective. Also, data analysis based on PCA severely restricts automation of the measuring system or its use by non-specialized operators. To circumvent these drawbacks, a fuzzy controller was designed to quantitatively perform sample classification while providing outputs in simpler data charts. For instance, the ET along with the referred fuzzy controller performed with a 100% hit rate the quantification of MIB and GSM samples in distilled and tap water. The hit rate could be read directly from the plot. The lower cost of these polymeric sensors allied to the especial features of the fuzzy controller (easiness on programming and numerical outputs) provided initial requirements for developing an automated ET system to monitor odorant species in water production and distribution. (C) 2012 Elsevier B.V. All rights reserved.

Charge generation, charge transport, and residual charge in the electrospinning of polymers: A review of issues and complications

Electrospinning has become a widely implemented technique for the generation of nonwoven mats that are useful in tissue engineering and filter applications. The overriding factor that has contributed to the popularity of this method is the ease with which fibers with submicron diameters can be produced. Fibers on that size scale are comparable to protein filaments that are observed in the extracellular matrix. The apparatus and procedures for conducting electrospinning experiments are ostensibly simple. While it is rarely reported in the literature on this topic, any experience with this method of fiber spinning reveals substantial ambiguities in how the process can be controlled to generate reproducible results. The simplicity of the procedure belies the complexity of the physical processes that determine the electrospinning process dynamics. In this article, three process domains and the physical domain of charge interaction are identified as important in electrospinning: (a) creation of charge carriers, (b) charge transport, (c) residual charge. The initial event that enables electrospinning is the generation of region of excess charge in the fluid that is to be electrospun. The electrostatic forces that develop on this region of charged fluid in the presence of a high potential result in the ejection of a fluid jet that solidifies into the resulting fiber. The transport of charge from the charge solution to the grounded collection device produces some of the current which is observed. That transport can occur by the fluid jet and through the atmosphere surrounding the electrospinning apparatus. Charges that are created in the fluid that are not dissipated remain in the solidified fiber as residual charges. The physics of each of these domains in the electrospinning process is summarized in terms of the current understanding, and possible sources of ambiguity in the implementation of this technique are indicated. Directions for future research to further articulate the behavior of the electrospinning process are suggested. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3682464]

Hb S-Sao Paulo: A new sickling hemoglobin with stable polymers and decreased oxygen affinity

Hb S-Sao Paulo (SP) [HBB:c.20A > T p.Glu6Val: c.196A > G p.Lys65Glu] is a new double-mutant hemoglobin that was found in heterozygosis in an 18-month-old Brazilian male with moderate anemia. It behaves like Hb S in acid electrophoresis, isoelectric focusing and solubility testing but shows different behavior in alkaline electrophoresis, cation-exchange HPLC and RP-HPLC. The variant is slightly unstable, showed reduced oxygen affinity and also appeared to form polymers more stable than the Hb S. Molecular dynamics simulation suggests that the polymerization is favored by interfacial electrostatic interactions. This provides a plausible explanation for some of the reported experimental observations. (C) 2012 Elsevier Inc. All rights reserved.

Binary and ternary inclusion complexes of dapsone in cyclodextrins and polymers: preparation, characterization and evaluation

Dapsone (DAP) is a synthetic sulfone drug with bacteriostatic activity, mainly against Mycobacterium leprae. In this study we have investigated the interactions of DAP with cyclodextrins, 2-hydroxypropyl-beta-cyclodextrin (HP beta CD) and beta-cyclodextrin (beta CD), in the presence and absence of water-soluble polymers, in order to improve its solubility and bioavailability. Solid systems DAP/HP beta CD and DAP/beta CD, in the presence or absence of polyvinylpyrrolidone (PVP K30) or hydroxypropyl methylcellulose (HPMC), were prepared. The binary and ternary systems were evaluated and characterized by SEM, DSC, XRD and NMR analysis as well as phase solubility assays, in order to investigate the interactions between DAP and the excipients in aqueous solution. This study revealed that inclusion complexes of DAP and cyclodextrins (HP beta CD and beta CD) can be produced in order to improve DAP solubility and bioavailability in the presence or absence of polymers (PVP K30 and HPMC). The more stable inclusion complex was obtained with HP beta CD, and consequently HP beta CD was more efficient in improving DAP solubility than beta CD, and the addition of polymers had no influence on DAP solubility or on the stability of the DAP/CDs complexes.

Late clinical outcomes after implantation of drug-eluting stents coated with biodegradable polymers: 3-year follow-up of the PAINT randomised trial

Aims: The long-term clinical performance of drug-eluting stents (DES) coated with biodegradable polymers is poorly known. Methods and results: A total of 274 coronary patients were randomly allocated to paclitaxel-eluting stents, sirolimus-eluting stents, or bare metal stems (2:2:1 ratio). The two DES used the same biodegradable polymers and were identical except for the drug. At three years, the pooled DES population had similar rates of cardiac death or myocardial infarction (9.0% vs. 7.1; p=0.6), but lower risk of repeat interventions (10.0% vs. 29.9%; p<0.01) than controls with bare stents. The cumulative 3-year incidence of definite or probable stent thrombosis in the pooled DES group was 2.3% (first year: 1.8%; second year: 0.4%; third year: zero). There were no significant differences in outcomes between paclitaxel- and sirolimus-eluting stents. Conclusions: The biodegradable-polymer coated DES releasing either paclitaxel or sirolimus were effective in reducing the 3-year rate of re-interventions.

Classification of polymers insulators hydrophobicity basead on digital image processing

Although the hydrophobicity is usually an arduous parameter to be determined in the field, it has been pointed out as a good option to monitor aging of polymeric outdoor insulators. Concerning this purpose, digital image processing of photos taken from wet insulators has been the main technique nowadays. However, important challenges on this technique still remain to be overcome, such as; images from non-controlled illumination conditions can interfere on analyses and no existence of standard surfaces with different levels of hydrophobicity. In this paper, the photo image samples were digitally filtered to reduce the illumination influence, and hydrophobic surface samples were prepared from wetting silicon surfaces with solution of water-alcohol. Furthermore norevious studies triying to quantify and relate these properties in a mathematical function were found, that could be used in the field by the electrical companies. Based on such considerations, high quality images of countless hydrophobic surfaces were obtained and three different image processing methodologies, the fractal dimension and two Haralick textures descriptors, entropy and homogeneity, associated with several digital filters, were compared. The entropy parameter Haralick's descriptors filtered with the White Top-Hat filter presented the best result to classify the hydrophobicity.

Optical storage in azobenzene-containing epoxy polymers processed as Langmuir Blodgett films

In this study, azocopolymers containing different main-chain segments have been synthesized with diglycidyl ether of bisphenol A (DGEBA, DER 332, n=0.03) and the azochromophore Disperse Orange 3 (DO3) cured with twomonoamines, viz. benzylamine (BA) and m-toluidine (MT). The photoinduced birefringence was investigated in films produced with these azopolymers using the spin coating (SC) and Langmuir Blodgett (LB) techniques. In the LB films, birefringence increased with the content of azochromophore and the film thickness, as expected. The nanostructured nature of the LB films led to an enhanced birefringence and faster dynamics in the writing process, compared to the SC films. In summary, the combination of azocopolymers and the LBmethod may allow materials with tuned properties for various optical applications, including in biological systems were photoisomerization may be used to trigger actions such as drug delivery.