Cellulose nanocrystals from grape pomace and their use for the development of starch-based nanocomposite films

Nanocomposite films prepared from starch (ST) in the presence of cellulose nanocrystals (CNCs) was performed using grape pomace as raw material. CNCs were obtained by acid hydrolysis and added to filmogenic solutions (1, 2, 5, 10 and 15 g/100 g of ST). Cellulose, CNCs and Nanocomposites were characterized. Amorphous non-cellulosic materials were removed from the grape pomace presented values for CrI 64% and 71% and yield 12 and 70% in Cellulose and CNCs, respectively. Nanocomposites showed smaller permeability and the addition of 5 to 15% CNCs formed more opaque films and had improved tensile strength and Youngs modulus. The addition of CNCs from 5 to 15% proved to be effective in improving mechanical properties and decreasing water vapor permeability, important characteristics in food packaging materials. This study provided an effective method to obtain CNCs from the agroindustrial waste and open the way to produce high-value starch based nanocomposites.The authors are grateful for financial support provided by FAPERJ - Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro, Brazil (E-26.202749/2018), the National Council for Scientific and Technological Development – CNPq (311936/2018-0), and the Coordenação de Aperfeiçoamento Pessoal do Ensino Superior (CAPES). The support during transmission electron microscopy analyses provided by the LABNANO/CBPF is also very much appreciated.info:eu-repo/semantics/publishedVersio

biosensor applications

A novel ferrocenyldithiophosphonate (TPFc) functionalized monomer and its conductive copolymer were synthesized, characterized and its potential use for biosensor applications was investigated. The structure of copolymer (P(TPFc-co-TPA)) which has free amino and ferrocene (Fc) groups was characterized by various techniques such as NMR and cyclic voltammetry. Afterwards, covalent immobilization of glucose oxidase (GOx) was carried out with glutaraldehyde using the amino groups on both the conducting copolymer and GOx. Fc on the backbone played a role as redox mediator during the electrochemical measurements. Therefore, the proposed copolymer P(TPFc-co-TPA) served as a functional platform for stable biomolecule immobilization and for obtaining the oxygen free mediated electrochemical responses. The current signals were recorded using glucose as substrate, at +0.45 V vs. Ag/AgCl in Na-acetate buffer (pH 4.5; 50 mM). Additionally, K-m(app) (20.23 mM), I-max (3.03 mu A) and sensitivity (0.10 mu A mM(-1) cm(-2)) values were determined. Finally, the biosensor was successfully applied to glucose analysis in various beverages and the results were compared with data obtained from the spectrophotometric glucose detection kit as a reference method

voltammetric sensing of mercury ions in aqueous medium

Herein, we report the synthesis and characterization of a new rhodamine-based monomer (RD-CZ), and an investigation of the optical and electrochemical properties of the corresponding polymer (P(RD-CZ)),which was electropolymerized on an ITO electrode. The resulting P(RD-CZ) polymer film was used as a simple and novel multi-signal sensor platform, which demonstrates ion-selective potentiometric, colori-metric and voltammetric responses in aqueous media for the first time. P(RD-CZ) exhibits excellent selectivity for Hg2+ ions compared with Cd2+, Cu2+ Zn2+, and Fe3+ using the potentiometric technique, which depends on the increasing charge carrier transport through rhodamine-bound Hg2+ with a limit of detection (LOD) of 9.77 x 10(-8) M. The P(RD-CZ) polymer film also exhibits a distinct color change from orange to purple, which is detectable even by the naked eye, in the presence of Hg2+ ions. The LOD for Hg2+ ions obtained using the colorimetric method is 3.16 x 10(-8) M. The same material has also been used for the voltammetric sensing of Hg2+ in aqueous media with a detection limit of 1 x 10(-7) M. In this study, a conductive polymer-based sensor platform for detecting mercury ions via three different methods has been designed for the first time. By doing so, a disposable planar paper-based ion-sensing platform, which is suitable for low-cost point-of-care and in-field testing applications, could be fabricated with a highly reproducible and linear response towards different concentrations of analyte ions in aqueous and biological samples

Conducting Polymer-Based Electrochemical Biosensors

Herein, we report a novel ferrocenyldithiophosphonate functional conducting polymer and its use as an immobilization matrix in amperometric biosensor applications. Initially, 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)amidoferrocenyldithiophosphonate was synthesized and copolymerized with 4-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzenamine at graphite electrodes. The amino groups on the polymer were utilized for covalent attachment of the enzyme glucose oxidase. Besides, ferrocene on the backbone was used as a redox mediator during the electrochemical measurements. Prior to the analytical characterization, optimization studies were carried out. The changes in current signals at +0.45 V were proportional to glucose concentration from 0.5 to 5.0 mM. Finally, the resulting biosensor was applied for glucose analysis in real samples and the data were compared with the spectrophotometric Trinder method

Rhodamine-based conjugated polymers: potentiometric, colorimetric and voltammetric sensing of mercury ions in aqueous medium.

Herein, we report the synthesis and characterization of a new rhodamine-based monomer (RD-CZ), and an investigation of the optical and electrochemical properties of the corresponding polymer (P(RD-CZ)), which was electropolymerized on an ITO electrode. The resulting P(RD-CZ) polymer film was used as a simple and novel multi-signal sensor platform, which demonstrates ion-selective potentiometric, colorimetric and voltammetric responses in aqueous media for the first time. P(RD-CZ) exhibits excellent selectivity for Hg(2+) ions compared with Cd(2+), Cu(2+) Zn(2+), and Fe(3+) using the potentiometric technique, which depends on the increasing charge carrier transport through rhodamine-bound Hg(2+) with a limit of detection (LOD) of 9.77 × 10(-8) M. The P(RD-CZ) polymer film also exhibits a distinct color change from orange to purple, which is detectable even by the naked eye, in the presence of Hg(2+) ions. The LOD for Hg(2+) ions obtained using the colorimetric method is 3.16 × 10(-8) M. The same material has also been used for the voltammetric sensing of Hg(2+) in aqueous media with a detection limit of 1 × 10(-7) M. In this study, a conductive polymer-based sensor platform for detecting mercury ions via three different methods has been designed for the first time. By doing so, a disposable planar paper-based ion-sensing platform, which is suitable for low-cost point-of-care and in-field testing applications, could be fabricated with a highly reproducible and linear response towards different concentrations of analyte ions in aqueous and biological samples

A novel functional conducting polymer as an immobilization platform

Here, we present the fabrication of conducting polymer based enzymatic and microbial biosensors. To obtain immobilization platforms for both pyranose oxidase (PyOx) and Gluconobacter oxydans, the graphite electrode surface was modified with the polymer of 4-amino-N-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzamide (HKCN) which has free amino groups on the surface for further bioconjugation reactions with the biomolecules. Initially, the electrode surface was covered with HKCN via electropolymerization. Then, either PyOx or G. oxydans cell was stabilized using glutaraldehyde as a cross-linker. After optimization of biosensors, analytical characterization and surface imaging studies were investigated. The change of current depends on glucose concentration between 0.05-1.0 mM and 0.25-2.5 mM with HKCN/PyOx and HKCN/G. oxydans biosensors in batch systems. Also, the calibration graphs were obtained for glucose in FIA mode, and in this case, linear ranges were found to be 0.01-1.0 mM and 0.1-7.5 mM for HKCN/PyOx and HKCN/G. oxydans, respectively. (C) 2014 Elsevier B.V. All rights reserved

electrochemical sensing and fluorescence imaging of cells

We report here the electrochemical co-polymerization of two functional monomers, one containing fluorescent rhodamine dye (RF) and the other monomer having amine groups (RD), onto electroactive Indium Tin Oxide (ITO) glass. After one step preparation of these surfaces, a three peptide called ArginylGlysylAspartic acid (RGD) was immobilized via EDC chemistry by using amine groups (P(RF-co-RD)/RGD) of the co-polymer, for further use in various bio-applications such as cell adhesion and imaging as well as electrochemical cell sensing. The resultant RGD bound and also fluorescent platforms were utilized as targeted adhesion materials towards integrin avb3 receptor positive (U87-MG) cells and the selectivity was checked by using HaCaT cells as a control. Finally, electrochemical measurements were carried out to characterize step by step surface modification and detection of cell attachment. As a result, P(RF-co-RD)/RGD is a promising material for multi-purpose uses, such as fluorescence imaging without the need for an additional dye for cell visualization and as a targeted adhesion and electrochemical cell sensing platform

Copolymer based multifunctional conducting polymer film for fluorescence sensing of glucose.

A simple, rapid and effective fluorescence sensing platform has been fabricated using a fluorescent conducting polymer surface. For this purpose, a rhodamine based electroactive monomer (RDC) and a functional group containing monomer (SNS) have been copolymerized to develop a conducting polymer based sensor platform having a fluorescence and enzyme-binding surface on ITO electrode. The proposed fluorescence sensing mechanism for detection of glucose is related to the consumption of dissolved oxygen at the double layer of the electrode which is fluorescence quenching agent by glucose-GOx reaction. Concentration of glucose was investigated quantitatively from 0.05 to 1 mM via fluorescence signal measurement. This novel approach could be adapted for the production of various rapid and effective fluorescence sensing platforms for glucose

A novel functional conducting polymer as an immobilization platform.

Here, we present the fabrication of conducting polymer based enzymatic and microbial biosensors. To obtain immobilization platforms for both pyranose oxidase (PyOx) and Gluconobacter oxydans, the graphite electrode surface was modified with the polymer of 4-amino-N-(2,5-di(thiophen-2-yl)-1H-pyrrol-1-yl)benzamide (HKCN) which has free amino groups on the surface for further bioconjugation reactions with the biomolecules. Initially, the electrode surface was covered with HKCN via electropolymerization. Then, either PyOx or G. oxydans cell was stabilized using glutaraldehyde as a cross-linker. After optimization of biosensors, analytical characterization and surface imaging studies were investigated. The change of current depends on glucose concentration between 0.05-1.0mM and 0.25-2.5mM with HKCN/PyOx and HKCN/G. oxydans biosensors in batch systems. Also, the calibration graphs were obtained for glucose in FIA mode, and in this case, linear ranges were found to be 0.01-1.0mM and 0.1-7.5mM for HKCN/PyOx and HKCN/G. oxydans, respectively