Carboxybetaine Ester Feature as a Platform for Switchable Surface Properties

A lot of strategies for smart approaches on surfaces were applied such as hydrogel layer, polymer brushes or self-assembly monolayers (SAM). [1] Nowadays switchable zwitterionic materials consisting of molecules with internally balanced charge between positive ammonium and negative carboxy group are promising candidates for this application. [2] They can combine antifouling properties of their zwitterion state and complexation or sticky character in their pre-zwitterionic carboxybetaine ester form. Zwitterionic forms possess antibiofouling properties due to electrostatic interaction between charged moieties, highly hydration capability and overall neutral charge in material as well as biomimetic character because zwitterions are structural similarity to biomembranes. We showed that modifications of surface by zwitterionic based self-assemble monolayer allow enhance detection limit of biosensors down to 10–15 M for analyte, [3,4] or improve electrorheological response. [5] Carboxybetaine esters have cationic character and permit complexation with polyanionic bioabsorbents as well as character of counter ion can adjust wettability and interaction with biomolecules. These studies will present on the utilization of pre-zwiterionic molecules: carboxybetaine based derivates formed from lipoic acid precursor in order to modify surface for construction of impedimetric lectin biosensors and for tuning wettability and interaction with DNA and other charged (bio)molecules. Novel pre-zwitterionic carboxybetaine ester (hydrolysable and photolysable) derivates were synthetized by protocol consists of several synthetic steps and fully characterized. Subsequently, modification of a gold surface was performed by a self-assembled monolayer deposited from a solution containing prezwitterion molecules. Self-assembly monolayer, formed from derivates, was characterized by set instrumentation as atomic force microscopy, quartz crystal microbalance XPS, contact angle etc. Hydrolysable carboxybetaine derivate was able to from complex with polycationic DNA molecules to preconcentrate and release at pH dependent manner. During course of hydrolysis carboxybetaine ester is transferred to carboxybetaine zwitterionic form to promote DNA release due to formation of carboxylate negative charge. Additionally, gradient in wettability can be observed within progress of hydrolysis and present of long perfluorinated or aliphatic types of counter ions. For example switch in wettability can be achieved only by simple and rapid couterion exchange between superhydrophilic (contact angle (CA) below 10° (to very high hydrophobilic (CA over 140°) on rough gold surface. After completed hydrolyses zwitterionic surface can be utilized as a platform for biosensor surface with nonfouling properties. Carboxylic functionality allows immobilizing sensing molecules as lectins for electrochemical impedance spectroscopy by means of EDC/NHS chemistry. This methodology provides opportunity for ultrasensitive detection up to 10–15 M of lectins which may result of a biomarker discovery on several diseases in whole media. Moreover utilization of photolabile ester of carboxybetaine derivates allowing spatially control wettability and pattering with photomask was performed. Photolabile 2-nitrophenyl methyl ester group was introduced to pre-zwitterionic molecule and after irradiation of prepared surface with light at 365 nm was transformed from carboxybetaine ester group to zwitterionic carboxybetaine. Progress of photolysis can be observed by change of surface zeta potential, quartz crystal microbalance and contact angle measurement. This irreversible switch along with different interaction of biological species before and after photolysis will be discussed in this contribution as well. This contribution was made possible by NPRP grant 6-381-1-078 from the Qatar National Research Fund (a member of the Qatar Foundation). The statements contained are entirely the responsibility of the authors.qscienc

Carboxybetaine Modified Interface for Electrochemical Glycoprofiling of Antibodies Isolated from Human Serum

Impedimetric lectin biosensors capable of recognizing two different carbohydrates (galactose and sialic acid) in glycans attached to antibodies isolated from human serum were prepared. The first step entailed the modification of a gold surface by a self-assembled monolayer (SAM) deposited from a solution containing a carboxybetaine-terminated thiol applied to the subsequent covalent immobilization of lectins and to resist nonspecific protein adsorption. In the next step, Sambucus nigra agglutinin (SNA) or Ricinus communis agglutinin (RCA) was covalently attached to the SAM, and the whole process of building a bioreceptive layer was optimized and characterized using a diverse range of techniques including electrochemical impedance spectroscopy, cyclic voltammetry, quartz crystal microbalance, contact angle measurements, zeta-potential assays, X-ray photoelectron spectroscopy, and atomic force microscopy. In addition, the application of the SNA-based lectin biosensor in the glycoprofiling of antibodies isolated from the human sera of healthy individuals and of patients suffering from rheumatoid arthritis (RA) was successfully validated using an SNA-based lectin microarray. The results showed that the SNA lectin, in particular, is capable of discriminating between the antibodies isolated from healthy individuals and those from RA patients based on changes in the amount of sialic acid present in the antibodies. In addition, the results obtained by the application of RCA and SNA biosensors indicate that the abundance of galactose and sialic acid in antibodies isolated from healthy individuals is age-related.Slovak Scientific Grant Agency VEGA 2/0162/14 and from the Slovak Research and Development Agency APVV 0282-11. The European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement no. 311532. This publication was made possible by NPRP grant no. 6-381-1-078 from the Qatar National Research Fund (a member of the Qatar Foundation)

Biocompatible Graphene Oxide With Anchored Zwitterionic Moiety - Synthesis, Characterization And Application

Biocompatible Graphene Oxide with Anchored Zwitterionic Moiety - Synthesis, Characterization and Application Markéta Ilčíková1, Zuzana Kroneková2, Anna Záhoranová2 and Peter Kasák1* 1 Center for Advanced Materials, Qatar University, P.O.Box 2713 Doha, Qatar 2 Polymer Institute, Slovak Academy of Sciences, Dubravska cesta 9, Bratislava, Slovakia *Corresponding author: [email protected] The novel biocompatible graphene oxide (GO) bearing zwitterionic moiety was synthesized and characterized. The zwitterionic structures have recently gained attention in biomedical applications as materials for development of ultra-low fouling surfaces. Generally, zwitterions contain both negative and positive charge in their structures; however the overall charge is neutral. That impart them highly hydrophilic performance; the adsorbed water then prevent the cells or bacteria to interact with surface. Graphene is two dimensional filler interesting predominantly due to high electrical conductivity. In oxidized form the electrical conductivity is compromised due to presence of hydroxyl, epoxy and carboxyl functional groups. In this work, the hydroxyl groups were utilized for anchoring the zwitterionic moiety onto the GO surface. The reaction was performed in two steps. First the silanization with (3-mercaptopropyl)trimethoxysilane was preformed to introduce the thiol functionality onto the GO surface that was reacted with sulfobetaine monomer (3-((2-methacrylamidoethyl)dimethylammonio)propane-1-sulfonate) through thiolene click reaction in the following step. The successful modification was confirmed by FTIR and TGA. Compared to neat graphene, the presence of sulfobetaine improved the graphene biotolerability for fibroblasts and pancreatic beta cells. Modification of GO surface with zwitterionic moiety prevents its negative effect on cell viability. Thus the adsorption of cells on the surface and the cell - GO surface interaction is effected. The modified GO will be used for modification of electrode at biochips construction, and the electrorheological response will be discussed as well.Qscienc

Controllably coated graphene oxide particles with enhanced compatibility with poly(ethylene-co-propylene) thermoplastic elastomer for excellent photo-mechanical actuation capability

This paper reports the utilization of the controllable coating via SI-ATRP technique as a promising approach for controlling stimuli-responsive capabilities of graphene oxide (GO) based nanocomposites. Various polymer brushes with controlled molar mass and narrow dispersity were grown from the surface of GO particles. Modification of GO with poly(methyl methacrylate) and poly(n-butyl methacrylate) was proved by transmission electron microscopy, thermogravimetric analysis with online FTIR recording and finally by X-ray photoelectron spectroscopy (XPS). Densities of GO-based materials were investigated and conductivity measurements showed the increase values. XPS and Raman shift was used to confirm the GO particles reduction. A compatibility of the filler with propylene-based elastomer was elucidated by melt rheology. The light-induced actuation capability was investigated on composite samples to show, that polymer hybrid particles based on GO have better compatibility with the polymer matrix and thus their proper dispersibility was significantly improved. In addition the plasticizing effect of the short polymer grafts present on the GO filler surface has the crucial impact on the matrix stiffness and thus the ability of composite material to reversibly respond to the external light stimulation.Scopu

Foamed phase change materials based on recycled polyethylene/paraffin wax blends

Foamed phase-change materials (FPCMs) were prepared using recycled linear low-density polyethylene (LLDPE) blended with 30 wt.% of paraffin wax (PW) and foamed by 1,1′-azobiscarbamide. The protection of pores’ collapse during foaming process was insured through chemical cross-linking by organic peroxide prior foaming. This work represents one of very few attempts for a preparation of polymeric phase change foams without a use of micro-encapsulated phase change component leading to the enhancement of the real PCM component (PW) within a final product. The porous structure of fabricated foams was analyzed using micro-computed tomography, and direct observation, and reconstruction of the internal structure was investigated. The porosity of FPCMs was about 85–87 vol.% and resulting thermal conductivity 0.054–0.086 W/m·K. Differential Scanning Calorimetry was used to determine the specific enthalpies of melting (22.4–25.1 J/g) what is the latent heat of materials utilized during a heat absorption. A stability of samples during 10 heating/cooling cycles was demonstrated. The phase change changes were also investigated using the dynamic mechanical analysis from 0° to 65 °C during the 10 cycles, and the mechanical stability of the system and phase-change transition were clearly confirmed, as proved by DSC. Leaching test revealed a long-term release of PW (around 7% of its original content) from samples which were long term stored at temperatures over PW melting point. This is the usual problem concerning polymer/wax blends. The most common, industrially feasible solution is a lamination of products, for instance by aluminum foils. Finally, the measurement of the heat flow simulating the real conditions shows that samples containing PW decrease the energy passing through the sample from 68.56 to 34.88 kJ·m−2. In this respect, FPCMs provide very effective double functionality, firstly common thermal insulators, and second, as the heat absorbers acting through melting of the PW and absorbing the excessive thermal energy during melting. This improves the heat protection of buildings and reduces temperature fluctuations within indoor spaces.This work was made possible by NPRP grant No.: 13S-0127-200177 from the Qatar National Research Fund (A Member of the Qatar Foundation). The statements made herein are solely the responsibility of the authors. M.M. and M.I. gratefully acknowledges the Ministry of Education, Youth and Sports of the Czech Republic—DKRVO (RP/CPS/2020/003).Scopu

Modulation of wettability, gradient and adhesion on self-assembled monolayer by counterion exchange and pH

In this study, two quaternary ammonium salts derived from L-lipoic acid were applied for self-assembled monolayers formation on rough structured gold surface. The derivatives differ in functionality since one possesses simple quaternary ammonium group whereas the other one is carboxybetaine ester containing quaternary ammonium group with pH hydrolysable ester group as a pendant. The response of surface wettability to ion exchange between Cl? and perfluorooctanoate, kinetics and gradient wettability were examined by water contact angle measurement and confirmed by X-ray photoelectron spectroscopy. Furthermore, adhesion forces related to applied counterion on the entire surface and after hydrolysis were investigated by atomic force microscopy measurement at nanometer scales. A dramatic change in wettability upon counterion exchange from superhydrophilic for Cl? to very or superhydrophobic for perfluorooctanoate in a repeatable manner was observed for both derivatives. Kinetics of counterion exchanges revealed faster hydration of simple quaternary derivate. The wettability gradient could be designed from superhydrophobic to superhydrophilic either in a reversible manner by simple immersion of the modified surface in a counterion solution modulated by ionic strength or in an irreversible manner for carboxybetaine ester derivate by time-controlled hydrolysis to charge balanced carboxybetaine. 2017 Elsevier Inc.The authors gratefully acknowledge Mr Ahmed Suliman, Gas Processing Center Qatar University, for carrying out the XPS analysis. This publication was supported by Qatar University Grant QUUG-CAM-2017-1 . This publication was made possible by NPRP grant # NPRP-6-381-1-078 and NPRP-9-219-2-105 from the Qatar National Research Fund (member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. Appendix AScopu

Mixed Zwitterion-Based Self-Assembled Monolayer Interface for Impedimetric Glycomic Analyses of Human IgG Samples in an Array Format

An impedimetric lectin biosensor for the detection of changes in the glycan structure of antibodies isolated from human serum is here correlated with the progression of rheumatoid arthritis (RA). The biosensor was built up from a mixed self-assembled monolayer (SAM) on gold consisting of two different thiolated zwitterionic derivatives, carboxybetaine and sulfobetaine, to resist nonspecific interactions. The carboxyl-terminated one was applied also for the covalent immobilization of lectin Ricinus communis agglutinin I (RCA-I). The process of building a bioreceptive layer was optimized and characterized using a diverse range of techniques. Impedimetric assays were integrated on a chip consisting of eight gold working electrodes, which is an important step toward the achievement of a moderate level of multiplexing for the analysis of human serum samples. At the end, the results obtained by the impedimetric analysis of immunoglobulins G (IgGs) isolated from serum samples were compared with those of two other standard bioanalytical methods employing lectins, that is, lectin microarrays (MAs) and enzyme-linked lectin binding assays (ELLBAs). The impedimetric results agreed very well with the DAS28 index (RA disease activity score 28), suggesting that impedimetric assays could be used for the development of a new diagnostic procedure sensitive to glycosylation changes in human IgGs and thus RA progression. 2016 American Chemical Society.Scopu