Graphene as a signal amplifier for preparation of ultrasensitive electrochemical biosensors

Early diagnostics of diseases performed with minimal money and time consumption has become achievable due to recent advances in development of biosensors. These devices use biorecognition elements for selective interaction with an analyte and signal readout is obtained via different types of transducers. Operational characteristics of biosensors have been reported to improve substantially, when a diverse range of nanomaterials was employed. This review presents construction of electrochemical biosensors based on graphene, atomically thin 2D carbon crystals, which is currently intensively studied nanomaterial. The most attractive directions of graphene applications in biosensor preparation are discussed here including novel detection and amplification schemes exploiting graphene’s unique electrochemical, physical and chemical properties. The future of graphene-based biosensors is most likely bright, but there is still a lot of work to do to fulfill high expectations.Slovak scientific grant agency VEGA 2/0162/14 and from the Slovak research and development agency APVV 0282-11 is acknowledged. The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No. 311532 and this work has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 317420. This work was funded by the National Priorities Research Program (Qatar National Research Fund), NPRP 6-381-1-078

Glycoprofiling of cancer biomarkers: Label-free electrochemical lectin-based biosensors

Glycosylation of biomolecules is one of the most prevalent post- and co-translational modification in a human body, with more than half of all human proteins being glycosylated. Malignant transformation of cells influences glycosylation machinery resulting in subtle changes of the glycosylation pattern within the cell populations as a result of cancer. Thus, an altered terminal glycan motif on glycoproteins could provide a warning signal about disease development and progression and could be applied as a reliable biomarker in cancer diagnostics. Among all highly effective glycoprofiling tools, label-free electrochemical impedance spectroscopy (EIS)-based biosensors have emerged as especially suitable tool for point-of-care early-stage cancer detection. Herein, we highlight the current challenges in glycoprofiling of various cancer biomarkers by ultrasensitive impedimetric-based biosensors with low sample consumption, low cost fabrication and simple miniaturization. Additionally, this review provides a short introduction to the field of glycomics and lectinomics and gives a brief overview of glycan alterations in different types of cancer.Slovak research and development agency APVV 0282-11 and VEGA 2/0162/14 is acknowledged. The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Program (FP/2007-2013)/ERC Grant Agreement no 311532 and this work has received funding from the European Union’s Seventh Framework Program for research, technological development and demonstration under grant agreement no 317420.This publication was made possible by NPRP grant # 6-381-1-078 from the Qatar National Research Fund (a member of Qatar Foundation)

Light-controllable viscoelastic properties of a photolabile carboxybetaine ester-based polymer with mucus and cellulose sulfate

In this study, the interaction of a photoswitchable carboxybetaine ester-based polymer with mucus and cellulose sulfate was elucidated, showing light-controllable viscoelastic properties. This polymer contains photolabile o-nitrobenzyl ester moieties, allowing transformation from its polycationic form to a charge-balanced nontoxic polyzwitterionic form upon photolysis by irradiation at 365 nm. Rheological studies revealed that the polycationic form of the polymer interacts with mucus and cellulose sulfate to create a physically crosslinked hydrogel based primarily on polyionic complexation and partially on hydrogen bonding. In these cases, a dramatic change in the rheological synergism was confirmed for mucus-based and cellulose sulfate-based systems. Rheological synergism with the polycationic carboxybetaine ester sample reached nearly 4 and 3.8, while it decreased with the charge-balanced zwitterionic sample to 0.3 and 0.7 after irradiation of the mucus-based and cellulose sulfate-based systems, respectively. Disruption of the interaction during light-induced transformation was on-line monitored and showed a 3 and 3.3 times decrease in the elastic modulus for the mucus-based and cellulose sulfate-based systems, respectively. These properties suggest possible biomedical applications, such as spatially controlled drug release or laparoscopic utilization.Qatar National Research Fund, QNRF; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Qatar University, QU: 7 - 1724 - 3 - 438, QUUG-CAM-2017-

Mussel-mimicking sulfobetaine-based copolymer with metal tunable gelation, self-healing and antibacterial capability

In the present study, the sulfobetaine-based copolymer bearing a dopamine functionality showed gel formation adjusted by the application of metal salts for gelation and various values of pH. Normally, the liquid-like solution of the sulfobetaine-based copolymer and metal cross-linkers is transformed to a gel-like state upon increasing the pH values in the presence of Fe3+ and Ti3+. Metal-induced coordination is reversible by means of the application of EDTA as a chelating agent. In the case of Ag+ ions, the gel is formed through a redox process accompanied with the oxidative coupling of the dopamine moieties and Ag0 particle formation. Mussel-mimicking and metal-dependent viscoelastic properties were observed for Fe3+, Ti3+, and Ag+ cross-linking agents, with additionally enhanced self-healing behavior in comparison with the covalently cross-linked IO4 − analogues. Antibacterial properties can be achieved both in solution and on the surface using the proper concentration of Ag+ ions used for gelation; thus, a tunable amount of the Ag0 particles are formed in the hydrogel. The cytotoxicity was elucidated by the both MTT assay on the NIH/3T3 fibroblast cell line and direct contact method using human dermal fibroblast cell (F121) and shows the non-toxic character of the synthesized copolymer. © 2017 The AuthorsQatar University [QUUG-CAM-2017-1]; Ministry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504]; Maersk Oil R&TC Qatar project; Qatar National Research Fund (Qatar Foundation) [9 - 219-2-105

Polypyrrole nanotubes decorated with gold particles applied for construction of enzymatic bioanodes and biocathodes

The novel composites of gold nanoparticles and polypyrrole nanotubes (Au-x@PNT) were prepared and used as a platform for fabrication of bioelectrode interfaces. Changing the conditions of composite preparation caused variations in a gold architecture, electrical conductivity and a biocompatibility. These features could be easily adjusted by setting up a proper fabrication protocol. The Au-x@PNT-chitosan matrix was utilized for fabrication of bioelectrode interfaces with physisorbed oxidoreductases. Biocatalytic activity of such physisorbed fructose dehydrogenase (FDH), laccase (Lac) and bilirubin oxidase (BOD) was investigated with biocatalytic current density up to j = 2.45 mA cm(-2) obtained for a bioanode based on direct electron transfer of FDH. Performance of biocathodes with immobilized Lac and BOD showed current density up to 232 mu A cm(-2) in presence of a redox mediator.NPRP grant from the Qatar National Research Fund (Qatar Foundation) [6-381-1-078

Nicotinamide-based supergelator self-assembling via asymmetric hydrogen bonding NH⋯OC and H⋯Br− pattern for reusable, moldable and self-healable nontoxic fuel gels

Hypothesis: Development of highly efficient low-molecular weight gelators (LMWGs) for safe energy storage materials is of great demand. Energy storage materials as fuel gels are often achieved by construction of hybrid organic frameworks capable of multiple noncovalent interactions in self-assembly, which allow tuning required properties at the molecular level by altering individual building blocks of the LMWG. However, LMWGs have limited rechargeable capability due to their chemical instability. Experiments: We designed, synthesized and characterized a novel, bio-inspired chiral gemini amphiphile derivative 1 containing N-hexadecyl aliphatic tails from quaternized nicotinamide-based segment and bromide anion showing supergelation ability in water, alcohols, aprotic polar and aromatic solvents, with critical gel concentrations as low as 0.1 and 0.035 wt% in isopropanol and water, respectively. Findings: Nanostructural architecture of the network depended on the solvent used and showed variations in size and shape of 1D nanofibers. Supergelation is attributed to a unique asymmetric NH⋯OC, H⋯Br− hydrogen bonding pattern between H-2 hydrogens from nicotinamide-based segment, amide functional groups from chiral trans-cyclohexane-1,2-diamide-based segment and bromide ions, supporting the intermolecular amide–amide interactions appearing across one strand of the self-assembly. Gels formed from 1 exhibit high stiffness, self-healing, moldable and colorable properties. In addition, isopropanol gels of 1 are attractive as reusable, shape-persistent non-toxic fuels maintaining the chemical structure with gelation efficiency for at least five consecutive burning cycles. © 2021 Elsevier Inc.Chemical Institute, Slovak Academy of Sciences [IRCC-2020004]; Slovak Research and Development AgencySlovak Research and Development Agency [APVV-17-0324]; Ministry of Education of the Slovak Republic [1/0712/18, 1/0145/20]; European Union's Horizon 2020 research and innovation programme [810701]; Ministry of Education, Youth and Sports of the Czech Republic-DKRVO [RP/CPS/2020/003]; Qatar National Library; Qatar University [IRCC-2020004]RP/CPS/2020/003; Univerzita Komenského v Bratislave; Horizon 2020 Framework Programme, H2020: 810701; Slovenská Akadémia Vied, SAV: IRCC-2020-004; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Ministerstvo školstva, vedy, výskumu a športu Slovenskej republiky; Qatar University, QU; Agentúra na Podporu Výskumu a Vývoja, APVV: APVV-17-0324; Vedecká Grantová Agentúra MŠVVaŠ SR a SAV, VEGA: 1/0145/20, 1/0712/18; Horizon 202

Tailoring electrocatalytic properties of Pt nanoparticles grown on Ti3C2Tx MXene surface

In this work, the spontaneous and NaBH4-induced reduction of chloroplatinic acid on the surface of Ti3C2TX MXene was investigated to synthesize a hybrid PtNP-decorated MXene nanomaterial (MX-Pt) with potential as hydrogen evolution (HER) or oxygen reduction reaction (ORR) catalyst properties. The initial Pt concentration, reduction time and presence of additional reducing agents were varied, and as-synthesized nanocomposites were characterized thoroughly by XRD, EDX, SEM and XPS analysis and by electrochemical methods. Composites containing 14 wt% Pt showed HER with an onset potential of -75.9 mV and a current density of -10 mA cm(-2) achieved at -226 mV. The spontaneous deposition of PtNPs on MXene improved the electrocatalytic properties over using an external reducing agent to form PtNP, which was explained based on the different rates of oxidation of Ti in the initial MXene support. Furthermore, good stability of the electrode modified by the MX-Pt was achieved without any polymeric binder and the HER reaction achieved only a negligible decrease over 3 000 potentiodynamic cycles. (C) 2019 The Electrochemical Society.Qatar National Research Fund (a member of The Qatar Foundation) NPRP grant [9-219-2-105

Atom transfer radical polymerization of pyrrole-bearing methacrylate for production of carbonyl iron particles with conducting shell for enhanced electromagnetic hielding

The conducting polymer poly(2-(1H-pyrrole-1-yl)ethyl methacrylate (PPEMA) was synthesized by conventional atom transfer radical polymerization for the first time from free as well as surface-bonded alkyl bromide initiator. When grafted from the surface of carbonyl iron (CI) a substantial conducting shell on the magnetic core was obtained. Synthesis of the monomer as well as its polymer was confirmed using proton spectrum nuclear magnetic resonance (H-1 NMR). Polymers with various molar masses and low dispersity showed the variability of this approach, providing a system with a tailorable structure and brush-like morphology. Successful grafting from the CI surface was elucidate by transmission electron microscopy and Fourier-transform infrared spectroscopy. Very importantly, thanks to the targeted nanometer-scale shell thickness of the PPEMA coating, the magnetization properties of the particles were negligibly affected, as confirmed using vibration sample magnetometry. Smart elastomers (SE) consisting of bare CI or CI grafted with PPEMA chains (CI-PPEMA) and silicone elastomer were prepared and dynamic mechanical properties as well as interference shielding ones were investigated. It was found that short polymer chains grafted to the CI particles exhibited the plasticizing effect, which might be interesting from the magnetorheological point of view, and more interestingly, in comparison to the neat CI-based sample, it provided enhanced electromagnetic shielding of nearly 30 dB in thickness of 500 mu m. Thus, SE containing the newly synthesized CI-PPEMA hybrid particles also exhibited considerably enhanced damping factor and proper mechanical performance, which make the material highly promising from various practical application points of view.Ministry of Education, Youth and Sports of the Czech Republic-DKRVO [RP/CPS/2022/003]; Internal Grant Agency of Tomas Bata University in Zlin [IGA/CPS/2021/003]; Integrated Infrastructure Operational Programme - ERDF [313021T081]; Slovak Research and Development Agency [APVV-19-0338]; Slovak Grant Agency VEGA [2/0129/19]; Qatar University Grant [QUCG-CAM-22/23-504]RP/CPS/2022/003; Slovenská Akadémia Vied, SAV: 313021T081; Tomas Bata University in Zlin, TBU: IGA/CPS/2021/003; Qatar University, QU: QUCG-CAM-22/23-504; Agentúra na Podporu Výskumu a Vývoja, APVV: APVV-19-0338; Vedecká Grantová Agentúra MŠVVaŠ SR a SAV, VEGA: 2/0129/19; European Regional Development Fund, ERD

Switchable Materials Containing Polyzwitterion Moieties

In recent decades, the design and construction of smart materials capable of switching into a polyzwitterionic state by an external trigger have been intensively pursued. Polyzwitterionic states have unique antifouling and surface properties and external triggers, such as pH, light, ions, electric field and CO2, cause significant changes in materials with regard to overall charge, ionic strength and wettability. This survey highlights current progress in the irreversible as well as the reversible switching process involving polyzwitterionic moieties, which can, in turn, be applied to studying the interaction of various interfaces with biological species as protein, DNA, bacteria or platelets and also for advanced use