Electrochemical sensing and imaging of biological samples

Implementation of analytical methods for biological samples (e.g. bacteria or mammalian cells) is of great importance for diagnosis and treatment of various diseases, as well as for environmental monitoring. However, analysing biological samples is a cumbersome task since it requires a high sensitivity and selectivity, a capability to sense dynamic and spatial concentration changes and time-consuming separation strategies. Although several approaches have been proposed to address all these points, there is still room for the exploration and development of new analytical platforms that contribute to the manipulation and understanding of biological systems. The aim of the present thesis is therefore to propose, characterize and implement new analytical tools that can be used for perturbing, sensing and imaging of biological samples such as adherent cancer cells. As a first approach, scanning electrochemical microscopy (SECM) was combined with cell fixations strategies in order to investigate differences between adherent melanoma cells corresponding to various cancer stages. For this purpose, alive, fixed and permeabilized cells were characterized electrochemically and additionally immunostained in order to visualize by SECM the different intracellular distribution of tyrosinase among three melanoma cancer stages. Constant height SECM is widely used for cells investigation, but the intricate cells topography can influence significantly the real probe-substrate distance and thus encumber the interpretation of the obtained experimental data. Applying soft stylus probes in a contact mode could be an alternative to alleviate such a limitation, although it can also introduce damages on the biological samples. Therefore, as the next step the applicability of the soft stylus concept towards the scanning of adherent living cells in a contact mode was investigated. As a result, modified ultra-soft probes were implemented for the successful and damage-free contact mode scanning of adherent melanoma cells. While the most of the SECM experiments with adherent cells have been devoted to the âreadingâ of a biological response, the perturbation of the cell microenvironment through spatially localized electrochemical or chemical reactions is also of high importance. Therefore, the SECM soft stylus concept was extended as a tool for locally altering the microenvironment of few adherent living cells. A re-designed electrochemical push-pull probe was employed for controlling the extracellular space of a small number of adherent cells. Besides SECM, mass-spectrometry (MS) can be also used for cancer cells characterisation. Therefore, in this thesis an intact cell matrix-assisted laser desorption/ionization MS approach was combined with various cell fixation techniques in order to obtain a simple and fast protocol for acquiring the MS fingerprint of cancer cells. As a result, the developed protocol allowed the characterization and differentiation of various melanoma cell lines in a fast and simple manner, which can be important for cancer diagnosis. Finally, the amperometric sensing approach was exported into an inkjet printed multiplexed platform for the monitoring of biological and environmental relevant samples. With this aim, a multiplexed electrochemical sensor device was fabricated by sequential inkjet printing of silver, carbon nanotubes and an insulating layer on a polyimide substrate and coupled to different magnetic beads-based immunoassay formats

Use of Echinoderms and Marine and Terrestrial Plant Materials in the Technology of Mayonnaise Sauce

Sea urchin caviar is a valuable product, as well as a therapeutic and prophylactic agent for cancer, it removes radionuclides from the body, increases the body’s resistance to various types of infections, with physical and mental fatigue, under stress. In addition to the above mentioned aspects, the ingestion of sea urchin caviar helps to increase the human body’s resistance to adverse and harmful environmental factors, and has a positive effect on the cardiovascular system and thyroid function. The gonads of sea urchins contain a set of all amino acids not synthesized by the human body, moreover, in a ratio close to the composition of the “ideal protein”. The technology for manufacturing a new mayonnaise sauce using such valuable ingredients as sea urchin caviar, kelp, and nettle has been scientifically substantiated and created. A prescription composition of a new product has been developed; samples of mayonnaise sauce were made and their study during storage was carried out. The implementation of such a technology will allow not only rational use of stocks of marine non-fish raw materials and plants, but also expand the range and properties of functional products

Bevacizumab biosimilar and reference bevacizumab in subjects with stage IIIB/IV non-squamous non-small cell lung cancer (STELLA): Design of a confirmatory, double-blind, randomized, controlled study

Background: MB02 is a bevacizumab biosimilar developed to stringent guidelines, including non-clinical and preclinical investigations and a clinical trial as first-line treatment in metastatic colorectal cancer (Romera A et al. Lancet Gastroenterol Hepatol 2018;3 (12): 845-855). A clinical trial (STELLA) has been initiated to confirm there are no clinically meaningful differences between MB02 and reference bevacizumab (Avastin) in terms of efficacy, safety, and immunogenicity (NCT03296163). Methods: STELLA study is a multinational, double-blind, randomized, parallel-group, equivalence study comparing the efficacy and safety of MB02 vs reference bevacizumab plus chemotherapy in subjects with stage IIIB/IV non-squamous non-small cell lung cancer (NSCLC)

Aluminium Foil as Single-Use Substrate for MALDI-MS Fingerprinting of Different Melanoma Cell Lines

Herein, we present the intact cell matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for the fingerprinting of human melanoma cancer cell lines grown on aluminium foil. To perform the MALDI-MS assay, melanoma cells were cultured on a flat and thin foil, which was directly transferred to the target plate of MALDI-MS for analysis. The influence of a wide range of cell fixation protocols (i.e. formalin-based and alcohol-based methods) and MALDI matrices on the obtained characteristic spectra was investigated. For the optimization of the MALDI-MS protocol, the MS fingerprints of the melanoma WM-239 cell line with and without an overexpressed enhanced green fluorescent protein were employed. The fingerprints obtained from WM-239 cells grown on aluminum foil were compared with intact cell MALDI of cell pellet and presented higher sensitivity in high m/z range. The optimized protocol was subsequently applied to characterise melanoma cell lines derived from different cancer stages and allowed the identification of unique MS signals that can be used for the differentiation between the studied cell lines (i.e. molecular weight equal to 10.0 kDa and 26.1 kDa)

Analytical Chemistry at the Laboratoire d'Electrochimie Physique et Analytique

The Laboratoire d'Electrochimie Physique et Analytique (LEPA) has moved to the new Energypolis campus in Sion. This laboratory is involved in energy research in particular by studying charge transfer reactions at soft interfaces and developing interfacial redox electrocatalysis, by pioneering the concept of photo-ionic cells and by integrating redox flow batteries for the production of hydrogen at the pilot scale. Nonetheless, this laboratory has a long tradition in analytical chemistry with the development of microfabrication techniques such as laser photo-ablation, screen-printing and more recently inkjet printing for the design and fabrication of biosensors and immunosensors. As shown in the present review, the laboratory has recently pioneered new technologies for electrochemical and mass spectrometry imaging and for the screening of allergy in patients. The role of the laboratory in the Valais landscape will be to foster the collaboration with the HES to develop teaching and research in analytical chemistry as this field is a major source of employment for chemists

Inkjet-printed microtiter plates for portable electrochemical immunoassays

Herein, we present the large-scale fabrication of multiplexed three-electrode sensors used in a point-of-care device platform that couples a magnetic bead-based immunoassay strategy with amperometric detection for rapid and highly sensitive analysis. The multiplexed sensors consisted of eight independent electrochemical cells, each with a carbon nanotube (CNT) working electrode, CNT counter electrode and a silver-silver chloride quasi-reference electrode. The microchips were fabricated on flexible polyethylene terephthalate (PET) sheets by sequential multilayer inkjet printing (IJP) of silver, CNT and insulator inks that were either simultaneously or subsequently post-processed (e.g. through UV photo-polymerization or photonic curing). Finally, plastic wells were mounted on top of the inkjet-printed patterns to obtain an eight-well microtiter plate where each well had a solution capacity of 50 μL. Due to the high precision of the IJP process, the microtiter plates showed high reproducibility among the individual electrochemical cells (1–2% of deviation). Furthermore, the microchips can be reusable for at least up to 20 times as demonstrated herein. In a customized multichannel potentiostat with eight implemented magnets matching the positions of the working electrodes, the electrochemical readout of magnetic bead based sandwich and competitive immunoassays was successfully realized for the detection of thyroid-stimulating hormone (TSH) and atrazine (ATR) in aqueous and urine samples, respectively. The achieved limits of detection for ATR (i.e. 0.01 μg/L) and TSH (i.e. 0.5 μIU/mL) demonstrated the potential of the IJP microtiter plates for the environmental and biological quantification of analytes in a very reliable high throughput platform. This work shows that IJP has certainly reached the status of a batch production tool for electroanalytical sensing platform

Untersuchung der Tyrosinase-Expression in nicht-metastatischen und metastatischen Melanomgeweben durch elektrochemische Rastersondenmikroskopie

Trotz des enormen Fortschritts, der bei der Diagnose von Melanomen erzielt wurde, bleibt die zuverlässige Erkennung der verschiedenen Malignomstadien eine Herausforderung. Derzeitige Strategien setzen auf die optische Erfassung der Konzentration und räumlichen Verteilung spezifischer Biomarker. Neueste optische Methoden können allerdings durch Interferenzen mit Hintergrundfarben und durch Autofluoreszenz beeinflusst werden. Wir bewältigen diese Defizite hier unter Einsatz der elektrochemischen Rastersondenmikroskopie (SECM), um den prognostischen Indikator Tyrosinase (TyR) in nicht-metastatischen und metastatischen Melanomgeweben mithilfe einer weichen Mikroelektrodensonde abzubilden. Das elektrochemische Auslesen der TyR-Verteilung wurde durch das Adaptieren eines immunchemischen Verfahrens ermöglicht. Wir zeigen, dass die SECM die erwähnten Beschränkungen optischer Methoden übertreffen kann und bisher nicht gekannte Möglichkeiten für eine verbesserte Diagnose und das Verständnis der räumlichen Verteilung von TyR in verschiedenen Melanomstadien eröffnet

Electronic band structure of a Tl/Sn atomic sandwich on Si(111)

A two-dimensional compound made of one monolayer of Tl and one monolayer of Sn on Si(111) has been found to have a sandwichlike structure in which the Sn layer (having the milk-stool arrangement) resides on the bulklike terminated Si(111) surface and the Tl layer (having the honeycomb-chained-trimer arrangement) is located above the Sn layer. The electronic band structure of the compound contains two spin-split surface-state bands, of which one is nonmetallic and the other is metallic. Near the Fermi level the metallic band is split with the momentum splitting Δk∥=0.037 Å−1 and energy splitting ΔEF=167 meV. The steep dispersion of the band when crossing the Fermi level corresponds to an electron velocity of ≈8.5×105 m/s, which is comparable to the value reported for graphene. The 2D Fermi contours have almost circular shape with spin texture typical for hexagonal surfaces

Single layer nickel disilicide on surface and as embedded layer

Single monolayers of various materials (e.g. graphene, silicene, bismuthene, plumbene, etc) have recently become fascinating and promising objects in modern condensed-matter physics and nanotechnology. However, growing a monolayer of non-layered material is still challenging. In the present report, it will be shown that single monolayer NiSi2 can be fabricated at Si(111) surface stabilized by either Tl, Pb or In monolayers. Nickel atoms were found to intercalate the stabilizing metal layers upon deposition and to reside in the interstitial sites inside the first silicon bilayer of bulk-like-terminated Si(111)1×1 surface. The interstitial positions almost coincide with the bulk NiSi2 atomic positions thus forming NiSi2 single layer. Atomic and electronic structure of formed systems is described in detail by means of a set of experimental techniques, including low-energy electron diffraction, scanning tunneling microscopy, angle-resolved photoemission spectroscopy and also first-principles density-functional-theory calculations. Quality of formed single monolayer NiSi2 was additionally confirmed by in situ four-probe transport measurements that show that single monolayer NiSi2 preserves a metallic-type conductivity down to 2.0 K. Moreover it was found that delta-type structure with atomic sheet of NiSi2 silicide embedded into a crystalline Si matrix can be fabricated using room-temperature overgrowth of a Si film onto the Tl stabilized NiSi2 surface layer. Confinement of the NiSi2 layer to a single atomic plane has been directly confirmed by high-resolution transmission electron microscopy

Synthesis of two-dimensional TlxBi1-x compounds and Archimedean encoding of their atomic structure

Crystalline atomic layers on solid surfaces are composed of a single building block, unit cell, that is copied and stacked together to form the entire two-dimensional crystal structure. However, it appears that this is not an unique possibility. We report here on synthesis and characterization of the one-atomic-layer-thick TlxBi1−x compounds which display quite a different arrangement. It represents a quasi-periodic tiling structures that are built by a set of tiling elements as building blocks. Though the layer is lacking strict periodicity, it shows up as an ideally-packed tiling of basic elements without any skips or halting. The two-dimensional TlxBi1−x compounds were formed by depositing Bi onto the Tl-covered Si(111) surface where Bi atoms substitute appropriate amount of Tl atoms. Atomic structure of each tiling element as well as arrangement of TlxBi1−x compounds were established in a detail. Electronic properties and spin texture of the selected compounds having periodic structures were characterized. The shown example demonstrates possibility for the formation of the exotic low-dimensional materials via unusual growth mechanisms