Browsing by Author "Peltola, Emilia"

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Adsorption of 17-βbeta-estradiol on Pristine Graphene - A First-principles Structure Search Study
(2024-09-05) Sippola, Saara
School of Electrical Engineering | Master's thesis
17-beta-estradiol (E2) is a steroid hormone that has widespread impacts on the human body and the environment. Currently, the gold standard for its measurement is a conventional blood test coupled with mass spectrometry. Electrochemical sensing has been proposed as an alternative that would enable continuous measurement of E2 sensitively and selectively. Possible application areas include clinical trials, fertility monitoring, and water purification. In this Thesis, I studied the adsorption of E2 on pristine graphene computationally using density-functional theory. There were two objectives to the work: 1) to determine any stable and unique adsorption configurations of E2 on graphene, and 2) analyse the found structures to determine, whether the nature of adsorption was physical or chemical by detecting the presence of any chemical bonds. In order to fulfill the first objective, I employed Bayesian Optimization Structure Search (BOSS) to reduce the human bias that is otherwise involved in the selection of adsorption configuration candidates. As a result, I detected two unique adsorption configurations of E2 on pristine graphene. Analysis of their electronic structure revealed that both structures physisorb on graphene. This study is a preliminary step towards understanding the atomic-scale interactions involved in the adsorption process. In the future, this work could be expanded by considering the effects of environmental parameters, such as solvation and electrode potential, to the adsorption process. More realistic simulations could support and accelerate experimental sensor development.
Biofouling affects the redox kinetics of outer and inner sphere probes on carbon surfaces drastically differently - implications to biosensing
(2020-08-07) Peltola, Emilia; Aarva, Anja; Sainio, Sami; Heikkinen, Joonas J.; Wester, Niklas; Jokinen, Ville; Koskinen, Jari; Laurila, Tomi
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Biofouling imposes a significant threat for sensing probes used in vivo. Antifouling strategies commonly utilize a protective layer on top of the electrode but this may compromise performance of the electrode. Here, we investigated the effect of surface topography and chemistry on fouling without additional protective layers. We have utilized two different carbon materials; tetrahedral amorphous carbon (ta-C) and SU-8 based pyrolytic carbon (PyC) in their typical smooth thin film structure as well as with a nanopillar topography templated from black silicon. The near edge X-ray absorption fine structure (NEXAFS) spectrum revealed striking differences in chemical functionalities of the surfaces. PyC contained equal amounts of ketone, hydroxyl and ether/epoxide groups, while ta-C contained significant amounts of carbonyl groups. Overall, oxygen functionalities were significantly increased on nanograss surfaces compared to the flat counterparts. Neither bovine serum albumin (BSA) or fetal bovine serum (FBS) fouling caused major effects on electron transfer kinetics of outer sphere redox (OSR) probe Ru(NH3)63+ on any of the materials. In contrast, negatively charged OSR probe IrCl62- kinetics were clearly affected by fouling, possibly due to the electrostatic repulsion between redox species and the anionically-charged proteins adsorbed on the electrode and/or stronger interaction of the proteins and positively charged surface. The OSR probe kinetics were less affected by fouling on PyC, probably due to conformational changes of proteins on the surface. Dopamine (DA) was tested as an inner sphere redox (ISR) probe and as expected, the kinetics were heavily dependent on the material; PyC had very fast electron transfer kinetics, while ta-C had sluggish kinetics. DA electron transfer kinetics were heavily affected on all surfaces by fouling (ΔEp increase 30-451%). The effect was stronger on PyC, possibly due to the more strongly adhered protein layer limiting the access of the probe to the inner sphere.
Biolikaantuminen dopamiinia mittaavilla hiilielektrodeilla
(2021-05-14) Heinolainen, Anni
Sähkötekniikan korkeakoulu | Bachelor's thesis
Carbon nanomaterials interfacing with neurons
(2019-09-30) Muukkonen, Maarit
Perustieteiden korkeakoulu | Master's thesis
Chemically reduced graphene oxide in electrochemical sensing for bioapplications
(2016-10-31) Wahlström, Janessa
Sähkötekniikan korkeakoulu | Master's thesis
Electrochemical sensing with voltammetric methods are based on measuring the current induced by an applied potential with an electrode. The current originates from oxidizing or reducing analytes and is related to the concentration of the analyte, which can be almost any ion or molecule found from human body. Neurotransmitters such as dopamine and serotonin, the main interfering compounds, ascorbic acid and uric acid as well as glucose and $\beta$-nicotinamide adenine dinucleotide are important analytes for medical purposes. Graphene has high electrical conductivity, mechanical strength and surface area, which makes it a suitable electrode material. A simple mass production method is to chemically reduce oxidized graphene. Chemically reduced graphene oxide contains structural defects and oxygen bearing functional groups, which enhances the electrochemical properties. Large surface area provides a platform for surface functionalization, which results in large amount of electroactive sites. The surface of chemically reduced graphene oxide can be covered with metallic nanoparticles, nanostructures or recognition elements, which increases selectivity and sensitivity. Especially bimetallic nanostructures are widely used and are concidered more stabile than $e.g.$ enzymes. Nanoparticles or nanostructures can be immobilized on the surface of chemically reduced graphene oxide with stabilizing layers, which also prevent them from aggregating, since aggregation of nanoparticles results in lower surface area and thus lower electrochemical responce. Comparison of different chemically reduced graphene oxide sensors based on published research is problematic due to the wide variety of oxidizing methods, reductants, scan rates, solution pH, reference electrodes, substrate electrodes and stabilizers, which all affect the electrochemical responce. This is why a comparative study should be conducted in order to evaluate the effectiveness of different surface functionalization methods.
Development of Medical Abrasives: For Skin Applications
(2020-04-27) Björkman, Cecilia
Perustieteiden korkeakoulu | Master's thesis
Differentiation of Human Mesenchymal Stem Cells into Dopaminergic Neurons on Brain Electrode Materials
(2016-08-24) Mynttinen, Elsi
Sähkötekniikan korkeakoulu | Master's thesis
Mesenchymal stem cells (MSCs) are multipotent cells that can differentiate into various cell types depending on their environment, but cannot undergo neurogenesis in normal conditions. In contrast, with the appropriate chemical and mechanical stimuli, these cells can be guided towards the neuronal lineage in vitro. Moreover, the generated neurons can be further directed into a dopaminergic (DA) subgroup. This process, however, requires optimal growth conditions, as well as suitable substrates for controlling the cell fate. In this thesis work, human MSCs (hMSCs) were differentiated into DA neurons on four different carbon-based materials and the differentiation process with and without differentiation factors was assessed by following markers related to neurogenesis. The substrate materials were tetrahedral amorphous carbon (ta-C), ta-C coated with poly-D-lysine (PDL), ta-C coated with carbon nanodiamonds (vox) and vox functionalized with brain-derived neurotrophic factor (BDNF). The differentiation medium was a cocktail of BDNF, sonic hedgehog (Shh) and fibroblast growth factors (FGF2 and FGF8). The expressions of glial fibrillary acidic protein (GFAP), nestin, neuron-specific enolase (NSE) and thyrosine hydroxylase (TH) were tracked by immunofluorescence staining and quantitative real-time polymerase chain reaction (RT-qPCR). The results showed the ability of the differentiation medium to induce neuron-like morphology in the cells cultured for 12 days on all material types. In addition, the marker profiles revealed a positive effect of the nanostructures on the MSC differentiation, while PDL coating was found unfavorable for MSCs. Furthermore, the results also indicate that the differentiation process had not been fully completed by the day 12, implying a need for a longer period in culture. These experiments demonstrate various challenges related to developing an efficient protocol for DA differentiation from hMSCs, the most important being the optimization of the combined mechanical and chemical stimuli. Nevertheless, the use of MSCs holds great promise for therapeutic approaches in several medical conditions including spinal cord injuries and neurodegenerative disorders such as Parkinson’s disease.
Effect of substrate mechanical properties on neural cell mechanics
(2020-01-21) Rantataro, Samuel
Kemian tekniikan korkeakoulu | Master's thesis
While an animal body contains a wide range of tissue types, most cells are subjected only to soft environments in vivo, neural cells in particular. Living cells are however able to sense mechanical properties of their surroundings, which plays an essential role in regulating cell behavior. Acknowledging this mechanosensory nature of cells is becoming ever more important in making accurate cell/organ models or treating various pathologies with implants. While soft materials are readily available, they usually lack the functionalities necessary in sensing electrical or chemical signals from the cells. Thus, mechanical biocompatibility of the typically used functional materials must be assessed. Atomic force microscopy was used in this study to measure elasticity of living cells on various materials with different mechanical properties, including vertically aligned carbon nanofibers. Two neural cell lines, PC-12 Adh and C6, were found to show similar level of cytoskeletal strengthening on both soft hydrogel and carbon nanofibers, indicating both samples appearing soft from the cellular perspective. Intriguingly, carbon nanofibers are also known to be both electrically and electrochemically active functional materials. The results obtained here provide an early indication for mechanical biocompatibility of vertically aligned carbon nanofibers, further supporting their use as a sensory material for measuring the behavior of neural cells.
Effects of Biofouling on Carbon Nanofiber -Based Dopamine Sensors
(2020-01-20) Luukinen, Mikko
Perustieteiden korkeakoulu | Master's thesis
Researchers in the Microsystems Technology research group have developed a hybrid material of carbon nanofibers (CNF) grown on tetrahedral amorphous carbon (ta-C). This material has been found suitable for electrodes used in detecting dopamine (DA) with cyclic voltammetry. The effects of biofouling on the ta-C + CNF electrodes were studied in this thesis. Cyclic voltammetry experiments for measuring DA, hexaammineruthenium and hexachloroiridate were performed before and after fouling the electrode surface with bovine serum albumin or fetal bovine serum. The effects were compared between ta-C + CNF samples grown with different parameters. The ta-C + CNF hybrid material was found to be relatively resistant to biofouling. It was also found that growing the material in a higher temperature with a thicker layer of nickel catalyst particles may further enhance this resistance.
The Effects of Surface Properties on Protein Adsorption
(2018-05-11) Messo, Maikki
Sähkötekniikan korkeakoulu | Bachelor's thesis
Fabrication of micro- and nanopillars from pyrolytic carbon and tetrahedral amorphous carbon
(2019-08-01) Heikkinen, Joonas J.; Peltola, Emilia; Wester, Niklas; Koskinen, Jari; Laurila, Tomi; Franssila, Sami; Jokinen, Ville
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Pattern formation of pyrolyzed carbon (PyC) and tetrahedral amorphous carbon (ta-C) thin films were investigated at micro- and nanoscale. Micro- and nanopillars were fabricated from both materials, and their biocompatibility was studied with cell viability tests. Carbon materials are known to be very challenging to pattern. Here we demonstrate two approaches to create biocompatible carbon features. The microtopographies were 2 μm or 20 μm pillars (1:1 aspect ratio) with three different pillar layouts (square-grid, hexa-grid, or random-grid orientation). The nanoscale topography consisted of random nanopillars fabricated by maskless anisotropic etching. The PyC structures were fabricated with photolithography and embossing techniques in SU-8 photopolymer which was pyrolyzed in an inert atmosphere. The ta-C is a thin film coating, and the structures for it were fabricated on silicon substrates. Despite different fabrication methods, both materials were formed into comparable micro- and nanostructures. Mouse neural stem cells were cultured on the samples (without any coatings) and their viability was evaluated with colorimetric viability assay. All samples expressed good biocompatibility, but the topography has only a minor effect on viability. Two μm pillars in ta-C shows increased cell count and aggregation compared to planar ta-C reference sample. The presented materials and fabrication techniques are well suited for applications that require carbon chemistry and benefit from large surface area and topography, such as electrophysiological and -chemical sensors for in vivo and in vitro measurements.
Feasibility of SU-8 photoresist derived pyrolytic carbon for neurotransmitter measurement in biosensing applications
(2016-10-31) Sovanto, Katariina
Sähkötekniikan korkeakoulu | Master's thesis
The biggest challenges in electrochemical detection of dopamine are the complexity of biological liquids, as well as the low and brief concentrations of dopamine in vivo. Within biological liquids there are multiple molecules which might interfere with dopamine detection. One of the major ones is ascorbic acid, which exists in the human brain in much higher concentrations than dopamine does. The oxidation peaks for the two materials tend to overlap on carbon materials. All in all, the electrode material needs to be both selective and sensitive towards dopamine. The purpose of this work is to evaluate the feasibility of SU-8 photoresist derived pyrolytic carbon for detecting dopamine in vivo. The fabrication process was found to result in extremely smooth, nanographitic surfaces with excellent conductivity. The material was characterized electrochemically using cyclic voltammetry. Rapid outer sphere reactions were measured in a FcMeOH solution indicated fast electron transfer and near reversible reactions for films fabricated at 800 – 900 °C. 500 nM DA concentration was the lowest in which dopamine was clearly detected. Separation for the oxidation peaks of dopamine and ascorbic acid could not be achieved in realistic concentrations, but some improvement in the peak shapes was achieved both after anodization and after oxygen plasma treatment of the electrodes. Dopamine was also detected successfully in cell culture media with an electrode, which was not treated with oxygen plasma. Oxygen plasma treatment made the electrode surface sensitive towards electroactive reagents within the cell culture media. Biocompatibility is considered separately for each tissue type. For neural sensing applications, extremely good biocompatibility with neural tissue is required. The electrode surface cannot be allowed to be encapsulated or fouled, as that might lead to electrochemical insulation from the target tissue. The material should be able to support growth, proliferation and neuronal differentiation cells. No cytotoxic effects were discovered on the SU-8 derived pyrolytic carbon, when mouse neural stem cells were seeded. The viability detected was about equal to the cellular viability on tetrahedral amorphous carbon. Oxygen plasma treatment of the pyrolytic carbon surface significantly increased cell viability. Cellular differentiation to neurons could not be induced despite treatment with poly-L-lysine, oxygen plasma, growth factor and differentiation factor.
Hermosoluerilaistumisen ohjaus biomateriaalien avulla
(2015-08-27) Lehtinen, Ilona
Sähkötekniikan korkeakoulu | Bachelor's thesis
Hermosoluerilaistumisen ohjaus sähkömagneettisella stimulaatiolla
(2015-08-28) Vekuri, Henriikka
Sähkötekniikan korkeakoulu | Bachelor's thesis
Hermoston välittäjäaineiden sähkökemiallinen mittaus
(2021-05-03) Pellinen, Heini
Sähkötekniikan korkeakoulu | Bachelor's thesis
Hiilipintojen biolikaantuminen
(2019-08-28) Viitala, Emmi
Sähkötekniikan korkeakoulu | Bachelor's thesis
Hybrid Carbon Nanostructures for Direct Neuronal Interfacing
(2019-08-21) Peltola, Emilia
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
We have developed a concept of hybrid carbon nanomaterials, where different allotropes of carbon are integrated into a structure. In order to facilitate the long-term measurements in vivo, the cellular response at the bioelectric interface should be optimized. Indeed, failure of implant integration has been proposed to be the main reason for sensor failure in vivo. Most strategies to enhance electrode integration into target tissue exploit a protective layer or barrier on an electrode substrate. For the detection of neurotransmitters, this is not as suitable strategy, because (1) such films give rise to an increased background electrode capacitance and impedance, and (2) act as a diffusion barrier and as a result, a decreased amount of the analyte reaches the electrode surface and the kinetics is compromised. Here we demonstrate that we can regulate the cellular response just with the electrode material. Specifically, we will show that it is possible to combine the properties of different carbon allotropes to obtain hybrid materials with enhanced neural response. We will present three examples of the approach: (i) functionalized nanodiamonds on tetrahedral amorphous carbon (ta-C), (ii) multi-walled carbon nanotubes grown directly on top of to-C, and (iii) carbon nanofibres synthesized on top of ta-C thin films. We demonstrate that hybrid structures may promote neural integration as, for example, hydrogen-terminated nanodiamonds enhance neural cell viability and while not increasing glial cell viability. Moreover, carbon nanofibers show prominence for tuning the cellular response as their dimension match biologically relevant cues. We show that nanofiber dimensions significantly alter glial and neural cell adhesion as well as their morphology. The properties of the hybrid structures can be tailored, both geometrically and chemically, with high definition. Consequently, these materials possess exceptionally high potential to achieve optimal host response just with the electrode material.
Inorganic particulate matter in the lung tissue of idiopathic pulmonary fibrosis patients reflects population density and fine particle levels
(2019-06-01) Mäkelä, Kati; Ollila, Hely; Sutinen, Eva; Vuorinen, Vesa; Peltola, Emilia; Kaarteenaho, Riitta; Myllärniemi, Marjukka
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Idiopathic pulmonary fibrosis (IPF) is a chronic lung disease with a dismal prognosis and an unknown etiology. Inorganic dust is a known risk factor, and air pollution seems to affect disease progression. We aimed to investigate inorganic particulate matter in IPF lung tissue samples. Using polarizing light microscopy, we examined coal dust pigment and inorganic particulate matter in 73 lung tissue samples from the FinnishlPF registry. We scored the amount of coal dust pigment and particulate matter from 0 to 5. Using energy dispersive spectrometry with a scanning electron microscope, we conducted an elemental analysis of six IPF lung tissue samples. We compared the results to the registry data, and to the population density and air quality data. To compare categorical data, we used Fisher's exact test; we estimated the survival of the patients with Kaplan-Meier curves. We found inorganic particulate matter in all samples in varying amounts. Samples from the southern regions of Finland, where population density and fine particle levels are high, more often had particulate matter scores from 3 to 5 than samples from the northern regions (31/50, 62.0% vs. 7/23, 30.4%, p = 0.02). The highest particulate matter scores of 4 and 5 (n = 15) associated with a known exposure to inorganic dust (p = 0.004). An association between particulate matter in the lung tissue of IPF patients and exposure to air pollution may exist.
Integrating Carbon Nanomaterials with Metals for Bio-sensing Applications
(2019-01-01) Sainio, Sami; Leppänen, Elli; Mynttinen, Elsi; Palomäki, Tommi; Wester, Niklas; Etula, Jarkko; Isoaho, Noora; Peltola, Emilia; Koehne, Jessica; Meyyappan, M.; Koskinen, Jari; Laurila, Tomi
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
Age structure in most developed countries is changing fast as the average lifespan is increasing significantly, calling for solutions to provide improved treatments for age-related neurological diseases and disorders. In order to address these problems, a reliable way of recording information about neurotransmitters from in vitro and in vivo applications is needed to better understand neurological diseases and disorders as well as currently used treatments. Likewise, recent developments in medicine, especially with the opioid crisis, are demanding a swift move to personalized medicine to administer patient needs rather than population-wide averages. In order to enable the so-called personalized medicine, it is necessary to be able to do measurements in vivo and in real time. These actions require sensitive and selective detection of different analytes from very demanding environments. Current state-of-the-art materials are unable to provide sensitive and selective detection of neurotransmitters as well as the required time resolution needed for drug molecules at a reasonable cost. To meet these challenges, we have utilized different metals to grow carbon nanomaterials and applied them for sensing applications showing that there are clear differences in their electrochemical properties based on the selected catalyst metal. Additionally, we have combined atomistic simulations to support optimizing materials for experiments and to gain further understanding of the atomistic level reactions between different analytes and the sensor surface. With carbon nanostructures grown from Ni and Al + Co + Fe hybrid, we can detect dopamine, ascorbic acid, and uric acid simultaneously. On the other hand, nanostructures grown from platinum provide a feasible platform for detection of H2O2 making them suitable candidates for enzymatic biosensors for detection of glutamate, for example. Tetrahedral amorphous carbon electrodes have an ability to detect morphine, paracetamol, tramadol, and O-desmethyltramadol. With carbon nanomaterial-based sensors, it is possible to reach metal-like properties in sensing applications using only a fraction of the metal as seed for the material growth. We have also seen that by using nanodiamonds as growth catalyst for carbon nanofibers, it is not possible to detect dopamine and ascorbic acid simultaneously, although the morphology of the resulting nanofibers is similar to the ones grown using Ni. This further indicates the importance of the metal selection for specific applications. However, Ni as a continuous layer or as separate islands does not provide adequate performance. Thus, it appears that metal nanoparticles combined with fiber-like morphology are needed for optimized sensor performance for neurotransmitter detection. This opens up a new research approach of application-specific nanomaterials, where carefully selected metals are integrated with carbon nanomaterials to match the needs of the sensing application in question.
Interface matters - Effects of catalyst layer metallurgy on macroscale morphology and electrochemical performance of carbon nanofiber electrodes
(2023-01) Pande, Ishan; Pascual, Laura Ferrer; Kousar, Ayesha; Peltola, Emilia; Jiang, Hua; Laurila, Tomi
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
The effect of catalyst materials and different process parameters on the growth of carbon nanofibers (CNFs) has been widely investigated. Typically, an adhesion metallization is required together with the catalyst to secure adequate attachment to the surface. The interactions within this multilayer structure and their effect on CNF growth and morphology has, however, not been thoroughly assessed. Thus, this work presents the growth behavior, the macroscale morphology, and the basic electrochemical characteristics of CNFs grown on two types of substrates - (1) Si + 80 nm Cr + 20 nm Ni, and (2) Si + 20 nm Ti + 20 nm Ni. Our results show that the macroscale geometric parameters of CNFs can be readily altered by using different adhesive layers. The inherently unstable Ti-Ni interface results in diffusion of Ni towards the silicon wafer to form silicide, which reduces the amount of available Ni for CNF nucleation, and therefore, the population density of fibers is reduced. On the other hand, the Cr-Ni interface results in a larger population density, but the rate of growth is reduced due to diffusion of carbon into the thicker Cr layer. The results are rationalized by using relevant binary and ternary phase diagrams. Further, cyclic voltammetry experiments show that the pseudocapacitance of CNFs shows a correlation with the length and population density of fibers, while the electron transfer kinetics appear nearly reversible for all the electrodes. This simple approach can be used for tailoring CNFs for specific applications by controlling their macroscale geometrical parameters.