Browsing by Author "Gustafsson, Eero"

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  • Biocompatibility of Porous Films Used on Electrochemical Sensor Materials
    (2020-01-18) Gustafsson, Eero
     Sähkötekniikan korkeakoulu | Bachelor's thesis
  • A carbon-based electrochemical aptasensor for detection of vancomycin
    (2023-08-21) Gustafsson, Eero
     Kemian tekniikan korkeakoulu | Master's thesis
    Labelled, carbon-based electrochemical aptasensor was developed for detecting vancomycin from biologically relevant samples in the therapeutically relevant concentration ranges below 50µM. Both hand-prepared and commercially manufactured electrodes were used to measure vancomycin using square wave voltammetry (SWV) in measurement buffers such as phosphate buffered saline (PBS) and human plasma. In contrast to traditional gold-based electrochemical aptasensors, the electrode materials investigated in this work were carbon-based, with single-walled carbon nanotubes (SWCNTs) being the electrode material tested and tried, ultimately hoping for the carbon-based aptasensor architecture to function as an electrochemical platform technology for the detection of various different biomolecules for point-of-care (POC) testing. A couple of different aptamer functionalisation techniques were tested: (1) direct carbodiimide crosslinking via EDC/NHS chemistry, (2) using the 𝜋 − 𝜋 stacking to our advantage by using an aromatic linker molecule 1-pyrenebutyric acid with an NHS-ester and finally (3) trying to use carboxymethyl cellulose (CMC) as a monolayer for aptamer functionalisation via EDC/NHS coupling. Unfortunately the adsorptive tendencies of SWCNTs and unsuccessful coupling protocols seemingly hindered the sensor development process, as the AttoMB2-labelled aptamers seem to, against all hypotheses, adsorb to the SWCNT surfaces via the labelled end, compromising the degree of freedom required for optimal functioning. The ferrocene-labelled aptamers were seemingly unusable with these functionalisation trials at every stage of the project, due to inherent instability arising from uncertain phenomena. The result was a long project full of sensor development via the “trial-and-error”- method, with the end-product being capable of sensing vancomycin in rather limiting circumstances via the loss of current, most likely arising from the net loss of non- specifically attached aptamers due to the binding of vancomycin. Further development and testing volume is necessary for the future development of such a sensor, with consideration of other carbonaceous electrode materials recommended as well.
  • Challenges in aptamer-based sensor development using carbon nanotube networks
    (2024-12) Ferrer Pascual, Laura; Gustafsson, Eero; Siitonen, Juha; Durairaj, Vasuki; Laurila, Tomi
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Electrochemical aptamer-based (EAB) sensors represent a promising biosensing platform, leveraging the selectivity of aptamers and the advantages of electrochemical methods. These sensors offer high sensitivity, rapid response, low limits of detection, cost-effectiveness, and miniaturization potential. While gold electrodes have been predominantly used in EAB sensors, alternatives such as carbon nanotubes (CNTs) are gaining attention. CNTs offer advantages like large surface area and conductivity but pose challenges due to their reactivity and 3D network structure. In this study, we explore the development of EAB sensors using single-wall carbon nanotube (SWCNT) networks, emphasizing on the challenges and electroanalytical insights. Three key electrochemical parameters are proposed for assessing EAB sensor performance: (i) variations in peak current, (ii) shifts in peak position, and (iii) the restoration of the background current. Focusing solely on peak current changes can be misleading, as factors like aptamer surface depletion can influence it. Additionally, both partial and integrated currents should be monitored in square wave voltammetry (SWV) analysis, considering both ON and OFF behaviours across frequencies. This comprehensive approach provides a preliminary assessment of successful binding and surface passivation in EAB sensors when combined with surface analytical techniques such as surface plasmon resonance (SPR) measurements.
  • Geometrical and chemical effects on the electrochemistry of single-wall carbon nanotube (SWCNT) network electrodes
    (2023-10-20) Leppänen, Elli; Gustafsson, Eero; Wester, Niklas; Varjos, Ilkka; Sainio, Sami; Laurila, Tomi
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Single-wall carbon nanotube (SWCNT) network is a promising electrode material for bio detection. Unfortunately, the associations between their physical as well as chemical properties and observed electrochemical performance are not known. This hinders any systematic optimization of the network properties towards specific analytes. Here we present a consistent physicochemical and electrochemical characterization of differently treated SWCNT networks. The results unambiguously show that (i) even if the electrochemical properties of different electrodes are practically identical when assessed by surface insensitive outer sphere redox (OSR) probes their behavior with inner sphere redox (ISR) probes can be drastically different. Further, (ii) the choice of the modification method (structural, chemical, electrochemical) heavily depends on nature of the target analyte, which are typically ISR probes. Although, (iii) chemical changes in the carbon phase appeared to be minor, effects of different treatments on oxidation states of Fe appeared to have a strong effect on the electrochemical performance of the networks in the case of ISR probes.