| 1. |
- Bolin, Maria
(författare)
-
Conjugated polymer surface switches for active cell control
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Conjugated polymers have been found useful in a wide range of applications such as sensors, electrochemical transistors, solar cells, and printed electronics due to their mechanical, optical and electronic properties. An amazing research field has grown during the last three decades since the discovery of conducting polymers in 1976. Since the materials can be made from solutions, different processing methods such as spin coating and vapor phase polymerization can be used to coat a huge variety of substrates. The choice of method depends mainly on monomer solubility and kind of substrate to be coated. During the synthesis the polymers can be chemically modified to tailor their functionalities. Due to this variability in materials and the processability, electronics can be achieved on unconventional substrates such as flexible plastic foils and cell culturing dishes. As a contrast to inorganic, usually metallic materials, conducting polymers are built up from organic compounds in a molecular structure with soft mechanical properties that have shown to be a benefit in combination with biology, ranging from interactions with cells to interactions with advanced biological species such as tissues. This combination of research fields and the possible applications are merged within the field of organic bioelectronics.The primary purpose of this thesis is to give a background to organic electronics in general and how electrochemical devices can be processed and developed for biological applications in particular. An organic electronic surface switch is introduced to control cell adhesion and proliferation as well as an electrochemical transistor to spatially tune the cell adhesion along an electrochemical gradient. To mimic a more natural cell environment a three dimensional fiber substrate was used to design an electronically active matrix to promote nerve cell adhesion and communication. By combining standard microfabrication techniques and conjugated polymers desired patterns of electroactive polymer were created to enable active regulation of cell populations and their extracellular environment at high spatial resolution. Finally, a brief look into future challenges will also be presented.
|
|
| 2. |
- Gabrielsson, Erik O., 1985-
(författare)
-
Monopolar and Bipolar Membranes in Organic Bioelectronic Devices
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the 1970s it was discovered that organic polymers, a class of materials otherwise best know as insulating plastics, could be made electronically conductive. As an alternative to silicon semiconductors, organic polymers offer many novel features, characteristics, and opportunities, such as producing electronics at low costs using printing techniques, using organic chemistry to tune optical and electronic properties, and mechanical flexibility. The conducting organic polymers have been used in a vast array of devices, exemplified by organic transistors, light-emitting diodes, and solar cells. Due to their softness, biocompatibility, and combined electronic and ionic transport, organic electronic materials are also well suited as the active material in bioelectronic applications, a scientific and engineering area in which electronics interface with biology. The coupling of ions and electrons is especially interesting, as ions serve as signal carriers in all living organisms, thus offering a direct translation of electronic and ionic signals. To further enable complex control of ionic fluxes, organic electronic materials can be integrated with various ionic components, such as ion-conducting diodes and transistors.This thesis reports a background to the field of organic bioelectronic and ionic devices, and also presents the integration of ionic functions into organic bioelectronic devices. First, an electrophoretic drug delivery device is presented, capable of delivering ions at high spatiotemporal resolution. The device, called the organic electronic ion pump, is used to electronically control amyloid-like aggregation kinetics and morphology of peptides, and offers an interesting method for studying amyloids in vitro. Second, various ion-conducting diodes based on bipolar membranes are described. These diodes show high rectification ratio, i.e. conduct ions better for positive than for negative applied voltage. Simple ion diode based circuits, such as an AND gate and a full-wave rectifier, are also reported. The AND gate is intended as an addressable pH pixel to regulate for example amyloid aggregation, while the full-wave rectifier decouples the electrochemical capacity of an electrode from the amount of ionic charge it can generate. Third, an ion transistor, also based on bipolar membranes, is presented. This transistor can amplify and control ionic currents, and is suitable for building complex ionic logic circuits. Together, these results provide a basic toolbox of ionic components that is suitable for building more complex and/or implantable organic bioelectronic devices.
|
|
| 3. |
- Golabi, Mohsen, 1979-
(författare)
-
Functionalised surfaces for bacterial discrimination
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bacterial detection and identification is a critical step in many arenas, including food and water safety, clinical diagnostics, bioprocess control and biosecurity. Social hygiene has a direct correlation with the strict control of microorganisms in these fields. The worldwide cases of bacterial infectious disease is assessed to be 1-2 billion annually, and these have a massive negative effect on the global economy. Although many precise techniques are currently available, a huge mortality and morbidity related to bacterial infection disease continues to be reported annually due to misdiagnosis or delay in diagnosis. Increasing efficiency and reliability of pathogen detection methods will potentially improve social health and protect society against pathogenic diseases.The development of culture media for selective isolation and differentiation of bacteria started in the late 19th century. Immunological assays and then genotyping techniques were developed in 20th century, in addition to many less commonly used techniques for bacterial detection. Each of the currently used methods has its advantages and weaknesses in terms of speed, cost and accuracy. Much effort has recently been devoted to developing biosensors for bacterial detection for simpler and more rapid use.This thesis is focused on functionalised surfaces for the development of biosensors for bacterial discrimination and detection, and is divided in three subsections. First, we explored a new approach for bacterial discrimination based on pattern recognition. Traditional culturing methods discriminate bacteria based on their metabolic activity pattern. Taking inspiration from the extensive body of work that reports the use of electronic-noses to differentiate bacteria based on the volatiles patterns they produce, we explored the possibility of bacteria differentiation based on adhesion patterns. By altering the electropolymerisation conditions, the physicalchemical surface properties of polypyrrole (PPy) can be tuned to fabricate a range of dissimilar surfaces. The adhesion of different bacteria on a series of polymers was measured. Data analysis of the adhesion patterns proved that bacteria can be discriminated by examining their adhesion to dissimilar surfaces. Next, we developed a new functionalisation of PPy by doping PPy with 4-N-Pentylphenylboronic Acid and investigated the modulation of bacteria binding to those surfaces. In this second section, a new electropolymerisation technique for whole-cell imprinting was developed based on different functional monomers. 3-Aminophenyl boronic acid was shown to be a good monomer to produce whole-cell imprinted polymers (CIP) with high affinity for bacterial cells with improved releasing ability. Finally, in the third section aptamers, which are promising synthetic recognition elements, were explored for bacterial detection testing. A specific aptamer was used to fabricate of a prototype of label-free aptasensor for bacterial detection. Also, the SELEX process was used to produce a pool of aptamers, or “polyclonal” aptamers, which targeted a group of bacteria species. Using polyclonal aptamers as a recognition element enables biosensors to enhance their resolution to detect broader types of bacterial species using a single serological-like test.
|
|
| 4. |
- Persson, Kristin
(författare)
-
Electronic Control of Cell Cultures Using Conjugated Polymer Surfaces
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the field of bioelectronics various electronic materials and devices are used in combination with biological systems in order to create novel applications within cell biology and medicine. A famous example of a successful bioelectronics application is the pacemaker. Metals are the most common electrical conductors, whereas polymers are generally considered being insulators. However, in the late 1970s it was shown that a special class of polymers with conjugated double bonds, could in fact, after some chemical modifications, conduct electricity. This was the start of the research field known as conducting polymers, and then later on organic electronics, a research area that has grown rapidly during the last decades. Conjugated polymers are also suitable to interact and interface with cells and tissues, as they are generally soft, flexible and biocompatible. In addition, their chemical properties can be tailor-made through synthesis to fit biological requirements and functions. During the last years applications using organic bioelectronics have become numerous.This thesis describes applications based on different conjugated polymers aiming to stimulate and control cell cultures. When culturing cells it is of interest to be able to control events such as adhesion, spreading, proliferation, differentiation and detachment. First, the impact of different polymer compositions and redox states on the adhesion of bacteria and subsequent biofilm formation was investigated. Similar polymer electrodes were also used to steer differentiation of neural stem cells, through changes in the surface exposure of a relevant biomolecule. Controlled delivery of molecules was achieved by coating nanoporous membranes with polymers that swell and contract when changing the redox state. Finally, electronic control over cell detachment using a water-soluble polymer was achieved. When applying a positive potential to this polymer, it swells, cracks and finally detaches, taking the cells that was cultured on top along with it. Together, the work and results presented in this thesis demonstrate a versatile conjugated polymer technology to achieve electronic control of the different growth stages of cell cultures as well as cellular functions.
|
|
| 5. |
- Toss, Henrik
(författare)
-
Operating Organic Electronics via Aqueous Electric Double Layers
- 2015
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The field of organic electronics emerged in the 1970s with the discovery of conducting polymers. With the introduction of plastics as conductors and semiconductors came many new possibilities both in production and function of electronic devices. Polymers can often be processed from solution and their softness provides both the possibility of working on flexible substrates, and various advantages in interfacing with other soft materials, e.g. biological samples and specimens. Conducting polymers readily partake in chemical and electrochemical reactions, providing an opportunity to develop new electrochemicallydriven devices, but also posing new problems for device engineers.The work of this thesis has focused on organic electronic devices in which aqueous electrolytes are an active component, but still operating in conditions where it is desirable to avoid electrochemical reactions. Interfacing with aqueous electrolytes occurs in a wide variety of settings, but we have specifically had biological environments in mind as they necessarily involve the presence of water. The use of liquid electrolytes also provides the opportunity to deliver and change the device electrolyte continuously, e.g. through microfluidic systems, which could then be used as a dynamic feature and/or be used to introduce and change analytes for sensors. Of particular interest is the electric double layer at the interface between the electrolyte and other materials in the device, specifically its sensitivity to charge reorganization and high capacitance.The thesis first focuses on organic field effect transistors gated through aqueous electrolytes. These devices are proposed as biosensors with the transistor architecture providing a direct transduction and amplification so that it can be electrically read out. It is discussed both how to distinguish between the various operating mechanisms in electrolyte thin film transistors and how to choose a strategy to achieve the desired mechanism. Two different strategies to suppress ion penetration into, and thus electrochemical doping of, the organic semiconductor are presented.The second focus of the thesis is on polarization of ferroelectric polymer films through electrolytes. A model for the interaction between the remnant ferroelectric charge in the polymer film and the mobile ionic charges of the electrolyte is presented, and verified experimentally. The reorientation of the ferroelectric polarization via the electric double layer is also demonstrated in a regenerative medicine application; the ferroelectric polarization is shown to affect cell binding, and is used as a gentle method to nondestructively detach cells from a culture substrate.
|
|
| 6. |
- Tybrandt, Klas
(författare)
-
Ionic Circuits for Transduction of Electronic Signals into Biological Stimuli
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modern electronics has revolutionized the way information is processed and stored in our society. In health care and in biology it is of great interest to utilize technology to regulate physiology and to control the signaling pathways. Therefore, the coupling of electronic signals to biological functions is of great importance to many fields within the life sciences. In addition to the conventional inorganic electronics, a new branch of electronics based on organic materials has emerged during the last three decades. Some of these organic materials are very attractive for interacting with living systems since they are soft, flexible and have benevolent chemical properties.This thesis is focused on the development of ionic circuits for transduction of electronic signals into biological stimuli. By developing such an intermediate system technology between traditional electronics and biology, signals with chemical specificity may be controlled and addressed electronically. First, a technology is described that enables direct conversion of electronic signals into ionic ones by the use biocompatible conductive polymer electrodes. The ionic bio-signals are transported in lateral channel configurations on plastic chips and precise spatiotemporal delivery of neurotransmitter, to regulate signaling in cultured neuronal cells, is demonstrated. Then, in order to achieve more advanced ionic circuit functionality, ion bipolar junction transistors were developed. These ion transistors comprise three terminals, in which a small ion current through one terminal modulates a larger ion current between the other two terminals. The devices are functional at physiological salt concentrations and are utilized to modulate neurotransmitter delivery to control Ca2+ signaling in neuronal cells. Finally, by integrating two types of transistors into the same chip, complementary NOT and NAND ion logic gates were realized for the first time. Together, the findings presented in this thesis lay the groundwork for more complex ionic circuits, such as matrix addressable delivery circuits, in which dispensing of chemical and biological signals can be directed at high spatiotemporal resolution.
|
|
