14:15-14:40: Virginia Ranaweera
Title: Polydimethylsiloxane (PDMS) as a flexible substrate for implantable graphene devices
Abstract: Implantable graphene devices have attracted interest among researchers as a more effective and long-lasting solution to many medical conditions. The ultimate target of the GIN research group is to build a Graphene-based nerve-machine interface for neuroprosthetics.
Graphene as a single layered biocompatible flexible material with excellent electrical properties and mechanically durability is by far the most suitable material to facilitate as the interface material for this device.
In this research the focus was to find a suitable flexible substrate to support the graphene on this implantable field effect transistor. Literature provided many suitable candidates which are biocompatible and flexible. Graphene produced by chemical vapour deposition (CVD) is usually transferred to the required substrate using polymethyl methacrylate (PMMA) which leaves behind residues. Hence an attempt was made to avoid the necessity for a transfer mediator. By considering various fabrication techniques associated with the suitable candidates PDMS was chosen to try out first. Experiments were done by directly depositing a PDMS thin film which is around 20 µm on to the graphene, eliminating the intermediate transfer process. This flexible graphene-PDMS stack was supported by a SiO2 chip to facilitate characterisation and functionalization.
The graphene is modified by two-photon oxidation (2PO) to enhance the binding interaction between graphene and the hydro-gel containing proteins and neurons. Preliminary experiments indicate the feasibility to oxidise graphene while on PDMS. Further research needs to be done to optimise 2PO parameters and to design the device fabrication.
Supervisors: Andreas Johansson, Mika Pettersson
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14:40-15:05: Hassan Morsy
Title: The structural determinants underlying unusual absorption spectra of a bacterial phytochrome
Abstract: The spectral properties and light sensitivity of bacterial phytochromes (BphPs) are critically shaped by their structural determinants, enabling adaptation to diverse environmental conditions. This study investigates the role of the PHY-ARM, a loop or a helical motif located near the bilin chromophore-binding domain (CBD), in the unique spectral behavior of the BphP from Bradyrhizobium sp. STM 3809 (BrBphP), focusing on its involvement in light-induced conformational change. Molecular cloning is used to generate chimeric constructs by exchanging the ARM structure of BrBphP with that of the phytochrome from Deinococcus radiodurans (DrBphP). These chimeric proteins were subsequently expressed, purified, and characterized through UV-VIS spectroscopy to assess their photoconversion efficiency, spectral characteristics, and the stability of their red (Pr) and far-red (Pfr) light-absorbing states. The findings reveal that the PHY-ARM is a key modulator of the chromophore environment, influencing spectral shifts and light response dynamics. The BrARM was shown to induce a red-shifted dark state, reduce far-red light absorption of the Pfr state, and speed up the dark reversion because it favors the Pr state or disfavors the Pfr state. These features indicate an evolutionary adaptation to low-light environments where the scarcity of far-red light would naturally restrict the formation of the Pfr state. By stabilizing the Pr state and reducing the frequency of photoconversion, BrBphP can conserve energy until conditions with adequate light are present to trigger a significant response. In contrast, the DrARM enhanced Pfr state stability, facilitating extended light responses. These results highlight the structural flexibility of phytochromes and the critical role of the PHY-ARM in optimizing photoreceptor functionality. This research advances our understanding of phytochrome spectral behavior and offers potential applications in developing light-responsive systems for biotechnology and synthetic biology.
Supervisors: Dr. Heikki Takala, Dr. Cornelia Böhm, and Ms. Iida Tuure
