Kamil Awsiuk oral presentation (OB2-Mon1-2-2)
Orientation of immunoglobulin and streptavidin adsorbed on spin-cast polythiophene films: Impact of polymer film crystallinity
1 (1) M. Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków, Poland
2 (2) Institute of Nuclear & Radiological Sciences & Technology, Energy & Safety, NCSR Demokritos, Agia Paraskevi, 15310 Athens, Greece
3 (3) Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków, Poland
Many bioelectronic and biosensor applications are based on polythiophenes (PTs) - promising conducting and solution-processable polymers, and rely on biofunctionalization of polymer surfaces with proteins through adsorption. Spin-cast PT films were examined prior to and after protein adsorption with time of flight secondary ion mass spectrometry (ToF-SIMS) and other surface science techniques (AFM, XPS). Principal component analysis (PCA) of ToF-SIMS data revealed crystalline texture of polymer films , present for regioregular but absent for regiorandom PTs, and its impact on orientation  (or conformation ) of adsorbed proteins that affects their biorecognition (Fig.1).
PCA resolved the surface alignment of alkyl side-chains and differentiated the ToF-SIMS data for amorphous and semi-crystalline (edge-on texture) PTs films . Film structure was also confirmed with AFM and Grazing Incidence X-ray Diffraction.
Since ToF-SIMS probes the outermost surface composition, molecular orientations of immunoglobulin (IgG)  and streptavidin adsorbed to different PT polymers were concluded, based on amino acid ion fragments analyzed with PCA and relative prevalence of amino acids in different parts of protein molecule. In turn, biorecogntion of adsorbed proteins was examined with enzyme-linked immunosorbent assay. Obtained results indicate that both the improved orientational order and higher biorecognition efficiency is observed for PTs films with the semi-crystalline structure.
Acknowledgment: NCN Grant No. UMO-2011/03/N/ST5/04764
 K. Awsiuk, A. Budkowski, M.M. Marzec, P. Petrou, J. Rysz, A. Bernasik, Langmuir 30 (46), 2014, 13925-13933.
 K. Awsiuk, A. Budkowski, P. Petrou, M.M. Marzec, M. Biernat, T. Jaworska-Gołąb, J. Rysz, Colloids and Surfaces B: Biointerfaces, 148, 2016, 278-286.