Bioscope 2 afm

The morphology of biofilms formed on glass and PVC surfaces was examined by atomic force microscopy (AFM). AFM measurements were performed in air using a Bioscope II AFM with a NanoScope V controller (Veeco, Santa Barbara, CA, USA). Biofilms were imaged in contact mode using an MLCT-D silicon nitride cantilever with a nominal tip apex radius of 20 nm. The height and deflection images were obtained simultaneously at a scan rate 0.5 Hz, at a resolution of 512 pixels per line. Each image has been done in different places selected randomly from 30 × 30 µm² area, for a sample. AFM images were flattened and plane fitted prior to analysis. The calculated surface characteristics parameters included the root mean square (RMS) roughness (Rq), average height and surface area differences. The Rq is the root mean square average of height deviations taken from the mean data plane. Average height is the average of all the Z values. Surface area difference is the difference between the analyzed region’s three dimensional surface area and its two dimensional projected surface area. The data were analyzed with the NanoScope Analysis 1.7 software from Bruker. AFM imaging was performed in the Center of Quantum Optics at the Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Toruń, Poland.

A silicon wafer with hollow wells (squares with borders ranging from 5 to 10 µm) was immersed in acidic piranha solution (H₂SO₄ 3:1 H₂O₂) for 15 min; it was then washed with a large volume of distilled water and dried. Finally, 0.5 µL of yeast cell solution was dropped on the wafer and left until it was visually dry.
The BioScope II AFM combined with an inverted optical microscope developed by Veeco Instruments Ltd. (Santa Barbara, CA, USA) and an NP-D cantilever (Bruker, Camarillo, CA, USA) was used for the measurements. AFM contact mode in the phosphate buffer solution was applied at 0.15 Hz. Experiments were performed with the PPy-modified, non-modified, and inactivated yeast cells. Raw data were analysed using NanoScope Analysis 1.5 software.

AFM imaging was performed using a Bioscope II AFM (Veeco) mounted on an Olympus IX 73 inverted light microscope (Olympus). The microscope was equipped with a heated stage (37 °C) and cells were imaged in HEPES-buffered medium. Measurements were performed in contact mode using silicon nitride cantilevers with a nominal force constant of 0.01 N/m. Cantilevers were calibrated before every series of experiments by thermal tune using the manufacturer’s software. Force indentation curves were analyzed according to the model of Discher et al.^{23 (link)} computed with MATLab software. Data from at least 10 cells in at least three culture dishes were included in the analysis. Statistical analysis was performed as univariate analysis, defining a p-value of <0.05 as statistically significant.