Tap150a

Atomic Force Microscopy (AFM) imaging was carried out using a commercial AFM (Dimension Icon, Bruker Co., Santa Barbara, CA, USA). The ScanAsyst mode was applied using a silicon tip (TAP150A, Bruker, nominal frequency of 150 kHz, nominal spring constant of 5 N/m) with a scan resolution of 512 samples per line at a scan rate of 1.0 Hz for an area 2.5 µm × 2.5 µm. Integral and proportional gains were optimized empirically during scanning. All post-image analysis was carried out using the built-in AFM software and Nanoscope Analysis (NanoScope VIII MultiMode AFM, Bruker Nano Inc., Nano Surfaces Division, Santa Barbara, CA, USA). Three randomly selected areas were scanned per sample and the results of roughness (root mean squared roughness, Rq) were presented as the mean ± standard deviation of three different samples for each group. The statistics used for contact angle analysis was a student t-test to distinguish statistical significance, p = 0.05.

AFM images were collected using a MultiMode SPM with a Nanoscope III controller (Veeco Instruments, Santa Barbara, CA) operated in tapping-mode in air. The AFM cantilevers used in air had a spring constant of 5 newtons/m (Bruker cantilevers, TAP150A) with resonance frequencies ranging between 120 and 160 kHz. All recorded AFM images consist of 512 × 512 pixels with scan frequency ≤1 Hz. Each H-NS-DNA binding experiment was performed at least in duplicate. AFM images were obtained at several separate locations across the mica surface to ensure a high degree of reproducibility and were used for statistical analysis of H-NS-DNA complexes. Only H-NS-DNA complexes that were completely visible in AFM image were considered for statistical analysis. The images were simply flattened using the Gwyddion software (Version 2.25) without further image processing (52 ).

The roughness of the scaffolds surface was evaluated using an AFM (TAP150A) in the tapping mode (spring constant 2.919 n/m) as described previously (n=3).11 (link),12 (link) In brief, the root mean square roughness was calculated from the 5 µm scan of three areas using the NanoScope^® analysis software version 1.40 (Bruker Corporation, Billerica, MA, USA). The PeakForce quantitative nanomechanical mapping was used to obtain an FV modulus using the modified Hertzian model.