Np o10

Cell probes were prepared using triangular shaped tipless cantilevers (microlevers) (catalog no. NP-O10; Bruker Corporation) coated with bioinspired polydopamine wet adhesives. Cantilevers were immersed for 1 h in a 10 mM Tris buffer solution (pH 8.5) containing 4 mg ml⁻¹ dopamine hydrochloride (99%; Sigma) and dried with N₂ flow. Single cells were then attached onto the polydopamine-coated cantilevers using a Bioscope Catalyst AFM (Bruker Corporation). Hydrophobic substrates were prepared by immersing gold-coated substrates overnight in solutions of 1 mM 1-dodecanethiol (Sigma-Aldrich) (98%), rinsing them with ethanol, and drying them under N₂. To have cell aggregates on the hydrophobic surface, we deposited a drop of a cell suspension and allowed it to sediment for 10 to 15 min, and the cells were covered with 4 ml of PBS. Then, the cantilever was brought into contact with an isolated cell for 3 min, and the obtained cell probe was then transferred over a cell aggregate for cell-cell force measurements. The nominal spring constant of the cantilever was ∼0.06 N m⁻¹ as determined by the thermal noise method. Single-cell force spectroscopy measurements were performed at room temperature (20°C) in PBS, using a Bioscope Catalyst combined with an inverted optical microscope (Zeiss Axio Observer Z1 equipped with a Hamamatsu camera C10600 [Oberkochen, Germany]).

The cell adhesion forces were measured on mammalian HeLa cells using a Multimode IIIa AFM system with PicoForce (Bruker Nano: Santa Barbara, CA, USA). For the adhesion measurements we used tip-less silicon nitride cantilevers (NP-O10, Bruker), functionalized overnight with 2 mg/ml concanavalin A. The spring constant of the cantilever was calibrated using Thermal tune method before performing the experiments (0.068 N/m). The deflection sensitivity of the cantilever (43 nm/V) was also measured before starting the experiments by acquiring force curves on the cell free areas of the glass bottom petri dishes. For measuring the cell adhesion force, the cell was approached towards the surface coated overnight with 10 µg/mL fibronectin with a set force of 1 nN and a speed rate of 10 μm/s. After a contact time of 5 s between the cell and the fibronectin, the sample was retracted 18 μm with a speed rate of 5um/s. The deflection signal of the probe was recorded as a function of retraction until the cell was removed from the surface.

AFM imaging of the PPy/DBSA films on native polymers and whilst applying potentials of +300 mV, −300 mV and −800 mV was performed using the JPK Biowizard II with electrochemistry cell in CO₂ independent cell medium (18045-088, Life Technology). Images were acquired in contact mode using cantilevers with spring constant of ~0.12 N/m (NP-O10, Bruker). Images were first collected on native polymer with no applied potential. The tip was then retracted and a constant potential of +300 mV was applied using an eDAQ EA161 potentiostat. Imaging was resumed after the current had reached steady-state. This process was repeated for applied potentials of −300 mV and −800 mV. Scans of 10 μm were performed at a scan rate of 1 Hz. Experiments were repeated on 3 sample films.

To analyze the mechanical property of cells during the direct reprogramming of fibroblasts into neurons, mechanical measurements of single cells were performed using AFM (Bruker BioscopeResolve, Bruker Corp., USA) with silicon tipless cantilevers (NPO‐10, Bruker Corp., USA), a high sensitive cantilever k = 0.06 N m⁻¹, and sample Poisson's ratio of 0.499 at the UCLA Nano and Pico Characterization Facility. Fibroblasts were transduced with individual or different combinations of the transgenes and then the cell stiffness at various time points was measured during the reprogramming process (e.g., days 0, 1, and 3), wherein for each condition at least 30 cells were analyzed. During the measurements, cells were cultured on a glass bottom dish with pre‐warmed PBS and set on a temperature‐controlled stage at 37 °C. The force–distance curves were recorded and the elastic modulus of cells was calculated by NanoScope Analysis (Bruker Corp., USA) using the Hertz model as the Fit Model. Similar AFM measurements were also conducted on control samples of non‐transduced and GFP‐transduced fibroblasts as well as fibroblasts treated with small molecule inhibitors or cultured on different biomaterials

The interactions between Ce6, SiO₂-P_Ce6-IL and MRSA biofilm were measured by AFM. A common protocol was employed for the attachment of SiO₂-P_Ce6-IL1, SiO₂-P_Ce6-IL2 or Ce6 to the AFM tip: the AFM tip (NP-O10, Bruker) was placed in epoxy, which was allowed to cure for some time (total 5 min) 48 , 1 µL of SiO₂-P_Ce6-IL1, SiO₂-P_Ce6-IL2 and Ce6 (120 µM) were placed on the AFM tip. After drying at 80 ℃ for 24 h, the decorated tip was washed by distilled water to eliminate unattached nanoparticles. SEM was used to examine the SiO₂-P_Ce6-IL nanoparticles that terminated on the AFM tip.