Materials And Methods For Afm Adhesion Measurements

4. Materials and Methods for AFM Adhesion Measurements 4.1. Materials Paraformaldehyde (4% in 0.1 M Phosphate Buffer Saline), 1 Phosphate Buffered Saline (PBS) and Muscovite Mica (V-1 Quality) were purchased from Electron Microscopy Sciences (Hatfield, PA). Coverslips (No.1.5 thickness) were purchased from MatTek Corporation (Ashland, MA). MDA-MB-231 and Hs578Bst cell lines, growth media (L-15 fand 46-X, respectively), and media supplements (penicillin/streptomycin and fetal bovine serum) were purchased from American Type Culture Collection (ATCC, Manassas, VA). Uncoated n-doped silicon AFM probes (MPP-31100) were purchased from Bruker (Billerica, MA). 4.2. AFM Tip Preparation AFM tips were functionalized using a simple†¦show more content†¦The breast cancer cells were incubated at 37  °C under normal atmospheric pressure, while the normal breast cancer cells were incubated at 37  °C in environments with 5% CO2 levels, respectively. The MDA-MB-231 and Hs578bst cells were grown respectively in L-15 or 46-X base media. These were supplemented with 100 I.U./ml penicillin/100 ÃŽ ¼g/ml streptomycin and 10% FBS. The cells were first rinsed with 1X PBS and then fixed with 4 wt% paraformaldehyde solution for 10 mins at room temperature. They were then rinsed with PBS solution for three more times, before a final rinse with purified water. Finally, the samples were dried in a vacuum desiccator for at least 5 hours. 4.4. AFM tip Characterization An FEI Quanta 200 FEG Environmental-SEM (FEI, Hillsboro, OR) was used to view the AFM tips before and after coating. This was done to determine whether or not the AFM tips were successfully dip-coated. The tips were also viewed in the ESEM after the pull-off tests. This was done to ensure that no coating was lost during the AFM pull-off. 4.5. Force-Displacement Measurements All of the AFM experiments were performed in a Dimension NanoMan AFM (Bruker, Billerica, MA). This was done under ambient conditions at room temperature of 24  °C and a relative humidity of 45%. The photo-detector sensitivity was calibrated on a hard mica surface. The adhesive forces were measured for the following configurations: (1) bare tips and normal