Figure 4. Tapping-mode AFM images of enamel crystals after interaction with amine-capped PAMAM dendrimers. A solution of G7 PAMAM dendrimers with an amine (-NH₂)-capped surface was allowed to flow over the crystals and allowed to remain for 2 min before being wicked off. The sample was dried in a desiccator before being imaged in air. (a) Crystal surfaces after exposure to 1 µL 78-nM dendrimer solution. (b) Crystal surfaces after exposure to 2 µL 78-nM dendrimer solution. (c) After the distilled-water-washed sample was rinsed with 100 mM phosphate buffer (pH 7.4). (d) After the sample (c) was rinsed with 200 mM phosphate buffer (pH 7.4). AFM images show the topographical image (1 µm x 1 µm) on the left, and phase image (1 µm x 1 µm) on the right.