Fig. 5

Schematics and characterizations of amelogenin for enamel demineralization. (I) a Schematic of the formation of oligomer and nanosphere at different pH values. With the increase of pH, the amelogenin residues with positive charges are gradually deprotonated, thus the weak hydrophobic interactions lead to the formation of the nanospheres. b TEM images of the linear arrays of amelogenin nanospheres. c SEM image of a mature amelogenin ribbon showing well-defined edges. (II) a SEM images of native enamel, in which the arrows show the enamel orientation. b–d SEM images of newly formed crystal layer after the remineralization treatment with CS-AMEL hydrogel for 1 week. b Red rectangles 1 and 2 in the inserted image are selected regions in b, c. White arrows exhibit the orientation of newly formed crystal layer. c The new layer is closely combined to the enamel surface. d Red arrows show the typical bundle of parallelly aligned crystals inside the new layer. The inserted image shows the homogenous surface of the new layer. (I) was reproduced with permissions from ref. ²⁴⁴, 2011 American Society for Biochemistry and Molecular Biology, and ref. ²¹⁴, 2005 American Association for the Advancement of Science. (II) was reproduced with permission from ref. ²⁶⁴, 2013 Elsevier