Fig. 4.

Interface magnified: Chemical fingerprint at the surface of Mg implants is altered over time by degradation.

(A), Mg implants carefully retrieved from subcutaneous pockets for characterization of their surfaces. (B), Macroscopic observation of the Mg surface immediately following explantation after 1–28 d. (C), Scanning electron microscopy (SEM) images with a secondary electron detector showing the Mg surface with implant-adherent cells (arrowheads) and extracellular matrix. (D), Time survey of Mg surface chemical composition (Mg, O, Ca and P) using energy-dispersive X-ray spectroscopy (n = 3/time-point). (E), Top: Cross-sections of the degradation layer at the Mg surface observed with SEM using a backscattered electron detector (implant and tissues embedded in plastic). Yellow dotted line: degradation layer; bottom: Maps of Mg, O, C, Ca and P in the highlighted areas in E (C is generated from embedding medium). (F), Changes over time in degradation layer thickness and in the rate of thickening per day (n = 5–6/time-point).

Data are means ± s.e.m.; a: P < 0.05 versus days 1 and 3; b: P < 0.05 versus day 6. Unpaired Mann-Whitney U test. Scale B = 2 mm; C = 20 μm; E = 10 μm.