Fig. 3.

Controllable biodegradation of MnO₂ hybrid nanoscaffolds. a A schematic diagram explaining an unconventional redox biodegradation mechanism of our MnO₂ hybrid nanoscaffolds. This redox biodegradation can be achieved through either bioreductants exists commonly in human body such as vitamin C, electrically delivered reduction signals or by stem cells cultured with the nanoscaffold. Degradation products include water (colored in green) and Mn²⁺ (colored in blue). b Controllable redox biodegradation of MnO₂ hybrid nanoscaffolds demonstrated through cyclic voltammetry. A successful degradation of nanoscaffolds were confirmed by the disappearance of yellow color from nanoscaffold triggered by electrical stimuli. x axis indicates voltage (v). c, d Degradation of nanoscaffold by commonly existent bioreductants (e.g., vitamin C), indicated by the decay of micropatterns from the micropatterned nanoscaffold (c); and the disappearance of manganese elements from the substrate after degradation through EDS analysis (d). cps means count per scan. e Time dependent biodegradation of MnO₂ hybrid nanoscaffolds in cell culture without addition of any external trigger. The degradation of nanoscaffold was examined based on the thickness of the black-colored layer sandwiched between two layers of cells. GO nanoscaffolds were used as a negative control and no noticeable degradation was observed. Half-degradation time of MnO₂ hybrid nanoscaffolds was determined to be around 2 weeks. f Controllable fast-biodegradation of MnO₂ hybrid nanoscaffolds. By controlling bioreductant (vitamin C) concentrations, a fast degradation of iPSC-NSC seeded nanoscaffold and formation of iPSC-NSC sheet was achieved. Nanoscaffold is indicated by the dark-colored background before degradation. Size of each image is 1 cm by 1 cm. Cells were stained with pink color for convenience of observation. Scale bar: c 100 μm