## Materials and Methods
### In-Vivo Study  
Preliminary in vivo tissue compatibility tests of Zn ribbons, with similar AZ31 magnesium samples for comparison, were conducted by subcutaneous implantation in mice. A total of eight female, 17-20 g, C57 BK/6J mice were used and all procedures were approved by the University of Cincinnati Institutional Animal Care and Use Committee and followed the US National Institutes of Health guidelines for animal use. For this test, mice were anesthetized with isoflurane, given analgesics and two incisions were made on the back, just below the scapula, and two pockets were made on either side of the backbone. Inside each pocket was placed a two-strut segment (~5 mm long) of photo-chemically etched ribbon made of uncoated Zn (four mice) or uncoated Mg (AZ31 Mg, same pattern, four different mice), as shown in Figure 7. The incisions were closed with metal staples. One mouse with Zn ribbon died within 24 h of surgery for reasons not attributed to the Zn material. No issues with wound healing or animal behavior were observed in the remaining animals. After 15 days in vivo, the mice were euthanized and the skin with the attached ribbon was removed. The skin segments were fixed (4% paraformaldehyde in phosphate-buffered saline (PBS), pH 7.2) for 48 h at room temperature and rinsed in PBS. Some tissues were processed and embedded in paraffin (via standard methods) and sectioned (8-um thick) onto slides for hematoxylin and eosin (H&E) staining (where cell nuclei are stained blue and all other cellular material is pink) or immunostaining. The Mg samples were cut with standard high-profile disposable microtome blades, but the Zn samples were cut with diamond disposable blades (both from C.L. Sturkey, Inc., Lebanon, PA). Despite the use of diamond blades, the Zn metal did cause some tissue tearing during sectioning. For tissue section immunostaining, the method was as previously described [40]. The antibodies used were specific for axons (rabbit antibody against the 200 MW neurofilament protein (NF), 1/500, Sigma-Aldrich) or blood vessels (monoclonal mouse antibodies against smooth muscle actin (SMA), 1/500, Thermo Fisher Scientific, Florence, KY). Secondary antibodies were Alexa Fluor 488 conjugated goat anti-rabbit and Alexa Fluor 594 conjugated goat anti-mouse (each at 1/500). DAPI (4',6-diamidino-2-phenylindole, 1/1000, Sigma-Aldrich) was added to the secondary antibody for nuclear staining. For whole tissue studies, the techniques were modified from published reports [41; 42]. Skin samples with metal ribbon material were rinsed after fixation (PBS) and dehydrated in a series of increasing concentrations of methanol to 100% methanol (15-30 min incubations). autofluorescence was quenched with [PERSON]'s bleach (methanol, DMSO and H\({}_{2}\)O\({}_{2}\) in ratios 4:1:1, for 2 h) then rehydrated in steps from 100% methanol to PBS, as for dehydration. Tissue was blocked for 8 h in Tris-buffered saline (0.1M Tris with 0.15M NaCl, TBS) containing 0.5% Perkin Elmer TSA blocking reagent (Thermo Fisher). The primary antibody was added and incubated for 24-72 h on a shaker. Following five 1-h washes with PBS, the secondary antibody was added at 1/500 and incubated for 24-48 h, rinsed again, and then dehydrated with increasing amounts of methanol. Tissues were then equilibrated with the clearing agent: 1:1 benzyl alcohol: benzyl benzoate, overnight, with another change the next day, which rendered the tissues transparent. Unless otherwise specified, all materials were from Thermo Fisher Scientific. Photography of the whole animal was done using a cell phone camera, while images of tissue sections were taken with either a Zeiss Axiocam digital camera (color) or with a QICam CCD camera (QImaging, Canada) (black and white), both on a Zeiss Axioplan imaging 2e fluorescence microscope. Fluorescent images taken with the QICam camera were pseudocolored and combined using Photoshop. Confocal images were taken on a Nikon A1R plus confocal on an upright FN1 microscope.