In vivo TiTannic hydrogel injection. 100 µL of a sterile preparation of TiTannic hydrogel was injected under aseptic conditions. Mice were anaesthetized using 2% isofluorane and hair was removed from a < 1 cm 2 area on both flanks and treated with Betadine surgical scrub (Fisher Scientific, UK) before injection. TiTannic hydrogels were injected subcutaneously using a sterile 25gauge hypodermic needle. Mice were maintained under general anesthesia for a total of 10 minutes to allow the gel to form homogenously. Recovery was monitored closely until the mice moved freely and were observed to start feeding again. TiTannic hydrogel with the surrounding skin and subcutaneous adipose tissue layer as well as tissue for Ti detection were isolated after schedule 1 culling of the mice at defined time points.