PROBLEM TO BE SOLVED: To obtain the subject material intended for preparing such a site including a sensor-embedding site as to enable cell transplantation or transplanted cell removal to be easily conducted when needed through making a void enclosed by capillaries when embedded.
SOLUTION: This material for forming a neovascular bed is obtained for the purpose of preparing a void enclosed by a capillary-rich tissue and enabling cells to be transplanted or a sensor to be embedded therein through embedding this material there (in the tissue). It is preferable that this material has a material base (e.g. a bag made of hydrogel, polymeric membrane or inorganic material) and a neovascular-inducing factor capable of making abundant capillaries (e.g. vascular epithelial cell growth factor, basic fibroblast growth factor, acidic fibroblast growth factor, blood platelet-derived growth factor, transforming growth factor-4, osteonectin, angiopoietin 1 and 2) and the neovascular-inducing factor lies under a sustained release condition.