The present invention addresses the problem of providing a cell- or tissue-embedding device which suppress the reduction in a living cell or a living tissue, during a process for preparing a PVA gel containing the living cell or living tissue, so as to exhibit an excellent ability to supply a physiologically active substance. An aqueous gel, which is to be used for forming an immunoisolation layer of a cell- or tissue-embedding device, is prepared by using a modified polyvinyl alcohol-based resin (A) having an active carbonyl group and a crosslinking agent (B) as components thereof.本發明之課題在於：於製作含有活細胞或活體組織之PVA凝膠之製程中，藉由抑制活細胞或活體組織之減少，而供給生理活性物質之供給能力較高之細胞或組織包埋裝置。 本發明將具有活性羰基之改性聚乙烯醇系樹脂(A)及交聯劑(B)作為成分而構成用以形成細胞或組織包埋裝置之免疫隔離層的水性凝膠。
