This article is devoted to synthesis, identification and complex investigation of biocompatibility for graphene oxide (GO) covalent conjugate with [5-[[4,6-bis(aziridin-1-yl)-1,3,5-triazin-2-yl]amino]-2,2-dimethyl-1,3-dioxan-5-yl]methanol (Diox) cytostatic (GO-Diox). GO was synthesised using a patented modified Hummers and Offeman's method leading to the production of GO enriched with oxygen-containing functional groups (⁓85 %). Obtained nanomaterial was covalently modified with Diox, after which it was characterised using 13C NMR, Raman, and IR spectroscopy, XRD. Biocompatibility study included investigation of hemocompatibility, antioxidant activity, endocytosis, cytotoxicity. Moreover, the photothermal action of GO-Diox nanoconjugate was performed.