摘要Nuclear safety is a global growing concern,where ionizing radiation(IR)is a major injury factor resulting in serious damage to organisms.The detection of IR is usually conducted with physical dosimeters;however,biological IR detection methods are deficient.Here,a living composite hydrogel consisting of engineered bacteria and gelatin/sodium alginate was 3D-printed for the biological detection of IR.Three strains of PrecA::egfp gene circuit-containing engineered Escherichia coli were constructed with IR-dependent fluorescence,and the DH5α strain was finally selected due to its highest radiation response and fluorescence.Engineered bacteria were loaded in a series of gelatin/sodium alginate matrix hydrogels with different rheology,3D printability and bacterial applicability.A high-gelatin-content hydrogel containing 10%gelatin/1.25%sodium alginate was optimal.The optimal living composite hydrogel was 3D-printed with the special bioink,which reported significant green fluorescence under γ-ray radiation.The living composite hydrogel provides a biological strategy for the detection of environmental ionizing radiation.