Preparation of Bi-based hydrogel for multi-modal tumor therapy

Radiotherapy (RT) is becoming a pervasive therapeutic pattern in clinical cancer therapy. However, the hypoxic microenvironment of tumors has a strong resistance to radiotherapy and could lead to a potential recurrence and metastasis after the treatment. Therefore, the use of synergistic strategies for improving and supplementing the RT efficiency is important. Herein, a novel Bi₂S₃/alginate (ALG) hydrogel containing tirapazamine (TPZ) was designed for the effective suppression of tumor recurrence, by introducing Bi³⁺ into the ALG, Na₂S and TPZ solution. In this formulation, Bi³⁺ was used to crosslink with the ALG to form the hydrogel and react with S^2- to simultaneously form Bi₂S₃ nanoparticles in the hydrogel matrix. The resulting Bi₂S₃ nanoparticles not only exhibit the superb radiosensitization effect to boost the effective eradication of tumors during RT but also manifest an excellent photothermal transforming performance for tumor hyperthermia and computed tomography (CT) imaging capacity for tumor monitoring. Furthermore, the RT caused hypoxia could activate the reductive prodrug TPZ and enhance its therapeutic efficiency. The reported hydrogel system provides an efficient and safe therapeutic strategy for current local tumor therapy.