Injectable polypeptide-polysaccharide depot for preventing postoperative tumor recurrence by concurrent chemotherapy and brachytherapy.

Chemotherapy and radiotherapy in combination with sequence regimens are recognized as the current major strategy for suppressing postoperative tumor recurrence. However, systemic side effects and poor in-field cooperation of the two therapies seriously impair the therapeutic efficacy of patients. The combination of brachytherapy and chemotherapy through innovative biomaterials has proven to be an important strategy to achieve synergistic effects of radiotherapy and chemotherapy in-time and in-field. However, for postoperative chemoradiotherapy, as far as we know, there are few relevant reports. Herein, an injectable pH-responsive polypeptide-polysaccharide depot for concurrent chemotherapy and brachytherapy was developed by encapsulating vincristine into iodine-125 radionuclide labeled hydrogel. This depot hydrogel was prepared by dynamic covalent bonds of Schiff base between aldehydeated hyaluronic acid and polyethylene glycol-polytyrosine. Therefore, this hydrogel enables smart response to tumor acidic microenvironment, rapid release of the encapsulated vincristine and an enhanced uptake effect by tumor cells, which significantly reduces IC of vincristine for the anaplasia Wilms' tumor cells . This depot hydrogel shows excellent stability and biocompatibility, and maintains for 14 days after injection in a postoperative model of anaplasia Wilms' tumor. After injection at the cavity of tumor excision, responsively-released vincristine and the radioactive iodine-125 exerted excellent killing effects on residual tumor cells, inhibiting tumor relapse and liver metastasis of the recurrent tumor. Hence, this study proposes an effective therapeutic strategy for inhibiting anaplasia Wilms' tumor recurrence, which provides a new approach for concurrent postoperative chemo-radiotherapy and a desirable guidance in regimen execution of pediatric refractory tumors.