ObjectiveTo design and synthesize a novel permeable hydrogel loaded with a radiation agent for the implantation radiotherapy of tumors.

MethodsThe polymer PECT-RGDPECT:poly(ε-caprolactone-co-1, 4, 8-trioxa4.6spiro-9-undecanone)-poly(ethylene glycol)-poly(ε-caprolactone-co-1, 4, 8-trioxa4.6spiro-9-undecanone); RGD:Arg-Gly-Asp was synthesized by esterification reaction, and an ¹³¹I-labeled hyaluronic acid was prepared by amidation reaction and chloramine-T method. The chemical structure of them was characterized by ¹H-NMR, and the ¹³¹I-labeled hyaluronic acid was isolated and purified by precipitation and centrifugation. Hydrogel formation was verified by vial flipping experiment, and the cytotoxicity of the polymer materials was evaluated by MTT assay. The in vivo stability and degradation of the injected hydrogel were studied using a radioactive small animal live imaging system. The in vivo antitumor effect of the ¹³¹I@PECT-RGD hydrogel was investigated by inhibiting tumor growth volume and tumor tissue section.

ResultsThe polymer PECT-RGD was non-cytotoxic and could form a stable hydrogel under the normal physiological temperature(37℃). This hydrogel is capable of self-degradation in vivo. Compared with the PBS group, the ¹³¹I@PECT-RGD hydrogel and the ¹³¹I@PECT gel showed significantly higher anti-tumor efficiency (P < 0.05, F=71.968). A significant difference in anti-tumor efficiency was found between the ¹³¹I@PECT and ¹³¹I@PECT-RGD hydrogels (P < 0.05, t=7.276). No significant difference in body weight was found among the three groups (P > 0.05, F=3.878). HE staining showed that only a small part of the tumor tissue was necrotic in the PBS group, whereas a large part of the tumor tissue was necrotic in the ¹³¹I@PECT group; the tumor tissue of the ¹³¹I@PECT-RGD group was generally necrotic.

ConclusionsThe ¹³¹I@PECT-RGD hydrogel could be injected into tumor tissue in situ and display great biocompatibility, self-degradation ability, and anti-tumor activity. Thus, this hydrogel has potential applications in local radiotherapy.