Enhanced localized therapeutic precision: A face-to-face folate-targeted Cu2+-mediated nanotherapy with thermosensitive sustained-release system.

Safe and effective Cu2+ supplementation in local lesion is crucial for minimizing toxicity of DSF-based chemotherapy. Targeted delivery of Cu2+ appears more promising. Intraperitoneal chemotherapy for peritoneal carcinoma (PC) establishes "face-to-face" contact between targeted nanocarriers and tumor tissue. Herein, this study developed a biodegradable, injectable thermosensitive hydrogel that coencapsulating DSF submicroemulsion (DSF-SE) and folate-modified liposome loading glycyrrhizic acid-Cu (FCDL). FCDL acted as 'beneficial horse' to target the tumor-localized folate receptor, thus liberating Cu2+ in tumor nidus. The prepared FCDL and DSF-SE were found with uniform sizes (160.2 nm, 175.4 nm), low surface charge (-25.77 mV, -16.40 mV) and high encapsulation efficiency (97.93 %, 90.08 %). In vitro drug release profile of FCDL, DSF-SE and FCDL＆DSF-SE@G followed a sustained release pattern. And the release behavior of Cu2+ from FCDL was pH-related, i.e., Cu2+ was released faster under acidic condition. When FCDL and DSF-SE were loaded into an PLGA-PEG-PLGA-based hydrogel system, FCDL＆DSF-SE@G was formed to ensure separated delivery of Cu2+ and DSF in space but synchronized release over time. The rheology experiment showed a satisfactory gelling temperature of 32.7 °C. In vitro cytotoxicity study demonstrated that FCDL＆DSF-SE@G significantly lowered the IC50 of free Cu2+/DSF, Cu2+/DSF hydrogel and non-targeted analogue by almost 70 %, 65 % and 32 %, respectively. Accordingly, in tumor-bearing mice, FCDL＆DSF-SE@G augmented the tumor inhibition rates for the same formulations by 352 %, 145 % and 44 %, respectively. The main mechanism was attributed to higher uptake of FCDL and DSF-SE, resulting in increased Cu(DDTC)2 formation, ROS production and cell apoptosis. In conclusion, this targeted nanotherapy approach with dual-nanocarriers loaded hydrogel system, with its focus on face-to-face contact between nanocarriers and tumor tissues in the peritoneal cavity, holds significant promise for intraperitoneal chemotherapy in PC.