Specific tumor-targeted gene delivery remains an unsolved therapeutic issue due to aberrant vascularization in tumor microenvironment (TME). Some bacteria exhibit spontaneous chemotaxis toward the anaerobic and immune-suppressive TME, which makes them ideal natural vehicles for cancer gene therapy. Here, we conjugated ZIF-8 metal-organic frameworks encapsulating eukaryotic murine interleukin 2 (Il2) expression plasmid onto the surface of VNP20009, an attenuated Salmonella typhimurium strain with well-documented anti-cancer activity, and constructed a TME-targeted Il2 delivery system named Il2/ZIF-8@Salmonella. Both in vitro and in vivo experiments demonstrated that Il2/ZIF-8@Salmonella maintained the tumor-targeting feature of bacteria, and could be effectively phagocytosed by intratumoral macrophages, thus leading to the expression and secretion of IL2 in TME. The detailed analysis of tumor immune microenvironment (TIME) showed that one dose of combinatorial Il2/ZIF-8@Salmonella achieved synergistic actions on a potent remodeling of TIME, marked by the activation of cytotoxic T cells and M1-polarization of macrophages in TME, thus leading to significant anti-tumor effects in melanoma, orthotopic hepatocellular carcinoma, and pulmonary metastasis models. More importantly, Il2/ZIF-8@Salmonella exhibited high safety to major organs and hematopoietic systems. Taken together, we report a novel plasmid/ZIF-8@Salmonella system that simultaneously achieves effective TME-targeted delivery of therapeutic gene, as well as synergistic re-activation of TIME.

Objective:To compare the efficacy of 3D-printed guide plate assisted versus freehand placement of cannulated screws for the treatment of Sanders type II and III calcaneal fractures.Methods:A retrospective cohort study was conducted to analyze the clinical data of 29 patients with Sanders type II and III calcaneal fractures admitted to Chonggang General Hospital from June 2020 to October 2022. Among them, there were 18 males and 11 females, with an age range of 22-69 years [(40.1±11.5)years]. Nineteen patients were treated with individualized 3D-printed guide plate assisted placement of cannulated screws (3D-printed group) and 10 were treated with freehand placement of cannulated screws (freehand group). The surgical time, fluoroscopy times, postoperative 6-month calcaneal morphology (length, width, height, B?hler angle and Gissane angle), and American Orthopedic Foot and Ankle Society (AOFAS) ankle-hindfoot score and Maryland functional score assessed at 3, 6 months after operation and at the final follow-up were compared between the two groups. The incision healing and complications were observed.Results:The patients were followed up for 6-24 months [(11.3±2.5)months]. The surgical time and fluoroscopy times in the 3D-printed group were (53.4±9.1)minutes and (7.3±1.1)times, respectively, which were shorter than (90.2±16.0)minutes and (16.0±3.2)times in the freehand group (all P<0.01). At 6 months after operation, there was no significant difference in calcaneal length between the two groups ( P>0.05); the calcaneal width, height, B?hler angle and Gissane angle in the 3D-printed group [(34.0±1.8)mm, (47.2±1.6)mm, (27.8±1.0)°, (129.2±2.8)°] were superior than those in the freehand group [(37.5±2.0)mm, (43.0±2.7)mm, (25.8±1.5)°, (125.9±2.5)°] (all P<0.01). At 3, 6 months after operation and at the final follow-up, the values of AOFAS ankle-hindfoot score in the 3D-printed group [(72.2±2.3)points, (79.7±2.3)points, (86.5±4.4)points] were higher than those in the freehand group [(64.2±6.9)points, (73.4±4.2)points, (81.8±3.1)points] (all P<0.05); the values of Maryland score in the 3D-printed group [(71.4±7.7)points, (84.7±2.6)points, (91.5±2.5)points] were higher than those in the freehand group [(65.2±5.6)points, (79.1±3.8)points, (87.1±2.9)points] (all P<0.05). All surgical incisions were healed in stage I. In the 3D-printed group, there were no complications regarding infection, iatrogenic vascular or nerve injury, or fixation failure after surgery. In the freehand group, one patient with lateral sural cutaneous nerve injury was resolved spontaneously without specific treatment. Conclusion:Compared with freehand placement of cannulated screws, 3D-printed guide plate assisted placement of percutaneous placement has the advantages of shorter surgical time, fewer fluoroscopy times, lower reduction loss, better ankle joint function recovery, and less complications in treating Sanders type II and III calcaneal fractures.