肿瘤免疫治疗在对抗原发性肿瘤、预防肿瘤复发和转移等方面取得了长足进展。然而，缺乏肿瘤抗原和无法有效启动适应性免疫导致免疫治疗效果不佳。焦亡是一种程序性细胞死亡途径，通过在焦亡过程中释放细胞内促炎成分和肿瘤抗原，有效促进抗肿瘤免疫。特别是，结合光热试剂和小分子药物可促进焦亡。小分子药物可以增强焦亡关键蛋白GSDME在肿瘤细胞中的表达。同时，低功率激光照射可以激活半胱天冬酶-3，将GSDME切割成GSDME-N结构域并聚集在细胞膜上形成孔，导致细胞焦亡。更为重要的是要考虑将它们准确地共同递送到肿瘤，以减少全身毒性并提高治疗效率。活细胞仿生递送系统由于其生物安全性和对肿瘤细胞的趋向性，提高了药物递送的效率、精度和递送载体的安全性。活细胞和纳米材料递送系统的结合可以实现长循环、高载药量和高靶向递送效率。在活细胞纳米递送系统中，基于体内细胞搭便车的纳米递送系统具有广阔的应用前景。内源性细胞具有生物相容性好、免疫原性低、靶向自驱动能力强等天然递送优势，避免了活细胞载体在体外的复杂制备和灭活。

受体内细胞搭便车策略的启发，我们设计了一种基于中性粒细胞搭便车的纳米载体，通过在荧光成像导航下触发焦亡来精确递送和肿瘤免疫治疗。纳米载体由负载有地西他滨（DAC）的抗CD11b和IR820偶联牛血清白蛋白纳米颗粒组成。通过将IR820锚定在纳米颗粒上，无需额外的荧光标记即可实现用于肿瘤免疫治疗的成像导航和光热增强焦亡。纳米递药系统发挥作用的过程分为中性粒细胞识别纳米粒、纳米粒随中性粒细胞到达肿瘤部位、到达肿瘤部位后纳米粒的释放和精确治疗等一系列过程。系统给药后，抗CD11b抗体可以靶向血液中活化的中性粒细胞。由于中性粒细胞对术后炎症微环境的生物趋向性，纳米载体可以通过中性粒细胞搭便车实现高效的肿瘤递送。纳米递送系统上的荧光信号分子IR820充当导航监视器，以跟踪纳米递送系统的精确传递。体内成像可以监测肿瘤部位纳米颗粒的更高蓄积，以监测血液中嗜中性粒细胞的快速循环。当纳米载体到达肿瘤区域时，带有IR820的光热控制系统使它更快得从细胞载体中释放。接着，释放的DAC上调肿瘤细胞的GSDME表达量，低剂量激光照射激活半胱天冬酶-3，引起焦亡，改善系统的适应性免疫应答，调节免疫抑制微环境，为有效的肿瘤免疫治疗，进一步在预防肺转移中发挥关键作用。

本文分为两章，从搭便车中性粒细胞递送系统的构建及体外评价、术后肿瘤复发和肺转移模型的构建及药效评价两部分对我们设计的搭便车中性粒细胞通过光热触发细胞焦亡进而增强肿瘤免疫治疗的系统进行了较为全面的评价。在第一部分中，我们通过粒径、电位以及原子力显微镜表征了纳米载药系统的大小、带电荷性质和脱水后形态及纳米粒大小分布情况。同时，通过7天内的粒径大小变化，证明了纳米载体在缓冲液中的稳定性。进一步，通过模拟肿瘤微环境中高表达还原型谷胱甘肽作为释放外液，验证了纳米载体在肿瘤微环境中的特异性释放。利用体外和体内两种状态下纳米载体搭便车中性粒细胞的效率验证了CD11b抗体能够有效靶向术后激活的中性粒细胞并在肿瘤部位蓄积。接着，在第二部分中，通过对术后复发模型中肿瘤组织中蛋白的表达证明了我们设计的载药系统在低剂量激光照射下能够有效触发肿瘤细胞焦亡。通过对肿瘤微环境中的免疫细胞分析，证明了搭便车中性粒细胞的纳米载体通过光热触发肿瘤细胞焦亡能够发挥增强肿瘤免疫的效果。

Tumor immunotherapy has made great strides, fighting primary tumors and preventing tumor recurrence and metastasis. However, the lack of tumor antigens and the inability to effectively initiate adaptive immunity has led to poor immunotherapy. Pyroptosis is a programmed cell death pathway that effectively promotes anti-tumor immunity by releasing intracellular pro-inflammatory components and tumor antigens during the process of pyroptosis. In particular, a combination of photothermal reagents and small molecule drugs can promote pyroptosis. Small molecule drugs can enhance the expression of GSDME, a key protein for pyroptosis, in tumor cells. At the same time, low-power laser irradiation can activate caspase-3, which cleaves GSDME into the GSDME-N structural domain and accumulates in the cell membrane to form pores, leading to cellular pyroptosis. It is even more important to consider their precise co-delivery to the tumor to reduce systemic toxicity and improve therapeutic efficiency. Live cell bionic delivery systems improve the efficiency, precision and safety of the delivery vehicle due to their biosafety and bio-tropism towards tumor cells. The combination of live cells and nanomaterial delivery systems allows for long cycling, high drug loading and targeted delivery efficiency. Among the living cell nano-delivery systems, nano-delivery systems based on cell-hitchhiking in vivo have promising applications. Endogenous cells have natural delivery advantages such as good biocompatibility, low immunogenicity and high targeting self-driving ability, avoiding the complex preparation and inactivation of live cell carriers in vitro.

Inspired by hitchhiking strategies, we designed a neutrophil hitchhiking-based nanocarrier for precise delivery and tumor immunotherapy by triggering pyroptosis under fluorescent imaging navigation. The nanocarrier consists of anti-CD11b antibody and IR820 coupled bovine serum albumin nanoparticles loaded with decitabine (DAC). By anchoring IR820 to the nanoparticles, imaging navigation and photothermally enhanced pyroptosis for tumor immunotherapy can be achieved without additional fluorescent labelling. The nano-delivery system works through a series of processes including recognition of the nanoparticles by neutrophils, arrival of the nanoparticles at the tumor site with the neutrophils, release of the nanoparticles at the tumor site and precise treatment. After systemic administration, anti-CD11b antibodies can target activated neutrophils in the blood. Due to the bio-tropism of neutrophils to the post-operative inflammatory microenvironment, the nanocarriers can hitchhike through the neutrophils to achieve efficient tumor delivery. The fluorescent signal molecule IR820 on the nano-delivery system acts as a navigation monitor to track the precise delivery of the nano-delivery system. In vivo imaging allows monitoring of higher accumulation of nanoparticles at the tumor site to monitor the rapid circulation of neutrophils in blood. When the nanocarrier reaches the tumor area, a photothermal control system with IR820 allows it to be released more rapidly from the cell carrier. The released DAC then up-regulates GSDME expression in the tumor cells and low dose laser irradiation activates caspase-3, causing pyroptosis, improving the adaptive immune response of the system and modulating the immunosuppressive microenvironment for effective tumor immunotherapy, further playing a key role in the prevention of lung metastasis.

This paper is divided into two chapters to provide a comprehensive evaluation of our designed hitchhiking neutrophil delivery system that enhances tumor immunotherapy by photothermal triggered pyroptosis, from the construction and in vitro evaluation of the hitchhiking neutrophil delivery system, and efficacy evaluation of the postoperative tumor recurrence and lung metastasis. In the first part, we characterized the size, electric potential, morphology of the nanodrug delivery system and nanoparticle size distribution. The stability of the nanocarriers in the buffer was demonstrated by the change in particle size over 7 days. Further, the specific release of nanocarriers in the tumor microenvironment was verified by simulating the high expression of reduced glutathione in the tumor microenvironment as the release fluid. The efficiency of nanocarrier hitchhiking neutrophils in both in vitro and in vivo states was used to verify that the CD11b antibody can effectively target postoperatively activated neutrophils. Then, in the second part, the ability of our designed drug delivery system to effectively trigger tumor cell scorching under low dose laser irradiation was demonstrated by protein expression in tumor tissues in a post-operative recurrence model. By analyzing immune cells in the tumor microenvironment, it was demonstrated that the nanocarriers by hitchhiking neutrophils can enhance tumor immunity through photothermal triggered tumor cell pyroptosis.