肿瘤严重威胁人类健康，转移和耐药是导致患者术后预后不佳和死亡率上升的主要原因。为了提高患者生存率，目前已有多种方法，如肿瘤组织活检、生物标志物检测以及新兴的液体活检等用于肿瘤转移和耐药研究。然而，离体组织病理检测和分子生物学验证不能反映肿瘤的真实状态。因此，建立肿瘤转移和耐药在体检测的方法对肿瘤个体化治疗是非常重要的。分子影像技术的发展为肿瘤诊疗带来了新的契机，通过在体多模态成像不仅可以准确定位肿瘤，而且可以通过药物治疗后肿瘤大小的变化评估耐药状态。虽然已经取得了一定的研究进展，但由于缺乏肿瘤特异性标志物，无法对肿瘤转移灶进行实时精准定量，并且延迟的肿瘤变化无法实时反映耐药的真实情况。因此，需要不断探索新的肿瘤转移和耐药在体检测方法。基于以上研究背景，本文首先构建了基于二氧化硅的纳米探针，实现皮下肿瘤在体检测。此基础上构建了原位转移瘤模型，实现对原位肿瘤和转移灶的定量检测。为了进一步对肿瘤耐药进行检测，构建了基于四氧化三锰的肿瘤微环境智能响应型纳米探针，对原位肿瘤耐药模型进行在体检测，并在此基础上进一步实现对耐药肿瘤的光热和化学动力学协同治疗。具体研究内容包括以下几个方面：

(1) 构建了基于二氧化硅的肿瘤在体检测纳米探针。首先合成了单分散性良好的二氧化硅纳米粒子 (SiO₂ NPs)，然后利用四唑化合物T1将多肽RGD通过光点击方法交联在SiO₂ NPs表面 (SiO₂@T1-RGDk NPs)。透射电镜图显示SiO₂ NPs呈现单分散性良好的球形结构，粒径约为50 nm。通过不同溶剂和不同温度下粒径的变化验证了SiO₂@T1-RGDk NPs良好的稳定性。通过紫外吸收光谱、荧光光谱和红外光谱进一步证明SiO₂@T1-RGDk NPs的成功合成。细胞摄取和亲和力分析结果表明SiO₂@T1-RGDk NPs具有良好的肿瘤细胞靶向性并积累在细胞质中。通过细胞毒性分析和体内急性毒性分析评估了SiO₂@T1-RGDk NPs的体内外生物安全性。以前列腺癌为肿瘤模型，通过荧光成像实现肿瘤在体检测。

(2) 构建了基于介孔二氧化硅的肿瘤转移在体检测纳米探针。首先通过水油两相反应法合成了生物可降解介孔二氧化硅纳米粒子 (bMSN NPs)，并对其表面进行氨基修饰。然后将荧光染料Cy7.5和叶酸 (FA) 交联在bMSN NPs表面 (bMSN@Cy7.5-FA NPs)。Cy7.5可作为在体荧光成像剂，FA可以特异性靶向肿瘤细胞。bMSN NPs的粒径约为100 nm，具有清晰的介孔结构。通过在不同溶剂和不同温度下粒径的变化验证了bMSN@Cy7.5-FA NPs良好的稳定性。通过紫外吸收光谱和荧光光谱进一步验证bMSN@Cy7.5-FA NPs的成功合成。细胞毒性实验结果表明bMSN@Cy7.5-FA NPs具有良好的生物安全性。细胞摄取和亲和力分析实验结果显示bMSN@Cy7.5-FA NPs能够被细胞摄取并积累在细胞质中，对肿瘤细胞具有良好的靶向性。构建胰腺癌转移瘤模型，通过在体荧光成像验证bMSN@Cy7.5-FA NPs的体内分布，实现转移瘤定量检测。根据三室模型评估bMSN@Cy7.5-FA NPs在肿瘤和肌肉的分布，结果显示肿瘤部位荧光信号快速增强，表明bMSN@Cy7.5-FA NPs具有良好的肿瘤靶向性。

(3) 构建了可用于肿瘤耐药在体检测和协同治疗的肿瘤微环境智能响应型纳米探针。首先通过热分解法合成了四氧化三锰纳米粒子 (Mn₃O₄ NPs)，表面经聚多巴胺修饰，利用四唑化合物T2通过光点击方法将胃癌多药耐药特异性多肽GMBP1交联在纳米粒子表面 (MPG NPs)。透射电镜结果显示MPG NPs粒径在10 nm以内，在不同溶剂和不同温度下均具有良好的稳定性。紫外吸收光谱和荧光光谱进一步验证了MPG NPs的成功合成。细胞摄取和亲和力分析表明MPG NPs对胃癌多药耐药细胞具有良好的靶向性。在不同pH下测定了MPG NPs的磁共振成像弛豫率，验证MPG NPs的磁共振成像性能。建立原位胃癌耐药模型，通过磁共振成像进行胃癌耐药在体检测。体内急性毒性和溶血实验结果表明MPG NPs具有良好的在体生物安全性。

(4) 进一步验证了MPG NPs对耐药胃癌的协同治疗作用。通过与谷胱甘肽 (GSH) 和过氧化氢 (H₂O₂) 的反应验证MPG NPs良好的化学动力学特性。通过不同条件下MPG NPs溶液温度变化验证其光热成像性能。通过细胞毒性、克隆形成、流式和细胞染色验证MPG NPs的肿瘤细胞抑制作用。建立原位胃癌耐药模型，验证MPG NPs的光热和化学动力学协同治疗效果，结果显示协同治疗组小鼠肿瘤逐渐变小甚至消失，表明MPG NPs具有良好的协同治疗作用。

Cancer is a serious threat to human health. Metastasis and drug resistance are the main reasons for poor postoperative prognosis and increased mortality. In order to improve the survival rate of patients, various methods, such as tumor tissue biopsy, biomarker detection, and emerging liquid biopsy, are currently used for tumor metastasis and drug resistance research. However, histopathological testing and molecular biological validation cannot reflect the true state of the tumor. Therefore, it is very important to establish a method for detection of tumor metastasis and drug resistance for individualized tumor therapy. The development of molecular imaging technology has brought new opportunities for the precise diagnosis and treatment of tumors. In vivo multimodal imaging can not only accurately locate the tumor, but also evaluate the drug resistance status through the change of tumor size after drug treatment. Although some research progress has been made, due to the lack of tumor-specific markers, it is impossible to accurately quantify tumor metastases in real time, and delayed tumor changes cannot reflect the real situation of drug resistance in real time. Therefore, it is necessary to continuously explore new methods for in vivo detection of tumor metastasis and drug resistance. Based on the above research background, a silica-based nanoprobe was constructed firstly to achieve tumor detection in vivo. On this basis, an orthotopic metastatic tumor model was constructed to achieve quantitative detection of orthotopic tumors and metastases. In order to further detect tumor drug resistance, a Mn₃O₄-based intelligent responsive nanoprobe for tumor microenvironment was constructed to detect orthotopic drug-resistant tumors. On this basis, photothermal and chemodynamic therapy of drug-resistant tumors are realized. The specific research contents include the following aspects:

(1) A silica-based nanoprobe for tumor in vivo detection was constructed. Firstly, silica nanoparticles (SiO₂ NPs) with good monodispersity were synthesized, and then the polypeptide RGD was cross-linked on the surface of SiO₂ NPs by the photo-click method using tetrazole compound T1 (SiO₂@T1-RGDk NPs). Transmission electron microscope images show that the SiO₂ NPs have a spherical structure with good monodispersity and a particle size of about 50 nm. The good stability of SiO₂@T1-RGDk NPs was verified by the change of particle size under different solvents and different temperatures. The successful synthesis of SiO₂@T1-RGDk NPs was further demonstrated by UV absorption spectroscopy, fluorescence spectroscopy and infrared spectroscopy. The results of cellular uptake and affinity analysis indicated that SiO₂@T1-RGDk NPs had good tumor cell targeting and accumulated in the cytoplasm. The in vitro and in vivo biosafety of SiO₂@T1-RGDk NPs was evaluated by cytotoxicity assay and in vivo acute toxicity assay. Taking prostate cancer as a tumor model, the tumor can be detected in vivo through fluorescence imaging.

(2) A nanoprobe for detection of tumor metastasis based on mesoporous silica was constructed. First, biodegradable mesoporous silica nanoparticles (bMSN NPs) were synthesized by a water-oil two-phase reaction method, and their surfaces were modified with amino groups. The fluorescent dye Cy7.5 and folic acid (FA) were then cross-linked on the surface of bMSN NPs (bMSN@Cy7.5-FA NPs). Cy7.5 can be used as an in vivo fluorescence imaging agent, and FA can specifically target tumor cells. The particle size of the bMSN NPs is about 100 nm with clear mesoporous structure. The good stability of bMSN@Cy7.5-FA NPs was verified by the change of particle size in different solvents and different temperatures. The successful synthesis of bMSN@Cy7.5-FA NPs was further verified by UV absorption spectroscopy and fluorescence spectroscopy. The results of cytotoxicity experiments showed that bMSN@Cy7.5-FA NPs had good biosafety. The results of cellular uptake and affinity analysis showed that bMSN@Cy7.5-FA NPs could be taken up by cells and accumulated in the cytoplasm, and had good targeting to tumor cells. A pancreatic cancer metastasis model was constructed, and the in vivo distribution of bMSN@Cy7.5-FA NPs was verified by in vivo fluorescence imaging to achieve quantitative detection of metastases. The distribution of bMSN@Cy7.5-FA NPs in tumor and muscle was evaluated according to the three-compartment model, and the results showed that the fluorescence signal at the tumor site increased rapidly, indicating that bMSN@Cy7.5-FA NPs had good tumor targeting.

(3) An intelligent responsive nanoprobe for tumor microenvironment for the in vivo detection and synergistic treatment of drug resistance was constructed. Firstly, manganese tetroxide nanoparticles (Mn₃O₄ NPs) were synthesized by thermal decomposition, and the surface was modified with polydopamine. The tetrazole compound T2 was used to cross-link the gastric cancer multidrug resistance-specific polypeptide GMBP1 on the surface of the nanoparticles by photo-click reaction (MPG NPs). Transmission electron microscopy results showed that the MPG NPs had a particle size within 10 nm and had good stability in different solvents and temperatures. The UV absorption and fluorescence spectra further verified the successful synthesis of MPG NPs. Cellular uptake and affinity analysis indicated that MPG NPs had good targeting to gastric cancer multidrug-resistant cells. The MRI relaxation rates of MPG NPs were measured at different pH to verify their MRI performance. An orthotopic gastric cancer drug resistance model was established, and the drug resistance of gastric cancer was detected in vivo by MRI. The results of in vivo acute toxicity and hemolysis experiments indicated that MPG NPs had good biosafety.

(4) The synergistic therapeutic effect of MPG NPs on drug-resistant gastric cancer was further verified. The good chemical kinetic activity of MPG NPs was verified by the reaction with glutathione (GSH) and hydrogen peroxide (H₂O₂). The photothermal effect was verified by the temperature change of MPG NPs solution under different conditions. The tumor cell inhibitory effects of MPG NPs were verified by cytotoxicity, clone formation, flow cytometry and apoptosis staining. Establish an orthotopic gastric cancer drug resistance model, and the photothermal and chemodynamic synergistic treatment effects of MPG NPs were verified. The results showed that the tumors in the synergistic treatment group gradually became smaller or even disappeared, indicating that MPG NPs have a good synergistic therapeutic effect.