肿瘤信号分子触发化学发光/超声双模成像和光动力治疗的新型纳米探针研究

Most of the present theranostic nanoprobes suffer from low specificity, limited theranosic precision and overreliance on the external stimulus and reporters. To resolve this problem, we will design a novel nanohybrid, which can regulate the tumor signal expression and use them for long-term chemiluminescent/ultrasonic dual-modal imaging and self-photodynamic therapy of tumor, without the help of the external stimulus and reporters. The peroxyoxalate (CPPO), chlorins e6 (Ce6) and CaO2 nanoparticles are packed inside the nanohybrid whose surface is coated with a layer of calcium phosphate (CaP), and the CaP outlayer is further modified with tumor targeting ligand. After targeted accumulation in the tumor site, the CPPO in the nanohybrid can be oxidized by the abnormally overproduced H2O2 to form a high-energy intermediate that transfers its energy to the coembedded nearby Ce6 molecules to generate near infrared fluorescence and singlet oxygen, accompanied with the degradation of intermediate to produce CO2 which can be used as a ultrasonic contrast; CaO2 can generate a large amount of exogenous H2O2 to amplify the imaging and therapy efficacy. CaP can prevent CPPO from premature hydrolysis, as well as improve the nanohybrid stability. In this work, the selectivity of imaging and therapy efficacy of the nanohybrid in the cancer cells and the tumor site will be investigated both in vitro and in vivo, respectively. Furthermore, we will systematically study the bio-distribution and metabolism in major organs of our nanohybrid, and evaluate its toxicity. Therefore, this project might provide new strategy for cancer “visualized healthcare”.

目前大多数“诊疗一体化”纳米探针在肿瘤部位的特异性不强，诊疗精准度不高并且严重依赖外界刺激源和报告源。为此，本项目拟合成一种不需要外界刺激源和报告源，可直接对肿瘤信号分子进行调控并加以利用，实现持续化学放光和超声造影，同时具有自发产生光动力治疗效果的多功能纳米粒。Nanohybrid内部包埋过氧化草酸酯（CPPO），二氢卟吩（Ce6）和CaO2纳米粒，外部包覆一层磷酸钙（CaP），表面含有肿瘤靶向基团。Nanohybrid靶向富集到肿瘤部位后，在其内部高丰度H2O2作用下，CPPO氧化生成高能中间体并将能量转移给Ce6，激发Ce6产生近红外荧光和单线态氧，同时高能中间体分解产生的CO2气体用于超声造影；CaO2可通过在癌细胞内生成大量外源性H2O2来提高成像和治疗效果；CaP可防止CPPO过早水解并提高纳米复合物的稳定性。本研究的顺利实施可为癌症的“可视化治疗”提供新思路。

针对目前大多数“诊疗一体化”纳米探针存在的特异性不强、诊疗准确度不高、严重依赖外界刺激源和报告源等问题，本研究探索了一种不需要外界刺激源和报告源，可直接利用肿瘤部位H2O2这种特异信号分子，实现化学发光成像和自发光动力的“诊疗一体化”纳米探针；克服目前光学成像和光动力治疗因为外界激发光源穿透深度的限制，不能用于深层肿瘤的诊断和治疗的问题，为癌症的“可视化”治疗提供一种新思路。在本研究中，我们利用叶酸修饰的纳米胶束内部包埋过氧化草酸酯（CPPO），半导体聚合物（PFPV）和四苯基卟啉（TPP），合成了一种多功能纳米探针。当纳米探针通过肿瘤细胞表面叶酸受体介导的内吞作用进入肿瘤细胞后，细胞内H2O2 与 CPPO 反应并将能量转移给PFPV，进而PFPV发光激发TPP产生近红外荧光和单线态氧，实现化学发光成像和光动力治疗功能。该纳米探针灵敏度极高，对生理浓度H2O2（1-10 μM）也可进行有效探测。尾静脉注射后，纳米探针在小鼠肿瘤部位产生化学发光信号，且较荧光成像信号的背景干扰更低，特异性更强，同时可有效抑制肿瘤组织生长。利用单个纳米粒子内CPPO、PFPV、TPP之前的能量传递接力策略，实现了肿瘤区域的化学发光成像和自发光动力治疗，为未来临床上光学成像和光动力治疗提供了新思路。