近红外光动力癌症诊疗聚合物纳米粒子的合成与性能

Theranostics, combing both diagnostics and therapeutics, have attracted much attention for its potential application in personalized medicine. As an emerging interdiscipline, it is related to but different from traditional imaging and therapeutics. It embraces the efforts of utilizing multiple techniques to arrive at a comprehensive imaging/therapy regimen. Recently, light-triggered theranostics have received special attention due to the advantage of highly specific spatial and temporal control of compound release. Photodynamic therpy (PDT) is an potential theranostic method for cancer treatment. PDT uses a drug knowm as a photosensitizer (PS), light, and oxygen to destroy tumors and their surrounding vasculature due to the foamtion of reactive oxygen species (ROS), especially the singlet oxygen. Meanwhile, upon light activation,PS can emit fluorescence , and which can be employed for locating diseases, photodiagnosis and molecular imaging. In biomedical applications, the utilization of dyes that absorb and fluoresce in the near-infrared (NIR) range (600-1000 nm) takes the advantage of spectral coincidence with the tissue transparent window where minimal photon interferences (absorption, autofluorescence,and scattering) from solvents, biomolecules, and the biological matrix allow for deeper light penetration. Combing the NIR fluorescence and PDT, the NIR PDT theranostic regents could be highly advantageous to treat deeply seated tumors and monitor the treatment response. However, the PSs are generally hydrophobic and nanocarriers should be developed to delivery suitable dose of PSs into tussue and cell. In addition, trageted ligand should added onto the nanocarriers to make them access selectively to the tumor tissue or cancer cell. Here, in the proposal, biocompatible/biodegradable polypeptides will be synthesized by controlled polymerization, and micelles or nanogel are the target nanostructure. Spectic trageting F3 peptide or folic acid should be added, and NIR derivatives of Cy7,7 and/or photosensitizers (porfin or BODIPY) should be conjugated to the nanocarriers to prepare the target nanoparticles for NIR PDT and imaging synchronously. Then cell and small animal experiments should be carried out to study the properties of the nanoparticles for cancer theranostics.

光动力治疗(PDT)是采用光激发光敏剂并与氧结合产生反应性氧基团，使癌细胞死亡的方法。该方法的优点是普适性强，光敏剂毒性受激可控，毒副作用小。但在使用时存在以下问题:1)光敏剂通常是憎水的，如何高效靶向地输运到肿瘤是个问题；2)大部分光敏剂的激活光在可见光区，不利于组织透过，且易造成皮肤与组织的损伤,应发展近红外PDT；3)目前的应用仍以治疗为主，缺乏诊断或示踪，应发展光动力诊疗(theranostics)。为此本项目拟合成以生物相容性/可降解的聚多肽为主体骨架的两亲性多嵌段共聚物或纳米凝胶为光敏剂的高分子纳米载体、以叶酸或F3-多肽为靶向基团、以卟吩类化合物或BODIPY衍生物为近红外光敏剂、或以普通光敏剂与近红外高效发光的Cy7,7化合物体系结合，制备新型的近红外光动力诊疗靶向聚合物纳米粒，并研究其在细胞与活体中的输运与肿瘤治疗中的应用，发展新型的近红外光动力诊疗体系。

光动力治疗(PDT)是采用光激发光敏剂并与氧结合产生高能量单线态氧等ROS基团，原位杀生癌细胞的方法。该方法的优点是普适性强，光敏剂毒性受激可控，毒副作用小。本项目针对目前光动力治疗中存在的光敏剂憎水性强、难以直接使用；大部分光敏剂为可见光区，难以组织透过；仍要与抗癌药物同时使用及难以示踪等问题，提出了采用生物相容及可降解特的聚多肽为骨架，以近红外光敏剂为核心，同时具备成像与光动力治疗行为，希望发展出新的光动力诊疗纳米体系。在项目执行过程中，严格依照计划书，开展了一系列系统的研究，实现的预定目标，取得了一系列有价值的成果，包括：1）近红外光敏剂的合成：合成了溴代IR808为代表的Cy7,7分子、高单线态氧产率的BODIPY-Br2型近红外发光光敏剂，这两类光敏剂均同时具备近红外发光的单线态氧产生功能，在此基础上进一步合成了具有化学活性的BODIPY-Br2型光敏剂，更易于与高分子形成缀合物；2）多种聚多肽基功能高分子纳米粒子的合成：分别合成了半乳糖靶向的PEG化大分子RAFT引发剂，及多嵌段两亲共轭高分子；设计并合成了IR808-Br2负载的靶向近红外聚多肽纳米凝胶；通过结合开环聚合、自由基聚合、Click反应的手段合成出了分别具有半乳糖及叶酸靶向的pH响应三嵌段共聚物；设计合成了两亲性pH敏感的聚合物载体；合成了超pH敏感的聚多肽纳米体系；3）近红外成像诱导的光动力治疗：研究了多种聚合物体系的细胞毒性与降解特性，采用激光共聚焦显微镜研究了其在细胞中的内吞及选择性结合的过程示踪。采用in vivo实验进行了小鼠实际光动力治疗的效果，发现得到的聚合物纳米粒子体系具备优异的生物相容性，且具备优异的谷胱甘肽还原崩解或pH响应特性，可以在其肿瘤微环境或者进入细胞后迅速崩解，释放出内含的近红外光敏剂，在近红外光作用下，实现高效光动力治疗，同时过程可以被近红外光跟踪。总而言之，项目按照计划得到了较为完美的执行，达到了预期的目标，为下一步性能更好智能化近红外光动力纳米诊疗体系的发展奠定了坚实的基础。