State Key Laboratory of Applied Organic Chemistry, Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou 730000, China.
Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study & Department of Pharmacy and Pharmacology, University of South China, Hengyang 421001, China.
Molecules. 2022 May 7;27(9):3016. doi: 10.3390/molecules27093016.
Bottlebrush copolymers with different chemical structures and compositions as well as diverse architectures represent an important kind of material for various applications, such as biomedical devices. To our knowledge, zwitterionic conjugated bottlebrush copolymers integrating fluorescence imaging and tumor microenvironment-specific responsiveness for efficient intracellular drug release have been rarely reported, likely because of the lack of an efficient synthetic approach. For this purpose, in this study, we reported the successful preparation of well-defined theranostic zwitterionic bottlebrush copolymers with unique brush-on-brush architecture. Specifically, the bottlebrush copolymers were composed of a fluorescent backbone of polyfluorene derivate (PFONPN) possessing the fluorescence resonance energy transfer with doxorubicin (DOX), primary brushes of poly(2-hydroxyethyl methacrylate) (PHEMA), and secondary graft brushes of an enzyme-degradable polytyrosine (PTyr) block as well as a zwitterionic poly(oligo (ethylene glycol) monomethyl ether methacrylate-co-sulfobetaine methacrylate) (P(OEGMA--SBMA)) chain with super hydrophilicity and highly antifouling ability via elegant integration of Suzuki coupling, NCA ROP and ATRP techniques. Notably, the resulting bottlebrush copolymer, PFONPN--(PHEMA--(PTyr--P(OEGMA--SBMA))) (P) with a lower MW ratio of the hydrophobic side chains of PTyr and hydrophilic side chains of P(OEGMA--SBMA) could self-assemble into stabilized unimolecular micelles in an aqueous phase. The resulting unimolecular micelles showed a fluorescence quantum yield of 3.9% that is mainly affected by the pendant phenol groups of PTyr side chains and a drug-loading content (DLC) of approximately 15.4% and entrapment efficiency (EE) of 90.6% for DOX, higher than the other micelle analogs, because of the efficient supramolecular interactions of π-π stacking between the PTyr blocks and drug molecules, as well as the moderate hydrophilic chain length. The fluorescence of the PFONPN backbone enables fluorescence resonance energy transfer (FRET) with DOX and visualization of intracellular trafficking of the theranostic micelles. Most importantly, the drug-loaded micelles showed accelerated drug release in the presence of proteinase K because of the enzyme-triggered degradation of PTyr blocks and subsequent deshielding of P(OEGMA--SBMA) corona for micelle destruction. Taken together, we developed an efficient approach for the synthesis of enzyme-responsive theranostic zwitterionic conjugated bottlebrush copolymers with a brush-on-brush architecture, and the resulting theranostic micelles with high DLC and tumor microenvironment-specific responsiveness represent a novel nanoplatform for simultaneous cell image and drug delivery.
具有不同化学结构和组成以及不同结构的瓶刷共聚物是一类用于各种应用的重要材料，例如生物医学设备。据我们所知，将荧光成像与肿瘤微环境特异性响应相结合的两性离子共轭瓶刷共聚物用于高效的细胞内药物释放的研究很少，这可能是由于缺乏有效的合成方法。为此，在本研究中，我们成功制备了具有独特刷状结构的具有治疗作用的两性离子瓶刷共聚物。具体而言，瓶刷共聚物由具有荧光共振能量转移的聚芴衍生物（PFONPN）荧光主链、聚（2-羟乙基甲基丙烯酸酯）（PHEMA）一级刷和可酶降解的聚酪氨酸（PTyr）块的二级接枝刷组成，以及两性离子聚（聚（乙二醇）单甲醚甲基丙烯酸酯-co-磺酸甜菜碱甲基丙烯酸酯）（P（OEGMA-SBMA））链，该链通过优雅的Suzuki 偶联、NCA ROP 和 ATRP 技术具有超亲水性和高度抗污能力。值得注意的是，所得的瓶刷共聚物 PFONPN-（PHEMA-（PTyr-P（OEGMA-SBMA）））（P）具有较低的疏水性 PTyr 侧链和亲水性 P（OEGMA-SBMA）侧链的 MW 比，可在水相中自组装成稳定的单分子胶束。所得单分子胶束的荧光量子产率为 3.9%，主要受 PTyr 侧链上的邻位酚基团和 DOX 的载药量（DLC）约 15.4%和包封效率（EE）90.6%的影响，这高于其他胶束类似物，因为 PTyr 块与药物分子之间的π-π堆积的有效超分子相互作用，以及适度的亲水性链长。PFONPN 主链的荧光能够与 DOX 发生荧光共振能量转移（FRET），并可视化治疗性胶束的细胞内转运。最重要的是，由于蛋白酶 K 触发的 PTyr 块降解以及随后的 P（OEGMA-SBMA）冠状物失屏蔽导致胶束破坏，载药胶束在存在蛋白酶时表现出加速的药物释放。总的来说，我们开发了一种有效的方法来合成具有 brush-on-brush 结构的酶响应治疗性两性离子共轭瓶刷共聚物，所得具有高 DLC 和肿瘤微环境特异性响应的治疗性胶束是一种用于同时进行细胞成像和药物递送的新型纳米平台。
