Multistimuli-responsive PEGylated polymeric bioconjugate-based nano-aggregate for cancer therapy

Biocompatible, stimuli-responsive, intelligent and efficient drug delivery systems are essential for effectively suppressing cancer and reducing toxic side effects of chemotherapeutic drugs. Herein, two strategies have been employed to develop a N-(1,3-dihydroxypropan-2-yl) methacrylamide (DHPMA)-derived polymer carrier for doxorubicin (DOX) with a long circulation time: increasing molecular weight (MW) of the DHPMA polymer through an enzyme-responsive oligopeptide linker; and further grafting poly(ethylene glycol) (PEG) onto the polymer chain via a disulfide bond (pDHPMA-DOX-SS-mPEG), resulting in nano-aggregate. The nano-aggregate enters into 4T1 cells through multiple endocytosis pathways and DOX released in the presence of a low pH and reductive enzymes contribute to significant apoptosis by decreasing mitochondria membrane potential and disrupting actin cytoskeletons. Significantly enhanced tumor accumulation of the nano-aggregate is evidenced from ex vivo fluorescence imaging in comparison with the bioconjugate (pDHPMA-DOX) with no PEGylation. This is supported with a much longer terminal half-life time up to 16.9 h for pDHPMA-DOX-SS-mPEG, significantly higher than 10.4 h for pDHPMA-DOX and 2.7 h for free drug DOX. Accordingly, the best tumor inhibitive effect has been achieved by pDHPMA-DOX-SS-mPEG confirmed by significant reduction in tumor volumes and undetectable active proliferative cells and positive endotheliocytes from immunohistochemical staining of CD31 and Ki-67 in the 4T1 tumor tissue. The results demonstrate that increased MW through biodegradable linkers and grafted PEG significantly contribute to an extended circulation time, reduced systemic toxicity and an enhanced therapeutic efficacy. Tumor microenvironment-responsive PEGylated DHPMA-derived polymeric bioconjugate-based nano-aggregate offers the promising anti-tumor effect.

生物相容性、刺激响应性、智能且高效的药物递送系统对于有效抑制癌症以及减少化疗药物的毒副作用至关重要。在此，采用了两种策略来开发一种用于阿霉素（DOX）且具有长循环时间的由N -（1,3 - 二羟基丙 - 2 - 基）甲基丙烯酰胺（DHPMA）衍生的聚合物载体：通过一种酶响应性寡肽连接体增加DHPMA聚合物的分子量（MW）；以及通过二硫键将聚乙二醇（PEG）进一步接枝到聚合物链上（pDHPMA - DOX - SS - mPEG），形成纳米聚集体。该纳米聚集体通过多种内吞途径进入4T1细胞，并且在低pH值和还原酶存在的情况下释放的DOX通过降低线粒体膜电位和破坏肌动蛋白细胞骨架导致显著的细胞凋亡。与未进行PEG化的生物共轭物（pDHPMA - DOX）相比，体外荧光成像证明纳米聚集体在肿瘤中的积累显著增强。pDHPMA - DOX - SS - mPEG的末端半衰期长达16.9小时，这有力地支持了上述结论，其半衰期明显高于pDHPMA - DOX的10.4小时和游离药物DOX的2.7小时。因此，pDHPMA - DOX - SS - mPEG实现了最佳的肿瘤抑制效果，这通过4T1肿瘤组织中肿瘤体积显著减小以及免疫组化染色显示CD31和Ki - 67的活性增殖细胞和阳性内皮细胞无法检测到得以证实。结果表明，通过可生物降解的连接体增加分子量以及接枝PEG显著有助于延长循环时间、降低全身毒性并提高治疗效果。基于肿瘤微环境响应性PEG化DHPMA衍生的聚合物生物共轭物的纳米聚集体具有良好的抗肿瘤效果。