Lyu Xiangxue, Zhang Qiufen, Liang Dehai, Huang Yanbin
Key Laboratory of Advanced Materials (MOE), Department of Chemical Engineering, Tsinghua University, Beijing 100084, China.
College of Chemistry & Molecular Engineering, Peking University, Beijing 100871, China.
Acta Pharm Sin B. 2019 Jan;9(1):186-193. doi: 10.1016/j.apsb.2018.08.001. Epub 2018 Aug 7.
Currently there is no successful platform technology for the sustained release of protein drugs. It seems inevitable to specifically develop new materials for such purpose, and hence the understanding of protein-material interactions is highly desirable. In this study, we synthesized cholesterol-grafted polyglutamate (PGA--Chol) as a hydrophobically-modified polypeptide, and thoroughly characterized its interaction with a model protein (human serum albumin) in the aqueous solution by using circular dichroism, fluorescence methods, and light scattering. With the protein concentration fixed at 5 μmol/L, adding PGA--Chol polymers into the solution resulted in continuous blue shift of the protein fluorescence (from 339 to 332 nm), until the polymer molar concentration reached the same value as the protein. In contrast, the un-modified polyglutamate polymers apparently neither affected the protein microenvironment nor formed aggregates. Based on the experimental data, we proposed a physical picture for such protein-polymer systems, where the polymer first bind with the protein in a 1:1 molar ratio a fraction of their hydrophobic pendant cholesterol resides along the polymer chain. In this protein/polymer complex, there are excess unbound cholesterol residues. As the polymer concentration increases, the polymers form multi-polymer aggregates around 200 nm in diameter the same hydrophobic cholesterol residues. The protein/polymer complex also participate in the aggregation their excess cholesterol residues, and consequently the proteins are encapsulated into the nanoparticles. The encapsulation was also found to increase the thermal stability of the model protein.
目前，尚无成功的蛋白质药物缓释平台技术。专门为此目的开发新材料似乎是不可避免的，因此，对蛋白质与材料相互作用的理解非常必要。在本研究中，我们合成了胆固醇接枝聚谷氨酸（PGA-Chol）作为疏水改性多肽，并通过圆二色性、荧光方法和光散射，全面表征了其在水溶液中与模型蛋白（人血清白蛋白）的相互作用。将蛋白质浓度固定在5 μmol/L，向溶液中加入PGA-Chol聚合物会导致蛋白质荧光持续蓝移（从339 nm到332 nm），直到聚合物摩尔浓度达到与蛋白质相同的值。相比之下，未改性的聚谷氨酸聚合物显然既不影响蛋白质微环境，也不形成聚集体。基于实验数据，我们提出了这样一个蛋白质-聚合物体系的物理模型：聚合物首先以1:1摩尔比与蛋白质结合，其一部分疏水侧链胆固醇沿聚合物链分布。在这种蛋白质/聚合物复合物中，存在过量未结合的胆固醇残基。随着聚合物浓度增加，聚合物形成直径约200 nm的多聚合物聚集体，这些聚集体含有相同的疏水胆固醇残基。蛋白质/聚合物复合物也会因其过量的胆固醇残基参与聚集体形成，结果蛋白质被包裹进纳米颗粒中。还发现这种包裹增加了模型蛋白的热稳定性。
