Ghosh Arijit, Buettner Christian J, Manos Aaron A, Wallace Ashley J, Tweedle Michael F, Goldberger Joshua E
Department of Chemistry and Biochemistry and ‡Department of Radiology, Wright Center for Innovation in Biomolecular Imaging, The Ohio State University , Columbus, Ohio 43210, United States.
Biomacromolecules. 2014 Dec 8;15(12):4488-94. doi: 10.1021/bm501311g. Epub 2014 Nov 12.
There has been recent interest in designing smart diagnostic or therapeutic self-assembling peptide or polymeric materials that can selectively undergo morphological transitions to accumulate at a disease site in response to specific stimuli. Developing approaches to probe these self-assembly transitions in environments that accurately amalgamate the diverse plethora of proteins, biomolecules, and salts of blood is essential for creating systems that function in vivo. Here, we have developed a fluorescence anisotropy approach to probe the pH-dependent self-assembly transition of peptide amphiphile (PA) molecules that transform from spherical micelles at pH 7.4 to nanofibers under more acidic pH's in blood serum. By mixing small concentrations of a Ru(bipy)3(2+)-tagged PA with a Gd(DO3A)-tagged PA having the same lipid-peptide sequence, we showed that the pH dependence of self-assembly is minimally affected and can be monitored in mouse blood serum. These PA vehicles can be designed to transition from spherical micelles to nanofibers in the pH range 7.0-7.4 in pure serum. In contrast to the typical notion of serum albumin absorbing isolated surfactant molecules and disrupting self-assembly, our experiments showed that albumin does not bind these anionic PAs and instead promotes nanofibers due to a molecular crowding effect. Finally, we created a medium that replicates the transition pH in serum to within 0.08 pH units and allows probing self-assembly behavior using conventional spectroscopic techniques without conflicting protein signals, thus simplifying the development pathway from test tube to in vivo experimentation for stimuli-responsive materials.
最近人们对设计智能诊断或治疗性自组装肽或聚合物材料产生了兴趣，这些材料可以响应特定刺激而选择性地发生形态转变，在疾病部位聚集。开发在能准确融合血液中大量不同蛋白质、生物分子和盐类的环境中探测这些自组装转变的方法，对于创建在体内发挥作用的系统至关重要。在此，我们开发了一种荧光各向异性方法，用于探测肽两亲分子（PA）的pH依赖性自组装转变，该分子在pH 7.4时从球形胶束转变为血清中更酸性pH条件下的纳米纤维。通过将少量浓度的钌（联吡啶）3（2+）标记的PA与具有相同脂质 - 肽序列的钆（DO3A）标记的PA混合，我们表明自组装的pH依赖性受到的影响最小，并且可以在小鼠血清中进行监测。这些PA载体可以设计成在纯血清中pH范围为7.0 - 7.4时从球形胶束转变为纳米纤维。与血清白蛋白吸收孤立的表面活性剂分子并破坏自组装的典型概念相反，我们的实验表明白蛋白不结合这些阴离子PA，而是由于分子拥挤效应促进纳米纤维的形成。最后，我们创建了一种介质，将血清中的转变pH复制到0.08 pH单位以内，并允许使用传统光谱技术探测自组装行为而不会产生冲突的蛋白质信号，从而简化了从试管到体内实验的刺激响应材料的开发途径。
