Lee Lillian, Johnston Angus P R, Caruso Frank
Centre for Nanoscience and Nanotechnology, Department of Chemical and Biomolecular Engineering, The University of Melbourne, Victoria 3010, Australia.
Biomacromolecules. 2008 Nov;9(11):3070-8. doi: 10.1021/bm800593t. Epub 2008 Oct 1.
DNA films are promising materials for diverse applications, including sensing, diagnostics, and drug/gene delivery. However, the ability to tune the stability of DNA films remains a crucial aspect for such applications. Herein, we examine the role of oligonucleotide length on the formation, and salt and thermal stability, of DNA multilayer films using oligonucleotides of homopolymeric diblocks (polyAG and polyTC), with each block (A, G, T, or C) ranging from 5 to 30 bases (10-, 20-, 30-, 40-, and 60-mer). Using a combination of quartz crystal microgravimetry, dual polarization interferometry, and flow cytometry, we demonstrate that at least 10 bases per hybridizing block in the DNA diblocks (that is, 20-mer) are required for successful hybridization and, hence, DNA multilayer film formation. Films assembled using longer oligonucleotide blocks were more stable in low salt conditions, with the DNA multilayer films assembled from the 60-mer oligonucleotides remaining intact in solutions of about 25 mM NaCl. A systematic increase in film melting temperature ( T m) was observed for the DNA multilayer films (assembled on colloids) with increasing oligonucleotide length, ranging from 38.5 degrees C for the 20-mer films to 53 degrees C for the 60-mer films. Further, an alternating trend in T m of the DNA multilayer films was observed with layer number (AG or TC); DNA multilayer films terminated with an AG layer exhibited a higher T m (44-49 degrees C) than films with an outermost TC layer (ca. 38 degrees C), suggesting a rearrangement of the film structure upon hybridization of the outermost layer. This work shows that the stability of DNA multilayer films can be tuned by varying the length of the oligonucleotide building blocks, thus providing a versatile means to tailor the salt and thermal stability of DNA films, which is necessary for the application of such films.
DNA膜是用于多种应用的有前景的材料，包括传感、诊断以及药物/基因递送。然而，调节DNA膜稳定性的能力对于此类应用而言仍然是一个关键方面。在此，我们使用均聚物双嵌段（聚AG和聚TC）的寡核苷酸来研究寡核苷酸长度对DNA多层膜的形成、盐稳定性和热稳定性的作用，每个嵌段（A、G、T或C）的长度范围为5至30个碱基（10聚体、20聚体、30聚体、40聚体和60聚体）。通过结合石英晶体微重力法、双偏振干涉测量法和流式细胞术，我们证明DNA双嵌段中每个杂交嵌段至少需要10个碱基（即20聚体）才能成功杂交，从而形成DNA多层膜。使用更长的寡核苷酸嵌段组装的膜在低盐条件下更稳定，由60聚体寡核苷酸组装的DNA多层膜在约25 mM NaCl的溶液中保持完整。随着寡核苷酸长度增加，观察到DNA多层膜（组装在胶体上）的膜熔解温度（Tm）有系统地升高，从20聚体膜的38.5℃到60聚体膜的53℃。此外，观察到DNA多层膜的Tm随层数（AG或TC）呈现交替趋势；以AG层终止的DNA多层膜的Tm（44 - 49℃）高于最外层为TC层的膜（约38℃），这表明在最外层杂交时膜结构发生了重排。这项工作表明，可以通过改变寡核苷酸构建块的长度来调节DNA多层膜的稳定性，从而提供一种通用方法来定制DNA膜的盐稳定性和热稳定性，这对于此类膜的应用是必要的。
