Solberg Sean M, Landry Christopher C
Department of Chemistry, University of Vermont, 82 University Place, Burlington, Vermont 05405, USA.
J Phys Chem B. 2006 Aug 10;110(31):15261-8. doi: 10.1021/jp061691+.
In these experiments, double-stranded, linear DNA sequences were adsorbed into the pores of spherically shaped acid-prepared mesoporous silica (APMS). The lengths of the sequences were either 760 base pairs or 2000 base pairs. DNA adsorption into the interior of the mesoporous material was confirmed using confocal microscopy of sequences containing fluorescently labeled DNA molecules. Additional characterization with N(2) physisorption and powder X-ray diffraction supported this finding. The extent of adsorption was measured at various concentrations using UV-visible spectrophotometry to establish adsorption isotherms. APMS alone adsorbed a negligible amount of DNA; however, exchanging divalent cations such as Mg(2+) and Ca(2+) into the pores of APMS prior to DNA uptake was found to cause a significant amount of DNA to be adsorbed. Using Na(+) caused a lower amount of DNA to be adsorbed. DNA adsorption was also dependent on the pore diameter of APMS. Adsorption increased upon expansion of the pore size of the metal ion-exchanged material from 34 to 54 A; however, no additional uptake was measured by further increasing the pore size to 100 A. The amount of DNA adsorbed could also be significantly increased by using (aminopropyl)triethoxysilane to covalently link ammonium ions to the surface. Postsynthetic modification of the silica surface with aminopropyl groups increased the maximum DNA adsorption to 15.7 microg/mg silica, for materials with pore diameters of 100 A, which is 2 to 3 times more adsorbed DNA than for metal ion-exchanged material. This indicated that DNA binds more strongly in the presence of the ammonium group compared to the metal counterions. Finally, calculation and comparison of Freundlich and Langmuir constants for these adsorption processes indicate that intermolecular interactions between the DNA molecules within the pores are significant when the effective pore diameter is small, including materials with larger pores that were modified with organosilane.
在这些实验中，双链线性DNA序列被吸附到球形酸制备介孔二氧化硅（APMS）的孔中。序列长度为760个碱基对或2000个碱基对。使用含有荧光标记DNA分子的序列进行共聚焦显微镜观察，证实了DNA吸附到介孔材料内部。通过N₂物理吸附和粉末X射线衍射进行的额外表征支持了这一发现。使用紫外可见分光光度法在不同浓度下测量吸附程度，以建立吸附等温线。单独的APMS吸附的DNA量可忽略不计；然而，发现在摄取DNA之前将二价阳离子如Mg²⁺和Ca²⁺交换到APMS的孔中会导致大量DNA被吸附。使用Na⁺会导致吸附的DNA量减少。DNA吸附还取决于APMS的孔径。当金属离子交换材料的孔径从34 Å扩大到54 Å时，吸附增加；然而，将孔径进一步增加到100 Å时，未测量到额外的摄取量。通过使用（氨丙基）三乙氧基硅烷将铵离子共价连接到表面，也可以显著增加DNA的吸附量。对于孔径为100 Å的材料，用氨丙基对二氧化硅表面进行后合成修饰可使最大DNA吸附量增加到15.7 μg/mg二氧化硅，这比金属离子交换材料吸附的DNA多2至3倍。这表明与金属抗衡离子相比，在铵基团存在下DNA结合更强。最后，对这些吸附过程的弗伦德利希和朗缪尔常数进行计算和比较表明，当有效孔径较小时，包括用有机硅烷修饰的较大孔径材料，孔内DNA分子之间的分子间相互作用很显著。
