Miyoshi Hirokazu, Matsuo Yuki, Liu Yiyao, Sakata Takao, Mori Hirotaro
Radioisotope Research Center, The University of Tokushima, Tokushima 770-8503, Japan.
J Colloid Interface Sci. 2009 Mar 15;331(2):507-13. doi: 10.1016/j.jcis.2008.09.026. Epub 2008 Sep 17.
Porous silica nanocapsules with 20% 3-aminopropyltrimethoxysilane (APS)-bound 6-carboxy-fluorescein (APS-fluorescein) and 80% APS molecules adsorbed on the surface of a 50-nm-diameter Au core were prepared by a modified core-shell method. Silica mesoporous nanocapsules were obtained after the Au cores were dissolved in sodium cyanide. The size of the pores in the silica shells corresponded to the area of the fluorescein (approximately 1.02 nm(2)) in each APS-fluorescein molecule, which was bound to the silica shell by coupling between the silanol groups of APS in the APS-fluorescein molecule and the silica shell. The amino group of APS bound to the silica inside the shell is also reactive. Dy485XL N-hydroxysuccinimide ester (NHS) molecules were then added to the mesoporous silica nanocapsules in the solution and bonded to the amino group of the interior. Thus, mesoporous (fluorescein and Dy485XL)-bound silica nanocapsules were obtained. The fluorescence of Dy485XL was only observed in the mesoporous (fluorescein and Dy485XL)-bound silica nanocapsules in aqueous solution after ultrafiltration. However, the fluorescence of fluorescein reappeared after the addition of acetonitrile. Furthermore, upon adding various solvents to the mesoporous (fluorescein and Dy485XL)-bound silica nanocapsules, their fluorescence varied with that of fluorescein or Dy485XL. In the case of a mixture of 6-carboxy-fluorescein-N-hydroxysuccinimide (FLUOS) and Dy485XL-NHS free molecules in aqueous solution, the fluorescence of FLUOS was observed. Such different fluorescence phenomena demonstrated that Dy485XL-NHS molecules can easily penetrate into the nanocapsule interior via the pores and that the interior of the silica nanocapsules can bind to Dy485XL molecules. These fluorescence behaviors are discussed in terms of fluorescence resonance energy transfer (FRET) and solvatochromism.
采用改进的核壳法制备了多孔二氧化硅纳米胶囊，其由结合了20% 3 - 氨丙基三甲氧基硅烷（APS）的6 - 羧基荧光素（APS - 荧光素）和吸附在直径50 nm金核表面的80% APS分子组成。将金核溶解在氰化钠中后得到二氧化硅介孔纳米胶囊。二氧化硅壳层中孔的大小与每个APS - 荧光素分子中荧光素的面积（约1.02 nm²）相对应，该荧光素通过APS - 荧光素分子中APS的硅醇基团与二氧化硅壳层之间的偶联而与二氧化硅壳层结合。壳内与二氧化硅结合的APS的氨基也具有反应活性。然后将Dy485XL N - 羟基琥珀酰亚胺酯（NHS）分子加入到溶液中的介孔二氧化硅纳米胶囊中，并与内部的氨基结合。由此得到了介孔（荧光素和Dy485XL）结合的二氧化硅纳米胶囊。超滤后，仅在水溶液中的介孔（荧光素和Dy485XL）结合的二氧化硅纳米胶囊中观察到Dy485XL的荧光。然而，加入乙腈后荧光素的荧光重新出现。此外，向介孔（荧光素和Dy485XL）结合的二氧化硅纳米胶囊中加入各种溶剂后，它们的荧光随荧光素或Dy485XL的荧光而变化。在水溶液中6 - 羧基荧光素 - N - 羟基琥珀酰亚胺（FLUOS）和Dy485XL - NHS游离分子的混合物的情况下，观察到了FLUOS的荧光。这种不同的荧光现象表明Dy485XL - NHS分子可以通过孔轻松渗透到纳米胶囊内部，并且二氧化硅纳米胶囊的内部可以与Dy485XL分子结合。根据荧光共振能量转移（FRET）和溶剂化显色作用对这些荧光行为进行了讨论。
