Department of Biological Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India.
Department of Biological Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032, India.
Colloids Surf B Biointerfaces. 2014 Jan 1;113:442-9. doi: 10.1016/j.colsurfb.2013.09.047. Epub 2013 Sep 30.
The present work reports the development of water-in-oil (w/o) microemulsion doped with newly designed nanocomposite comprising of gold nanoparticle (GNP) decorated single walled carbon nanotube (SWNT). This nanocomposite included cationic reverse micelle was used to boost the catalytic activity of a surface-active enzyme, Chromobacterium viscosum lipase (CV lipase). SWNT was non-covalently dispersed using cetyltrimethylammonium bromide (CTAB), cetylalaninetrimethylammonium chloride (CATAC) while GNP was synthesized by reduction of HAuCl4 with reducing/stabilizing agent trisodium citrate. Counterion exchange between cationic SWNT dispersing agent and anionic capping agent of GNP led to the formation of GNP decorated SWNT (SWNT-GNP) nanocomposite. This newly developed SWNT-GNP included CTAB reverse micelle was characterized by several microscopic and spectroscopic techniques. Interfacially located SWNT-GNP included w/o microemulsion (confirmed from biphasic and fluorescence experiment) was used as a proficient host for enhancing the catalytic activity of lipase. Lipase activity within this self-assembled soft nanocomposite improved up to 3.9-fold (second order rate constant, k2=1694±16 cm(3) g(-1) s(-1)) compared to standard CTAB reverse micelle (k2=433±7 cm(3) g(-1) s(-1)). In case of cetyltripropyl ammonium bromide (CTPAB) based reverse micelle, the observed lipase activity improved to k2=2036±11 cm(3) g(-1) s(-1) in the presence of SWNT-GNP composite. Notably, this catalytic activity of lipase within SWNT-GNP included reverse micelle was till date the highest activity found in any w/o microemulsion. The attainment of flexibility in enzyme conformation at the augmented interface was verified using circular dichroism (CD) spectroscopy.
本工作报道了一种新型纳米复合材料的制备及其在油包水（w/o）微乳液中的应用。该纳米复合材料由负载金纳米粒子（GNP）的单壁碳纳米管（SWNT）组成。该纳米复合材料中的阳离子反胶束被用于提高表面活性脂肪酶——粘质沙雷氏菌脂肪酶（CV 脂肪酶）的催化活性。SWNT 通过十六烷基三甲基溴化铵（CTAB）、十六酰基丙氨酸三甲基氯化铵（CATAC）实现非共价分散，而 GNP 则通过还原稳定剂三钠柠檬酸盐还原 HAuCl4 合成。阳离子 SWNT 分散剂的抗衡离子与 GNP 的阴离子封端剂之间的离子交换导致 GNP 负载的 SWNT（SWNT-GNP）纳米复合材料的形成。这种新开发的 SWNT-GNP 负载 CTAB 反胶束通过多种微观和光谱技术进行了表征。界面处的 SWNT-GNP 负载 w/o 微乳液（通过两相和荧光实验证实）被用作增强脂肪酶催化活性的有效主体。与标准 CTAB 反胶束（k2=433±7 cm3g-1s-1）相比，该自组装软纳米复合材料中的脂肪酶活性提高了 3.9 倍（二级速率常数，k2=1694±16 cm3g-1s-1）。在十六烷基三丙基溴化铵（CTPAB）基反胶束的情况下，在 SWNT-GNP 复合材料存在下，观察到的脂肪酶活性提高到 k2=2036±11 cm3g-1s-1。值得注意的是，在任何 w/o 微乳液中，这种负载脂肪酶的 SWNT-GNP 反胶束的催化活性至今仍是最高的。利用圆二色性（CD）光谱证实了在增强的界面上酶构象的灵活性的提高。
