【作者】 李凯；

【导师】 伍小平； 张青川；

【作者基本信息】 中国科学技术大学 ， 固体力学， 2006， 博士

【摘要】 在生物和化学领域中，生化传感器是进行各种实验研究的必要条件和工作基础。研制特异性强，灵敏度高，响应时间短的高性能传感器一直是人们追求的目标。近年来，伴随着微机电系统(Microelectromechanical System，MEMS)技术的兴起，系统的微型化成为一个重要的发展方向。它的优点在于：具有很大的比表面积，对表面效应十分敏感，容易实现阵列式的多点集成，而且运用IC制造工艺可低成本大规模生产。这种技术的出现，为生化传感器的研制提供一条新的思路。 本文针对当前生化传感领域中，大分子构象转变的检测问题展开了实验研究。当生化过程在微悬臂梁的表面发生时，会导致其表面应力发生变化并产生弯曲变形。本文利用这种效应独立的构建了一套基于微悬臂梁的生化传感实验系统，并在其基础上，按照从简单到复杂——即从结构简单的人工合成大分子聚N-异丙基丙烯酰胺(PNIPAM)，到结构复杂的生物大分子胰蛋白酶——的研究思路对大分子的构象转变问题进行了实验研究，具体包括以下四个方面的内容： (1) 以小分子(11羧基硫醇，11MUA)在微悬臂梁上的吸附过程作为对照，研究了大分子(一端巯基化的聚N-异丙基丙烯酰胺，HS-PNIPAM)在微悬臂梁表面吸附生长过程中的构象转变。结果显示：11MUA在微悬臂梁表面的吸附生长过程包括两个阶段，而HS-PNIPAM分子的吸附生长过程却由三个阶段组成。分析认为，导致这种差异的主要原因在于PNIPAM分子具有构象的调整机制，整个吸附生长过程就是其构象不断调整直至形成分子刷的过程。 (2) 通过分子自组装的方法将PNIPAM分子修饰到微悬臂梁表面，检测环境(水)温度在20℃到40℃之间变化时，微悬臂梁的变形。结果显示：在升温过程中(20℃到40℃)，微悬臂梁发生了弯曲变形。这个过程对应着PNIPAM分子链从伸展的无规线团构象转变到塌缩的小球构象。而在降温过程中(40℃到20℃)，微悬臂梁发生了相反方向的变形，这对应这PNIPAM分子链构象的恢复。从整体上看，微悬臂梁的变形在整个温度循环过程中的表现出不可逆性和迟滞性。分析认为，这是由于PNIPAM分子链在塌缩过程中形成氢键引起的。 (3) 研究了当环境pH制在3到11之间变化时，修饰在微悬臂梁表面聚丙烯更多还原

【Abstract】 The goal to find biochemical sensors with high specificity, sensitivity and short response time are always pursued by people. Recently, the progress in the technology of Microelectromechanical System (MEMS) has brought some new ideas for this aim because of its advantages, such as large surface-area-to-volume ratio, very sensitive to surface effect, easy to realize array compact and low-cost. volume production.When a biochemical process taking place on a microcantilever surface, its surface stress changes and result in a cantilever deflection. Using this effect, an experimental system was established, and a simple-to-complex(from simple artificial PNIPAM macromolecule to complex natural Trypsin protein molecule) method was adopted to research experimentally the conformation transition of macromolecules. This investigation involves four aspects as bellow.(1) Taking a small molecule (11-mercaptoundecanoic acid, 11MUA) adsorption process as a control, the conformation transition of thiol-terminated poly(N-isopropylacrylamide) (HS-PNIPAM) in the adsorption-growth process on a microcantilever surface have been investigated. The results show that different from 11MUA whose growth process involves two phases, the growth process of HS-PNIPAM consists of three steps. By analysis, it is considered that the reason causing this difference is the conformational adjust mechanism which leads the HS-PNIPAM to form polymer brush finally.(2) Employing molecule self assembling method, PNIPAM molecules were grafted onto the surface of a microcantilever, and the cantilever deflections were detected by varying the surrounding (water solution) temperature in the range of 20°C —40℃. The results shown that the microcantilever deflects upon heating and an opposite deflection occurs upon cooling. This process corresponding to the conformation transition of PNIPAM, namely, transition between a coil conformation and a globule conformation. The deflection of the microcantilever is irreversible and shows a clear hysteresis during the whole experimental process. These phenomena are attributed to hydrogen bonding formed during the collapsing process.更多还原