Collaborative Research: Ionic Amplifiers for Biosensing

大自然已经进化出复杂的途径来放大检测低浓度离子或分子的信号。一个强大的人造放大器系统，与那些在《自然》中实现的离子和分子信号的控制和放大相似，将有助于探测具有超低电导率的生物通道（如糖尿病中的重要通道）和理解生物过程。受生物学的启发，这项研究将专注于开发第一步，以制备具有放大特性的离子电路，该电路建立在电子集成电路和Nature？S信号通路。离子电路的原型将使用具有控制几何和表面化学的纳米孔作为构建块来制备。研究人员选择纳米孔作为构建单元，因为生物细胞中的生物通道和孔是生物扩增的第一步。跨学科的项目将为研究生和本科生创造一个良好的培养环境。此外，两所大学的本地学生亦计划到访，进行有关纳米科技和生物传感的实践活动。该研究的总体目标是为生物传感应用设计一种通用的离子放大和构建响应时间为毫秒级的离子晶体管的途径。包括氮化硅、聚合物薄膜和玻璃纳米吸管在内的各种材料中的纳米孔将通过调整其表面特性和几何形状来呈现离子晶体管。纳米多孔晶体管将是三个终端系统，其工作原理与基于半导体的晶体管相似。在构建的离子体系中，阴离子携带负电荷而不是电子，阳离子携带正电荷而不是空穴。由于仅几个离子或分子的运动就会导致测量信号的变化，因此需要系统的纳米级尺寸以实现快速的时间响应。在电路中连接两个离子晶体管将导致制备一个离子等效的达林顿放大器，其中电流增益等于两个组件晶体管放大的乘积。并将演示达林顿放大器在探测具有超低电导率的离子通道中的应用。离子差分放大器的制备也将被探讨。使用这些放大器，原则上可以实现数千倍的放大，使测量飞安培电流成为可能。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Nature has evolved complex pathways to amplify the signal from the detection of low concentrations of ions or molecules. A robust, man-made amplifier system with similar control and amplification of ionic and molecular signals as those achieved in Nature will be helpful for probing biological channels with ultra-low conductivities (like those important in diabetes) and understanding biological processes. Inspired by biology, this research will focus on development of the first steps to prepare ionic circuits with amplifying properties built on the principles of both electronic integrated circuits and Nature?s signaling pathways. Prototypes of ionic circuits will be prepared using nanopores with controlled geometry and surface chemistry as the building blocks. The investigators chose nanopores as building blocks, because biological channels and pores in a biological cell create the first step of biological amplification. The interdisciplinary program will create an excellent training environment for graduate and undergraduate students. Visits of students from local schools at both universities are also planned with hands-on activities on nanotechnology and biosensing.The overarching goal of the research is to design a generic route for ionic amplification and building ionic transistors with millisecond response time for biosensing applications. Nanopores in various materials including silicon nitride, polymer films and glass nanopipettes will be rendered ionic transistors by tuning their surface characteristics and geometries. The nanoporous transistors will be three terminal systems, which will function according to principles similar to those of semiconductor-based transistors. In the ionic systems constructed, instead of electrons, anions will carry negative charge, and, instead of holes, cations will carry positive charge. Nanoscale dimensions of the system are required for a quick temporal response, as movement of only a few ions or molecules will lead to changes in the measured signal. Connecting two ionic transistors in a circuit will lead to preparation of an ionic equivalent of a Darlington amplifier, where current gain is equal to a product of amplifications of the two component transistors. Application of the Darlington amplifier to probe ion channels with ultralow conductivities will be demonstrated as well. Preparation of an ionic differential amplifier will also be explored. With these amplifiers, in principle, thousand-fold amplification might be achieved, making measuring femto-Ampere currents accessible.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.