Multiplexing Detection of Extracellular and Intracellular Toxins in Water by GaN Field Effect Transistors

蓝藻华，也被称为有害藻华，已知会产生各种有害毒素，包括微囊藻毒素、蛤蚌毒素、anatoxin-a和柱体精子蛋白酶。当涉及到水安全和管理时，这些水华已经成为一个主要问题，因为它们会对公众健康、水生生态系统和当地经济产生严重影响。目前的毒素检测方法包括酶联免疫吸附法、聚合酶链反应、高效液相色谱法和液相色谱-质谱法。这些方法需要复杂的操作、荧光团标记、精密的批量仪器和熟练的人员。此外，这些方法需要数天的分析时间，不能在现场轻松进行，也不能同时确定多种毒素。因此，认识到水质监测和环境保护的重要性，迫切需要能够满足这一挑战的简单和低成本的检测技术。用于检测水中毒素的新型传感器的开发可以彻底改变我们对水生态系统在流域尺度上控制水质的功能的理解。例如，在一定程度上，它可以通过组装一组新型传感器来完成，用于现场实时多路监测水循环中的生物和非生物隔间。这些传感器的无处不在的网络将使在空间和时间尺度上的过程监测比目前可行的要高得多。将这些数据流整合到水循环的模拟模型中，将加深我们对这些过程的理解，促进实时指数的发展，以预测诸如藻华等事件，并确定可以遵循的策略，以避免此类事件的发生。研究成果将整合到推广活动中，包括与工业界合作验证，在伊利湖进行实地测试，通过俄勒冈州立大学石头实验室的年度“媒体日”，“纳米生物技术夏令营”和当地学校学生的“采用课程”来宣传技术。本项目的目标是开发基于GaN（氮化镓）的免疫场效应晶体管生物传感器，用于检测水和环境样品中的细胞外和细胞内蓝藻毒素。所提出的设备能够根据需要通过免疫传感和核酸检测快速（在几分钟内）进行无标记多路检测。这些传感器设备可以在一个大型阵列系统中制造，每个设备使用不同的抗体，这样就可以通过一次低成本的测试来获得污染物的完整概况。由于这些设备可以以非常小的尺寸制造，并在单个设备级别进行监测，因此每个传感阵列都可以检测到极低浓度的潜在毒素。虽然这类生物传感器已被证明用于其他生物传感应用，但其在蓝藻毒素检测和监测方面的应用尚未得到证实。该团队选择AlGaN（氮化铝镓）/GaN异质结半导体结构作为器件平台，因为这种材料系统具有化学惰性和稳定性，因此可以实现高信噪比。所提出的毒素传感器能够满足以下要求：(1)灵敏度高或检出限低，动态范围大；(2)高特异性和多路检测；(3)检测速度快，分析时间短；(4)无标签；(5)现场便携性和易用性，能够检测细胞外和细胞内毒素，并形成长期环境监测的传感网络。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。

Cyanobacterial blooms, also known as harmful algal blooms have been known to produce a variety of harmful toxins including microcystins, saxitoxins, anatoxin-a, and cylindrospermopsins. These blooms have become a major concern when it comes to water safety and management as they can have severe impacts on public health, aquatic ecosystems, and local economies. Current methods for toxin detection include enzyme-linked immunosorbent assay, polymerase chain reaction, high performance liquid chromatography, and liquid chromatography-mass spectrometry. These methods require complex operation, fluorophore labeling, sophisticated and bulk instruments, and skilled personnel. Additionally, these methods take days for analysis, cannot be easily performed in the field, and cannot determine multiple toxins at the same time. Therefore simple and low cost detection technologies that can meet this challenge are critically needed in recognition of the importance of water quality monitoring and environmental protection. The development of novel sensors for detection of toxins in water can revolutionize our understanding of aquatic ecosystem functions governing water quality at the watershed scale. For example, it can be accomplished, in part, by assembling a portfolio of novel sensors for on-site real time multiplexing monitoring of the biotic and abiotic compartments within the water cycle. The pervasive networking of these sensors will enable process monitoring at spatial and temporal scales that are much higher than is currently feasible. Integrating these data streams into simulation models of the water cycle will deepen our understanding of these processes, facilitate the development of real-time indices to forecast events such as algal blooms, and identify strategies that can be followed to avert such events. The outcome of the research will be integrated in the outreach activities include working with industry for validation, field testing in Lake Erie, publicizing the technology through annual "Media Day" at OSU Stone Lab, "Nanobiotechnology Summer Camp" and "Adopting a Class" from local school students. The objective of this project is to develop GaN (gallium nitride) based immunologically field effect transistors biosensors for detection of extracellular and intracellular cyanotoxins in water and environmental samples. The proposed devices are capable of label-free multiplexing detection rapidly (in minutes) by both immuno-sensing and nucleic acid detection as necessary. These sensor devices can be fabricated in a large array system with each device using distinct antibodies, so that a full profile of contaminants can be achieved by a single low cost test. Due to the fact that these devices can be fabricated at very small sizes and monitored at the individual device level, each sensing array can detect potential toxins at extremely low concentrations. Although this kind of biosensors have been demonstrated for other biosensing applications, their application to cyanotoxin detection and monitoring has yet to be demonstrated. The team choses AlGaN (aluminum gallium nitride)/GaN heterojunction semiconductor structures as the device platform because this material system is chemically inert and stable so a high signal-to-noise ratio can be achieved. The proposed toxin sensors can meet the following requirements: (1) high sensitivity or low detection limit and large dynamic range; (2) high specificity and multiplexing detection; (3) rapid detection and short analysis time; (4) label free; and (5) field-portability and easy-of-use, capable of detection of both extracellular and intracellular toxins, and forming a sensing network for long term environmental monitoring.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.