Graphene Sensors for Food Allergen Detection

由于官能化，石墨烯具有出众的电子特性、表面敏感性和选择性，使其成为传感器应用的理想选择。基于化学修饰的石墨烯传感器的新型、通用、实时监测传感器技术将被用于食品安全应用，检测食品中的花生(Arah1-9)过敏原。食品加工厂中可能存在极低浓度的微量坚果，可在过敏个体中引发免疫反应，从麻疹到严重的胃肠道和呼吸道症状，在严重情况下-过敏性休克。在有可能交叉污染的地方，食品生产商有义务为产品贴上标签或召回标签错误的产品-给行业造成数百万美元的损失(GB 500万/召回发生率)并产生负面宣传。我们的传感器系统为食品和食品加工单位的现场智能监测而开发，将实现即时和低成本的过敏原监测。使用化学修饰的石墨烯，集成到封装的过敏原传感器中进行现场监测，将为最终用户联合利华在监测微量坚果污染物方面提供真正的突破。该传感器技术使用具有受体分子功能的石墨烯通道-能够选择性和特异性地检测特定过敏原。该联盟已经开发出将抗体附着到石墨烯上的化学功能化方法。该项目将使用针对花生过敏原的抗体作为受体。商业传感器的生产需要大面积、均匀、电子级的石墨烯--在绝缘的衬底上。加州大学欧文分校将在预制图案化的GE上开发“无转移”石墨烯，这可能会使石墨烯电子产品发生阶段性变化。同时，将对生长在铜上的石墨烯进行工作-转移到SiO_2/Si晶片上-通过使设备和功能化工作能够在石墨烯/锗可用之前完成来降低风险。这些材料(NPL)的表征对于提供具有一致和可控电性能的均匀石墨烯至关重要。NPL将分析石墨烯生长和化学修饰后的层厚度、均匀性、缺陷密度和电性能。PG将把现有的石墨烯器件制造工艺转移到SiO_2/Si上的大面积CVD石墨烯和Ge晶片上的预图案化石墨烯，以制造石墨烯化学场效应晶体管。ChEM-FET包括两个金属(钛/金)触点之间的石墨烯通道，该通道通过光刻和随后的氧等离子体刻蚀形成图案。大面积制造将降低单个传感器的成本。根据目前定价的晶片和加工成本GB 1000&使用4 mm正方形芯片，每个传感器的成本为2.22 GB。通过使用2 mm的正方形芯片，这可以降低到每个芯片0.55 GB。随着石墨烯价格的下降，这一成本可能会进一步降低。胺表面化学是在以前的EPSRC资助下开发的[OJ Guy]，PG将使用它来附着过敏原特异性抗体。为抗体与石墨烯的结合而开发的新的电化学重氮功能化将与新的血浆胺终止工艺一起使用，然后(A)酰胺与抗体偶联&(B)阻断非特定结合部位。变应原结合到修饰的石墨烯表面会引起门控效应，这可以通过电/电化学检测到。PG和NPL将表征功能化石墨烯(XPS、I-V、CV、拉曼、SKPM)。PG的原型传感器最终将被集成到联合利华的一个食品处理单元模型中，用于检测微量的过敏原。

Exceptional electronic properties, surface sensitivity & selectivity, inferred by functionalisation, makes graphene ideal for sensor applications. Novel, generic, real-time monitoring sensor technology, based on chemically modified graphene transducers, will be demonstrated for food safety applications, detecting peanut (Ara h 1-9) allergens in food products. Trace quantities of nuts can be present in food processing plants at very low concentrations & can trigger an immune response in allergic individuals, ranging from hives to severe gastrointestinal & respiratory symptoms, & in serious cases - anaphylactic shock.Where there is a possibility of cross-contamination, food producers are obliged to label products or recall incorrectly labelled products - costing industry millions (£5m/recall incidence) & producing negative publicity. Our sensor system, developed for in-situ smart monitoring of food & food processing units, would enable instant and low-cost allergen monitoring. Using chemically modified graphene, integrated into a packaged allergen sensor, for in situ monitoring would offer end-user Unilever a real breakthrough in monitoring for trace nut contaminants.The sensor technology uses a graphene channel functionalised with a receptor molecule - capable of selective & specific detection of a particular allergen. Chemical functionalisation methods, for attaching antibodies to graphene, have already been developed by the consortium. This project will use antibodies targeted against peanut allergens as the receptors. Commercial sensor production requires large area, uniform, electronic-grade graphene - on an insulating substrate. UCAMwill develop "Transfer free" graphene on pre-patterned Ge could providing a step change in graphene electronics. In parallel, work will be performed on graphene grown on copper - transferred onto SiO2/Si wafers - mitigating risk by enabling device and functionalisation work to be completed prior to the availability of graphene/ Germanium. Characterisation of these materials (NPL) is essential to providing uniform graphene with consistent and controlled electrical properties. NPL will analyse layer thicknesses, uniformity, defect densities and electrical performance following growth and also subsequent to chemical modification of graphene. PG will transfer existing graphene device fabrication process to large area CVD graphene on SiO2/Si & pre-patterned graphene on Ge wafers to fabricate graphene Chemical Field Effect Transistors. Chem-FETs comprise a graphene channel, patterned via lithography & subsequent oxygen plasma etch, between two metal (Ti/Au) contacts. Large area fabrication will reduce individual sensor costs. Based on current pricing wafer & processing costs of £1000 & using 4mm square chips, yields a cost of £2.22 per sensor. This could be reduced to £0.55 per chip by using a 2mm square chip. As the price of graphene comes down, this cost could be further reduced. Amine surface chemistry, developed under previous EPSRC grants [OJ Guy], will be used by PG to attach allergen-specific antibodies. Novel electrochemical diazonium functionalisation developed for antibody attachment to graphene will be used along with new plasma amine termination processes, before (a) amide coupling to the antibody & (b) blocking non-specific binding sites. Allergen binding to modified graphenes surface induces a gating effect, which can be electrically/electrochemically detected. PG and NPL will characterise functionalised graphene (XPS, I-V, CV, Raman, SKPM). PG's prototype sensors would ultimately be integrated into a model food processing unit at Unilever & used to detect trace quantities of allergens.