NECi Superior Enzymes

Nitrate Biosensor - Case Study


Courtesy of NECi Superior Enzymes


In 1998, Dr. Bill Campbell and his team published a peer-reviewed journal article in Analytical Chemistry on the construction and characterization of Nitrate Reductase-Based Amperometric Electrode and Nitrate Assay of Fertilizers and Drinking Water. This publication set the stage for the nitrate biosensor project. In this publication, we found that nitrate reductase was indeed capable of being employed in an electrode based system and assays conducted with the electrode compared well with colorimetric and potentiometric assays of the same samples.

In 2012, Nicolas Plumere, Jorg Henig, and Dr. Campbell published another peer-reviewed article in Analytical Chemistry on an Enzyme-Catalyzed O2 Removal System for Electrochemical Analysis under Ambient Air. This technology eliminates the problem of oxygen interference with an electrochemical Nitrate Reductase catalyzed Nitrate Biosensor. Dr. Bill Campbell and his wife, Ellen R. Campbell submitted a Phase 1 USDA Proposal for funding research to develop the Nitrate Biosensor which would employ the oxygen removal system.

During our funded project from NSF, we collaborated with Dr. Joshua Pearce and his team at Michigan Technological University to develop an open-source, handheld, spectrophotometer. This device improves the utility of NECi's on-site Nitrate Test Kits, and sends data directly to mobile devices via Bluetooth interface where it can be geographically tracked, stored, and exported as a CSV file for further analysis. When beta-testing of these devices was completed during a pilot project with a major agricultural company, feedback was that the enzyme-based test kits simply weren't fast or easy enough, and they wanted results within seconds. Our solution to this was to develop a Nitrate Biosensor that would provide users with data within minutes on-site using enzyme based analytical chemistry technology. The concept for the biosensors was inspired by the design of glucose meter for diabetes point-of-care management, using interchangeable 'test strips'. Ideally, the Nitrate Biosensor will be a two component system with a disposable point-of-use nitrate sensor and nitrate meter, which will be interfaced via Bluetooth transmission to a smartphone or tablet PC. We plan to adapt this technology to our phosphate measurement enzymes as well.


Nitrate supplies nitrogen for plant growth and crop productivity and is a limiting factor for obtaining maximum yield in many crops. Phosphate is also a key factor for plant growth and crop productivity since phosphorus is central to many biochemical processes and components. Both nitrogen and phosphorus are supplied to plants in a variety of forms through fertilizers, mainly applied to soils in fields. However, not all of the nitrogen and phosphorus ends up as a usable form in crop plant tissue which will in turn support growth and productivity. Excess nutrients leach into nearby groundwater, leading to potential adverse affects to environmental and human health.

In order to properly manage nutrients, better and more frequent analysis of soil and water need to be implemented. Two goals are achievable with nutrient status information: optimization of crop productivity for maximum yield with minimum fertilizer application, and minimizing nutrient loss to nearby groundwater from the field to avoid nutrient pollution.


In 2012, our team designed and constructed a potentiostat for use with commercial screen-printed 3-electrode sensors in a USDA SBIR funded project. The schematics of the printed circuit board from this project will be used as a guide for designing the new potenitiostat as the central component of the Nitrate Meter. NECi has patented the oxygen removal system to circumvent oxygen interfering with the sensor's operation.

We are currently seeking funding and interest in this project in order to continue research.

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