Biosensing

Selection includes high selectivity and low detection limit sensors. For 20 years WPI has led the market for ion-sensitive electrochemical sensors. We offer a range of macro and micro biosensors for monitoring nitric oxide, hydrogen peroxide, oxygen, carbon monoxide and hydrogen sulfide.

WPI’s biosensors are unique, because they offer a high selectivity and low detection limit (down to nM concentration) with a broad dynamic range; covering physiological concentration of species with different sizes from nM to mM. The majority of our sensors are the only commercially available sensors in the world. Scientists across a variety of disciplines have relied on our sensors for over 25 years. These scientists use WPI’s sensors for research performed in universities, hospitals, biomedical research labs, pharmaceutical companies, food/ nutrition research labs, environmental monitoring centres and military labs. Our popular biosensors are listed in thousands of publications.

Free Radical Analyzers

Our free radical analyzers are used in biosensing experiments to detect oxygen, nitric oxide, carbon dioxide, hydrogen peroxide, hydrogen sulfide and glucose, using WPI ion-species specific biosensors. Our TBR series biosensing analyzers can be set to monitor the specific species of interest, and the 4-channel TBR4100 can monitor four biosensors simultaneously. While the TBR biosensing device is commonly used as a nitric oxide analyzer, it is perfect for real-time detection and measurement of a variety of redox-reactive species using the electrochemical (amperometric) detection principle. This series of optically isolated biosensing analyzers has ultra low noise and independently operated channels.

Biosensors Designed for Selective Detection

Choosing the right sensor for your application is critical for successful research. The manufacturer's specifications provide valuable information for selecting your sensor. Consider the following five performance factors in reference to your application:

Response – Electrochemical electrodes produce changes in current in response to changes in concentration. “Response” is most often specified in terms of the amount of current per concentration unit: nA/µM or pA/nM, etc. The larger the current per concentration the higher the sensitivity of the sensor.

Detection Limit – Detection limit is the minimum change in concentration that can be reliably seen. This specification is directly related to the noise of the sensor. A sensor with a 100nA/μM response but a 3 µM detection limit is not as good as a 10nA/μM response sensor with a 1 µM detection limit.

Free Radical Detection – The best sensors have low detection limits and high sensitivity. A sensor can have a low detection limit and a good response, however, to be useful in long term studies it must be stable when temperature and concentration are constant. A drifting baseline, if monotonic, can be corrected, but wandering baselines limit the utility of sensors to short experiments.

Selectivity – It is a rare instance that the ion species of interest is the only ion in the medium to be measured. In a perfect world your sensor would respond ONLY to the ion of interest. In reality there is always some contribution from competing species. The lower the contribution the better.

Linearity – For an electrode to be useful and easy to calibrate the response must be “linear” with changes in concentration over the range of interest. Non-linear behavior requires special curve fit software to calibrate the sensors. This approach is more time consuming and can be unreliable. “Good” linearity is expressed by a R² of 0.980 or higher. (1.00 is perfect.) All of the electrochemical sensors made by WPI are 0.98 or better.

The table below presents the specifications of WPI’s macro sensors (2 mm sensor) and microsensors.

Macro Sensors

SPECIES	Carbon Monoxide	Nitric Oxide	Hydrogen Peroxide	Oxygen	Hydrogen Sulfide
Order Number	ISO-COP-2	ISO-NOP	ISO-HPO-2	ISO-OXY-2	ISO-H2S-2
Available Diameters	2 mm	2 mm	2 mm	2 mm	2 mm
Response Time	< 10 sec	< 5 sec	< 5 sec	< 10 sec	< 5 sec
Detection Limit/Range	10 nM to 10 µM	1 nM to 40 µM*	< 100 nM to 100 µM	0.1% - 100%	< 5 nM to 100 µM
Sensitivity	~0.5 pA/nM	≤ 2 pA/nM	8 pA/µM	0.3 - 0.6nA/%	2 pA/nM
Drift	< 1 pA/min	< 1 pA/min	< 1 pA/min	≥ 1%/min	< 1 pA/min
Temperature Dependent	Yes	Yes	Yes	Yes	Yes
Physiological Interference	nitric oxide	NaNO2 (10-6 or better)	None	None	None

*Higher detection limit available on request — contact for custom pricing

Micro Sensors

Order Number	Species	Qty /Pk	Fiber Diameter (µm)	Tip Length (mm)	Response Time (sec)	Lowest Detection Limit/Range (nM)	Nominal Sensitivity - New Sensor (pA/nM)
ISO-NOPF200	Nitric Oxide	2	200	1-5	<5	0.2	≥ 10
ISO-NOPF200-Lxx		2	200	1-10	<5	0.2	≥ 20
ISO-NOPF100		2	100	1-5	<5	0.2	≥ 6
ISO-NOPF100-Lxx		2	100	1-5	<5	0.2	≥ 20
ISO-NOPF500-Cxx		2	500	5-10	<10	0.2	≥ 20
ISO-NOP3005		3	30	0.5	<3	1	≥ 0.2
ISO-NOP3020		3	30	2	<3	1	≥ 1
ISO-NOP007		3	7	2	<3	0.5	≥ 0.5
ISO-NOPNM		3	7 Conical tip: 100 nm	2	<3	0.5	≥ 0.5
ISO-HPO-100	Hydrogen Peroxide	3	100	1-5	<5	1	≥ 1
ISO-HPO-100-L	Hydrogen Peroxide	2	100	1-5	<5	1	≥ 1
ISO-H2S-100-Cxx	Hydrogen Sulfide	2	100	2-5	<5	<5	1-4