National Physical Laboratory

Medical test results in minutes

NPL has helped Vivacta, a healthcare diagnostics company, to develop their point-of-care testing technology with a bespoke software analysis tool.

Image courtesy of iStockphoto
Image courtesy of iStockphoto

Summary

Vivacta's point-of-care test uses innovative sensor technology to collect and analyse a patient's blood sample, and diagnose certain health conditions, all in the space of a few minutes. This saves considerable time as the sample does not have to be sent off to a laboratory for testing, and allows for quicker diagnosis and treatment of the patient's health conditions.

NPL helped Vivacta investigate a number of different sensor setups quickly, saving them considerable development time. NPL's analysis tool also helped Vivacta understand their system better, and provided an analysis tool that they could use in future to optimise their sensor technology. In particular, the software allowed Vivacta to understand which parameters in their system were vital to performance and which parameters had little effect.

Background

Currently, most clinical tests for diagnosing a patient's health condition are performed using large, expensive bench-top analysers in centralised hospital labs, which often have a long turnaround time for returning results. This has driven the development of 'point-of-care testing' (POCT) which allows immediate testing and analysis in front of the patient.

There are many benefits to POCT, the most significant of which is how quickly the results are available to healthcare workers and patients. This allows appropriate treatment to be offered much quicker, which is often vital when managing critically ill patients.

The Customer

Vivacta is an in vitro diagnostics company who have developed innovative technology that can quickly measure biological markers at the point-of-care.

Its initial product is a highly sensitive TSH (thyroid-stimulating hormone) assay, which can quickly diagnose thyroid conditions.

Vivacta's patented piezofilm based sensor technology has benefits over other point-of-care detection technologies as it is sensitive, possesses a wide dynamic range, and has good precision. Also, it only needs a tiny sample of whole blood from a finger prick, so a red cell separation step is no longer needed, and the patient doesn't need to have blood collected by venipuncture. Thus, the sample can be collected by a non-trained user, and a phlebotomist is not required. The blood sample is collected in a credit card sized cartridge and placed in a reader where results are reported in 5-10 minutes.

The Challenge

Vivacta needed NPL's help to understand how the different parameters in the cartridge affect the piezofilm response, and also how to best interpret the response in order to get the best signal-to-noise in the system.

Previously, cartridge optimisation was carried out empirically, without a full understanding of the underlying physics - NPL's challenge was to produce a bespoke computer model of the cartridge design.

Vivacta's piezofilm detection technology takes advantage of a phenomenon called the 'piezoelectric effect'. This is where molecular-scale mechanical, or temperature, changes at the surface of a piezofilm produce an electric charge.

In Vivacta's sensor, an antibody is placed on the surface of the piezofilm which binds to the substance that is being analysed (the analyte). Carbon particles in solution are also coated in an antibody which binds to the analyte. The analyte facilitates the binding of the carbon particles to the surface of the sensor. An LED pulse is then fired at the film which creates localised heating of the carbon particles and produces an electric charge. The charge produced depends on the rate of binding between the antibody on the film surface and the target analyte.

Each cartridge contains a number of layers with the innermost layers corresponding to the piezofilm. The amount of electricity generated by the piezofilm is not only dependent on the LED power and the cartridge construction (such as the number of layers) but also their thermo-mechanical properties.

Vivacta initially made contact with NPL through a technology translator working for the Sensors & Instrumentation Knowledge Transfer Network (which NPL helps run), in early 2008. Following several site visits (both to NPL and also Vivacta) NPL put a research team together to respond to Vivacta's pressing needs.

The Solution

NPL had already developed a heat and mass flow modelling package called TherMOL, which was originally designed for modelling laser pulses and had been used in biomaterials projects at NPL. NPL also has world leading expertise in measuring and modelling the properties of piezoelectric and pyroelectric materials, so were well placed to work with Vivacta on this project to optimise the piezo-film cartridge design through modelling.

The Implementation

A heat transfer model of the Vivacta sensor was set up at NPL using the TherMOL software. NPL performed a number of preliminary simulations with air and water samples, and the results showed good agreement with Vivacta's own experimental tests. The initial work also agreed with the qualitative interpretation of the sensor output that Vivacta had developed in the absence of a full physical method

With this validation complete, NPL then developed a bespoke version of TherMOL, to Vivacta's specifications, including a model to predict electric charge from the sensor.

This new version of the software was given to Vivacta and their partners who used it extensively to predict the charge output from a variety of different sensor setups.

The Impact

By developing a bespoke software analysis tool for Vivacta, NPL helped the company investigate a number of different sensor setups quickly. This was particularly useful as it provided confirmation that the empirical results were backed up by the fundamental science and that a number of variables had little influence on system performance. This is particularly critical for understanding the allowable tolerances in the manufacturing processes.

NPL's modelling helped Vivacta understand their system better, and provided an analysis tool that they could continue to use in the future to optimise their sensor technology.

Steve Ross, Vivacta's Head of Research and Development, highlighted how fundamental NPL's assistance was to their project by stating:

"NPL's work has been really useful, understanding the fundamental science behind the technology ensures that we always get the performance that we require. The model should help us to reduce the development time as we work on new applications and future products."

For more information please contact Markys Cain

Find out more about NPL's research in Advanced Materials

Find out more about NPL's work in the Healthcare sector

Do you have a measurement challenge that you'd like NPL's help with? If so, why not apply for NPL's Technology Innovation Fund ?

Last Updated: 9 Oct 2012
Created: 11 Nov 2010

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