POC testing? There's an app for that...

Testing for infectious diseases in minutes rather than days is becoming a reality using new smartphone-based biosensor technology says Dale Athey

Infectious diseases like flu afflict millions of people every year, bringing misery to sufferers with a hard hitting virus that can rapidly sweep through populations and, in some cases whole continents, in a matter of weeks.

Identifying and treating these diseases also has considerable cost implications for those responsible for delivering health protection services, while placing a further strain on often already overburdened healthcare systems, delaying treatment and endangering human lives.

Success in treating many infectious diseases lies in the speed of response; antiviral drugs are at their most effective within the first three days of the onset of symptoms, so the value to medical staff of having to hand easy-to-use, quick and reliable ways to test patients, whether they are in a local clinic, doctor’s surgery or a remote village hundreds of miles from the nearest healthcare facility, cannot be overstated.

As a result, there is a strong international trend to move the testing and monitoring of infectious diseases outside of the confines of specialist hospitals by using point of care (POC) diagnostics.

For example, in the UK, previous reports by the House of Lords and the government response recommended increased testing in non-tertiary referral centres and GP surgeries as part of an approach aimed at earlier and better detection and diagnosis of some diseases to deliver improvements in patient outcomes.

In some areas, such as HIV testing for example, there is already a strong international trend towards POC testing and this approach is extending into other areas including the diagnosis of respiratory viruses.

These factors have driven forward the development of a new generation of highly advanced POC testing and detection technologies using the advantages offered by new biosensor devices and smartphones and which have the potential to transform the way flu and other infectious diseases can be diagnosed.

The most advanced POC diagnostic approach combines state-of-the-art technology, specialist biosensor materials and advanced electronics in a small hand held device for the accurate detection of illnesses from patient supplied samples.

Chief among these is a new mobile phone enabled biosensor from medical device and diagnostic specialist OJ-Bio, a joint venture between the Newcastle-based biotechnology company Orla Protein Technologies Ltd and the Japan Radio Company (JRC).

In this unique collaboration, Orla provides the specialist biosensor materials that are combined with JRC’s advanced electronics capability to create a specialist ‘biochip’ technology platform.

This work has involved taking shear horizontal Surface Acoustic Wave (SAW) chips and coating them with new protein technology to create a device that gives highly specific responses when coming into contact with samples containing markers of the disease concerned.

The reaction that takes place is turned into an electronic signal which can be combined with a small reader to transmit and receive data in real time.

SAW chips have been in commercial use for over 40 years and are widely used in the telecoms industry and base stations where they act as bandpass filters. Now, for the first time, the combination of novel antibodies, nanoparticles and multiplexing methods enables SAW technology to be used to its full potential with biological samples, with the resulting devices being able to detect disease antigens in samples from serum, urine or saliva.

The new chips are designed and manufactured to allow operation in liquids with high sensivity to perform as an immunoassay device that detects the mass and viscosity changes of a biological molecule on the surface of the SAW sensor devices.

The chips are fabricated using a delay line on quartz substrates, comprising transmitting and receiving interdigital transducers with a biochemical reaction area between them. The transducers are protected from liquids by a glass lid, epoxy walls and a membrane constructed using a photolithograpy technique that allows liquid samples to be directly applied onto the chip.

The sensor area is modified with capture antibodies that are specific to each target marker and are held in the correct orientation to react with disease antigens. When the target marker in solution binds to the immobilised capture antibody, the “added mass” of the binding causes a shift in the phase angle of the surface acoustic wave passing across the chip surface and this is translated into an electronic signal.

Different capture coatings can be tested immediately on a working prototype measurement unit so that robust assays can be developed, with data being transferred to a simple hand held device like a mobile phone for display of results.

In this way disposable SAW sensors that can be inserted into an electric reader to detect multiple antigen-antibody reactions via changes in the phase/amplitude of the input/output signals. This will allow medical staff to perform rapid near-patient testing without the need for complex or cumbersome equipment.

This makes the technology ideal for remote disease monitoring, with many applications for rural use or situations where clinical readings are needed without patient transfer. They are equally well-suited for use in High Street or walk-in clinics and for consumer diagnostic applications.

As part of the initial research into the development of accurate, rapid and low-cost, POC testing for respiratory viruses, OJ-Bio has recently led a project in which a new SAW biosensor was developed and then tested in collaboration with the Health Protection Agency  in Newcastle.

The so-called VIRASENS project was undertaken to pioneer the combination of electronics and biotechnology as part of the development of a prototype PoC diagnostic biosensor device for respiratory virus detection.

Work was undertaken into the detection of three respiratory viruses, (Respiratory Syncytial Virus (RSV), Influenza A and Influenza B) in clinical samples collected by the HPA laboratory in Newcastle-upon-Tyne.

During the initial stages of product research and development, the HPA collected nasal secretions, nose/throat swabs and nasal aspirates from patients and used these samples to test the capability of the OJ-Bio biosensor against the current benchmark polymerase chain reaction method as well as alongside another commercial POC test.

Assays were performed by mounting SAW chips into specially designed fixtures connected to a control box. Clinical samples and controls were added to the chip surface followed by virus specific gold-conjugated secondary antibody for five minutes. The amount of virus binding to the chip surface was recorded in degrees of phase shift, with a reduction in the phase angle (ie a negative phase shift) indicting the presence of the influenza virus.

An example of the type of data obtained on the SAW device is shown below (see two separate data charts). These proved that the SAW biosensor technology can provide accurate results in around 10 minutes, had good levels of diagnostic sensitivity for the three test viruses (total 93% when compared to the HPA lab-based PCR method, the ‘gold standard’ for respiratory testing) and did not give false positives, showing 100% specificity even when other viral analytes were present.

These results compare favourably to currently available rapid tests for Flu and RSV diagnosis which have demonstrated sensitivity between 4.4-70% and specificity between 50.5-100% and demonstrate that the SAW technology can provide a sensitive POC test for Influenza and RSV diagnosis.

Importantly, along with the POC potential, results from the SAW biosensor device can be displayed on a complementary (App enabled) hand held reading device such as a mobile phone and can be wirelessly transmitted to a central resource for remote connectivity to healthcare networks and facilities.

Following this work, government funding for further development work into its innovative new technology has recently been secured from the UK Technology Strategy Board’s Biomedical Catalyst programme.

The latest funding approval will enable the company to continue its work by developing the lab-based prototypes described above into a fully functional pilot device capable of carrying out large scale clinical trials.

The next stage of manufacture will involve considerable innovation in design and production of the SAW biochip, including the design and first testing of a new ‘multi-parameter chip’, and also in the reader, where functions will be placed within a handheld format which is wireless enabled.

In addition software that is currently designed for the PC interface on the current prototype will be developed for the handheld device. The optimised assays which have been developed for flu A&B and RSV on the existing prototypes will be optimised on the current platform (stability, reproducibility etc.) for transfer to the new devices and biochips. As a final stage, more extensive trials will be performed on the device which will be close to the final product format.

The SAW biosensor technology has already effectively demonstrated its potential as a low cost tester which has the potential to revolutionise the speed of diagnosis and treatment, hitting the flu virus hard at its source and inhibiting its ability to spread.

However, the potential applications of this concept are far wider; at its core lies a versatile ‘biochip’ platform technology for rapid wireless immunodiagnostic testing which could be adapted for potential applications in PoC diagnostics for other infectious diseases such as HIV and periodontal gum disease, which also affect millions of people and cost billions in treatment programmes.

In a separate project, OJ-Bio is working with researchers from University College London (UCL) on the development of a POC device capable of detecting HIV marker proteins in human blood quickly and effectively.

So far the technology has been proven to work using model HIV samples and new funding from the National Institute for Health Research (NIHR) Invention for Innovation (i4i) programme will enable

The beauty of this technology in this application is its inherent sensitivity to low levels of multiple markers, with the potential for much earlier diagnosis of HIV. This will empower patients to gain earlier access to antiretroviral treatment with better associated health outcomes.

Contact: www.oj-bio.com