Magnetic biosensor for point-of-care diagnostics

Current methods of testing for drugs, for example roadside testing for drugs-of-abuse, can require trained operators and may take around 10 to 15 minutes to complete. The need has therefore long been felt for a test offering the speed and convenience of the alcohol breathalyzer. Philips is developing a new technique that is faster and requires less handling than the current techniques.

Enabling fast convenient testing

The new test makes use of magnetic particles that have been developed to bind with selected drug molecules. Saliva taken from the mouth is mixed with fluid containing these particles which then passes over a sensor array. The presence or absence of these magnetic particles is detected by a magnetic-field sensor beneath the array which then generates a signal indicating a positive or negative test result. The aim is to produce a fast, reliable and convenient testing device that includes a disposable sensing element. The giant magnetic resistive (GMR) sensor technology used in this test was developed within Philips and has now been transferred to a venture within the company’s Healthcare Incubator.

Interconnect design and microfluidic structures Philips Applied Technologies is supporting the venture by developing interconnect designs that provide reliable electronic control and signal readout in the liquid environment in which the sensor will operate. We are also developing the microfluidic structures required for efficiently transporting the test fluid to the sensor array. Determining the most suitable structures is a significant challenge involving a fast design, make and evaluation cycle. This comprises the development of functional designs using advanced simulation techniques, generation of 3D CAD output for fabrication of prototypes, material property measurements, prototypes fabrication by injection molding, microfluidic chip assembly where the sensors are bonded to the microfluidic structures, and finally fluidic evaluation of the devices in the field.

One of the aims of the venture is to produce a roadside ‘through-the-window’ tester that will allow police and other authorities to conduct a screening test for drugs-of-abuse in under a minute. Other possible applications in the medical sector include allergy testing, urine testing and testing of domestic air and water quality. Outside the medical area the new fast, convenient testing technique could offer important benefits in the testing of nutrition and vitamin levels in food, breast-milk quality and pollution levels.