Film implants could end painful blood sampling.

Film implants could end painful blood sampling.

A simple, cheap implantable sensor could spell the end of painful blood tests for diabetics. Sitting just below the skin, the miniature sensor would remove the need to draw blood to check glucose levels. The sensor is ready to go into testing almost immediately, claim its developers at Penn State University, US.

Craig Grimes and colleagues developed the sensor with technology currently used to prevent shoplifting. The sensor is based on a film of a magnetoelastic polymer, which vibrates at a characteristic frequency in a magnetic field. In anti-theft devices, such films are incorporated into tags which can be sensed wirelessly by transmitters at the shop exit.

Grimes’ team coated the film with a polymer gel that swells in the presence of acid, then covered this layer in a permeable film containing the enzyme glucose oxidase.

The outer film is implanted just beneath the skin where it absorbs blood and converts the glucose present into a mild acid. The inner coating swells, and this changes the characteristic frequency of the magnetoelastic film. The technology is extremely ’friendly’ for implanting; the sensor itself contains no active components, requires no power supply and no connections outside the body; it is also paper-thin and extremely cheap. All the electronics needed are contained in the reader which is the size of a wristwatch and costs around $50 (?27) to make, Grimes says. To make a reading of blood glucose, the patient would just have to wave the sensor, which might be implanted in the back of the hand or the lower arm, over the reader.

The technology isn’t limited to glucose sensing. ’There’s a large variety of biological things, from protein toxins to pathogens, that we’re interesting in detecting,’ Grimes comments.

So far, the team has developed systems for Escherichia coli and Staphylococcus enterotoxin B, and has perfected the technique to the extent that it could enter animal testing almost immediately.

’We’ve been developing the sensors for years now on a real shoestring budget,’ says Grimes. ’If someone came along and said "let’s do it," it could be a real quick process.’

Stuart Nathan