New device is out of sight

Researchers from the US Department of Energy’s Lawrence Livermore National Laboratory and MiniMed Inc. are developing a medical implant that may give diabetics a welcome change to their daily routine.

Diabetics face a daily routine of finger pricking, glucose monitoring and, for some, insulin injections. Failure to maintain the routine could lead to an assortment of anomalies including kidney and heart disease and blindness.

The implantable device is said to be composed of a glucose sensor imbedded under the skin and an insulin pump implanted in the abdomen and has been designed to work like an artificial pancreas to signal when the body needs insulin and deliver it in precise doses.

Insulin pumps are said to be an attractive alternative to injections because they closely match the natural action of the pancreas by releasing small amounts of shorter-acting insulin.

The pump, manufactured by MiniMed, is a 2.3-in.-diameter by 0.8-in.-thick titanium disk that includes a reservoir for the insulin. Unlike injections, which can pool insulin in the tissues before it slowly dispenses into the bloodstream, the pump infuses it directly into the abdomen where it is more quickly absorbed.

Livermore’s new sensor mechanism automates the process by telling the internal pump when to administer the insulin. The sensor uses fluorescent transducer molecules to measure light reflected in the tissues instead of measuring glucose in the blood.

‘The detection mechanism uses a molecule that normally has low fluorescence because, once excited by light, electrons are transferred from one part of the molecule to another, preventing bright fluorescence from occurring,’ said Stephen Lane, a Livermore physicist and associate program leader of the Medical Technology Program. ‘When bound to glucose, however, the glucose molecule prevents the electrons from interfering with the fluorescence, and the molecule becomes a bright fluorescent emitter. The more glucose that is present, the more molecules that become bright emitters.’

The fluorescent molecules are then placed within a biocompatible polymer implant being developed by MinMed, and transmits the information to the pump through a device worn on the wrist. The sensor components work in conjunction with the pump, creating a ‘biomechanical’ pancreas.