May 02, /Researchers at the University of California (UCSD; San Diego) have developed nanoscale polymer-based sensors for implanting into the human body to monitor conditions including the delivery of drugs, the strain on a weak joint, or the healing of a suture. A key advantage with biopolymers is that they are biocompatible and do not corrode in the body. The innovation is featured in a recent issue of Science.

The researchers, led by Michael J. Sailor, professor/chemistry at UCSD, developed a method to transfer the optical properties of silicon sensors, previously thought to be the exclusive domain of nanoscale crystalline materials such as porous silicon, to a range of organic polymers. But porous silicon, unlike polymer sensors, is not always biocompatible, is not flexible and can corrode, the researchers say. The researchers say they tested nanosensors made from polylactic acid to demonstrate the monitoring of drug delivery in the body. The results showed that the sensors could accurately determine the rate of drug delivery.

Sailor: New application for biopolymers.

The polymer-based sensors reflect a wide range of wavelengths, some of which are not absorbed by the human body, that can be picked up by light-sensing equipment. A physician monitoring a joint with an implanted polymer sensor can see changes in the reflection spectrum of the sensor as the joint is stressed at different angles, the researchers say. Biodegradable polymers in drug delivery dissolve at a set rate in the presence of a given drug; as the sensor degrades its changing state would signal the level of drug delivery. Such biodegradable polymers may be used to monitor the delivery of antiviral drugs, pain and chemotherapy medications, and contraceptives, Sailor says.

Separately, Sailor and his research colleagues have developed sensors from porous silicon dust-sized chips for applications such as chemical or biological detection systems.