Novel Luminescent Biosensor.

Researchers at the Los Alamos National Laboratory have developed a method of using certain polymers as luminescent sensors to detect and identify biological and chemical agents-almost instantaneously

With the help of molecular intermediaries that bind to the receptor sites of biological and chemical agents, the polymers fluoresce in the presence of these agents. They also may be able to detect viruses such as influenza and HIV, as well as bacteria and proteins. Further development could lead to a lightweight, portable, real-time diagnostic tool that could be used in homes, in clinics, and in the field.

While studying polymers for possible applications in photovoltaics and nonlinear optics, the Los Alamos researchers discovered that certain polymers transfer their electrons over to electronaccepting molecules when excited by laser light. The luminescence of a polymer is "quenched" once that polymer has transferred its electrons to the acceptor molecule, which then is attached to the polymer. The researchers found they could use this effect for sensing by attaching a specific ligand to the acceptor molecule; the new molecular package then gets pulled away from the polymer by the receptor site of a biological or chemical agent, and the polymers luminescence is restored.

All pathogens, proteins, viruses, and bacteria contain receptor sites--those sites enable them to latch onto specific ligands and thus to find routes into the cells they infect. By matching the right ligand with a receptor, researchers can positively identify the specific proteins, viruses, or bacteria.

The process is analogous to a lock and key. The ligand part of the molecular package, called a quencher-tether-ligand (QTL), is the "key" that fits into a receptor site on a specific biological or chemical species.

According to Duncan McBranch, one of the scientists working on the project, a researcher could identify bacteria or viruses simply by placing a sample into an array of sample holders containing different receptor-specific QTLS. The spectrometer would analyze each sample holder simultaneously and identify any bacteria or virus within seconds.

A paper detailing the luminescent-sensor finding was published in the October 1999 issue of the Proceedings of the National Academy of Sciences.