Labeling blood with microscopic bar codes can help in lab testing

Thursday, October 4th 2001, 12:00 am
By: News On 6

WASHINGTON (AP) _ Microscopic particles formed into bar codes may enable medical workers to identify hundreds of different proteins in a single drop of blood, leading to faster and more accurate lab tests.

In a study appearing Friday in the journal Science, scientists report that the micro bar codes, similar to the system stores use to electronically identify products at the cash register, are made by forming metallic atoms into rods so small that it takes 20 to span a human hair.

Michael J. Natan, chief technical officer of SurroMed Inc. in Mountain View, Calif., and a co-author of the study, said atoms of gold, silver, copper and other metals are assembled in banded patterns in the rods. These patterns can then be used as a code when viewed through a microscope.

In laboratory tests, Natan said the tiny rods are attached to proteins, such as antibodies which in turn attach themselves to the target protein in a medical specimen.

Natan said thousands of the minute rods, each with a different metal band pattern and each attached to a different protein, could be placed into a small medical specimen to conduct hundreds of medical lab tests at the same time.

Many medical tests now in use or in development are based on identifying proteins that are related to disease or to disease processes. For instance, heart disease has been linked to elevated levels of certain types of cholesterol and to other compounds such as c-reactive protein. Other disorders may reveal themselves by making specific proteins or enzymes that can be detected in the blood or urine or spinal fluid.

In the past, lab tests required individual specimens for each of the target proteins.

``If we had to use a single sample for every target protein, you could bleed a person dry to do all the measurements that we want to do,'' said Natan. ``With the micro bar codes, we can get thousands proteins, whatever is needed'' from a single small specimen.

In the Science study, Natan and his co-authors at Pennsylvania State University were able to identify and separate rabbit and human proteins when the specimens were mixed together.

``We've shown that we can identify proteins in a single batch and even when that sample is very small,'' said Christine D. Keating of Penn State.

Michael J. Sailor of the University of California, San Diego, said the research is important because it offers a way to perform many medical laboratory tests with a small sample.

Eventually, he said, advanced medical diagnosis and care may require ''100,000 tests from a single drop of blood.''

Current test methods often use dyes that produce particular colors in the presence of specific proteins, said Sailor, ``but seeing a lot of different colors becomes very difficult when you want to do 100,000 tests at once on a finger prick of blood. Also, the dyes tend to fade.''

The micro bar codes using metal rods, he said, would provide almost an unlimited number of identifying patterns.

``Also, the metal barcodes are stable and you can do chemistry with them,'' said Sailor.

He noted that another technique, using identifying dots, is also being developed and may have an advantage over the micro rods because the dots are even smaller than the rods.

Natan said both Penn State and his company have a financial interest in the success of the research.

Science publishes research that has been reviewed and critiqued by panels of scientists.