Dry Chemistry Strip Technology:
Dry chemistry reagent strip technology has evolved
from a simple litmus paper into a highly advanced technology during the
past 50 years. It converts the labor intensive laboratory tests into a
simple dip-and-read test with results in seconds and transforms the practice
of diagnostic, monitoring testing into a new level. For example, a 45
second test for blood sugar using a single drop of blood was not envisioned
as possible 20 years ago, but now is a every day routine for diabetes.
The accuracy and precision of those blood tests is not less than those
performed in the laboratory using liquid reagents.
Scientists at IBT (Integrated Biomedical Technology,
Inc) have involved in the development of dry chemistry reagent strip for
over 25 years, specifically, in the development of whole blood tests,
urine reagent strips, chemical disinfectant tests and other bio-chemical
tests. The company has received 8 patents plus several more pending on
the chemical testing of the commonly used disinfectants such as bleach,
chlorine, chloramine, peracetic acid, glutaraldehyde and formaldehyde.
Those patented technologies allow us to develop a test strip for testing
of the disinfectants at the levels where have not been possible before.
The basic principle of the dry strip technology,
in fact, is very simple. It involves a simple process of impregnating
the liquid reagents into an absorbing material and drying it in an oven.
A novelist can easily develop a working prototype in three months, yet
may take another three years to perfect the test to the desired performance
characteristics. The most common problems encountered in the strip development
- Lack of thermal stability.
The strip becomes unstable and requires refrigeration for long term
- Uneven color development.
The strip develops a patchy color pattern, which often is difficult
to read and interpret.
- Limited quantitation range.
The strip has narrow quantitation range. It either lacks the sensitivity
for detection of critically low level analyte or, is unable to differentiate
high levels of analyte. In either case, it makes the strip less effective
and could provide false sense of security in certain application.
The strip reaction may be interfered by substances present in the test
sample thus causing false positive or false negative reaction. For detection
of chemical disinfectant, strip specificity or chemical interference
usually is not a problem. In testing of biological fluids, elimination
of potential interferences may become a major roadblock in the development
of the test.
Since the invention of radio immunoassay nearly 50
years ago, tests utilizing the specific binding between antigen and antibody
has evolved into a major analytical format. Such tests provide good sensitivity
and specificity. In order to avoid hazardous radioactive isotope, many
of the test have switched to the use of enzyme, fluorescence chemicals,
color dyes, colored beads or gold conjugate as a signal markers. Some
of these indicator conjugate may alter the biding kinetics of antigen
Optimal binding of antigen antibody requires a proper ionic and hydrophillic
environment. IBT has developed a proprietary cocktail, which will promote
the maximal antigen antibody binding and reduce nonspecific binding of
the antibody to the membrane matrix. The result is a test, which has a
cleaner reaction band and works well in extreme conditions of high salt
or pure water sample media.