In formulation chemistry, compounds are
mixed to get a product with the desired characteristics. Examples of
formulations are adhesives, paints, inks, cosmetics, detergents, pesticides
and pharmaceuticals. Depending upon what a product is needed for and
how it will be used or applied, needed qualities may include adhesiveness,
weather resistance, correct texture, long or short shelf life or stability,
biodegradability, specificity and attractiveness. Some of these properties
(or the correct level of these properties) may not be inherent in an
original product and must be added by changing its formulation.
One of the most difficult problems faced by formulation chemists at
NWRC is finding a way for products (vaccines, baits etc.) to be delivered
orally to wildlife species. This delivery method is desired due to the
fact that wildlife species are much more inaccessible than livestock
or companion animals.
In some cases, compounds used by NWRC are proteins which, once ingested,
are recognized as food by the body. Stomach acids will then be secreted,
destroying the active ingredients before they can act. One way to ensure
compounds aren't destroyed in an anima's stomach is to encapsulate them
(enclose them in a capsule). These encapsulated formulations are protected
in the rumen and stomach and later release the active ingredients in
the small intestine to increase absorption. In another example, active
ingredients have been incorporated into a synthetic grit matrix to develop
a species-specific controlled-release formulation for management of
pest birds. Following ingestion of the grit formulation, the active
ingredient is released as the matrix is slowly worn down in the crop
of the bird. Controlling size of grit pieces offers a means to decrease
ingestion by nontarget birds.
Below are other instances in which formulation chemists have contributed
to products developed at NWRC.
is a narcotic that, when used in concentrations of less than 2.5%, can
anesthetize birds for removal from a location but not kill them. In
early days of use, alpha-chloralose was mixed with butter and squirted
into bread for delivery. A more easily produced and delivered product
was needed. Tests were completed to determine how much active ingredient
was necessary to achieve the desired effect in target species. Formulation
chemists then produced an alpha-chloralose tablet with the active ingredient
held together by a binding agent (common binding agents are lactose,
microcrystalline cellulose, etc.). The tablet also had to have properties
that allowed it to dissolve in water so the alpha-chloralose was available
for ingestion. Formulation chemists added color to the tablets so that
field operatives could distinguish the 3 different strengths of the
Oral Rabies Vaccine Development
Tetracycline is a compound that is employed as a biomarker in vaccines
or other orally delivered products. By looking for tetracycline in animal
tissue samples (primarily teeth and bones), scientists can determine
whether the target animal populations are ingesting the associated vaccine.
For example, tetracycline is used in rabies
vaccines. Because some animals, such as skunks, don’t like the
taste of tetracycline, formulation chemists had to find a way to to
mask its odor. Additionally, baits used for larger animals like raccoons
weren’t useful for skunks because the skunks often nibbled only
around the edges of the bait, not swallowing it. The vaccine dose, in
the middle of the bait, didn’t get delivered. Thus, the tetracycline
was re-formulated as small particles layered with a taste-masking coating
and applied directly to the vaccine sachet (a plastic envelope with
the liquid vaccine inside), yielding much higher bait take and improved
correlation between marking and identifiable levels of antibodies to
an avicide registered for use on some bird species, has been an extremely
difficult problem because of the reactivity of the molecule (with light,
air, etc.). DRC-1339 comes from the manufacturer as a powder. To be
used as part of a rice bait, it must be formulated with an adhesive
to stick to the rice. Unfortunately, the developed bait turns orange
when used in the field, and birds won’t eat it. Attempts are being
made to alter rice properties so it doesn’t react with DRC-1339
(for example, oxidizing it).
Brown Treesnake Baits
To trap the brown
treesnake, an invasive species on Guam, live mice are used as baits
within the live traps. These mice are separated from the main portion
of the trap and cannot be actually be reached by the snakes. To sustain
the mice for long periods of time, potatoes are placed in the live trap
as a source of moisture for the mice. Grain bait blocks are also placed
in the traps to provide food. Because potatoes had to be shipped to
Guam, and people had to be hired to make the bait blocks, NWRC chemists
were asked to develop a more efficient way of providing sustenance for
the mice. The chemists were able to formulate a new product with a Konjac
matrix (Konjac is a water-swellable dietary fiber used as a thickener
and stabilizer) that held water and grain together
as a one product, thus improving trapping procedures.
M-44 is a mechanical device that, when triggered, expels cyanide.
Canids are lured to the M-44 by the use of odor attractants. Initially,
individual trappers were mixing their own variations of attractants.
These users, however, wanted a more uniform and easily reproducible
attractant, so NWRC chemists developed a product that, while attractive
to canids, minimized nontarget impacts. The lure was composed of gelatin
(regular Knox gelatin) and Konjac (for a binding matrix) glycerin, and
some corn oil (to better hold odors).
Melting of baits was another problem to be solved. The bait was developed
so that it was more thermally stable and could be used in warm climate
states such as Texas as well as cooler areas such as Wyoming.
Goal and Objectives