From: Avian Diseases Vol 28, No. 4 October-December 1982
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Summary
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A system for storing frozen serum samples
using hollow plastic cards is described. This system
offers improved economy of materials and storage spaceand
also facilitates rapid retrieval of samples.
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Research Note
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Official diagnostic laboratories commonly
freeze sera from routine accessions for future reference.
Material collected for specific serological surveys
should be likewise stored. Such sera collected over a
period of years can be very useful in retrospective
epidemiological investigations when previously unknown
infectious diseases are described. The main limitation on
the size of such collections of sera is the amount of
freezer space available. Glass vials and ampules have
been commonly used to store sera but they occupy a lot of
space if stored in boxes which allow rapid identification
and retrieval of samples. Plastic microtitration plates
have many advantagesover conventional methods: They are
compact and facilitate the identification of individual
sera by a grid system (1). Their main disadvantage is the
necessity to thaw up to 96 samples at one time resulting
in unnecessary freeze-thaw cycles for many sera. Other
disadvantages are the small well capacity (maximum 275
mcl) and the rather high cost of plates in some
countries. In view of these disadvantages a method of
serum storage using hollow plastic cards was developed.
The corrugated plastic card used (Polionda 3mm, Tuffy
Habib S.A. Rio de Janeiro Brazil) appears as a linear
series of hexagons in cross section, each of which
represents a compartment in which serum can be stored.
This laboratory has had good results with cards of 5 x x
cms(for 10 samples, 0.5ml in each). The cards may be
siliconised by immersiojn in 0.35% polysiloxane (24
Emulsion, Dow Corning, Sao Paulo Brazil). One of the open
edges of each card is sealed with heat and pressure. One
corner of the opposite edge is removed to facilitate
orientation of the card within the filing system. Figure
1 shows a storage card ready for use.
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Figure 1 Storage card ready for use. The
larger the dimension of the X axis, the larger the volume
that can be stored in each compartment. The larger the
dimension in the Y axis, the larger the number of samples
that can be stored in each card.
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Filing boxes may be made from wood or
other material and notches can be cut in their sides.
Boxes designed to store photographic slides may be
acquired in specialised shops and are ideal for the size
of card described. Sera should be carefully placed in
each compartment with Pasteur pipettes, beginning at the
bottom to avoid air bubble formation (Fig.2). A few drops
of melted paraffin may be used to seal the end of each
compartment. Each card should be properly identified and
its contents registered in a book before placing them in
the storage box at -20 C (Fig. 3).
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Figure 2. Storage card ready for use (right) and
already loaded with sera and identified. |
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Figure 3. A photographic slide box may be used to
file the cards. This box holds 1600-2000 serum samples .
On the left is the number of microtitration plates needed
to hold a similar number of samples. |
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The shape of the storage cards results in
rapid freezing and thawing of samples and efficient use
of available space. Samples can be removed from the
storage cards by means of a Pasteur pipette or
plunger-type micropipette. |
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References
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1. Whittemore, A.D. and J.E. Williams
Microsystem for collecting and shipping diagnostic sera.
Appl. Microbiol. 24:671-672 1972 |