Method and apparatus for washing solid media

A method is described for safely and effectively washing solid gels or films containing biological macromolecules such as proteins or nucleic acids. The method involves placing the gels in an open plastic container and decanting a wash solution horizontally so as to leave the gel at the bottom of the container without using external means to hold the gel down. The undamaged gel can then be safely removed and detection experiments can thus be carried out. A preferred apparatus for carrying out this method is also described and consists of an elongated open-topped side spouted tray.

FIELD OF THE INVENTION 
This invention relates to a method for washing biological materials and an 
apparatus for carrying out the method. 
BACKGROUND OF THE INVENTION 
Specific protein, ligand, antibody and nucleic acid probes are used to 
detect macromolecules embedded in polyacrylamide or agarose gels, or 
attached to sheets of nitrocellulose or other related materials. However, 
prior to the detection step, extensive washing is often mandatory and the 
washing process often results in breakage of the sheets or gels. Further, 
these primitive washing procedures often lead to the wash solutions being 
splashed about, potentially causing contamination of the work bench or the 
scientist. Still further, the scientist often decants the wash solution 
while holding the solid media into the inverted tray by hand. This forces 
the scientist or lab assistant to have intimate contact with the 
solutions, some which are strongly radioactive (e.g. .sup.125 I, .sup.32 
P, .sup.35 S, etc.) or carcinosenic. Mere use of gloves will seldom 
provide protection against these agents due to minor imperfections or 
tears in the glove surface. Additionally, the usual plastic gloves used in 
the lab are not radiation resistant. To avoid touching the medium that is 
being washed, a scientist can hold the materials in the tray with forceps; 
however, frequent handling with forceps often leads to marring or tearing 
of the gel or the strip. 
It is thus desirable to have a system for washing biological materials 
which can overcome the above problems. 
It is thus an object of the present invention to create a method for the 
safe and effective washing of biological materials which does not involve 
physically holding down the materials. 
It is also an object of the present invention to provide an apparatus for 
carrying out the safe and effective washing of biological materials 
through the method of the present invention. 
SUMMARY OF THE INVENTION 
The present invention relates to a method of delicately washing biological 
or other macromolecules which avoids the need for physically holding these 
materials in place while a wash solution is being decanted. 
The method of the present invention is particularly useful when the wash 
solutions used are potentially very harmful to the scientist. Through use 
of this method, a wash solution containing biological materials can be 
safely decanted, and the washed biological materials safely removed for 
further study without being marred or torn apart. 
In carrying out the method of the present invention for washing biological 
or other macromolecules, a gel containing biological or other 
macromolecules is placed in a container, after which a wash solution is 
poured generally vertically onto the gel. The wash solution is then 
interacted with the macromolecules in the gel, after which the wash 
solution is decanted in a substantially horizontal direction, causing the 
wash solution to flow out of the container while concurrently causing the 
gel to adhere to the surface of the container and remain on that surface 
in the absence of external means to hold the gel down. 
A side spouted, open-topped tray is particularly useful for carrying out 
this method. Using this apparatus to carry out the method of the present 
invention, one washes biological materials embedded in gels or films by 
first placing them at the bottom of the elongated, open-topped tray. The 
tray, which is preferably made of plastic, is then filled with a wash 
solution, and, after incubation, the solution is decanted through a spout 
on the side of the tray. The gel, which adheres to the bottom surface of 
the tray, remains behind following decantation, and can be removed safely 
and without damage for detection or further experimentation.

DETAILED DESCRIPTION OF THE INVENTION 
The preferred apparatus for carrying out the method of the present 
invention, as observed in FIGS. 1-3, comprises a tray 10 with elongated 
flat bottom 12, side walls 14 integral with the bottom and forming a 
chamber capable of receiving and retaining a wash solution (not shown). 
The tray contains a spout 16 in one of the side walls, disposed so that 
the bottom 18 of the spout 16 lies flush with the bottom 12 of the tray 
10. In the preferred embodiment, the bottom surface 12 of the tray is not 
totally flat, but rather has a forward end 20 which is slightly inclined 
upwards. This upward incline is helpful in retaining the biological media 
in the tray while the solution is decanted, as will be described in the 
description of the method below. 
The tray can also include indented corners 22 which sit on top of the 
corners 24 of the tray 10. This allows the trays to be stacked if one 
desires to utilize or agitate several of the trays at one time. The 
stacked trays are observable in FIG. 3. 
It is preferred that the tray be constructed of lucite or other related 
plastic material. The present invention takes advantage of the fact that 
gels of polyacrylamide or agarose, or nitrocellulose sheets and other 
similar materials have a physical affinity for these types of plastic 
surfaces. When solid media is slightly dried, it will tend to remain 
adhered to the flat bottom surface as the used solution flows away. 
Although the invention can be constructed as specified above, it can also 
be made by modification of a conventional tissue culture flask. Such 
culture flasks are known in the art, and types of these flasks are 
observed in U.S. Pat. Nos. 4,334,028 and 3,870,602. The tray of the 
present invention can be constructed by removing the top face of the 
conventional tissue culture flask by any suitable means. Preferably, the 
top is removed so as to leave the indented corners 22 of the tray which 
allow stacking. This operation has been performed in two ways: (a) the 
face was removed by gently tapping with a hammer and removing pieces of 
broken plastic with a broad nosed pliers, and (b) cutting the upper face 
out with an electrically heated probe. 
The tray, whether built from scratch, or made by altering a tissue culture 
flask, can be made in different sizes to accommodate different washing 
assignments. Trays have been made by modifying conventional tissue culture 
flasks which ranged from 75 cm.sup.2 to 500 cm.sup.2 surface area. 
Once constructed, the open-topped spouted tray of the present invention is 
particularly useful in carrying out the safe and effective washing of 
biological materials using the method of the present invention. However, 
this is not the only tray which could be used, and many other suitable 
containers can be employed in the method of the present invention. 
Using the apparatus described above, the preferred method of the present 
invention is as follows: 
Gels or films containing macromolecules are placed into the tray directly 
from, e.g., an electrophoresis apparatus or a blot assembly. The tray is 
then filled with a wash solution until it is no more than half full. At 
this point the gel or film in the tray can be incubated with or without 
automatic agitation from a shaker. If agitation speed is moderate (about 
one cycle per second) the solution will remain in the tray without 
spillage. If faster agitation is desired, however, it is possible to seal 
the tray with parafilm or saran wrap, and this will prevent spillage. 
Once incubated, the spout of the tray may be opened and the wash solution 
may be decanted. Due to the adherence of solid media to the plastic 
surface of the tray, and due to the upward incline at the spouted front 
end of the tray, the solid biological material embedded in the gel or 
sheet will remain at the bottom of the tray while the wash solution is 
removed through the spout. If desired, the entry from the tray chamber to 
the spout can be fitted with a vertical piece of plastic which will act as 
a meshwork at the point of exit for the solution. This allows one to 
handle and recover very thin pieces of nitrocellulose which might 
otherwise be washed away. 
After this first decantation, it is possible to replenish the solution for 
further washes, or even change to a new solution when desired. When one 
has completed the washing, the biological media at the bottom of the tray 
can be removed in any suitable fashion. One way to remove the solid medium 
is by leaving the last wash solution undecanted, and then lifting out the 
materials using a plastic pancake turner. Alternatively, one can decant 
the solution as described above, and place a piece of dry filter paper or 
damp dialysis bag backing on the remaining gel or nitrocellulose strip. 
Then, removal can be accomplished simply by turning the tray over, and the 
protected solid media can be safely deposited in a suitable container or 
on another convenient surface. 
As a result of this method, one obtains an undamaged sample of 
macromolecules in a sheet or a gel which is now ready for detection or 
further experimentation. Further, this unbroken sample is obtained without 
the contamination of lab or scientist which most often accompanied the 
prior art methods of washing these gelled biological materials. 
Although the invention has been described in considerable detail, it will 
be apparent that numerous modifications and variations are possible, 
within the spirit and scope of the invention.