The electrophoresis system that I had made previously required cutting expensive acrylic and then fusing the acrylic pieces to make the buffer tank, the gel tray, etc. A lot of work with the risk of leaks.
I was trying to figure out what to do with small parts cabinets as I did not need them after making my drawer chest. Realized the small parts drawers would make great electrophoresis tanks if they were watertight and if they could withstand boiling water. A quick test showed that the drawers were watertight and could hold boiling water without any distortion.
Images show the finished unit separating DNA (the colored bands are DNA loading dyes). A 3D diagram of the electrophoresis system shows the system is made of three parts; the buffer tank made from the parts drawer,two electrode holdres, and the gel tray. The gel tray is held in place with plastic squares attached to the side of the tank. The plastic square also supports the electrodes that slide into space. A simplified top view shows the layout of the plastic squares (support), the gel tray, and the electrode holders. The whole build is summarized in a youtube video with bad music.
Step 1: Making the Electrophoresis Buffer Tank
To make the electrophoresis buffer tank, I used the plastic drawers from a small parts cabinet to which I attached the small plastic squares cut out from plastic picture holders bought from a dollar store. The plastic squares were attached with Goof-off solvent. These plastic squares would act as stops for the gel tray and support the electrode holders.
Step 2: Making the Electrode Holders
Removable electrodes worked well in my previous build so did the same here. An L-shaped piece of plastic was made from the dollar store plastic picture holder in which a hole was drilled to hold a female jack. The plastic was bent at 90 degrees with a hot air source. The L-shaped piece was then glued to another piece that would form the vertical plate for the electrode holder. Wired female sockets were then glued into place into the L-hole and the jacks were covered with plastic 25ml pipette pieces that fit perfectly over the wire and the female sockets. Made three sets of electrode holders.
For the black negative electrodes, nichrome wires from a discarded toaster element were used. The wire was held by fusing the plastic over one end of the wire, stretching the wire to the other end of the electrode plate and passing them through slots cut into the other end of the plate. The wire was then covered with a piece of plastic tubing and then soldered to the copper wire coming from the female socket. For the red positive electrodes, platinum wire was used. Exposed wires were covered with plastic goop (plastic pieces melted in goof-off).
Step 3: Making the Gel Tray
The gel tray was made from the picture frame plastic with ends bent over at 90 degrees with a hot air gun. Slots for combs were drawn in and cut with a hacksaw.
Combs were modified from existing gel combs from commercial disposable gels. Gel combs can also be made from plastic pieces as shown in the previous instructable.
A casting tray was also made in a similar way by bending over ends of a plastic piece just a bit larger than the gel tray. Rubber pieces were glued to the casting tray to create a seal when the gel tray was placed in the casting tray.
To cast a gel, the gel tray is placed inside the casting tray. The comb in put in place and molten agarose dissolved in electrophoresis buffer cooled to about 60C is poured into the gel tray. Once the gel has solidified the comb is removed. The gel tray is removed from the casting tray and placed into the buffer tank.
Step 4: Running the Gel
The gel tray with the solidified agarose in covered with buffer, the electrode plates placed into the tank, and wires attached to a power supply. DNA containing marking dyes and fluorescent stain is loaded into the wells created by the comb and the power turned on.
DNA migrates towards the positive electrode with smaller pieces moving faster under the electric field.
DNA bands are visualized by UV or blue light that excites the fluorescent dye bound to the DNA resulting in the emission of green or orange color wherever DNA is present.