If you are doing biological
research chances are very high that you must have at least once used a
microtiter plate 96-well high throughput (HTP) also commonly know as 96-well.
For some the HTP or even a hyper HTP (384-well) is bread and butter. The
American National Standards Institute has even defined the dimensions for
96-well format. But have you ever wondered why is it is a 96-well not any other
number. Well if you have some thoughts it will be great to hear as well. But
here is what we in the lab came up with, ‘we’ here are myself, John, Marvin,
Enfu etc., thanks to lively discussion and contributions.
A quick Google search will give
you the history of microtiter plate and here is a quick primer. The very first microtiter plate can be
traced back to the Hungarian scientist Dr. Gyola Takátsy around 1950s(1-3).
Dr. Takátsy used this innovative technique for influenza virus detection during
an epidemic. He published the idea, which was picked up by the Linbro Company and
made 96-well microplate. More refinement of microtiter plate, automation and
wide applications came along afterwards. A list of further reading can be found
at the end if you would like to know more about the evolution of microtiter
plate1-6.
So after reading all about the history/evolution it is
still not clear how Dr. Takátsy came to a conclusion that 12x8=96-well is the
best format. It seems that Dr. Takátsy very first microtiter plate was a
6x12=72-well, he also has tried 10x10=100-well. To quote from an article4
“For time-saving, Dr. Takátsy soon replaced the wire loops by thin iron
or steel knitting needles that could be flame-sterilized. He arranged the
needles in a way that he could keep them in his hands without problems. This
led to a plate with 8 x 12 wells that could be quickly and easily filled the
96-well plate was born”.
The 96-well format has began its
humble being from early 1950’s, this rules out the ‘chicken-egg problem’ of
which is earlier the 8x12 tip boxes or 8x12 plate. Thus the 96-well format has clearly
dictated the market to make 96 tip boxes, multi-channel pipette, PCR blocks
etc.,
Coming back to the original
question of why 96? Conventionally a 10x10=100-well seems to be an ideal plate,
100 a round composite number. Where in the first instance 96 might look like a
random number, but it the highest number below 100 to have maximum positive
divisors (96 is divisible by: 1, 96 and 2,3,4,6,8,12,16,24,32,48). This means
one can make easy partitions, serial dilutions, duplications and combinations. There
smaller options too but they are basically divisors or 96 (for eg., 24-well
crystallization plate/tissue culture plate). Nextal has made a new format of 6x3=18-well crystallization
plate, but again not a square plate (see below).
A perfect 10x10=100-well will
give you a square block and it is quite easy to mix-up with a four
equiv-dimension block. Although to some extent this argument holds true for a
rectangular 8x12 block too, but there is only one possible way doing wrong with
a rectangular block. Plus a 2:3 ratio as originally Dr. Takátsy said is easy to
hold/handle by hand.
We can argue more good things
about the 8x12=96-well format, but to some extent it sounds like there is ‘no
choice of other option so we like it’. It is nearly impossible to even think
about another format (the 384 and more are mere multiplications of 96).
According to Dr Peter Banks5 the 2009 global market for microplates
is ~$500million. If you add up the entire tip box formats and other instrument
formats the sum will go considerably higher. So for the moment sit tight and do
your HTP assay in 96-well format (or more) thinking how good the 96-well format
is. But don’t forget to thank Dr. Takátsy for inventing a tool that makes our
life easy.
6. http://www.labmanager.com/?articles.view/articleNo/3551/article/Evolution-of-Microplate-Technology
* I couldn’t come up with 96
reasons, it’s like using only few wells in a 96-well plate!
