Biomedical Engineering Reference
In-Depth Information
Static
incubation
Start media
perfusion
FIGURE 5.35
Seeding.cells.in.microchannels..(From.L..Kim,.Y.-C..Toh,.J..Voldman,.and.H..Yu,.“A.
practical.guide.to.microluidic.perfusion.culture.of.adherent.mammalian.cells,”.
Lab Chip
.7,.681,.
2007..Reproduced.by.permission.of.The.Royal.Society.of.Chemistry.)
5.4.4 From Serial Pipetting to Highly Parallel Micromixers, Pumps, and Valves
Fluid handling—ranging from reagent mixing to medium changes and supernatant sampling—
is a major throughput-limiting step in cell culture technology. It currently involves interrupting
incubation and subsequently pipetting the luid in or out of the cell culture medium, which
requires time-consuming manual labor or very costly automated multipipetters equipped with
complex tubing and valve systems—both processes being prone to contamination and spills.
he advent of multiwell plates represents an attempt to mitigate these limitations, but it is expen-
sive to scale up because the required number of plates and luid delivery steps grows geometri-
cally as the number of cell culture parameters increases.
Let us consider two examples (note to young investigators: either of these would make for
great microluidics projects):
he optimization of a deined cell culture medium (for a particular cell type, a par-
ticular application, and even a particular phenotype), which may involve studying
the nonlinear, nonadditive efects of various hormones, growth factors, amino acids,
glucose, salts, and so on at diferent concentrations, as critical as it can be for the suc-
cess of an experiment, can become a monumental task in its own that only a few cell
culture laboratories can aford to undertake. As cell culture studies become increas-
ingly sophisticated, the development of fast, inexpensive mixers that generate a com-
binatorial range of luid mixtures becomes imperative.
Most cell culture protocols are presently based on changing the cell culture medium
every 24 hours (or 48 hours). Biologists have not adopted this schedule based on irst
principles (i.e., this is what the cells need); they have adopted it because it is convenient
for humans, who need to rest between experiments. If the schedule were being carried
by a microluidic automaton (i.e., by microvalves and micropumps), one might ind
