Methods in molecular biology and the understanding
of actions inside living cells have changed drastically
over the last decade. In comparison, methods
in cell culture have remained unchanged for
almost a century, when the first type of Petri dish
Recently, there have been major developments in
the optical analysis of processes inside living cells. Fluorescence methods, confocal microscopy, and
evanescent field methods have become indispensable
tools for cell imaging. Consequently, there is an
increased demand for systems that combine the
needs for cell cultivation with the requirements of
Figure 1 - μ-Slide I and a cell observed with different imaging modes in a
cell culture chip for live cell imaging.
The cell culture μ-Slide system (ibidi GmbH,
Munich, Germany) is well suited for the cultivation
and subsequent high-end optical analysis of cells. In
addition to fluorescence applications, the system
can be used with phase contrast or differential
interference contrast (DIC). The μ-Slide I and a
cell observed with different imaging modes are
shown in Figure 1.
μ-Slides contain channels and reservoirs to grow the
cells on the same substrate where, later, fixation,
staining, and imaging are carried out. Thus, there is
no need to transfer the cells to a coverslip.
The system is a flow-through device for the functional
analysis of living cells. Apart from some open
formats, most of the systems are perfusion chambers.
They allow easy exchange of fluids and are
useful for the cultivation of cells under defined
shear stress conditions.
The μ-Slide I was used to cultivate human umbilical
vein epithelial cells (HUVECs) under flow conditions.
The influence of different coatings and flow
rates on cell growth could be observed. A channel
fully covered with HUVECs was obtained by sequential
seeding steps, providing a model system for blood
vessels in general.
Figure 2 - a) Y-shaped μ-Slide with adopted flow system. b) Schematic drawing of an artificial blood vessel in the system.
Another approach utilizing the advantages of a perfusion
chamber is the investigation of plaque formation
inside an artificial blood vessel. The flow-through
device can be easily connected via its LUER
adaptors, and the system is ready to be used as a disposable
cell culture biochip to meet high optical
demands. The main research area here was to study
the influence of the velocity gradients at the bifurcation
of the vessel. These branching points are of special
interest in arteriosclerosis research because the
flow conditions change drastically. In an
ongoing project, the authors are studying
the influence of certain substrates to cell
adhesion. At ibidi the authors plan to do a
screening to identify which substances start
an inflammation process on an endothelial
layer at the bifurcation. Additionally, the
authors will simulate cell-cell interactions in
their blood vessel model systems. Figure 2a
shows a Y-shaped μ-Slide together with a
diagram to illustrate the flow inside such an
artificial blood vessel (Figure 2b).
Due to its ease of handling, the μ-Slide VI
flat is suitable for rapid parallel immuno-fluorescence assays, e.g., in surface immobilization,
binding, and imaging protocols. In
six parallel channels, cells can be seeded in
a volume of only 25 μL, while a microscopic
area of 100 mm2 per channel is generated.
The parallelization enables the easy comparison
of different cell lines, fixation, or staining methods
on a single slide.
In a 25-μL cell suspension, 10,000 cells per channel
can be observed. After cultivation, cells can be fixed
and stained. For fixation, all standard methods (i.e.,
methanol, acetone, and paraformaldehyde) can be
used. The plastic material is compatible with all
commonly used substances.
Figure 3 - Fluorescence image of cells taken in μ-Slide VI flow.
Figure 4 - Fluorescence image of cells taken in μ-Slide VI flow.
Only 25 μL of staining solution is required.
Subsequently, different staining protocols, concentrations
of staining solutions, or antibodies
can be applied to the same set of cells on one
slide. All washing procedures and optimization
steps can be performed right under the microscope.
The images shown in Figures 3 and 4 can
be achieved on a single μ-Slide in almost no time.
Due to the small volumes of staining solution
required, the costs of such an assay can be reduced
by a factor of 10–20.
In addition, the convenience of the μ-Slides is an
important advantage. Until now, cells had to be
seeded on glass coverslips in a six-well plate, and
washing and further treatment were tedious. With μ-Slides, there is no cracking of fragile coverslips,
spilling of fluids onto the microscope, contact with
organic solvents, or staining solutions. The entire
procedure is done in the protected surroundings of
the channel. Stringent washing steps are easy and highly reproducible. For each assay, there is a time
reduction of approx. 30 min.
Figure 5 - μ-Slide VI flow.
Another important application of μ-Slides is the
toxicological screening of chemicals such as potential
drug candidates and environmental toxins, and
for this, the μ-Slide I and μ-Slide VI flow are particularly
well suited. The perfusion chamber permits
the easy addition of candidate drugs to adherent
cells on the surface. Measurements can be taken
with the microscope with a ready-to-use flow kit
(see Figure 5). Alternatively, a time-lapse series can
be taken and pharmacological screening of substances
can be made in long-term studies using the
perfusion chambers. Consequently, cell-based
assays that require an optical readout can be easily
performed in a μ-Slide VI flow. For example, the
influence of differently concentrated cadmium
solutions on COS cells have been tested (results to
The major focus of ibidi’s research projects is chemotactical
assays. An ideal system for these assays is
Dictyostelium discoideum. This widespread model system
is known to migrate in a cyclic adenosine
monophosphate (cAMP) gradient. The channel
geometry of μ-Slide I is well suited for these types of
assays, in which the chemoatractant is added from one
side and the motion of the cells can be observed in a
time-lapse series directly under the microscope. (The
Dictyostelium discoideum mutant used here [DdLimE-GFP]
was a kind gift from Dr. Günther Gerisch, MPI
for Biochemistry, Martinsried, Germany.)
6 - Sequence from a time-lapse series analyzing the Dictyostelium discoideum velocity
in a cAMP gradient.
In one set of experiments, 40 μL of a 0.1 mM concentration
of cAMP was injected into the channel
using a simple pipetting procedure. Subsequently,
the motion of the Dictyostelium discoideum was monitored
over time (see Figure 6). Most of these social
amoebae move over one-third to one-half of the
observation window, which is 425 μm wide. Thus, a
cell velocity of 5–7 μm/min is observed here, which
corresponds to the values reported in the literature.
Lab on a Slide® technology (ibidi GmbH) allows
the handling and analysis of biological samples.
Therefore, cells, bacteria, and viruses can be investigated,
immobilized, and manipulated using high-resolution
microscopy. This includes confocal, atomic force microscopy (AFM), and FCS measurements.
Biocompatible surfaces enable the investigation
of drug uptake and drug pathways inside
Looking to the future, these disposable cell culture
chips will be of interest from a cell biological as well
as a biophysical point of view. They allow a deeper
look at protein interaction, drug uptake, and blood
vessel formation. In addition, a better understanding
of cell attachment to well-characterized surfaces
under defined shear stress will improve the development
of new products in the analytical, cosmetic,
and pharmaceutical industries.
Dr. Rädler is Head, Chemical Research & Functional Surfaces,
and Mr. Horn is Product Manager, Chemotactical Assays, ibidi
GmbH, Schellingstrasse 4, 80799 Munich, Germany; tel.: +49
89 2180 6418; fax: +49 89 2180 13539; e-mail:firstname.lastname@example.org.