ChemoMetec SP-100 - Manual (Page 21)

1 Basics of the SP-100 system
3
1.1.2 SP1-Cassette
The SP1-Cassette is a small custom made disposable plastic device designed for optimal
sample handling and safe disposal. The cassette is shown in
Figure 5 . The main features
of the cassette are the piston, the flow system containing the fluorescent dye (PI), and
the measurement chamber with the measurement window.
The SP1-Cassette is loaded by gently pressing the piston rod, thereby creating a partial
vacuum through the flow system. Approximately 60 µl of the lyzate mixture is loaded
into the cassette.
The PI is immobilized in the first three lanes of the flow system. As the lyzate mixture is
loaded into the SP1-Cassette and transported through the flow system towards the
measurement chamber (the clear window), the immobilized PI is dissolved and mixed
with the lyzate mixture. PI intercalates with DNA and stains the nuclei of the cells. Due
to the fluorescent nature of PI it absorbs green light and then emits red fluorescence
light, which is used for detection of the stained nuclei. The actual cell count is
performed in the measurement chamber of the SP1-Cassette, using the NucleoCounter
SP-100 with its integrated fluorescence microscope and automatic image analysis (refer
to Section 1.1.3).
The total volume of the measurement chamber is approximately 3 µl. As mentioned in
Section 1.1.1, the analysis volume is approximately 1 µl, i.e. one third of the total
measurement chamber volume is analyzed.
In connection with the production of the SP1-Cassettes each cassette is marked with a
black dot code, which specify the precise depth of the measurement chamber of the
cassette. The dot code is read and decoded in the instrument during analysis and the
volume is obtained by multiplying the area to be analysed with the depth of the
cassette. The area analysed is only dependent on the optics of the instrument.
Therefore, the area is constant and specific for each instrument.
Caution! In order to avoid contaminating the measurement window it is important not
to touch the window when handling the cassettes.