Biomedical Engineering Reference
In-Depth Information
Fig. 3.7
Results for Luminex xMap bead. The results for the CON1 calibration beads (identifier
channel) illustrate the ability to distinguish between different bead types, and the results for CON2
show the ability to detect low analyte concentrations (reporter channel)
channel. This measurement illustrates that we can clearly distinguish the different
bead types and that we have a sufficient sensitivity in the reporter channel to measure
low analyte concentrations.
3.5
Multicolor Detection with Single Large-Area Detector
The particular strength of our technique is to enable sensitive, rugged, and low-
cost instruments for PoC applications. The critical alignment within the system is
substituted by the alignment of the shadow mask relative to the channel thereby
providing a rugged system. To prove multicolor detection can be achieved without
costly dielectric filter sets and multiple detectors, we demonstrated an elegant and
effective solution for two-color detection using a single larger-area detector. Replac-
ing the patterned shadow mask with a patterned color mask (see Fig.
3.8
a) allows
recording multiple fluorescence channels with a single large-area detector. Different
fluorescence emission characteristics of different fluorophores are transmitted at
different positions of the mask. Therefore, different fluorophores create a different
fluorescence intensity-time profile when they traverse the detection area. Informa-
tion of the particle's emission spectrum is encoded in the time-dependent signal.
In our measurements, we used a 532-nm excitation laser, a pin photodiode,
and a red/green-patterned color mask to distinguish between PE and PECy5
Spherotech beads. PE-fluorescence emission is transmitted by the green parts of
the transmission mask shown in Fig.
3.8
a, while PECy5-fluorescence emission is
transmitted by the complementary red parts of the mask. As shown in Fig.
3.8
b,
the fluorescence signal from PE and PECy5 Spherotech beads which have the same
excitation spectra but different emission spectra shows a (almost) complementary
