Biomedical Engineering Reference
In-Depth Information
biocomponent (or biomimetic component) biosensors are principally capable of
working in crude samples without prior purification, like the measurements
made by glucose sensor measures in undiluted blood samples. However, many
biochemical assays, especially those related to the determination of nucleic acids
need sample preparation. Also the introduction of labels for improvement of
sensitivity requires preanalytical sample treatment. For this reason, further inte-
gration steps have to be performed to fulfill the needs of more complex analyses.
2.2 Lab-on-Chip Systems
While in biosensors and biochips data generation and amplification are included,
preceding steps such as sample preparation, purification and washing steps for
performing assays are not. For point-of-care testing, nevertheless, these steps
should be included, for example when cells have to be destroyed to analyze
interior compounds. Especially for the analysis of nucleic acids, usually lyses and
amplification (with polymerase chain reaction, PCR) are necessary steps before
determination of origin or more specific sequence details. Since user-friendliness
was defined as being one of the key challenges all these steps have to be automated
and integrated into the analytical device.
One concept to do so is a Lab-on-Chip system; the term derived from the notion
of a ''laboratory on a (microelectronic) chip'' program. All the above-mentioned
preanalytical steps have to be performed within the Lab-on-Chip device at labo-
ratory quality and it has to be designed in such a way that an unprocessed sample is
applied and finally measured by the biosensor which is part of the Lab-on-Chip.
Work on Lab-on-Chip systems in general has been reported for many years.
However, most approaches lack the possibility of serial production which hinders
the development that finally might lead to commercialization. Also, in many
studies just single steps of the analytical process were displayed and designed in a
chip-like format but the whole process has not been covered yet.
Recently, the current authors published work on a Lab-on-Chip system called
the ''Fraunhofer ivD-platform'' that was designed with the potential for serial
production and offers a huge degree of modularity [
21
]. The system which will be
described in greater detail in a later chapter of this topic consists of a credit-card-
sized cartridge (used as a consumable) and a read-out unit. Considering the con-
cept of integration within the cartridge, which is the actual Lab-on-Chip system,
all steps from sampling to transduction are integrated. Processes such as data
amplification and displaying of the results are integrated into the read-out and
processing unit. In this way, the combination of the cartridge and the read-out unit
cover the whole process chain necessary for point-of-care testing.
To perform a test, blood from the finger pad is used and applied onto the
cartridge. Besides a reservoir for the sample, the cartridge holds the reagents
necessary for the particular test (assay), the sensor and actuators for displacing
reagents and sample towards the sensor. Hence, after adding a drop of blood the
