Nanomedicine - Bionanoelectronics: Bioinquiring and Bioinspired Devices - page 145

Fig. 4.24 DNA biochip

FUNCTIONALIZATION =
immobilization of DNA sequences
(probes) on prescribed positions

HYBRIDIZATION = analytes
are contacting probes

READOUT

DNA biochip

readout is based on chemiluminescence, in which the background signal and photo
bleaching are absent, in contrast to the fluorescence method. Tens of thousands of
DNA probes can be analyzed simultaneously in this way.
Another chip, the protein chip (microarray), is targeting the most advanced topics
of genomics, i.e., the analysis of genome at protein level. The main procedures
of this biochip are similar to the DNA chip, but the protein chip is by far more
complicated than the DNA chip. The reason is that there is a large variety of proteins,
such as antigen-antibody, antibody-antigen-antibody, protein-protein, receptor-
protein, etc., and so the functionalization methods and the hybridization processes
are more complicated and more elaborate. Moreover, in the case of proteins, the
polymerase chain reaction (PCR) amplification mechanism for DNA multiplication
is missing. There are specific linkers for protein immobilization. The readout is
more difficult than in the case of DNA chips. The readout techniques are enzyme-
linked immunosorbent assays (ELISA), which are not specific at various protein
interactions, and thus, many false results can be obtained. Fluorophore labeling
has poor reproducibility, and therefore, the readout techniques for protein chips are
oriented to label-free detection methods, such as those based on plasmonics and
described in Chap. 2 of this topic.
There are also lab-on-chips associated to microfluidics, which were explained
briefly in Chap. 1 . A good review about lab-on-chip applications is ( Haeberle and
Zengerle 2007 ). The concept of lab-on-chip can be extended to other types of
biochips. For example, a plant-in-chip is a microfluidic platform for the hydroponic
growth of the Arabidopsis plant ( Parashar and Pandey 2011 ). The microfluidic plat-
form consists of several microchannels, in which 1-day-old germinated seedlings are