47Biochip Technologies
Numerous biochip technologies are available for clinical applications. Some
examples that are relevant to personalized medicine are described briefl y in the
following text.
PCR on a Chip
PCR is now offered on a chip. One example is VereChip™, a silicon chip that inte-
grates an ultra-fast miniaturized PCR reactor for amplifi cation of nucleic acids and
a customizable microarray. It allows users to apply the full benefi ts of molecular
testing in real-world conditions, at a fraction of the time, cost and complexity
needed to operate common lab equipment. A compact optical reader captures and
analyzes the microarray in a few seconds. The optimal optics settings are automati-
cally selected and this makes it particularly suitable for minimally-trained personnel
and point-of-care (POC) applications. The software can provide a highly detailed
microarray analysis report for expert users in a central lab or a simple diagnostic
report for basic users in a POC setting. An example of application is VereFlu™ for
diagnosis of human and swine infl uenza.
A fast PCR biochip technology system can identify infectious disease strains in
<15 min when using protein arrays and in <2 h when using nucleic acid arrays. The
system can be used in hospitals and other laboratories as well as in the fi eld. Each
biochip has hundreds to thousands of gel drops, each ~100 μm in diameter. A seg-
ment of a DNA strand, protein, peptide or antibody is inserted into each drop, tailor-
ing it to recognize a specifi c biological agent or biochemical signature. These drops
are in known positions so when a sample reacts, the reaction position can be
detected, identifying the sample. A sample to be tested is applied to a biochip,
which is then put in a reader and scanned using patented side illumination laser
technology to detect reaction sites. Automated algorithms determine the agents
present in the sample. Techniques are being refi ned to shorten sample preparation
time to ~10 min and increase system sensitivity, enabling full analysis to be done in
<1 h for nucleic acid arrays.
Methods for the simultaneous analysis of multiple genes are needed and micro-
arrays are an ideal platform for such analysis because their miniature size enables
one to arrange up to hundreds or thousands of biological probes in a relatively small
space with minute sample volume. However, the overall sensitivity of microarray
detection technology is relatively low. Use of PCR as a powerful tool for multi-
target analysis has two limitations: (1) identifying solution-phase multiplex PCR
amplicons typically requires a secondary method for size separation or sequence
verifi cation prior to analysis and data interpretation; and (2) multiplex PCR is
restricted in the number of targets that can be reliably amplifi ed simultaneously,
because of uncontrollable primer–primer interactions.
Biochips and Microarrays