55specifi c autoantibodies, using arrays of large numbers of recombinant proteins of
known identity. Such arrays overcome the problems associated with variation of
protein levels in conventional tissue extracts and hence improve reproducibility as
a prerequisite for diagnostic use. High-throughput protein arrays have the potential
to become diagnostic tools, eventually arriving at the doctor’s offi ce and as over-
the- counter devices. However, techniques to enable effi cient and highly parallel
identifi cation, measurement and analysis of proteins remain a bottleneck. A plat-
form technology that makes collection and analysis of proteomic data as accessi-
ble as genomic data has yet to be developed. Sensitive and highly parallel
technologies analogous to the nucleic acid biochip, for example, do not exist for
protein analysis.
New Developments in Protein Chips/Microarrays
The new and versatile protein array technology allows high-throughput screening
for gene expression and molecular interactions. Protein arrays appear as new and
versatile tools in functional genomics, enabling the translation of gene expression
patterns of normal and diseased tissues into protein product catalogues. Protein
function, such as enzyme activity, antibody specifi city or other ligand–receptor
interactions and binding of nucleic acids or small molecules can be analyzed on a
whole-genome level. As the array technology develops, an ever-increasing variety
of formats become available (e.g. nanoplates, patterned arrays, three-dimensional
pads, fl at-surface spot arrays or microfl uidic chips), and proteins can be arrayed
onto different surfaces (e.g. membrane fi lters, polystyrene fi lm, glass, silane or
gold). Various techniques are being developed for producing arrays, and robot-
controlled, pin-based or inkjet printing heads are the preferred tools for manufactur-
ing protein arrays. CCD cameras or laser scanners are used for signal detection;
atomic force microscopy and mass spectrometry are upcoming options. The emerg-
ing future array systems will be used for high-throughput functional annotation of
gene products, their involvements in molecular pathways, and their response to
medical treatment and become the physician’s indispensable diagnostics tools.
Protein Biochips/Microarrays for Personalized Medicine
Protein biochips/microarrays are well-established tools for research and some prod-
ucts for in vitro diagnostics are available commercially. Profi ling proteins on bio-
chips will be useful for distinguishing the proteins of normal cells from early-stage
cancer cells, and from malignant metastatic cancer cells. In comparison with the
DNA microarrays, the protein microarrays/chips, offer the possibility of developing
a rapid global analysis of the entire proteome leading to protein-based diagnostics
and therapeutics. Of all the applications of protein microarrays, molecular diagnos-
tics is most clinically relevant and would fi t in with the coming trend in individual-
ized treatment. These technologies have an advantage in diagnosis of some conditions.
Biochips and Microarrays