Nucleic Acid Microarrays
The use of microarrays for gene expression profiling was first published in 1995. This technology allowed scientists to analyze thousands of mRNAs in a single experiment to determine whether expression is different in disease states. Unfortunately, mRNA levels within a cell are often poorly correlated with actual protein abundance. This can be due to many factors including degradation rate of mRNA versus proteins and post-transcriptional controls and modifications. Measuring the amount of protein directly would bypass any mRNA inconsistencies and give a true level of gene function, however traditional protein characterization methods were slow and cumbersome. These combined factors were the impetus behind the creation of protein chips.
Deficiency of Traditional Protein Characterization Methods
Before the advent of protein chips, protein measuring and characterization was done using two different methods: 2D gel electrophoresis coupled with mass spectrometry, and liquid chromatography. These methods can separate and visualize a large number of proteins per experiment, however they are time consuming when compared to protein chips. Their process is very low-throughput because of lack of automation. Reproducibility is also a factor because of the large amount of sample handling. A better, more standardized, higher-throughput method needed to be invented for protein measuring and characterization.
Protein Chip Precursors to Modern Day
Immunoassays, the precursor to protein chips available since the 1980s, exploit the interactions between antibodies and antigens in order to detect their concentrations in biological samples. Their creation, however, is tedious and expensive. As a response to this, researchers at Harvard University combined the technologies of immunoassays and DNA microarrays to develop the protein chip. In their landmark paper, published in 2000, “Printing Proteins as Microarrays for High-Throughput Function Determination,” Gavin MacBeath and Stuart Schreiber described how to create protein chips and demonstrated three types of applications that would benefit from this new technology. The strengths of their approach were the use of readily available materials (i.e. glass slides, polyacrylamide gel), the relative ease of implementation (robotic microarray printers), and compatibility with standard instrumentation.
Within the past five years, many companies, including Biacore, Invitrogen, and Sigma-Aldrich, have begun production of industrial level protein array systems that can be used for drug discovery and basic biological research. Commercial entities have made protein chip research a streamlined and standardized process on the same level as DNA microarrays compared to its inception in 2000.
Academic research plays a huge role in the development and improvement of these technologies. The collaboration of academic research with systems such as the Affymetrix GeneChip and the Human Genome Initiative has allowed for friendly competition, resulting in the advancement of technologies. With more develops come a better understanding and encourages even more research towards these fields.
Affymetrix is a company that has been manufactures microarrays, named GeneChip, since 1992. They have 13 locations across the world with headquarters located in the US (California), UK, Japan, and China.