A recent article (1) reporting on a conference in Edinburgh, Scotland, discusses the progress in ‘affinity proteomics’, that is, antibody-based assays including protein microarrays and their potential for use in clinical diagnostics. There continues to be much optimism around the use of antibody-based microarrays for diagnostics, and yetthe emergence of this technology has been slower than expected. While antibody-based microarrays have been used extensively in research programs and biomarker discovery, only one company has attained US-FDA approval for a clinical diagnostic with protein microarrays: SQI Diagnostics(“SQD”). Curious about the barriers for protein microarrays’ entry into clinical diagnostics, I recently spoke with Gabriel Armstrong, Director for Customer Solutions at SQI, about navigating the approval process for the first protein microarray.Gabriel talked about the design paradigm that SQI needed to develop to address the diagnostics market with protein microarrays.
“Historically, protein microarrays were developed for the high throughput proteomics research market, which demanded low cost, flexible systems and sacrificed sensitivity and data quality as a result,” says Gabriel. One of the first lessons SQI faced was that there was no precedent for a multi
–plex protein assay in diagnostic, and that DNA analysis platforms based on beads were not optimal for use with proteins and antibodies. According to Gabriel, SQI “ realized we needed to build standards and controls into our multi –plex platform so that the performance standard matched that of single-plex assays based on ELISAs”. Thus the arrays used in SQI assays include many novel algorithms and other innovations such as normalization curves, positive and negative controls for each protein. SQI reports that their new Diagnostic Tools and Services business is leveraging their experience to help other companies with biomarker content convert to multiplex arrays, both for clinical and research applications. Currently SQI has approved diagnostic assays for autoimmune diseases that monitor up to 4 proteins/assay. Their pipeline includes assays that will multiplex up to 10-13 proteins in a single assay. This is equivalent to 10-13 ELISA plates (96-well format), and in a clinical lab, each plate is typically processed at a different station. This scenario brings the concept of miniaturization with microarrays into focus, where a single plate can process up to 80 patients’ samples for 4 assays at once, conserving space and sample for the modern diagnostics clinic.
- Genetic engineering & Biotechnology News, 32(9), “Advancing Beyond the Genome with Affinity Proteomics”