Tuesday, December 1, 2009

Protein Microarrays


Protein Microarray
Arrayit’s Microarray Platform Empower Biomarker Discovery and Diagnostics


We are implementing our ex-situ microarray technology to accelerate protein-biomarker discovery for research and diagnostic applications. What I am seeing in the field is that protein microarrays are being used to measure protein expression in normal and diseased human cells and also to detect infectious pathogens. Our tools, kits and reagents are the driving force behind the deployment of high throughput multiplexed protein microarray assays.

In one example antibody-capture reverse-antigen microarrays are being used to profile protein-expression patterns. We specialize in glass surface chemistries for Protein Microarrays and our SuperEpoxy 2 surface chemistry is widely used in this area. However, we also have SuperNitro and SuperPVDF microarray slide substrates. Our membrane slide technology laminates a 150 µm-thick, hydrophobic nitrocellulose or PVDF surface on a standard glass slides. These slides are compatible with 1, 2, 8, 16 and 24 well microarray reaction tools that empower simultaneous and multiplexed sample processing (arrays of arrays if you can picture that). See photos here. In some cases the tools put 4 slides into the format of a 96 well plate which as been especially popular. Our microarray slides can accommodate the microarray printing of spotting of antibodies, antigens, or cell lysates with high binding capacity. They can be used in reverse-phase protein microarrays, where antigens or cell lysates are captured on the array and probed with labeled antibodies. These types of microarrays are helping researchers identify proteins preferentially expressed in disease states and analyze proteome representation in various cell types. These membrane surfaces work exceptionally well in colorimetric microarray detection using our SpotWare colorimetric microarray scanner.

Protein microarrays target have many applications and therefore can service many different research areas. We can expand the utility of standard ELISA-type immunoassays through miniaturization and multiplexing. That said, we are also offering advantageous products in the biomarker discovery market and which of course leads to new diagnostics applications. For biomarker discovery, our PlasmaScan Microarray contains a unique set of antibodies that are only expressed in human plasma. We are confident that this product represents the right approach for future diagnostic applications. Our ability to measure differentially expressed antibodies expressed in plasma as candidate biomarkers, will yield specific panels of biomarkers that will provide the specificity needed for future diagnostic and prognostic applications. This microarray is available as a service and as a product for an end user.

Mass Spectrometry versus Protein Microarray

You may be asking yourself, should I be using Mass Spectrometry or Protein Microarrays? Of course I’m going to answer microarrays!...but I can provide very good reasons for that. Many applications use plasma for therapeutic-target discovery as well as diagnostic and prognostic applications. These application areas have many important requirements.

· Quantitative measurements over a wide dynamic range,
· Sensitivity to measure low-abundance proteins
· High throughput and easy to use
· Cost effective
· Small samples sizes
· No cross reactivity between proteins on the microarray(s)

It is important to not that it is not necessary to have antibody pairs for protein microarray assays, since we can very accurately measure auto antibodies to address many clinical applications. For example, using IgG the human body made against a tumor or other foreign cell.

Shelf life

Put away your worries about protein microarray stability and shelf-life. We have shown that protein microarrays can be printed and stored dry at room temperature for 1 year or longer. In contrast, beads used in multiplexed assays stored in solution will aggregate and go bad in a short amount of time. Our protein printing buffer stabilizes the proteins on the microarray for long term storage and since each spot is in a distinct location, they cannot aggregate and go bad. Stored clean and dry our protein microarray are stable indefinately.

Microarray Manufacturing

Arrayit has been selling specialty microarray glass since 1999. Our glass slides substrates are provided with or without coatings to meet all types of ex-situ and in-situ microarray applications. We are seeing specific opportunities for protein microarraying market sectors: academic researchers, producers of commercial kits, and companies developing diagnostic assays. Proteins, such as antibodies, antigens and synthetic peptides are inherently quite stable and do not tend to denature, especially if they are in the correct buffer system such as our Protein Printing Buffer. For these proteins, traditional 2-Dimensional surfaces are best and our SuperEpoxy 2 surface chemistry is excellent. When choosing the right surface chemistry consider the type of proteins being printed, use Protein Printing Buffer to stabilize the protein etc…BUT DO NOT FORGET THE DETECTION METHOD!! All membranes have high background when using standard microarray fluorescent scanning. Not all surfaces are compatible with high levels of detergents and will get in the way of binding. It can be a bit complicated, email me if you’re having trouble working through this todd@arrayit.com The bottom line is that our Microarray Printing Technology can create a microarray of protein samples on epoxy-silane coated glass, gold-plated glass, membrane-coated glass, microfluidic substrates, plastics, hydrogels and membrane-coated plate wells. We have specific publication examples in all of these areas! So don’t worry, your application is going to be compatible with our spotting methods!! http:/www.arrayit.com