The rapid progression of microarray technology was the focus of two recent conferences—Select Biosciences “Advances in Microarray Technology” held in Barcelona and the “World Microarray Congress” held in Vancouver. Both events emphasized the exploration of gene expression through microarray technology by advanced means that can provide enhanced results faster and more efficiently.
At the Barcelona meeting, Iain McWilliam, Ph.D., senior scientist at Arrayjet, described advances in microarray production using inkjet technology, which he characterized as having come of age. Once the preserve of specialist facilities, inkjet printing is now used by 20 Arrayjet customers globally in both research labs and microarray production facilities.
The technology uses noncontact printing within a flexible platform to produce diverse microarrays at high speed. The Arrayjet systems, Dr. McWilliam noted, are low maintenance and are used in both R&D and production settings. He listed nucleic acids, peptides, intact cells, and proteins—including “obnoxious proteins such as blood serum and cell lysates”—among the arrays that can be produced. Common substrates include coated glass slides, NC slides, SPR prisms, unbound NC membrane, and silicon wafers.
In another example, which concerned the application of microarray technology to hybridoma production for monoclonal antibodies, Dr. McWilliam described how protein microarrays improved throughput per technician 10-fold (from 20 to 200 targets per technician per year) by reducing processing time from four to seven months to just seven weeks. This method was developed by Federico De Masi, Ph.D., of Alan Sawyer’s group at the EMBL Monoclonal Antibody Core Facility in Italy.
Arrayjet microarrayers place spots in a precise and repeatable manner and, in the case of the Ultra-Marathon system, at a rate of one 384-well plate onto 1,000 slides in less than 90 minutes, reported Dr. McWilliams. The key to the system is the JetSpyder™, a nanoscale liquid-handling unit that enables aspiration of 12 or 32 samples simultaneously, he added.
A XaarJet inkjet print head (Xaar) mates to the JetSpyder via vacuum, and probes are aspirated from source plates (up to 48 x 96 or 384 wells). The JetSpyder is then undocked leaving the print head, containing 12 or 32 probes, primed and ready to print. Probes are delivered via noncontact, on-the-fly printing onto the substrate to the user’s specification. The accuracy of printing is such that in subsequent print runs probes can be overlaid onto the same spot locations to create multilayered assays. Additionally, the system aspirates each probe into multiple nozzles within the print head, enabling flexible dispensing from 100 pL to 600 pL per spot, according to the company.
Furthermore, no changes to the system are required when switching between sample types or when changing print layouts. The recently released Array Multiplier™ software enables the user to divide each slide or substrate into a number of areas, each of which can be independently addressed by the microarrayer during the production step, producing slides with multiple mini-arrays printed on them and thereby greatly increasing sample throughput, Dr. McWilliams said.
The system is automatically cleaned between aspirations during printing, as well as at the beginning and end of each print run: the print head and JetSpyder capillaries are stringently washed with buffer—both independently and when docked together—to eliminate carryover contamination, even when arraying sticky protein solutions or cell lysates.