Patterned and switchable surfaces for biomaterial applications

Andrew Hook – Patterned and switchable surfaces for biomaterial applications1.2.5. Robotic contact and non-contact microprintingFormation of micron resolution arrays is routinely achieved by robotic contact andnon-contact microprinting. Robotic contact printing is achieved using a roboticspotter that first dips a pin with microscale diameter into a desired solution then spotsthe sample onto the substrate surface at a specified location. Two types of pins aretypically used. First, a solid pin, which is commonly used for transferring proteinsand other sticky molecules because of their ease of cleaning and second, a quilled pinthat has a hollow centre that is able to draw up the solution and act as a reservoirallowing repeated spotting without re-dipping. Although, this increases the rate ofmicroarray formation, these pins are much more difficult to keep clean and are,therefore, only suitable for ‘non-sticky’ molecules. Robotic non-contact printing isachieved by ejecting nano-litre volumes of the desired solution from a microcapillaryonto specified positions on a surface. The advantage of this strategy is that commonproblems with pins, such as the risk of contamination if the pins are insufficientlycleaned, inhomogeneous spot geometry and variations in the dispensed volume, canbe avoided [94], however, this approach typically suffers from ‘splattering’ ofejected volumes. Such strategies can be used to form DNA and protein microarraysand more recently also cell microarrays [8, 15, 82, 94-99].This form of patterning is very effective at quickly and reproducibly producingmicron resolution patterns that can be used for the cost effective, high-throughputanalysis of proteins and DNA products using very little reagents on, typically, asingle microscope slide. Microarrays were key to the success of the human genomeproject and will underpin further genomic analysis. The development of cellmicroarrays will further advance genomic analysis, and as the investigation of more1-29