Preparation of PEI-coated slides

Clean slides in a ultrasonic bath with 1% SDS and 4% hydrofluoric acid (HF). 

Immerse in APS, 0.05% w/v in 95% ethanol rinse several times with 95% ethanol oven dry at 110°C. 

Immerse amine slides in a stirred slurry of cyanuric chloride (12.7 g/L) and sodium carbonate (25g/L) in hexane at 4°C for 1 hr with sonication rinse with hexane air dry. 

Immerse slides in 0.1% aqueous polyethylenimine (25,000 average mol. wt.) at 4°C for 1 hr with sonication. 

Both proteins and nucleic acids may be immobilized to a variety of solid supports. For high density microarrays, glass slides are the preferred substrates because of their flatness and optical properties. Better spot resolution is also possible on nonporous glass as opposed to porous membranes, primarily due to a reduction in diffusion at the surface-liquid interface. However, keep in mind that spot (droplet) diffusion can occur on most substrates by the actions of surfactants and other wetting agents including proteins. Control of spot size and morphology is required in order to achieve reproducible and reliable results with microarrays. 

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