Minimizing Carry-Over Contamination
Due to the composition and differing viscosity of various spotting solutions used for protein arrays, minimizing the amount of carry-over between spots is a critical step for successful protein arraying. The OmniGrid and MicroGrid microarraying systems allow for control over the wash steps and cycles.
In order to establish a wash protocol that did not have carry-over, each dip into the dye sample was spotted six times onto the slides followed by the wash cycle, dipped into 1X PBS without dye and printed for an additional six spots. This was repeated three times. By varying the number of cycles through the sonication, wash, and dry cycles it is possible to develop a wash protocol that does not have any carry-over between samples (Figure 2).
The OmniGrid system has an on-board sonication and recirculating washing system to increase the effectiveness of the wash cycles. The MicroGrid system has two recirculating wash baths and uses the flood-and-flush method of cleaning the pins. Additionally, the two recirculating wash baths on the MicroGrid can be used as stationary baths, which can be filled with various cleaning agents such as ethanol.
Due to variations in printing solutions and concentration of proteins, sample-specific wash protocols will need to be determined empirically. By varying the times and number of cycles through the wash stations, it is possible to print proteins on nitrocellulose without any visible carry-over (Figure 2).