Microarray partition using a recycled marker pen and neutral balsam

Microarrays are very powerful tools for both basic research and clinical studies [1 ]. There are a variety of types of micro arrays, e.g. DNA microarrays, protein microarrays, carbohy drate arrays, tissue microarrays [2] etc. They have been widely applied for numerous applications from gene expres sion monitoring [3], single nucleotide polymorphism analysis [4] to protein protein interaction profiling [5], protein small molecule interaction analysis [6], etc. The most wellrecognized micmarrays usually carry thou sands to millions of probes on a single array. To save cost, time, and labor, it is a good practice to create subarrays on a single standard substrate slide in a layout compatible with the standard multichannel pipette, thus facilitating high throughput operation. As to effectively analyze multiple samples on a targeted microarray, tile subamlys must be physically partitioned to prevent crosscontamination. To effectively partition subarrays on a single slide, several types of incubation frames have been developed, e.g. FrameSealTM incubation chamber （BioRad, Hercules, USA）, SmartGridTM （CapitalBio Corporation, Beijing, China）, and Whatman： FAST slide incubation chambers （GE Healthcare, Bethesda, USA）. Usually, these frames are adhesive on one side. They could be fastened and stuck to the microarray and could be easily removed after incubation. However, these chambers are and layout of the chamber is not reusable and tile number fixed. If the chamber is not properly handled, leaking will occur and thus cause cross contamination. To increase the reusability of the chamber, nonadhesive chamber coupled with a clipping toolkit is also available, e.g. the ArraySlide chamber and ArraySlide gasket （Gel Company, San Francisco, USA）. Another avail able partition method is to imprint prepatterned wax using a mold by a device named Slidelmprinter （Gel Company）. However, this device and the accessories are expensive. Here, we described a simple method for hydrophobic par tition of flexible number of subarrays on a single microarray using a recycled marker pen and hydrophobic neutral balsam as ink. A recycled marker pen was cleaned by ethanol toremoTe all the colorful ink until the tip turned white and then airdried. Neutral balsam was chosen as ink because it could form rigid and waterrepellent barrier on glass slide when dried as shown in immunohistochemistry experiments. The neutral balsam solution was freshly prepared before partitioning by mix neutral balsa