Introduction: The purpose of this study is to find the differences in SELDI-MS-TOF between serum and ACD plasma samples, which could provide the guide for selecting either serum or plasma samples for our ongoing study to discover potential biomarkers from patients with or without stroke. Method: Eight serum and eight ACD plasma samples were collected at same time from eight stroke patients. ACD plasma was prepared by mixing the whole blood sample with 1:1 PBS, and then centrifuged at 1000G for 20 min at RT using density gradient tube. Serum was prepared by sitting the whole blood sample at RT for at least 30 min and centrifuged at 1000G for 10 min. The SELDI-MS-TOF was acquired with four biochips, CM10, Q10, H50 and IMAC under same experimental conditions with Ciphergen Proteinchip PBSIIc. The biochips were read with two laser intensity settings. The low laser intensity focused on lower Mw range of 2.5 to 100 kDa and high laser intensity focused on higher Mw of 10 to 200 kDa. The spectra generated from these four types of biochips were compared and analyzed statistically with Ciphergen DataExpress. Results: For Q10, H50 and CM10 biochips, there was no significant difference in the features of SELDI-MS-TOF. The average number of the major peaks (s/n 6, val. 6) in serum was about 15% more than that in plasma in low Mw range (low laser setting). However, serum showed more and intense peaks, especially in the low Mw range (Mw<10000) if IMAC biochip was used. On average, serum had 34% more peaks (s/n 6, val. 6) than that in plasma in low Mw range in two IMAC runs. For high Mw range (high laser setting), peak difference was not significant for all four chips. There were some unique proteins existed in serum (Figure 1) which may due to the loss during the ACD plasma preparation or generated during the clotting process. Proteins (Mw 5350, 5920, 7880, 9202 et al) were significantly higher in serum. Conclusion: The results from serum and ACD plasma (diluted with 1:1 PBS) showed that serum had more and intense peaks, especially in low Mw range with IMAC chip. So for SELDI-MS-TOF, serum could be a better choice if serum is available. More comprehensive study by comparing serum with four different plasmas is underway.

[Proc Amer Assoc Cancer Res, Volume 46, 2005]