Strategies for Miniaturized Biomarker Detection

Abstract: The aim of this thesis is development and application of different miniaturized strategies for detection of biomarkers. The biomarker PSA (prostate specific antigen), which is prostate cancer specific, has been the main focus of the thesis. The papers present two miniaturized strategies for biomarker detection, developed at the department, an antibody microarray and the ISET platform. The antibody microarray, based on a micro- and nanoporous silicon surface, which increases the sensitivity of the assay, was utilized to quantitatively measure the prostate cancer biomarker PSA. The microarray was also developed to measure the two forms of PSA: total PSA and free PSA, which together gives a better indication of the prostate cancer disease. The second platform for proteomic analysis, the in-house developed platform ISET, which is a sample preparation platform for MALDI mass spectrometry, was first redesigned to be able to handle more viscous samples and larger volumes. Subsequent to the new configuration of the ISET platform, three new applications were developed and published within the framework of this thesis; digestion and detection of the biomarker PSA, protein validation of recombinant protein production, and aptamers as affinity ligand rather than antibody to reduce the background from the affinity probe when performing digestion of the captured protein. The ISET sample preparation was also automated using liquid handling robotics for faster analysis in for example screening procedures. In addition to the microarray, the porous silicon surface was utilized to capture PSA and analyse through the use of reporter mass tags ionized in the mass spectrometry.