DNA-modified ITO surfaces for affinity MALDI-MS

Abstract

Indium Tin Oxide (ITO) coated surfaces were compared with fused silica and aluminium probes for conventional MALDI-MS of proteins, followed by experiments to determine if the advantages of ITO over the poorly conducting fused silica surface would carryover to affinity MALDI-MS, in which the probe surface is modified with DNA for protein capture and detection. Improved precision of m/z values and increased detectability by 1 to 2 orders of magnitude were observed for capture and detection of insulin and insulin-like growth factor 2 at surfaces modified with sequences from the insulin-linked polymorphic region (ILPR) of the human insulin gene that have previously been shown to bind with high affinity to these proteins. Results also indicate capture and detection of the insulin β-chain from DTT-treated human serum at the DNA-modified ITO surfaces. The improved performance is accompanied by the same ease of covalent DNA attachment and indefinite reusability of the DNA-modified surfaces previously demonstrated for fused silica probes. The use of ITO-coated surfaces is an important advance toward the routine use of DNA-modified surfaces in affinity MALDI-MS for rapid screening of DNA–protein interactions for applications such as biomarker discovery and detection of low abundance proteins in complex biological samples.