The effect of thin oxide film on protein sample measurement with TOF-SIMS

• Published in: Surface and interface analysis Vol. 43; no. 1-2; pp. 272 - 276
• Main Authors: Aoyagi, Satoka, Inoue, Masae, Mitsuoka, Takuya
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.01.2011; Wiley
• Subjects: Atomic, molecular, and ion beam impact and interactions with surfaces; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; Glass; Impact phenomena (including electron spectra and sputtering); Indium tin oxide; Lysozyme; Oxide coatings; Physics; Plates; protein evaluation; Proteins; Silicon substrates; Spectra; thin oxide film; TOF-SIMS; Atomic force microscopy; protein evaluation; Gallium; Inorganic compounds; Oxide layer; Transition element compounds; Glass; Time-of-flight method; Indium; Positive ions; Thin films; Thickness; Proteins; Silicon oxides; Preparation; Ion sources; thin oxide film; SIMS; Silicon; TOF-SIMS; indium-tin oxide
• ISSN: 0142-2421; 1096-9918; 1096-9918
• DOI: 10.1002/sia.3443

Recently, the biomaterial field has become one of the most important applications of time of flight (TOF) SIMS time‐of‐flight secondary ion mass specmetry (TOF‐SIMS). Although TOF‐SIMS can be applied to insulating samples, electrically conductive substrates such as Si, Au plates and indium‐tin oxide (ITO) glass plates are more useful to detect fragment ions from biomaterials. ITO glass and silicon substrates are often employed for the preparation of biomaterial samples instead of glass plates. In this study, an ITO glass plate and silicon plates with various thicknesses of silicon oxide thin film were compared to investigate the most suitable sample preparation conditions for evaluating protein samples using TOF‐SIMS. Four kinds of substrates, an ITO glass plate, a silicon plate, a silicon plate with an oxide film of 50 nm, and another of 250 nm, were employed as substrates to adsorb a model protein, egg white lysozyme. Each sample was measured five times with TOF‐SIMS with a gallium ion source under static conditions. The TOF‐SIMS spectra of each sample were compared to evaluate the effect of thin oxide films on protein measurement with TOF‐SIMS. The specific peaks of each sample related to lysozyme in the positive ion spectra were selected in comparison to their control samples. As a result, TOF‐SIMS spectra of the silicon plate with a 50 nm silicon oxide film showed the most specific peaks related to lysozyme. In addition, TOF‐SIMS spectra of the ITO sample showed many peaks of fragment ions related to lysozyme in a high‐mass range at which the other samples do not show adequate peaks. Thus, both substrates with the oxide films, silicon oxide and ITO, displayed better results than the silicon plate sample. Copyright © 2010 John Wiley & Sons, Ltd.