Kawasaki Hideya, Sugitani Tsuyoshi, Watanabe Takehiro, Yonezawa Tetsu, Moriwaki Hiroshi, Arakawa Ryuichi
Department of Applied Chemistry, Kansai University, Suita, Osaka 564-8680, Japan.
Anal Chem. 2008 Oct 1;80(19):7524-33. doi: 10.1021/ac800789t. Epub 2008 Sep 6.
Layer-by-layer (LBL) self-assembled multilayer films of gold nanoparticles (AuNPs) on a silicon wafer were demonstrated to be promising substrates for surface-assisted laser desorption/ionization (SALDI) mass spectrometry (MS) of peptides and environmental pollutants for the first time. LBL multilayer films, (AuNPs/PAHC)n, consisting of alternating layers of ammonium citrate capped AuNPs and poly(allylamine hydrochloride) (PAHC) were prepared on a silicon surface. Silicon plates with aggregated AuNPs were more suitable than those with dispersed AuNPs for the SALDI-MS of peptides. The number of particle layers had a significant effect on the laser desorption/ionization of angiotensin I; the peak intensity of the peptide (molecular ion amount) increased with an increase in the number of layers of AuNPs. As a result, the (AuNPs/PAHC)5 multilayer films increased the sensitivity of the angiotensin I to subfemtomoles and raised the useful analyte mass range, thus making it possible to detect small proteins (a 12 kDa cytochrome c). The signal enhancement when using (AuNPs/PAHC)5 may be due to (i) the high absorption of the UV laser light at 337 nm by the AuNP layers, (ii) the low thermal conductivity due to the AuNPs being covered with a thin monolayer of PAHC, and (iii) the increase in the surface roughness (approximately 100 nm) with the number of AuNP layers. Thus, laser-induced rapid high heating of AuNPs for effective desorption/ionization of peptides is possible. In addition, it was found that (AuNPs/PAHC)5 could be used to extract environmental pollutants (pyrene and dimethyldistearylammonium chloride) from very dilute aqueous solutions with concentrations less than 10(-10) mg/mL, and the analytes trapped in the LBL film could be identified by introducing the film directly into the SALDI mass spectrometer without needing to elute the analytes out of the film.
首次证明，在硅片上通过逐层（LBL）自组装形成的金纳米颗粒（AuNPs）多层膜是用于肽和环境污染物的表面辅助激光解吸/电离（SALDI）质谱分析（MS）的有前景的基质。在硅表面制备了由柠檬酸铵包覆的AuNPs和聚（烯丙胺盐酸盐）（PAHC）交替层组成的LBL多层膜（AuNPs/PAHC）n。对于肽的SALDI-MS，具有聚集AuNPs的硅板比具有分散AuNPs的硅板更合适。颗粒层数对血管紧张素I的激光解吸/电离有显著影响；肽的峰强度（分子离子量）随着AuNPs层数的增加而增加。结果，（AuNPs/PAHC）5多层膜将血管紧张素I的灵敏度提高到亚飞摩尔水平，并扩大了有用分析物的质量范围，从而能够检测小蛋白质（12 kDa的细胞色素c）。使用（AuNPs/PAHC）5时的信号增强可能归因于：（i）AuNP层对337 nm紫外激光的高吸收；（ii）由于AuNPs被PAHC的单层薄覆盖而导致的低导热率；（iii）表面粗糙度随AuNP层数增加（约100 nm）。因此，有可能通过激光诱导AuNPs快速高效加热来实现肽的有效解吸/电离。此外，发现（AuNPs/PAHC）5可用于从浓度低于10（-10）mg/mL的极稀水溶液中提取环境污染物（芘和二甲基二硬脂基氯化铵），并且无需将分析物从膜中洗脱出来，直接将膜引入SALDI质谱仪即可鉴定捕获在LBL膜中的分析物。
