title: Layer-by-layer self-assembled mutilayer films of gold nanoparticles for surface-assisted laser desorption/ionization mass spectrometry.
abstract: 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.
authors.affiliation: Department of Applied Chemistry, Kansai University, Suita, Osaka 564-8680, Japan.
authors.forename: Hideya
authors.initials: H
authors.lastname: Kawasaki
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Sugitani
authors.forename: Takehiro
authors.initials: T
authors.lastname: Watanabe
authors.forename: Tetsu
authors.initials: T
authors.lastname: Yonezawa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Moriwaki
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Arakawa
mesh_terms: D000803:Angiotensin I / Q000032:analysis / Q000737:chemistry; D019343:Citric Acid / Q000737:chemistry; D045304:Cytochromes c / Q000032:analysis / Q000737:chemistry; D006046:Gold / Q000737:chemistry*; D006801:Humans; D007328:Insulin / Q000032:analysis / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry*; D018625:Microscopy, Atomic Force / Q000379:methods; D010446:Peptide Fragments / Q000032:analysis / Q000737:chemistry; D011073:Polyamines / Q000737:chemistry; D011506:Proteins / Q000032:analysis* / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013056:Spectrophotometry, Ultraviolet / Q000379:methods
chemical_list: D007328:Insulin; D010446:Peptide Fragments; D011073:Polyamines; D011506:Proteins; D000644:Quaternary Ammonium Compounds; D019343:Citric Acid; C063994:polyallylamine; D006046:Gold; C481046:ammonium citrate; D045304:Cytochromes c; D000803:Angiotensin I