title: Cavitands Endow All-Dielectric Beads With Selectivity for Plasmon-Free Enhanced Raman Detection of Nε-Methylated Lysine.
abstract: SiO2/TiO2 microbeads (T-rex) are promising materials for plasmon-free surface-enhanced Raman scattering (SERS), offering several key advantages in biodiagnostics. In this paper we report the combination of T-rex beads with tetraphosphonate cavitands (Tiiii), which imparts selectivity toward Nε-methylated lysine. SERS experiments demonstrated the efficiency and selectivity of the T-rex-Tiiii assays in detecting methylated lysine hydrochloride (Nε-Me-Lys-Fmoc) from aqueous solutions, even in the presence of the parent Lys-Fmoc hydrochloride as interferent. The negative results obtained in control experiments using TSiiii ruled out any other form of surface recognition or preferential physisorption. MALDI-TOF analyses on the beads exposed to Nε-Me-Lys-Fmoc revealed the presence of the Tiiii•Nε-Me-Lys-Fmoc complex. Raman analyses based on the intensity ratio of Nε-Me-Lys-Fmoc and cavitand-specific modes resulted in a dose-response plot, which allowed for estimating the concentration of Nε-methylated lysine from initial solutions in the 1 × 10(-3) to 1 × 10(-5) M range. These results can set the basis for the development of new Raman assays for epigenetic diagnostics.
authors.affiliation: INSTM and Chemistry for Technologies Laboratory, University of Brescia , via Branze 38, 25123 Brescia, Italy.
authors.forename: Ivano
authors.initials: I
authors.lastname: Alessandri
authors.affiliation: Department of Chemistry and INSTM Ru, University of Parma , Parco area delle Scienze 17/A, 43124 Parma, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Biavardi
authors.affiliation: INSTM and Department of Molecular and Translational Medicine, University of Brescia , Viale Europa 11, 25123 Brescia, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Gianoncelli
authors.affiliation: INSTM and Department of Molecular and Translational Medicine, University of Brescia , Viale Europa 11, 25123 Brescia, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Bergese
authors.affiliation: Department of Chemistry and INSTM Ru, University of Parma , Parco area delle Scienze 17/A, 43124 Parma, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Dalcanale
mesh_terms: D004988:Ethers, Cyclic; D008239:Lysine / Q000737:chemistry*; D008745:Methylation; D012118:Resorcinols; D012822:Silicon Dioxide; D013059:Spectrum Analysis, Raman
chemical_list: D004988:Ethers, Cyclic; D012118:Resorcinols; C442939:cavitand; D012822:Silicon Dioxide; D008239:Lysine
keywords: Nε-methylated lysine; T-rex; all-dielectric beads; cavitands; core/shell colloids; plasmon-free SERS