title: Thermal and Chemical Stability of Thiol Bonding on Gold Nanostars.
abstract: The stability of thiol bonding on the surface of star-shaped gold nanoparticles was studied as a function of temperature in water and in a set of biologically relevant conditions. The stability was evaluated by monitoring the release of a model fluorescent dye, Bodipy-thiol (BDP-SH), from gold nanostars (GNSs) cocoated with poly(ethylene glycol) thiol (PEG-SH). The increase in the BDP-SH fluorescence emission, quenched when bound to the GNSs, was exploited to this purpose. A maximum 15% dye release in aqueous solution was found when the bulk temperature of gold nanostars solutions was increased to T = 42 °C, the maximum physiological temperature. This fraction reduces 3-5% for temperatures lower than 40 °C. Similar results were found when the temperature increase was obtained by laser excitation of the near-infrared (NIR) localized surface plasmon resonance of the GNSs, which are photothermally responsive. Besides the direct impact of temperature, an increased BDP-SH release was observed upon changing the chemical composition of the solvent from pure water to phosphate-buffered saline and culture media solutions. Moreover, also a significant fraction of PEG-SH was released from the GNS surface due to the increase in temperature. We monitored it with a different approach, that is, by using a coating of α-mercapto-ω-amino PEG labeled with tetramethylrhodamine isothiocyanate on the amino group, that after heating was separated from GNS by ultracentrifugation and the released PEG was determined by spectrofluorimetric techniques on the supernatant solution. These results suggest some specific limitations in the use of the gold-thiolate bond for coating of nanomaterials with organic compounds in biological environments. These limitations come from the duration and the intensity of the thermal treatment and from the medium composition and could also be exploited in biological media to modulate the in vivo release of drugs.
authors.affiliation: †Department of Physics "G. Occhialini", University of Milano Bicocca, piazza della Scienza 3, 20126 Milano, Italy.
authors.forename: Mykola
authors.initials: M
authors.lastname: Borzenkov
authors.affiliation: †Department of Physics "G. Occhialini", University of Milano Bicocca, piazza della Scienza 3, 20126 Milano, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Chirico
authors.affiliation: †Department of Physics "G. Occhialini", University of Milano Bicocca, piazza della Scienza 3, 20126 Milano, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: D'Alfonso
authors.affiliation: †Department of Physics "G. Occhialini", University of Milano Bicocca, piazza della Scienza 3, 20126 Milano, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Sironi
authors.affiliation: †Department of Physics "G. Occhialini", University of Milano Bicocca, piazza della Scienza 3, 20126 Milano, Italy.
authors.forename: Maddalena
authors.initials: M
authors.lastname: Collini
authors.affiliation: ‡Department of Chemistry, University of Pavia, viale Taramelli 12, 27100 Pavia, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Cabrini
authors.affiliation: ‡Department of Chemistry, University of Pavia, viale Taramelli 12, 27100 Pavia, Italy.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Dacarro
authors.affiliation: ‡Department of Chemistry, University of Pavia, viale Taramelli 12, 27100 Pavia, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Milanese
authors.affiliation: ‡Department of Chemistry, University of Pavia, viale Taramelli 12, 27100 Pavia, Italy.
authors.forename: Piersandro
authors.initials: P
authors.lastname: Pallavicini
authors.affiliation: ‡Department of Chemistry, University of Pavia, viale Taramelli 12, 27100 Pavia, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Taglietti
authors.affiliation: §Institut de Chimie Moléculaire de l'Université de Bourgogne, UMR CNRS 6302, Université de Bourgogne, 21078 Dijon, France.
authors.forename: Claire
authors.initials: C
authors.lastname: Bernhard
authors.affiliation: §Institut de Chimie Moléculaire de l'Université de Bourgogne, UMR CNRS 6302, Université de Bourgogne, 21078 Dijon, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Denat
mesh_terms: D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D013438:Sulfhydryl Compounds; D006046:Gold