Fluorescence Quenching upon Binding of Copper Ions in Dye‐Doped and Ligand‐Capped Polymer Nanoparticles: A Simple Way to Probe the Dye Accessibility in Nano‐Sized Templates

Abstract

The synthesis and properties of well‐defined core–shell type fluorescent metal‐chelating polymer nanoparticles NP, in the 15 nm diameter range, with a fluorophore (9,10‐diphenylanthracene: DPA) entrapped in the particle core and a selective ligand (1,4,8,11‐tetraazacyclotetradecane: Cyclam), grafted onto the surface are presented. NPs with different number of dye‐per‐particle are readily obtained by entrapment of the fluorophore within the polymer core. The ligand‐coated NPs exhibit a high affinity for Cu2+ ions in aqueous solution and quenching of the DPA fluorescence is observed upon binding of copper. The quenching of fluorescence arises through energy transfer (FRET) from the dye to the copper‐cyclam complexes that form at the NP surface with an operating distance (d) in the 2 nm range. A simple core–shell model accounts for the steady‐state and time‐resolved fluorescence titration experiments: dye molecules located in the outer sphere (thickness d) of the NPs are quenched while the fluorescence of dyes embedded more deeply is not affected by the binding of copper ions. The observed high quenching efficiency (60–65 %), which is tightly correlated to the volumic and microstructural features of the NPs, shed light on the enhanced accessibility inherent in nano‐sized templates. The response towards different metal ions was investigated and this confirmed the selectivity of the nanoparticle template‐assembled sensor for cupric ions.

Improving the visualization of fluorescently tagged nanoparticles and fluorophore-labeled molecular probes by treatment with CuSO4 to quench autofluorescence in the rat inner ear

“…Metals in close proximity to chromophores are known to quench fluorescence in a distance dependent fashion (Richmond et al, 2000). Cupric ion was reported to quench fluorescence of DsRed (a bright red fluorescent protein), eGFP, and fluorescent dyes entrapped in nanoparticles by binding to amino acids close to the chromophores (Eli and Chakrabartty, 2006;Richmond et al, 2000;Gouanvé et al, 2007). When the emission spectra of chromophores (donor) are overlapped with the absorption spectrum of cupric ion (accepter), energy transfer from the donor to the accepter would happen.…”

“…When the emission spectra of chromophores (donor) are overlapped with the absorption spectrum of cupric ion (accepter), energy transfer from the donor to the accepter would happen. Cupric ion absorbs the energy at emission wavelength of the donor without re-emitting the energy fluorescently resulting in fluorescent quenching (Gouanvé et al, 2007). Yellow fluorescent components in lipofuscin are composed of proteinaceous material (Kikugawa et al, 1997).…”

A Core–Shell Nanoparticle Approach to Photoreversible Fluorescence Modulation of a Hydrophobic Dye in Aqueous Media

“…1 H NMR spectrum of SPCOOH. 1 H NMR (400 MHz, deuterated DMSO, 25°C, TMS) (ppm): 1.0 -1.3 (2 CH 3 ), 2.6 (CH 2 COO), 3.4 -3.5 (CH 2 N), 5.9 -6.0 (olefinic protons, 2H), 6.6 -8.2 (aromatic protons), 12.0 (COOH, hydrogen bonding). Figure S3.…”

A comparison of mono and multivalent linkers and their effect on the colloidal stability of nanoparticle and immunoassays performance

“…Dye-doped silica nanoparticles [13][14][15] (NP) stand out as excellent candidates as it is possible to dope silica NPs with a large number of fluorophores, increasing the total fluorescence of the label significantly [16,17]. Moreover, the fluorophore is protected inside a silica matrix, thereby increasing photostability [18,19] and quantum efficiency [20,21]. Silica NPs are also relatively non-toxic, chemically inert, and can be prepared in a range of sizes [22].…”