Experimental and theoretical studies of the optimisation of fluorescence from near-infrared dye-doped silica nanoparticles

Biomedical Diagnostics Institute, National Centre for Sensor Research, School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9, Ireland.
Analytical and Bioanalytical Chemistry (Impact Factor: 3.44). 11/2008; 393(4):1143-9. DOI: 10.1007/s00216-008-2418-9
Source: PubMed


There is substantial interest in the development of near-infrared dye-doped nanoparticles (NPs) for a range of applications including immunocytochemistry, immunosorbent assays, flow cytometry, and DNA/protein microarray analysis. The main motivation for this work is the significant increase in NP fluorescence that may be obtained compared with a single dye label, for example Cy5. Dye-doped NPs were synthesised and a reduction in fluorescence as a function of dye concentration was correlated with the occurrence of homo-Förster resonance energy transfer (HFRET) in the NP. Using standard analytical expressions describing HFRET, we modelled the fluorescence of NPs as a function of dye loading. The results confirmed the occurrence of HFRET which arises from the small Stokes shift of near-infrared dyes and provided a simple method for predicting the optimum dye loading in NPs for maximum fluorescence. We used the inverse micelle method to prepare monodispersed silica NPs. The NPs were characterised using dynamic light scattering, UV spectroscopy, and transmission electron microscopy (TEM). The quantum efficiency of the dye inside the NPs, as a function of dye loading, was also determined. The fluorescent NPs were measured to be approximately 165 times brighter than the free dye, at an optimal loading of 2% (w/w). These experimental results were in good agreement with model predictions.

The change in nanoparticle fluorescence versus increased dye loading modelled using homo-Förster resonance energy transfer.

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Available from: Xavier Le Guével, Jul 01, 2014
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    • "All chemicals were obtained from Sigma Aldrich, (Sigma-Aldrich Corp., St. Louis, MO) unless otherwise stated. Silica nanoparticles (φ=74 nm) containing fluorescein (3 (w/w)) and synthetic premiR-34a (0.1 (w/w)), or a scrambled miR-negative control (0.1 (w/w)) were prepared using a microemulsion method [71]. The mechanism for formation of silica nanoparticles, outlined in Figure S1C, involves hydrolysis and condensation of a silica precursor (tetraethylorthosilicate). The proposed mechanism of drug delivery is dissolution of the nanoparticle and release of the dye under physiological conditions via hydrolysis of the silica network. "
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