showed an excellent thermal stability even after refluxing in
water or ethanol for 3 days. Silica nanoparticles prepared by
direct modification of Rhodamine B and successive surface
modification,
SiO2(RhB)–OH,
SiO2(RhB)–PEG
and
SiO2(RhB)–PTMA, respectively, showed a cell viability 485%
and did not show any acute cytotoxicity to various cell types at
a level up to 100 mg mlÀ1 over 72 h. The continuous
monitoring experiments with MC3T3-E1 cells cultured with
SiO2(RhB)-PTMA clearly showed that our fluorescent nano-
particles did not affect the proliferation of MC3T3-E1 and
they could be used for long-term and multiple-time
bio-imaging systems.
This work was supported by the National Core Research
Center program of the Korea Science and Engineering
Foundation (KOSEF) through the NANO System Institute
at Seoul National University and grants from the NIAMS
(AR056090) and Emory University (G. R. B. Jr and C. E. C.).
Fig.
3 Fluorescent images of MC3T3-E1 cells incubated with
50 nm-sized, positively charged, orange fluorescent silica nano-
particles; 100 mg mlÀ1 of nanoparticles were added to the medium.
Notes and references
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membrane, with a dark nucleus clearly shown in fluorescent
images even after a few days of incubation.
Since the fluorescent dye molecules are chemically
embedded in the solid silica matrix have an excellent
photostability without susceptibility to photobleaching,3a,6a,9a
biocompatible and stable fluorescent silica nanoparticles
prepared in the present method by the direct modification of
fluorescent molecules could be used for biological experiments
which require the monitoring of multiple time points to
investigate the differentiation and/or development of cells.
As shown in Fig. 3(a) and (b), MC3T3-E1 cells incubated
with SiO2(RhB)-PTMA for 24 h showed a bright orange
fluorescence from the cytoplasm, and this was also clearly
observed from the floating cells after trypsinization (Fig. 3(b)),
treating with the trypsin enzyme commonly found in the
digestive tract which can be used to digest the proteins that
facilitate adhesion to the container and inter-cellularly, in
order to detach cells from the surface and divide into other
plates for subculturing. During the settlement of cells onto
new culture media (Fig. 3(c)–(f)), the movement of cell
spreading was easily monitored by fluorescent imaging.
Fluorescence could still be observed for several days as shown
in Fig. 3(g), (h) and (i), corroborating that our fluorescent
nanoparticles did not affect the proliferation of MC3T3-E1
cells or show photobleaching; which makes them very useful
as bio-imaging and tagging materials for long-term and
consecutive multiple-time monitoring experiments.
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from TEOS and directly derivatized fluorescent organic dye
molecules. They are highly dispersible in ethanol and water at
a range of pH from acidic to basic, along with a good thermal
stability. The surface-modified silica nanoparticles also
ꢀc
This journal is The Royal Society of Chemistry 2009
Chem. Commun., 2009, 2881–2883 | 2883