Fluorescent and Cross-linked Organic–Inorganic
Hybrid Nanoshells for Monitoring Drug Delivery
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Abstract
Functionalized and monodisperse nanoshells
have attracted significant
attention owing to their well-defined structure, unique properties,
and wide range of potential applications. Here, the synthesis of cross-linked
organic–inorganic hybrid nanoshells with strong fluorescence
properties was reported via a facile precipitation polymerization
of hexachlorocyclotriphosphazene (HCCP) and fluorescein on silica
particles used as templates. The resulting poly(cyclotriphosphazene-<i>co</i>-fluorescein) (PCTPF) nanoshells were firm cross-linked
shells with ∼2.2 nm mesopores that facilitated the transport
of drug molecules. The fluorescent nanoshells also exhibited excellent
water dispersibility and biocompatibility; thus, they can be considered
as ideal drug vehicles with high doxorubicin storage capacity (26.2
wt %) and excellent sustained release (up to 14 days). Compared to
doxorubicin (DOX) alone, the PCTPF nanoshells more efficiently delivered
DOX into and killed cancer cells. Moreover, the PCTPF nanoshells also
exhibited remarkable fluorescent emission properties and improved
photobleaching stability in both suspension and solid state owing
to the covalent immobilization of fluorescein in the highly cross-linked
organic–inorganic hybrids. The exceptional fluorescent properties
enabled the release of DOX as well as the distribution of nanoshells
and DOX to be monitored