We introduce shell cross-linked
protein/
quantum dot (QD) hybrid
nanocapsules as a serum-stable systemic delivery nanocarrier for
tumor-targeted in vivo bio-imaging applications. Highly luminescent,
heavy-metal-free Cu0.3InS2/ZnS (CIS/ZnS) core-shell QDs are synthesized and mixed with
amine-reactive six-armed poly(
ethylene glycol) (PEG) in
dichloromethane. Emulsification in an aqueous
solution containing
human serum albumin (HSA) results in shell cross-linked
nanocapsules incorporating CIS/ZnS QDs, exhibiting high luminescence and excellent dispersion stability in a serum-containing medium.
Folic acid is introduced as a
tumor-targeting
ligand. The feasibility of
tumor-targeted in vivo bio-imaging is demonstrated by measuring the fluorescence intensity of several major organs and
tumor tissue after an intravenous tail vein injection of the
nanocapsules into nude mice. The cytotoxicity of the QD-loaded HSA-PEG
nanocapsules is also examined in several types of cells. Our results show that the cellular uptake of the QDs is critical for cytotoxicity. Moreover, a significantly lower level of cell death is observed in the CIS/ZnS QDs compared to
nanocapsules loaded with
cadmium-based QDs. This study suggests that the systemic
tumor targeting of
heavy-metal-free QDs using shell cross-linked HSA-PEG hybrid
nanocapsules is a promising route for in vivo
tumor diagnosis with reduced non-specific toxicity.