Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2002 Oct 1;99(20):12617-21.
doi: 10.1073/pnas.152463399. Epub 2002 Sep 16.

Nanocrystal targeting in vivo

Maria E Akerman  1 , Warren C W Chan, Pirjo Laakkonen, Sangeeta N Bhatia, Erkki Ruoslahti
Affiliations

Nanocrystal targeting in vivo

Maria E Akerman et al. Proc Natl Acad Sci U S A. .

Abstract

Inorganic nanostructures that interface with biological systems have recently attracted widespread interest in biology and medicine. Nanoparticles are thought to have potential as novel intravascular probes for both diagnostic (e.g., imaging) and therapeutic purposes (e.g., drug delivery). Critical issues for successful nanoparticle delivery include the ability to target specific tissues and cell types and escape from the biological particulate filter known as the reticuloendothelial system. We set out to explore the feasibility of in vivo targeting by using semiconductor quantum dots (qdots). Qdots are small (<10 nm) inorganic nanocrystals that possess unique luminescent properties; their fluorescence emission is stable and tuned by varying the particle size or composition. We show that ZnS-capped CdSe qdots coated with a lung-targeting peptide accumulate in the lungs of mice after i.v. injection, whereas two other peptides specifically direct qdots to blood vessels or lymphatic vessels in tumors. We also show that adding polyethylene glycol to the qdot coating prevents nonselective accumulation of qdots in reticuloendothelial tissues. These results encourage the construction of more complex nanostructures with capabilities such as disease sensing and drug delivery.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Schematic representation of qdot targeting. Intravenous delivery of qdots into specific tissues of the mouse. (Upper) Design of peptide-coated qdots. (Lower) Qdots were coated with either peptides only or with peptides and PEG. PEG helps the qdots maintain solubility in aqueous solvents and minimize nonspecific binding.
Figure 2
Figure 2
Binding of peptide-conjugated qdots to endothelial cells and breast cancer cells in vitro is specific to peptide sequence. (a) Binding of green GFE-conjugated qdots to LE cells that express membrane dipeptidase. (b and c) Inhibition of GFE-qdot binding to LE cells by free GFE peptide (500 μM) (b) or with cilastatin, an inhibitor of the receptor, membrane dipeptidase (50 μM) (c). (d) Quantification of fluorescence intensity of an experiment similar to the one illustrated in a–c. (Columns A–C) GFE-qdot binding to LE cells; GFE concentration 250 μM; and cilastatin 50 μM. (Column D) The binding of GFE-qdots to the LE cells is not inhibited by a control peptide (LyP-1; 250 μM). (Column E) LyP-1-qdots do not bind to the LE cells. The fluorescence associated with 10 individual cells from each panel was measured by using digital image analysis. Background fluorescence from cells that received no qdots has been subtracted (2 a.u., arbitrary units). A representative experiment of five experiments was quantified. (e and f) F3 qdots bind to MDA-MB-435 breast carcinoma cells (e); free F3 peptide (500 μM) inhibits the binding (f). (g) Binding of LyP-1 qdots to MDA-MB-435 cells. (h and i) GFE qdots do not recognize the MDA-MB-435 cells (h) and LyP-1 qdots do not bind to the LE cells (i). Nuclei were visualized with 4′,6-diamidino-2-phenylindole staining (blue). Cells were examined under an epifluorescence microscope with a 425/40-nm excitation and a 515-nm long-pass filter. (Original magnifications: a–c and i, ×200; and e–h, ×400.)
Figure 3
Figure 3
In vivo targeting of qdots to normal lung vasculature is specific. Red GFE-conjugated qdots were injected into the tail vein of normal mice, and the presence of qdots in lung tissue was assessed by examining sections under a confocal microscope with UV excitation and a 585-nm long-pass filter (a and b) or an epifluorescent microscope as in Fig. 2 (c and d). (a) Red qdots localized in lung tissue. (b) Inhibition of qdot accumulation in the lungs by coinjected cilastatin. (c and d) Absence of GFE qdots in the brain (c) and kidney (d) demonstrates the specificity of binding. The results shown are representative of three experiments carried out with nine mice. (Original magnifications: a and b, ×600; c and d, ×200.)
Figure 4
Figure 4
In vivo targeting of qdots to tumor vasculature is specific. Red F3 or LyP-1 qdots, both PEG-coated, were injected into the tail vein of nude BALB/c mice bearing MDA-MB-435 breast carcinoma xenograft tumors. Blood vessels were visualized by coinjecting tomato lectin (green). (a) F3 qdots colocalize with blood vessels in tumor tissue. (b) LyP-1 qdots also accumulate in tumor tissue, but do not colocalize with the blood vessel marker. (c) Red F3 qdots and green LyP-1 qdots injected into the same tumor mouse target different structures in tumor tissue. (d) GFE qdots that bind to normal LE injected into tumor mice are not detected in tumor tissue. (e) F3 qdots injected into tumor mice do not appear in the skin taken from an area next to the tumor. A longer exposure was used in d and e to bring out the tissue background. (f) LyP-1 qdots are internalized by cells in tumor tissue. Images a, b, and f were obtained with a confocal microscope, and images c–e were obtained with an epifluorescent microscope as in Fig. 2. The results shown are representative of experiments carried out with six mice for the F3 qdots and 12 mice for the LyP-1 qdots. (Original magnifications: a and d, ×400; b and c, ×600; e, ×200; and f, ×2,400.)
Figure 5
Figure 5
Qdot uptake by the reticuloendothelial system is reduced by PEG coating. Green LyP-1 qdots with or without an added PEG coating were adjusted to an equal concentration by measuring absorbance at 540 nm and injected into the tail vein of mice bearing MDA-MB-435 tumors. Qdot localization in reticuloendothelial tissues was studied by epifluorescent microscopy of tissue sections as in Fig. 2. (a and b) LyP-1 qdots in the liver (a) and spleen (b). (c and d) LyP-1/PEG qdots in the liver (c) and spleen (d). These images are representative of three independent experiments. (Original magnifications: ×200.)
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

References

    1. Niemeyer C M. Angew Chem. 2001;40:4128–4158. - PubMed
    1. Chan W C, Maxwell D J, Gao X, Bailey R E, Han M, Nie S. Curr Opin Biotechnol. 2002;13:40–46. - PubMed
    1. Alivisatos A P. Science. 1996;271:933–937.
    1. Han M, Gao X, Su J Z, Nie S. Nat Biotechnol. 2001;19:631–635. - PubMed
    1. Ruoslahti E. Semin Cancer Biol. 2000;10:435–442. - PubMed

Publication types

LinkOut - more resources