In vivo near‐infrared fluorescence imaging of cancer with nanoparticle‐based probes

Schematic representation of a typical core–shell NIRF dye‐containing nanoparticle design.

NIR transillumination images (Ex 755 nm, Em 830 nm) taken at various times track fluorescence signals and pharmacokinetic distributions for the indocyanine green calcium phosphate nanoparticles (ICG‐CPNPs) and controls delivered systemically via tail vein injections in nude mice implanted with subcutaneous human breast adenocarcinoma tumors. Hash (‐) marks next to each mouse indicate the position of the 5‐mm tumors. (a) NIR transillumination images taken at 3 h to track fluorescence signals for the indocyanine green calcium phosphate nanoparticles (ICG‐CPNPs) and the controls delivered systematically via tail vein injections in nude mice implanted with subcutaneous human breast adenocarcinoma tumors. Two control samples, (i) carboxylate‐terminated CPNPs without ICG encapsulant and (ii) free ICG, match the particle concentration and fluorophore content (10¹³ particles/mL and 10⁻⁵ M, respectively) of a (iii) PEGylated ICGCPNP sample. (b, ii) No fluorescence signal is detected from the free ICG at 24‐h postinjection, while the PEG‐ICG‐CPNP sample (c, iii) retains significant signal even after 96 h. (b, iii) Fluorescence signal is unmistakably localized in tumors 24 h after administration with PEGylated ICG‐CPNPs. The excised organs in panel (d) illustrate the biliary clearance route 10‐min postinjection of PEG‐ICG‐CPNPs. Fluorescence signal is not seen from the stomach or spleen with minimal renal involvement. (Reproduced with permission from Ref 49. Copyright 2008 American Chemical Society).

Schematic representation of the three ways to incorporate molecules into lipoprotein particles. (a) Direct conjugation of the molecules to the amino acid residues of apolipoproteins. (b) Incorporation of the molecules into the phospholipid monolayer via an intercalation mechanism. (c) Reconstitution into the apolar core.

(a) Schematic illustrations of rerouted low‐density lipoproteins (LDL) nanocarrier (bottom) with folic acid (FA) targeting ligand (middle) and 1,1′‐dioctadecyl‐3,3,3′, 3′‐tetramethylin‐dotricarbocyanine iodide (DiR)‐based NIR fluorescent label (top). (b) Real time in vivo fluorescence images of KB/HT1080 dual tumor mice with i.v. injection of DiR‐LDL‐FA (5.8 µM). (Reproduced with permission from Ref 60. Copyright 2007 American Chemical Society).

Schematic and optical properties of CdS‐capped CdTe_xSe_1−x alloyed near‐IR‐emitting quantum dots (QDs). (a) Biocompatible near‐IR‐emitting QDs contain a core structure (CdTe_xSe_1−x) with a CdS and an organic shell. The outer organic shell contains functional groups for attaching biorecognition molecules to the QD surface. (b) Absorbance and fluorescence spectra of CdS‐capped CdTe_xSe_1−x near‐IR‐emitting QDs with different compositions of Te:Se in the core. (Reproduced with permission from Ref 74. Copyright 2006 American Chemical Society).

Design and spectroscopic characterization of bioluminescent quantum dot conjugates based on bioluminescence resonance energy transfers (BRET). (a) A schematic of quantum dot that is covalently coupled to a BRET donor, luc8. The bioluminescence energy of luc8‐catalyzed oxidation of coelenterazine is transferred to the quantum dots, resulting in quantum dot emission. (b) Absorption and emission spectra of quantum dot 655 (Ex 480 nm), and spectrum of the bioluminescent light emitted in the oxidation of coelenterazine catalyzed by luc8. (Reproduced with permission from Ref 82. Copyright 2006 Nature).

A schematic of quantum dot (QD)705‐arginine–glycine–aspartic acid (RGD), PEG denotes poly(ethylene glycol) synthesis and in vivo NIR fluorescence imaging of U87MG tumor‐bearing mice (left shoulder, pointed by white arrows) injected with 200 pmol of QD705‐RGD (left) and QD705 (right), respectively. All images were acquired under the same instrumental conditions. The mice autofluorescence is color coded green while the unmixed QD signal is color coded red. Prominent uptake in the liver, bone marrow, and lymph nodes was also visible. (Reproduced with permission from Ref 90. Copyright 2006 American Chemical Society).

(a) One weight percentage colloidal solutions of nanocrystals in dichloromethane excited at 977 nm demonstrating upconversion luminescence. (i) NaYF4: 2% Er³⁺, 20% Yb³⁺ solution showing its transparency. (ii) Total upconversion luminescence of NaYF4: 2% Er³⁺, 20% Yb³⁺ solution. (iii and iv) NaYF4: 2% Er³⁺, 20% Yb³⁺ upconversion viewed through green and red filters, respectively. (v) NaYF4: 2% Tm³⁺, 20% Yb³⁺ solution. (b) Transmission electron microscopy (TEM) image of NaYF4: 2% Er³⁺, 20% Yb³⁺ nanocrystals. Inset: High‐resolution TEM image of a single nanocrystal. (c) Low‐resolution transmission electron micrographs of NaYF4: 2% Er³⁺, 20% Yb³⁺ samples showing uniformity of the particles. (Reproduced with permission from Ref 102,103. Copyright 2006, 2007 American Chemical Society).

In vivo imaging of rat: quantum dots (QDs) injected into translucent skin of foot (a) show fluorescence, but not through thicker skin of back (b) or abdomen (c); PEI/NaYF₄: Yb, Er nanoparticles injected below abdominal skin (d), thigh muscles (e), or below skin of back (f) show luminescence. QDs on a black disk in (a and b) are used as control. (Reproduced with permission from Ref 126. Copyright 2008 Elsevier).