[21] QD Tumor-targeted Fluorescence Imaging in Vivo in Vitro

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One-Pot Synthesized Aptamer-Functionalized CdTe:Zn2+ QuantumDots for Tumor-Targeted Fluorescence Imaging in Vitro and in VivoCuiling Zhang, Xinghu Ji, Yuan Zhang, Guohua Zhou, Xianliang Ke, Hanzhong Wang,

Philip Tinnefeld, and Zhike He*,

Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and MolecularSciences, Wuhan University, Wuhan 430072, P. R. ChinaState Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, P. R. ChinaPhysical and Theoretical Chemistry, NanoBioScience, TU Braunschweig, Hans-Sommer-Strasse 10, 38106 Braunschweig, Germany

*S Supporting Information

ABSTRACT: High quality and facile DNA functionalizedquantum dots (QDs) as efficient fluorescence nanomaterials

are of great signifi

cance for bioimaging both in vitro and invivo applications. Herein, we offer a strategy to synthesizeDNA-functionalized Zn2+ doped CdTe QDs (DNA-QDs)through a facile one-pot hydrothermal route. DNA is directlyattached to the surface of QDs. The as-prepared QDs exhibitsmall size (3.85 0.53 nm), high quantum yield (up to80.5%), and excellent photostability. In addition, the toxicity ofQDs has dropped considerably because of the Zn-doping andthe existence of DNA. Furthermore, DNA has been designedas an aptamer specific for mucin 1 overexpressed in manycancer cells including lung adenocarcinoma. The aptamer-functionalized Zn2+ doped CdTe QDs (aptamer-QDs) have beensuccessfully applied in active tumor-targeted imaging in vitro and in vivo. A universal design of DNA for synthesis of Zn2+ dopedCdTe QDs could be extended to other target sequences. Owing to the abilities of specific recognition and the simple synthesisroute, the applications of QDs will potentially be extended to biosensing and bioimaging.

F luorescence imaging is commonly used as one of the mostpotent tools for tumor-targeted imaging from cells andtissues of living animals.13 Functionalized quantum dots(QDs),

which are modified and doped with biomolecules, have beenwidely applied in fluorescence imaging, and it is necessary andimportant that these have good biocompatible, specific targeting,and excellent fluorescence properties. DNA functionalized QDsare among the most studied functionalized QDs for fluorescenceimaging. A common approach for obtaining DNA functionalizedQDs is via simple avidinbiotin interaction due to its selectivityand strong binding (Kd = 10

15 M).4 However, it is difficult tocontrol the binding site of a given biotin unit and the orientation

of the biotin-appended DNA on the QD, because avidin has fourbinding sites. Also, the cross-linking and large size of avidin-coated QDs are unfavorable for fluorescence imaging applica-tions.58 Moreover, the previous investigations of ourgrouphaverevealed that thelarge-size QDs could hardlyenter cells.9,10 Ithas

been realized that the optimal QDs for fluorescence imagingexhibit continuous light emission and have a size of 415 nm as

well as low cytotoxicity.11

Core/shell structure and environmentally friendly materialsare considered to be the potentialities due to the low toxicity. Todate, many new types of QDs such as core/shell (CdSe/ZnS,CdTe/ZnS), core/shell/shell (CdTe/CdS/ZnS, CdSe/CdTe/ZnSe), and environmentally friendly CuInSe, Ag2S, and Si QDs

nanomaterials have been developed.1220 Besides, metal-dopedQDs, forinstance, Mn2+ doped CdSe QDs and Zn2+ doped CdTeQDs by aqueous-phase synthesis have showed low cellulartoxicity, high quantum yield, excellent biocompatibility, andsmall size.21,22 However, these QDs are sensitive to theexperimental conditions, and it is difficult to functionalizethem with DNA. More recently, DNA has been demonstrated to

be unique ligands for the aqueous synthesis of QDs.2326

Especially, cadmium-based QDs is one of the most studiedsystems for DNA-templated synthesis. The small, stable, and

water-soluble cadmium-based QDs can be generated in one step,and the DNA molecules on the QD surface possess

biorecognition capabilities that can be directly applied to specifictargeting.25,27 The functionalized QDs have been widely appliedin biosensing, bioimaging, and self-assembly.2831 However, theQDs containing the highly toxic heavy metal element(cadmium)32 have low quantum yield and low output (400 Lof product at 4 M), which are still the limitation for biomedicalapplications. Thus, an improved methodto prepare DNAlabeledQDs which meets the request of perfect QDs with small size, low

Received: February 26, 2013Accepted: May 20, 2013Published: May 20, 2013

Article

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toxicity, and good fluorescence properties is ultimately neededfor fluorescence imaging.

Herein, labeling DNA on Zn2+ doped CdTe QDs (DNA-QDs) by the one-pot method has been accomplished. The QDshave high quantum yield (up to 80.5%) and high output (2 mL ofproduct at 30M). Because of the doping with Zn, the QDs havereduced toxicity. The unique functional domain of DNA onCdTe:Zn2+ QDs is designed as the aptamer which can recognizemucin 1. Mucin 1 has been widely overexpressed in human lungadenocarcinoma cells.33 In this research, the A549 cells (humanlung adenocarcinoma epithelial cell line) were chosen as thetarget cell. It is worth mentioning that the aptamer-QDs have

been designed for the first time for application in active tumor-targeted imaging in vitro and in vivo.

EXPERIMENTAL SECTION

Chemicals and Materials. NAC (98%), rhodamine 6G,sodium phosphate monobasic dihydrate (NaH2PO42H2O),sodium phosphate dibasic dodecahydrate (Na2HPO412H2O),sodium chloride (NaCl), dimethyl sulfoxide (DMSO), andHoechst 33342 were commercially available from Sigma (USA).

3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT) was bought from Amresco (USA). Dulbeccos modifiedEagle medium (DMEM) was purchased from Gibco Inc.CdCl22.5H2O, ZnCl2, tellurium powder (99.999%), and sodium

borohydride (NaBH4) were obtained from Sinopharm ChemicalReagent (China) and were used as received without additionalpurification. All chemicals used were of analytical grade or of thehighest purity available. Modified DNA, 5-TCCGCTGCAGA-

AAAA AAT*C*G*G*G*C*G*T*A*C-3 (* indicates thephosphorothioate linkage), modified aptamer, GCAGTTGA-TCCTTTG GATACCCTGGAAAA AAT*C*G*G*G*C*G*-T*A*C-3, complementary modified DNA, 5-TTCTGCAG-CGGA-3, and SYBR green 1 were synthesized by ShanghaiSangon Biotechnology Co. Ltd. (Shanghai, China). The mucin 1

with two repeats of the 20 amino acid variable tandem repeatregion (from the N terminus to the C terminus: PDTRPAPGSTAPPAHGVTSAPDTRPAPGSTAPPAHGVTSA) was syn-thesized by the ChinaPeptides Co., Ltd. (Shanghai, China). Allsolutions were prepared using ultrapure water obtained from theMilli-Q system (Millipore, USA).

Preparation of DNA Functionalized Zn Doping CdTeNanocrystals. The DNA-QDs solution was synthesized byreacting NaHTe with Cd2+ and Zn2+, in which NAC andmodified DNA are the stabilizing reagents at pH 9.0. The freshNaHTe solution was obtained by the reaction of 25 mg of Tepower and 20 mg of NaBH4 in 1 mL of water at 0 C for 5 h.Then, the fresh NaHTe solution was injected into 2 mL ofoxygen-free aqueous solution containing CdCl22.5H2O andZnCl2 at pH 9.0. Sequentially, DNA solution containing 1.5 M

nucleotides was added to the mixture. The molar ratio of Cd, Zn,Te, and NACused was 1:2:0.2:3.6. Last, the mixture solution wastransferred to a Teflon lined stainless steel autoclave and heatedto the growth temperature (200 C). In order to get the pureQDs at the end of the synthesis, the reaction solution waspurified by ultrafiltration using an Amicon Ultra-4 centrifugalfilter device with a MW cut offof 30 kDa (Millipore Corp., USA)The as-prepared products were stored at 4 C or lyophilized toobtain the QD powder for characterization. The quantum yieldsof QDs were determined by rhodamine 6G (95%, as referencestandard) and rhodamine B (98%, as reference standard).34

The labeling efficiency was calculated as follows: theconcentrations of CdTe:Zn2+ QDs and DNA-QDs were

estimated by the absorption spectra according to a reportedmethod.35 The concentration of DNA was calculated from theabsorbance at 260 nm after subtracting the contribution of QDs,for QDs make a contribution to the absorbance at 260 nm. Themolar extinction coefficient of DNA is 2 105 M1 cm1by thesynthesis report of DNA. Then, the DNA to QDs ratio wascalculated accordingly.

Hybridization between DNA-QDs and ComplementaryDNA. The hybridization reaction was performed by mixingDNA-QDs and the complementary DNA. First, 0, 5, and 10 Lof 1 M complementary DNA in 10 mM PBS buffer solution(pH 7.4, 15 mM NaCl) were added into DNA-QDs solution.Then, the buffer solution was added into a final volume of 500Land held about 30 min. The final concentration of QDs was 8nM. TwentyL of SYBR green 1 (diluted 10 000 times of theoriginal solution) was added and held about 5 min. At last, thefluorescence signals of QDs and SYBR green 1 were detected.

Cell Cytotoxicity Assay. The cytotoxicity of DNA-QDs wasevaluated by the MTT assay. A549 cells were cultured in 96 wellplates at a density of 2500 cells per well in 200 L of DMEM andthen cultured 16 h at 37 C. QDs (CdTe, CdTe:Zn2+,CdTe:Zn2+-DNA) were added to each wel l to a finalconcentration of 0, 0.375, 0.75, 0.15, 0.3, 0.6, 1.2, and 2.4 M.96 well plates were incubated for 24 h. After that, the supernatant

was replaced with fresh DMEM (200 L). TwentyL of 5 mgL1 MTT was added to each well, and then, the PBS buffersolution was added to a final volume of 200 L. The mixture wasremoved after being incubated for 4 h; 200 L of DMSO wasadded to each well to dissolve formazan crystals by rude shock for1 min. The absorbance at 570 nm was measured using amicroplate reader (Bio-Rad550, USA). Data was collected inquadruplicate, and the final data was averaged. The percentrelative viability of A549 cells related to the control wellcontaining PBS buffer without QDs was calculated by thefollowing equation:

=

A A A Acell viability (%) ( )/( )

100

sample blank control blank

(1)

where Asample is the absorbance of the solution containing cellscultured with QDs,Ablankis the absorbance of the PBS buffer,and

Acontrol is the absorbance of the cells only.DNA-QDs Applied in Tumor Targeting in Vitro and in

Vivo. First, the nuclei of A549 cells and Vero cells were stainedwith Hoechst 33342 simply by adding the dye (5 g/mL, 30min) to theDMEM with 10%heat-inactivated fetal bovine serum(FBS) culture medium, and the cells were washed three times.Second, the cells were cultured (37 C, 5% CO2) with 200 nMaptamer-QDs (4 C, 30 min, and 45 min) or first 600 nM

aptamer (4 C, 30 min) and then 200 nM aptamer-QDs (4 C,30 min). Then, the cells were washed three times with buffer.Finally, thefluorescence images were measured on the UltraView

VOX confocal system (PerkinElmer, USA) attached to aninverted microscope (Nikon, Japan) with 488 nm laserexcitation; 100 objective lenses were chosen for observation.The images of QDs interaction with cells were dealt with the

Volocity software.The tumor-bearing nude mice were supplied by Wuhan

BioMed Science & Technology Co. Ltd. (China) The sizes oftumors were about 0.5 cm3. Two nmol of aptamer QDs ornonaptamer QDs was injected into a nude mouse by tail veininjection. Then, mice were anesthetized with ketamine (40 mg/

Analytical Chemistry Article

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kg). After 10 min, mice were imaged with the Maestro in vivoimaging system(Cambridge Research & Instrumentation, USA).

Apparatus and Characterization. UVvis absorptionspectra were obtained by a Shimadzu UV-2550 spectropho-tometer (Japan). Fluorescence spectra were measured on aShimadzu RF-5301 fluorescence spectrophotometer (Japan).The FT-IR spectra were recorded on a Perkin-Elmer-2spectrometer (USA). A TEM sample was made by droppingQD aqueous solution onto ultrathin carbon-coated copper grids.TEM images were conducted on a JEM 2100 transmissionelectron microscope (Japan). A dynamic light scattering (DLS)measurement was measured on the Zetasizer instrumentZEN3600 (Malvern, UK) with a 173 back scattering angleand HeNe laser ( = 633 nm). The crystal phase of QDs wascharacterized by a Bruker D8 Discover X-ray Diffractometer(German) with 2range from 10 to 70 at a scanning rate of 2per minute. The interactions between aptamer and mucin 1protein were characterized on the chirascan dichroismspectrometer (Applied Photophysics, UK).

RESULTS AND DISCUSSIONThe design strategy is illustrated in Figure 1. The one-pothydrothermal process permits the preparation of high zinc

content, good photostability, and high quantum yield DNA-QDswith antioxidant N-acetylcysteine (NAC) ligand. DNA was usedas the coligand to obtain the DNA functionalized QDs (Figure1B). This DNA ligand contains three domains, phosphoro-thioates which bind to QDs because of their high affinity tocadmium, linker, and functional domain. Structures ofphosphorothioates and functional domain are shown in Figure1A. In the present synthesis strategy, DNA is crucial to thegrowth of QDs. Amine and carbonyl groups are responsible for

surface passivation; steric and/or secondary conformation effectsof the capping strands play an important role in stabilizing thecolloids, and overall surface reactivity of the sequences mainlyinfluences the quality of nanocrystals.25,26,36During the synthesisprocess, the CdTe:Zn2+ QDs were gradually formed, and the Satoms in the phosphorothioates domain of the designed DNA

were inserted into CdTe:Zn2+ QDs.However, functional domain(nonphosphorothioates) extended away from the surfaces ofCdTe:Zn2+ QDs and was available for recognition to thecomplementary DNA, peptide, or protein.

Crystal Structure and Hydrodynamic Diameter Char-acterizations of DNA-QDs. The transmission electronmicroscopy (TEM) image had shown that the DNA-QDs were

spherical particles and well dispersible (Figure 2A). The highlycrystalline structure of the DNA-QDs was visualized on the highresolution TEM (HRTEM) image (inset in Figure 2A). Asshown in Figure 2B, X-ray diffraction (XRD) characterizationexhibited that the prepared DNA-QDs belonged to thecubiczinc

blende structure. A size distribution histogram of DNA-QDs(em: 574 nm) was obtained by measuring more than 300particles, which revealed the particle sizes of DNA-QDs of 3.85 0.53 nm (Figure 2C). Dynamic light scattering (DLS, Figure 2D)

was performed to determine the hydrodynamic diameter of theQDs. In comparison, the corresponding average hydrodynamicdiameter of the DNA-QDs in water was about 7.3 nm. Thedifference in diameter measured by TEM and DLS should beattributed to the surface DNA ligand of the DNA-QDs inaqueous solution. Most importantly, the small size of as-preparedDNA-QDs is advantageous for bioimaging compared to theDNA-labeled QDs bridged by avidinbiotin.

Availability of DNA on the CdTe:Zn2+QDs. Theavailability of DNA on the QDs was tested by hybridization

with complementary DNA in combination with SYBR green 1staining (Figure S1, Supporting Information). SYBR green 1 is afluorescent asymmetrical cyanine dye whose fluorescence is very

weak in aqueous solution. The fluorescence is dramaticallyincreased when it binds to double stranded DNA (dsDNA) butnot single stranded DNA (ssDNA).37 By this strategy, thedsDNA was formed by hybridizing the DNA on the surface ofQDs with the complementary DNA, andwhen SYBR green 1 wasadded, the fluorescence of it was increased sharply. The morecomplementary DNA was added, the stronger was thefluorescence intensity of SYBR green 1 observed. All of theseresults have verified the availability of the DNA on the surface ofQDs.

UVVis Absorption and Fluorescence Spectra of DNA-QDs and CdTe:Zn2+ QDs. DNA-QDs and CdTe:Zn2+ QDsshow similar UVvis absorption and fluorescence spectra,indicating that the DNA does not negatively influence the

luminescence properties of the QDs (Figure S2, SupportingInformation). The absorption at 260 nm of DNA-QDs isattributed to DNA, further supporting that the DNA is attachedto the QDs. In addition, the spectrum of the DNA-QDs is blue-shifted by 3 nm compared with CdTe:Zn2+ QDs. This resultindicates that the DNA ligand may interact electronically withthe crystal surface and alter its electronic properties.28,29

Optical Properties of the As-Prepared DNA-QDs. DNA-QDs with different colors are prepared by controlling thereaction time. Figure 3A,B shows the UVvis spectra and thefluorescence spectra of a series of as-prepared DNA-QDs withmaximum emission wavelengths ranging from 546 to 646 nm,respectively. The corresponding emission decay times of DNA-QDs display a gradual increase from 23.7 1.0 to 34.0 1.2nsas

the emission wavelength increased (Figure 3C). Overall, the as-prepared DNA-QDs exhibit a high quantum yield (up to 80.5%),long fluorescence decay times, and narrow emission bands (seephotographs in Figure 3D and Table S1 in SupportingInformation). Furthermore, we could obtain 2 mL of DNA-QDs solution at a concentration of 30 M by the one-potmethod. This up scaling is important to meet the need ofquantity in biological applications.

Figure 4 shows the photostability result. The DNA-QDs andCdTe QDs solutions were irradiated continuously over a periodof60 min.Thefluorescence intensity of CdTe QDs solution onlyremained at 35% of the initial value, while the fluorescenceintensity of DNA-QDs stabilized at around 62%. This suggested

Figure 1. Schematic illustration of structures of (A) phosphorothioatesand functional domain and (B) the one-pot synthesized DNA-QDsroute.




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that the DNA-QDs had a better photostability for tracing over

extended time periods as well as for imaging.Controllability Numbers of DNA Molecules per QD.

Under the same conditions, the numbers of DNA per QD are

different with different amounts of DNA added (Figure S3,

Supporting Information). In order to vary the number of DNAmolecules per QD, different amounts of initial DNA were added.The numbers of DNA sequences per QD were determined to be

Figure 2. (A) TEM image (inset: the HRTEM image); (B) the XRD of the prepared DNA-QDs ( em = 574 nm), the standard pattern of CdTe QDs(JCPDs card 15-0770) is also offered at the bottom lane; (C) the size distribution; (D) dynamic light scatting histogram.

Figure 3. (A) UVvis spectra, (B) fluorescence spectra, and (C) fluorescence lifetime decay curves of DNA-QDs with controllable maximum emissionwavelengths ranging from 546 to 646 nm. (D) Photographs of the aqueous solution of DNA-QDs under UV irradiation and visible light conditions by adigital camera. The samples were directly extracted from the original solution right after reaction without further treatment.




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0.36, 1.3, 1.83, and 2.67 (when the added ratios of DNA are1:1,1.3:1, 1.7:1, and 2.6:1, respectively) using UV absorption ofDNA-QDs and CdTe:Zn2+ QDs. It suggested that the numbersof DNA per QD could be one or two by controlling the amountof DNA.

In Vitro Cytotoxicity. Cytotoxicity assessment of QDs isanother critical consideration for the bioimaging application. Inthe present study, we used the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay to estimate thecytotoxicity at various concentrations of CdTe QDs, CdTe:Zn2+

QDs, and DNA-QDs. This method has been widely used toquantify cell death of A549 cells.38,39As shown in Figure 5, theCdTe QDs were obviously the most toxic, and the DNA-QDs

were less toxic than CdTe:Zn2+ QDs. Fortunately, the A549 cells

maintained more than 40% viability following the treatment withDNA-QDs at concentrations as high as 2.4 M. In contrast, theviability of A549 cells treated with CdTe:Zn2+ QDs degraded to14%, and the viability of A549 cells treated withCdTeQDs at the

same concentration was only 7%. That is, DNA-QDs have thelowest toxicity within this series. Besides, the toxicity of CdTeQDs has been discussed comprehensively in previous research;32

0.3 M of CdTe QDs could lead to 80% of cell death, while 0.3M of DNA-QDs could keep 50% of cells viable. There are tworeasons for this phenomenon. First, high Zn doped ratio (thesurface molar ratio of Zn to Cd is 1:1) plays a key role. Second,DNA capping may also reduce toxicity, for that can improve thestability and prevent the release of toxic components.40,41All ofthese results indicated that DNA-QDs showed a promisingprospect in bioimaging application.

Characteristics of Interactions between Aptamer andMucin 1 by Circular Dichroism. Mucin 1 is overexpressedover 90% in late stage epithelial ovarian cancers and metastaticlesions but not in normal ovarian tissues.42 The DNA aptamerspecific for mucin 1 was previously reported to assist doxorubicinenter cells for treatment of multidrug resistant ovarian cancer. Itis therefore an interesting candidate that was used as therecognition domain of DNA. For the following experiments, wesynthesized aptamer-QDs (the recognition area of DNA wasdesigned as the aptamer of mucin 1) which could have specific

binding with mucin 1, which was known to be expressed on thecell surface of A549 cells.43 To clarify the interactions betweenaptamer and mucin 1, the circular dichroism (CD) experiment

was performed. Figure S5 (Supporting Information) has shownthe CD spectra of aptamer-QDs, mucin 1, aptamer-QDs-mucin 1complex, and aptamer-mucin 1 complex. Aptamer-QDs havealmost no absorption at the far ultraviolet region. The CDspectrum of the 40-amino acid synthetic peptide (2 repeats)contains a large negative peak at around 206 nm. This spectrumis characteristic of proline-rich repeat proteins.44,45 Whenaptamer or aptamer-QDs were added to the mucin 1 solution,the negative peak decreased, which demonstrated that thestructure of mucin 1 was destroyed because of interactions

between aptamer and mucin 1.In Vitro and in Vivo Targeted Imaging. To demonstrate

the aptamer-QDs as tumor cellular target probes, we furtheremployed our aptamer-QDs for in vitro imaging. The aptamer-QDs were first evaluated for tumor targeting in this paper. Theconfocal images confirmed strong binding of the aptamer-QDsto A549 cells (Figure 6A). The aptamer-QDs were mainlydistributed near the membrane within a 30 min incubation timeat 4 C. When the incubation time lasted longer (45 min), thesehad been spread mostly to cytoplasm and near nuclearmembrane (Figure S6, Supporting Information). A controlexperiment using Vero cells, mucin 1-negative kidney cells,showed little binding to the membrane (Figure 6B). Additionalcontrol experiment using DNA-QDs, which were not linked withmucin 1 aptamer but with a random sequence, also showed theabsence of binding (Figure 6C). The specific interaction

experiment was done by pretreating A549 cancer cells withaptamer and then incubating with the aptamer-QDs (Figure6D); there was almost no fluorescence. From such results,aptamer-QDs could be applied in tumor targeting in vitro. To the

best of our knowledge, this is the first report of evaluatingaptamer-QDs which were synthesized by a one-pot hydro-thermal method for tumor-targeted imaging.

To further investigate the feasibility of aptamer-QDs in vivo,we conducted lung cancer tumor targeting and imaged in liveanimals. To start with, the aptamer-QDs and nonaptamer QDs

were intravenously injected into tumor-bearing nude mice.Figure 7 shows fluorescence images of the tumor-bearing miceinjected with different QDs. No signals were observed from the

Figure 4. Photostability of DNA-QDs (black) andCdTe QDs(red)(Xelamp, 150 W, Ex: 350 nm).

Figure 5. Cytotoxicity of A549 cells incubated with differentconcentrations of DNA-QDs (a), CdTe:Zn2+ QDs (b), and CdTeQDs (c) for 24 h.




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tumor-bearing mouse treated with nonaptamer QDs; on thecontrary, strong signals located at the tumor could be seen fromthe mouse treated with aptamer-QDs. This finding issubstantiated byfluorescence images of tumor organs that alsoshowed higher accumulation of the targeting aptamer-QDs(Inset in Figure 7B). All of these data demonstrated that theaptamer-QDs had high selectivity and sensitivity for active tumortargeting in vivo. These results reveal that the aptamer-QDs canserve as efficient probes for future tumor diagnosis applications.

CONCLUSIONS

In this study, DNA functionalized Zn-doped CdTe QDs weredirectly synthesized through a facile one-pot hydrothermal route.The QDs exhibit high quantum yield, low cellular toxicity, smallsize, excellent photostability, and biocompatibility. Mostimportantly, the as-prepared aptamer-QDs were well suitablefor in vitro and in vivo imaging of tumor targeting. Compared to

other methods of DNAfunctionalized QDs, these DNA-QDs aremore adaptable for the further study of highly specific andsensitive bioimaging. Such DNA-QDs are promising tools fordisease diagnosis.

ASSOCIATED CONTENT

*S Supporting InformationDetails for fluorescence spectra, UVvis spectra, and FT-IRcharacterizations. This material is available free of charge via theInternet at http://pubs.acs.org.

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected].

Author Contributions

The manuscript was written through contributions of all authors.All authors have given approval to the final version of themanuscript.

Notes

The authors declare no competing financial interest.

ACKNOWLEDGMENTS

This work was financially supported by the National KeyScientific Program Nanoscience and Nanotechnology(2011CB933600), the National Science Foundation of China425 (21275109, 21075093), Large-scale Instrument and Equip-ment Sharing Foundation of Wuhan University,and academic

award for excellent Ph.D. Candidates funded by Ministry ofEducation of China 427 (5052012203001).

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Figure 6. Confocal fluorescent tumor cellular target studies of QDs. (A)A549 cells, which are mucin 1-positive, as shown in the presence of theCdTe:Zn2+-aptamer QDs (aptamer-QDs) binding to the cell surface;(B) the negative control was noted in Vero cells that lack mucin 1expression incubated with aptamer-QDs; (C) the negative control wasdetected in A549 cells incubated with DNA-QDs which were not linkedwith mucin 1 aptamer but with a random sequence; (D) A549 cells werefirst incubated with aptamer and then aptamer-QDs. Scale bars: 7 m.

Figure 7. (A) Fluorescence images and (B) photographs of tumor-bearing mice injected with aptamer-QDs (2 nmol, left) and nonaptamer

QDs (right). Tumor organs of the mice were also analyzed (insets in B).The autofluorescence of the mouse was removed by spectral unmixing.All images were obtained under the same experimental conditions.


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[21] QD Tumor-targeted Fluorescence Imaging in Vivo in Vitro

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