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The targeted labeling imaging of stellate cells on liver frozen section by immunofluorescence is a very promising visualization technique to study the distribution of stellate cells in the liver. In this study, water soluble carbon quantum dots that can emit blue, green and yellow fluorescence are synthesized by the hydrothermal method, and their sizes are 3.2, 3.7, and 4.3 nm, respectively. The three carbon quantum dots have good fluorescence stability, and the quantum yields are 36.1%, 26.3% and 21%, respectively. When the mass fraction of KCl in the blue carbon quantum dot dispersion system is 13%, it still maintains the liquid state at -30 °C. The final fluorescent probe is obtained after the carbon quantum dots are coupled with the secondary antibody, spectral characterizations confirm that the conjugate probe still maintains protein immunoactivity and has good stability. Cell experiments prove that the probe has good biocompatibility, the rabbit anti-mouse Desmin antibody is used as the primary antibody, the results of cellular immunofluorescence imaging and flow cytometry show that the probe can specifically label hepatic stellate cell at -20 °C. The results of liver frozen section experiments show that hepatic stellate cell can be specifically targeted and labeled by the fluorescent probe. This labeling technology provides an important technical means for elucidating the structure and function of the liver at the cellular level, exploring the liver pathological change, and designing and developing drug., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

A method for simultaneous labeling and multicolor fluorescence imaging of different hepatic immune cells below freezing point is established based on quantum dots. In the experiment, carbon quantum dots with emission wavelength of 435 nm, CdTe@CdS quantum dots at 542 nm and CdSe@ZnS quantum dots at 604 nm are synthesized respectively, it is found that when the mass fractions of KCl (as antifreeze) are 12 %, 14 %, and 12 %, respectively, the three quantum dot dispersion systems remain liquid state at -20 °C. After they are conjugated with the corresponding secondary antibodies, agarose gel electrophoresis, circular dichroism and capillary electrophoresis confirm the effectiveness of conjugation. By indirect immunofluorescence method, the above three quantum dot fluorescent probes are used to simultaneously and specifically target a variety of liver immune cells, and the multi-color simultaneous imaging of different liver immune cells is realized under the same excitation wavelength, it is found that hepatic macrophages are arranged radially in the liver, hepatic stellate cells present punctate distribution, and hepatic sinusoidal endothelial cells present circular distribution, which is consistent with the results of H&E staining and ultrathin section TEM. This study provides an important technical means for elucidating the structure and function of the liver., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Chirality is a fundamental phenomenon of nature, and the enantioselective recognition of amino acids isomers is especially important for life science. In this study, chiroptical system based on chiral assembly graphene quantum dots (GQDs) was developed for visual testing of D-phenylalanine (D-Phe). Here, GQDs were used as the fluorescent element, and chiral functional moieties of 1,3,5-triformylphloroglucinol-functionalized chiral ( +)-diacetyl-L-tartaric anhydride (TPTA) were used as the chiral recognition elements. Based on the formed chiral microenvironment, the fluorescence intensity of TPTA-assembled GQDs had a good linear relationship with D-Phe in the concentration range of 0.1-5 μM, and the detection limit was 0.023 μM. According to the variation in luminance of TPTA-assembled GQDs, visual testing to D-Phe was realized using a smartphone-assisted chiroptical system with a detection limit of 0.050 μM. The spiked recoveries of both chiroptical sensing methods based on TPTA-assembled GQDs from the food matrix ranged from 86.20 to 110.0%. Furthermore, TPTA-assembled GQDs were successfully applied to intracellular chiroptical imaging in response to D-Phe in vitro. The developed chiral nanomaterial TPTA-assembled GQDs with excellent photochemical stability, optical properties, and bioimaging capabilities provide a promising technique for the visual detection of amino acid isomers in the field of smart devices., (© 2022. Springer-Verlag GmbH Germany, part of Springer Nature.)

Taking the hepatic sinusoid (HS) as the main delivery area of liver nutrients and metabolic waste, recognizing its structure is important for a deep understanding of liver function. In this paper, based on lycopersicon esculentum lectin (LEL), with targeting ability for endothelial cells, and carbon quantum dots (CQDs), with high biosafety, an LEL-coupled CQD immunofluorescence probe (CQD@LEL) that can label microvessels is designed and used for the fluorescence labeling and imaging of HS in liver tissue sections. The CQD size is approximately 2 nm. Blue fluorescence is emitted under excitation; its optimal excitation wavelength is 400 nm while the emission is at about 450 nm. Gel electrophoresis and capillary electrophoresis confirm that glutaraldehyde can couple LEL to CQD, and the obtained CQD@LEL retains the fluorescence property and has good stability. Optimization experiments show that its labeling effect is positively correlated with time and probe concentration for dyeing the blood vessels of mouse liver slices. In order to improve the effect further, a probe concentration of 0.17 mg mL -1 and incubation time of 3 h were chosen to label the liver tissue sections. The results show that the liver microvessels are formed by interstitial structures among the hepatic cords, and the HS presents a granular or patchy appearance. H&E and ultrathin section TEM show that the microvascular wall of the liver is composed of discontinuous endothelial cells, and there are Kupffer cells and other cells in the tubes, proving that our probe can clearly label the structure and morphology of liver microvessels. This work is of great significance for the visualization of HS.

CdTe@CdS core-shell quantum dots with different particle sizes are synthesized by an aqueous method, and coating them with a CdS shell layer improves the quantum yield (36% → 59%) and fluorescence stability (37% → 77%) of CdTe@CdS quantum dots. When the KCl concentration (mass fraction) in the system is 15%, the CdTe@CdS quantum dot dispersion system remains in the liquid state at -20 °C, and the low temperature increases the fluorescence intensity. A QD-Ab probe is obtained after CdTe@CdS quantum dots are coupled with IgG; the circular dichroism shows that the IgG protein structure is not destroyed, while capillary electrophoresis, agarose gel electrophoresis and flow cytometry verify the conjugation efficiency. With rabbit anti-mouse EMR1 antibody as the primary antibody and QD-Ab as the secondary antibody, the hepatic macrophages in liver frozen sections are fluorescently labeled at -20 °C, and it is found that they are radially distributed in hepatic sinusoids with specific and highly efficient labeling; these results are verified by H&E staining and TEM. This technology can provide important technical support for in-depth understanding of the distribution of liver immune cells in the liver, and it can further provide a scientific basis to understand the relationship between the liver structure and function and pathological changes.

A nanoplatform based on Ag 2 S quantum dots (QDs) and tellurium nanorods (TeNRs) was developed for combined chemo-photothermal therapy guided by H 2 O 2 -activated near-infrared (NIR)-II fluorescence imaging. Polypeptide PC 10 AGRD-modified TeNRs and Ag 2 S QDs were co-encapsulated in 4T1 cell membrane to prepare a nanoplatform (CCM@AT). Ag 2 S QDs and TeNRs in the CCM@AT were used as a fluorescence probe and photosensitizer, and a chemotherapeutic prodrug and quenching agent to quench the fluorescence of Ag 2 S QDs, respectively. After the CCM@AT was specifically targeted to the tumor site, the TeNRs were dissolved by the high concentration of H 2 O 2 at the tumor site to light up the fluorescence of Ag 2 S QDs for NIR-II fluorescence imaging. In addition, the generated toxic TeO 6 6- S quantum dots (QDs) with NIR-II fluorescence emission and good photothermal conversion efficiency are used as a fluorescence probe and photosensitizer, and tellurium nanorods (TeNRs) are used as a chemotherapeutic prodrug and quenching agent to quench the fluorescence of Ag 2 S quantum dots (QDs) with NIR-II fluorescence emission and good photothermal conversion efficiency are used as a fluorescence probe and photosensitizer, and tellurium nanorods (TeNRs) are used as a chemotherapeutic prodrug and quenching agent to quench the fluorescence of Ag 2 S QDs. This multiple nanoplatform provides an inspiration for the combination therapy of tumor guided by NIR-II fluorescence imaging., Competing Interests: Declaration of Competing Interest The authors declare no competing financial interest., (Copyright © 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

In this paper, CdSe/ZnS quantum dots (QDs) with particle size of 5.5 ~ 9.3 nm were synthesized, and the fluorescence emission ranged from 545 ~ 616 nm. When the volume fraction of ethanol was 30%, the water-soluble QD dispersion system remained liquid under -20 °C freezing conditions, the fluorescence intensity increased with a decrease in temperature, and the quantum yield reached 79% at -20 °C. The endothelial cell adhesion molecule CD31 antibody (anti-CD31) was used as the primary antibody, QDs were coupled with IgG as the secondary antibody (QD-Ab), and effective labeling of hepatic sinusoid endothelial cells was achieved at -20 °C. Fluorescence imaging and flow cytometry analysis showed that the labeling efficiency was as high as 97%, indicating that QDs have an important application prospect in microscopic section tomography of the liver., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Water-soluble fluorescence nanomaterials are widely applied for water-phase food safety monitoring. However, there is still a challenge for the development of oil-soluble fluorescence nanomaterials for oil-phase food safety detection. Particularly, the edible oil quality has a huge impact on human health, in which excessive acid number (AN), 3-chloro-1,2-propanediol (3-MCPD), and moisture content (MC) are critical monitoring factors. Herein, orange-emitting oil-soluble CsPbBr 1.5 I 1.5 quantum dots (QDs) were prepared and applied for AN and 3-MCPD detection depending on fluorescence quenching and wavelength shifts. A "turn-off" fluorescence sensor and "wavelength-shift" fluorescence colorimetric sensor were fabricated for AN and 3-MCPD detection. Water-sensitive mesoporous silica-coated CsPbBr 1.5 I 1.5 QDs were employed for the establishment of ratiometric fluorescence sensors for MC monitoring by introducing water-stable green-emitting CsPbBr 3 nanosheets (NSs) as reference probes. Perovskite nanomaterial-engineered multiplex-mode fluorescence sensors were proposed for the detection of AN, 3-MCPD, and MC in edible oil, with the limits of detection (LODs) of 0.71 mg KOH/g, 39.8 μg/mL 3-MCPD, and 0.45% MC, respectively. This work not only expands the application of perovskite nanomaterials in the bioanalysis field but also provides new materials and novel approaches for the multiplex-mode oil-phase food safety monitoring.

Given their superior penetration depths, photosensitizers with longer absorption wavelengths present broader application prospects in photodynamic therapy (PDT). Herein, Ag 2 S quantum dots were discovered, for the first time, to be capable of killing tumor cells through the photodynamic route by near-infrared light irradiation, which means relatively less excitation of the probe compared with traditional photosensitizers absorbing short wavelengths. On modification with polydopamine (PDA), PDA-Ag 2 S was obtained, which showed outstanding capacity for inducing reactive oxygen species (increased by 1.69 times). With the addition of PDA, Ag 2 S had more opportunities to react with surrounding O 2 , which was demonstrated by typical triplet electron spin resonance (ESR) analysis. Furthermore, the PDT effects of Ag 2 S and PDA-Ag 2 S achieved at longer wavelengths were almost identical to the effects produced at 660 nm, which was proved by studies in vitro. PDA-Ag 2 S showed distinctly better therapeutic effects than Ag 2 S in experiments in vivo, which further validated the enhanced regulatory effect of PDA. Altogether, a new photosensitizer with longer absorption wavelength was developed by using the hitherto-unexplored photodynamic function of Ag 2 S quantum dots, which extended and enhanced the regulatory effect originating from PDA., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Ag 2 S quantum dots have received extensive attention as theranostic agents for second near-infrared (NIR-II) fluorescence and photoacoustic dual-mode imaging, and photothermal therapy. However, it is still greatly challenging to synthesize Ag 2 S quantum dots using aqueous synthesis. In this study, genetically engineered polypeptide-capped Ag 2 S quantum dots were successfully synthesized. Three cysteines were integrated to the C-terminal and N-terminal of RGDPC 10 A to enhance the stability and brightness of the synthesized Ag 2 S quantum dots. The RGDPC 10 A-capped Ag 2 S quantum dots exhibited excellent stability, outstanding resistance to photobleaching, and a superior quantum yield of up to 3.78% in the NIR-II biological window. The in vitro and in vivo results showed that the RGDPC 10 A-capped Ag 2 S quantum dots possessed typical NIR-II fluorescence, photoacoustic imaging, and photothermal therapeutic effectiveness against tumors. Moreover, the results of toxicity assays suggested that the RGDPC 10 A-capped Ag 2 S quantum dots have negligible long-term toxicity. These findings open up the possibility for synthesizing theranostic agents by using this aqueous method.

A graphene quantum dot (GQD) is a novel carbon nanomaterial with the advantages of low cost and no pollution. It has attracted serious attention in the biomedical fields because of its stabilities and tunable fluorescence wavelength. In this manuscript, an N-doped graphene quantum dot (N-GQD) was synthesized by a hydrothermal method using citric acid as the carbon source and urea as the nitrogen source. X-ray diffraction, Raman spectroscopy, transmission electron microscopy, UV-vis absorption spectrum, and fluorescence spectrum were used to characterize the N-GQD. The results showed that the N-GQD had a uniform size of about 5 nm. The two fluorescence emission peaks, one in the visible light region showed a 49.75% quantum yield, while another in the near infrared region was 2.49%. The photothermal conversion efficiency was 62.53%, higher than any kind of carbon nanomaterial in existence today. MTT and a long-term cytotoxicity experiment confirmed that the N-GQD had low cytotoxicity. The probe also had the ability of photoacoustic response at the same time. After coupling with folic acid, it presented imaging and photothermal therapy on the cells, which has great application prospects in the early diagnosis and treatment of tumors.

Background: Ag 2 S has the characteristics of conventional quantum dot such as broad excitation spectrum, narrow emission spectrum, long fluorescence lifetime, strong anti-bleaching ability, and other optical properties. Moreover, since its fluorescence emission is located in the NIR-II region, has stronger penetrating ability for tissue. Ag 2 S quantum dot has strong absorption during the visible and NIR regions, it has good photothermal and photoacoustic response under certain wavelength excitation., Results: 200 nm aqueous probe Ag 2 S@DSPE-PEG 2000 -FA (Ag 2 S@DP-FA) with good dispersibility and stability was prepared by coating hydrophobic Ag 2 S with the mixture of folic acid (FA) modified DSPE-PEG 2000 (DP) and other polymers, it was found the probe had good fluorescent, photoacoustic and photothermal responses, and a low cell cytotoxicity at 50 μg/mL Ag concentration. Blood biochemical analysis, liver enzyme and tissue histopathological test showed that no significant influence was observed on blood and organs within 15 days after injection of the probe. In vivo and in vitro fluorescence and photoacoustic imaging of the probe further demonstrated that the Ag 2 S@DP-FA probe had good active targeting ability for tumor. In vivo and in vitro photothermal therapy experiments confirmed that the probe also had good ability of killing tumor by photothermal., Conclusions: Ag 2 S@DP-FA was a safe, integrated diagnosis and treatment probe with multi-mode imaging, photothermal therapy and active targeting ability, which had a great application prospect in the early diagnosis and treatment of tumor.

Graphene quantum dot (GQD) has been attractive in analytical science field due to its low toxicity, stable photoluminescence. Herein, nitrogen-doped GQD (N-GQD) was prepared by a facile solvothermal treatment of GO using dimethylformamide, and exhibited a green emission with 23.1% quantum yield. The N-GQD probe showed a selective and sensitive fluorescence enhancement response to Al 3+ , the mechanism might be the formation of a complex between Al 3+ and N-GQD constrained the photo-induced electron transfer (PET) process of N-GQD itself. With Benesi-Hildebrand equation, the binding constant and molar ratio between N-GQD and Al 3+ was calculated to be 4.6 × 10 4 Lmol -1 and 1:1 respectively. The pK a value of N-GQD was also determined to be 4.4 by capillary electrophoresis. In pH 4.0 PBS solution, there was a good linear relation between the fluorescence intensity and the logarithm of concentration of Al 3+ in the range of 2.5-75μmolL -1 , the limit of detection (3σ) was 1.3μmolL -1 . This "Off - On" fluorescence method had been applied to accurate quantification of aluminum in hydrotalcite tablets. What's more, the fluorescence switch property of N-GQD was explored by alternate addition of Al 3+ and EDTA. The probe was also utilized for detection Al 3+ in living cells due to its excellent biocompatibility., (Copyright © 2017 Elsevier B.V. All rights reserved.)

In this study, an oil-soluble Ag 2 S quantum dot (QD) was synthesized through thermal decomposition using the single-source precursor method, and Pluronic F127 (PF127), a triblock copolymer functionalized with folic acid (FA), was deposited on the surface of the QD, then a water-soluble PF127-FA@Ag 2 S nanoprobe with targeting ability was fabricated. The as-prepared PF127-FA@Ag 2 S exhibited spheroidal morphology and high dispersibility, with average diameters of 115 ± 20.7 nm (as observed by transmission electron microscopy). No obvious toxicity of the PF127-FA@Ag 2 S nanoprobe was found in standard 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay and colony-formation assay, indicating good biocompatibility and safety. The resulting PF127-FA@Ag 2 S exhibited excellent stability between 4 °C-40 °C. Additionally, the capacity of the tumor cell-targeting high contrast enhanced photoacoustic imaging of PF127-FA@Ag 2 S was verified in comparison with A547 and HeLa cells. In other words, the excellent properties of PF127-FA@Ag 2 S show great potential in further research for targeting and photoacoustic imaging.

A high quantum yield (4.3%) hybrid nanogel system based on engineered polypeptides and Ag 2 S quantum dots has been developed as a multifunctional diagnostic and therapeutic agent for targeted second near-infrared fluorescence, photoacoustic imaging, and photothermal therapy.

In this article, a fluorescence-CT dual-mode nanoprobe is successfully synthesized by making use of distearoylphosphatidylethanolamine-poly(ethylene glycol)-folate (DSPE-PEG2000-FA) and other amphiphilic molecules to coat silver sulfide (Ag2S) quantum dots (QDs) and iodinated oil simultaneously. In vitro experiments show that the fluorescence wavelength of the nanoprobe is 1170 nm in the near infrared-II region. Its size is 139.6 nm, it has good dispersibility, and it has low cellular toxicity at concentrations up to 25 μg mL(-1) Ag. In vivo experiments revealed that the probe has a rather long circulation time (blood half-life of 5.7 hours), and the tissue histopathological tests show that it is not obviously harmful to major organs' normal function. Biochemical analysis (glutamic pyruvic transaminase and glutamic oxaloacetic transaminase levels) and blood analysis (white blood cell, red blood cell, hemoglobin and blood platelet counts) reveal that it has little influence on blood within 15 days of administration. When injected into HeLa xenograft nude mice by the tail vein, the probe elicited intensely enhanced fluorescence and X-ray computed tomography (CT) signals in the tumors after 24 hours, and the structure, size and position of tumor tissue were shown clearly. In a word, the probe has good tumor targeting capabilities, and it has significant value in fluorescence-CT dual-mode imaging in vivo.

Quantum dot (QD)-polypeptide probes have been developed through the specific metal-affinity interaction between polypeptides appended with N-terminal polyhistidine sequences and CdSe/ZnS core-shell QDs. The size and charge of a QD-polypeptide can be tuned by using different coiled-coil polypeptides. Compared to glutathione-capped QDs (QD-GSH), QD-polypeptide probes showed an approximately two- to three-fold luminescence increase, and the luminescence increase was not obviously related to the charge of the polypeptide. QD-polypeptide probes with different charge have a great effect on nonspecific cellular uptake. QD-polypeptide probes with negative charge exhibited lower nonspecific cellular uptake in comparison to the QD-GSH, while positively charged QD-polypeptide probes presented higher cellular uptake than the QD-GSH. A targeted QD-ARGD probe can obviously increase targeted cellular uptake in α v β 3 overexpressing HeLa cells compared to QD-A. In addition, QD-polypeptide probes showed lower in vitro cytotoxicity compared to the original QDs. These results demonstrate that these QD-polypeptide probes with high specific cellular uptake, high fluorescence intensity and low background noise are expected to have great potential applications in targeted cell imaging.

Background: X-ray computed tomography (CT) imaging can be used to reveal the three-dimensional structure of deep tissue with high spatial resolution. However, it cannot reveal molecular or cellular changes, and has great limitations in terms of specificity and sensitivity. Fluorescence imaging technology is one of the main methods used for the study of molecular events in vivo and has important applications in life science research. Therefore, the combination of CT and fluorescence imaging is an ideal dual-modal molecular imaging method, which can provide data on both molecular function and tissue structure, and has important research value. In a previous study, Bi2S3 nanoparticles were wrapped with quantum dots in SiO2 to generate CT and fluorescence imaging. However, this type of probe led to low survival and caused innegligible in vivo toxicity in mice. Therefore, it is necessary to develop new multifunctional probes that demonstrate biocompatibility and safety in vivo., Methods: A polyethylene glycol-phospholipid bilayer structure was used to synthesize hybrid clusters containing hydrophobic Bi2S3 nanoparticles and quantum dots for combined CT/fluorescence imaging. Mean particle size, polydispersity index, and zeta potential were used to study the stability over an 8-week test period. In vivo CT and fluorescence imaging experiments were performed, and the in vivo safety of the probe was evaluated, using histopathological, biochemical, and blood analyses., Results: The probe distinctly enhanced the CT contrast and had fluorescence imaging capability. In addition, the nanocomposite hybrid clusters showed a longer circulation time (>4 h) than iobitridol. The results also showed that the Bi2S3-QD@DSPE probe had good biocompatibility and safety, and did not affect normal organ functioning., Conclusions: Bi2S3-QD@DSPE hybrid clusters exhibited remarkable performance in CT angiography and fluorescence imaging in vivo.

In this study, silica coated Au nanospheres (Au@SiO2) were prepared by a reverse microemulsion method; subsequently, a layer of fluorescent quantum dots (QDs) were adsorbed onto it and then it was coated with silica again. After modifying with PVP, the composite silica coated gold nanosphere and quantum dots nanoparticle (Au@SiO2-QDs/SiO2-PVP) was obtained. This composite structure contained Au and QDs, and it could be used for contrast-enhanced X-ray CT imaging and fluorescence imaging. Characterization showed that the composite nanoparticle had good dispersity, a high fluorescence intensity and a good effect of X-ray absorption, and it was suitable for using as a bimodal imaging probe.

A new type of multifunctional quantum dot (QD)-polypeptide hybrid nanogel with targeted imaging and drug delivery properties has been developed by metal-affinity driven self-assembly between artificial polypeptides and CdSe-ZnS core-shell QDs. On the surface of QDs, a tunable sandwich-like microstructure consisting of two hydrophobic layers and one hydrophilic layer between them was verified by capillary electrophoresis, transmission electron microscopy, and dynamic light scattering measurements. Hydrophobic and hydrophilic drugs can be simultaneously loaded in a QD-polypeptide nanogel. In vitro drug release of drug-loaded QD-polypeptide nanogels varies strongly with temperature, pH, and competitors. A drug-loaded QD-polypeptide nanogel with an arginine-glycine-aspartic acid (RGD) motif exhibited efficient receptor-mediated endocytosis in αvβ3 overexpressing HeLa cells but not in the control MCF-7 cells as analyzed by confocal microscopy and flow cytometry. In contrast, non-targeted QD-polypeptide nanogels revealed minimal binding and uptake in HeLa cells. Compared with the original QDs, the QD-polypeptide nanogels showed lower in vitro cytotoxicity for both HeLa cells and NIH 3T3 cells. Furthermore, the cytotoxicity of the targeted QD-polypeptide nanogel was lower for normal NIH 3T3 cells than that for HeLa cancer cells. These results demonstrate that the integration of imaging and drug delivery functions in a single QD-polypeptide nanogel has the potential for application in cancer diagnosis, imaging, and therapy.

The mixture of graphene oxide (GO) and aptamer labeled fluorophore is widely used in developing fluorescent sensors for the analysis of biomolecules, according to the light signal 'off-on' procedure. Moreover, the laser-induced fluorescence-coupled affinity probe capillary electrophoresis (APCE) technique has been broadly applied for the separation of micromolecules. Here, a strategy is proposed for analysis of content of carcino-embryonic antigen (CEA) based on the combination of GO and quantum dots labeling aptamer (QD-aptamer) by capillary electrophoresis (CE). The method has three advantages: (i) combined with CE, only few samples are required and efficiency of separation is high, (ii) fluorescent detection can be carried out after separation of GO and fluorescence probe combined with targets by CE, while fluorescence detection sensitivity had been greatly improved, and (iii) the issues of APCE, including the effect of excess fluorescence probe and maximizing separation between analytes, could be solved by introducing GO. It has been proved that QD-aptamer-CEA complex can completely dissociate from GO. Results show that the fluorescence intensity has a linear relationship with the concentration of CEA in the range from 0.257 to 12.9 ng/mL, and the limit of detection is approximately 5 pg/mL (S/N=3). The proposed method with high specificity has been applied for the accurate analysis of content of CEA in patient׳s serum., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Incorporating ligands with nanoparticle-based carriers for specific delivery of therapeutic nucleic acids (such as antisense oligonucleotides and siRNA) to tumor sites is a promising approach in anti-cancer strategies. However, nanoparticle-based carriers remain insufficient in terms of the selectivity and transfection efficiency. In this paper, we designed a dual receptor-targeted QDs gene carrier QD-(AS-ODN+GE11+c(RGDfK)) which could increase the cellular uptake efficiency and further enhance the transfection efficiency. Here, the targeting ligands used were peptides GE11 and c(RGDfK) which could recognize epidermal growth factor receptors (EGFR) and integrin ανβ3 receptors, respectively. Quantitative flow cytometry and ICP/MS showed that the synergistic effect between EGFR and integrin ανβ3 increased the cellular uptake of QDs carriers. The effects of inhibition agents showed the endocytosis pathway of QD-(AS-ODN+GE11+c(RGDfK)) probe was mainly clathrin-mediated. Western blot confirmed that QD-(AS-ODN+GE11+c(RGDfK)) could further enhance gene silencing efficiency compared to QD-(AS-ODN+GE11) and QD-(AS-ODN+c(RGDfK)), suggesting this dual receptor-targeted gene carrier achieved desired transfection efficiency. In this gene delivery system, QDs could not only be used as a gene vehicle but also as fluorescence probe, allowing for localization and tracking during the delivery process. This transport model is very well referenced for non-viral gene carriers to enhance the targeting ability and transfection efficiency.

Monodispersed Bi2S3-QD@SiO2-PEG nanoparticles are prepared by a one-pot method in a reverse microemulsion system, which exhibited remarkable performances in CT and fluorescence imaging in vitro and in vivo.

Based on the multivalent binding capability of streptavidin (SA) to biotin, a multifunctional quantum dot probe (QD-(AS-ODN+p160)) coupled with antisense oligonucleotide (AS-ODN) and peptide p160 is designed for real-time tracking of targeted delivery of AS-ODN and regulation of folate receptor-α (hFR-α) in MCF-7 breast cancer cells. Fluorescence spectra, capillary electrophoresis (CE) and dynamic light scattering (DLS) are used to characterize the conjugation of AS-ODN and p160 with quantum dots (QDs), DLS results confirm the well stability of the probe in aqueous media. Confocal imaging and quantitative flow cytometry show that QD-(AS-ODN+p160) is able to specifically target human breast cancer MCF-7 cells. Low temperature and ATP depletion treatments reveal the cellular uptake of QD-(AS-ODN+p160) is energy-dependent, and the effects of inhibition agents and co-localization imaging further confirm the endocytic pathway is mainly receptor-mediated. Transmission electron microscopy (TEM) shows the intracellular delivery and endosomal escape of QD probe along with incubation time extended. Two transfection concentrations of QD probe (10 nM and 50 nM) below half inhibitory concentration (IC50 ) value are chosen according to MTT assay. Real-time PCR shows at these two concentration cases the relative mRNA expression levels of hFR-α reduce to 72.5 ± 3.9% and 17.6 ± 1.0%, respectively. However, western blot and quantitative ELISA analysis show the expression level of hFR-α protein has a significant decrease only at 50 nM, indicating that gene silence is concentration-dependent. These results demonstrate that the QD-(AS-ODN+p160) probe not only achieves gene silence in a cell-specific manner but also achieves real-time tracking during AS-ODN intracellular delivery., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Quantum dots (QDs) fluorescent probes based on oligonucleotide aptamers and peptides with specific molecular recognition have attracted much attention. In this paper, CdSe/ZnS QDs probes for targeted delivery to mouse and human cells using aptamer GS24 and peptide T7 specific to mouse/human transferrin receptors were developed. Capillary electrophoresis analyses indicated that the optimal molar ratios of QDs to aptamer or peptide were 1:5. Fluorescence and confocal microscope imaging revealed QD-GS24 and QD-T7 probes were able to specifically recognize B16 cells and HeLa cells respectively. Quantitative flow cytometry analysis indicated the transportation of QD-GS24 or QD-T7 into cells could be promoted by corresponding free transferrin. Transmission electron microscopy confirmed the uptake of probes in cells and the effective intracellular delivery. MTT assay suggested the cytotoxicity of probes was related to the surface ligand, and aptamer GS24 (or peptide T7) could reduce the cytotoxicity of probes to a certain degree. The study has great significance for preparing QDs fluorescent probes using non-antibody target molecules.

In this paper, we prepared three types of transferrin-quantum dots conjugates (QDs-Tf) using three different methods (electrostatic interaction, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) coupling, denatured transferrin (dTf) coating). Fluorescence emission spectra, surface characteristics, zeta potentials of quantum dots (QDs) and QDs-Tf fluorescent probes were characterized by spectrophotometer, capillary electrophoresis, and dynamic light scattering. Fluorescent imaging of HeLa cells was also performed by QDs and QDs-Tf fluorescent probes. It was found that the fluorescence imaging performances of QDs-Tf probes prepared by electrostatic interaction and EDC coupling were better compared with the one prepared by dTf coating. Then a real-time single cell detection system was established to quantitatively evaluate cell labeling effects of QDs-Tf fluorescent probes. It was found that for cell labeling efficiency, the proportion of cells labeled by quantum dot probes to a group of cells, QDs-Tf probe prepared by EDC coupling showed the highest labeling efficiency (85.55±3.88%), followed by electrostatic interaction (78.86±9.57%), and dTf coating showed the lowest (40.09±10.2%). This efficiency order was confirmed by flow cytometry results. This study demonstrated the relationship between conjugation methods and the resultant QDs-Tf probes and provided a foundation for choosing appropriate QDs-Tf probes in cell labeling., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Here the distance dependence of metal-enhanced quantum dots (QDs) fluorescence in solution is studied systematically by capillary electrophoresis (CE). Complementary DNA oligonucleotides-modified CdSe/ZnS QDs and gold nanoparticles (Au NPs) were connected together in solution by the hybridization of complementary oligonucleotides, and a model system (QD-Au) for the study of metal-enhanced QDs fluorescence was constructed, in which the distance between the QDs and Au NPs was controlled by adjusting the base number of the oligonucleotide. In our CE experiments, the metal-enhanced fluorescence of the QDs solution was only observed when the distance between the QDs and Au NPs ranged from 6.8 to 18.7 nm, and the maximum enhancement by a factor of 2.3 was achieved at 11.9 nm. Furthermore, a minimum of 19.6 pg of target DNA was identified in CE based on its specific competition with the QD-DNA in the QD-Au system. This work provides an important reference for future study of metal-enhanced QDs fluorescence in solution and exhibits potential capability in nucleic acid hybridization analysis and high-sensitivity DNA detection.

Here a novel capillary electrophoresis (CE) for simultaneous detection of dual single-base mutations using quantum dot-molecular beacon (QD-MB) probe is described. Two QD-MB probes were designed using 585 and 650-nm emitting CdTe QDs which were covalently conjugated to MBs with different DNA oligonucleotide sequences by amide linkage and streptavidin-biotin binding, respectively. The hybridizations of QD-MB probes with different DNA targets were then monitored by CE, and results indicated that the two QD-MB probes specifically hybridized with their complementary DNA sequences, respectively. Target DNA identification was observed to have a high sensitivity of 16.2 pg in CE. Furthermore, the simultaneous detection of dual single-base mutations in a given DNA oligonucleotide was successfully achieved in CE using above two QD-MB probes. This novel CE-assisted QD-MB biosensor offers a promising approach for simultaneous detection of multiple single-base mutations, and exhibits potential capability in the single nucleotide polymorphism (SNP) analysis and high-sensitivity DNA detection., (Copyright © 2010 Elsevier B.V. All rights reserved.)

The optical properties of antiphotobleaching and the advantage of long-term fluorescence observation of quantum dots are fully adopted to study the effects of iron on the endocytosis of transferrin. Quantum dots are labeled for transferrin and endocytosis of transferrin in HeLa cells is observed under the normal state, iron overloading, and an iron-deficient state. In these three states, the fluorescence undergoes a gradual process of first dark, then light, and finally dark, indicating the endocytosis of transferrin. The fluorescence intensity analysis shows that a platform emerges when fluorescence changes to a certain degree in the three states. Experienced a same period of time after platform, the fluorescence strength of cells in the normal state is 1.2 times the first value, and the iron-deficiency state is 1.4 times, but the iron overloading state was 0.85 times. We also find that the average fluorescence intensity in cells detected by the spectrophotometer in the iron-deficiency state is almost 7 times than that in a high iron state. All this proves that iron overloading would slow the process, but iron deficiency would accelerate endocytosis. We advance a direct observational method that may contribute to further study of the relationship of iron and transferrin.

Here a new method for high-sensitivity quantum dot (QD)-based fluorescence resonance energy transfer (FRET) bioanalysis was developed. In this method, capillary electrophoresis (CE) with fluorescence detection was applied. The FRET system consisted of water-soluble 532-nm emitting CdTe QDs donor and 632-nm emitting CdSe/ZnS QDs acceptor which were covalently conjugated with mouse IgG and goat anti-mouse IgG, respectively. The bio-affinity between antigen and antibody brought two kinds of QDs close enough to make the FRET happen between them. In the CE experiments, highly efficient separation of donor-acceptor immunocomplexes was obtained, and the process of FRET was monitored. Results showed that FRET efficiency obtained by CE (38.56-69.58%) improved substantially in comparison with that obtained by ensemble measurement (12.77-52.37%). The high efficient separation of donor-acceptor immunocomplexes and the possible conformation change of antigen and antibody, contributes to the lower analysis uncertainty (variance) and higher FRET efficiency obtained in CE and consequentially, this makes the analysis of FRET more sensitive. This novel CE-based technique can be easily extended to other FRET system based on QDs and may have potential application in the study of biomolecule conformation change., (Copyright 2009 Elsevier B.V. All rights reserved.)

Quantum dots (QDs) are widely used in the life sciences because of their novel physicochemical properties. However, the cytotoxity of these nonoparticles have attracted great attention recently because this has not been well resolved. Four probes were synthesized by chemical coupling and protein denaturation with CdSeZnS, CdTe QDs, and transferrin. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and capillary electrophoresis were used to verify the conjugation of these luminescent probes. The cytotoxicity of these four luminescent probes and the original QDs were evaluated in HeLa cells. The results showed that over 92% of HeLa cells were still alive after being exposed to 3.2-microM CdSeZnS QDs capped with denatured transferrin for 72 h. Furthermore, while the probe preparation was very simple, the photoluminescence quantum yield of this probe was 7% higher than the original CdSeZnS QDs. This provides a new way for exploiting QD probes with low cytotoxicity, which will expand applications of nanocomposite assembly in biolabeling and imaging.

This paper describes a highly efficient method for size determination of water-soluble CdSe/ZnS core-shell quantum dots (QDs) by capillary electrophoresis (CE) using polymer additive as sieving medium. The influence of some factors, such as kinds and concentrations of the sieving medium, pH, concentrations of the background electrolyte (BGE) and applied voltage, on the separation of QDs was investigated. Under the optimal separation conditions, four different sized QDs were successfully separated, and the relative standard deviation (RSD) of the migration times for these QDs was below 1.013%. In addition, an equation was fit by taking into account the correlation existing between the electrophoretic mobilities and the sizes of a set of QDs. The feasibility of this equation to measure the sizes of other QDs was confirmed by comparison with the sizes obtained by transmission electron microscopy (TEM) experiment. This work offers a novel method for size determination of QDs, and provides an important reference on the study of QDs based on CE.

Multiplex optical coding carriers for biological assays have been achieved by coating silica colloidal crystals beads with quantum dots, which provided high stability, large capacity and simplicity for practical application.

Quantum dot (QD) solubilization, conjugation with biomolecules, column purification, and labeling of human HepG2 cells with transferrin-QD (Tf-QD) conjugates are reported in detail in this article. Water-soluble QDs (WQDs) were obtained using sodium thiolycolate to replace the surface ligand tri-n-octylphosphine oxide (TOPO) on the surface of oil-soluble QDs, and Tf-QD conjugates were produced by coupling Tf to WQD. The resulting Tf-QDs were characterized by UV and luminescence spectrophotometry and purified by Sephadex column. The results indicate that Tf has been conjugated to QD successfully. Based on transferrin/transferrin-receptor-mediated delivery system, the Tf-QD conjugates were used to label human HepG2 cells. After a short incubation, the QDs were mainly localized to the membrane of cells. After 12-h incubation, QDs appear mainly in the cytoplasm portion. However, QDs were not found in the nucleus of the cells. Furthermore, the fluorescence intensity of QDs in the cells reduces gradually over time, and fluorescence cannot be observed after 10 days. However, the growth of the labeled cells was not markedly affected by the toxicity of QDs, and they are alive for 10 days. These results can be used for further application of QDs in bioscience.

Mouse anti-human CD71 monoclonal antibody (anti-CD71) was conjugated with red quantum dots (QDs; 5.3 nm, emission wavelength lambda(em) = 614 nm) and used to label HeLa cells successfully. Then green QD-labeled goat anti-mouse immunoglobulin G (IgG; the size of the green QDs was 2.2 nm; lambda(em) = 544 nm) was added to bind the red-QD-conjugated anti-CD71 on the cell surface by immunoreactions. Such interaction between anti-CD71 and IgG lasted 4 min and was observed from the fluorescence spectra: the fluorescence intensity of the "red" peak at 614 nm increased by 32%; meanwhile that of the "green" one at 544 nm decreased by 55%. The ratio of the fluorescence intensities (I(544 nm)/I(614 nm)) decreased from 0.5 to 0.2. The fluorescence spectra as well as cell imaging showed that fluorescence resonance energy transfer took place between these two kinds of QDs on the HeLa cells through interactions between the primary antibody and the secondary antibody.

The resonance energy transfer between chemiluminescence donor (luminol-H2O2 system) and quantum dots (QDs, emission at 593 nm) acceptors (CRET) was investigated. The resonance energy transfer efficiencies were compared while the oil soluble QDs, water soluble QDs (modified with thioglycolate) and QD-HRP conjugates were used as acceptor. The fluorescence of QD can be observed in the three cases, indicating that the CRET occurs while QD acceptor in different status was used. The highest CRET efficiency (10.7%) was obtained in the case of oil soluble QDs, and the lowest CRET efficiency (2.7%) was observed in the QD-HRP conjugates case. This result is coincident with the quantum yields of the acceptors (18.3% and 0.4%). The same result was observed in another similar set of experiment, in which the amphiphilic polymer modified QDs (emission at 675 nm) were used. It suggests that the quantum yield of the QD in different status is the crucial factor to the CRET efficiency. Furthermore, the multiplexed CRET between luminol donor and three different sizes QD acceptors was observed simultaneously. This work will offer useful support for improving the CRET studies based on quantum dots.

CdTe quantum dots (QDs) were synthesized in aqueous solution with 3-mercaptopropionic acid (MPA) as the stabilizer. The photoluminescence (PL) of CdTe QDs (3.5nm) is found to be temperature-dependent: as the temperature arising from 278K to 323K, the PL intensity declines to 50.2% of its original and PL emission peak shows obvious red-shift ( approximately 7nm). After modification of the QDs surface with denatured ovalbumin, the PL is more temperature-insensitive than before. The PL intensity retains more than 70% of its original and the emission peak shows less red-shift ( approximately 2nm). Moreover, it is found that the PL intensity and wavelength of denatured ovalbumin coated CdTe QDs are reversible during heating (323K)-cooling (278K) cycles. All the studies provide an important theoretical basis for searching temperature-insensitive bioprobes.

Transferrin and mouse anti-human CD71 monoclonal antibody were respectively conjugated covalently to the core/shell CdSe/ZnS quantum dots with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydrocylsulfo-succinimide (Sulfo-NHS). The conjugation worked well and the bioactivities of these macromolecules still remained, which was verified by column filtration, sodium dodecyl sulfate polyacrylamide gel electrophoresis, absorption spectra, fluorescence spectra, and circular dichroism spectrometry. Thus, these two kinds of quantum dot conjugates were used to recognize the tumor cells involved. In case of pseudo positivity, FITC-labeling secondary antibody IgG was used, and the results showed that as-prepared fluorescent quantum dot bioprobes were highly specific to tumor cells., ((c) 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007.)

Different diameter CdSe/ZnS semiconductor nanocrystals (average diameter: from approximately 3.5 to approximately 20 nm), quantum dots (QDs) were synthesized by changing the nucleation time, using organometallic reagents. These quantum dots possess narrow and symmetrical fluorescent emissions. The emission wavelengths of these composite dots span most of the visible spectrum from 500 through 700 nm. Furthermore, it is found that the quantum dots with an emission at approximately 590 nm, tend to have a good quantum yield (such as Phi(590)=43.5%). While the emission wavelength of prepared CdSe/ZnS QDs shifts toward blue or red from 590 nm, the quantum yield tends to decrease. After that, optical encoding of microbeads with these quantum dots was carried out, and the spectra of encoded beads were identified. The result indicates that, to identify the encoded beads with different emission wavelengths and emission intensities, it is needed to acquire and differentiate the spectra of beads. After immobilized with human IgG, the encoded beads were used to detect the corresponding antibody in solution. The result indicates that the encoded beads can detect the antibody signal effectively. And the effective detection range of the antibody is about 2-15 microM.

A multi-wall carbon nanotubes (MWNTs)-quantum dots (QDs) composite-modified glassy carbon electrode (GCE) was prepared. The complex was characterized by transmission electron microscopy (TEM). The electrochemical behavior of levodopa at MWNTs and QDs-modified GCEs (MWNTs-QDs/GCE) was studied by cyclic voltammetry (CV) and chronocoulometry (CC). It was found that its electrochemical behavior was a two-charge-two-proton process. The modified electrode had high electrocatalytic activity for levodopa with a standard heterogeneous rate constant of 0.595 cm s(-1), which was greatly increased compared with the values for bare GCE and individual MWNTs modified GCE. The better electrocatalytic activity for levodopa at MWNTs-QDs/GCE may due to a synergistic effect between MWNTs and QDs. This result provides a novel way to promote research on biomicromolecules at nano-dimensions.

CdTe quantum dots (QDs) were synthesized in aqueous solution with 3-mercaptopropionic acid as the stabilizer. Chemically reduced bovine serum albumin (BSA) was used to modify the surface of the QDs. Experimental results showed that the denatured BSA (dBSA) could be effectively conjugated to the surface of CdTe QDs. Column chromatography was used to purify the conjugates and determine the optimal ratio of dBSA to QDs. Further experimental results showed that the conjugation of QDs by dBSA efficiently improved the photoluminescence quantum yield, the chemical stability of QDs and their stability against photobleaching. A facile and sensitive method for determination of silver(I) ions was proposed based on the fluorescence quenching of the dBSA-QDs. Under the optimal conditions, the relative fluorescence intensity decreased linearly with the concentration of the silver(I) ions in the range 0.08-10.66 microM. The detection limit was 0.01 microM. This study provides a new method for the detection of metal cations.

Multicolor encoded beads were achieved by incorporating two color core-shell quantum dots (QDs) (CdSe/ZnS) to commercial polystyrene (PS) beads. By controlling the concentration ratios of the two quantum dots (QDs) in doping solutions, a series of codes with different intensity ratios were obtained. Based on the multiple encoded carboxylic modified polystyrene beads, fluorescent dyes labeled antibodies were distinguished successfully on the beads' surface. It suggests that the encoded beads from this method have the practicability in biological applications and chemical analysis.

Water-soluble quantum dots (QDs) were used to label goat anti-human immunoglobulin antibodies (Abs), and the labeling process was characterized by column purification. The QDs obtained in organic solvent were modified with mercaptoacetic acid (MAA) and became water-soluble. These water-soluble QDs were linked to the antibodies using the coupling reagents ethyl-3-(dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The linking process was shown to be effective by ultra-filter centrifugation and column purification. After comparing the quantities of Abs and water-soluble QDs involved in the linking reaction via column purification, it was found that a molar Abs:QD ratio of >1.2 resulted in most of the water-soluble QDs becoming covalently linked to the Abs. The circular dichroism (CD) spectra of Abs and QD-Ab conjugates were very similar to each other, indicating that the secondary structure of Abs remained largely intact after the conjugation. Finally, antigen (Ag)-antibody (Ab) recognition reactions perfomed on the surface of a glass slide showed that the conjugate retained the activity of Abs. This work lends support to the idea of linking biomolecules to QDs, and thus should aid the application of QDs to the life sciences.

A novel multiplex analysis technology based on quantum dot (QD) optical encoded beads was studied. Carboxyl functionalized polystyrene beads, about 100 microm in size, were precisely encoded by the various ratios of two types of QDs whose emission wavelengths are 576 and 628 nm, respectively. Then the different encoded beads were covalently immobilized with different probes in the existing of sulfo-NHS and 1-[3-(Dimethylamino) propyl]-3-ethylcarbodiimide methiodide, and the probe density could reach to 3.1 mmol/g. These probe-linked encoded beads were used to detect the target DNA sequences in complex DNA solution by hybridization. Hybridization was visualized using fluorescein isothiocynate-labeled DNA sequences. The results show that the QDs and target signals can be obviously identified from a single-bead-level spectrum. This technology can detect DNA targets effectively with a detection limit of 0.2 microg/mL in complex solution.

Novel -COOH modified polystyrene beads were prepared by sulfonation grafting, and the surface area and pore volume are greatly improved in comparison with the swelling-treated beads. The optimization coating time is 4 h, and the corresponding -COOH content is approximately 2.1 mmol/g. The scanning electron microscope results show that the silica particles deposited on the beads and formed a silica shell that decreases the leakage of quantum dots (QDs) preferably and improves the bar code stability greatly. The anti-photobleaching of silica-coated beads was studied systemically, and the results show that the half-decay time (t1/2) of the coated beads increases to 537 s--seven times longer than that of the uncoated ones. Further DNA probe hybridization experiments indicated that the coding signal and target signal can be detected simultaneously and that the assays based on these probe-conjugated silica/QD/polystyrene beads have good specificity and sensitivity that can detect a concentration as low as 0.01 microg/ml target DNA in denatured calf thymus DNA solution, indicating that it is feasible to use this kind of bead for multiplex analysis.

Semiconductor CdS fluorescent quantum dots (QDs) have been widely studied for their excellent optical and electrical properties. There are many mature preparation methods of CdS QDs have been developed. Among these, the ionizing radiation preparation method is generally easy to implement under normal temperature and pressure, it is also safe and effective, and environmentally friendly. The associated ionizing radiation preparation methods for CdS QDs, such as γ-ray radiation preparation and electron beam radiation preparation, are reviewed to provide a reference for the preparation of other fluorescent QDs. The applications of CdS QDs in the fields of photocatalysts, biomedicine, and solar cells, in addition to applications in the field of analysis, are reviewed. In light of the current research status of CdS QDs, the application prospects and development directions of CdS QDs are discussed.