Luminescent gelatin nanospheres by encapsulating CdSe quantum dots

Quantum dots (QDs) have been encapsulated within gelatin nanoparticles (GNPs), which gives GNPs fluorescent properties and improves the biocompatibility of QDs. Hydrophilic CdSe QDs were produced through thermodecomposition following the ligand‐exchange method, and were then encapsulated in GNPs. The results of high‐resolution transmission electron microscopy and transmission electron microscopy show that CdSe QDs and QDs‐encapsulated GNPs (QDs‐GNPs) have average diameters of 5 ± 1 and 150 ± 10 nm, respectively. Results of both high‐resolution transmission electron microscopy and confocal laser scanning microscopy indicate that CdSe QDs are successfully encapsulated within GNPs. The QDs‐GNPs have distinctive fluorescent properties with maximum emission at 654 nm, with a 24 nm red‐shift comapred with hydrophilic mercaptoundecanoic acid (MUA)‐modified QDs. In addition, an in vitro cytotoxicity test shows that QDs‐GNPs do not have any toxic effect on cells. It is expected that QDs‐GNPs might be an excellent candidate as a contrast agent in bio‐imaging. Copyright © 2013 John Wiley & Sons, Ltd.     

In situ detection of salicylic acid binding sites in plant tissues

The determination of hormone‐binding sites in plants is essential in understanding the mechanisms behind hormone function. Salicylic acid (SA) is an important plant hormone that regulates responses to biotic and abiotic stresses. In order to label SA‐binding sites in plant tissues, a quantum dots (QDs) probe functionalized with a SA moiety was successfully synthesized by coupling CdSe QDs capped with 3‐mercaptopropionic acid (MPA) to 4‐amino‐2‐hydroxybenzoic acid (PAS), using 1‐ethyl‐3‐(3‐dimethyllaminopropyl) carbodiimide (EDC) as the coupling agent. The probe was then characterized by dynamic light scattering and transmission electron microscopy, as well as UV/vis and fluorescence spectrophotometry. The results confirmed the successful conjugation of PAS to CdSe QDs and revealed that the conjugates maintained the properties of the original QDs, with small core diameters and adequate dispersal in solution. The PAS–CdSe QDs were used to detect SA‐binding sites in mung bean and Arabidopsis thaliana seedlings in vitro and in vivo. The PAS–CdSe QDs were effectively transported into plant tissues and specifically bound to SA receptors in vivo. In addition, the effects of the PAS–CdSe QDs on cytosolic Ca²⁺ levels in the tips of A. thaliana seedlings were investigated. Both SA and PAS–CdSe QDs had similar effects on the trend in cytosolic‐free Ca²⁺ concentrations, suggesting that the PAS–CdSe QDs maintained the bioactivity of SA. To summarize, PAS–CdSe QDs have high potential as a fluorescent probe for the in vitro/in vivo labeling and imaging of SA receptors in plants. Copyright © 2014 John Wiley & Sons, Ltd.     

Sodium 4‐mercaptophenolate capped CdSe/ZnS quantum dots as a fluorescent probe for pH detection in acidic aqueous media

Development of the fluorescent pH detection method is promising due to the sensitivity, easy operation, and low‐cost, etc. However, traditional organic fluorophores have still some disadvantages such as the tedious preparation and purification as well as low photostability and water solubility, which limits the rapid detection application. Semiconductor quantum dots (QDs) have recently risen to prominence as an alternative for organic fluorophores in fluorescence analysis by virtue of their convenient synthesis and superior optical properties. In this study, we report on sodium 4‐mercaptophenolate functionalized CdSe/ZnS QDs (denoted as ^?OPhS‐QDs), which can serve as a selective “on–off” fluorescence probe for aqueous media pH. ^?OPhS‐QDs exhibit strong fluorescence in near neutral medium. As a Lewis organic base, ^?OPhS‐ moieties on QDs surface easily binds to proton under acidic conditions to yield 4‐mercaptophenol capped QDs (i.e. HOPhS‐QDs), which acts as an efficient hole trapper. As a result, the QDs photoluminescence (PL) is switched off. Under optimal conditions, the present probe exhibits a good linear relationship between fluorescence response and pH values in the pH range 3.0–5.2. Furthermore, the present probe exhibits a high selectivity for proton over other common cations and has been successfully used for pH detection in real water samples.     

Biokinetics and <Emphasis Type="Italic">In Vivo</Emphasis> Distribution Behaviours of Silica-Coated Cadmium Selenide Quantum Dots

Recently, quantum dots derived from trace elements like cadmium and selenium have attracted widespread interest in biology and medicine. They are rapidly being used as novel tools for both diagnostic and therapeutic purposes. In this report, we evaluated the distribution of silica-coated cadmium selenide (CdSe) quantum dots (QDs) following intravenous injection into male Swiss albino mice as a model system for determining tissue localization using in vivo fluorescence and ex vivo elemental analysis by inductively coupled plasma optical emission spectroscopy (ICP-OES). Trioctylphosphine oxide-capped CdSe quantum dots were synthesized and rendered water soluble by overcoating with silica, using aminopropyl silane (APS) as silica precursor. ICP-OES was used to measure the cadmium content to indicate the concentration of QDs in blood, organs and excretion samples collected at predetermined time intervals. Meanwhile, the distribution and aggregation state of QDs in tissues were also investigated in cryosections of the organs by fluorescence microscopy. We have demonstrated that the liver and kidney were the main target organs for QDs. Our systematic investigation clearly shows that most of the QDs were metabolized in the liver and excreted via faeces and urine in vivo. A fraction of free QDs, maintaining their original form, could be filtered by glomerular capillaries and excreted via urine as small molecules within 5 days.     

Direct and indirect immunolabelling of HeLa cells with quantum dots

With excellent optical properties, quantum dots (QDs) have been made as attractive molecular probes for labelling cells in biological research. In this study high‐quality CdSe QDs prepared in a paraffin–oleic acid system were used as fluorescent labels in direct and indirect detection of carcinoembryonic antigen (CEA), a cancer marker expressed on the surface of HeLa cells. The primary antibody (Ab) (rabbit anti‐CEA8) and secondary Ab (goat anti‐rabbit IgG) were covalently linked to carboxyl‐functioned CdSe QDs, and both the QDs–antibody and QDs–IgG probes were successfully used to label HeLa cells. The present study demonstrates the practicability of CdSe QDs as an attractive type of fluorescent labels for biological applications such as protein probes and cell imaging. Copyright © 2008 John Wiley & Sons, Ltd.     

Study on the interaction between 2‐mercaptoethanol,dimercaprol and CdSe quantum dots

The interactions between 2‐mercaptoethanol, dimercaprol and CdSe quantum dots (QDs) in organic media have been investigated by spectral methods. The results showed that the fluorescence (FL) emission of CdSe QDs gradually decreased, with a slight red‐shift, after adding thiols to CdSe QDs solutions. With the increase of the concentrations of thiols, the resonance light scattering (RLS) signal of CdSe QDs had been strongly enhanced in the wavelength range 300–500 nm, which was confirmed by the formation of larger CdSe QDs particles. The effect of thiols on the FL emission of CdSe QDs could be described by a Stern–Volmer‐type equation with the concentration ranges 1.0 × 10^–6–7.5 × 10^–4 mol/L for 2‐mercaptoethanol and 1.0 × 10^–7–2.5 × 10^–5 mol/L for dimercaprol. The possible mechanism of the interaction was proposed according to the results of UV‐vis absorption and micro‐Raman spectroscopy. The results indicated that FL quenching was mainly attributable to the exchange of the QDs surface molecules. Copyright © 2008 John Wiley & Sons, Ltd.     

Photoluminescence properties of hybrid SiO2‐coated CdTe/CdSe quantum dots

Hybrid SiO₂‐coated CdTe/CdSe quantum dots (QDs) were prepared using CdTe/CdSe QDs prepared by hydrothermal synthesis. A CdSe interlayer made CdTe/CdSe cores with unique type II heterostructures. The hybrid SiO₂‐coated CdTe/CdSe QDs revealed excellent photoluminescence (PL) properties compared with hybrid SiO₂‐coated CdTe QDs. Because of the existence of spatial separations of carriers in the type II CdTe/CdSe core/shell QDs, the hybrid QDs had a relatively extended PL lifetime and high stability in phosphate‐buffered saline buffer solutions. This is ascribed to the unique components and stable surface state of hybrid SiO₂‐coated CdTe/CdSe QDs. During the stabilization test in phosphate‐buffered saline buffer solutions, both static and dynamic quenching occurred. The quenching mechanism of the hybrid QDs was not suited with the Stern–Volmer equation. However, the relative stable surface of CdTe/CdSe QDs resulted in lower degradation and relative high PL quantum yields compared with hybrid SiO₂‐coated CdTe QDs. As a result, hybrid SiO₂‐coated CdTe/CdSe QDs can be used in bioapplications. Copyright © 2013 John Wiley & Sons, Ltd.     

Fluorescence sensing of nitric oxide in aqueous solution by triethanolamine‐modified CdSe quantum dots

The water‐soluble luminescent CdSe quantum dots were prepared by ligand exchange with triethanolamine (TEA). Oxygen can reversibly enhance the fluorescence of the synthesized quantum dots (TEA‐CdSe‐QDs) in aqueous solution. Nitric oxide radical (NO) can react easily with dissolved oxygen in water and was found to have a significant quenching effect on the fluorescence of the TEA‐CdSe‐QDs. The fluorescence responses were concentration‐dependent and can be well described by the typical Stern–Volmer equation. A good linear relationship (R² = 0.9963) was observed over the range 5.92 × 10^?7 to 1.85 × 10^?5 mol/L nitric oxide. Above this concentration was a second linear region ranging from 2.12 × 10^?5 to 1.12 × 10^?4 mol/L NO with a gentler slope. The detection limit, calculated following the 3σ IUPAC criteria, was 3.02 × 10^?7 mol/L. The interference effect of some common interferents such as nitrite (NO₂^?), nitrate (NO₃^?), glucose and l ‐ascorbic acid on the detection of NO was negligible for the proposed system, demonstrating the potential utility of this probe for the detection of NO in biological systems. The possible mechanism was also discussed. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and characterization of cadmium selenide quantum dots doped by europium and investigation of their chemiluminescence properties and antibacterial activities

Nanoparticles of cadmium selenide (CdSe) doped with europium, were synthesized as stabilizing agents using thioglycolic acid ligand. This method is based on the enhancing effect of CdSe quantum dots (QDs) doped with europium on chemiluminescence (CL) emission. This emission was generated by mixing CdSe QDs with manganese (II), iron (II) and chrome (II) sulfates as catalysts in the presence of hydrogen peroxide (H₂O₂). The structural characteristics and morphology of these nanoparticles were investigated by scanning electron microscopy, Fourier transform infrared spectroscopy, ultraviolet–visible absorption spectroscopy, X‐ray pattern and dynamic light scattering methods. The CdSe QDs doped with europium were used as the sensitizer in a luminol?hydrogen peroxide CL system. The sensitized CdSe QDs were analyzed for antibacterial activity against Gram‐positive or Gram‐negative bacteria. The results showed that the CdSe QDs are effective against all the studied bacteria, effectiveness was especially higher for Bacillus subtilis.     

Comprehensive study of interaction between biocompatible PEG‐InP/ZnS QDs and bovine serum albumin

Polyethylene glycol (PEG) surface modified biocompatible InP/ZnS quantum dots (QDs) act as a potential alternative for conventional carcinogenic cadmium‐based quantum dots for in vivo and in vitro studies. Comprehensively, we studied the interaction between a model protein bovine serum albumin (BSA) and PEGylated toxic free InP/ZnS QDs using various spectroscopic tools such as absorption, fluorescence quenching, time resolved and synchronous fluorescence spectroscopic measurements. These studies principally show that tryptophan (Trp) residues of BSA have preferable binding affinity towards PEG‐InP/ZnS QDs surface and a blue shift in Trp fluorescence emission is a signature of conformational changes in its hydrophobic microenvironment. Photoluminescence (PL) intensity of Trp is quenched by ground state complex formation (static quenching) at room temperature. However, InP/ZnS@BSA conjugates become unstable with increasing temperature and PL intensity of Trp is quenched via dynamic quenching by PEG‐InP/ZnS QDs. Experimentally determined thermodynamic parameters for these conjugates have shown spontaneity, entropy driven and exothermic nature of bio‐conjugation. The calculated binding affinity (n ? 1, Hill coefficient) suggest that the affinity of InP/ZnS QDs for a BSA protein is not dependent on whether or not other BSA proteins are already bound to the QD surface. Energy transfer efficiency (E), Trp residue to InP/ZnS QDs distances and energy transfer rate (k_T) were all obtained from FÖrster resonance energy.     

Near‐Infrared,Heavy Metal‐Free Colloidal “Giant” Core/Shell Quantum Dots

“Giant” core/shell quantum dots (g‐QDs) are a promising class of materials for future optoelectronic technologies due to their superior chemical‐ and photostability compared to bare QDs and core/thin shell QDs. However, inadequate light absorption in the visible and near‐infrared (NIR) region and frequent use of toxic heavy metals (e.g., Cd and Pb) are still major challenges for most g‐QDs (e.g., CdSe/CdS) synthesized to date. The synthesis of NIR, heavy metal‐free, Zn‐treated spherical CuInSe₂/CuInS₂ g‐QDs is reported using the sequential cation exchange method. These g‐QDs exhibit tunable NIR optical absorption and photoluminescence (PL) properties. Transient fluorescence spectroscopy shows prolonged lifetime with increasing shell thickness, indicating the formation of quasi type‐II band alignment, which is further confirmed by simulations. As a proof‐of‐concept, as‐synthesized g‐QDs are used to sensitize TiO₂ as a photoanode in a photoelectrochemical (PEC) cell, demonstrating an efficient and stable PEC system. These results pave the way toward synthesizing NIR heavy metal‐free g‐QDs, which are very promising components of future optoelectronic technologies.     

Application of quantum dots as probes for correlative fluorescence, conventional, and energy-filtered transmission electron microscopy.

Luminescent semiconductor quantum dots (QDs) are a new class of fluorescent label with wide-ranging applications for cell imaging. The electron density and elemental composition of these materials permit the extension of their use as probes in conventional electron microscopy (TEM) and energy-filtered TEM (EFTEM). Here we illustrate the feasibility of using streptavidin-conjugated QDs as TEM tags by labeling a nuclear protein on cell sections and obtaining correlative fluorescence and TEM data. We also show that QD probes can be employed in conjunction with immunogold for co-localization of proteins at the ultrastructural level. Furthermore, by obtaining cadmium elemental maps of CdSe/ZnS QDs distributed on a nuclear structure, we demonstrate the potential of QDs for co-localization of multiple proteins when used in combination with EFTEM.     

Metabolic alteration of Tetrahymena thermophila exposed to CdSe/ZnS quantum dots to respond to oxidative stress and lipid damage

CdSe/ZnS Quantum dots (QDs) are possibly released to surface water due to their extensive application. Based on their high reactivity, even small amounts of toxicant QDs will disturb water microbes and pose a risk to aquatic ecology. Here, we evaluated CdSe/ZnS QDs toxicity to Tetrahymena thermophila (T. thermophila), a model organism of the aquatic environment, and performed metabolomics experiments. Before the omics experiment was conducted, QDs were found to induce inhibition of cell proliferation, and reactive oxygen species (ROS) production along with Propidium iodide labeled cell membrane damage indicated oxidative stress stimulation. In addition, mitochondrial ultrastructure alteration of T. thermophila was also confirmed by Transmission Electron Microscope results after 48 h of exposure to QDs. Further results of metabolomics detection showed that 0.1 μg/mL QDs could disturb cell physiological and metabolic metabolism characterized by 18 significant metabolite changes, of which twelve metabolites improved and three decreased significantly compared to the control. Kyoto Encyclopedia of Genes and Genomes analysis showed that these metabolites were involved in the ATP-binding cassette transporter and purine metabolism pathways, both of which respond to ROS-induced cell membrane damage. In addition, purine metabolism weakness might also reflect mitochondrial dysfunction associated with energy metabolism and transport abnormalities. This research provides deep insight into the potential risks of quantum dots in aquatic ecosystems.     

Interaction of β‐cyclodextrin‐capped CdSe quantum dots with inorganic anions and cations

A facile method was developed for the preparation of water soluble β‐Cyclodextrin (β‐CD)‐modified CdSe quantum dots (QDs) (β‐CD‐QDs) by directly replacing the oleic acid ligands on the QDs surface with β‐CD in an alkaline aqueous solution. The as‐prepared QDs show good stability in aqueous solution for several months. Oxoanions, including phosphoric acid ion, sulphite acid ion and carbonic acid ion, affect the fluorescence of β‐CD‐QDs. Among them, H₂PO₄^– exhibited the largest quenching effect. For the polyprotic acids (HO)₃AO, the effect of acidic anions on the fluorescence of β‐CD‐QDs was in the order: monoanion (HO)₂AO₂^– > dianion (HO)AO₃^2– >> trianion AO₄^3–. After photoactivation for several days in the presence of anions at alkaline pH, the β‐CD‐QDs exhibited strong fluorescence emission. The effect of various heavy and transition metal ions on the fluorescence properties of the β‐CD‐QDs was investigated further. It was found that Ag⁺, Hg²⁺ and Co²⁺ have significant quenching effect on the fluorescence of the β‐CD‐QDs. The Stern–Volmer quenching constants increased in the order: Hg²⁺ < Co²⁺ <Ag⁺. The adsorption model of metal ions on β‐CD‐QDs was explored. Copyright © 2011 John Wiley & Sons, Ltd.     

CdSe量子点荧光猝灭法测定尿嘧啶

以CdSe量子点为荧光探针,基于荧光猝灭法对碱基尿嘧啶进行了定量检测,考察了缓冲液体系、反应时间、量子点浓度等多种因素的影响. 实验结果表明,在pH 7.4的0.2 mol/L Na₂HPO₄-NaH₂PO₄缓冲液中,反应时间为60 min,尿嘧啶浓度为10^-6～10^-4mol/L范围时,其线性回归方程为F₀/F =0.992+3.35×10⁴Q (mol/L),检测限为3.23×10^-6 mol/L(即0.36μg/ml). 该方法检测范围宽,灵敏度高,为尿嘧啶的测定提供了新的方法.     

Synthesis and characterisation of quantum dots coupled to mycolic acids as a water-soluble fluorescent probe for potential lateral flow detection of antibodies and diagnosis of tuberculosis

This work explores the potential use of cadmium-based quantum dots (QDs) coupled to mycolic acids (MAs) as a fluorescent probe to detect anti-MA antibodies which are biomarkers for tuberculosis (TB). The use of free MAs as antigens for the serodiagnosis of TB is known but has not been developed into a point of care test. This study focuses on the synthesis, solubility, and lateral flow of QDs coupled to MAs. Water-soluble CdSe/ZnS QDs capped with l -cysteine were synthesised and covalently coupled to MAs via amide linkages to form a water-soluble fluorescent probe: MA-CdSe/ZnS QDs. The MA-CdSe/ZnS QDs showed broad absorption bands and coupling, confirmed by the presence of amide bonds in the Fourier-transform infrared (FTIR) spectrum, resulting in a blue shift in fluorescence. Powder X-ray diffraction (XRD) revealed a shift and increase in the number of peaks for MA-CdSe/ZnS QDs relative to the L-cys-CdSe/ZnS QDs, suggesting that coupling changed the crystal structure. The average particle size of MA-CdSe/ZnS QDs was ~3.0 nm. Visual paper-based lateral flow of MA-CdSe/ZnS QDs was achieved on strips of nitrocellulose membrane with both water and membrane blocking solution eluents. The highly fluorescent MA-CdSe/ZnS QDs showed good water solubility and lateral flow, which are important properties for fluorescence sensing applications.     

Spontaneous emission of semiconductor quantum dots in inverse opal SiO2 photonic crystals at different temperatures

The photoluminescence (PL) characteristics of CdSe quantum dots (QDs) infiltrated into inverse opal SiO₂ photonic crystals (PCs) are systemically studied. The special porous structure of inverse opal PCs enhanced the thermal exchange rate between the CdSe QDs and their surrounding environment. Finally, inverse opal SiO₂ PCs suppressed the nonlinear PL enhancement of CdSe QDs in PCs excited by a continuum laser and effectively modulated the PL characteristics of CdSe QDs in PCs at high temperatures in comparison with that of CdSe QDs out of PCs. The final results are of benefit in further understanding the role of inverse opal PCs on the PL characteristics of QDs. Copyright © 2015 John Wiley & Sons, Ltd.     

High quantum yield and well‐dispersed quantum dots luminescent composite through sodium carboxymethyl starch

It is a challenging task to prepare well‐dispersed and highly luminescent quantum dots (QDs) powder and a new strategy is reported in this article. Sodium carboxymethyl starch (CMS‐Na) was employed in this work to prepare the QDs–starch composite. Ultraviolet (UV) light shows that the blank starches had no fluorescence, while the QDs‐starches were highly luminescent. Scanning electron microscopy (SEM) observation shows that the QDs–starch composite has the typical particle morphology with the diameter around 200 nm. Energy dispersive X‐ray spectroscopy (EDX) results show that there are intensive tellurium (Te) and cadmium (Cd) element signals. Combined fluorescent lifetime and steady‐state spectrometer show that the QDs–starch quantum yields (QYs) increase when the QDs loading increases from 1 × 10^?6 mol/g to 2 × 10^?6 mol/g, but when the loadings further increase, the QYs decrease slightly. For the red colour (λ_em = 660 nm) QDs, the QYs can reach to as high as 28.2%, and for the other colour QDs they can also have the QYs above 22%. Time‐resolved photobleaching experiments show that the fluorescent QDs–starch composite has a half‐decay time of 40.23 s. These results indicate that the CMS‐Na is a promising QDs dispersant to obtain high QY QD composites.     

Quantum Dots based on Indium Phosphide (InP): the Effect of Chemical Modifications of the Organic Shell on Interaction with Cultured Cells of Various Origins

CdSe and CdTe-based semiconductor fluorescent nanocrystals, also called quantum dots (QDs), attract the attention of biologists due to their wide range of emission in a visible light interval, high fluorescence quantum yield and photostability. However, their application is limited because of possible toxicity of cadmium. Indeed, there is a probability of metal leakage from QDs cores as a result of damage of both inorganic and organic layers of shells covering QDs. An alternative to cadmium QDs could be nanostructures having as a core, for example, non-toxical indium phosphide (InP), also emitting in the visible region of the spectrum. At present, there is few works on the use of these particles in biology. In this study, a comparative analysis of the spectral-luminescent properties of two InP/ZnS-QDs samples coated with PEG carrying- COOH or -NH₂ functional groups was performed. The obtained data were compared with the characteristics of CdSe/ZnS-QDs coated with PEG. The photophysical properties of all QDs in aqueous solution corresponded to the information claimed by manufacturers, but the fluorescence quantum yield of InP-based nanoparticles was found to be lower than that of CdSe-QDs. We also show that the photoluminescence of all types of QDs at pH 4.0 was lower than at pH 7.4, while the decrease in fluorescence intensity was minimal in the case of QDs-PEG-COOH. Studying the uptake of all three types of QDs by J774 macrophages, we found that the fluorescence spectra of internalized QDs do not change in comparison with those in solution. All three types of QDs after 24 hours of incubation were accumulated in the cells, but while QDs-NH₂ and QDs without reactive groups were detected mainly in vesicular-like discrete structures, the QDs-COOH were diffusely distributed throughout the cytoplasm. This fact indicates different mechanisms of interaction with cell membranes. In nonphagocytic HeLa cells all types of QDs behaved similarly, but the overall level of cells fluorescence was much lower. This may be due to both reduced nonspecific uptake and possible quenching of QDs fluorescence in acidic endolysosomes. Cytofluorimetric analysis of propidium iodide accumulation showed that after 24 hours incubation with all studied types of QDs as well as in control (no QDs), the proportion of dead HeLa cells did not exceed 10%. Thus, it has been demonstrated that non-toxic InP-based QDs can be used as an effective tool for biological research.     

Cu‐doped quantum dots: a new class of near‐infrared emitting fluorophores for bioanalysis and bioimaging

Transition metal ion‐doped quantum dots (QDs) exhibit unique optical and photophysical properties that offer significant advantages over undoped QDs, such as larger Stokes shift to avoid self‐absorption/energy transfer, longer excited‐state lifetimes, wider spectral window, and improved chemical and thermal stability. Among the doped QDs emitters, Cu is widely introduced into the doped QDs as novel, efficient, stable, and tunable optical materials that span a wide spectrum from blue to near‐infrared (NIR) light. Their unique physical and chemical characteristics enable the use of Cu‐doped QDs as NIR labels for bioanalysis and bioimaging. In this review, we discuss doping mechanisms and optical properties of Cu‐doped QDs that are capable of NIR emission. Applications of Cu‐doped QDs in in vitro biosensing and in in vivo bioimaging are highlighted. Moreover, a prospect of the future of Cu‐doped QDs for bioanalysis and bioimaging are also summarized.