Bright and Stable Yellow Quantum Dot Light-Emitting Diodes Through Core-Shell Nanostructure Engineering.

Solution-processed and efficient yellow quantum dot light-emitting diodes (QLEDs) are considered key optoelectronic devices for lighting, display, and signal indication. However, limited synthesis routes for yellow quantum dots (QDs), combined with inferior stress-relaxation of the core-shell interface, pose challenges to their commercialization. Herein, a nanostructure tailoring strategy for high-quality yellow CdZnSe/ZnSe/ZnS core/shell QDs using a "stepwise high-temperature nucleation-shell growth" method is introduced. The synthesized CdZnSe-based QDs effectively smoothed the release stress of the core-shell interface and revealed a near-unit photoluminescence quantum yield, with nonblinking behavior and matched energy level, which accelerated radiative recombination and charge injection balance for device operation. Consequently, the yellow CdZnSe-based QLEDs exhibited a peak external quantum efficiency of 23.7%, a maximum luminance of 686 050 cd m-2, and a current efficiency of 103.2 cd A-1, along with an operating half-lifetime of 428 523 h at 100 cd m-2. To the best of the knowledge, the luminance and operational stability of the device are found to be the highest values reported for yellow LEDs. Moreover, devices with electroluminescence (EL) peaks at 570-605 nm exhibited excellent EQEs, surpassing 20%. The work is expected to significantly push the development of RGBY-based display panels and white LEDs.

Development of a Dual Fluorescence Signal-Enhancement Immunosensor Based on Substrate Modification for Simultaneous Detection of Interleukin-6 and Procalcitonin.

High-sensitivity detection of biomarkers is of great significance to improve the accuracy of disease diagnosis and the rate of occult disease diagnosis. Using a substrate modification and two-color quantum dot (QD) nanobeads (QBs), we have developed a dual fluorescence signal-enhancement immunosensor for sensitive, simultaneous detection of interleukin 6 (IL-6) and procalcitonin (PCT) at low volumes (∼20 µL). First, the QBs compatible with QDs with different surface ligands were prepared by optimizing surfactants based on the microemulsion method. Through the use of a fluorescence-linked immunosorbent assay (FLISA), the feasibility of a dual signal-enhancement immunosensor was verified, and a 5-fold enhancement of fluorescence intensity was achieved after the directional coating of the antibodies on sulfhydryl functionalization (-SH) substrates and the preparation of QBs by using a polymer and silica double-protection method. Next, a simple polydimethylsiloxane (HS-PDMS) immunosensor with a low volume consumption was prepared. Under optimal conditions, we achieved the simultaneous detection of IL-6 and PCT with a linear range of 0.05-50 ng/mL, and the limit of detection (LOD) was 24 and 32 pg/mL, respectively. The result is comparable to two-color QBs-FLISA with a sulfhydryl microplate, even though only 20% of its volume was used. Thus, the dual fluorescence signal-enhancement HS-PDMS immunosensor offers the capability of early microvolume diagnosis of diseases, while the detection of inflammatory factors is clinically important for assisting disease diagnosis and determining disease progression.

Highly Sensitive, Stable InP Quantum Dot Fluorescent Probes for Quantitative Immunoassay Through Nanostructure Tailoring and Biotin-Streptavidin Coupling.

Nontoxic, highly sensitive InP quantum dot (QD) fluorescent immunoassay probes are promising biomedical detection modalities due to their unique properties. However, InP-based QDs are prone to surface oxidation, and the stability of InP QD-based probes in biocompatible environments remains a crucial challenge. Although the thick shell can provide some protection during the phase transfer process of hydrophobic QDs, the photoluminescence quantum yield (PLQY) is generally decreased because of the contradiction between lattice stress relaxation and thick shell growth. Herein, we developed thick-shell InP-based core/shell QDs by inserting a ZnSeS alloy layer. The ternary ZnSeS intermediate shell could effectively facilitate lattice stress relaxation and passivate the defect states. The synthesized InP/ZnSe/ZnSeS/ZnS core/alloy shell/shell QDs (CAS-InP QDs) with nanostructure tailoring revealed a larger size, high PLQY (90%), and high optical stability. After amphiphilic polymer encapsulation, the aqueous CAS-InP QDs presented almost constant fluorescence attenuation and stable PL intensity under different temperatures, UV radiation, and pH solutions. The CAS-InP QDs were excellent labels of the fluorescence-linked immunosorbent assay (FLISA) for detecting C-reactive protein (CRP). The biotin-streptavidin (Bio-SA) system was first introduced in the FLISA to further improve the sensitivity, and the CAS-InP QDs-based SA-Bio sandwich FLISA realized the detection of CRP with an impressive limit of detection (LOD) of 0.83 ng/mL. It is believed that the stable and sensitive InP QD fluorescent probes will drive the rapid development of future eco-friendly, cost-effective, and sensitive in vitro diagnostic kits.

Fabrication of CuInZnS/ZnS Quantum Dot Microbeads by a Two-Step Approach of Emulsification-Solvent Evaporation and Surfactant Substitution and Its Application for Quantitative Detection.

CuInS2 quantum dots (CIS QDs) are considered to be promising alternatives for Cd-based QDs in the fields of biology and medicine. However, high-quality hydrophobic CIS QDs are difficult to be transferred to water due to their 1-dodecylmercaptan (DDT) ligands. Therefore, the fluorescence and stability of the prepared aqueous CIS QDs is not enough to meet the requirement for sensitive detection. Here, as large as 13 nm CuInZnS/ZnS QDs with DDT ligands were first synthesized, and then, CuInZnS/ZnS microbeads (QBs) containing thousands of QDs were successfully fabricated by a two-step approach of emulsion-solvent evaporation and surfactant substitution. Through emulsion-solvent evaporation, the CuInZnS/ZnS QDs formed microbeads in the microemulsion with dodecyl trimethylammonium bromide (DTAB), and the Förster resonance energy transfer (FRET) has been effectively overcome. Then, CO-520 was introduced to substitute DTAB to improve the stability and water solubility. Lastly, the microbeads were coated with a SiO2 shell and carboxylated. Subsequently, the constructed QBs (∼210 nm) were used as labels in a fluorescence immunosorbent assay (FLISA) for quantitative detection of heart type fatty acid binding protein (H-FABP), and the limit of detection was 0.48 ng mL-1, which indicated a greatly improved detection sensitivity compared to that of the Cd-free QDs. The highly fluorescent and stable CuInZnS/ZnS QBs will have great application prospects in many biological fields.

Biomolecular Surface Functionalization and Stabilization Method to Fabricate Quantum Dots Nanobeads for Accurate Biosensing Detection.

The surface functionalization of quantum dots (QDs) is essential for their application as a label material in a biological field. Here, a protein surface functionalization approach was introduced to combine with silica encapsulation for the sustainable and stable synthesis of QDs nanobeads for biomarker detection. The formation of QDs nanobeads was achieved by multiple mercapto groups in bovine serum albumin (BSA) macromolecules as multidentate ligands to replace hydrophobic ligands on the surface of QDs and decompression. The resulting QDs nanobeads exhibited 20 times more photoluminescence than the corresponding hydrophobic QDs and presented excellent stability under physiological conditions due to the protection of BSA and silica. The nanobeads served as a robust signal-generating reagent to construct the lateral flow immunoassay (LFIA) biosensor for the detection of glycosylated hemoglobin (HbA1c). The concentration of HbA1c was determined within 10 min with high specificity using only 60 µL of whole blood samples collected clinically. The nanobeads-based LFIA biosensor exhibited linear detection of HbA1c from 4.2% to 13.6%. The accuracy and stability of this approach in clinical utility was demonstrated by the detection of HbA1c after a long-term storage of test strips. This protein surface modification technology provides a new way for improving the biological properties of QDs in clinical diagnosis.

Bulk-like ZnSe Quantum Dots Enabling Efficient Ultranarrow Blue Light-Emitting Diodes.

Blue-emitting heavy-metal free QDs simultaneously exhibiting photoluminescence quantum yield close to unity and narrow emission line widths are essential for next-generation electroluminescence displays, yet their synthesis is highly challenging. Herein, we develop the synthesis of blue-emitting QDs by growing a thin shell of ZnS on ZnSe cores with their size larger than bulk Bohr diameter. The bulk-like size of ZnSe cores enables the emission to locate in the blue region with a narrow emission width close to its intrinsic peak width. The obtained bulk-like ZnSe/ZnS core/shell QDs display high quantum yield of 95% and extremely narrow emission width of ∼9.6 nm. Moreover, the bulk-like size of ZnSe cores reduces the energy level difference between QDs and adjacent layers in LEDs and improves charge transport. The LEDs fabricated with these high-quality QDs show bright pure blue emission with an external quantum efficiency of 12.2% and a relatively long operating lifetime.

Sensitive Immunoassay Based on Biocompatible and Robust Silica-Coated Cd-Free InP-Based Quantum Dots.

Low-toxic InP quantum dots (QDs) as an ideal candidate for Cd-based QDs have tremendous potential for next-generation commercial display and biological detection applications. However, the progress in biological detection is still far behind that of the Cd-based QDs. This is mainly because the InP-based QDs are of inferior stability and photoluminescence quantum yield (PL QY) in aqueous solution. Here, PL QY of 65% and excellent stability of InP/GaP/ZnS QD@SiO2 nanoparticles have been successfully synthesized via a silica coating method. The containing thiol-capped hydrophobic InP/GaP/ZnS QDs were pre-silanized with waterless, ammonia-free hydrolysis tetraethyl orthosilicate, and subsequently, an outer silica shell was generated in the reverse microemulsion. The corresponding QD-based fluorescence-linked immunosorbent assay exhibits a high sensitivity of 0.9 ng mL-1 for C-reactive protein and the broad detection range of 1-1000 ng mL-1, which was close to that of the state-of-the-art Cd-based QD@SiO2 nanoparticles and had the highest sensitivity of Cd-free QDs so far. This work provides a very successful silica coating method for the containing thiol-capped hydrophobic QDs and the QDs highly sensitive to water and oxygen, and the obtained InP/GaP/ZnS QD@SiO2 nanoparticles were considered as the robust, biocompatible, and promising Cd-free fluorescent labels for the further ultra-sensitive detection.

Mesoporous silica nanoparticles loaded with fluorescent coumarin-5-fluorouracil conjugates as mitochondrial-targeting theranostic probes for tumor cells.

In this study, a nanodrug carrier (mesoporous silica nanoparticle (MSN)-SS-cysteamine hydrochloride (CS)-hyaluronic acid (HA)) for targeted drug delivery was prepared using MSNs, in which HA was used as a targeting ligand and blocking agent to control drug release. Coumarin is a fluorescent molecule that targets mitochondria. Two conjugates (XDS-DJ and 5-FUA-4C-XDS) were synthesized by chemically coupling nitrogen mustard and 5-fluorouracil with coumarin, which was further loaded into MSN-SS-CS-HA nanocarriers. MTT analysis demonstrated that the nanocomposite MSN-SS-CS@5-FUA-4C-XDS/HA displayed stronger cytotoxicity toward HCT-116 cells than HeLa or QSG-7701 cells. Furthermore, MSN-SS-CS@5-FUA-4C-XDS/HA was able to target the mitochondria of HCT-116 cells, causing decreased mitochondrial membrane potential and excessive production of reactive oxygen species. These results indicate that MSN-SS-CS@5-FUA-4C-XDS/HA has the potential to be a nanodrug delivery system for the treatment of colon cancer.

A quantum dot microspheres-based highly specific and sensitive three-dimensional microarray for multiplexed detection of inflammatory factors.

The development trend ofin vitrodiagnostics is to obtain various biological information from a sample at extremely low concentration and volume, which has promoted its progress in accurate and sensitive multiplexed detection. Here, we developed a single color quantum dot (QD) based three-dimensional (3D) structure matrix microarray and conducted the detection of two inflammatory factors (C-reactive protein (CRP) and serum amyloid A (SAA)) by a self-built fluorescence detection system. This strategy increased detection sensitivity by immobilizing the antibody specifically on the 3D substrate because it captured more than about 7 times of 'effective' antibodies compared to the two-dimensional (2D) plane. Compared to the dual QDs-2D fluorescence-linked immunosorbent assay, the limit of detection (LOD) of 3D microarray based on QDs modified with amphiphilic polymers has been further improved to 0.11 ng ml-1for SAA assay and to 0.16 ng ml-1for CRP assay, respectively. By using QD microspheres (SiO2@QDs@SiO2-COOH, containing approximately 200-300 hydrophobic QDs on per SiO2sphere) as fluorescent labels, the LOD for CRP and SAA of 3D microarray reached as high as 15 pg ml-1and 86 pg ml-1, and the sensitivity was further improved by 28-fold and 425-fold, respectively. Because of its excellent performance, this QD microspheres-based 3D microarray has great application potential for highly sensitive and multiplexed quantitative detection of other biomarkers, small molecules, and antibiotic residues in biomedicine and food safety.

A competitive immunoassay based on engineered magnetic/fluorescent nanoparticles and biolayer interferometry-based assay for T-2 toxin determination.

For the first time a competitive immunoassay was developed by employing T-2 antibody-functionalized magnetite nanoparticles and T-2 toxin-conjugated fluorescent quantum dots (QDs). Free T-2 and the T-2-modified QDs compete for binding to antibody-modified magnetic beads; the magnetic beads collected by magnetic separation were subjected to fluorescence intensity analysis (with excitation/emission wavelengths at 460/616 nm). This competitive immunoassay for T-2 toxin determination was applied both in a microcentrifuge tube and on a 96-well plate. The dynamic range of the immunoassay is 1-100 ng mL-1, the limit of detection (LOD) is 0.1 ng mL-1, and determination was completed in about 40 min and 30 min in the microcentrifuge tube and 96-well plate, respectively. Moreover, the biolayer interferometry (BLI) technique was employed for T-2 determination for the first time, in which the conjugate of T-2 toxin and bovine serum albumin (BSA) was immobilized on the sensors before detection. Its average recovery of T-2 toxin from barley sample ranged from 82.00 to 123.33%, and the relative standard deviation (RSD) was between 9.42 and 15.73%. The LOD of the BLI-based assay is 5 ng mL-1, and it only takes 10 min to finish the determination. Graphical abstract.

High-efficiency CdSe/CdS nanorod-based red light-emitting diodes.

In this paper, we report the synthesis, the structural and optical characterization of CdSe/CdS//CdS nanorods (NRs) and their exploitation in nanorod-based light-emitting diodes (NR-LEDs). Two kinds of NRs of CdSe/CdS and CdSe/CdS//CdS were incorporated into the structure of solution-processed hybrid NR-LEDs. Compared to CdSe/CdS, the efficiencies of CdSe/CdS//CdS NR-based LEDs are overwhelmingly higher, specifically showing unprecedented values of peak current efficiency of 19.8 cd/A and external quantum efficiency of 15.7%. Such excellent results are likely attributable to a unique structure in CdSe/CdS//CdS NRs with a relatively high quantum yield, thick CdS outer shell, and rod structure which minimize nonradiative energy transfer between closely packed NRs in emitting layer.

Highly sensitive and accurate detection of C-reactive protein by CdSe/ZnS quantum dot-based fluorescence-linked immunosorbent assay.

BACKGROUND: The conventional and widely used enzyme-linked immunosorbent assays (ELISA), due to specificity and high-sensitivity, were suitable in vitro diagnosis. But enzymes are vulnerable to the external conditions, and the complex operation steps limit its application. Semiconductor quantum dots have been successfully used in biological and medical research due to the high photoluminescence and high resistance to photobleaching. In this study, we have developed a novel quantum dot-labeled immunosorbent assay for rapid disease detection of C-reactive protein (CRP). RESULTS: The assay for the detection of CRP can provide a wide analytical range of 1.56-400 ng/mL with the limit of detection (LOD) = 0.46 ng/mL and the limit of quantification = 1.53 ng/mL. The precision of the assay has been confirmed for low coefficient of variation, less than 10% (intra-assay) and less than 15% (inter-assay). The accuracy of assay meets the requirements with the recoveries of 95.4-105.7%. Furthermore, clinical samples have been collected and used for correlation analysis between this FLISA and gold standard Roche immunoturbidimetry. It shows excellent accurate concordance and the correlation coefficient value (R) is as high as 0.989 (n = 34). CONCLUSIONS: This in vitro quantum dot-based detection method offers a lower LOD and a wide liner detection range than ELISA. The total reaction time is only 50 min, which is much shorter than the commercialization ELISA (about 120 min). All of the results show that a convenient, sensitive, and accurate fluorescence-linked immunosorbent assay method has been well established for the detection of CRP samples. Therefore, this method has immense potential for the development of rapid and cost-effective in vitro diagnostic kits.

High-efficiency, low turn-on voltage blue-violet quantum-dot-based light-emitting diodes.

We report high-efficiency blue-violet quantum-dot-based light-emitting diodes (QD-LEDs) by using high quantum yield ZnCdS/ZnS graded core-shell QDs with proper surface ligands. Replacing the oleic acid ligands on the as-synthesized QDs with shorter 1-octanethiol ligands is found to cause a 2-fold increase in the electron mobility within the QD film. Such a ligand exchange also results in an even greater increase in hole injection into the QD layer, thus improving the overall charge balance in the LEDs and yielding a 70% increase in quantum efficiency. Using 1-octanethiol capped QDs, we have obtained a maximum luminance (L) of 7600 cd/m(2) and a maximum external quantum efficiency (ηEQE) of (10.3 ± 0.9)% (with the highest at 12.2%) for QD-LEDs devices with an electroluminescence peak at 443 nm. Similar quantum efficiencies are also obtained for other blue/violet QD-LEDs with peak emission at 455 and 433 nm. To the best of our knowledge, this is the first report of blue QD-LEDs with ηEQE > 10%. Combined with the low turn-on voltage of ∼2.6 V, these blue-violet ZnCdS/ZnS QD-LEDs show great promise for use in next-generation full-color displays.

Multimodal phototherapy agents target lipid droplets for near-infrared imaging-guided type I photodynamic/photothermal therapy.

The construction and optimization of a single phototherapeutic agent with photoluminescence, type I photodynamic therapy (PDT), and photothermal therapy (PTT) functions remain challenging. In this study, we aimed to design and synthesize four donor-acceptor (D-A) type aggregation-induced emission molecules: PSI, TPSI, PSSI, and TPSSI. We employed phenothiazine as an electron donor and 1,3-bis(dicyanomethylidene)indan as a strong electron acceptor in the synthesis process. Among them, TPSSI exhibited efficient type I reactive oxygen species generation, high photothermal conversion efficiency (45.44 %), and near-infrared emission. These observations can be attributed to the introduction of a triphenylamine electron donor group and a thiophene unit, which resulted in increased D-A strengths, a reduced singlet-triplet energy gap, and increased free intramolecular motion. TPSSI was loaded into bovine serum albumin to prepare biocompatible TPSSI nanoparticles (NPs). Our results have indicated that TPSSI NPs can target lipid droplets with negligible dark toxicity and can efficiently generate O2•- in hypoxic tumor environments. Moreover, TPSSI NPs selectively targeted 4T1 tumor tissues and exhibited a good PDT-PTT synergistic effect in vitro and in vivo. We believe that the successful preparation of multifunctional phototherapeutic agents will promote the development of efficient tumor diagnosis and treatment technologies. STATEMENT OF SIGNIFICANCE: The construction of a single phototherapeutic agent with photoluminescence, type I photodynamic therapy, and photothermal therapy functions, and its optimization remain challenging. In this study, we construct four donor-acceptor aggregation-induced emission molecules using phenothiazine as an electron donor and 1,3-Bis(dicyanomethylidene)indan as a strong electron acceptor. By optimizing the molecular structure, an integrated phototherapy agent with fluorescence imaging ability and high photodynamic / photothermal therapy performance was prepared. We believe that the successful preparation of multifunctional phototherapeutic agents will promote the development of efficient tumor diagnosis and treatment technology.

Tailored three-color quantum dots nanobeads for multiplexed detection with tunable detection range and multilevel sensitivity of signal-amplified immunosensor.

The excellent optical properties of quantum dots (QDs) make them as an ideal fluorescent probe for multiplexed detection, however, the interference between different emission spectra, the dependence of excitation wavelengths, and the sharp decrease of quantum yield (QY) during surface modification are issues that cannot be ignored. Herein, a dual protection scheme of polymer and silica was proposed to prepare high-quality three-color QDs nanobeads using QDs with different ligands. In comparison with single-core QDs, the fluorescence signal of the prepared QD nanobeads (QBs) is increased by more than 1,000 times and has better stability. Considering the excitation efficiency of QDs, we tailor three-color QBs as fluorescent probes based on fluorescence-linked immunosorbent assays (tQBs-FLISA) to detect multiple inflammatory biomarkers simultaneously with tunable detection ranges. This resulted in highly sensitive detection of three inflammatory biomarkers in comparison to the single-core QD-FLISA, the sensitivities of C-reactive protein (CRP), serum amyloid A (SAA), and procalcitonin (PCT) were increased by 16-fold, 19-fold, and 5-fold, respectively, to 0.48 ng/mL, 0.42 ng/mL, and 10 pg/mL. Furthermore, the tQBs-FLISA showed good accuracy without interference from common serum factors. In this strategy, a three-color QBs suitable for multilevel sensitivity and tunable detection range was tailored using the versatile polymer and silica dual protection method, building high-performance immunosensor for in vitro diagnostics (IVD).

Tailored different sizes of quantum dot nanobeads for sensitive and quantitative detection based on the competition fluorescence-linked immunosorbent assay platform.

Highly stable and multicolor photoluminescent (PL) quantum dots (QDs) have attracted widespread attention as ideal probe materials in the field of in vitro diagnostics (IVD), especially the fluorescence-linked immunosorbent assay (FLISA), due to their advantages of high-throughput, high stability, and high sensitivity. However, the size of QDs as fluorescent probes have significant effects on antigen-antibody performance. Therefore, it is critical to design suitable QDs for obtain excellent quantitative detection-based biosensors. In this paper, we prepared different sizes of aqueous QDs (30 nm, 116 nm, 219 nm, and 320 nm) as fluorescent probes to optimize the competitive FLISA platform. The SARS-CoV-2 neutralizing antibody (NTAB) assay was used as an example, and it was found that the size of the QDs has a significant impact on the antigen-antibody binding efficiency and detection sensitivity in competitive FLISA platform. The results showed that these QD nanobeads (QBs, ∼219 nm) could be used as a labeled probe for competitive FLISA, with half-maximal inhibitory concentration (IC50) of 1.34 ng/mL and limit of detection (LOD) of 0.21 pg/mL for NTAB detection. More importantly, the results showed good specificity and accuracy, and the QB219 probe was able to efficiently bind NTAB without interference from other substances in the serum. Given the above advantages, the nanoprobe material (∼200 nm) offers considerable potential as a competitive FLISA platform in the field of IVD.

Highly efficient near-infrared light-emitting diodes by using type-II CdTe/CdSe core/shell quantum dots as a phosphor.

In this paper, we present an innovative method for the synthesis of CdTe/CdSe type-II core/shell structure quantum dots (QDs) using 'greener' chemicals. The PL of CdTe/CdSe type-II core/shell structure QDs ranges from 600 to 820 nm, and the as-synthesized core/shell structures show narrow size distributions and stable and high quantum yields (50­75%). Highly efficient near-infrared light-emitting diodes (LEDs) have been demonstrated by employing the CdTe/CdSe type-II core/shell QDs as emitters. The devices fabricated based on these type-II core/shell QDs show color-saturated near-infrared emission from the QD layers, a low turn-on voltage of 1.55 V, an external quantum efficiency (EQE) of 1.59%, and a current density and maximum radiant emittance of 2.1 × 10(3) mA cm−2 and 17.7 mW cm−2 at 8 V; it is the first report to use type-II core/shell QDs as near-infrared emitters and these results may offer a practicable platform for the realization of near-infrared QD-based light-emitting diodes, night-vision-readable displays, and friend/foe identification system.

Recent advances in quantum dot-based fluorescence-linked immunosorbent assays.

Fluorescence immunoassays have been given considerable attention among the quantitative detection methods in the clinical medicine and food safety testing fields. In particular, semiconductor quantum dots (QDs) have become ideal fluorescent probes for highly sensitive and multiplexed detection due to their unique photophysical properties, and the QD fluorescence-linked immunosorbent assay (FLISA) with high sensitivity, high accuracy, and high throughput has been greatly developed recently. In this manuscript, the advantages of applying QDs to FLISA platforms and some strategies for their application to in vitro diagnostics and food safety are discussed. Given the rapid development of this field, we classify these strategies based on the combination of QD types and detection targets, including traditional QDs or QD micro/nano-spheres-FLISA, and multiple FLISA platforms. In addition, some new sensors based on the QD-FLISA are introduced; this is one of the hot spots in this field. The current focus and future direction of QD-FLISA are also discussed, which provides important guidance for the further development of FLISA.

DNA tetrahedron-mediated triplex molecular switch for extracellular pH monitoring.

This study aimed to construct a novel DNA triplex molecular switch modified with DNA tetrahedron (DTMS-DT) with sensitive response to extracellular pH using a DNA tetrahedron as the anchoring unit and DNA triplex as the response unit. The results showed that the DTMS-DT had desirable pH sensitivity, excellent reversibility, outstanding anti-interference ability, and good biocompatibility. Confocal laser scanning microscopy suggested that the DTMS-DT could not only be stably anchored on the cell membrane but also be employed to dynamically monitor the change in extracellular pH. Compared with the reported probes for extracellular pH monitoring, the designed DNA tetrahedron-mediated triplex molecular switch exhibited higher cell surface stability and brought the pH-responsive unit closer to the cell membrane surface, making the results more reliable. In general, developing the DNA tetrahedron-based DNA triplex molecular switch is helpful for understanding and illustrating the pH dependent cell behaviors and disease diagnostics.

Establishment of a Ca(II) ion-quantum dots fluorescence signal amplification sensor for high-sensitivity biomarker detection.

Quantum dots (QDs) have been considered as the promising fluorescent labeling material, which is expected to meet the requirement of high-sensitivity detection in clinical diagnostics. Some common metal ions are known to affect the stability and fluorescence properties of QDs, but scarcely any systematic research has been done about their impacts on QD-based bio-detection. By evaluating the effect of Ca2+ metal ions on the properties of aqueous QDs, a new metal ion-QD fluorescence signal amplification sensor (i.e., Ca2+-QD-fluorescence-linked immunosorbent assay, Ca2+-QD-FLISA) has been developed for the detection of inflammatory biomarkers with high sensitivity. Compared with the common QD-FLISA, the detection sensitivity for CRP of Ca2+-QD-FLISA was improved by a 4-fold of magnitude to 0.23 ng/mL, and this assay showed good selectivity, high accuracy, and excellent repeatability. The versatility of the QD-FLISA method were also validated by using different metal ion-QD probes (Ca2+, Mg2+, Ba2+, Fe2+, and Mn2+) to detect CRP, serum amyloid A (SAA), and procalcitonin (PCT). The significant improvement in detection sensitivity was achieved due to the crosslinking of aqueous QDs by Ca2+ ions to enhance fluorescence and at the same time promote antigen-antibody binding efficiency. The present study illustrates the versatility of metal ion-QD-FLISA as a simple and effective method to detect a wide range of biomarkers with high sensitivity and accuracy.