Suspension Array of Ionic Liquid or Ionic Liquid–Quantum Dots Conjugates for the Discrimination of Proteins and Bacteria

It is of great importance to develop novel and sensitive sensing materials for the detection of proteins and microorganisms to fulfill the demand of disease diagnosis. As the selectivity and sensitivity of sensing systems are highly dependent on the receptor, the fluorescent sensor array with imidazolium ionic liquids (ILs) and ionic liquid–quantum dots conjugates as semiselective receptors is developed for protein/bacteria differential sensing or discrimination. The IL sensing system formed by 1,3-dibutylimidazolium chloride (BBimCl), 1,3-diethylimidazolium bromine (EEimBr), 1,3-dibutylimidazolium bromine (BBimBr), 1,3-dihexylimidazolium bromine (HHimBr), and 1,3-dioctylimidazolium bromine (OOimBr) and the IL@QDs/QDs sensing system formed by CdTe, BBimCl@CdTe, EEimBr@CdTe, BBimBr@CdTe, and HHimBr@CdTe are tested, by transferring the interaction binding difference between receptors and proteins to the fluorescent response pattern. The IL sensing system is applied to the identification of 48 samples (8 proteins at 500 nM) with an accuracy of 91.7%. For the IL@QDs/QDs sensing system, 8 proteins are completely distinguished with 100% accuracy at a very low concentration level of 10 nM. Remarkably, 36 training cases (6 strains of bacteria from 3 different species) are discriminated with 100% (OD₆₀₀ of 0.1)

In Situ Growth of Silver Nanoparticles on Graphene Quantum Dots for Ultrasensitive Colorimetric Detection of H₂O₂ and Glucose

We report a facile green approach for in situ growth of silver nanoparticles (AgNPs) on the surface of graphene quantum dots (GQDs). GQDs serve as both reducing agent and stabilizer, and no additional reducing agent and stabilizer is necessary. The GQDs/AgNPs hybrid exhibits a superior absorbance fading response toward the reduction of H₂O₂. A simple colorimetric procedure is thus proposed for ultrasensitive detection of H₂O₂ without additional chromogenic agent. It provides a record detection limit of 33 nM for the detection of H₂O₂ by the AgNPs-based sensing system. This colorimetric sensing system is further extended to the detection of glucose in combination with the specific catalytic effect of glucose oxidase for the oxidation of glucose and formation of H₂O₂, giving rise to a detection limit of 170 nM. The favorable performances of the GQDs/AgNPs hybrid are due to the peroxidase-like activity of GQDs

Graphene Oxide–Rare Earth Metal–Organic Framework Composites for the Selective Isolation of Hemoglobin

Graphene oxide-La­(BTC)­(H₂O)₆ (H₃BTC=1,3,5-benzenetricarboxylic acid) metal organic framework composites (LaMOF-GO_<i>n</i>, <i>n</i> = 1–6, corresponding to the percentage of GO at 1, 2, 3, 4, 5, and 10%) are prepared through a simple and large-scale method at room temperature. The obtained composites are characterized by ATR-FTIR spectra, SEM, XRD, TGA, and N₂ adsorption–desorption isotherm. The presence of GO significantly changes the morphologies of the composites from spindly rectangular rods to irregular thick blocks and increases their surface area from 14.8 cm² g^–1 (LaMOFs) to 26.6 cm² g^–1 (LaMOF-GO₃), whereas at the same time, the crystalline structure of La­(BTC)­(H₂O)₆ is maintained. As a novel solid-phase adsorbent the LaMOF-GO composite exhibits outstanding adsorption properties for proteins. The strong hydrophobic interaction, especially π–π interaction between protein and the composite, is the main driving force for protein adsorption. In particular, highly selective isolation of hemoglobin (Hb) is achieved by using LaMOF-GO₃ composite as sorbent in 4 mM B-R buffer containing 0.05 mol L^–1 NaCl at pH 8. The retained Hb could be effectively recovered with a 1 mM B-R buffer at pH 10, giving rise to a recovery of 63%. The practical applicability of the LaMOF-GO₃ composite is demonstrated by the selective adsorption of Hb from human whole blood, and SDS-PAGE assays indicate that Hb could be selectively isolated with high purity from biological samples of complex matrixes

Quantum-Dot-Conjugated Graphene as a Probe for Simultaneous Cancer-Targeted Fluorescent Imaging, Tracking, and Monitoring Drug Delivery

We report a novel quantum-dot-conjugated graphene, i.e., hybrid SiO₂-coated quantum dots (HQDs)-conjugated graphene, for targeted cancer fluorescent imaging, tracking, and monitoring drug delivery, as well as cancer therapy. The hybrid SiO₂ shells on the surface of QDs not only mitigate its toxicity, but also protect its fluorescence from being quenched by graphene. By functionalizing the surface of HQDs-conjugated graphene (graphene-HQDs) with transferrin (Trf), we developed a targeted imaging system capable of differential uptake and imaging of cancer cells that express the Trf receptor. The widely used fluorescent antineoplastic anthracycline drug, doxorubicin (DOX), is adsorbed on the surface of graphene and results in a large loading capacity of 1.4 mg mg^–1. It is advantageous that the new delivery system exhibits different fluorescence color in between graphene-HQDs and DOX in the aqueous core upon excitation at a same wavelength for the purpose of tracking and monitoring drug delivery. This simple multifunctional nanoparticle system can deliver DOX to the targeted cancer cells and enable us to localize the graphene-HQDs and monitor intracellular DOX release. The specificity and safety of the nanoparticle conjugate for cancer imaging, monitoring, and therapy has been demonstrated in vitro

Quantum Dots Conjugated with Fe₃O₄‑Filled Carbon Nanotubes for Cancer-Targeted Imaging and Magnetically Guided Drug Delivery

A novel and specific nanoplatform for in vitro simultaneous cancer-targeted optical imaging and magnetically guided drug delivery is developed by conjugating CdTe quantum dots with Fe₃O₄-filled carbon nanotubes (CNTs) for the first time. Fe₃O₄ is filled into the interior of the CNTs, which facilitates magnetically guided delivery and improves the synergetic targeting efficiency. In comparison with that immobilized on the external surface of CNTs, the magnetite nanocrystals inside the CNTs protect it from agglomeration, enhance its chemical stability, and improve the drug loading capacity. It also avoids magnetic nanocrystals-induced quenching of fluorescence of the quantum dots. The SiO₂-coated quantum dots (HQDs) attached on the surface of CNTs exhibit favorable fluorescence as the hybrid SiO₂ shells on the QDs surface prevent its fluorescence quenching caused by the CNTs. In addition, the hybrid SiO₂ shells also mitigate the toxicity of the CdTe QDs. By coating transferrin on the surface of the herein modified CNTs, it provides a dual-targeted drug delivery system to transport the doxorubicin hydrochloride (DOX) into Hela cells by means of an external magnetic field. The nanocarrier based on the multifunctional nanoplatform exhibits an excellent drug loading capability of ca. 110%, in addition to cancer-targeted optical imaging as well as magnetically guided drug delivery

Nano Copper Oxide-Incorporated Mesoporous Carbon Composite as Multimode Adsorbent for Selective Isolation of Hemoglobin

Assembly of nano-objects with tunable size, morphology and function into integrated nanostructures is critical for the development of a novel nanosystem in adsorption, sensing and drug/gene delivery. We demonstrate herein the fabrication of ordered mesoporous carbon by assembling uniform and highly dispersed copper-oxide (Cu_<i>x</i>O_<i>y</i>) nanoparticles into the mesopores via evaporation of solvent from the mixture of triblock copolymer, carbon source and metal nitrate hydrate. The ordered 2D hexagonal mesoporous carbon composite possesses a large surface area of 580.8 cm²/g, a uniform pore size of 5.4 nm, a large pore volume of 0.64 cm³/g and a high metal content of 3.32 wt %. The mesoporous composite exhibits excellent adsorption selectivity and high adsorption capacity to hemoglobin (Hb) under the synergistic effect of hydrophobic and metal-affinity interactions as well as size exclusion. This facilitates multimode adsorption of hemoglobin fitting Langmuir adsorption model and offers an adsorption capacity of 1666.7 mg g^–1 for hemoglobin. The mesoporous composite is used for the isolation of hemoglobin from human whole blood with high purity. It demonstrates the potential of the copper-oxide nanoparticle-embedded mesoporous carbon composite in selective isolation/removal of specific protein species from biological sample matrixes

Selective Isolation of Myosin Subfragment‑1 with a DNA-Polyoxovanadate Bioconjugate

The bioconjugation of a polyoxometalate (POMs), i.e., dodecavanadate (V₁₂O₃₂), to DNA strands produces a functional labeled DNA primer, V₁₂O₃₂-DNA. The grafting of DNA primer onto streptavidin-coated magnetic nanoparticles (SVM) produces a novel composite, V₁₂O₃₂-DNA@SVM. The high binding-affinity of V₁₂O₃₂ with the ATP binding site in myosin subfragment-1 (S1) facilitates favorable adsorption of myosin, with an efficiency of 99.4% when processing 0.1 mL myosin solution (100 μg mL^–1) using 0.1 mg composite. Myosin adsorption fits the Langmuir model, corresponding to a theoretical adsorption capacity of 613.5 mg g^–1. The retained myosin is readily recovered by 1% SDS (m/m), giving rise to a recovery of 58.7%. No conformational change is observed for myosin after eliminating SDS by ultrafiltration. For practical use, high-purity myosin S1 is obtained by separation of myosin from the rough protein extract from porcine left ventricle, followed by digestion with α-chymotryptic and further isolation of S1 subfragment. The purified myosin S1 is identified with matrix-assisted laser desorption/ionization time-of-flight/mass spectrometry, giving rise to a sequence coverage of 38%

Assay of Biothiols by Regulating the Growth of Silver Nanoparticles with C‑Dots as Reducing Agent

Recently, the development of optical probes for the assay of thiols, e.g., cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), has been an active research area due to their biological significance. We have found that carbon dots (C-dots) exhibit direct reduction of Ag⁺ to elemental silver (Ag⁰) and the resulting Ag⁰ formed a silver nanoparticle (Ag-NP) spontaneously. The excessive C-dots consume free Ag⁺ in the solution by binding Ag⁺ with functional groups on the C-dots surface and thus inhibits the growth of Ag-NPs. Biothiols can coordinate with Ag⁺ through thiol groups, and afterward, the Ag⁺-biothiol complex gradually releases free Ag⁺ to ensure its reduction by C-dots and thus facilitates the growth of Ag-NPs on C-dots surface. A colorimetric assay procedure is thus developed for fast detection of biothiols based on Ag-NPs plasmon absorption. The linear calibration range can be regulated by controlling the concentration of Ag⁺. Two linear ranges were obtained for the biothiols assay at different levels, which offer ultrahigh sensitivity for the assay of an ultratrace amount of biothiols with detection limits of 1.5, 2.6, and 1.2 nM for Cys, Hcy, and GSH, respectively. The precisions for the assay of Cys, Hcy, and GSH at 20 nM are achieved as 3.1%, 3.1%, and 2.4%. In addition, the sensing system exhibits good selectivity toward biothiols in the presence of other amino acids, the major metal cations, and biomolecules in biological fluids. For the assay of 20 nM Cys, 150-fold of coexisting amino acids, 2500-fold of Ca²⁺, Mg²⁺, glucose, and ascorbic acid, and 38-fold of HSA are tolerated. In the assay of Cys in human plasma, spiking recoveries of 94% to 108% are obtained at 100 μM

Hollow Copper Sulfide Nanosphere–Doxorubicin/Graphene Oxide Core–Shell Nanocomposite for Photothermo-chemotherapy

A novel core–shell nanostructure, hollow copper sulfide nanosphere–doxorubicin (DOX)/graphene oxide (GO) (CuS–DOX/GO), is constructed for the purpose of controlled drug delivery and improved photothermo-chemotherapeutic effect. The CuS–DOX/GO nanocomposite is configured by employing dual photothermal agents, where the core, hollow CuS nanoparticle, acts as delivery-carrier for doxorubicin, and the shell, PEGylated GO nanosheet, prohibits leakage of the drug. DOX can be efficiently loaded onto the hollow CuS nanoparticles, and its subsequent release from CuS–DOX/GO nanocomposite is triggered in a pH- and near-infrared light-dependent manner. Moreover, integration of the two photothermal agents significantly improves the photothermal performance of this system. Ultimately, the combination of phototherapy and chemotherapy based on this system results in a much higher HeLa cell killing efficacy with respect to that for a single chemotherapy mode, as demonstrated by in vitro cytotoxicity tests

High Time-Resolution Optical Sensor for Monitoring Atmospheric Nitrogen Dioxide

High time-resolution monitoring of nitrogen dioxide (NO₂) is of great importance for studying the formation mechanism of aerosols and improving air quality. Based on the Griess–Saltzman (GS) reaction, a portable NO₂ optical sensor was developed by employing a porous polypropylene membrane tube (PPMT) integrated gas permeation collector and detector. The PPMT was filled with GS reagents and covered with a coaxial jacket tube for gas collection. Its two ends were respectively fixed with a yellowish-green light-emitting diode and a photodiode for optic signal reception. NO₂ was automatically introduced through the collector by two air pumps cooperating with a homemade gas injector. Under the optimized conditions, the device presented good performance for monitoring NO₂, such as a limit of detection of 5.1 ppbv (parts per billion by volume), an intraday precision of 4.1% (RSD, relative standard deviation, <i>n</i> = 11, <i>c</i> = 100 ppbv), an interday precision of 5.7% (RSD, <i>n</i> = 2–3 per day for 5 days, <i>c</i> = 100 ppbv), an analysis time of 4.0 min, and a linearity range extended to 700 ppbv. The developed device was successfully applied to analyzing outdoor air with a comparable precision to that of the standard method of China. The high time-resolution characteristic that includes sampling 15 times per hour and a good stability for 10 days of urban air analysis had also been evaluated