Isolation of Cytochrome C for Proteomics with Lindqvist-type Polyiodate Modified Metal Organic Framework.

Separation and purification of Cytochrome C (Cyt-C) is important for proteomic. High efficient and selective pretreatment method for Cyt-C in real samples are always needed. Herein, polyniobate (K7H[Nb6O19]·13H2O, Nb6O19) is modified on a metal-organic framework MIL-125(Ti) through intermolecular hydrogen bonds and an aqueous-stable composite Nb6O19/MIL-125(Ti) is successfully prepared to pretreat complex protein sample. Protein adsorption studies have shown that Nb6O19/MIL-125(Ti) can promote the selective adsorption of Cyt-C due to the synergistic effect of electrostatic and hydrogen-bond interactions. At pH=10.0 (Britton-Robinson buffer), the adsorption efficiency of 300 µL 100 µg·mL-1 Cyt-C onto 1.0 mg Nb6O19/MIL-125(Ti) can reach 99.5%. The adsorption behavior of Cyt-C fits well with the Langmuir adsorption model, corresponding to a maximum theoretical adsorption capacity of 168.35 mg·g-1. Using 3 mol·L-1 NaCl as the eluent, a high elution efficiency of 92.19% is obtained. In addition, the results of the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis confirm that Nb6O19/MIL-125(Ti) efficiently adsorbed Cyt-C from scrofa heart extraction. LC-MS/MS spectrometry results show that the purification of Cyt-C reduces the abundance from the 12th to the 154th place after Nb6O19/MIL-125(Ti) treatment. Moreover, low abundant proteins, e.g., Superoxide dismutase 1, IF rod domain-containing protein and Ubiquitin-60S ribosomal protein L40 were considerably enriched. These outcomes confirm the practicability of Nb6O19/MIL-125 (Ti) as a Cyt-C extractant has potential application value in scrofa heart proteomics.

Tunable Organelle Imaging by Rational Design of Carbon Dots and Utilization of Uptake Pathways.

Employing one-step hydrothermal treatment of o-phenylenediamine and lysine to exploit their self- and copolymerization, four kinds of CDs (ECDs, NCDs, GCDs, and LCDs) are synthesized, possessing different surface groups (CH3, C-O-C, NH2, and COOH) and lipophilicity which endow them with various uptake pathways to achieve tunable organelle imaging. Specifically, highly lipophilic ECDs with CH3 group and NCDs with C-O-C group select passive manner to target to endoplasmic reticulum and nucleus, respectively. Amphiphilic GCDs with CH3, C-O-C and NH2 groups prefer caveolin-mediated endocytosis to locate at Golgi apparatus. Highly hydrophilic LCDs with CH3, NH2 and COOH groups are involved in clathrin-mediated endocytosis to localize in lysosomes. Besides, imaging results of cell division, three-dimensional reconstruction and living zebrafish demonstrate that the obtained CDs are promising potential candidates for specific organelle-targeting imaging.

Green preparation of carbon dots with different surface states simultaneously at room temperature and their sensing applications.

It is a considerable challenge to develop environmental friendly, low-cost methodology for green preparation of carbon dots (CDs). Herein, CDs with different surface states are prepared using o-phenylenediamine (o-PD) and hydroquinone (HQ) as precursors via oxidation/polymerization and Schiff base reaction at room temperature without additional oxidizing agents. Two CDs products (YCDs and GCDs) are obtained after separation with silica gel column chromatography based on their polarity differences. The different surface states endow these two CDs with different properties. The rich NO2 and OH groups on the surface of YCDs contribute to a narrow band gap, resulting in the red-shifted photoluminescence (PL) emission of this CDs product, making it a sensitive probe for the detection of toxic pollutant p-nitrophenol (p-NP) attributed to the inner filter effect, along with a detection limit of 0.08 µmol/L. GCDs are characterized with abundant surficial NH2 groups, and can be used as a potential probe to detect H2O content in D2O, giving a detection limit of 0.17 vol%.

Correction: Carbon dots with tunable dual emissions: from the mechanism to the specific imaging of endoplasmic reticulum polarity.

Correction for 'Carbon dots with tunable dual emissions: from the mechanism to the specific imaging of endoplasmic reticulum polarity' by Shuang E et al., Nanoscale, 2020, 12, 6852-6860, DOI: .

Carbon Dots as an Indicator of Acid-Base Titration and a Fluorescent Probe for Endoplasm Reticulum Imaging.

In this study, carbon dots (CDs) with red color are successfully prepared via hydrothermal treatment of o-phenylenediamine and urea. The as-prepared red CDs exhibit an acidichromism feature, making them turn purple at pH 4.4 and become blue at pH 3.3. Further investigations reveal that the surface chemical bond species of CDs are responsible for the acidichromism feature. Taking advantage of the acidichromism feature, the CDs are employed as a titration indicator for analysis of alkali samples, which gives rise to satisfactory results without significant difference between the titration methods using CDs and methyl orange or a mixture of methyl red and bromocresol green as indicators. The CDs show excitation-independent fluorescence with dual-emission at 600 and 650 nm, along with a respectable quantum yield of 20.1%, which provides the CDs with deep tissue penetration and minimum autofluorescence background that is desirable in bioimaging. In addition, the CDs are found to light up endoplasm reticulum particularly, indicating their endoplasm reticulum targeting capability, which is proven by a colocalization study with other classical subcellular dyes. Endocytosis inhibiting investigations confirm that the endoplasm reticulum targeting ability is mainly attributed to the caveolin/lipid-raft-mediated endocytosis pathways of CDs. This study not only presents a facile approach for red CDs but also explores the possibility of CDs in titration analysis and in endoplasm reticulum targeting imaging.

Carbon dots with tunable dual emissions: from the mechanism to the specific imaging of endoplasmic reticulum polarity.

Regulating the fluorescence of carbon dots (CDs) is important but highly challenging. Here, carbon dots with tunable dual emissions were facilely fabricated via modulating the polymerization and carbonization processes of o-phenylenediamine (OPD) with lysine (Lys) as the co-precursor and modulator, respectively. The self-polymerization/carbonization of the OPD molecules contributed to the blue/green emission of the OPD-derived CDs. The introduction of Lys in the CD fabrication process efficiently suppressed the carbonization of the OPD polymer chains and enhanced the self-polymerization of the OPD molecules. Meanwhile, the formed OPD-Lys co-polymer chains endowed the final CD product with a new green emission center. The dual-emissive CDs were distinctly sensitive to polarity fluctuations, providing a ratiometric fluorescence response towards solution polarity. Due to their specific distribution in the endoplasmic reticulum (ER), the as-prepared dual-emissive CDs successfully distinguished the polarity variations in ER under stress, which offers a new approach for the early diagnosis of cell injury.

Targeted imaging of the lysosome and endoplasmic reticulum and their pH monitoring with surface regulated carbon dots.

Organelles play crucial roles in cellular activities and the functions of organelles are related greatly to the pH values, therefore, the bio-imaging of targeted organelles and their related pH sensing is of great importance in biological assays. Herein we report the fluorescence imaging of specific organelles, i.e., lysosomes and endoplasmic reticulum, and their pH sensing with surface regulated carbon dots (CDs). Carbon dots functionalized with amine groups (ACDs) are first prepared by hydrothermal treatment of citric acid and urea, and then laurylamine functionalized CDs (LCDs) are obtained via the conjugation of laurylamine with ACDs. The as-prepared ACDs and LCDs provide clear and bright imaging results for the lysosome and endoplasmic reticulum, respectively. The subcellular targeting features of the two CDs are attributed to their surface chemistries and cellular uptake pathways. Moreover, both the CDs are pH responsive within a certain pH range, i.e., 4.0-5.4 for ACDs and 6.2-7.2 for LCDs. The ACDs and LCDs are thus successfully applied to visualize the pH fluctuations of the lysosome and endoplasmic reticulum in MCF-7 cells.

Hydrophobic Carbon Nanodots with Rapid Cell Penetrability and Tunable Photoluminescence Behavior for in Vitro and in Vivo Imaging.

Tunable fluorescent emission and applications in both in vitro and in vivo imaging of hydrophobic carbon nanodots (CNDs) with rapid penetration capability are reported. The hydrophobic CNDs are prepared via hydrothermal treatment of ionic liquid 1-ethyl-3-methylimidazolium bromide and exhibit excitation-dependent photoluminescence behavior along with a red-shift in the excitation/emission maxima with concentration. The quantum yields of the as-prepared CNDs are in the range of 2.5-4.8% at an excitation wavelength of 300-600 nm. The rapid penetration behavior (within 1 min) of CNDs into the cell membrane significantly reduces the sample treatment time and avoids potential fluorescence quenching induced by the interaction between CNDs and samples. A co-location study reveals that the hydrophobic CNDs are distributed mainly in the lysosome. The potentials of the hydrophobic CNDs as fluorescent probe in in vitro and in vivo imaging are well demonstrated by the labeling of HeLa cells, MCF-7 cells, A549 cells, and Kunming mice.

Improving the biocompatibility of carbon nanodots for cell imaging.

In the practice of in vivo imaging with carbon nanodots (CNDs) as probe, the volume of CNDs solution introduced into living body should be kept at minimum, and a higher concentration is needed to ensure sufficient quantity of the probe for obtaining bright image. Therefore, the improvement on biocompatibility of the CNDs is among the most important and critical issues. We report herein the improvement on the biocompatibility of CNDs with modification by ionic liquid. Amide group functionalization of carbon nanodots is first conducted through microwave irradiation, followed by coupling the ionic liquid 1-carboxymethyl-3-methyl imidazolium bromide on the surface of the Amide-CNDs via covalent conjunction to produce the modified carbon nanodots (IL-CNDs). This modification process significantly improved the biocompatibility of CNDs, as demonstrated by cell imaging at a higher concentration of CNDs. Both Amide-CNDs and IL-CNDs exhibit abundant surface functional groups, resulting in tunable fluorescent emission feature and potential applications in two-color cell imaging.

Polyhedral Oligomeric Silsesquioxane Functionalized Carbon Dots for Cell Imaging.

In the present study, octa-aminopropyl polyhedral oligomeric silsesquioxane hydrochloride salt (OA-POSS) functionalized carbon dots (CDs/POSS) are prepared by a one-pot approach with glycerol as carbon source and solvent medium. OA-POSS serves as a passivation agent, and it is obtained via hydrolytic condensation of 3-aminopropyltriethoxysilane (APTES). During the functionalization process, the amino groups on OA-POSS combine with carboxylic groups on the bare CDs via formation of amide bond to construct organic-inorganic hybrid carbon dots. The obtained CDs/POSS are well dispersed in aqueous medium with a diameter of ca. 3.6 nm. It is demonstrated that CDs/POSS provide favorable photoluminescent property with a quantum yield of 24.0%. They also exhibit resistance to photobleaching and excellent photoluminescence stability in the presence of biological sample matrix (characterized by heavy metals and organic molecules), which facilitate cell imaging in biological systems. Both the photoluminescent emission wavelength and the fluorescence intensity depend closely on the excitation wavelength, and thus, it provides a potential for multicolor imaging as demonstrated with HeLa cells and MCF-7 cells.

The regulation of hydrophilicity and hydrophobicity of carbon dots via a one-pot approach.

The regulation of hydrophilicity/hydrophobicity of carbon dots (CDs) at will is most important. One pot simultaneous preparation of hydrophilic and/or hydrophobic CDs is herein reported, via a hydrothermal process with 1-butyl-3-methylimidazolium hexafluorophosphate as the carbon source in a H3PO4-ethanol medium. The hydrophilicity or hydrophobicity of CDs (or their proportions) is simply regulated by varying the H3PO4/ethanol molar ratio. Hydrophilic and hydrophobic CDs are obtained simultaneously with H3PO4/ethanol molar ratios within 0-1.72, while hydrophilic or hydrophobic CDs are the sole product obtained from H3PO4-BmimPF6 or BmimPF6-only systems. The CDs exhibit excitation-dependent maximum fluorescence at 360/440 nm (hydrophilic) and 430/510 nm (hydrophobic), with quantum yields of 17.0% and 7.7%, respectively. Both hydrophilic and hydrophobic CDs obtained by this approach exhibit favorable biocompatibility and offer great potential in bio-imaging as demonstrated for the fluorescent labeling and imaging of live HeLa cells.

An acid-free microwave approach to prepare highly luminescent boron-doped graphene quantum dots for cell imaging.

Boron-doped graphene quantum dots (B-GQDs) are prepared via a one-pot acid-free microwave approach with graphene oxide as the carbon source and borax as the boron source. Boron atoms are incorporated into the graphene framework by attacking the defects in the graphene structure, deriving an atomic percentage of 1.44% in the final product. Boron atom doping into the graphene structure and restoration of defects in the graphene structure bring the obtained B-GQDs favorable photoluminescence behaviors. The as-prepared B-GQDs exhibit excitation-independent photoluminescence behaviors with an excitation/emission maximum at 320/430 nm, and a fluorescence quantum yield of 21.1%. Moreover, stable photoluminescence is observed within a wide range of pH 3.0-11.0. A tolerance to an external ionic strength of up to 2.0 mol L-1 KCl along with an excellent anti-photobleaching capability is achieved. The standard MTT assay suggests that the B-GQDs are of low cytotoxicity with favorable biocompatibility, and a cell viability of 87% could be achieved at 4.0 mg mL-1 of B-GQDs. The practical application of B-GQDs in bio-analysis is demonstrated by bio-imaging of HeLa cells.

Isolation/separation of plasmid DNA using hemoglobin modified magnetic nanocomposites as solid-phase adsorbent.

Hemoglobin (Hb) modified magnetic nanocomposites are prepared by immobilization of Hb onto the surface of amino-functionalized Fe(3)O(4)@SiO(2) magnetic nanoparticles via covalent bonding with glutaraldehyde as cross-linker. The obtained nanocomposites are characterized with FT-IR, SEM, XRD and surface charge analysis. A direct solid-phase extraction procedure for the isolation/separation of plasmid DNA using this nanocomposite as a novel adsorbent is thus developed. Some important experimental parameters governing the sorption efficiency, i.e., the pH of sample solution and the ionic strength, are investigated. The Hb modified magnetic nanocomposites provide a sorption capacity of 27.86 mg g(-1) for DNA. By using 2.0mg of the nanocomposites as sorption medium and a suitable acidity of pH 6.1, a sorption efficiency of 93% is achieved for 25 µg mL(-1) of DNA in 1.0 mL of sample solution. Afterwards, the absorbed DNA could be readily recovered by using 1.0 mL of Tris-HCl buffer (pH 8.9, 0.01 mol L(-1)), giving rise to a recovery of ca. 68.3%. The present solid-phased extraction protocol is applied for the isolation of plasmid DNA from Escherichia coli culture, resulting in comparable yield and purity of plasmid DNA with respect to those obtained by using commercial kits.