Advances in fluorescent carbon dots for biomedical applications

Carbon Dots are an emerging class of carbon-based nanoparticles, which since their discovery have attracted tremendous attention because of their exceptional fluorescent, chemical and mechanical properties as well as high photostability and biocompatibility. This unique combination of outstanding characteristics, together with the ease with which they can be synthesized, qualify carbon dots as highly promising materials for applications in electronics and biology, in particular, for biosensing, bioimaging, biotherapy and drug delivery. In this review, we present some of the most recent applications of carbon dots in biology and medicine, concentrating on their fluorescence properties, biocompatibility and efficiency; we also discuss how improvements could prompt their use in human studies. We illustrate how carbon dots, prepared through several facile and cost-effective methods by either the bottom-up or the top-down route, can be used for imaging cells and bacteria and as sensing probes of metal cations. Moreover, we explain how their astonishing versatility has given rise to new biotherapy methods especially in the field of cancer theranostics

A Review of Structure, Properties, and Chemical Synthesis of Magnetite Nanoparticles

Extensive studies were devoted to iron oxide nanoparticles (IONPs), in recent years. Iron oxides are chemical compounds that have various polymorphic forms, including maghemite (γ-Fe2O3), magnetite (Fe3O4), and Hematite (α-Fe2O3). Among them, the most important studied is magnetite (Fe3O4) due to its low cost and low toxicity, besides its unique magnetic and physicochemical characteristics which qualified it for use in various applications such as biomedical and technological applications. Magnetic particles should be small and have a narrow size distribution for these applications. The smaller the size of the iron oxide particles, the greater their reactivity and biodegradability. In this review, we display summary information of magnetite (Fe3O4) nanoparticles in terms of structure, characteristics, and preparation methods.   Because the prepared strategy has been proven to be critical for preferable control of the particle size and shape, in addition, to producing monodispersed magnetite (Fe3O4) nanoparticles with a direct effect on their characteristics and applications, special attention will be placed on chemical preparation techniques including Hydrothermal synthesis, Co-precipitation technique, Sol-Gel process, and thermal decomposition method. This review offers specific information for selecting appropriate synthetic methods for obtaining appropriate sizes, shapes, and magnetic properties of magnetite (Fe3O4) nanoparticles (NPs) for target applications

Production of a Laccase from Botrytis cinerea (DSMZ 877) and Application for Textile Phenolic Dye Decolorization

AbstractIn this study, the production, partial purification and characterization of a laccase from Botrytis cinerea strain (DSMZ No. 877) was studied. The production of laccase was induced using copper sulphate and Gallic acid as inducers. The maximum laccase activity observed during B. cinerea growth in the presence of 0.1% Gallic acid was 2600 UL−1. Laccase purification was performed by precipitated the enzyme with 90% ammonium sulphate followed by gel filtration chromatography. The optimum pH for the laccase activity was observed at acidic pH values (close to pH 3.5 - 4.6), while the optimum temperature was 70°C. The ability of the produced laccase as well as the laccase from T. versicolor to catalyse the decolorization of a phenolic dye (phenol red) was also investigated using natural and synthetic mediators. The higher decolorization activity was observed with 1–hydroxybenzotriazole (HBT) as mediator at pH 4.5 and temperature 30° C

Germanane Monolayer Films as Antibacterial Coatings

Germanane (GeH), a graphane analogue, has attracted significant interest because of its optoelectronic properties; however, the environmental and biological effects of GeH have scarcely been investigated so far. Here we report a facile approach based on the Langmuir-Schaefer deposition to produce homogeneous and dense GeH monolayer films on various substrates. In view of possible applications and to extend the use of GeH to unexplored fields, we investigated its antibacterial activity for the first time and found that this promising 2D structure exhibits remarkable antibacterial activity against both Gram-negative and Gram-positive bacterial strains

Laccase-Functionalized Graphene Oxide Assemblies as Efficient Nanobiocatalysts for Oxidation Reactions

Multi-layer graphene oxide-enzyme nanoassemblies were prepared through the multi-point covalent immobilization of laccase from Trametes versicolor (TvL) on functionalized graphene oxide (fGO). The catalytic properties of the fGO-TvL nanoassemblies were found to depend on the number of the graphene oxide-enzyme layers present in the nanostructure. The fGO-TvL nanoassemblies exhibit an enhanced thermal stability at 60 degrees C, as demonstrated by a 4.7-fold higher activity as compared to the free enzyme. The multi-layer graphene oxide-enzyme nanoassemblies can efficiently catalyze the oxidation of anthracene, as well as the decolorization of an industrial dye, pinacyanol chloride. These materials retained almost completely their decolorization activity after five reaction cycles, proving their potential as efficient nano- biocatalysts for various applications

Smectite clays as solid supports for immobilization of beta-glucosidase:Synthesis, characterization, and biochemical properties

Nanomaterials as solid supports can improve the efficiency of immobilized enzymes by reducing diffusional limitation as well as by increasing the surface area per mass unit and therefore improving enzyme loading. In this work, beta-glucosidase from almonds was immobilized on two smectite nanoclays. The resulting hybrid biocatalysts were characterized by a combination of powder X-ray diffraction, X-ray photoelectron spectroscopy, thermogravimetric. analysis, differential thermal analysis, and infrared spectroscopy. Biochemical studies showed an improved thermostability of the immobilized enzyme as well as enhanced performance at higher temperatures and in a wider pH range

Development of a Multi-Enzymatic Biocatalytic System through Immobilization on High Quality Few-Layer bio-Graphene

In this work, we report the green production of few-layer bio-Graphene (bG) through liquid exfoliation of graphite in the presence of bovine serum albumin. Microscopic characterization evaluated the quality of the produced nanomaterial, showing the presence of 3–4-layer graphene. Moreover, spectroscopic techniques also confirmed the quality of the resulted bG, as well as the presence of bovine serum albumin on the graphene sheets. Next, for the first time, bG was used as support for the simultaneous covalent co-immobilization of three enzymes, namely β-glucosidase, glucose oxidase, and horseradish peroxidase. The three enzymes were efficiently co-immobilized on bG, demonstrating high immobilization yields and activity recoveries (up to 98.5 and 90%, respectively). Co-immobilization on bG led to an increase of apparent K(M) values and a decrease of apparent V(max) values, while the stability of the nanobiocatalysts prevailed compared to the free forms of the enzymes. Co-immobilized enzymes exhibited high reusability, preserving a significant part of their activity (up to 72%) after four successive catalytic cycles at 30 °C. Finally, the tri-enzymatic nanobiocatalytic system was applied in three-step cascade reactions, involving, as the first step, the hydrolysis of p-Nitrophenyl-β-D-Glucopyranoside and cellobiose

Hybrid Nanomaterials of Magnetic Iron Nanoparticles and Graphene Oxide as Matrices for the Immobilization of beta-Glucosidase:Synthesis, Characterization, and Biocatalytic Properties

Hybrid nanostructures of magnetic iron nanoparticles and graphene oxide were synthesized and used as nanosupports for the covalent immobilization of β-glucosidase. This study revealed that the immobilization efficiency depends on the structure and the surface chemistry of nanostructures employed. The hybrid nanostructure-based biocatalysts formed exhibited a two to four-fold higher thermostability as compared to the free enzyme, as well as an enhanced performance at higher temperatures (up to 70°C) and in a wider pH range. Moreover, these biocatalysts retained a significant part of their bioactivity (up to 40%) after 12 repeated reaction cycles

A facile approach to hydrophilic oxidized fullerenes and their derivatives as cytotoxic agents and supports for nanobiocatalytic systems

A facile, environment-friendly, versatile and reproducible approach to the successful oxidation of fullerenes (oxC60) and the formation of highly hydrophilic fullerene derivatives is introduced. This synthesis relies on the widely known Staudenmaier’s method for the oxidation of graphite, to produce both epoxy and hydroxy groups on the surface of fullerenes (C60) and thereby improve the solubility of the fullerene in polar solvents (e.g. water). The presence of epoxy groups allows for further functionalization via nucleophilic substitution reactions to generate new fullerene derivatives, which can potentially lead to a wealth of applications in the areas of medicine, biology, and composite materials. In order to justify the potential of oxidized C60 derivatives for bio-applications, we investigated their cytotoxicity in vitro as well as their utilization as support in biocatalysis applications, taking the immobilization of laccase for the decolorization of synthetic industrial dyes as a trial case.Peer ReviewedPostprint (published version

Carbon nanostructures derived through hypergolic reaction of conductive polymers with fuming nitric acid at ambient conditions

Hypergolic systems rely on organic fuel and a powerful oxidizer that spontaneously ignites upon contact without any external ignition source. Although their main utilization pertains to rocket fuels and propellants, it is only recently that hypergolics has been established from our group as a new general method for the synthesis of different morphologies of carbon nanostructures depending on the hypergolic pair (organic fuel-oxidizer). In search of new pairs, the hypergolic mixture described here contains polyaniline as the organic source of carbon and fuming nitric acid as strong oxidizer. Specifically, the two reagents react rapidly and spontaneously upon contact at ambient conditions to afford carbon nanosheets. Further liquid-phase exfoliation of the nanosheets in dimethylformamide results in dispersed single layers exhibiting strong Tyndall effect. The method can be extended to other conductive polymers, such as polythiophene and polypyrrole, leading to the formation of different type carbon nanostructures (e.g., photolumincent carbon dots). Apart from being a new synthesis pathway towards carbon nanomaterials and a new type of reaction for conductive polymers, the present hypergolic pairs also provide a novel set of rocket bipropellants based on conductive polymers.Web of Science266art. no. 159