Photoluminescent and superparamagnetic reduced graphene oxide-iron oxide quantum dots for dual-modality imaging, drug delivery and photothermal therapy

Reduced graphene oxide–iron oxide quantum dots (QDs) with intrinsic photoluminescent and superparamagnetic properties were synthesized through a green, hydrothermal method that simultaneously reduced and shattered graphene nanosheets to form the dots. The structure, morphology, properties and cell viability of these QDs were investigated. The QDs emitted violet light when excited at 320 nm, possessed no residual magnetization upon magnetic hysteresis tests, and had low cytotoxicity to healthy cells at low concentrations. The suitability of the QDs for fluorescent and magnetic resonance dual-modality imaging was shown by in vitro imaging with dermal fibroblast cells and T2 relaxation time. A drug could be loaded onto the surface of the QDs, with a loading ratio of drug to QD of 0.31:1. The drug achieved a steady but full release from the QDs over 8 h: these drug-loaded QDs could be manipulated by an external magnetic stimulation for targeted drug delivery. The potential for use as a cancer photothermal therapy was demonstrated by both a rapid, ∼50 °C temperature increase by a suspension of 100 μg ml−1 of QDs and the photothermal ablation of HeLa cells in vitro under near infrared irradiation. The stability of the MGQDs in fetal calf serum was shown to improve when an ionic drug was coated on the surface

A review on the heat and mass transfer phenomena in nanofluid coolants with special focus on automotive applications

Engineered suspensions of nanosized particles (nanofluids) are characterized by superior thermal properties. Due to the increasing need for ultrahigh performance cooling in many industries, nanofluids have been widely investigated as next-generation coolants. However, the multiscale nature of nanofluids implies nontrivial relations between their design characteristics and the resulting thermo-physical properties, which are far from being fully understood. This pronounced sensitivity is the main reason for some contradictory results among both experimental evidence and theoretical considerations presented in the literature. In this Review, the role of fundamental heat and mass transfer mechanisms governing thermo-physical properties of nanofluids is assessed, from both experimental and theoretical point of view. Starting from the characteristic nanoscale transport phenomena occurring at the particle-fluid interface, a comprehensive review of the influence of geometrical (particle shape, size and volume concentration), physical (temperature) and chemical (particle material, pH and surfactant concentration in the base fluid) parameters on the nanofluid properties was carried out. Particular focus was devoted to highlight the advantages of using nanofluids as coolants for automotive heat exchangers, and a number of design guidelines was suggested for balancing thermal conductivity and viscosity enhancement in nanofluids. This Review may contribute to a more rational design of the thermo-physical properties of particle suspensions, therefore easing the translation of nanofluid technology from small-scale research laboratories to large-scale industrial applications

Тоғызқұмалақ ойыны: шығу тарихы, дамуы және қазіргі замандағы жай-күйі

Қазақ халқы сан ғасырлар бойы түрлі қиындықтарды басынан өткергендігіне қарамастан, өз мәдениетін дамытуға көп көңіл бөлді. Ата-бабаларымыз әсіресе терең логикалық ойлауды, тапқырлықты талап ететін интеллектуалдық ойындарды дамытуға басымдық жасады. Солардың бірі – «көшпелілер алгебрасы» саналатын тоғызқұмалақ ойыны. Ұлттық ойынның дамуы мен таралуына әр тарихи кезеңнің өзіндік әсері болды. Әсіресе еліміздің тәуелсіздікке қол жеткізуі тоғызқұмалақ ойынының әлемдік деңгейде таралуына мүмкіндік берді. Нәтижесінде тез есептеуге, стратегиялық ойлауға негізделген ұлттық ойын 2020 жылы халықаралық ЮНЕСКО ұйымының Адамзаттың материалдық емес мәдени мұраларының репрезентативтік тізіміне енді. Сондықтан ұсынылып отырған мақалада қазақ халқының ұлттық интеллектуалдық ойыны тоғызқұмалақтың шығу тарихы мен әр түрлі кезеңдердегі даму барысы қарастырылады. Ұлттық ойын бойынша алғашқы чемпионаттың ұйымдастырылуы, республикалық және халықаралық деңгейдегі Тоғыз-құмалақ Федерацияларының құрылуы, тұңғыш спорт шеберлерінің шығуы туралы маңызды деректер беріледі. Ғылыми жұмыста тоғызқұмалақ ойынының ерекшелігі, жалпы құндылығы, маңыздылығы сипатталады. Сонымен қатар ұлттық ойынның қазіргі замандағы жай-күйі, халықаралық деңгейде насихатталуы да жан-жақты зерделенеді

Carbon and Silicon Nanomaterials for Medical Nanotechnology Applications

This dissertation focuses on the development of sp2-carbon- and silicon-based nanomaterials for medical diagnostics and in vivo magnetic field-guided delivery applications. To realize these applications, especially for the development of new in vivo Magnetic Resonance Imaging (MRI) contrast agents (CAs), high solubility in aqueous media is required. Therefore, this work first details development of a new non-covalent method for the preparation of stable aqueous colloidal solution of surfactant-free sp2-carbon nanostructures, as well as a second rapid covalent functionalization procedure to produce highly-water-dispersible honey-comb carbon nanostructures (ca. 50 mg/mL). Next, highly-water-dispersible graphene nanoribbons and Gd3+ ions were together used to produce a high-performance MRI CA for T1- and T2- weighted imaging. In terms of its relaxivity (r1,2) values, this new CA material outperforms currently-available clinical CAs by up to 16 times for r1 and 21 times for r2. Finally, sub-micrometer discoidal magnetic nanoconstructs have been produced and studied for applications for in vivo magnetic-field-guided delivery into cancerous tumors. The nanoconstructs were produced by confining ultra-small superparamagnetic iron oxide nanoparticles (USPIOs) within mesoporous silicon which produced T2-weighted MRI CA performance 2.5 times greater than for the free USPIOs themselves. Moreover, these nanoconstructs, under the influence of an external magnetic field, collectively cooperated via a new mechanism to amplify accumulation in melanoma tumors of mice. Overall, the results of this dissertation could aid in the rapid translation of these nanotechnologies into the clinic, while, hopefully, also serving as an inspiration for continued research into the field of Medical Nanotechnology

Dynamic Adsorption of Functionalized Zwitterionic Copolymers on Carbonate Surfaces under Extreme Reservoir Conditions

© The injection of aqueous polymer solutions into reservoirs for enhanced oil recovery has attracted considerable interest in the petroleum industry. Polymers increase the viscosity of the fluids and thereby improve the volumetric sweep efficiency. However, significant polymer retention in reservoirs by adsorption to surfaces limits the propagation through the reservoir and can reduce the efficiency of the polymer flooding. To explore the structure-property relationships that can direct improvements in future polymer designs, we have investigated the dynamic adsorption of a model system of five zwitterionic copolymers using a quartz crystal microbalance with dissipation and core-flooding experiments at high temperatures and salinities. The results indicate that the degree of dynamic polymer retention is sensitive to a low percentage of functional comonomers on the polymer backbone. The concept of using a small fraction of comonomers to tune the adsorption of polymers is an attractive cost-effective method for modifying the properties of the polymers employed in the oil and gas industry

Brine-soluble zwitterionic copolymers with tunable adsorption on rocks

Injection of aqueous fluids into reservoirs as an enhanced oil recovery (EOR) tool has been of great interest in petroleum engineering. EOR using viscous polymer solutions improves the volumetric sweep efficiency. However, significant polymer adsorption on reservoir rock surfaces is one of the greatest challenges in polymer-flooding EOR. We have synthesized and characterized five zwitterionic copolymers and studied their static adsorption on limestone surfaces in seawater at high temperatures and salinities. Our results indicate that polymer adsorption directly correlates to a small percentage of functional co-monomers on the polymer backbone. One particular copolymer shows negligible static adsorption on limestone surfaces. ©2019 keywords: zwitterionic; copolymer; free-radical polymerization; tunable adsorptio

Geometrical confinement of Gd(DOTA) molecules within mesoporous silicon nanoconstructs for MR imaging of cancer

Porous silicon has been used for the delivery of therapeutic and imaging agents in several biomedical applications. Here, mesoporous silicon nanoconstructs (SiMPs) with a discoidal shape and a sub-micrometer size (1,000 × 400 nm) have been conjugated with gadolinium-tetraazacyclododecane tetraacetic acid Gd(DOTA) molecules and proposed as contrast agents for Magnetic Resonance Imaging. The surface of the SiMPs with different porosities – small pore (SP: ~ 5 nm) and huge pore (HP: ~ 40 nm) – and of bulk, non-porous silica beads (1,000 nm in diameter) have been modified with covalently attached (3-aminopropyl)triethoxysilane (APTES) groups, conjugated with DOTA molecules, and reacted with an aqueous solution of GdCl3. The resulting Gd(DOTA) molecules confined within the small pores of the Gd-SiMPs achieve longitudinal relaxivities r1 of ~ 17 (mM·s)−1, which is 4 times greater than for free Gd(DOTA). This enhancement is ascribed to the confinement and stable chelation of Gd(DOTA) molecules within the SiMP mesoporous matrix. The resulting nanoconstructs possess no cytotoxicity and accumulate in ovarian tumors up to 2% of the injected dose per gram tissue, upon tail vein injection. All together this data suggests that Gd-SiMPs could be efficiently used for MR vascular imaging in cancer and other diseases