Génération des solutions évolutives de métal de très haute-Aspect Ratio nanocomposites dans un milieu liquide biologique
Summary
Ici, nous présentons un protocole à synthétiser de nouveaux, de haute rapport d'aspect biocomposites dans des conditions biologiques et dans des milieux liquides. Les biocomposites échelle du nanomètre au micromètre de diamètre et de la longueur, respectivement. nanoparticules de cuivre (CNPS) et du sulfate de cuivre combinés avec la cystine sont les éléments clés pour la synthèse.
Abstract
L'objectif de ce protocole est de décrire la synthèse de deux nouveaux biocomposites avec des structures de ratio d'aspect élevé-. Les biocomposites sont en cuivre et la cystine, soit avec des nanoparticules de cuivre (CNPS) ou du sulfate de cuivre qui contribue le composant métallique. La synthèse est effectuée dans un liquide dans des conditions biologiques (37 ° C) et la forme des composites auto-assemblées après 24 h. Une fois formés, ces composites sont très stables dans les deux milieux liquides et sous une forme séchée. Les composites échelle du nano aux micro gamme de longueur, et de quelques microns à 25 nm de diamètre. La microscopie électronique à balayage à émission de champ avec une spectroscopie à dispersion d'énergie aux rayons X (EDX) a montré que le soufre était présent dans les structures linéaires NP-dérivés, tandis qu'il est absent de la matière CNP départ, ce qui confirme la cystine en tant que source de soufre dans les nanocomposites finaux . Lors de la synthèse de ces nano et micro-composites linéaires, un large éventail de longueurs de structures est formée dans le récipient de synthèse. La sonication du mélange liquide après la synthèse a été démontrée pour aider à contrôler la taille moyenne des structures en diminuant la longueur moyenne avec l'augmentation du temps de sonication. Étant donné que les structures formées sont très stables, ne pas agglomérer, et sont formées dans la phase liquide, la centrifugation peut également être utilisée pour aider à concentrer et séparer les composites formés.
Introduction
Copper is a highly reactive metal that in the biological world is essential in some enzyme functions 1,2, but in higher concentrations is potently toxic including in the nanoparticulate form 3,4. Concern over copper toxicity has become more relevant as CNPs and other copper-based nanomaterials are utilized, due to the increased surface area/mass for nanostructures. Thus, even a small mass of copper, in nanoparticle form, could cause local toxicity due to its ability to penetrate the cell and be broken down into reactive forms. Some biological species can complex with and chelate metal ions, and even incorporate them into biological structures as has been described in marine mussels 5. In studying the potential toxic effects of nanomaterials 4, it was discovered that over time, and under biological conditions used for typical cell culturing (37 °C and 5% CO2), stable copper biocomposites could be formed with a high-aspect ratio (linear) structure.
By a process of elimination, the initial discovery of these linear biocomposites, which occurred in complete cell culture media, was simplified to a defined protocol of essential elements needed for the biocomposites to self-assemble. Self-assembly of two types of highly linear biocomposites was discovered to be possible with two starting metal components: 1) CNPs and 2) copper sulfate, with the common biological component being cystine. Although more complex, so called “urchin” and “nanoflower” type copper-containing structures with nanoscale and microscale features have been previously reported, these were produced under non-biological conditions, such as temperatures of 100 °C or greater 6-8. To our knowledge, synthesis of individual, linear copper-containing nanostructures that are scalable in liquid phase under biological conditions has not been previously described.
One of the starting materials utilized for synthesis of nanocomposites, namely CNPs, has been reported previously to be very toxic to cells 4. It has recently been reported that after the nanocomposites are formed, these structures are less toxic on a per mass basis than the starting NPs 9. Thus, the synthesis described here may be derived from a biological and biochemical reaction that has utility in stabilizing reactive copper species, both in the sense of transforming the NP form into larger structures and in producing composites less toxic to cells.
In contrast to many other nanomaterial forms which are known to aggregate or clump upon interaction with biological liquid media 10,11, once formed, the highly linear composites described here avoid aggregation, possibly due to a redistribution of charge which has been previously reported 9. As detailed in the current work, this avoidance of aggregation is convenient for the purposes of working with the structures once formed for at least 3 reasons: 1) composite structures once formed may be concentrated using centrifugation and then easily dispersed again using vortex mixing; 2) formed structures can be decreased in average size by sonication for different periods of time; and 3) the formed linear structures may provide an additional tool for avoiding the recently described “coffee ring effect” 12 and thus provide a dopant for creating more evenly distributed coatings of materials, especially those containing spherical particulates.
Protocol
Representative Results
Discussion
Alors que l'évaluation des effets toxiques potentiels des nanomatériaux dont CNPS, il a été observé que sur le long terme, PNC ont été transformés à partir d'une distribution de particules initialement plus dispersée à une forme agrégée plus grande (Figure 2). Dans certains cas, ces formations très agrégés qui ont été produites dans le plat de culture cellulaire, dans des conditions biologiques, formés projections très linéaires de l'agrégat central, rappelant cuivre d?…
Disclosures
The authors have nothing to disclose.
Acknowledgements
The authors would like to acknowledge the technical assistance of Alfred Gunasekaran in electron microscopy studies at the Institute of Micromanufacturing at Louisiana Tech University, and Dr. Jim McNamara for assistance with additional microscopy studies. The work described was supported in part by Louisiana board of Regents PKSFI Contract No. LEQSF (2007-12)-ENH-PKSFI-PRS-04 and the James E. Wyche III Endowed Professorship from Louisiana Tech University (to M.D.).
Materials
| Mini Vortexer | VWR (https://us.vwr.com) | 58816-121 | |
| CO2 Incubator Model # 2425-2 | VWR (https://us.vwr.com) | Contact vendor | Current model calalog # 98000-360 |
| Eppendorf Centrifuge (Refrigerated Microcentrifuge) | Labnet (http://labnetinternational.com/) | C2500-R | Model Prism R |
| Cell Culture Centrifuge Model Z323K | Labnet (http://labnetinternational.com/) | Contact vendor | Current model Z206A catalog # C0206-A |
| Sonicator (Ultrasonic Cleaner) | Branson Ultrasonics Corporation (http://www.bransonic.com/) | 1510R-MTH | |
| Balance | Sartorius (http://dataweigh.com) | Model CP225D similar model CPA225D | |
| Olympus IX51 Inverted Light Microscope | Olympus (http://olympusamerica.com | Contact vendor | |
| Olympus DP71 microscope digital camera | Olympus (http://olympusamerica.com | Contact vendor | |
| external power supply unit- white light for Olympus microscope | Olympus (http://olympusamerica.com | TH4-100 | |
| 10x, 20, and 40x microscope objectives | Olympus (http://olympusamerica.com | Contact vendor | |
| Scanning Electron Microscope | Hitachi (http://hitachi-hitec.com/global/em/sem/sem_index.html) | model S-4800 | |
| Transmission Electron Microscope | Zeiss (http://zeiss.com/microscopy/en_de/products.html) | model Libra 120 | |
| Table Top Work Station Unidirectional Flow Clean Bench | Envirco (http://envirco-hvac.com) | model PNG62675 | Used for sterile cell culture technique |
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