Electrophoresis in lyotropic polymer liquid crystals

Rill, Randolph L.; Locke, Bruce R.; Liu, Yingjie; Winkle, David H. Van

doi:10.1073/pnas.95.4.1534

Cited by 91 publications

(103 citation statements)

References 32 publications

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“…The consequent gelation of Pluronic by hierarchical selfassembly is maintained in the presence of both unbound and Pluronic-conjugated proteins. If, under the current synthetic conditions, the micelles in the amphiphilic Pluronic block copolymers self-assemble into hierarchical architectures, [34][35][36] they could presumably act in a manner similar to that of the mms6-containing bacterial phospholipid membranes, allowing a surfacecontrolled crystal growth. Both unbound forms of mms6 are likely to phase-separate from the gel into the water-rich regions of the gels, being expelled from the micelles.…”

Section: Resultsmentioning

confidence: 99%

Cobalt Ferrite Nanocrystals: Out-Performing Magnetotactic Bacteria

et al. 2007

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Magnetotactic bacteria produce exquisitely ordered chains of uniform magnetite (Fe3O4) nanocrystals, and the use of the bacterial mms6 protein allows for the shape-selective synthesis of Fe 3O4 nanocrystals. Cobalt ferrite (CoFe2O 4) nanoparticles, on the other hand, are not known to occur in living organisms. Here we report on the use of the recombinant mms6 protein in a templated synthesis of CoFe2O4 nanocrystals in vitro. We have covalently attached the full-length mms6 protein and a synthetic C-terminal domain of mms6 protein to self-assembling polymers in order to template hierarchical CoFe2O4 nanostructures. This new synthesis pathway enables facile room-temperature shape-specific synthesis of complex magnetic crystalline nanomaterials with particle sizes in the range of 40 -100 nm that are difficult to produce using conventional techniques. KeywordsAmes laboratory, biochemistry biophysics and molecular biology, physics and astronomy, bioinspired synthesis, biomineralization protein, templating, superparamagnetism, magnetic nanocrystals, cobalt ferrite nanocrystals T he synthesis of magnetic nanoparticles with narrow size distribution represents a significant practical and fundamental challenge.1,2 Such particles are in high demand in various areas, from quantum computing to cancer therapy. [3][4][5][6][7][8][9][10][11][12] Contrary to common sense, the smallest nanoparticles are not necessarily the best. Often, larger particles (ϳ50 nm), just below the superparamagnetic threshold, are the most suitable for many applications. For example, in magnetic recording and drug delivery, larger particles with large magnetic moments are preferred.13-16 The problem is not only the particle size but also significant agglomeration of the particles. It is especially difficult to produce non-agglomerated nanocrystals of ferromagnetic nanoparticles. 17 Various synthetic approaches have been utilized, ranging from homogeneous synthesis 18 to heterogeneous synthesis 2 and to the use of powerful ultrasound to rapidly decompose volatile organometallics.19-21 One of the drawbacks associated with rapid synthesis is a decreased degree of crystallinity in the resulting material leading, in turn, to a significant spin misalignment, which reduces the total or net magnetic moment per particle. When the synthesis involves a more controlled thermal decomposition, it is possible to somewhat further minimize the crystallinity problems. 1,17In this article we describe a novel roomtemperature bioinspired route to produce nanocrystals of one of the best known, commercially used ferromagnetic compounds: cobalt ferrite. The idea arose from our investigations of magnetite biomineralization by various magnetotactic bacteria. 22 We investigated the ability of the acidic recombinant protein, mms6, cloned from these bacteria, to promote shape-specific magnetite growth in vitro. 23 These experiments were successful and yielded uniform magnetite nanocrystals, resembling those seen in magnetotactic bacteria, as shown in Figure 1.In addition...

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Section: Resultsmentioning

confidence: 99%

Cobalt Ferrite Nanocrystals: Out-Performing Magnetotactic Bacteria

et al. 2007

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“…Pluronic copolymers possess a unique viscosity-adjustable property, which renders PF127 gels easy to handle compared to conventional crosslinked hydrogels based on, amongst others, poly(vinyl alcohol), gelatin, and poly (N-isopropylacrylamide). [36,37] As an example, PF127 aqueous solutions (18-30% (w/v)) appear to be fluid at low temperatures (0-5 8C), and can transform into a gel-like cubic liquid crystal within a few seconds when heated. [38][39][40] Such a fast sol-gel transition renders PF127 gels particularly useful as an injectable vehicle for local delivery of various therapeutic agents.…”

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confidence: 99%

“…In comparison, SPEL features a temperature-dependant reversible sol-gel transition. Since this transition temperature can be adjusted by varying the concentration of PF127, [36,37] it is possible to apply SPEL as an injectable drug-delivery system for magnetically modulated release of hydrophobic bioactive agents on pathological sites.…”

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confidence: 99%

Injectable Superparamagnetic Ferrogels for Controlled Release of Hydrophobic Drugs

et al. 2009

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A ferrogel for magnetically controlled release of drugs is prepared by integration of superparamagnetic iron oxide nanoparticles and Pluronic F127 gels. The hydrophobic drug indomethacin is loaded in the ferrogel owing to the oil‐in‐water micellar structure. The characteristic sol–gel transition property renders the ferrogel an injectable drug carrier that will be, in principle, free from surgical implant procedure.

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“…Indeed, no major improvements in either sequencing readlength or elution times have been reported that can be directly related to a revolution in sieving matrices. We must add, however, that in some cases, the separation process is probably novel and remains to be investigated [3,4].…”

Section: Introductionmentioning

confidence: 99%

Theory of DNA electrophoresis (∼ 1999 –2002 ½)

et al. 2002

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Over the last two decades, the introduction of new methods such as pulsed-field gel electrophoresis and capillary array electrophoresis has made it possible to map and sequence entire genomes, including our own. The development of these experimental methods has been helped by the progress of theoretical and computational sciences, and the interactions between these three modi operandi of modern science are still pushing the limits of our technologies. We now see a clear trend towards proteomics and microfluidic (even nanofluidic!) devices. In this review, we take a look at the progress of the field over the last 3 years using the glasses of the theoretical scientist and focusing mostly on new ideas and concepts. About a dozen different subfields are discussed and reviewed. We conclude by giving a commented list of some of the best review articles published over the last 2-3 years.

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Electrophoresis in lyotropic polymer liquid crystals

Cited by 91 publications

References 32 publications

Cobalt Ferrite Nanocrystals: Out-Performing Magnetotactic Bacteria

Cobalt Ferrite Nanocrystals: Out-Performing Magnetotactic Bacteria

Injectable Superparamagnetic Ferrogels for Controlled Release of Hydrophobic Drugs

Theory of DNA electrophoresis (∼ 1999 –2002 ½)

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