Publications by Year: 2006

Kamyshny A, Magdassi S. Microencapsulation. In: PS D Encyclopedia of Surface and Colloid Science. Taylor & Francis ; 2006.
Williams R, Peisajovich SG, Miller OJ, Magdassi S, Tawfik DS, Griffiths AD. Amplification of complex gene libraries by emulsion PCR. Nat. MethodsNature Methods. 2006;3 (7) :545 - 550.Abstract
The efficient amplification of genomic libraries, cDNA libraries and other complex mixts. of genes by PCR is impeded by two phenomena: firstly, short fragments tend to be amplified in preference to larger ones; and, secondly, artifactual fragments are generated by recombination between homologous regions of DNA. Recombination in this case occurs when a primer is partially extended on one template during one cycle of PCR and further extended on another template during a later cycle. Thus, chimeric mols. are generated, the short ones of which are then preferentially amplified. A variety of PCR protocols have been proposed to minimize these problems, most of which rely on high template concns. and low nos. of PCR cycles. Clearly, however, such an approach is not viable if little template DNA is available. Here we describe a protocol for amplifying complex DNA mixts., based on the compartmentalization of genes in a water-in-oil (w/o) emulsion. Template fragments are segregated in the minute aq. droplets of the emulsion and amplified by PCR in isolation. This approach alleviates the problems described above while enabling the use of small amts. of template DNA and high nos. of PCR cycles. Box 1 described an alternative method for generating very stable emulsions for emulsion PCR using the surfactant ABIL EM 90. [on SciFinder(R)]
Magdassi S, Kamyshny A, Aviezer S, Grouchko M.; 2006. Aqueous-based dispersions of metal nanoparticles for use in conductive inks.Abstract
The invention relates to a method for prepg. an aq.-based dispersion of metal nanoparticles comprising: (a) pre-reducing a metal salt suspension by a H2O sol. polymer capable of metal redn. to form a metal nuclei; and (b) adding a chem. reducer to form metal nanoparticles in dispersion. The invention further relates to aq.-based dispersions of metal nanoparticles, and to compns. such as inks comprising such dispersions. [on SciFinder(R)]
Steinberg D, Magdassi S, Kamyshny A, Zegerman H, Letzter A.; 2006. A chewing gum for preventing tooth decay.Abstract
Organoleptically acceptable chewing gums (composed of a gum base, at least one edible acid, and optionally other ingredients) are characterized by high adherence to plaque bacteria. Thus, a ratio between gum base and malic acid of 60:1.8 may be used. A method for prepg. the chewing gum includes triturating a coloring agent (e.g., carmoisine). A method for com. producing and marketing the chewing gums includes testing the chewing gums for adhesion to bacteria, such as plaque bacteria. [on SciFinder(R)]
Miller OJ, Bernath K, Agresti JJ, Amitai G, Kelly BT, Mastrobattista E, Taly V, Magdassi S, Tawfik DS, Griffiths AD. Directed evolution by in vitro compartmentalization. Nat. MethodsNature Methods. 2006;3 (7) :561 - 570.Abstract
The goal of in vitro compartmentalization (IVC) is to divide a large reaction between many microscopic compartments. This technique was first developed to generate "artificial cells" for the directed evolution of proteins. Typically, an aq. soln. of genes and an in vitro transcription-translation system is stirred (or homogenized) into an oil-surfactant mixt. to create a water-in-oil (w/o) emulsion with -1010 aq. droplets per mol of emulsion. The majority of droplets contain no more that a single gene along with all of the mol. machinery needed to express that gene. The expressed proteins and the products of their catalytic activities cannot leave the droplets, and so genotype is coupled to phenotype in vitro, making it possible to select very large libraries of genes (108-1011 genes). We describe the advantages and applications of IVC. A protocol for performing a directed evolution expt. by IVC makes use of one or more w/o emulsions. This procedure involves the generation of a gene library, the performance of a selection, and the subsequent recovery of the selected genes by PCR. We also describe two procedures for converting w/o emulsions to water-in-oil-in-water (w/o/w) emulsions for high-throughput screening using a fluorescence-activated cell sorter (FACS). Finally, we describe two methods for delivering substrates, regulators and other compds. to the preformed aq. droplets of w/o emulsion. [on SciFinder(R)]
Tawfik D, Bernath K, Magdassi S, Peisajovich SG.; 2006. Directed evolution of protein inhibitors of DNA-nucleases by in vitro compartmentalization (IVC) and nano-droplet delivery.Abstract
The present invention provides an in vitro system for compartmentalization of large mol. libraries and provides methods for selection and isolation of mols. having desired activities from such libraries. The present invention provides novel and inventive applications of IVC for the selection of mols. being capable of modulating a particular activity of a known biol. active moiety, including, but not limited to an enzyme. The inventors of the present invention utilize a micelle delivery system that enables the transport of various solutes, including metal ions, into the emulsion droplets thereby inducing a desired activity of the known biol. active moiety or of the gene product. The present invention is based ion part on the unexpected finding that an IVC system can be used for directed evolution of nuclease inhibitors. In vitro compartmentalization (IVC) uses water-in-oil emulsions to create artificial cell-like compartments in which genes can be individually transcribed and translated. Here, the inventors present a new application of IVC for the selection of DNA-nuclease inhibitors. They developed a nano-droplets delivery system that allows the transport of various solutes, including metal ions, into the emulsion droplets. This transport mechanism was used to regulate the activity of colicin nucleases that were co-compartmentalized with the genes, so that the nucleases were activated by nickel or cobalt ions only after the potential inhibitor genes have been translated. They demonstrated its utility by selecting libraries of the gene encoding the cognate inhibitor of colicin E9 (immunity protein 9, or Im9) for inhibition of another colicin (ColE7). The in vitro evolved inhibitors show significant inhibition of ColE7 both in vitro and in vivo. These Im9 variants carry mutations into residues that det. the selectivity of the natural counterpart (Im7) while completely retaining the residues that are conserved throughout the family of immunity protein inhibitors. [on SciFinder(R)]
Sen T, Magdassi S, Nizri G, Bruce IJ. Dispersion of magnetic nanoparticles in suspension. Micro Nano Lett.Micro & Nano Letters [Internet]. 2006;1 (1) :39 - 42. Publisher's VersionAbstract
Pure magnetite nanoparticles (Fe3O4) have been synthesized in water by copptn. using two different approaches (from ferrous sulfate and a mixt. of ferrous and ferric chlorides). All materials aggregated in aq. suspension, but their subsequent dispersion on treatment with a variety of agents was obsd. to be different. Magnetite produced using ferrous sulfate could not be disaggregated, whereas magnetite produced from a mixt. of ferrous and ferric chlorides could be disaggregated to a quasi-monodispersed form. The dispersing agents were tetra-Me ammonium hydroxide, Disperbyk 190 and polyacrylic acid. The finding has potentially important implications for the surface activation of superparamagnetic magnetite nanoparticles and their ability to be used in bio/life science applications. [on SciFinder(R)]
Garbar A, Lekhtman D, De la Vega F, Magdassi S, Kamyshny A, Kahana F.; 2006. Ink jet printable compositions.Abstract
Ink jet printable compns. that include nano metal powders in a liq. carrier are described for printing elec. conductor patterns. These compns. have high metal nanopowder concns. and low viscosities. [on SciFinder(R)]
Magdassi S, Kamyshny A, Grouchko M. Making connections. Aqueous dispersions of silver nanoparticles form conductive inkjet inks. Eur. Coat. J.European Coatings Journal. 2006;(11) :54, 56, 58-59.Abstract
Nanoparticles of metals having high elec. cond. offer new scope for direct digital printing of conductive patterns. Stable aq. silver nanoparticle dispersions were synthesized by chem. redn. These were suitable for inkjet printing, with the dried inks sintering at temps. as low as 160°. However, the resistance remained much higher than that of metallic silver. [on SciFinder(R)]
Magdassi S, Vinetsky Y.; 2006. Production of nanoemulsions for improving light fastness of inks.Abstract
A nanoemulsion useful for improving light-fastness of water-based inks comprises nanodroplets of UV stabilizer in water, wherein the nanodroplets comprise (a) water-immiscible liq. phase, which is a UV stabilizer or a mixt. of UV stabilizers, (b) submicron solid particles of at least one UV stabilizer dispersed within said nanodroplets, and wherein the av. size of the droplets is < 350 nm. The nanoemulsion may further comprise one or more light fastness agents selected from UV absorbers, UV blockers, antioxidants, singlet oxygen quenchers, super oxide anion quenchers, ozone quenchers, visible light absorbers, or IR absorbers. [on SciFinder(R)]