Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2002-03-25
2004-12-21
Le, H. Thi (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C427S002100, C427S128000, C427S189000, C427S190000, C427S212000, C428S900000
Reexamination Certificate
active
06833192
ABSTRACT:
The invention refers to a new process for preparing coated crystals by coating crystal template particles with alternating layers of oppositely charged polyelectrolytes and/or nanoparticles.
The area of thin film fabrication, in which ordered, functional supramolecular structures are the chief goal, has been greatly impacted by the recent introduction of the layer-by-layer (LbL) self-assembly technique (Decher, Science 1997, 277, 1232). The LbL method permits the fabrication of multilayer thin film assemblies on solid supports by the spontaneous sequential adsorption of oppositely charged species from dilute aqueous solutions onto charged substrates. The driving force for the multilayer film build-up is primarily due to the electrostatic attraction and complex formation between the charged species deposited. The LbL approach was initially employed to construct multilayer films of polyelectrolytes (Decher, Science 1997, 277, 1232), and subsequently extended to include proteins (Lvov et al, J. Am. Chem. Soc. 1995, 117, 6117; Onda et at, T. Biotech. Bioeng. 1996, 51, 163; Caruso et al, Langmuir 1997, 13, 3427), nucleic acids (Decher et al, J. Biosens. Bioelectron. 1994, 9, 677; Sukhorukov et al, Thin Solid Films 1996, 284/285, 220; Caruso et al, Anal. Chem. 1997, 69, 2043), dyes (Araki et al, Langmuir 1996, 12, 5393; Yoo et al, Synthetic Metals 1997, 85, 1425; Ariga et al, J. Am. Chem. Soc. 1997, 119, 2224), dendrimers (Tsukruk et al, Langmuir 1997, 13, 2171), and various inorganic nanoparticles (Kleinfeld et al, Science 1994, 265, 370; Keller et al, J. Am. Chem. Soc. 1994, 116, 8817; Kotov et al, J. Am. Chem. Soc. 1997, 119, 6821; Kotov et al, J. Phys. Chem. 1995, 99, 13065; Feldheim et al, J. Am. Chem. Soc. 1996, 118, 7640; Schmitt et al, Adv. Mater 1997, 9, 61; Lvov et al, Langmuir 1997, 13, 6195) in polyelectrolyte multilayer assemblies by replacing one of the polyions by a similarly charged species.
The vast majority of studies concerning the LbL technique have employed macroscopically flat charged surfaces as substrates for multilayer film formation. For example, U.S. Pat. No. 5,716,709 describes multilayered nanostructures comprising alternating organic and inorganic ionic layers on a flat substrate, such as a silicon wafer. Recently, Keller et al reported the preparation of alternating composite multilayers of exfoliated zirconium phosphate sheets and charged redox polymers on (3-aminopropyl)-triethoxysilane-modified silica particles (Keller et al, J. Am. Chem. Soc. 1995, 117, 12879).
In more recent studies (Caruso et al., Macromolecules, 1999, 32, 2317; Caruso et al., J. Phys. Chem. B. 1998, 102, 2011; Sukhorukov et al., Colloids Surf. A: Physicochem.Eng.Aspects 1998, 137, 253), the LbL approach was successfully applied to utilise submicron- and micron-sized charged colloidal particles as the adsorbing substrates to produce colloid-supported polyelectrolyte multilayer films: regular step-wise polyelectrolyte multilayer growth was observed on the colloids.
Considerable scientific effort has focussed on the fabrication of composite micro- and nanoparticles that consist of either organic or inorganic cores coated with shells of different chemical composition (Kawahashi and Matijevic, J.Colloid Interface Sci. 1991, 143, 103; Garg and Matijevic, J.Colloid Interface Sci. 1988, 126; Kawahashi and Matijevic, J.Colloid Interface Sci. 1990, 138, 534; Ohmori and Matijevic, J.Colloid Interface Sci. 1992, 150, 594; Giersig et al., Adv. Mater. 1997, 9, 570; Liz-Marzan et al., Langmuir 1996, 12, 4329; Liz-Marzan et al., J.Chem.Soc.Chem.Commun. 1996, 731; Giersig et al., Ber.Bunsenges.Phys.Chem. 1997, 101, 1617; Correa-Duarte et al., Chem.Phys.Lett. 1998, 286, 497; Bamnolker et al., J.Mater.Sci.Lett. 1997, 16, 1412; Margel and Weisel, J.Polym.Sci.Chem.Ed. 1984, 22, 145; Philipse et al., Langmuir 1994, 10, 92). These core-shell particles often exhibit properties which are significantly different to those of the templated core (e.g. different surface chemical composition, increased stability, higher surface area, as well as different magnetic and optical properties), thus making them attractive both from a scientific and technological viewpoint. Applications for such particles are diverse, ranging from capsule agents for drug delivery, catalysis, coatings, composite materials, as well as for protecting senstitive agents such as enzymes and proteins. Previous investigations have demonstrated that polymeric microparticles and inorganic cores can be coated with uniform layers of various materials, including silica, yttrium basic carbonate, zirconium hydrous oxide, either by controlled surface precipitation reactions on the core particles, or by direct surface reactions.
U.S. Pat. No. 5,091,187 discloses the coating of micro-crystals with phospholipids. EP-A-0 516 252 discloses the coating of nanocrystalline-magnetic particles with natural or synthetic glycosamino-glucans which may be selected from chondroitin-sulphate, dermatan-sulphate, heparan-sulphate, heparin and analogs thereof.
U.S. Pat. No. 5,705,222 discloses a process for preparing composite particle dispersions wherein a plurality of core particles is dispersed in a first solution wherein the core particles do not irreversibly self-flocculate, an amount of polymer is added to the dispersion of core particles, wherein the polymer has an affinity for the dispersed core particles and the excess polymer is removed by a solid/liquid separation process, i.e. centrifugation or decanting.
In DE 198 12 083.4 it was suggested that soluble colloidal cores can be used as templates for the sequential deposition of polyelectrolytes to fabricate novel three-dimensional hollow polymer shells. From PCT/EP99/01854 the preparation of coated capsules and hollow shells by coating colloidal particles with alternating layers of oppositely charged nanoparticles and polyelectrolytes is known. DE 199 075 52.2 discloses a process for preparing capsules having a polyelectrolyte shell wherein the template particles are selected from aggregates of biological and/or amphiphilic materials such as cells, cell aggregates, subcellular particles, virus particles and aggregates of biomolecules.
The coating of biocrystals, however, represents several challenges which are not applicable when templating other solid core particles including biological templates. First, the crystals are formed under delicate solution conditions, hence suitable conditions have to be found which facilitate polymer multilayer deposition on the crystal surface and do not destroy the crystal morphology (i. e. to avoid its solubilization), and second, the permeability of the polymer capsule walls must be such that it permits encapsulation of the bio-crystal. In addition, since the primary usefulness of biological molecules is their biological function, their activity should be preserved when encapsulated.
Herein we report sucessful coating of crystals, e. g. bio-crystals by depositing alternating layers of oppositely charged polyelectrolytes and/or nanoparticles on crystal template particles via the sequential electrostatic adsorption of polyelectrolyte and/or nanoparticles from solution. Functional biomolecules are obtainable after solubilization within the polyelectrolyte
anoparticle shell and/or after removal of the shell.
Thus, a first aspect of the present invention is a process for preparing coated crystals comprising the steps:
(a) providing a dispersion of crystal template particles in a solvent and
(b) coating said particles with a multilayer comprising alternating layers of oppositely charged polyelectrolytes and/or nanoparticles. Suitable crystal template particles are particles of crystallized substances. Preferably the crystals are particles of crystallized organic compounds and/or particles of crystallized biomolecules (bio-crystals) (including molecules which occur in living organisms and/or which influence the metabolism of living organisms). E. g. the crystals may be selected from crystals of proteins, peptides, nucleic acids, lipids, carbohydrates, saccharides, drugs etc., wh
Caruso Frank
Möhwald Helmuth
Renneberg Reinhard
Trau Dieter
Le H. Thi
Max-Planck Gesellschaft Zur Forderrung der Wissenschaften E.V.
Sutherland & Asbill & Brennan LLP
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