Abstract: This invention relates to the process for the preparation of polyurethane with controlled particle size and shape. More, particularly it relates to the production of polyurethane microspheres from a diol and diisocyanate by dispersion polymerization in presence of a steric stabilizer and a catalyst in an organic solvent at a controlled temperature, and finally separating the spherical polyurethane particles from the reaction mixture by conventional means.

Abstract: Disclosed herein are novel electrophoretic displays and materials useful in fabricating such displays. In particular, novel encapsulated displays are disclosed. Particles encapsulated therein are dispersed within a suspending, or electrophoretic, fluid. This fluid may be a mixture of two or more fluids or may be a single fluid. The displays may further comprise particles dispersed in a suspending fluid, wherein the particles contain a liquid. In either case, the suspending fluid may have a density or refractive index substantially matched to that of the particles dispersed therein. Finally, also disclosed herein are electro-osmotic displays. These displays comprise at least one capsule containing either a cellulosic or gel-like internal phase and a liquid phase, or containing two or more immiscible fluids. Application of electric fields to any of the electrophoretic displays described herein affects an optical property of the display.

Abstract: The present invention is directed to charged lipids, compositions comprising charged lipids, and the use of these compositions in drug delivery, targeted drug delivery, therapeutic imaging and diagnostic imaging, as well as their use as contrast agents.

Abstract: The invention disclosed relates to a nanofiltration composite membrane that is solvent and pH stable and may be used to separate at least one dissolved or suspended component from a liquid phase, including(a) a substrate ultrafiltration membrane formed from an ethylenically unsaturated nitrile, such as acrylonitrile and substituted acrylonitrile polymers, and(b) a coating of a hydrophilic polymer containing reactive functional groups.Preferably, the reactive functional groups described in (b) are subjected to a post-coating cross-linking reaction with a substantially non-cytotoxic cross-linking agent such as bi-functional aldehydes. A method for the preparation of such composite membranes is also disclosed.

Abstract: A polysulfone membrane for purifying blood having excellent compatibility with blood and the process producing the membrane are disclosed. The membrane comprises a mixed polymer phase of a graft copolymer and/or block copolymer having a molecular weight of 3.times.10.sup.5 daltons or more and comprising (A) a hydrophilic segment and (B) a hydrophobic segment (exclusive of polysulfone) in a total amount of from 0.5 to 30 parts by weight per 100 parts by weight of polysulfone, with the monomer unit ratio (A/B) between the segments A and B being from 0.5 to 5. The copolymer is preferably a graft copolymer where the hydrophilic segment is a polyvinylpyrrolidone segment and the hydrophobic segment is a polystyrene segment. The membrane can be prepared by applying a wet film formation process to a dope containing an appropriate solvent of the mixed polymer, such as N,N-dimethylacetamide.

Abstract: Highly asymmetric polymeric membranes with large pores which yield bubble points in the range of 0.5 to 25 psid and superior flow characteristics. The membranes can be cast from both metastable dispersions and from homogenous casting formulations. The technique of synthesis involves exposure of the cast membrane to humid air to create large surface pores on the exposed side.

Abstract: This invention relates to a novel Solvent Extraction and Direct Hydration (SEDH) method for preparing lipid-nucleic acid particles which are useful for the introduction of nucleic acids (e.g., plasmid DNA, antisense molecules, ribozymes, etc.) into cells. The lipid-nucleic acid particles prepared using the methods of the present invention have enhanced circulation characteristics and serum stability and, thus, they are extremely effective as nucleic acid delivery vehicles.

Abstract: A liposome composition containing encapsulated compound in stable precipitated form, and a method for producing the composition, are disclosed. The concentration of precipitated compound within the liposomes is severalfold higher than that in the bulk medium, and the concentration of compound within the liposomes is not reduced in the presence of a proton or alkali metal-ion ionophore added to the suspension.

Abstract: Gas-containing microcapsules useful as imaging agents, e.g. as ultrasound contrast agents, may be prepared by forming a dispersion of gas microbubbles in an aqueous medium comprising a solution or dispersion of a wall-forming material and subsequently inducing direct microencapsulation of these microbubbles by the wall-forming material.

Abstract: The present invention relates to a breathable, oriented microporous elastomeric film. The present invention also relates to a process for forming the breathable film including the step of stretching a filled film to produce a microporous film layer.

Abstract: The present invention relates to the field synthetic polymeric membrane materials formed from casting polyvinylidene difluoride (PVDF) polymer solutions and/or dispersions. Membranes formed in accordance with the present invention are all highly porous. Both internally isotropic membranes and highly asymmetric PVDF membranes are disclosed. The membranes of the invention are useful in a variety of microfiltration and ultrathin applications.

Abstract: Disclosed is a method for making liposomes, for example multivesicular liposomes (MVLs), containing one or more biologically active agents, wherein the loading of the active agents into the liposomes is modulated by adjusting the osmolarity of the aqueous component into which the agents are dissolved prior to encapsulation. To increase the loading of the active agent, the osmolarity of the aqueous component is reduced, and to decrease the loading of the active agent, the osmolarity of the aqueous component is increased. In the making of MVLs, the process involves dissolving the active agent and an optional osmotic excipient in a first aqueous component encapsulated within the liposomes. For any given concentration of drug, the osmolarity of the first aqueous component can be adjusted by increasing or decreasing the concentration or molecular weight of the osmotic excipients used therein.

Abstract: Provided are microcapsules enclosing therein a magnetic fluid, which are useful for imparting sound-absorbing and insulating ability to building materials, etc. by incorporation thereinto or adhesion thereto by means of an adhesive, and processes for producing the microcapsules. The heat-expandable microcapsule of the present invention comprises (i) a shell composed of a thermoplastic resin and (ii) a magnetic fluid which is a dispersion of magnetic substance fine particles having an average particle diameter of 5-200 nm in a hydrophobic organic solvent and a hydrophobic liquid foaming agent, both enclosed in the shell. The hollow microcapsule of the present invention comprises (i) a shell composed of a thermoplastic resin, and (ii) a magnetic fluid which is a dispersion of magnetic substance fine particles having an average particle diameter of 5-200 nm in a hydrophobic organic solvent and a vacant cell both included in the shell.

Abstract: Respective hollow fiber membranes suitable for use in removing undesired contaminants from blood, in particular in an artificial kidney, have:(1) per membrane area of 1.8 m.sup.2, in vitro clearances for urea and phosphorus respectively of .gtoreq.195, and .gtoreq.180, ml/min, a .beta..sub.2 -microglobulin clearance .gtoreq.44 ml/min and an albumin permeability .ltoreq.0.5%;(2) an albumin permeability .ltoreq.1.5% and an overall mass transfer coefficient Ko .gtoreq.0.0012 cm/min; and(3) a vitamin B.sub.12 dialyzance of .gtoreq.135 ml/min and an albumin permeability .ltoreq.3%. The membranes can be prepared by spinning hollow fibers from a spinning solution comprising a polysulfone, a hydrophilic polymer, a solvent and water, the spinning solution having a viscosity x at 30.degree. C. of 25-130 poise and a quantity y % of water given by:-0.01x+1.45.ltoreq.y.ltoreq.-0.01x+2.

Abstract: Multilamellar lipid vesicles are prepared by a two-step method. In the first step, a sterol is completely dissolved in a mixture comprising an aqueous solvent and a surfactant. In the second step, a lipid surfactant is added to a solution resulting from the first step, to prepare a homogeneous lamellar liquid crystal phase or a liquid crystal phase suspension in water. The liquid crystal phase or liquid crystal phase suspension can then be converted into multilamellar lipid vesicles.

Abstract: The invention relates to accurately meterable shaped articles, for example granules or pellets, containing hydrophilic macromolecules, active compounds and optionally further pharmaceutically acceptable structure-forming substances and auxiliaries, the active compound being present in a matrix in dissolved, suspended or emulsified form, and a novel process for the production of these shaped articles, the process being particularly economically and ecologically acceptable, and use of the shaped articles as medicaments, in which the bioavailability, shelf life and tolerability is increased. Using the shaped articles or mixtures according to the invention, intermediates or final products for pharmacy, cosmetics, diagnosis, analysis or dietetics (healthcare) can additionally be advantageously prepared.

Abstract: A process for producing a microencapsulated system comprising the steps of: (a) emulsifying a solution of color precursor in a solvent as a first internal phase and a diluent as a second internal phase in an external phase to produce discrete droplets of each of said first and second phases; and (b) encapsulating said droplets, is disclosed. A recording sheet is also disclosed which comprises a substrate having a layer of microencapsules containing a color precursor solution and microcapsules containing a diluent. Preferably the microcapsules are clusters of gelatin capsules.

Abstract: Disclosed are microcapsules comprising a polymer shell enclosing two or more immiscible liquid phases in which a drug, or a prodrug and a drug activator are partitioned into separate phases, or prevented from diffusing out of the microcapsule by a liquid phase in which the drug is poorly soluble. Also disclosed are methods of using the microcapsules for in situ activation of drugs, where upon exposure to an appropriate energy source the internal phases mix and the drug is activated in situ.

Abstract: Methods for preparing soft gelatin capsules containing fragrances are disclosed. The desired fragrance is dissolved in a solvent system comprising a volatile solvent, a non-volatile cosolvent, or a combination of a volatile solvent and a non-volatile cosolvent or cosolvents. The resulting mixture is then encapsulated between gelatin ribbions prepared with an odor-free gelatin plasticized with a partially dehydrated, hydrogenated glucose syrup.

Abstract: A method of forming magnetized rotating elements for a rotating element display where all the elements are magnetized in the same orientation is provided. First, at least two planar streams of hardenable liquids flowing in substantially the same direction are provided. Each stream has an associated optical modulation characteristic and at least one stream has an associated optical modulation characteristic different from at least one other stream. At least one stream includes a magnetic pigment. The streams are then merged to form a reservoir containing side-by-side amounts of each liquid from each stream. A free jet is then formed containing side-by-side amounts of each liquid from the reservoir. Then a portion of the free jet is passed through a magnetic field which is oriented transverse to the direction of the free jet to magnetize the magnetic pigment. The rotating elements formed can be either spherical in shape or cylindrical in shape.

Abstract: Briefly, in one aspect, the present invention provides puncture resistant microporous materials made of melt-processable semi-crystalline thermoplastic polymers. The microporous materials can be produced at relatively high rates and at low cost. Films and multilayer constructions made of the microporous materials and methods of making microporous materials also are provided.

Abstract: Uniaxially oriented microporous breathable films having exceptional toughness transverse to the direction of orientation are disclosed herein. Such films include a particulate filler and a nonelastic material including a copolymer of ethylene with at least one C.sub.4 -C.sub.8 .alpha.-olefin monomer, such copolymers being described in the trade as "super tough", "next generation", etc., and being prepared with "new" or "improved" catalyst systems or with metallocene or similar single-site catalysts. A method of manufacture is also disclosed.

Abstract: A capsule for encapsulating implantable cells for improving the detectability of electrical signals generated by the cells is provided. The capsule includes a low-conductivity (high electrical resistance) membrane and a semi-permeable (low electrical resistance) membrane. The low-conductivity membrane seals around the circumference of the cell mass between the electrical poles of the capsule, and further extends for increasing the electrical resistance between the poles. The semi-permeable membrane enables nutrients and waste materials to flow to and from the cell mass. The semi-permeable membrane enclosed at least one of the poles of the cell mass, and cooperates with the low-conductivity membrane to completely enclose the cell mass. The low-conductivity membrane may enclose one of the poles, if desired. Electrodes are used to detect the electrical signals from the cell mass. Various methods of making the capsule are disclosed.

Abstract: A high integrity liposome comprising at least one stabile lipid and at least one peptide-like therapeutic agent associated with said liposome, adapted for parenteral administration to an animal, including a human, and method according to manufacture and use. Immunizing dosage forms comprising a liposome and an immunogen, wherein said liposome and immunogen are present in an immunization dose. Additionally, a dosage form, including such form particularly adapted to producing an immune response, comprising a salt according to an organic acid derivative of a sterol and an immunogen wherein said organic acid derivative of a sterol and immunogen are present in an immunization dose, and method according to use is disclosed.

Abstract: This invention provides a heterotelechelic oligomer or polymer which is represented by the following formula: ##STR1## wherein A denotes a sugar residue, L denotes a linkage group represented by the following formula ##STR2## wherein R.sup.1 and R.sup.2 independently denote lower alkyl, aralkyl or aryl,X denotes a single bond or --CH.sub.2 CH.sub.2 --, Z denotes a group forming an unsaturated ester or ether, or a functional group such as halogen which binds to --CH.sub.2 CH.sub.2 --, n denotes an integer of 5-10,000, and m denotes an integer of 0 or 2-10,000.This invention also provides a process to produce the above oligomer or polymer, and further a high molecular-micelle with use of a polyethylene oxide-polyester block polymer which has a sugar residue at its terminal. Said oligomer or polymer is expected to exhibit excellent bioavailability, and is also expected to be utilized in the field such as carriers for drug delivery or diagnostic reagents.

Abstract: This invention provides a composition containing a sized liposome comprising a lipid and an inducer; the sized liposome has a diameter of at most about 1 micron and the inducer is present in an amount effective to induce interdigitation-fusion of the sized liposome. Also provided herein are interdigitation-fusion liposomes and gels, and methods of making the same.

Abstract: An immunoisolatory vehicle for the implantation into an individual of cells which produce a needed product or provide a needed metabolic function. The vehicle is comprised of a core region containing isolated cells and materials sufficient to maintain the cells, and a permselective, biocompatible, peripheral region free of the isolated cells, which immunoisolates the core yet provides for the delivery of the secreted product or metabolic function to the individual.

Abstract: A method for encapsulation of antineoplastic agents in liposomes is provided, having preferably a high drug:lipid ratio. Liposomes may be made by a process that loads the drug by an active mechanism using a transmembrane ion gradient, preferably a transmembrane pH gradient. Using this technique, trapping efficiencies approach 100%, and liposomes may be loaded with drug immediately prior to use, eliminating stability problems related to drug retention in the liposomes. Drug:lipid ratios employed are about 3-80 fold higher than for traditional liposome preparations, and the release rate of the drug from the liposomes is reduced. An assay method to determine free antineoplastic agents in a liposome preparation is also disclosed.

Abstract: A method for drying microspheres in a fluidized bed is provided, along with a composition comprising microspheres dried by that method.

Abstract: A pharmaceutical implant for the delivery of an effective amount of a bioactive peptide or peptide analog over a period of 1 to 12 months. This implant has a diameter of about 1 to 2 mm, a length of between about 10 and 25 mm and is obtainable from a process which includes the steps of grinding a copolymer of lactic acid and glycolic acid having a ratio of glycolide to lactide units of from about 0 to 5:1 to a particle size of between about 50 and 150 .mu.m; sterilizing the ground copolymer with a dose of between about 1 and 2.5 Mrads of ionizing .gamma.-radiation; wetting the ground and sterilized copolymer with a sterile aqueous slurry of a bioactive peptide or peptide analog; aseptically blending the copolymer and the slurry to obtain a homogeneous mixture of the copolymer and between about 10 and 50% of the bioactive peptide or peptide analog; drying the mixture at reduced pressure and at temperature not exceeding 25.degree. C.

Abstract: A process for rendering hydrophilic a separation membrane having a hydrophobic matrix polymer comprises doping the membrane solvent system with a cyclic ester additive which is compatible with the matrix polymer and adding a wetting agnet additive, such that the resulting membrane is instantaneously wetted. The invention further relates to the membrne formed in accord with this process.

Abstract: Disclosed are multivesicular liposomes containing biologically active substances, and having defined size distribution, adjustable average size, adjustable internal chamber size and number, and a modulated release of the biologically active substance. The liposomes are made by a process comprising dissolving a lipid component in volatile organic solvents, adding an immiscible aqueous component containing at least one biologically active substance to be encapsulated, and adding to either or both the organic solvents and the lipid component, a hydrochloride effective to control the release rate of the biologically active substance from the multivesicular liposome. A water-in-oil emulsion is made from the two components, the emulsion is immersed into a second aqueous component, and then divided into small solvent spherules which contain even smaller aqueous chambers. The solvents arc finally removed to give an aqueous suspension of multivesicular liposomes encapsulating biologically active substances.

Abstract: The present invention provides for liposomes formed with alkylammonium fatty acid salts, and methods for manufacturing same. The liposomes of the invention may deliver entrapped load material or materials at the occurrence of a preset triggering condition. Preferred liposomes of the invention are cationic liposomes. The preferred liposomes of the invention are formed with alkylammonium fatty acid salts, e.g., trialkylammonium fatty acid salts of long chain amides. The liposomes of the invention are used to encapsulate both hydrophobic and hydrophilic load materials. The liposomes formed accordingly are capable of delivering their loads upon the occurrence of a trigger or control condition.

Abstract: The present invention provides a microporous material or a membrane in which the membrane includes an azlactone moiety which is blended with or grafted to a thermoplastic polymer to provide a porous material having an internal structure characterized by a multiplicity of spaced, randomly disposed, non-uniform shaped, equiaxed particles of the polyazlactone polymer/thermoplastic polymer blends or the azlactone-graft copolymer. Each of the adjacent particles throughout the material are separated from one another to provide said material with a network of interconnected micropores and each of the particles are connected to each other by a plurality of fibrils. In addition to unmodified azlactone membranes, membranes which have been modified by subsequent reaction of the azlactone moiety with a suitable nucleophile are also included within the scope of the present invention.

Abstract: A composite polyamide reverse osmosis membrane and method of producing same. In one embodiment, the membrane is made by coating a porous polysulfone support for about 40 seconds with an aqueous solution containing 2 wt % of meta-phenylenediamine (MPD), 1 wt % 1,4-diazabicyclo[2,2,2]octane (DABCO) and 0.85 wt % methanesulfonic acid (MSA). Next, the excess MPD solution is removed, and the coated support is dipped for about 1 minute in 0.1 wt % organic solvent solution of trimesoyl chloride (TMC) in a mixture of alkanes having from 8 to 12 carbon atoms. After draining the TMC solution off, the resulting composite membrane is heated at 90.degree. C. for about 3.5 minutes and then rinsed in a basic aqueous solution at 40-60.degree. C. for 30 minutes. The resultant membrane exhibits a flux of 32.3 gfd and a salt rejection of 97.0% when used at 225 psi for an aqueous solution containing 2000 ppm of NaCl.

Abstract: A liposomal aqueous dispersion and method of making the liposomal aqueous dispersion is useful for encapsulation of drugs. The liposomal aqueous dispersion comprises: an aqueous suspension medium; multilamellar liposomes comprising an anionic phospholipid and cholesterol as essential components; neutral phospholipid in a mole ratio of 0 to 40% based on the total amount of said multilamellar liposomes; and a cation moiety-containing water-soluble drug, wherein the electrolyte concentration of said aqueous suspension medium is not more than 40 mM.

Abstract: The invention is directed to a process for producing a porous polymer comprising the steps of: (1) dispersing a porogen in a continuous monomer component phase wherein said continuous monomer component phase comprises at least one monomer having at least one perfluoropolyether unit and wherein said porogen is an optionally substituted poly(alkylene)glycol; (2) thereafter polymerising the continuous monomer phase; and (3) removing the porogen from the porous polymer.

Abstract: A method for making a skinless essentially symmetrical hydrophobic polysulfone microporous membrane by the steps of (a) forming a casting solution containing (i) a dissolved polyethersulfone polymer, (ii) a solvent for the polyethersulfone polymer, and (iii) a lower aliphatic glycol; (b) coating a substrate with the casting composition; (c) exposing the coated substrate to atmospheric conditions; (d) passing the exposed coated substrate into a precipitation bath to precipitate the membrane, the precipitation bath containing a lower aliphatic glycol and water; (e) rinsing the membrane; and (f) drying the membrane.

Abstract: Systems for processing dope for the manufacture of microporous phase inversion membrane having any one of a plurality of different pore sizes from a single master dope batch is disclosed. The systems and methods include formulating a single master batch of dope preferably maximizing the non-solvent to solvent ratio for a given weight percentage of polymer for use in a microporous phase inversion membrane casting operation to produce phase inversion membranes having one of a plurality of different predetermined pore sizes. The master dope batch is controllably formulated in a vessel such that the temperature of the dope does not exceed a predetermined maximum mixing temperature and is maintained at a relatively low temperature (lower than the mixing temperature) suitable for storage.

Abstract: The invention relates to a process for stabilization of vesicles formed from a lipid-phase membrane containing at least one ionic and/or nonionic amphiphilic lipid encapsulating an aqueous phase, in the form of a dispersion in an aqueous phase, by addition of at least one stabilizing agent to the aqueous dispersion phase, in which the stabilizing agent (s) is/are chosen from the group composed of glycerol alginates, propylene glycol alginates, gellan gum and wellan gum. The invention also relates to a composition for topical application containing vesicles stabilized by the said process.

Abstract: A method for loading a therapeutic compound having a cis diol moiety into pre-formed liposomes is described. The method includes adding to a suspension of liposomes (i) the compound to be loaded into the liposomes and (ii) a boronic acid compound, thereby achieving accumulation of the compound within the liposomes.

Abstract: A method for preparing encapsulated lipid-bilayer materials in a silica matrix comprising preparing a silica sol, mixing a lipid-bilayer material in the silica sol and allowing the mixture to gel to form the encapsulated lipid-bilayer material. The mild processing conditions allow quantitative entrapment of pre-formed lipid-bilayer materials without modification to the material's spectral characteristics. The method allows for the immobilization of lipid membranes to surfaces. The encapsulated lipid-bilayer materials perform as sensitive optical sensors for the detection of analytes such as heavy metal ions and can be used as drug delivery systems and as separation devices.

Abstract: A process for encapsulating a core material by mixing the core material with an aqueous medium comprising a natural polymer and treating the formed mixture at a pressure of from about 15,000 to 200,000 psi at a temperature of from about 0.degree. to 100.degree. C. to form a gel matrix comprising the core material encapsulated within the natural food polymer and then drying the resulting product.

Abstract: A controlled release delivery system includes a functional gene vector in a biodegradable polymeric microsphere encapsulating the vector. The present invention further provides a method of making a controlled release delivery system by encapsulating the functional gene vector in a biologically degradable polymeric microsphere.

Abstract: The present invention relates to cationically charge-modified membranes and methods of preparing such membranes. In one major aspect of the invention, the membranes are hydrophobic membranes that are treated with one or more polymeric wetting agents to render the membranes substantially hydrophilic, followed by treatment with one or more charge-modifying agents, the agents causing the membranes to possess a fixed formal positive charge. In another major aspect of the invention, a cationic membrane is formed from casting in a film a mixed polymer solution comprising a sulfone polymer and a copolymer of vinylpyrrolidone and a cationic imidazolinium compound, and quenching the film in an aqueous bath to produce a coagulated membrane. The membrane can be further cationically charge-modified with one or more charge-modifying agents.

Abstract: The invention provides a method for obtaining local anesthetics encapsulated in liposomes, such as multivesicular liposomes, with high encapsulation efficiency and slow release in vivo. When the encapsulated anesthetic is administered as a single intracutaneous dose, the duration of anesthesia and half-life of the drug at the local injection site is increased as compared to injection of unencapsulated anesthetic. The maximum tolerated dose of the encapsulated anesthetic is also markedly increased in the liposomal formulation over injection of unencapsulated anesthetic. These results show that the liposomal formulation of local anesthetic is usefuil for sustained local infiltration and nerve block anesthesia.

Abstract: A radially wound tubular fiber disk comprises a single strand of tubular fiber having a feed inlet at one end and a feed outlet at the other. Radially arranged adhesive strips forming seams maintain a desired spacing between adjacent convolutions of the tubular fiber disk and hold the disk in place.

Abstract: A dispersion is formed of aqueous polymer particles in a non-aqueous liquid and a stabiliser is covalently reacted on to the particles.

Abstract: A collagen containing substrate comprising cattle basal membrane is conditioned by incubating the membranes in a mixture of pepsin, hyaluronidase and acetic acid and separating the collagen from the mixture. The mixture can include pepsin, hyaluronidase and a 0.5M solution of acetic acid in 1:1:10 proportions. The incubation is conducted for about 10 hours at about 45.degree. C. After incubation, collagen is separated from the mixture by centrifuging at a speed of 5000 to 30000 rpms for about 30 minutes. The collagen is mixed with polymerizable monomer and polymerized to form a gel that can be ground to form an intraocular or contact lens.

Abstract: A method and apparatus is provided for casting a polymeric membrane on the inside surface of porous tubes to provide a permeate filter system capable of withstanding hostile operating conditions and having excellent selectivity capabilities. Any polymer in solution, by either solvent means or melt processing means, is capable of being used in the present invention to form a thin polymer membrane having uniform thickness on the inside surface of a porous tube. Multiple tubes configured as a tubular module can also be coated with the polymer solution. By positioning the longitudinal axis of the tubes in a substantially horizontal position and rotating the tube about the longitudinal axis, the polymer solution coats the inside surface of the porous tubes without substantially infiltrating the pores of the porous tubes, thereby providing a permeate filter system having enhanced separation capabilities.