The patent's assignee is 3M
News editors obtained the following quote from the background information supplied by the inventors: "The disclosure relates generally to methods for processing plastic substrates having inorganic antimicrobial microparticles within.
"A great deal of attention has been paid in recent years to the hazards of bacterial contamination from potential everyday exposure. Microbial growth on surfaces can pose serious threats to human health. As such, manufacturers have begun incorporating antimicrobial agents within various household products and articles.
"A number of inorganic materials have been shown to possess antimicrobial activity, include transition metals (e.g., silver, copper, zinc, gold, cerium, platinum, palladium, or tin). It is theorized that these metals, or ions thereof, exert their effects by disrupting respiration and electron transport systems upon absorption into bacterial or fungal cells.
"Silver and salts thereof have been used as an antimicrobial agent for centuries, and with the development of nano-silver technology, the use of silver in inorganic nano-particle form has produced a platform of high performance antimicrobial agents. Generally, these nano-silver materials consist of silver ions integrated into inert matrices consisting of ceramic, glass, or zeolite. Inorganic, silver-based antimicrobials that allow for controlled silver ion release have been proven effective against a variety of pathogens in a variety of environments and have been incorporated in a number of different materials of potential use in healthcare.
"It has been proposed that silver ions interact with disulfide or sulfhydryl groups of enzymes within cells causing structural changes that lead to disruption of metabolic processes followed by cell death. Eukaryotic cells (e.g., red blood cells and leukocytes) possess the necessary cellular mechanisms to overcome this disruption, whereas prokaryotic organisms (e.g., bacteria) do not, and hence silver can rapidly reduce or eliminate prokaryotic pathogens. Thus, silver-releasing particles provide an advantage over other antimicrobial agents that indiscriminately destroy both prokaryotic and eukaryotic cells."
As a supplement to the background information on this patent application, NewsRx correspondents also obtained the inventors' summary information for this patent application: "In one aspect, the disclosure provides a method of making a plastic article having an antimicrobial surface, the method comprising providing a plastic substrate having a substrate surface, wherein the plastic substrate comprises inorganic antimicrobial microparticles disposed within; and plasma etching the substrate surface to expose a portion of the inorganic antimicrobial microparticles. In some embodiments, the inorganic antimicrobial microparticles comprise a ceramic carrier and at least one antimicrobial metal. In some embodiments, the ceramic carrier is at least one of clay, zeolite, or silicon dioxide. In some embodiments, the antimicrobial metal is a transition metal. In some embodiments, the at least one antimicrobial metal is selected from the group consisting of silver, gold, copper, and zinc.
"In some embodiments of the method of the disclosure, the inorganic antimicrobial microparticles have an average particle size that is at least 1 micrometer. In some embodiments, the inorganic antimicrobial microparticles have an average particle size that is in a range of from 5 micrometers to 10 micrometers.
"In some embodiments of the method of the disclosure, the inorganic antimicrobial microparticles have an average particle size that is at least an order of magnitude smaller than a smallest dimension of the plastic substrate.
"In some embodiments, the inorganic antimicrobial microparticles are stable to processing at temperatures up to 1000.degree. C. (in some embodiments, up to 900.degree. C., up to 800.degree. C., up to 700.degree. C., up to 600.degree. C., or even up to 500.degree. C.).
"In some embodiments, the substrate surface comprises at least 0.1% by area (in some embodiments, in a range of from 0.3% by area to 1% by area) of inorganic antimicrobial microparticles after the plasma etching.
"In some embodiments, the inorganic antimicrobial microparticles comprise the antimicrobial metal in an amount that is up to 50 wt. % (in some embodiments, up to 20 wt. %, up to 10 wt. %, up to 5 wt. %, or even up to 1 wt. %) of a total weight inorganic antimicrobial microparticles.
"In some embodiments, the substrate surface comprises a low surface energy plastic.
"In some embodiments, providing the plastic substrate having a substrate surface comprises at least one of injection molding, thermoforming, or extruding.
"In some embodiments, the substrate surface comprises a high touch surface. In some embodiments, the substrate surface comprises any of a medical device or medical device component, a food preparation surface, or a doorknob.
"In some embodiments of the method of the disclosure, the plasma etching comprises positioning the plastic substrate in a process chamber, introducing a process gas into the process chamber, and generating the plasma. In some other embodiments, the plasma etching comprises positioning the plastic substrate in a process chamber, introducing a process gas into a remote plasma generation chamber, generating the plasma remote from the process chamber, and introducing the plasma to the process chamber.
"Methods of the current disclosure are useful for practical manufacture of plastic articles having an antimicrobial surface (e.g., medical devices, food preparation surfaces, high-touch surfaces). The manufacturing may be carried out in a continuous mode, suitable for production of multiple instances of plastic articles having an antimicrobial surface. The manufacturing may be carried out in a solventless mode, potentially minimizing environmental impact, and potentially reducing manufacturing costs.
"The method of the current disclosure can uniquely provide advantages that include a one-time plasma treatment for generation of the antimicrobial surface (i.e., potentially avoiding higher cost associated with reapplication of an antimicrobial coating), avoiding the need for chemically bonding the antimicrobial agent to the substrate surface (chemical bonding of other antimicrobials to polymers may reduces their antimicrobial activity), and immobilization of the inorganic antimicrobial microparticles in the substrate surface (some other antimicrobial coatings are water soluble and are quickly washed away).
"The term 'antimicrobial' as used herein describes an agent that can reduce the pathogenic contamination of a surface.
"The term 'ceramic carrier' as used herein describes a ceramic material that serves as a carrier for an inorganic antimicrobial agent. The ceramic carrier may or may not have antimicrobial activity.
"The term 'high touch surface' as used herein describes a surface that is frequently touched by humans (e.g., touched by a human hand, optionally a gloved human hand).
"The term 'inorganic antimicrobial' as used herein describes an antimicrobial composition that is at least 95 wt. % inorganic materials.
"The term 'low surface energy' as used herein describes a substrate surface having a surface energy of less than about 30 dynes per square centimeter.
"The term 'microorganism,' 'microbe,' or a derivative thereof, as used herein refers to any microscopic organism, including without limitations, one or more of bacteria, viruses, algae, fungi and protozoa. In some cases, the microorganisms of particular interest are those that are pathogenic, and the term 'pathogen' is used herein to refer to any pathogenic microorganism.
"The term 'microparticles' as used herein describes particles between 0.1 micrometer and 100 micrometers in size.
"The term ''plasma' as used herein describes a partially or fully ionized gas composed of ions, electrons, and neutral species. The plasma can be generated from various inert gases and reactive gases, as well as mixtures of inert gases, mixtures of reactive gases, and/or mixtures of inert gases and reactive gases.
"The term 'plasma etching' as used herein describes a process of subjecting a substrate to a plasma (or plasma products, in the case of a remote plasma etching), resulting in the removal of a portion of the substrate surface and thereby exposing material within the substrate.
"The term 'plastic' as used herein describes any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products.
"The term 'substrate' as used herein describes a non-porous sheet, a porous sheet, a fabric, a fiber, or a combination thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
"FIGS. 1A-1B are profile representations of an exemplary plastic substrate of the current disclosure, before (FIG. 1A) and after (FIG. 1B) plasma etching the substrate surface;
"FIG. 1C is an enlarged view of a portion of the substrate surface of FIG. 1B;
"FIGS. 2A-2B are profile representations of an exemplary plastic substrate of the current disclosure, illustrating the interaction of microbes with the substrate surface, before (FIG. 2A) and after (FIG. 2B) plasma etching the substrate surface.
"Although terms such as 'top', bottom', 'upper', lower', 'under', 'over', 'front', 'back', 'outward', 'inward', 'up' and 'down', and 'first' and 'second' may be used in this disclosure, it should be understood that those terms are used in their relative sense only unless otherwise noted."
For additional information on this patent application, see: Appeaning, Maria A.; Ylitalo, Caroline M.; Stepanova, Narina Y.; David, Moses M. Method for Making Plastic Articles Having an Antimicrobial Surface. Filed
Keywords for this news article include: Nanotechnology, Plasma Etching, Emerging Technologies, 3M
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