1. Nanotechnology

The property of matter depends on size and many of the chemical and physical characteristics change significantly when matter is reduced in size.  Nanotechnology is a general term that refers to a relatively new frontier of scientific endeavor.  The prefix “nano” signifies one-billionth.  Therefore, a nanometer is one-billionth of a meter, a nanogram is one billionth of a gram.  Ten hydrogen atoms placed side by side measures one nanometer in length.  Silver crystals sputtered under normal vapor deposit conditions result in tightly adherent crystals of 100-900nm in diameter.  Decreasing crystal volume by nanotechnology markedly increases the exposed surface area of the crystal which increases the available surface for chemical reactions to take place over a shorter time period.

Decreasing the particle size will also, in general, change the physical/chemical properties of the material.  Examples of changed properties resulting from nano-sized metals, include increased superconductivity and increased optical and electrical properties.  Nanosizing can also lead to a more economical utilization of expensive materials-meaning that can use less material because the reactions are more efficient.

Although not yet specifically defined, it is clear that some of the properties of silver in a nanocrystal are quite different than the typical crystal.  A large portion of the silver is available as grain or interphase boundaries, considered by some to be a new form of matter.  Orientation relationships are very different for the silver.  Also some of the silver appears to be in an oxidized form.  Increasing the variety of oxidized silver species would be expected to increase solubility and lead to a much higher overall reactivity.

         Nanocrystalline Silver

2. Physical Properties Of Acticoat™ Nanocrystalline Silver Delivery System

The method of making the nanocrystalline material on Acticoat is called physical vapour deposition.  Argon gas is introduced into a vacuum chamber that contains a silver cathode, the chamber acting as the anode.  When an electric current is passed through the gas, positive argon ions are created which accelerate towards the negatively charged silver cathode.  On impact, the argon ions knock out silver atoms that travel towards the substrate to be coated where they deposit and develop into nanocrystals when energy inputs are limited.  These are only about 15 nanometers across, which is between 30 a 50 atoms.  Thus a nanocrystalline structure is created with a significant grain-boundary component and increased surface area.

These changes to the physical properties of the crystal lattice result in a meta-stable, high-energy form of elemental silver.  Normal silver placed in water will not dissolve, but nanocrystalline silver dissolves to provide a continuous concentration in solution of around 70 ppm.  Both Ag+ and Ag⁰ are released: it is thought that Ag⁰  does not react with chloride as quickly as Ag+ and does not require a carrier.  As the ions in solution are depleted, the equilibrium shifts and more Ag+ and Ag⁰   ions are released.  By contrast, silver nitrate provides a huge immediate concentration of silver ions which, two hours after application, have virtually all been chemically consumed by chloride.

3. Silver Nanocrystalline Delivery Dressing (ACTICOAT™)

The silver delivery dressing developed by Dr. Burrell is a 3 layer wound dressing consisting of an absorbent rayon/polyester core laminated between an upper and lower layer of silver coated high density polyethylene mesh.  The laminations are held in place with ultrasound welds.  The silver coating, which consists of 0.25±0.4 mg silver per mg high-density polyethylene, is a binary allow of silver and oxygen with negligible contaminants (content is 99.99% silver).

The coatings are highly porous and consist of nanocrystals organized into coarse columnar structures.

This unique physical structure, in combination with the oxygen atoms/molecules that are trapped in the crystal lattice, contribute to the enhanced solubility of the films which continue to release silver until the concentration in solution reached 66mg/L a level that is 50 to 100 times higher than is expected from typical bulk pieces of silver metal.

The silver crystals coat both sides of the product with a polyester core between the sheets to maintain the moisture needed for silver release.  Either side of the silver dressing can be placed onto the wound surface.  The silver coating when wet with sterile water, produces a continual release of Ag+ and likely other silver radicals for days.  The delivery system readily olds to the wound producing wound occlusion as well as  maintaining a wound surface moisture layer.  Current published data indicates that this silver release product produces a rapid and complete killing of essentially all pathogens found on a wound.

The silver delivery system is represented. Both silver layers release the silver ion exposure to water.

REACTIVE SPECIES OF SILVER RELEASED FROM SLIVER PRODUCTS

Note: The release of silver with the nanocrystalline pure silver delivery system is constant for over 48 hours when exposed to water.  The silver concentration on the wound surface is 20-30 times greater than the concentration required to kill microbes. The concentration of Ag+ required to kill pseudomonas is comparable to that required for killing of other microbes.  This constant silver release is unique and quite different from the initial pulse release of silver Ag+ from other products.

Nanocrystal Silver Delivery System (ACTICOAT™)

Silver Delivery System (ACTICOAT™)

• A three (3) ply dressing consisting of inner rayon/polyester core between two (2) layers of silver coated mesh

• Nanocrystalline silver placed onto a bilayer of polyethylene for controlled release
• Nanocrystal coating containing 0.84 to 1.34 mg silver/cm²

• Ionic silver and silver radicals released in ideal concentrations when exposed to water

• Active silver release up to 7 days
• Maintain moisture layer for healing between wound and silver membrane
• Highly bactericidal fungicidal

• Silver Nitrate 0.5% solution

- Ag+ availability 318μg Ag+/mL water

- Immediate release

• Silver Nitrate 1% cream

- Ag+ availability 3030μg Ag+/gram

- Release over 12-24 hours

• Silver Nitrate (Nanocrystals)

- Ag+ availability 100μg Ag+/mL water

- Stable release for at least 48 hours

The large sheets of Acticoat™ nanocrystal silver is shown form fitting to a large wound