Cerdak, the Good, the Bad, the Oxygen and the Wound bed - A movie about the wonder of natural wound healing.
Cerdak granules - highly absorbent ceramic granules
The Goodies - Inflammatory elements, Proteins,Cellular elements, Growth factors, All other biological elements assisting in the healing process
The Badies - micro-organisms, Goodies healing elements whose useful lifetime has expired, chronic inflammation
Atmospheric Oxygen - Another goodie important for healing, especially in oxygen deprived wounds.
The Wound bed - an injured area on the body
The Cerdak wound dressing consists of spherical micro-porous ceramic granules contained in a sachet made from a wicking fabric. The granules are loosely packed, allowing free access of air to the wound. The raw material used for producing the ceramic is bio-inert alumina (aluminium oxide), also widely used for making ceramic prostheses.
The micro-porous ceramic granules have an average diameter of 0,7mm and a porosity of more than 60 volume per cent. The patented microstructure shown below, consists of a porous alumina matrix that encloses cellular pores with average diameters of 5 micro- meters. The cellular pores are interconnected by means of 0,3 micrometer diameter blow-holes, created during the manufacturing process. As a result of the interconnectedness between the cellular pores and the micro-porosity in the alumina matrix, the porosity is supplemented by a high permeability and a high surface area.
RELEVANT PROPERTIES OF CERDAK WOUND DRESSING
The most important properties of Cerdak wound dressing is micropore-driven capillary absorption, transport and storage of wound exudate and surface-area-driven adsorption of charged colloids suspended in wound liquids as well as odourous gases emanating from the wound.
ABSORPTION, TRANSPORT AND STORAGE OF WOUND EXUDATE BY CAPILLARY FORCES
The absorption, transport and storage of the exudate by the micro-porous ceramic granules result in the transfer of fluid from the wound bed to the pores of the ceramic. This is caused by the capillary pressure created at each pore by the surface tension of the exudate, the degree of wetting of the ceramic by the exudates and the effective diameter of the pore. The magnitude of this pressure is given by:
This gives a calculated average capillary suction force of 90 kPa. The potency of these forces are evident when compared with the systolic blood pressure of 16 kPa and the body's capillary forces of 4 kPa.
THE MECHANISM OF ABSORPTION AND DISTRIBUTION OF EXUDATE IN THE PORES OF THE CERAMIC
The mechanism of absorption, transport and storage of exudates is illustrated in the following sketch:
The wound produces exudate at a rate V₁. This fluid passes through the wicking sachet and when it comes into contact with the ceramic with its high capillary suction force, it is absorbed at a rate V₂, which is much faster than the rate of supply. Since each ceramic granule is in point-contact with surrounding granules with similar high suction potential, moisture migrates continuously between the granules in an attempt to equalize the hydrostatic potential of all the granules in the sachet. There is however no driving force for the exudates to leave the ceramic granules, so that the interstitial air gaps between the granules remain dry and filled with air.
Since the rate of removal of exudate by the ceramic is greater than the rate at which the exudate is supplied to the ceramic, it follows that the contact between the ceramic and the retained moisture in the wound bed will intermittently be broken and then re-established by a supply of freshly-produced exudate as shown in the explanatory movie.
THE INFLUENCE OF CERDAK’S ABSORPTION MECHANISM ON WOUND HEALING
- There is no continuous liquid phase between the old absorbed exudate locked up in the ceramic and fresh wound exudate in the wound bed
- The bacteria present in the wound bed are periodically removed with the old exudate, hence diluting the noxious components present in old exudate and known to retard the healing process
- Atmospheric oxygen can circulate through the interstitial voids between the loosely stacked ceramic granules to keep the moist wound aerated
- Due to the cyclic absorption, the moisture in the wound remains fresh with new growth factors and the wound bed is periodically exposed to atmospheric oxygen without a liquid interface
Adsorption refers to surface-area driven properties of the ceramic and is independent of the capillary-force driven absorption. An oxide surface like the micro-porous alumina ceramic has a marked acid-base character since it contains a definite number of ionizing sites from which protons (acid dissociation) or hydroxyl ions (basic dissociation) may be released, giving rise to a net surface charge. A proton colloidal solid on the other hand, may develop surface charges due to the ionization of side-chain amino acid groups. The ionic charges of free radicals are axiomatic.
In vitro tests were done to establish whether the ceramic surface would adsorb colloidal bacterial protein toxins and free radicals known to be suspended in wound exudates and known to extend the inflammation phase and the time for the wound to heal. The tests confirmed that in addition to the benefit of having little or no antibacterial activity, the Cerdak granules exhibited a high endotoxin (standard) binding as well as a free radical scavenging power.
The effect of free radicals on DNA is well known. DNA, synthesized from e.coli was subjected to hydroxyl radicals. The free radicals were synthesized in situ by exposing a mixture containing both DNA and hydrogen peroxide to ultra violet light for five minutes. The experiment was repeated after adding incremental small quantities of the microporous granules to the mixture and the results were compared after gel electrophoresis. The results showed that the microporous ceramic granules are extremely efficient scavengers of hydroxyl free radicals, and during the process, the DNA is preserved against any structural damage.