Authors: Professor Val Edwards-Jones1, Dr Vladimir Vishnyakov1, Pam Spruce2 1. Manchester Metropolitan University, Manchester, UK 2. TVRE Consulting, UK. m

1. An In vitro Investigation of the
Structure of Four Absorbent Dressings
Using Scanning Electron Microscopy
Authors: Professor Val Edwards-Jones1
, Dr Vladimir Vishnyakov1
, Pam Spruce2
1. Manchester Metropolitan University, Manchester, UK v.e.jones@mmu.ac.uk,
v.vishnyakov@mmu.ac.uk
2. TVRE Consulting, UK. pamspruce@gmail.com

2. Authors: Professor Val Edwards-Jones1
, Dr Vladimir Vishnyakov1
Pam Spruce2
An In vitro Investigation of the Structure of Four Absorbent Dressings
Using Scanning Electron Microscopy
INTRODUCTION
Absorbent dressings are commonly used in the management of acute and chronic wounds. A wide
range of dressings are now available, and while their primary function is to absorb excess exudate
in order to provide the correct environment at the wound bed for healing, an additional benefit is that
they may have the capacity to retain deleterious pathogens.
AIM
To observe the structure of four dressings* used in wound management for exudate absorption using
electron microscopy. To investigate whether these dressings had the capacity to retain bacteria.

3. Authors: Professor Val Edwards-Jones1
, Dr Vladimir Vishnyakov1
Pam Spruce2
An In vitro Investigation of the Structure of Four Absorbent Dressings
Using Scanning Electron Microscopy
METHODS
The dressings were investigated in three different conditions; dry, wet and in the presence of four
different microorganisms.
DRY
The dressings were trimmed to approximately 0.5cm x 0.5cm and attached to a holder and placed
into the chamber of a Leica high resolution Scanning Electron Microscope (SEM). Each dressing was
scanned and images taken at varying magnification to investigate the internal structure.
WET
Sterile distilled water was added to a 1cm x 1cm piece of dressing until fully hydrated. The dressings
were left to absorb the water for a minimum of 2 hrs and then prepared for scanning and image
capture Each dressing was trimmed to 0.5cm x 0.5cm and placed into a holder. This holder was
placed into liquid nitrogen to freeze the dressing in a hydrated nature (-180o
C). The frozen dressing
was then placed within the chamber of the Leica SEM and the temperature slowly raised to -120o
C
(time taken between 1-3hrs) to allow the water crystals to vapourise. The dressing was then scanned
at the same magnification as the dry dressings.

4. Authors: Professor Val Edwards-Jones1
, Dr Vladimir Vishnyakov1
Pam Spruce2
An In vitro Investigation of the Structure of Four Absorbent Dressings
Using Scanning Electron Microscopy
DRESSING WITH MICROORGANISMS
Four different microorganisms which are commonly found in wounds were used for each
dressing. Escherichia coli, Pseudomonas aeruginosa, Candida albicans, and Methicillin-resistant
Staphylococcus aureus (MRSA)
A suspension of microorganisms in phosphate buffered saline was allowed to sequester into the
dressing overnight. Following sequestration, the dressing was placed into formal saline (saline with
formaldehyde) for 18hrs to kill the microorganisms (to ensure the microscope was not contaminated).
The dressings were then washed with phosphate buffered saline to remove traces of formaldehyde
and also to remove any microorganism not firmly adhered to the dressings. The dressings were then
placed at 37o
C for 24hrs to dry ready for scanning electron microscopy.
Each dressing was trimmed to 0.5cm x 0.5cm and attached to the mount prior to insertion into the
electron microscope. Any change in the structure of the dressing was noted (in case of change
following sequestration) and the position of microorganism on the dressing noted.

5. Authors: Professor Val Edwards-Jones1
, Dr Vladimir Vishnyakov1
Pam Spruce2
An In vitro Investigation of the Structure of Four Absorbent Dressings
Using Scanning Electron Microscopy
RESULTS
Dressing 1 A circular cart wheel structure was observed within the dressing, holding a mass of fibres.
The dressing looked the same in hydrated conditions. It was difficult to see any microorganisms within
the dressing. In particular no Escherichia coli were observed.
Dressing 2 consisted of two types of fibres, smooth and striated. The dressing looked the same in
hydrated conditions. All microorganisms were easily found, attached to the fibres of the dressing.
Dressing 3 consisted of a mass of smooth fibres that once hydrated disappeared into a gel-like
matrix. Microorganisms could be seen embedded in the gel-like matrix.
Dressing 4 consisted of a mass of fibres with irregularities on their surface. On hydration, a
substance was observed adhered to the surface of the fibres. Bacteria Methicillin-resistant
Staphylococcus aureus (MRSA), Pseudomonas aeruginosa and Escherichia coli were attached to the
fibres, often within the irregularities. No Candida albicans was observed.

6. Authors: Professor Val Edwards-Jones1
, Dr Vladimir Vishnyakov1
Pam Spruce2
An In vitro Investigation of the Structure of Four Absorbent Dressings
Using Scanning Electron Microscopy
MRSA P.aeruginosa E.coli C.albicans
Dressing 1 No E.coli seen
Dressing 2
Dressing 3
Dressing 4 No Candida observed

7. Authors: Professor Val Edwards-Jones1
, Dr Vladimir Vishnyakov1
Pam Spruce2
An In vitro Investigation of the Structure of Four Absorbent Dressings
Using Scanning Electron Microscopy
CONCLUSION
Electron microscopy allowed the structure of the dressing to be observed in wet and dry conditions.
This methodology also allowed microorganisms to be observed in the dressings. Dressings 2 and 3
sequestered all the test microorganisms.
REFERENCES
* Dressings included in the study.
Dressing 1: Advadraw®
(Advancis Medical)
Dressing 2: Drawtex®
(Beier Drawtex Healthcare)
Dressing 3: Aquacel®
Extra™ (Convatec)
Dressing 4: UrgoClean®
(UrgoMedical)
This study was supported by an educational grant from Martindale Pharma.