Safety in use thanks to biological tests and evidence of effectiveness
Dr. Dirk Höfer, Competence Centre for Medical Textiles at the Hohenstein Institutes in Bönnigheim
Antimicrobial effect Test of the activity of materials with antimicrobial finishes.
Skin compatibility Safety tests for textiles and medical textiles (cosmetic, medically active textiles, dressings etc.) BÖNNIGHEIM - More and more manufacturers are extending their collections to include antibacterial textiles. These are aimed in particular at clients from hygiene-sensitive sectors such as the health sector and the foodstuffs industry.
The fact that the clothing worn by doctors and nursing staff, as well as that worn by workers in food processing companies, can play a critical role in the transfer of dangerous pathogens is indisputable. Antibacterial finishes are therefore a powerful selling point for marketing high-quality workwear. This is particularly true if the effectiveness has been proven beyond all doubt, i.e. on the basis of practical tests carried out by a neutral body. On the other hand, the term "antibacterial" inevitably raises questions amongst wearers as to the skin compatibility of textiles finished in this way.
Compelling legal reasons such as § 30 of the Ordinance on Foodstuffs and Articles for Domestic Use require the use of innovative textiles to ensure there are no risks to health. The user of the textile products can therefore expect them to be safe in use, and not to pose a health risk. If an employer demands that specific workwear is worn or actually provides such workwear, he must ensure that this is safe as part of his duty of care towards his employee.
For this reason, validated test methods have been developed at and are available from the Hohenstein Institutes to objectively assess the biological safety and effectiveness of textiles with antimicrobial finishes on a scientific basis. The risk analysis is central to this test, in other words whether and in what way it is possible to assess the biological effects of these types of textile finishes on humans, what benefits the materials offer the wearer and whether these benefits are achieved without posing additional risks for the wearer.
Test of effectiveness as evidence of quality
To record the quantitative reduction of bacteria by antimicrobial textiles, test systems have become established which specifically record this process. With the aid of suspension tests such as the JIS 1902:2002 it is possible to record the maximum achievable in-vitro "degree of effectiveness" of the finished textiles as growth inhibitors of test bacteria. In this way, the antimicrobial effect of different materials can be compared at the product development stage and the manufacturer can make a selection based on the market readiness of the products. The Hohenstein scientists provide documentary evidence of the proven antimicrobial effect of textiles in the form of a certificate which has become established as neutral evidence of quality and which is highly regarded amongst decision-makers and purchasers. There is also the option to have the antimicrobial effect of the textile material tested and certified by Hohenstein specialists after 50 treatment cycles. The neutral evidence that a product fulfils the promised function throughout its entire useful life is an important criteria influencing the purchase of antimicrobial textiles.
Biological safety tests on skin test systems
The basis for the biological safety tests for textiles is the EN ISO 10993 for the biological evaluation of medical devices. This stipulates, depending on the type and duration of body contact, what risk analyses need to be carried out and which test methods need to be employed for this. The cytotoxicity (tissue compatibility) and sensitisation and irritation potential are tested.
When considering the tissue compatibility of textiles with antimicrobial finishes, it is particularly important to look at whether potentially cell-toxic substances could be released from the material during normal wear. In the cytotoxicity test in accordance with EN ISO 10993, an extract from the textile is prepared using an artificial perspiration solution. The effects of this on the L 929 fibroblasts and HaCaT keratinocytes from the human epidermis provide information on potentially cell-toxic components. At the Hohenstein Institutes, tests of this type are also carried out i.a. on the biological safety of textiles which are finished with silver and are used to treat cases of neurodermatitis.
A classic test to determine the irritation potential of a substance is the Draize test, in which the substance to be tested is dripped onto the conjunctiva of a laboratory animal's eye in order to identify any potential irritants. The scientifically recognised hen's egg test on the chorioallantoic membrane (HET-CAM) is an alternative to the animal test. This has been validated i.a. by the European Centre for the Validation of Alternative Methods (ECVAM). It is possible to determine the irritation potential of substances which could be released from the textile material just as accurately by observing the blood vessels of the treated egg as using the animal test. In addition to the cytotoxicity test, the HET-CAM test therefore offers decisive additional security regarding the use of antimicrobial textiles.
New biological test systems make it possible to scientifically determine the interactions between textiles and the skin accurately and to recognise and evaluate potential benefits and risks. The methods can be used as safety tests for textiles with antimicrobial finishes.
Competence Centre for Medical Textiles
Dr. Dirk Höfer
Tel: 07143 271-432
Bönnigheim, September 2004