The recent demands on thermoplastic elastomers have presented manufacturers with specific challenges regarding sterilisation. MARFRAN srl has responded by developing solutions based on bacteriostatic substances.
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The pandemic has brought many changes to our lifestyle, some of which are destined to remain for many months: the greater use of personal protective equipment (PPE) in the professional sphere is certainly the most evident example.
The current trend in opting for reusable devices rather than their disposable counterparts is bringing the need for devices and materials that allow easy and effective sanitisation of the devices.
Technical challenges
All materials commonly used to produce reusable PPE, including thermoplastic elastomers (TPE), must face two technical challenges: the sterilisation temperature increase compared with other products; and the widespread employment of multiple sterilisation cycles. Even when properly and repeatedly sterilised, germs and bacteria can still live on the surfaces of these materials. An additional challenge is, therefore, to design materials that are less hospitable for all those germs and bacteria which, if not adequately limited, can constitute a serious danger to human health.
The bacteriostatic effect
In 2015, MARFRAN srl (at that time Francesco Franceschetti Elastomeric srl) registered a patent on the use of ustic acid in TPE compounds as an antibacterial (WO 2016/020774 A1), the effectiveness of which has been proven by numerous tests conducted on various compounds. Although ustic acid is sustainable (it is obtained from some lichens), it also introduces processing and operation temperature limits. Thanks to some collaborations, MARFRAN srl has more recently developed solutions based on bacteriostatic substances which, due to being inorganic, can be used at higher processing temperatures making them more suitable for TPE compounds with a higher molecular weight.
The bacteriostatic effect prevents a bacterial biofilm forming on the surface of the devices, making even common detergents effective for sanitisation and autoclaving more effective and lasting.
The effectiveness of the bacteriostatic treatment of MARFRAN compounds was confirmed by evaluating the antibacterial activity conducted according to ISO 22196: 2011.
The bacterial strains chosen for the test with MARFRAN.MED 40A — a medical TPE compound suitable for autoclaving even at 134 °C are the following:
- GRAM negative ⇒ Escherichia coli
- GRAM positive ⇒ Staphylococcus aureus
The results obtained are quite positive considering the hardness of the chosen compound:
- Antibacterial activity against Escherichia Coli (GRAM negative) according to ISO 22196, R = 3.2 ⇒99.9%
- Antibacterial activity against Staphylococcus Aureus (GRAM positive) according to ISO 22196, R = 1.8 ⇒ 98.4%
Reduced viral load
During the current pandemic, the material has shown its ability to reduce the viral load present on the
Figure 1: Survival studies of SARS-CoV-2 and other coronaviruses on the surface of various materials.
surface. Numerous studies have highlighted the ability of the SARS-CoV-2 virus to survive on the surfaces of various materials, even for several days. Figure 1 summarises studies done in the first half of 2020 relating to the survival of the coronavirus on surfaces.
The result obtained is a reduction of about one decade of the viral population per unit area (TCID50/cm²) in the first 8 hours. This behaviour makes any sanitisation or sterilisation process much easier and more effective.
From this first series of tests, the advantages of the bacteriostatic treatment of MARFRAN TPE compounds are evident, and can be summarised as follows:
- Effective against GRAM negative bacteria
- Effective against GRAM positive bacteria
- Significantly contributes to the abatement of the SARS-CoV-2 superficial viral population
- Thermally stable
- Suitable for contact with food
- Non-cytotoxic, usable in the medical field
- Does not affect the mechanical characteristics of the material.
The use of bacteriostatic treatment in MARFRAN compounds is in continuous development. The
Figure 2: Bacteriostatic treatment finds application in many personal protective devices such as work clogs.
company has, for example, applied bacteriostatic treatment to work clogs (Figure 2), thus developing MARFRAN E CDP, an excellent permanent antistatic compound. The specific resistivity of volume and surface of less than 1*10^9 ohm*cm remains unchanged even in the presence of bacteriostatic treatment.
Sterilisation/sanitisation is a continuous focus of development for MARFRAN srl, a company that always follows the real needs and requirements of customers and their applications.