Silver antimicrobials help hospital hygiene

Silver ions (blue) are transmitted to the bacteria (gold) via moisture. They disrupt the cell membranes of the microbes and deactivate them.

Ionic silver additives offer a robust way of keeping medical environments bacteria-free.

Encapsulated additives

Swiss antimicrobial producer Sanitized has launched a new line of encapsulated silver-based antimicrobial additives claimed to “deliver effective protection faster than ever before, and at concentrations lower than previously possible”. The products are said to offer “best-yet transparency for applications requiring fast and broad protection against microbes”.

According to the company, the silver formulation continues to perform through regular cleaning over the lifetime of the product to which it is applied, inhibiting germ growth and preventing odours even when in contact with humidity.

Sanitized uses a patented technology of silver encapsulated in a glass ceramic material at a small particle size. According to Sanitized this provides “a high degree of transparency which, when the antimicrobial is used in powder and liquid coatings, means that the aesthetics of the end-use application are not compromised”

The silver agent is claimed to be effective against a large number of bacteria and to remain stable at temperatures up to 500°C – far beyond any organic active compounds, says Sanitized.

The new products are compatible with a wide range of polymers, according to the company; in particular polyolefins, polystyrene and polyurethanes. The process stability of the encapsulated formulation is said to suit it to masterbatch use in plastics.

As well as medical applications the company mentions other demanding uses such as coatings on furniture and vinyl flooring; fibres for carpeting, bedding, mattress covers and pillow filling; non-woven materials for automotive seating and furnishing; packaging films; and cleaning equipment such as brooms, mops and cloths.

Maria Toscan, product manager for polymers at Sanitized says: “[The encapsulated formulation] offers well-understood antimicrobial performance with added value in terms of speed and cost-effectiveness, and without compromising aesthetics. In the personal care sphere, items such as toothbrushes made from hard injection moulded plastics can receive the same level of protection as sanitary ware such as basins, bathtubs, shower cubicles and toilet seats.”

Masterbatch formulation

MedX, the medical-specific formulation of Sanitized’s encapsulated silver agent, has been adopted by Clariant for a new range of antimicrobial Mevopur masterbatches. The aim is “to support the development of medical devices with surfaces that are active against bacteria.” Clariant cites independent tests demonstrating effectiveness against even antibiotic-resistant bacteria strains.

Clariant cites an increased need for antimicrobials in applications such as surgical instruments, catheters, connectors for tubing, and in-line filters to help reduce the transmission of bacteria which can cause secondary infection. A serious risk of death has been reported in the literature from hospital-acquired infection arising from catheters, says the company.

Clariant also reports increasing interest in evaluating antimicrobials for pharmaceutical packaging such as that for inhalers and ophthalmic solutions.

For the Mevopur masterbatches, Sanitized manufactures the active MedX silver agent according to Clariant’s quality control and impurity check requirements.

Clariant then carries out biological evaluation based on the ISO10993 test protocols developed for medical raw materials. This includes ISO10993 part 18 material characterisation at its ISO17025-certified laboratory in Singapore.

The company develops application-specific masterbatches for customers to evaluate. The carrier polymer grade for the masterbatch is selected according to the material used for the medical device. Options include polyethylene, polypropylene and polycarbonate. Pigments may be incorporated in the masterbatch if colouring is required.

In the case of transparent or translucent applications Clariant selects an active ingredient with a refractive index similar to that of the host polymer so as to maintain the desired degree of transparency in the final application.

Masterbatch is a convenient way to deliver the active ingredient into the host polymer, says Clariant. The concentration of the MedX antimicrobial agent is determined according to requirements for the chosen polymer and the device design, on the basis of Sanitized’s recommendations. Other factors to be considered include the types of bacteria predicted as contaminants and the operating conditions for the device. Clariant’s initial recommendation is taken as a starting point for the device producer’s own evaluation.

Since the antimicrobial agent is integrated into the polymer, says Clariant, there is no need for device manufacturers to add a secondary antimicrobial coating to their devices. Additional validation processes and extra costs are thus avoided.

Typical application: Suction liners

Disposable liners for medical suction systems afford a safe way of disposing of evacuated body fluids. With a view to minimising the risk of cross infection in hospitals, Plymouth-based VacSax has launched BactiClear disposable suction liners including silver-ion antibacterial protection by Stafford-based Biomaster.

According to VacSax, this is the only antibacterial suction liner system in the UK, with all external surfaces of the liner and canister having antibacterial properties.

Denise Ridall, VacSax’s associate sirector for sales and marketing says: “To date we have been in contact with over 50% of NHS hospitals to promote BactiClear, and our product information has gone to every hospital trust in the UK.”

VacSax cites independent tests of BactiClear to the ISO 22196:2011 standard, with a reduction in harmful bacteria such as MRSA and E. Coli of up to 99%.

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