New technology surfaces
June 1st 2008

A coating that makes surfaces easy to clean, actively reducing the growth of bacteria will contribute to improved hygiene and infection control strategies. It will make the cleaning job easier, safer and has the potential to significantly reduce costs. Does such a coating exist? Nano Hygiene Coatings thinks so...

Developed by Nano Hygiene Coatings, 4MED is a hygiene coating with hydrophobic/oleophobic properties. These properties make the surface non-stick and stain resistant. The coating combines the benefits of the easy-to-clean properties derived from nano chemical technology with an antimicrobial additive, actively preventing the growth of bacteria such as Escherichia Coli and MRSA.

Acting as reservoirs for many types of organisms, soil can accumulate on surfaces creating the ideal conditions for bacterial growth. Reducing that growth will significantly reduce the risks associated with their harmful effects.

At Nano Hygiene coatings,we undertook a series of tests, to establish whether: soil accumulates on surfaces over time, despite being repeatedly cleaned hydrophobic surfaces affect soil accumulation growth of bacteria on a surface could be reduced reduction of bacteria could be achieved quickly, and antimicrobial effect is long – lasting Stainless steel samples were soiled repeatedly with a solution containing bovine serum albumin (BSA) and an artificial organic soilant. Between each soilant event, the samples were cleaned for 10 seconds under running mains tap water. Of the two stainless steel samples tested, one was uncoated, and the other was coated with an NHC hydrophobic coating.

The results showed that the appearance of the uncoated surfaces continued to deteriorate significantly, despite repeated soiling and cleaning.The uncoated stainless steel samples retained significant organic deposits. In contrast the coated samples maintained their appearance and retained very little soiling. They were both visually and microscopically cleaner than the uncoated surfaces.

For testing growth of bacteria, the above test was repeated but this time with the stainless steel coated with 4MED. Antimicrobial activity was determined after the final soiling / cleaning event. The results revealed that biological significant activity had occurred on the 4MED coated sample, with the bacterial population declining by four orders of magnitude in 24 hours: an effective kill rate of 99.99 per cent. Over the same time period, bacterial populations had declined by 0.5 of a magnitude on the uncoated stainless steel.

Tests supporting the claims of any antimicrobial coating should be based on realistic exposure scenarios, i.e.

undertaken in the conditions that it will be used, or simulating those conditions. 4MED has been tested, on a splash of contaminated water, and, secondly, on a splash of contaminated body / animal fluid.

Both tests were undertaken with a sample coated with 4MED, and a sample coated with a hydrophobic coating but without antimicrobial functionality. For the contaminated water test, a suspension of E Coli was prepared in sterile distilled water. For the contaminated body / animal fluid test an E Coli inoculum was prepared in a vegetable oil / bovine serum albumin (BSA) solution (oil / protein solution).

Results showed that for the contaminated water splash test,4MED achieved a fast rate of kill of the bacterial population, resulting in a reduction of ca 2.5 orders of magnitude in three hours and a reduction to below the limit of detection in six hours. The Oil/Protein test results showed that the bacterial population declined by 0.5 orders of magnitude within 12 hours and a statistically significant 2.5 orders of magnitude in 24 hours; a kill rate of over 99 per cent.

To determine longevity, 4MED coated samples were artificially aged by processing in a dishwasher and the antimicrobial efficacy subsequently tested. Test samples contaminated with E Coli were processed at 40ºC with no detergent (13 litres per cycle) for 120 dishwash cycles.

The results showed that 120 dishwash cycles did not have any statistically significant impact on the performance of 4MED antimicrobial efficacy. The bacterial populations were reduced by four orders of magnitude following six hours contact to below the limit of detection in 24 hours.

Conclusions Dirt and organic deposits can build up on surfaces, despite repeated washing and cleaning, severely impacting the appearance.Coated hydrophobic surfaces, however, have no or little accumulation of soil which makes them an easy-clean solution. Combining the hydrophobic / Oleophobic properties with the antimicrobial functionality of 4MED produces synergistic benefits, significantly reducing the growth of bacteria. 4MED, tested under simulated teal life conditions has shown to be robust and durable, acting quickly and is effective even after artificial ageing. .

The implications for improved cleaning and hygiene strategies are clear. 4MED makes the cleaning job easier. It can have a direct impact on the costs associated with the cleaning job, reducing the growth of bacteria and contributing to the lowering of the risks associated with their harmful effects.