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Fighting bacteria with silver nanoparticles

How safe is your home? We are not talking of external threats but of internal threats like bacteria, algae and other microorganisms. Unlike floors and tabletops, there are several inconvenient and inaccessible surfaces, especially walls within our homes (and offices) that harbor bacteria leading to fomite transmission, that is, transmission of infectious diseases by bacteria left on surfaces.

The good news is that technology has come to the rescue. Asian Paints, India’s leading manufacturer of paints, has launched paints using technology that not only makes the walls look beautiful but is also good for the health of the inhabitants. This product is an anti-bacterial paint.

One may ask why the need for anti-bacterial paint? The reason is that in most Indian homes, the walls are not cleaned as often as the floors or the furniture. But bacteria and other microorganisms are known to colonise walls, tiles, building facades or any such surface that provides the right ecosystem for their growth.

Since microbial growth can cause significant damage to walls and building facades, a lot of research has been done to identify the bio factors that result in degradation and to analyse the sensitivity of microorganisms to biocides.

Cho et al., investigated the antibacterial efficacy of silver nanoparticles against Staphylococcus aureus (gram positive bacteria) and Escherichia coli (gram negative bacteria). When a suspension of silver nanoparticles, of an average size of 10 nm, was used, it was found that the suspension significantly inhibited the growth of both S. aureus and E. coli.

Another study* was done using a model of aerial green algae, Apatococcus lobatus (A. lobatus) to assess the biocidal properties of silver nanoparticles against aerial algal biofilms that cause biodegradation and biodeterioration of building materials.

The research revealed inhibition of aerial algal growth in terms of changes in structure and photosynthetic activity of the cells, depending on time and dosage of silver nanoparticles. Thus, it was found that silver nanoparticles could be used as a biocide against aerial algal coatings too.

Thanks to their unique properties, silver nanoparticles can be used against pathogenic bacterial activity. The increased surface area of silver nanoparticles, results in better contact with microorganisms, hence it results in a more effective biocidal activity**.

These unique properties of silver nanoparticles have made it a product that is used across various industries, especially those where an antiseptic effect is desirable, such as medicine and pharmacy, food, cosmetology, textile, construction, etc. 

Since microorganisms spread naturally by wind and weather conditions, researchers working on conservation of historic and other modern utility structures have been looking for ways to eradicate existing biological contamination besides inhibiting the microorganisms’ ability to re-colonize.

Photosynthetic micro-organisms can be extremely hazardous for building materials as the penetrating algae release chemical compounds eroding building substrates. Aerial algae have proved to be especially hazardous in case of limestone substrates. Algal biofilms are known to degrade wood substrates because the algae periodically store water inside their cells and excrete it later increasing dampness in the material surface.

In order to protect buildings, the silver nanoparticles are used as a biocidal component of building materials. In a US patent application, a method of their incorporation in the structure of the building materials is described. These materials may be used as roofing, insulation, siding, upholstery and other applications. The authors of the patent indicate that silver nano particles present in these types of materials inactivate bacteria, fungi or algae which can cause significant damage otherwise.

Increasing progress in research on the effects of silver nanoparticles on biological systems has led to the application of these molecules to the public and commercial use. Taking the lead, Asian Paints has introduced a water-based ‘Royale Health Shield Luxury Emulsion’, an indoor paint that makes home interior walls more hygienic.  

The`Royale Health Shield Luxury Emulsion’ is also the first paint in India to be equipped with the Silver Ion Technology as recommended*** by the Indian Medical Association. 99%# percent of infection-causing bacteria are killed within two hours itself when in contact with the paint. The antibacterial paint thus reduces possibility of respiratory infections and skin sensitization. Available in 1750 plus shades, it also neutralizes indoor air pollutants like formaldehyde making the indoor air healthier to breathe.

Apart from homes, the paint would be especially beneficial when used in facilities like hospitals, laboratories, schools, retirement homes and cafeterias where greater hygiene needs to be maintained.   

* The study was done by Paulina Nowicka-Kraczyk, Joanna Zelazna-Wieczorek, Tomasz Kozlecki at the Laboratory of Algology and Mycology, Faculty of Biology and Environmental Protection, University of Poland, Department of Chemical Engineering, Faculty of Chemistry, Wroclaw University of Technology, Wroclaw, Poland.
**Silver Nanoparticles – a material of the future…?, a Paper by Jolanta Pulit-Prociak and Marcin Banach, Department of Engineering and Chemical Technology, Cracow University, of Technology, Poland.
#Royale Health Shield with Silver Ion technology, within 2 hours of exposure kills 99% bacteria on walls.
***Fomite Infections (bacteria) can spread through infected walls among other indoor surfaces in homes and offices

– Rajeshwari Adappa, freelance journalist

Disclaimer: I acknowledge the support and contribution of Asian Paints Limited in providing information for this article. The purpose of this article is to explain the scientific principles behind anti-bacterial paints. All product specific views expressed here are my personal views. Readers should do their own research & consult professionals before purchasing the product. Products may not function as intended if they are not correctly used. Please also refer to product guides provided by companies before purchasing the product as your purchase and use of the product will be governed by them. For complete disclaimer and more information, please visit

Also read: When hygiene meets beauty and durability

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