INCREASING HYGIENE CONCERN AND DEVELOPMENT OF ANTIMICROBIAL CERAMIC PRODUCTS NOWADAYS

Burcu ATLI, Mehmet Tumerkan KESIM, Gurol Ozhan DEMIREL, Nazan BEKTAS, Ender SUVACI

Entekno Industrial Technologies and Nano Materials Industry and Trade Inc., Eskisehir, Turkey


Introduction


Ceramic components we use in several areas, have a prominent place in our life. These products have been touching our life for thousands of years in numerous areas from kitchens to bathrooms, decorative products to electronic wares; and their durability along with aesthetical and economical features is adding more areas of use day by day [1,2].


Microorganisms are single and/or multi cell livings that cannot be seen with naked eye and can be found in all areas. To give an example of how much these creatures can be on some environments; there can be found 3,5 million bacteria on a computer keyboard, 1,6 million on a mobile phone, 3,2 million on a toilet and 186 million per one square meter in a bathroom [3,4].


In all areas we use ceramic products, we unavoidably and of necessity live with microorganisms that’s harmful to human health. These microorganisms in our life may harm human health and especially the kinds residing on bathroom ceramics can cause serious respiratory diseases. In addition, these microorganisms shorten the life of ceramic products and may also cause economic losses [3-5].


These undesirable problems based on microorganisms that we come across in several areas of our life, have become more important than ever during the times of COVID-19 disease/pandemic with SARS-CoV-2 virus and at consumer aspect it has become inevitable for the ceramic products we’re always in touch with in our daily life to show antibacterial/antimicrobial features. Intended for this need, there’re some various antibacterial/antimicrobial active ingredients used on and within ceramic glaze forms. Active silver and zinc oxide are the two most important among these active ingredients. In this article we give information on ceramic products and antibacterial and antimicrobial active ingredients used to prevent and/or annihilate the microorganisms we frequently and unwittingly come across on ceramic products which take an important part in our daily life.


Microorganisms and Ceramic Centerline in Our Daily Life


Lately public health is a social concern. News about pathogenic microorganism contamination at critical areas such as hospitals, slaughterhouses, restaurants, industrial facilities etc. are causing threat and concern to society. Ceramic wares are being used frequently in these areas and they have a potent place in our daily life so the sector is continuously improving itself in every situation that potentially affect or may affect people.


As the pandemic becomes a part of our life, hygiene, cleaning, antibacterial, antimicrobial and antiviral have become rather important concepts for people. People have begun to care their personal hygiene more than ever and changed their cleaning habits. End users have begun to prioritize functionality options featuring antibacterial and antiviral specifications in nearly all the products they consume. There are similar attempts in several products such as antibacterial soaps, dinner services, mobile phone covers, notebooks, dyes, toilets, tiles and cooking ware and as a consequence the number of antibacterial, antiviral and antimicrobial products are increasing. For this reason, production and effective use of antimicrobial active products, have a particular importance for the society.


Although ceramics are being used in several different areas, bathrooms and toilets are the mostly used areas. We can say that mold growth is one of the most important problems particularly for ceramics in these areas. Mold growth is even more critical for the bathroom which contains hygiene and personal care products. While fungi which cause mold growth can be found everywhere, they can reproduce quickly in humid environments. Therefore, bathrooms and toilets are very suitable areas for their reproduction. On one hand, mold growth leads to rapid depredation of ceramics and on the other hand, more concerning pathogenic flora may cause allergic bronchitis and sinusitis, asthma and serious lung lesions that are hard to diagnose. Using bath accessories that may be affected by microbial spores may lead to candidosis, stomatitis, streptoderma, allergic dermatitis and mycosis of feet and nails. Continuous inhalation of excretory substances and vital activity affects human gastrointestinal system and causes symptoms like disbacteriosis, diarrhea, throwing up and weakens the immune system [6].

Harmful microorganisms in our living spaces can be classified as bacteria, yeast and mold. And there are various protection technologies against these microorganisms. As regards to the specifications desired for ceramic surfaces, surface analysis must be conducted for concerned microorganisms. Concepts and mechanisms in the sector providing protection against microorganisms may be confused with each other and antibacterial – antimicrobial specifications may cause ambiguity. Antibacterial specification is the capability/characteristic that provides activity against gram negative bacteria such as E. Coli and gram-positive bacteria such as S. Aureus and prevents or annihilates the growth of these bacteria on relevant surfaces. Antimicrobial specification on the other hand, is the capability of the actives and agents with a wider spectrum of protection and active not only against bacteria but also against organisms such as yeasts and mold.


Reproducing on ceramic and other surfaces we often use and impacting human health and product quality, the microorganisms and effects of these is given in brief below:


ASPERGILLUS

· Allergenic, toxigenic.

· Aspergillus is green, white and grey. Have a floury look in dark spots. This kind of mold does not need much ventilation.

· Along with dry food, grows also on textile, walls and closed spaces such as attics, basements, bathrooms and toilets.

· Causes respiratory diseases and allergic response [7].


PENICILLIUM

· Allergenic.

· Known also as the blue mold. Can also look blurry green or yellow.

· Usually found on bathroom floors and walls, basements and insulations especially when there’s a water damage [8].


TRICHODERMA

· Allergenic.

· Creamy white, turns to green when leaves its’ spores.

· Usually found on woods, windows, bathrooms and kitchens [9].


STACHYBOTRYS

· Toxigenic.

· Named also as the black mold, this greenish black mold grows on places with high cellulose concentration.

· Usually found on paper, chipboard and plasterboard [10].


FUSARIUM

· Allergenic, toxigenic.

· Causes athlete’s foot and nail fungus infections .

· Broadly found in everywhere. Grows rapidly in humid areas [11].


ALTERNARIA

· Allergenic.

· This blurry mold grows as black dots on white ground.

· Tends to grow on textiles, wallpapers, near windows and air conditioners, in bathroom and kitchens.

· Causes respiratory diseases and asthma [12].


CLADOSPORIUM

· Allergenic, pathogenic.

· This mold is brown, dark green or black.

· Grows both in hot and cold places.

· Often found on woods, carpets or textiles and in heating and cooling ducts and bathrooms [13].


Why Choose Antibacterial/Antimicrobial Products?


Antibacterial/Antimicrobial products are chosen for the purpose of

· Preventing biofilm formation on surfaces where it’s hard to clean or remove with disinfection,

· Preventing cross-contamination of harmful substance and/or microorganisms from equipment or surfaces to humans,

· Providing full hygiene in case of inadequate cleaning processes,

· Preventing materials decay and corrode

It’s inevitable for ceramics to have antimicrobial protection as a consequence of pandemic and increasing cleaning demand for they’re a part of our life. Accordingly, it’s important to meet the active raw material needs of ceramic manufacturers in order to develop innovative products with superior protection.


Antibacterial/Antimicrobial Protection Approaches

An antimicrobial surface contains agents that prevent and/or reduce the reproduction of microorganisms that spread physically, chemically or biologically. There are various approaches to gain antibacterial and antimicrobial specifications to ceramic surfaces, bodies and glazes, and the essence of these approaches are mechanisms that provide activity against microorganisms. The propounded approaches in basic are as follows; (i) antibacterial active release (antibiotics, silver compounds, etc.), (ii) destroy with contact (chitosan, peptides, cationic compounds, etc.) and (iii) anti-adhesive, microorganism repellent (surface smoothness, organic molecules, etc.) [14,15].


While phenolic compounds, terpenoids, alkoloids and lectin and polypeptide derivatives are used as organic structured active ingredients [16], inorganic and metal based active ingredients such as zinc oxide and silver are preferred by ceramic industry for they’re much more suitable for ceramic manufacturing processes. There are mainly three different mechanisms in antimicrobial effect capability of ceramics. First of them is the added active ingredient and the reactive oxygens formed in the environment damaging the cell membrane and penetrates the microorganism, the second is the added active ingredient being dissolved, cation formation which may lead to free cytotoxic effect (for example Zn+ ion) and these cations damaging the cell. The last mechanism is the added antimicrobial active ingredient making the microorganism’s cell wall unstable and causing cellular integrity to be destroyed [17,18]. Achieving ceramic surfaces and bodies demonstrate antibacterial/antimicrobial specifications, is a result of one and/or several of the mechanisms mentioned above working together effectively. For instance, as seen in Figure 1, living bacteria cells encountering active agent lose their decent cell form and suffer lysis [17].

Bacteria Cells After exposed to MicNo HYG

Figure 1. Antibacterial effect of MicNo HYG® on S. aureus bacteria [17].


Antibacterial/Antimicrobial Active Ingredients


Structures like glaze and ceramic body contains several metal oxide ingredients and these ingredients have already their unique antibacterial/antimicrobial protection activities. But most of the time these ingredients are fall on effective protection in glaze and body compositions. Although there are several antimicrobial additive ingredients, silver-based ingredients are preferred more in the market recent years for their high protection potential. Even though it’s expected for antimicrobial silver ingredients to reach up a market value of 3 billion dollars by 2014 [19], because of the potential toxicology profile of silver and it’s accumulation in human body, studies on using other metal oxide compounds are increasing day by day and it’s stated that mixture of silver component and other metal oxides like zinc oxide helps to reduce high toxicity values of silver [20].


In the study made by Azam et al. it’s indicated that ZnO ingredient provides much more effective antibacterial protection than other active ingredients such as copper oxide and ferrous oxide excluding silver and toxic mercury [21]. Among several different active ingredients silver and zinc oxide stands out with their wide spectrum and potential providing effective protection.

Figure 2. Antimicrobial / Antibacterial active ingredients [22].



Which Specifications Antibacterial/Antimicrobial Additives Must Have Suitable for Ceramic Bodies and Glazes?


With various product ranges incorporated in it and diversification of these products in itself, ceramic industry offers many products to the market. It’s expected for active ingredients used in these products not to negatively affect the visual, physical and chemical properties of the products.


Despite there are many different organic and inorganic based materials used as antibacterial and/or antimicrobial, ingredients suitable for use in ceramic industry are the inorganic ingredients. Both for their high firing temperatures and long firing durations, inorganic based ingredients are suitable materials for use in ceramic industry because organic based active ingredients may decompose under manufacturing conditions and/or these kind of coating materials have low wear resistance during use. It’s also very important to properly use these inorganic based ingredients within ceramic bodies and glaze structures. As a consequence of their incompatibility with glaze cures, many existing additives in the market may cause faults like pinprick, crack, flaking, agglomeration, loss of gloss and spotting on ceramic surfaces. Besides, these ingredients may also negatively affect the glaze color and/or requires additional firing [22].


Taking all these into consideration, an ideal antibacterial/antimicrobial additive;

· Must provide long time protection and prevent microorganism reproduction.

· Must not cause any change, deformation on ceramic body and glaze structure and must maintain the ceramic properties.

· Must be easily used within every kind of glaze structure.

· Must have an easy use and not bring extra production steps to the manufacturer.

· Must be financially reasonable, demonstrate a quick and high effectiveness with low amount of use.

· Must not harm human and environmental health, must have low toxicity levels

As it’s not always easy to bring all these specifications together, the key is to develop innovative additives having these specifications.


MicNo HYG® Technology and What It Offers Us


Physical properties like size and shape are very important on antimicrobial effect. As the particle size decreases, the surface area and therefore the antimicrobial activity increases typically. Among the dusting systems, patented MicNo HYG® which is the designed form of nanoparticles in polygonal plaque morphology, stands out as an effective ingredient in providing high antimicrobial activity [17]. By appropriately applying MicNo HYG® on ceramics at proper concentrations, desired antimicrobial properties can be achieved on ceramic surfaces and bodies. With its’ genuine and innovative design, MicNo HYG® demonstrates wide spectrum antimicrobial activity against different bacteria, yeast and molds at low concentrations. Given in Table 1 are the minimum inhibition concentration values (MIC; µg/mL) MicNo HYG® active ingredient showed against eleven different microorganisms including bacteria, molds and fungi. Low MIC values shows that microorganisms are inhibited with less active ingredient use thus more antimicrobial protection is provided. According to the information obtained from the table, it’s clearly seen that MicNo HYG® product has a wide spectrum antimicrobial properties [17].


Table 1. Minimum inhibition/preventive concentration (MIC; µg/mL) of MicNo HYG® product against various microorganisms.


Developed by Entekno company and manufactured in compatible with the whole ceramic industry, the domestic and patented MicNo HYG® product has the most suitable antibacterial/antimicrobial additive specifications for ceramics. It prevents microorganism growth on applied ceramic products and offers a friendly solution for human health and environment. Silver and zinc oxide compounds in it are combined using MicNo® platform technology, in a genuine plaque structure, in a way to ensure effective and active distribution/spread (Figure 3). Nano-sized active silver distributed homogeneously on micron-sized plaques enables it to be adapted to all systems and blended into the system without facing any agglomeration.


In addition, thanks to its’ plaque structure, it does not cause any change in ceramic body, glaze structure and form and can homogeneously spread to whole product surface. And thanks to this spreading and also the zinc oxide and active silver combination, it provides wide spectrum antimicrobial protection and helps prolonging the ceramic products’ life.

Figure 3. MicNo HYG® consists of silver nanoparticles decorated by homogenously and strongly adhered on unique zinc oxide plaque structure and with its’ high surface area and dressing it interacts with microorganisms more compared to nano-sized particles (Symbolizing Green: Ag, Blue: ZnO).


MicNo HYG® product offers;

· Wide spectrum antimicrobial protection,

· High surface dressing,

· Long time effect,

· Human and environment friendly product,

· Homogenous composition,

· High protection values with low amount of use,

· Technical support with microbiology laboratory

to ceramic manufacturers. With human and environment friendly products we develop as Entekno company, we endeavor to help ceramic manufacturers and desire to add value to the Turkish ceramics industry. We will always be glad to assist our industry on high added value additive products and analyses.



References


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