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Antibacterial Metal Fibers and Metal Nanoparticles

The antimicrobial textiles market is likely to grow significantly in the upcoming years. According to the recent estimations, the global antimicrobial textiles market will grow from USD 10.7 billion in 2021 to USD 14.7 billion by 2026. Moreover, as healthcare associated diseases are increasing in a number of hospitals, it is very important to protect medical devices as well as clothing used in the hospital. For that purpose material engineering enables that the antimicrobial products are integrated into devices and fabrics of healthcare. By this, the result is material that is resistant to the growth and spread of microbes and therefore can be odor-free. In the medical industry, the demand for antimicrobial textiles is high for hospital gowns, patient clothes, curtain, bed cover, surgical supplies, wipes, and others. Therefore the antimicrobial textiles have attracted a great interest in recent years due to their potential for reducing the transmission of infections in medical and health care environments. Antimicrobial textile materials reduce the adhesion of viruses and provide biocidal and antiviral activity or combinatory effects are today even more important due to the recent COVID-19 pandemic. This work presents our recent results in optimization and production of the hydrophobic antibacterial materials. [1]. The antimicrobial effects were tested on several different model microorganisms (Escherichia coli, Candida albicans, Staphylococus aureus, Klebsiella pseudomonia, MRSA and others). Obtained data on the toxicity to particular microoganisms was discussed, and the chemical characterization was performed by spectroscopic, chromatographic and microscopic techniques [2, 3]. By this, the hydrophobic materials were developed [4] and afterwards the antimicrobial effects were optimized [5]. The future perspectives of the emerging antimicrobial materials presents their significant role in the fight against microorganisms and viruses, needed for better future perspectives. ACKNOWLEDGEMENTS: This work was financially fully supported by the Croatian Science Foundation, project IP-2019-04-1381 under title „Antibacterial coating for biodegradable medicine materials ABBAMEDICA“.

Upotrebom nanočestica zlata (Au-) i srebra (Ag- NPs) u proizvodima prehrambene i tekstilne industrije je moguće unaprijediti njihova antibakterijska, UV zaštitna, vatroodbojna i/ili hidrofobna svojstva. U ovom je istraživanju provedena enzimatska sinteza Au- i Ag-NPs korištenjem dvaju oksidoreduktivnih enzima (celobioza dehidrogenaze (Mt CDH) i glukoza dehidrogenaze (Gc GDH)) kao prihvatljivija metoda sinteze kojom je moguće izbjeći pojedine nedostatke konvencionalnih metoda sinteze nanočestica. Ispitan je i optimiran utjecaj reakcijskih uvjeta na navedene reakcije te je određena reakcijska kinetika. Sintetizirane nanočestice su karakterizirane korištenjem UV-Vis spektroskopa, a prisustvo nanočestica zlata i srebra potvrđena je maksimalnim apsorbancijama na 540, odnosno 430 nm.

The usage of metal nanoparticles with exactly defined characteristics and their synthesis is among the most investigated research topics in the last decades. Gold and silver nanoparticles (NP) are considered as one of the most interesting nanoparticles due to their widespread application in health care, electronics, renewable energy and others. By their implementation in the products of the food and textile industry, many improvements in antibacterial, UV protection, flame retardant and/or hydrophobicity properties can be achieved. To overcome disadvantages during the conventional NPs synthesis, i.e. use of harsh chemicals and/or reaction conditions, enzymatic synthesis of Au- and Ag-NPs as a more convenient method was carried out in this research. For that purpose, two oxidoreductases: cellobiose dehydrogenase and glucose dehydrogenase were employed. The impact of the reaction conditions (temperature, enzyme and reactants concentration, reaction medium, pH, light and oxygen) was investigated and optimized. Successfully synthesized NPs were characterized by UV-Vis spectroscopy and transmission electron microscope (TEM). The determination of reaction kinetics and model development enabled insight in the reaction mechanism of the enzymatically catalyzed NPs.

Covid-19 is not the only threat to the global human health. It is estimated that by the year 2050, from the infections caused by antibiotic-resistant bacteria, more people could die than from AIDS, tuberculosis and viral hepatitis together. Only in Europe 25 000 deaths per year and costs over € 1.5 billion are the consequences of the resistant microorganisms activity. Therefore, in this work new antimicrobial materials containing nanoparticles active against Methicillin-resistant Staphylococcus aureus (MRSA) and Methicillin- sensitive Staphylococcus aureus (MSSA), microorganism strains resistant to antibiotics, are developed. Antimicrobial water-repellent coatings are intended for materials foreseen as: bedding hospital items, disposable antimicrobial lining and bandages for chronic wounds. In the development of the antimicrobial formulation, we apply the Response surface methodology (RSM) and mathematical modeling for predicting the optimal antimicrobial activity of nanoparticles and their mixtures. The thus-calculated antimicrobial mixtures are applied on the surface of biodegradable polymers (textiles or 3D printed surfaces) by sol-gel process. Polymers are characterized by different spectroscopic, microscopic and chromatographic methods and investigated for their newly obtained functional properties (water repellency, antimicrobial efficiency and others). Our results show that by applying RSM methodology and mathematical modeling, and by changing the process parameters excellent water repellency is achieved [1], as well as a very good antibacterial efficiency against MRSA and MSSA microorganisms [2]. In our future activities we plan to optimize the antimicrobial properties further in order to enhance the efficiency and reduce the time required for total antimicrobial effects in time interval shorter than few hours.

Biodegradable polymers that have antimicrobial properties have a very wide application in medicine and medical materials and are often used as medical textiles (bedding and hospital towels) or consumables such as bandages, gauze, and wound dressings. Polymers that are produced by 3D printing can also be functionalized with nanoparticle coatings to obtain antimicrobial properties. These materials can therefore be used as catheters, consumables, coatings and bags. In this work, the TLC method was applied to analyze 60 different metal ions in the antimicrobial coating of samples prepared in the laboratory. The stationary phases tested were 31 different preprepared cellulose and silica gel, polyamid and Al2O3, and the mobile phase consisted of various developers containing mixtures of inorganic and organic solvents (such as acetonitrile, acetyl acetone, butanol, triethylamine, ethylenediaminotetraacetic acid, hydrochloric acid, water, etc.). The optimal system that detected all metal ions consisted of silica gel as a stationary phase, while the mobile phase contained a solvent mixture of acetonitrile: hydrochloric acid: water, a volume of 24 mL in a volume ratio of 60.00: 19.17: 20.83. Sample detection was performed using a UV cabinet and during the detection the separation parameters (RF, Rs and others) of known standard solutions of metal ions were determined, which were then used in the detection of analytes in an unknown samples.

Nanotehnologija je znanost velikog potencijala za primjenu u brojnim područjima istraživanja. Nanočestice zlata, jedne su od najstabilnijih i biokompatibilnih vrsta nanočestica zbog čega se sve više primjenjuju u medicini, elektronici, tekstilnoj industriji i drugim područjima, a istražuje se i mogućnost njihove primjene u elektroničkim vodičima, isporuci lijekova, za terapeutske agense, u katalizi i sl. Sve veća potražnja i primjena metalnih nanočestica rezultira stoga i sve većom potrebom za razvojem ekološki prihvatljivijih metoda njihove sinteze. U ovom je radu provedena sinteza nanočestica zlata korištenjem tetrakloroauratne kiseline kao izvora iona zlata te glukoze kao reducensa. Ispitan je utjecaj uvjeta reakcije na koncentraciju i veličinu sintetiziranih nanočestica. Reakcije su provedene u fosfatnom puferu, pri sobnoj temperaturi te uz prisustvo svjetlosti i kisika. Rezultati istraživanja pokazali su da početna koncentracija glukoze blago utječe na reakcijsku brzinu sinteze nanočestica zlata, dok je utjecaj koncentracije tetrakloroauratne kiseline značajniji. Veličina sintetiziranih nanočestica gotovo i ne ovisi o koncentraciji glukoze, dok je njihova koncentracija u blagom porastu s porastom koncentracije glukoze.

Nanotehnologija se, kao znanost, sve više primjenjuje u raznim područjima tehnologije i industrije. Metalne nanočestice se, kao produkti nanotehnologije, ovisno o svojstvima koja pokazuju, koriste ponajviše u medicini, farmaciji, zaštiti okoliša, elektronici, energetici i sl. Nanočestice srebra su najšire korištene metalne nanočestice te su zbog svojih antimikrobnih svojstava trenutačno najzastupljenije u proizvodnji dezodoransa, odjeće, zavoja, otopina za čišćenje, sprejeva i medicinskih proizvoda. U okviru ovoga rada provedena je ekološki prihvatljiva sinteza nanočestica srebra uz upotrebu glukoze kao reducensa. Pri tome su ispitani uvjeti reakcije, tj. različite početne koncentracije srebrova nitrata, AgNO3 i glukoze u svrhu nastanka nanočestica što manjih veličina i što veće koncentracije. Reakcije su provedene u citratnom puferu, pri sobnoj temperaturi uz prisustvo svjetlosti i kisika. Provedeno ispitivanje pokazalo je da početna koncentracija glukoze ima blagi utjecaj na reakciju sinteze nanočestica srebra, dok je utjecaj koncentracije AgNO3 veći. Veličina sintetiziranih nanočestica srebra najmanja je pri najnižoj ispitanoj koncentraciji glukoze (5 mM) i najvišoj koncentraciji AgNO3, dok je brzina sinteze nanočestica najveća pri srednjoj ispitanoj koncentraciji glukoze (7 mM). Porast koncentracija sintetiziranih nanočestica srebra prisutan je s porastom početne koncentracije AgNO3.

Proizvodnja i upotreba metalnih nanočestica u kontinuiranom je porastu. Konvencionalne metode njihove sinteze često koriste razne toksične kemikalije i čine upotrebu tako sintetiziranih nanočestica ograničenom u prehrambenoj i tekstilnoj industriji, medicini, farmaceutici, itd. Stoga je vrlo važno naći i ispitati nove metode sinteze metalnih nanočestica koji će rezultirati ekološki prihvatljivim nanočesticama, a jedna od takvih upravo je njihova enzimatska sinteza. Nanočestice zlata jedne su od najviše istraživanih i korištenih vrsta nanočestica. Koriste se u raznim područjima znanosti i tehnologije te posebice u medicini u raznim terapijskim i dijagnostičkim sustavima. U ovom radu sintetizirane su nanočestice zlata korištenjem enzima glukoza dehidrogenaze (Gc GDH), koji katalizira reakciju oksidacije glukoze i celobioza dehidrogenaze (Mt CDH), koji katalizira reakciju oksidacije celobioze. Ispitana je kinetika oba enzima u navedenim reakcijama te je promatran utjecaj iona zlata na aktivnost enzima. Kinetika je u oba slučaja opisana jednosupstratnom Michaelis-Menteničinom kinetikom uz kompetitivnu inhibiciju ionima zlata. Procijenjene konstante inhibicije upućuju na to kako je inhibicija ionima zlata značajnija u slučaju reakcije oksidacije glukoze uz Gc GDH u odnosu na oksidaciju celobioze uz Mt CDH. Provođenjem sinteze nanočestica zlata uz Mt CDH i reakciju oksidacije celobioze, zaključeno je kako je mehanizam nastajanja naonočestica zlata direktno povezan s kinetikom reakcije oksidacije. Za navedenu sintezu postavljen je matematički model koji se dobro slaže s eksperimentalno dobivenim rezultatima. Prilikom sinteze nanočestica uz Gc GDH i glukozu, utvrđeno je da mehanizam nastajanja nanočestica nije povezan s reakcijom oksidacije glukoze, već nanočestice zlata nastaju redukcijom iona zlata uz glukozu i aminokiseline koje grade enzim.

Nanotechnology is a rapidly growing research area applicable in the textile industry, where nanoparticles integrated in the products can modify the existing materials or result with new product properties. Silver (Ag-) and gold nanoparticles (Au-NPs) are among the most commonly used NPs, and usually serve as coatings on medical textiles due to their antimicrobial properties. Therefore, there is an outgrowing need for the production of Ag- and Au-NPs, and it is necessary to develop a suitable and environmentally acceptable synthesis pathway. In this work, Ag- and Au-NPs syntheses were performed using glucose as a reductive agent. The influence of the different initial concentration of silver nitrate (AgNO3), tetrachloroauric acid (HAuCl4) and glucose was examined in a view of synthesizing the NPs of smallest size. The result has shown that the initial glucose concentration has a mild impact on both NPs synthesis while the influence of initial AgNO3 and HAuCl4 concentration was higher. Smallest Ag-NPs were synthesized using lowest glucose and highest AgNO3 concentration while the smallest Au- NPs were observed when both glucose and HAuCl4 were at the lowest or highest tested level.

Metal and metal oxide nanoparticles provide excellent antimicrobial, water resistance and protective properties so they are today one of the most important antimicrobial reagents in the textile industry. Therefore, extraordinary antimicrobial activity of metals and metal oxides receives significant global interest in the development of new products. The antimicrobial activity of the nanoparticles is the result of their very small diameters, which are far below the range of the microorganisms’ dimensions. Such nano-sized metals and metal oxides can interact with both bacterial surfaces and/or with the bacterial core, after they enter inside the bacterial cell showing activity against different microorganisms, including Gram-positive and Gram- negative bacteria, as well as on spores that are resistant to high temperature and high-pressure. Different biodegradable polymers containing nanoparticles in their surface coatings are used in many protective materials. In this work, thin layer chromatography (TLC) was applied as a simple, rapid and effective method for determination of metals in a form of metal ions which are used as efficient antibacterial compounds in protective coatings on biodegradable polymers. The development was performed by acetonitrile: hydrochloric acid: water= 72: 25: 23 (v/v), on thirty different stationary phases. For visualization, NH3 vapors and UV light (254 and 366 nm) were applied. Results proved that spots of different compounds (namely Ag, Al, Au, Co, Cr, Cu, Fe, Ni, Mn, Pb, Zn and others) can easily be determined. Proposed TLC method is therefore an excellent choice for identification and quantification of many metals used as antimicrobial compounds present in coatings on wide variety of different biodegradable polymers.

Nanotehnologija je jedna od najpopularnijih tema istraživanja u modernoj znanosti materijala te se naziva i područjem sljedeće industrijske revolucije. Nanočestice srebra (Ag NPs) najčešće su korištena vrsta metalnih nanočestica te se, s obzirom na baktericidna svojstva, primjenjuju uglavnom u području medicine za liječenje teških opeklina, razne dijagnostičke postupke i kao nosioci lijekova, ali i u tekstilnoj i prehrambenoj industriji gdje se ugrađuju u materijale u svrhu njihovog unapređivanja. Kao alternativa tradicionalnoj kemijskoj sintezi Ag NPs, danas se često koristi njihova enzimatska sinteza kojom se smanjuje upotreba reaktanata štetnih za ljude i okoliš. U ovom radu, u svrhu sinteze Ag NPs, korišten je enzim celobioza dehidrogenaza (Mt CDH) koji katalizira reakciju oksidacije celobioze te djeluje kao reducens iona srebra (Ag+ u Ag0). Ispitana je kinetika enzima kao i utjecaj iona srebra na kinetiku u acetatnom i citratnom puferu. Kinetika je u oba slučaja opisana jednosupstratnom Michealis-Menteničinom kinetikom uz kompetitivnu inhibiciju ionima srebra. Na temelju procijenjenih kinetičkih parametara zaključeno je kako je reakcija povoljnija u acetatnom puferu, s obzirom na znatno manju inhibiciju reakcije i deaktivaciju enzima ionima srebra u tom mediju. Postavljeni matematički modeli validiran je provođenjem reakcija sinteze Ag NPs u kotlastom reaktoru.