Antimicrobial efficiency of metal and metal oxide colloidal nanoparticles against E.coli

Koloidne nanočestice metala i metalnih oksida se sve više upotrebljavaju kao alternativa antibioticima zbog njihovih brojnih prednosti u svrhu liječenja i sprječavanja bakterijskih infekcija, a osobito su popularne koloidne nanočestice srebra, titanova dioksida i cinkova oksida zbog svoje široke primjene u biomedicini, industriji i biotehnologiji. Escherichia coli vrlo je zanimljiv modelni organizam za proučavanje jer pripada najviše istraženim bakterijama na svijetu, no i dalje je vrlo čest uzročnik bakterijskih infekcija raznih organskih sustava koje mogu biti i životno ugrožavajuće. Stalnom borbom protiv infekcija uzrokovanih E.coli raznim načinima, primjerice antibioticima, došlo je do razvitka otpornih sojeva protiv kojih se vrlo teško boriti uobičajenim načinima pa se stoga treba okrenuti i novim sredstvima. Upravo je to i cilj ovog rada, pokazati da su koloidne nanočestice ta nova opcija, tj. sredstvo borbe protiv bakterijskih infekcija. MIK i MBK vrijednostima koloidnih nanočestica srebra, cinkova oksida i titanova dioksida na E.coli ATCC 10536 pokazano je kako su one vrlo potentno antimikrobno sredstvo, a među njima najpotentniji baktericidni učinak imaju koloidne nanočestice srebra. U svrhu ispitivanja mogućeg postojanja sinergizma navedenih koloidnih nanočestica, pripremljena je optimirana smjesa koja se sastojala od 0.794 ppm nanočestica srebra, 683.217 ppm nanočestica titanova dioksida i 15.989 ppm nanočestica cinkova oksida što ukupno čini smjesu od 700.000 ppm. Rezultati govore u prilog antagonizmu, ali i da nema statistički značajne razlike u antimikrobnoj aktivnosti na sojeve ATCC 10536 i ESBL+ MFBF 12794 bakterijske vrste E.coli. Zadnji korak je ispitati antimikrobnu aktivnost tkanine impregnirane slojem navedene smjese koloidnih nanočestica, a rezultati govore da kod oba soja dolazi do potpune odnosno stopostotne redukcije broja kolonija nakon 12 sata inkubacije tkanine na koju su inokulirani ispitivani sojevi. Međutim, nema statistički značajne razlike u postotku redukcije broja kolonija između ispitivanih sojeva sojeva.Metal and metal oxide colloidal nanoparticles are increasingly used as an alternative to antibiotics because of their many advantages (in comparison to antibiotics) for treatment and prevention of bacterial infections. The most popular colloidal nanoparticles are silver, zinc oxide and titanium dioxide nanoparticles because they are used in various fields such as biotechnology and biomedicine. Escherichia coli (E.coli) is the most finely understood and extensively studied free-living organism on our planet. However, despite being the most extensively studied organism, E.coli is still to this day a very common cause of diseases of various organs and therefore E.coli is a very interesting model organism for this study. Resistance to antibiotics emerges in bacteria due to genetic mutations and consecutive selection of resistant mutants through selective pressure of antibiotics and because of that antibiotic resistance has become one of the leading problems in modern medicine. Therefore, currently available options (such as antibiotics) against bacterial infections are limited and it is advised to turn to new and improved antimicrobial agents. Metal and metal oxide colloidal nanoparticles are exactly that, the new and improved antimicrobial agents. MIC and MBC values of silver, zinc oxide and titanium colloidal nanoparticles against E.coli ATCC 10536 suggest that these nanoparticles are very potent antimicrobial agents with silver nanoparticles being the most potent of them. A mixture of nanoparticles (0.794 ppm of silver, 683.217 ppm of titanium dioxide and 15.989 ppm of zinc oxide) was prepared to determine a possible synergism between them. Results suggest that there is no synergism observed between silver, zinc oxide and titanium colloidal nanoparticles in the mixture and that there is no statistically significant difference in terms of antimicrobial efficiency against the two E.coli strains (ATCC 10536 i ESBL+ MFBF 12794). Lastly, antimicrobial efficiency of a textile fabric impregnated with the mixture of nanoparticles was evaluated using the time-kill method. Results suggest that after 12 hours of incubation there were no growth of bacterial colonies observed (complete reduction of bacterial colonies) for both E.coli strains. However, no statistically significant difference in terms of reduction of bacterial colonies was observed between the two E.coli strains