For decades, misuse and overuse of antibiotics for therapeutic and especially for industrial purposes promoted the development of antibiotic resistant bacteria. New solutions to enhance hygiene standards and limit the spread of bacteria are desperately needed. Antimicrobial surfaces have been demonstrated as a valid strategy to help break the infection chain, especially when applied as high touch-surfaces where there is a high risk of bacteria transfer. Copper metal and copper-based alloys are, due to their intrinsically antibacterial efficacy, ideal candidates for these purposes. Currently, a variety of test methods are suggested to inspect the antibacterial properties of copper alloy surfaces. However, experimental methods that take into account surface modifications caused by high frequency contact and deposited perspiration in addition to transfer of bacteria are still absent. The aim of this research is to develop a method to mimic the real conditions of indoor exposure of high touch surfaces introducing wet/dry cyclic exposures in combination with spray deposition of artificial sweat (ASW) on Cu and Cu5Zn5Al1Sn (Golden alloy) surfaces. GIXRD, FTIR, SEM-EDX and colorimetric analysis allowed to depict changes in surface appearance of Cu and Cu5Zn5Al1Sn surfaces with and without ASW deposition. The copper release from those surfaces during ASW immersion was measured by means of AAS; release rates from surfaces of different ageing times were assessed and the role of copper ions in inactivation of bacteria is discussed. Furthermore, antibacterial tests under wet and dry conditions using ASW as a bacteria transfer media, contributed to develop a new experimental set-up to evaluate antibacterial properties of indoor hygiene surfaces. The novel method established at “Quasi-dry” conditions provided reproducible results and was in accordance with real application conditions. The antibacterial efficacy of Cu and Cu5Zn5Al1Sn surfaces exposed to wet/dry cycles with and without ASW deposition was assessed and discussed based on the surface characterization results. The outcome of this novel multidisciplinary approach, combining fundamentals of atmospheric corrosion and microbiology, provides a new modus operandi to test antibacterial properties of high-touch surfaces, insight about the bactericidal mechanism of copper and shows surface modifications after accelerated hand-contact conditions.
Per decenni, un uso improprio e un abuso di antibiotici per scopi terapeutici e industriali hanno favorito l’insorgenza di batteri antibiotico-resistenti; pertanto si rendono necessarie nuove soluzioni per migliorare gli standard di igiene e limitare la diffusione batterica. Le superfici antibatteriche rappresentano una valida strategia atta ad interrompere la catena infettiva, specialmente laddove il rischio di trasferimento batterico è elevato a causa di un’alta frequenza di contatto. Il rame e le sue leghe, data la loro intrinseca efficacia antibatterica, sono candidati ideali a questo scopo. In letteratura sono presenti diversi metodi per valutare le proprietà antibatteriche delle leghe di rame; tuttavia, è ancora assente un metodo sperimentale che consideri le modificazioni superficiali causate dall’alta frequenza di contatto e la deposizione di sudore come mezzo di trasferimento batterico. L’obiettivo di questa ricerca è di sviluppare un metodo per simulare le condizioni reali di superfici ad alta frequenza di contatto in ambienti chiusi mediante l’esposizione di campioni di Cu e Cu5Zn5Al1Sn (Golden alloy) a cicli umido/secco, in combinazione con la deposizione nebulizzata di sudore artificiale (ASW). Analisi GIXRD, FTIR, SEM-EDX e colorimetriche hanno permesso di mettere in luce i cambiamenti superficiali di Cu e Cu5Zn5Al1Sn con e senza deposizione di sudore artificiale. Esperimenti di immersione in ASW hanno consentito di rilevare il rilascio di ioni rame da superfici con differenti gradi di invecchiamento e di discutere il loro ruolo nel meccanismo antibatterico. Test antibatterici in condizioni wet e dry, utilizzando ASW come mezzo di trasferimento batterico, hanno contribuito a sviluppare un nuovo metodo sperimentale eseguito in condizioni “Quasi-dry”. Quest’ultimo ha fornito risultati affidabili, permettendo di simulare le condizioni reali. L’efficacia antibatterica delle superfici di Cu e Cu5Zn5Al1Sn esposte a cicli di invecchiamento con e senza deposizione di sudore artificiale è stata valutata e discussa in relazione alla caratterizzazione dei materiali. I risultati di questo approccio multidisciplinare innovativo, che combina nozioni di corrosione e microbiologia, forniscono un nuovo modus operandi per testare le proprietà antibatteriche di superfici ad alta frequenza di contatto, propongono intuizioni sul meccanismo antibatterico del rame e mostrano le modificazioni superficiali dovute all’effetto accelerato del contatto umano.
Antibacterial properties of high touch surfaces. Method development with a multidisciplinary approach
SEPATI, MATTEO
2018/2019
Abstract
For decades, misuse and overuse of antibiotics for therapeutic and especially for industrial purposes promoted the development of antibiotic resistant bacteria. New solutions to enhance hygiene standards and limit the spread of bacteria are desperately needed. Antimicrobial surfaces have been demonstrated as a valid strategy to help break the infection chain, especially when applied as high touch-surfaces where there is a high risk of bacteria transfer. Copper metal and copper-based alloys are, due to their intrinsically antibacterial efficacy, ideal candidates for these purposes. Currently, a variety of test methods are suggested to inspect the antibacterial properties of copper alloy surfaces. However, experimental methods that take into account surface modifications caused by high frequency contact and deposited perspiration in addition to transfer of bacteria are still absent. The aim of this research is to develop a method to mimic the real conditions of indoor exposure of high touch surfaces introducing wet/dry cyclic exposures in combination with spray deposition of artificial sweat (ASW) on Cu and Cu5Zn5Al1Sn (Golden alloy) surfaces. GIXRD, FTIR, SEM-EDX and colorimetric analysis allowed to depict changes in surface appearance of Cu and Cu5Zn5Al1Sn surfaces with and without ASW deposition. The copper release from those surfaces during ASW immersion was measured by means of AAS; release rates from surfaces of different ageing times were assessed and the role of copper ions in inactivation of bacteria is discussed. Furthermore, antibacterial tests under wet and dry conditions using ASW as a bacteria transfer media, contributed to develop a new experimental set-up to evaluate antibacterial properties of indoor hygiene surfaces. The novel method established at “Quasi-dry” conditions provided reproducible results and was in accordance with real application conditions. The antibacterial efficacy of Cu and Cu5Zn5Al1Sn surfaces exposed to wet/dry cycles with and without ASW deposition was assessed and discussed based on the surface characterization results. The outcome of this novel multidisciplinary approach, combining fundamentals of atmospheric corrosion and microbiology, provides a new modus operandi to test antibacterial properties of high-touch surfaces, insight about the bactericidal mechanism of copper and shows surface modifications after accelerated hand-contact conditions.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/152244