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Bactericidal Surfaces Prepared by Femtosecond Laser Patterning and Layer-by-Layer Polyelectrolyte Coating
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology.ORCID iD: 0000-0003-4855-6668
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Antimicrobial surfaces are important in medical, clinical, and industrial applications, where bacterial infection and biofouling may constitute a serious threat to human health. Conventional approaches against bacteria involve coating the surface with antibiotics, cytotoxic polymers, or metal particles. However, these types of functionalization have a limited life-time and pose concerns in terms of leaching and degradation of the coating. Thus, there is a great interest in developing long-lasting and non-leaching bactericidal surfaces. To obtain a bactericidal surface, we combine μm-scale patterning of borosilicate glass surfaces by ultrashort pulsed laser irradiation and a non-leaching layer-by-layer polyelectrolyte modification of the surface. The combination of surface structure and surface charge results in an enhanced bactericidal effect against both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. The laser patterning and the layer-by-layer modification are environmentally friendly processes that are applicable to a wide variety of materials, which makes this method uniquely suited for fundamental studies of bacteria-surface interactions and paves the way for its applications in a variety of fields, such as in hygiene products and medical devices.

National Category
Manufacturing, Surface and Joining Technology
Research subject
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-264093OAI: oai:DiVA.org:kth-264093DiVA, id: diva2:1372026
Note

QC 20191126

Available from: 2019-11-21 Created: 2019-11-21 Last updated: 2019-11-26Bibliographically approved
In thesis
1. Development of Non-leaching Antibacterial Approaches on Cellulose-based Substrates and Their Mechanisms
Open this publication in new window or tab >>Development of Non-leaching Antibacterial Approaches on Cellulose-based Substrates and Their Mechanisms
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The layer-by-layer (LbL) technique is becoming a powerful tool that has been applied in many surface coatings and functionalizations in recent years. It has many advantages including a fast and mild process, the flexibility of choice of substrate, and the easiness to scale-up. Novel antibacterial materials can be achieved using this technique, by immobilizing selected antibacterial agents on surfaces of desired substrates. An ideal antibacterial agent, a cationic polyelectrolyte, can be LbL-deposited onto the surfaces in mono or multi layers, make the surfaces lethal to the bacteria due to their positive charge. This approach is able not only to effectively control the spreading of bacteria but also to minimize bacterial resistance as well as the environmental impact.

Cellulose fibres modified by different cationic polyelectrolytes including PDADMAC, PAH, PVAm as either monolayer or multilayer assembled with PAA using LbL deposition have shown more than 99.99 % bacterial removal as well as the inhibition of bacterial growth. Among these modifications, two layers of PVAm assembled with one layer of PAA have shown the highest antibacterial efficiency due to the highest adsorbed amount and charge density. Secondly, PAA was replaced by a bio-based cellulose nano-fibril (CNF), as a middle layer between two layers of PVAm, which decreases the carbon-footprint and expands the possibility of using LbL technique in antibacterial applications, since the LbL technique can be used long as the alternate layers are oppositely charged. The fibres modified with this approach have shown similar and even better antibacterial properties than those of PAA.

To develop the antibacterial approach using LbL on cellulose fibres, it is also essential to understand the antibacterial mechanism. It was found that the charge density and surface structures are two important factors affecting bacterial adhesion and the bactericidal effect. To study this, different charged cellulose model surfaces were made by coating oxidized, regenerated cellulose followed by PVAm/CNF/PVAm LbL deposition, and a better antibacterial effect was observed on the higher charged surface. By calculating the force between the bacteria and charged surface, it was suggested that a higher interaction due to the higher surface charge causes a large stress on the bacterial cell wall which leads to the disruption of the bacteria. To further improve the bactericidal effect, the flat surfaces were patterned with micro and nano structures using a femtosecond laser technique. The weakening of the bacterial cell wall caused by the charged surface makes the bacteria more vulnerable and easier to disrupt. This approach has been shown to be valid on both Gram-positive S. aureus, and Gram-negative E. coli. The effect was greater on E. coli with a weaker membrane structure and higher surface potential, which shows that the antibacterial mechanism is a physical disrupt of the bacterial cell.

Abstract [sv]

Layer-by-layer tekniken (LbL) blir ett kraftfullt verktyg som har använts i många ytbeläggningar och funktionaliseringar de senaste åren. Det har många fördelar, inklusive en snabb och mild process, flexibiliteten i valet av underlag och enkelheten att skala upp. Nya antibakteriella material kan uppnås med hjälp av denna teknik genom att immobilisera utvalda antibakteriella medel på ytor av önskat underlag. Ett idealiskt antibakteriellt medel, en katjonisk polyelektrolyt, kan LbL-avsättas på ytorna i mono- eller flerskikt, vilket gör ytorna dödliga för bakterierna på grund av deras positiva laddning. Detta tillvägagångssätt kan inte bara effektivt kontrollera spridning av bakterier utan också att minimera bakteriell resistens såväl som miljöpåverkan. Cellulosafibrer modifierade av olika katjoniska polyelektrolyter inklusive PDADMAC, PAH, PVAm som antingen monolager eller flerskikt sammansatt med PAA med användning av LbL-deposition har visat mer än 99,99% bakteriellt avlägsnande samt hämning av bakterietillväxt. Bland dessa modifieringar har två lager av PVAm sammansatt med ett skikt av PAA visat den högsta antibakteriella effektiviteten på grund av den högsta adsorberade mängden och laddningstäthet. För det andra ersattes PAA av en biobaserad cellulosanano-fibril (CNF), som ett mittlager mellan två lager av PVAm, vilket minskar kol-fotavtrycket och utvidgar möjligheten att använda LbL-teknik i antibakteriella tillämpningar, eftersom LbL-tekniken kan användas så länge som de alternativa skikten är motsatt laddade. Fibrerna modifierade med denna metod har visat liknande och ännu bättre antibakteriella egenskaper än hos PAA. Förutom att utveckla den antibakteriella metoden med hjälp av LbL på cellulosafibrer, är det också viktigt att förstå den antibakteriella mekanismen. Det visade sig att laddningstätheten och ytstrukturerna är två viktiga faktorer som påverkar bakteriell vidhäftning och den bakteriedödande effekten. För att studera detta gjordes olika laddade cellulosamodytor genom beläggning av oxiderad, regenererad cellulosa följt av PVAm / CNF / PVAm LbL-deposition och en bättre antibakteriell effekt observerades på den högre laddade ytan. Genom att beräkna kraften mellan bakterierna och laddad yta föreslogs att en högre interaktion på grund av den högre ytladdningen orsakar en stor påkänning på bakteriecellväggen vilket leder till störning av bakterierna. För att ytterligare förbättra den bakteriedödande effekten mönstrades de plana ytorna med mikro- och nanokonstruktioner med användning av en femtosekund laserteknik. Försvagningen av det bakteriella yttre membranet orsakat av den laddade ytan gör bakterierna mer sårbara och lättare att störa. Detta tillvägagångssätt har visat sig vara giltigt på både Gram-positiv S. aureus viii och gram-negativ E. coli. Effekten var större på E. coli med en svagare membranstruktur och högre ytpotential, vilket visar att den antibakteriella mekanismen är en fysisk störning av bakteriecellen.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2019. p. 75
Series
TRITA-CBH-FOU ; 2019: 70
Keywords
Layer-by-layer, antibacterial, cellulose materials
National Category
Polymer Technologies
Research subject
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-264035 (URN)978-91-7873-292-0 (ISBN)
Public defence
2019-12-13, Kollegiesalen, Brinellvagen 8, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 2019-11-22

Available from: 2019-11-22 Created: 2019-11-20 Last updated: 2019-11-22Bibliographically approved

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