The effects of surface architecture and physics on bacterial biofilm growth

Abstract

Bacteria are ubiquitous in the environment and can adhere onto abiotic or biotic surfaces to form biofilms. These three-dimensional (3D) communities of sessile cells are encased in a matrix of extracellular polymeric substances (EPS). Bacterial biofilms can be detrimental to human health, causing infections and diseases. Notably, bacterial biofilms are robust structures and are difficult to treat via traditional antibiotic therapy. The EPS matrix acts as a barrier to agents trying to access the interior of the biofilm, subsequently triggering the development of antibiotic resistance, which has been shown for both Staphylococcus epidermidis and Pseudomonas aeruginosa. Physical strategies, in particular the use of rationally surface design, have gained interests and present us with an effective approach to prevent bacterial adherence and biofilm growth without the requirement for antimicrobials. In this study, we aim to develop biomaterial surfaces via surface modifications that can control bacterial growth, as well as investigate the bacterial-material interactions on these surfaces. We firstly designed and fabricated nano-pillar structured surfaces via electron-beam lithography and polymer moulding technique. The results showed that rod-shaped Pseudomonas aeruginosa can align within the pillars if the space is comparable to the bacteria size; and the extended bacterial growth showed that fibrous network was formed and can help to connect isolated bacterial clusters within the pillars thereby aid in the continuous biofilm growth. Therefore, biomimetic hierarchical structured surfaces were fabricated based on the natural rose-petal via the same method of replicating nano-pillars. The key results showed that hierarchical structures are more effective in delaying biofilm growth of Staphylococcus epidermidis and Pseudomonas aeruginosa compared to the unitary structure. The nano-folds across the hemispherical micro-papillae restrict initial attachment of bacterial cells and delay the direct contacts of cells via cell alignment, and the hemispherical micro-papillae arrays isolate bacterial clusters and inhibit the formation of a fibrous network. Finally, we made two kinds of slippery surfaces via infusing the silicone oil. These slippery surfaces showed superior anti-wetting properties and exhibited excellent “self-cleaning” effects. Additionally, either slippery surface can prevent around 90% of bacterial biofilm growth of Staphylococcus epidermidis and Pseudomonas aeruginosa after 6 days, as compared with the unmodified control PDMS surfaces. This study detailed investigated the different bacterial responses when making contacts with artificial biomaterial surfaces. Multiply imaging techniques such as fluorescent microscopy, scanning electron microscopy and wettability analysis were adopted in this study, will instruct researchers to reveal the physic-chemical interactions of bacteria and materials. Particularly, the anti-biofilm surface design in this study will give insights to develop a more effective way for controlling robust biofilm growth, thereby paving a high way for preventing infection or fouling problems in either medical or industry contexts.